Abstract: Here we describe a fully automated approach for the synthesis of (68)Ga-labelled DOTA-peptides based on pre-concentration and purification of the generator eluate by using a cation exchange-cartridge and its comparison with fully automated direct labelling applying fractionated elution. Pre-concentration of the eluate on a cation exchange cartridge both using a resin-based and a disposable cation-exchange cartridge efficiently removed (68)Ge as well as major metal contaminations with Fe and Zn. This resulted in a high labelling efficiency of DOTA-peptides at high specific activity (SA) with short synthesis times.
Abstract: The diagnosis of invasive pulmonary aspergillosis (IPA) is difficult and lacks specificity and sensitivity. In the pathophysiology of Aspergillus fumigatus, iron plays an essential role as a nutrient during infection. A. fumigatus uses a specific and highly efficient iron uptake mechanism based on iron-complexing ferric ion Fe(III) siderophores, which are a requirement for A. fumigatus virulence. We aimed to evaluate the potential of siderophores radiolabeled with (68)Ga, a positron emitter with complexing properties comparable to those of Fe(III), as a radiopharmaceutical for imaging IPA. METHODS: (68)Ga radiolabeling of the A. fumigatus siderophores desferri-triacetylfusarinine C (TAFC) and desferri-ferricrocin (FC) was performed at high specific activity. Stability, protein binding, and log P values were determined. In vitro uptake in A. fumigatus cultures was tested under varying conditions. Biodistribution was studied in healthy noninfected BALB/c mice, and uptake was studied in a model of A. fumigatus infection using immunosuppressed Lewis rats. RESULTS: High-specific-activity (68)Ga labeling could be achieved, and resulting complexes were stable in serum, toward diethylenetriaminepentaacetic acid and Fe(III) challenge. Both siderophores showed hydrophilic properties ((68)Ga-TAFC, log P = -2.59; (68)Ga-FC, log P = -3.17) with low values of protein binding for (68)Ga-TAFC (<2%). Uptake of both siderophores was highly dependent on the mycelial iron load and could be blocked with an excess (10 microM) of siderophore or NaN(3), indicating specific, energy-dependent uptake. In noninfected mice, (68)Ga-TAFC showed rapid renal excretion and low blood values (1.6 +/- 0.37 percentage injected dose per gram [%ID/g] at 30 min); in urine only intact (68)Ga-TAFC was detected. In contrast, (68)Ga-FC revealed high retention in blood (16.1 +/- 1.07 %ID/g at 90 min) and rapid metabolism. In the rat IPA model, lung uptake of (68)Ga-TAFC was dependent on the severity of infection, with less than 0.04 %ID/g in control rats (n = 5) and 0.29 +/- 0.11 %ID/g in mildly infected (n = 3) and 0.95 +/- 0.37 %ID/g in severely infected (n = 4) rats. PET showed focal accumulation in infected lung tissue. CONCLUSION: Both siderophores bound (68)Ga with high affinity, and (68)Ga-TAFC, especially, showed high stability. (68)Ga-TAFC displayed highly selective accumulation by A. fumigatus subspecies in vitro and in vivo. The high and specific uptake by A. fumigatus proves the potential of (68)Ga-labeled siderophores for the specific detection of A. fumigatus during infection. They hold promise as new PET agents for IPA.
Abstract: A sophisticated coligand strategy is presented for peptide-derived radioconjugates based on (99m)Tc '4 + 1' mixed-ligand complexes. The new pharmacologically active coligands are assessed for (99m)Tc-labeling of the RGD-peptide cyclo(Arg-Gly-Asp-D-Tyr-Lys) which is an established vehicle to target alpha(v)beta(3) integrins playing a crucial part in tumor pathogenesis. Complexes of the general formula [(99m)Tc(NS(3)R)X] were synthesized and evaluated, in which Tc(III) is coordinated by NS(3)R, a derivative of the tetradentate chelator 2,2',2''-nitrilotriethanethiol (NS(3)), and by X, a monodentate binding isocyanide bearing the biomolecule. The novel tetradentate chelators (NS(3)R = NS(3)crown, NS(3)en, NS(3)(COOH)(3)) constitute NS(3) with a crown ether, an amine or a tricarboxylic acid as pharmacological modifiers. The isocyanides (X = L2-RGD, L2-Lys) contained the linker isocyanobutanoic acid (L2) coupled to N(6)-Lys of the RGD-peptide and additionally to a single Lys. The lipophilicity (distribution coefficient log D(O)(/W), pH = 7.4) of the RGD-containing radiotracers decreased in the order of the coligands NS(3)crown (-1.7 +/- 0.1), NS(3)en (-2.7 +/- 0.1) and NS(3)(COOH)(3) (-3.3 +/- 0.1). In the same order of the coligands, the biodistribution of the series [(99m)Tc(NS(3)R)(L2-RGD)] in normal rats showed a decrease of hepatobiliary and an increase of urinary excretion. The ratio of specifically to unspecifically uptaken activity (sum of surface bound and internalized activity) in alpha(v)beta(3) integrin-expressing M21 cells was in the range of approximately 4-5 and comparable for all [(99m)Tc(NS(3)R)(L2-RGD)] tracers. The biodistribution of [(99m)Tc(NS(3)en)(L2-RGD)] in nu/nu mice bearing M21 and M21L (control) tumor xenografts exhibited a specific tumor uptake with a low target-background ratio. The metabolic stability of the [(99m)Tc(NS(3)R)(L2-RGD)] tracers in normal rats was high, since 75-87% of the radioactivity in the plasma extract was assigned to the injected radiotracers 60 min after intravenous application in a rat. The hypothetical metabolites [(99m)Tc(NS(3)R)(L2-Lys)] were not found. These results demonstrate a considerable improvement of in vivo properties of (99m)Tc '4 + 1' peptide conjugates and open up the possibility of applying the labeling approach for further radiodiagnostic peptides.
Abstract: This guidance is meant as a guidance to Part B of the EANM "Guidelines on Good Radiopharmacy Practice (GRPP)" issued by the Radiopharmacy Committee of the EANM (see www.eanm.org ), covering the small-scale "in house" preparation of radiopharmaceuticals which are not kit procedures. The aim is to provide more detailed and practice-oriented guidance to those who are involved in the small-scale preparation of, for example, PET, therapeutic or other radiopharmaceuticals which are not intended for commercial purposes or distribution.
Abstract: Radiolabeling of nanoparticles (NPs) has been performed for a variety of reasons, such as for studying pharmacokinetics, for imaging, or for therapy. Here, we describe the in vitro and in vivo evaluation of DTPA-derivatized lipid-based NP (DTPA-NP) radiolabeled with different radiometals, including (111)In and (99m)Tc, for single-photon emission computed tomography (SPECT), (68)Ga for positron emission tomography (PET), and (177)Lu for therapeutic applications. PEGylated DTPA-NP with varying DTPA amounts, different composition, and size were radiolabeled with (111)In, (177)Lu, and (68)Ga, using various buffers. (99m)Tc-labeling was performed directly and by using the carbonyl aquaion, [(99m)Tc(H(2)O)(3)(CO)(3)](+). Stability was tested and biodistribution evaluated. High labeling yields (>90%) were achieved for all radionuclides and different liposomal formulations. Specific activities (SAs) were highest for (111)In (>4 MBq/mug liposome), followed by (68)Ga and (177)Lu; for (99m)Tc, high labeling yields and SA were only achieved by using [(99m)Tc(H(2)O)(3)(CO)(3)](+). Stability toward DTPA/histidine and in serum was high (>80 % RCP, 24 hours postpreparation).). Biodistribution in Lewis rats revealed no significant differences between NP in terms of DTPA loading and particle composition; however, different uptake patterns were found between the radionuclides used. We observed lower retention in blood (<3.3 %ID/g) and lower liver uptake (< 2.7 %ID/g) for (99m)Tc- and (68)Ga, compared to (111)In-NP (blood, <4 %ID/g; liver, <3.6 %ID/g). Imaging potential was shown by both PET magnetic resonance imaging fusion imaging and SPECT imaging. Overall, our study shows that PEGylated DTPA-NP are suitable for radiolabeling studies with a variety of radiometals, thereby achieving high SA suitable for targeting applications.
Abstract: Imaging techniques allowing non-invasive monitoring of tumour angiogenesis have attracted great interest over the last years. The integrin alpha(v)beta3 is overexpressed during tumour spread and metastasis and therefore is an attractive target for monitoring angiogenetic processes. This review summarizes attempts to develop radiolabelled peptides based on the Arg-Gly-Asp (RGD) sequence and related peptidomimetics with high affinity and selectivity for the alpha(v)beta3 integrin for tumour targeting. Most developments were based on cyclic RGD peptides radiolabelled with 18F, 64Cu, 68Ga for PET, 99mTc for SPECT or 177Lu for therapeutic applications. To enable fast elimination from non target tissue and rapid excretion of the radiolabelled peptides pharmacokinetic modifiers such as sugar amino acids have been evaluated. Out of these developments (18F)Galacto-RGD has shown high tumour-to-background ratios preclinically and has been evaluated in a number of clinical studies, showing the possibility for non invasive imaging of alpha(v)beta3 in tumour patients. To improve targeting efficiency multimeric constructs were reported revealing improved targeting properties in preclinical models. These developments still have to be transferred into the clinical setting.
Abstract: Two cyclized minigastrin analogues for gastrin receptor scintigraphy were synthesized and derivatized with HYNIC at the N-terminus for labeling with 99mTc. Radiolabeling efficiency, stability, cell internalization, and receptor binding on CCK-2 receptor expressing AR42J cells were studied and the biodistribution evaluated in tumor bearing nude mice, including NanoSPECT/CT imaging. Metabolites in urine, liver, and kidneys were analyzed by radio-HPLC. Radiolabeled cyclic MG showed high stability in vitro and receptor mediated uptake in AR42J cells. In the animal tumor model, fast renal clearance and low nonspecific uptake in most organs were observed. A tumor uptake >3% was calculated ex vivo 1 h p.i. for both 99mTc-EDDA-HYNIC-cyclo-MG1 and 99mTc-EDDA-HYNIC-cyclo-MG2. In an imaging study with 99mTc-EDDA-HYNIC-cyclo-MG1, the tumor was clearly visualized. The metabolite analysis indicated rapid enzymatic degradation in vivo.
Abstract: (68)Ga-labeled 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid-d-Phe(1)-Tyr(3)-octreotide (DOTA-TOC) PET has proven its usefulness in the diagnosis of patients with neuroendocrine tumors. Radionuclide therapy ((90)Y-DOTA-TOC or (177)Lu-DOTA-octreotate) is a choice of treatment that also requires an accurate diagnostic modality for early evaluation of treatment response. Our study compared (68)Ga-DOTA-TOC PET with CT or MRI using the Response Evaluation Criteria in Solid Tumors. Furthermore, standardized uptake values (SUVs) were calculated and compared with treatment outcome. METHODS: Forty-six patients (29 men, 17 women; age range, 34-84 y) with advanced neuroendocrine tumors were investigated before and after 2-7 cycles of radionuclide therapy. Long-acting somatostatin analogs were not applied for at least 6 wk preceding the follow-up. Data were acquired with a dedicated PET scanner. Emission image sets were acquired at 90-100 min after injection. (68)Ga-DOTA-TOC PET images were visually interpreted by 2 experienced nuclear medicine physicians. For comparison, multislice helical CT scans and 1.5-T MRI scans were obtained. Attenuation-corrected PET images were used to determine SUVs. Repeated CT evaluation and other imaging modalities, for example, (18)F-FDG, were used as the reference standard. RESULTS: According to the reference standard, (68)Ga-DOTA-TOC PET and CT showed a concordant result in 32 patients (70%). In the remaining 14 patients (30%), discrepancies were observed, with a final outcome of progressive disease in 9 patients and remission in 5 patients. (68)Ga-DOTA-TOC PET was correct in 10 patients (21.7%), including 5 patients with progressive disease. In these patients, metastatic spread was detected with the follow-up whole-body PET but was missed when concomitant CT was used. On the other hand, CT confirmed small pulmonary metastases not detected on (68)Ga-DOTA-TOC in 1 patient and progressive liver disease not detected on (68)Ga-DOTA-TOC in 3 patients. Quantitative SUV analysis of individual tumor lesions showed a large range of variability. CONCLUSION: (68)Ga-DOTA-TOC PET shows no advantage over conventional anatomic imaging for assessing response to therapy when all CT information obtained during follow-up is compared. Only the development of new metastases during therapy was detected earlier in some cases when whole-body PET was used. SUV analysis of individual lesions is of no additional value in predicting individual responses to therapy.
Abstract: Somatostatin receptor scintigraphy is an accurate imaging modality for the diagnosis of neuroendocrine tumor. Because detection of distant metastases has a major impact on treatment, early diagnosis of metastatic spread is of great importance. So far, no standard procedure has become established for the early diagnosis of bone metastases from neuroendocrine tumor. We compared the diagnostic value of CT with that of the novel somatostatin analog (68)Ga-1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid-d-Phe(1)-Tyr(3)-octreotide ((68)Ga-DOTATOC) in the detection of such metastases. METHODS: Fifty-one patients (22 women and 29 men; age range, 32-87 y) with histologically verified neuroendocrine tumor were included in this study. PET scans were fused with CT scans using a vacuum fixation device. (18)F-NaF or (99m)Tc-dicarboxypropane diphosphonate bone scans or clinical follow-up served as the reference standard. RESULTS: Twelve of the 51 patients had no evidence of bone metastases on any of the available imaging modalities, and 37 patients had (68)Ga-DOTATOC PET results true-positive for bone metastases. (68)Ga-DOTATOC PET results were true-negative for 12 patients, false-positive for one, and false-negative for another, resulting in a sensitivity of 97% and a specificity of 92%. (68)Ga-DOTATOC PET detected bone metastases at a significantly higher rate than did CT (P < 0.001). Furthermore, conventional bone scans confirmed the results of somatostatin receptor PET but did not reveal additional tumors in any patients. CONCLUSION: (68)Ga-DOTATOC PET is a reliable, novel method for the early detection of bone metastases in patients with neuroendocrine tumor. Our results show that CT and conventional bone scintigraphy are less accurate than (68)Ga-DOTATOC PET in the primary staging or restaging of neuroendocrine tumor.
Abstract: PURPOSE: alphavbeta3 integrins are important cell adhesion receptors involved in angiogenic processes. Recently, we demonstrated using [(18)F]Galacto-RGD that monitoring of alphavbeta3 expression is feasible. Here, we introduce (68)Ga- and (111)In-labelled derivatives and compare them with [(18)F]Galacto-RGD. METHODS: For radiolabelling, cyclo(RGDfK(DOTA)) was synthesised using SPPS. For in vitro characterisation determination of partition coefficients, protein binding, metabolic stability, alphavbeta3 affinity and cell uptake and for in vivo characterization, biodistribution studies and micro positron emission tomography (PET) imaging were carried out. For in vivo and in vitro studies, human melanoma M21 (alphavbeta3 positive) and M21-L (alphavbeta3 negative) cells were used. RESULTS: Both tracers can be synthesised straightforward. The compounds showed hydrophilic properties and high metabolic stability. Up to 23% protein-bound activity for [(68)Ga]DOTA-RGD and only up to 1.4% for [(111)In]DOTA-RGD was found. Cell uptake studies indicate receptor-specific accumulation. This is confirmed by the biodistribution data. One hour p.i. accumulation in alphavbeta3-positive tumours was 2.9 +/- 0.3%ID/g and in alphavbeta3-negative tumours 0.8 +/- 0.1%ID/g for [(68)Ga]DOTA-RGD ([(111)In]DOTA-RGD: 1.9 +/- 0.3%ID/g and 0.5 +/- 0.2%ID/g; [(18)F]Galacto-RGD: 1.6 +/- 0.2%ID/g and 0.4 +/- 0.1%ID/g). Thus, tumour uptake ratios were comparable. Due to approx. 3-fold higher blood pool activities for [(68)Ga]DOTA-RGD, tumour/blood ratios were higher for [(111)In]DOTA-RGD and [(18)F]Galacto-RGD. However, microPET studies demonstrated that visualisation of alphavbeta3-positive tumours using [(68)Ga]DOTA-RGD is possible. CONCLUSIONS: Our data indicate that [(68)Ga]DOTA-RGD allows monitoring of alphavbeta3 expression. Especially, the much easier radiosynthesis compared to [(18)F]Galacto-RGD would make it an attractive alternative. However, due to higher blood pool activity, [(18)F]Galacto-RGD remains superior for imaging alphavbeta3 expression. Introduction of alternative chelator systems may overcome the disadvantages.
Abstract: Somatostatin receptor scintigraphy has found considerable interest for imaging thyroid tumours. Recently, also therapeutic application of Somatostatin analogues labelled with beta-emitting radionuclides has been suggested as treatment option for thyroid tumours with absent radioiodine uptake. Most of the radiolabelled analogues available show a predominant affinity for Somatostatin receptor subtype 2. This study reports on the in vitro characterisation of Somatostatin receptor subtype mRNAs in thyroid tumours and normal thyroid tissue by means of RT-PCR. Surgical samples of 21 patients were collected, and mRNA of 16 tumour and 17 control specimen was isolated. mRNA expression for Somatostatin, SSTR subtype 1-5, thyroid markers (NIS, TSH, Tg, TPO) and control markers (GAPDH, beta-actin) was determined. PCR results were correlated with immunohistochemistry staining using SSTR2 receptor specific antibodies. 94% of all samples expressed Somatostatin receptor mRNA with predominant expression of subtype 2, less predominant of subtype 5 and subtype 3. Somatostatin receptor subtype 2 mRNA expression correlated well with immunohistochemical staining pattern in 13/16 samples, SSTR2 immunohistochemistry was positive in 87% of the samples. Our results show that Somatostatin receptor 2 is predominantly expressed on thyroid tissue and is a valid target for treatment of thyroid tumours. Octreotide derivatives currently used in Nuclear medicine seem to be well suited to target receptors expressed in thyroid tumours.
Abstract: AIM: The alfa(v)beta(3) integrin is involved in angiogenesis and tumor metastasis. Arginine-glycine-aspartic acid (RGD)-peptides bind with high affinity to this integrin. This study compares the influence of (99m)Tc-labeling applying novel Technetium-cores on imaging characteristics of the radiolabeled peptide. METHODS: Different peptide conjugates based on the cyclic pentapeptide c(RGDyK) (cRGD) were prepared and characterized (HYNIC-, Cys-, L2- and Pz1-cRGD). Radiolabeling experiments using different coligands for HYNIC-cRGD, the (99m)Tc(CO)(3) metal fragment for PZ-1-cRGD (pyrazolyl-derivative), the Tc-nitrido-core using a phosphine-coligand (PNP) for Cys-cRGD and an isonitrile-conjugate (L2-cRGD) together with a NS(3)-coligand (4+1 concept) were performed and showed labeling yields >90% at high specific activities. RESULTS: A high in vitro stability was observed, plasma protein binding and lipophilicity varied considerably between different radiolabeled cRGD conjugates. Experiments on biological activity of the radiolabeled peptides using alfa(v)beta(3) positive (M21) and negative (M21L) tumor cells did show specific uptake of various conjugates. Studies in tumor bearing animals revealed significant differences between different conjugates concerning pharmacokinetic behavior (predominant renal excretion to considerable hepatobiliary clearance) as well as tumor uptake (0.2-2.7%ID/g). Highest specific tumor uptake and tumor/background values were found for [(99m)Tc]EDDA/HYNIC-c(RGDyK), [(99m)Tc]Nitrido-PNP-Cys-c(RGDyK) and [(99m)Tc(CO)(3)]-Pz1-c(RGDyK). CONCLUSIONS: Using novel Tc-cores such as the (99m)Tc(CO)(3) metal fragment, Tc-nitrido- and the 4+1 concept peptides could be labeled with [(99m)Tc]technetium at high specific activities resulting in complexes with high stability, but binding moieties have to be optimized especially concerning hydrophilicity resulting in renal rather than hepatobiliary excretion. This comparative study underlines that peptide labeling strategies using (99m)Tc have to be properly selected and optimized. Different in vitro assays are necessary to predict targeting properties in vivo.
Abstract: BACKGROUND: Generator-produced Ga has attracted increasing interest for radiolabelling peptides used in PET applications. So far, the synthesis of Ga-peptide radiopharmaceuticals is mainly based on semi-automated systems. Here we describe a fully automated approach for the synthesis of Ga-labelled peptides. METHOD: A commercially available Ga generator was eluted with 0.1 mol . l HCl. Reaction parameters such as buffer conditions, pH range, reaction temperature and time, volume of reaction solution and generator fraction were optimized for labelling DOTA-Tyr-octreotide (DOTATOC). Reaction yields, pH, radiochemical purity, sterility, endotoxins, breakthrough of Ge and final Ge content were determined. A fully automated radiopharmaceutical synthesis device based on a modular concept for remote-controlled processing was developed and evaluated for a number of DOTA-derivatized peptides. RESULTS: DOTATOC could be labelled in almost quantitative yields by heating 10-50 nmol peptide at pH 3.5-4.0 for 5 min at 95 degrees C in 1.5 ml. Purification using a reversed-phase cartridge was required to avoid any potential Ge breakthrough: final activities of Ge were below 100 Bq . ml. Automated synthesis resulted in overall decay-corrected reaction yields of about 60% within 10 min. Even after 1 year using a 1110 MBq generator more than 130 MBq Ga-DOTATOC could be obtained. Moreover, it was demonstrated that a variety of DOTA-derivatized peptides can be labelled using identical reaction conditions with high yields. CONCLUSION: The system described allows the fully automated, efficient and rapid preparation of Ga-DOTA-derivatized peptides. It has been used successfully and reliably for routine preparations in clinical studies.
Abstract: The aim of this study was to evaluate the diagnostic value of a new somatostatin analog, (68)Ga-labeled 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid-d-Phe(1)-Tyr(3)-octreotide ((68)Ga-DOTA-TOC), for PET in patients with known or suspected neuroendocrine tumors. PET was compared with conventional scintigraphy and dedicated CT. METHODS: Eighty-four patients (48 men, 36 women; age range, 28-79 y; mean age +/- SD, 58.2 +/- 12.2 y) were prospectively studied. For analysis, patients were divided into 3 groups: detection of unknown primary tumor in the presence of clinical or biochemical suspicion of neuroendocrine malignancy (n = 13 patients), initial tumor staging (n = 36 patients), and follow-up after therapy (n = 35 patients). Each patient received 100-150 MBq (68)Ga-DOTA-TOC. Imaging results of PET were compared with (99m)Tc-labeled hydrazinonicotinyl-Tyr(3)-octreotide ((99m)Tc-HYNIC-TOC) and (111)In-DOTA-TOC. CT was also performed on every patient using a multidetector scanner. Each imaging modality was interpreted separately by observers who were unaware of imaging findings before comparison with PET. The gold standard for defining true-positive (TP), true-negative (TN), false-positive (FP), and false-negative (FN) results was based on all available histologic, imaging, and follow-up findings. RESULTS: PET was TP in 69 patients, TN in 12 patients, FP in 1 patient, and FN in 2 patients, indicating a sensitivity of 97%, a specificity of 92%, and an accuracy of 96%. The FP finding was caused by enhanced tracer accumulation in the pancreatic head, and the FN results were obtained in patients with a tumor of the gastrointestinal tract displaying liver metastases. (68)Ga-DOTA-TOC showed higher diagnostic efficacy compared with SPECT (TP in 37 patients, TN in 12 patients, FP in 1 patient, and FN in 34 patients) and diagnostic CT (TP in 41 patients, TN in 12 patients, FP in 5 patients, and FN in 26 patients). This difference was of statistical significance (P < 0.001). However, the combined use of PET and CT showed the highest overall accuracy. CONCLUSION: (68)Ga-DOTA-TOC PET shows a significantly higher detection rate compared with conventional somatostatin receptor scintigraphy and diagnostic CT with clinical impact in a considerable number of patients.
Abstract: PURPOSE: Different attempts have been made to develop a suitable radioligand for targeting CCK-2 receptors in vivo, for staging of medullary thyroid carcinoma (MTC) and other receptor-expressing tumours. After initial successful clinical studies with [DTPA(0),D: Glu(1)]minigastrin (DTPA-MG0) radiolabelled with (111)In and (90)Y, our group developed a (99m)Tc-labelled radioligand, based on HYNIC-MG0. A major drawback observed with these derivatives is their high uptake by the kidneys. In this study we describe the preclinical evaluation of the optimised shortened peptide analogue, [HYNIC(0),D: Glu(1),desGlu(2-6)]minigastrin (HYNIC-MG11). METHODS: (99m)Tc labelling of HYNIC-MG11 was performed using tricine and EDDA as coligands. Stability experiments were carried out by reversed phase HPLC analysis in PBS, PBS/cysteine and plasma as well as rat liver and kidney homogenates. Receptor binding and cell uptake experiments were performed using AR4-2J rat pancreatic tumour cells. Animal biodistribution was studied in AR4-2J tumour-bearing nude mice. RESULTS: Radiolabelling was performed at high specific activities and radiochemical purity was >90%. (99m)Tc-EDDA-HYNIC-MG11 showed high affinity for the CCK-2 receptor and cell internalisation comparable to that of (99m)Tc-EDDA-HYNIC-MG0. Despite high stability in solution, a low metabolic stability in rat tissue homogenates was found. In a nude mouse tumour model, very low unspecific retention in most organs, rapid renal excretion with reduced renal retention and high tumour uptake were observed. CONCLUSION: (99m)Tc-EDDA-HYNIC-MG11 shows advantages over (99m)Tc-EDDA-HYNIC-MG0 in terms of lower kidney retention with unchanged uptake in tumours and CCK-2 receptor-positive tissue. However, the lower metabolic stability and impurities formed in the labelling process still leave room for further improvement.
Abstract: Radiolabeled peptides containing the Arg-Gly-Asp amino acid sequence (single letter code = RGD) have been studied extensively to target integrin receptors upregulated on tumor cells and neovasculature. Integrins are cell surface transmembrane glycoproteins that exist as alphabeta heterodimers. The alphavbeta3 integrin is known to be overexpressed in many tumor types and is expressed at lower levels in normal tissues. Furthermore, alphavbeta3 and alphavbeta5 subtypes are expressed in neovasculature during angiogenesis. Thus, there is some impetus to image angiogenesis and tumor formation in vivo using RGD-based peptide targeting vectors. In this study, we report the design and development of a new cyclic RGD analogue cyclo-[Arg-Gly-Asp-d-Tyr-Lys(PZ)] (PZ = 3,5-Me2-pz(CH2)2N((CH2)3COOH)(CH2)2NH2) that can be radiolabeled with the [99mTc(CO)3(H2O)3]+ metal aquaion. Radiochemical evaluation of this new conjugate in vitro indicated a facile radiosynthesis of the new 99mTc-RGD conjugate with high radiolabeling yields (>or=95%) and high specific activities. In vitro internalization and blocking assays in alphavbeta3 receptor-positive, human M21 melanoma cancer cells showed the ability of this conjugate to target the integrin receptor with high specificity and selectivity. In vivo pharmacokinetic studies in normal CF-1 mice showed rapid clearance from blood with excretion primarily via/through the renal-urinary system. In vivo accumulation of radioactivity in mice bearing either alphavbeta3 receptor-positive or negative human melanoma tumors showed receptor specific uptake of tracer with accumulations of 2.50 +/- 0.29 and 0.71 +/- 0.08% ID/g in alphavbeta3 integrin positive (M21) and negative (M21L) tumors at 1 h postinjection (p.i.), respectively.
Abstract: [99mTc-EDDA-HYNIC-D-Phe1,Tyr3]-octreotide (99mTc-EDDA-HYNIC-TOC) is an alternative radioligand for somatostatin receptor (SSTR) scintigraphy of neuroendocrine tumours. In order to allow a rapid and accurate determination of the quality in the clinical routine the aim of this study was to evaluate different methods of radiochemical purity (RCP) testing. Three different methods of RCP testing were compared: high-performance liquid chromatography (HPLC), thin layer chromatography (TLC) and minicolumn (Sep-Pak purification = SPE). HPLC was shown to be the most effective method for the quality control. The use of TLC and SPE is only recommended after sufficient practical labelling experience.
Abstract: There has been increasing interest in peptides containing the Arg-Gly-Asp (RGD) sequence for targeting of alpha(v)beta(3) integrins to image angiogenesis. [(18)F]Galacto-RGD has been successfully used for positron emission tomography applications in patients. Here we report on the preclinical characterization of a (99m)Tc-labeled derivative for single-photon emission computed tomography. c(RGDyK) was derivatized with HYNIC at the amino group of the lysine [c(RGDyK(HYNIC)) or HYNIC-RGD]. (99m)Tc labeling was performed using coligands (tricine and EDDA), as well as (99m)Tc(CO)(3)(H(2)O)(3). Radiolabeled peptides were characterized with regard to lipophilicity, protein binding and stability in buffer, serum and tissue homogenates. Integrin receptor activity was determined in internalization assays using alpha(v)beta(3)-receptor-positive M21 and alpha(v)beta(3)-receptor-negative M21L melanoma cells. Biodistribution was evaluated in normal and nude mice bearing M21, M21L and small cell lung tumors. HYNIC-RGD could be labeled at high specific activities using tricine, tricine-trisodium triphenylphosphine 3,3',3''-trisulfonate (TPPTS), tricine-nicotinic acid (NA) or EDDA as coligands. [(99m)Tc]EDDA/HYNIC-RGD, [(99m)Tc]tricine-TPPTS/HYNIC-RGD and [(99m)Tc]tricine-NA/HYNIC-RGD showed protein binding (<5%) considerably lower than [(99m)Tc](CO)(3)/HYNIC-RGD and [(99m)Tc]tricine/HYNIC-RGD. [(99m)Tc]EDDA/HYNIC-RGD revealed high in vitro stability accompanied by low lipophilicity with a log P value of -3.56, comparable to that of [(18)F]Galacto-RGD. In M21 cells for this compound, the highest level of specific and rapid cell uptake (1.25% mg protein(-1)) was determined. In vivo, rapid renal excretion, low blood retention, low liver and muscle uptakes and low intestinal excretion 4 h postinjection were observed. Tumor uptake values were 2.73% ID/g in M21 alpha(v)beta(3)-receptor-positive tumors versus 0.85% ID/g in receptor-negative tumors 1 h postinjection. Small cell lung tumors could be visualized using gamma camera imaging. [(99m)Tc]EDDA/HYNIC-RGD shows encouraging properties to target alpha(v)beta(3) receptors in vivo with high stability and favorable pharmacokinetics. Tumor uptake studies showed specific targeting of alpha(v)beta(3)-receptor-positive tumors with tumor-to-organ ratios comparable to those of [(18)F]Galacto-RGD.
Abstract: BACKGROUND: Small animal imaging has recently been the subject of increasing interest and specific imaging devices in particular for positron emission tomography (PET) have been developed. To bypass limitations arising from high acquisition costs and dependence on an in-house cyclotron unit inevitably associated with PET, a conventional gamma camera has been equipped with a pinhole collimator and used to visualize striatal pre- and post-synaptic dopaminergic function in rats measured by the dopamine transporter ligand [123I]beta-CIT and the dopamine D2/dopamine D3 receptor ligand [123I]IBZM. In order to precisely estimate brain regions of low radioligand uptake, single photon emission computed tomography (SPECT) images were coregistered onto an MRI template. MATERIAL AND METHODS: Our pinhole SPECT/MRI approach has been employed in animal models of pre- and postsynaptic dopaminergic dysfunction. The physical characteristics of the scanner, the tracer kinetics and modelling as well as image postprocessing have been addressed and associated intrinsic problems and constraints discussed. CONCLUSIONS: An outlook has been provided on the application of pinhole SPECT and MRI coregistration towards non-invasive investigations of drug-receptor interactions and binding characteristics of newly developed radiopharmaceuticals.
Abstract: Single photon emission computed tomography (SPECT) and MRI coregistration have been assessed to characterize striatal dopamine D2/D3 receptor (D2/D3R) availability in rats following injection of the D2 and D3R radioligand [123I] iodobenzamide ([123I]IBZM). High-resolution SPECT data were obtained with a pinhole collimator. In order to precisely estimate brain regions of low radioligand uptake, SPECT images were coregistered onto a MRI template with high accuracy (maximum mismatch 1.1 mm). To evaluate an adequate dose of radioligand to be administered without exceeding the radioligand-to-receptor occupancy >5% and to define an appropriate time period for image acquisition, three untreated groups of animals received 29.6, 37, and 44.4 MBq of [123I]IBZM and underwent five consecutive SPECT acquisitions lasting 64 min each. Ratio calculations between specific striatal radioligand uptake and nondisplaceable cerebellar uptake revealed a secular equilibrium between 75 and 355 min post-tracer application in all three animal groups. Consequently, since the highest regional uptake values were obtained in the animal group receiving 44.4 MBq [123I]IBZM, this injection dose was considered to be appropriate. Finally, the capacity of the imaging method to detect distinct severity levels of striatal dopamine D2/D3 receptor loss was tested in a low, medium, and high dose quinolinic acid (QA) animal model of Huntington's disease. Motor impairment indicative of striatal dysfunction was monitored using amphetamine-induced rotational behavior and locomotor activity. Loss of striatal D2/D3R bearing medium-sized spiny neurons was assessed by DARPP-32 immunohistochemistry and compared to [123I]IBZM binding. Optical density measures of DARPP-32 immunohistochemistry demonstrated QA dose-dependent mild to subtotal unilateral striatal lesions ranging from 29.4% to 96.9% when compared to the nonlesioned side. Linear regression analysis showed that measurements of striatal DARPP-32 optical density and striatal [123I]IBZM uptake of the lesioned side were highly correlated (r2=0.83; P<0.001) whereas correlation with locomotor activity was less tight (r2=0.23; P<0.05; amphetamine-induced rotational behavior was not significantly correlated). This is the first study to demonstrate that in vivo [123I]IBZM SPECT and MRI coregistration are highly sensitive and, in contrast to behavioral measures, accurately detect mild to subtotal striatal lesions by measuring loss of D2/D3R availability. SPECT-MRI-based estimation of regional [123I]IBZM uptake provides a cost effective and widely available in vivo imaging technique for assessing striatal integrity in animal studies.
Abstract: AIM: To evaluate the use of 99mTc-EDDA-hydrazinonicotinyl-Tyr3-octreotide (Tc-TOC) for staging and follow-up of neuroendocrine gastro-entero-pancreatic (GEP) tumors with special focus on the acquisition protocol including single photon emission computed tomography (SPECT). METHODS: Eighty-eight patients (37 female, 51 male; age range: 16 to 81 years; mean age: 56.3 years) were studied: 42 patients for staging after initial histological confirmation and 46 patients during post-therapy follow-up. An average activity of 400 MBq of the radiopharmaceutical was injected. All tumors originated from neuroendocrine tissue of the gastroenteropancreatic tract. Whole body scintigrams at 4 h postinjection and SPECT of the abdomen were obtained in all patients. Additional planar images of the abdomen were acquired at 2 h after injection in 68 patients. RESULTS: The Tc-TOC scan result was true-positive in 56 patients, true-negative in 17, false-negative in 14, and false-positive in 1 patient. The false-positive finding was caused by a colonic adenoma. Overall, a scan sensitivity of 80% (56/70 patients), specificity of 94.4% (17/18 patients) and accuracy of 82.9% (73/88 patients) were calculated on patient basis. In total, Tc-TOC detected 357 foci in 69 patients. In 7 patients equivocal findings were observed in the bowel at 4 h postinjection without corresponding tracer uptake in the scan 2 h earlier, meaning that these abnormal findings were correctly classified as non-malignant. In addition to planar views, SPECT revealed further 62 lesions. CONCLUSIONS: Tc-TOC with one-day, dual-time acquisition protocol is an accurate staging procedure in patients with neuroendocrine GEP tumors. SPECT shows high sensitivity for detection of abdominal lesions, while earlier images improve the reliability of abnormal abdominal findings.
Abstract: PURPOSE: The aim of this study was to assess the value of multimodality imaging using a novel repositioning device with external markers for fusion of single-photon emission computed tomography (SPECT) and computed tomography (CT) images. The additional benefit derived from this methodological approach was analysed in comparison with SPECT and diagnostic CT alone in terms of detection rate, reliability and anatomical assignment of abnormal findings with SPECT. METHODS: Fifty-three patients (30 males, 23 females) with known or suspected endocrine tumours were studied. Clinical indications for somatostatin receptor (SSTR) scintigraphy (SPECT/CT image fusion) included staging of newly diagnosed tumours (n=14) and detection of unknown primary tumour in the presence of clinical and/or biochemical suspicion of neuroendocrine malignancy (n=20). Follow-up studies after therapy were performed in 19 patients. A mean activity of 400 MBq of (99m)Tc-EDDA/HYNIC-Tyr(3)-octreotide was given intravenously. SPECT using a dual-detector scintillation camera and diagnostic multi-detector CT were sequentially performed. To ensure reproducible positioning, patients were fixed in an individualised vacuum mattress with modality-specific external markers for co-registration. SPECT and CT data were initially interpreted separately and the fused images were interpreted jointly in consensus by nuclear medicine and diagnostic radiology physicians. RESULTS: SPECT was true-positive (TP) in 18 patients, true-negative (TN) in 16, false-negative (FN) in ten and false-positive (FP) in nine; CT was TP in 18 patients, TN in 21, FP in ten and FN in four. With image fusion (SPECT and CT), the scan result was TP in 27 patients (50.9%), TN in 25 patients (47.2%) and FN in one patient, this FN result being caused by multiple small liver metastases; sensitivity was 95% and specificity, 100%. The difference between SPECT and SPECT/CT was statistically as significant as the difference between CT and SPECT/CT image fusion (P<0.001). Twenty-seven abnormal SPECT findings in 17 patients could not be initially assigned to organs, but were clearly delineated after image fusion. In 21 patients (40%), clinically relevant information was obtained by image fusion as compared with SPECT alone. CONCLUSION: Co-registration of SPECT and diagnostic CT using a cost-effective immobilisation device provides excellent accuracy for tumour detection of endocrine malignancies and is superior to SPECT and CT alone. Image fusion reduces false positive results and can detect additional lesions. Anatomical information provided by CT enables precise localisation of abnormalities observed in SPECT.
Abstract: Over the last decade somatostatin receptor scintigraphy using various derivatives of long-acting somatostatin analogues has gained its place in the management of pancreatic islet-cell tumours. Scintigraphy is based on the high-affinity binding of such somatostatin analogues to receptors over-expressed by these tumour types. Following the introduction of (111)In-DTPA-D-Phe(1)-octreotide, clinical studies with radiolabelled DOTA-Tyr(3)-octreotide and DOTA-Tyr(3)-octreotate derivatives have shown considerable improvement of imaging results with increased tumour uptake. One of the newer developments, (68)Ga-labelled DOTA-Tyr(3)-octreotide, has shown promising results in patients with pancreatic islet-cell tumours, based on the high-affinity binding to the somatostatin receptor subtype 2 in combination with positron emission tomography (PET) technology. Other peptides--such as ligands for the gastrin/CCK2 receptors or vasoactive intestinal peptide (VIP)--have also been studied for imaging pancreatic cell tumours. Whereas small-sized gastrinoma, somatostatinoma, glucagonoma, carcinoid and VIPoma are frequently detected by somatostatin receptor scintigraphy, insulinoma may escape detection due to reduced receptor expression. Following peptide receptor scintigraphy, a change in patient management is reported in up to 30% of patients. When labelled with (90)Y or (177)Lu, some somatostatin analogues have been applied to patients in advanced stages of the disease. Despite positive response data in 50% of patients, long-term results and survival rates are lacking.
Abstract: [(99m)Tc-EDDA-HYNIC-D-Phe(1),Tyr(3)]-Octreotide ((99m)Tc-EDDA/HYNIC-TOC) is a promising new radiopharmaceutical with the potential to replace [(111)In-DTPA-D-Phe(1)]-Octreotide ((111)In-DTPA-OCT) as the radiopharmaceutical for somatostatin receptor scintigraphy due to the advantage of improved image quality, lower radiation dose for the patient, and daily availability. Here we describe the development of a freeze-dried kit formulation based on the Tricine/EDDA exchange labeling approach for the preparation of this radiopharmaceutical in a clinical setting. Three parameters were of major importance to achieve a suitable formulation with a radiochemical purity (RCP) >90%: addition of bulking agent, the pH of the freeze-drying solution, and the content of stannous chloride. The final formulation consisted of 20 mg Tricine, 10 mg EDDA, 50 mg Mannitol, 20 microg SnCl(2). 2H(2)O, and 20 microg [HYNIC-D-Phe(1), Tyr(3)]-Octreotide (HYNIC-TOC). Radiolabeling was performed by addition of 0.2 M Na(2)HPO(4) to adjust the pH to 6-7, followed by 0.5-2 GBq (99m)Tc sodium pertechnetate, in a total volume of 2 mL and incubation for 10 min in a boiling water bath. Mean RCP values of 10 batches showed values >90% over a storage period of up to 1 year, a high stability up to 24 h of the final preparation, and retained biological activity. The developed kit formulation forms the basis for further clinical evaluation of this promising new radiopharmaceutical.
Abstract: Gastrin/CCK-2 receptors are overexpressed in a number of tumors such as medullary thyroid cancer (MTC) and small cell lung cancer (SCLC). Recently [D-Glu1]-minigastrin (MG) has been radiolabeled with 131I, 111In, and 90Y and evaluated in patients. This study describes the labeling and evaluation of MG with technetium-99m using two different labeling approaches: HYNIC as bifunctional coupling agent and (Nalpha-His)Ac as tridentate ligand for 99mTc(CO3) labeling. Labeling was perfomed at high specific activities using Tricine and EDDA as coligands for HYNIC-MG and [99mTc(OH2)3(CO)3]+ for (Nalpha-His)Ac-MG. Stability experiments were carried out by reversed phase HPLC analysis in PBS, serum, histidine, and cysteine solutions, as well as rat liver and kidney homogenates. Receptor binding and internalization experiments were performed using CCK-2 receptor positive AR42J rat pancreatic tumor cells. Biodistribution experiments were carried out in nude mice carrying AR42J tumors by injection of 99mTc-labeled peptide with or without coinjection of 50 microg of minigastrin I human (MGh). HYNIC-MG and (Nalpha-His)Ac-MG could be radiolabeled at high specific activities (>1 Ci/micromol). For HYNIC-MG, high labeling yields (>95%) were achieved using Tricine and EDDA as coligands. Stability experiments of all 99mTc-labeled conjugates revealed a high stability of the label in PBS and serum as well as toward challenge with histidine and cysteine. Incubation in kidney homogenates resulted in a rapid degradation of all conjugates with <10% intact peptide after 60 min at 37 degrees C, with no considerable differences between the radiolabeled conjugates; a somewhat lower degradation rate was seen in liver homogenates. Protein binding varied considerably with lowest levels for 99mTc-EDDA/HYNIC-MG. Competition experiments of unlabeled conjugates on AR42J membranes versus [125I-Tyr12]-gastrin I showed high CCK-2 receptor affinity for all conjugates under study. Internalization behavior was very rapid for all radiolabeled conjugates in the order of 99mTc-(Nalpha-His)Ac-MG > 99mTc-EDDA/HYNIC-MG > 99mTc-Tricine/HYNIC-MG. In tumor-bearing nude mice the highest tumor-uptake was observed with 99mTc-EDDA/HYNIC-MG (8.1%ID/g) followed by 99mTc-Tricine/HYNIC-MG (2.2%ID/g) and 99mTc-(Nalpha-His)Ac-MG (1.2%ID/g) which correlated with kidney uptake (101.0%ID/g, 53.8%ID/g, 1.8%ID/g respectively). In this series of compounds 99mTc-EDDA/HYNIC-MG with its very high tumor/organ ratios except for kidneys seems to be the most promising agent to target CCK-2 receptors. Despite promising properties concerning receptor binding, internalization, and in vitro stability, 99mTc-(Nalpha-His)Ac-MG showed low tumor uptake in vivo.
Abstract: Tetraamine-[Tyr3]octreotate (Demotate) is a somatostatin (SST) analogue that can be easily labeled with 99mTc at high specific activities and showed promising preclinical properties for SST receptor scintigraphy. This study reports on the first intra-patient comparison of 99mTc-Demotate and another 99mTc-labeled SST analogue, 99mTc-EDDA/HYNIC-TOC (HYNIC-TOC). Five patients with carcinoid tumors (n = 2) and endocrine pancreatic tumors (n = 3) were investigated with both radiopharmaceuticals. 99mTc-Demotate rapidly visualized somatostatin receptor positive tumors as early as 15 minutes post-injection (p.i.) with maximum tumor uptake and tumor/organ ratios already 1 hour p.i. Organs of predominant physiological uptake were the spleen and the kidneys with no intestinal excretion detectable up to 24 hours. 99mTc-Demotate exhibited faster pharmacokinetic properties compared to HYNIC-TOC. Tumor/organ ratios at equivalent time points were higher or comparable for 99mTc-Demotate in three patients with a matching scan result. Equivocal findings were observed in two patients, i.e. comparable uptake behavior in larger lesions with differences in smaller ones. 99mTc-Demotate is a promising agent for somatostatin receptor scintigraphy providing images of excellent quality as early as 1 hour after injection.
Abstract: The aim of this study was to compare renal handling and distribution of (99m)Tc-octreotide and (99m)Tc-EDDA/HYNIC-Tyr(3)-octreotide (HYNIC-TOC) in rats. In kidney perfusion experiments, the renal clearance value of (99m)Tc-octreotide was three times lower than that of (99m)Tc-EDDA/HYNIC-TOC. The predominant renal excretion of (99m)Tc-EDDA/HYNIC-TOC was associated with a high and long-term renal accumulation up to 48 hrs. Microautoradiographic results indicated that (99m)Tc-EDDA/HYNIC-TOC was retained mainly in the renal medulla within the cells of the collecting ducts and in the surrounding tissue. Lower positivity was found in the proximal and distal tubular cells. We conclude that the mechanism of renal accumulation of somatostatin analogues renal accumulation is complex and that proximal tubular reabsorption is probably not the main mechanism for uptake of (99m)Tc-EDDA/HYNIC-TOC in the kidneys. The presence of the somatostatin receptors, differences in the tonicity level within kidneys and other possible mechanisms could participate in their renal accumulation.
Abstract: Several studies have reported on the expression of somatostatin receptors in patients with differentiated thyroid cancer (DTC). The aim of this study was to evaluate the imaging abilities of a recently developed technetium-99m labelled somatostatin analogue, (99m)Tc-EDDA/HYNIC-TOC ((99m)Tc-TOC), in terms of precise localisation of disease. The study population comprised 54 patients (24 men, 30 women; age range 22-90 years) with histologically confirmed DTC who presented with recurrent or persistent disease as indicated by elevated Tg levels after initial treatment. All patients were negative on the iodine-131 post-therapy whole-body scans. Fluorine-18 fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) was performed in a subgroup of 36 patients. The study population consisted of two groups: Group A ( n=22) comprised patients with disease recurrence as shown by elevated Tg levels but without detectable pathology. In group B ( n=32), pre-existing lesions were known. Among the 54 cases, SSTR scintigraphy was true positive in 33 (61.1%), true negative in 4 (7.4%) and false negative in 17 (31.5%) cases, which resulted in a sensitivity of 66%. A total of 138 tumour foci were localised in 33 patients. The fraction of true positive (99m)Tc-TOC findings was positively correlated ( P<0.01) with elevated Tg levels (higher than 30 ng/ml). Despite two false positive findings, analysis on a lesion basis demonstrated better diagnostic efficacy with (18)F-FDG PET ( P<0.001); however, it also revealed substantial agreement between the imaging techniques [Cohen's kappa of 0.62 (0.47-0.78)]. In conclusion, scintigraphy with (99m)Tc-TOC might be a promising tool for treatment planning; it is easy to perform and showed sufficient accuracy for localisation diagnostics in thyroid cancer patients with recurrent or metastatic disease.
Abstract: Somatostatin receptor (SSTR) scintigraphy with indium-111 DTPA-octreotide has become a routine diagnostic procedure in oncology. However, it suffers some drawbacks concerning the limited availability, suboptimal imaging properties and elevated radiation burden of (111)In. We have recently been involved in the development of a new tetraamine-functionalised [Tyr(3)]octreotate derivative (Demotate 1) that can be easily labelled with technetium-99m at high specific activities. (99m)Tc-Demotate 1 showed promising properties in preclinical studies. In this study we report on the first experience with (99m)Tc-Demotate 1 in patients. Six patients (mean age 56 years) with carcinoid tumours ( n=2) or endocrine pancreatic tumours ( n=4) with previously positive SSTR scintigraphy were enrolled in the study. Patients were injected with 500-600 MBq (99m)Tc-Demotate 1. Clinical and laboratory parameters were controlled up to 3 months p.i. Blood samples were taken at various time points up to 24 h p.i., and urine was collected up to 24 h. Whole-body images were acquired at 15-30 min, 1-2 h, 4 h and 24 h p.i. with additional single-photon emission tomography imaging at 1-4 h. Blood excretion was very rapid, with <2%ID in plasma after 1 h, and urinary excretion <20% ID after 6 h. Two patients complained of mild gastrointestinal problems and paraesthesia, but no other adverse reactions were observed. SSTR-positive tumours were rapidly visualised as early as 15 min p.i., with maximum tumour uptake (up to 19% ID) and tumour/organ ratios as early as 1 h p.i. Organs of predominant physiological uptake were the spleen and the kidneys, with no intestinal excretion detectable up to 24 h. (99m)Tc-Demotate 1 detected 11 lesions while In-Oct detected ten; differences in uptake behaviour were observed in three patients. This study shows for the first time that peptides derivatised with a tetraamine ligand for labelling with (99m)Tc show suitable properties for receptor imaging in patients. (99m)Tc-Demotate 1 is a promising agent for the visualisation of SSTR-positive lesions in patients, allowing rapid imaging as early as 1 h p.i.; some differences are observed in pharmacokinetic behaviour compared with (111)In-DTPA-octreotide.
Abstract: The aim of this study was to compare the imaging abilities of the recently developed somatostatin analog, (99m)Tc-hydrazinonicotinyl-Tyr(3)-octreotide ((99m)Tc-HYNIC-TOC [(99m)Tc-TOC]), with (111)In-diethylenediaminepentaacetic acid-D-Phe(1)-octreotide ((111)In-OCT [Octreoscan]) in patients undergoing routine somatostatin receptor (SSTR) scintigraphy. METHODS: Forty-one patients (20 men, 21 women; age range, 29-75 y; mean age, 56.7 y) with either histologically proven or biologically and clinically suspected endocrine tumors were enrolled in the study. Four groups were distinguished: (a) patients being evaluated for the detection and localization of neuroendocrine tumors (n = 6), (b) tumor staging (n = 19), (c) patients being investigated to determine the SSTR status of tumor lesions (n = 11), and (d) patient follow-up studies (n = 5). Each patient received a mean activity of 150 MBq (111)In-OCT and 350-400 MBq (99m)Tc-TOC. Scintigraphy with (99m)Tc-TOC was performed 4 h after injection and scintigraphy with (111)In-OCT was performed 4 and 24 h after injection. SPECT studies of areas of interest were performed 4 h after injection for both tracers as well as at 24 h after injection for (111)In-OCT. The time interval between the studies using each tracer ranged from 2 to 22 d (mean interval, 9.3 d). RESULTS: (111)In-OCT and (99m)Tc-TOC showed an equivalent scan result in 32 patients (78%), 9 cases showed discrepancies (22%), false-negative results with (111)In-OCT were seen in 6 cases (14.6%), whereas (99m)Tc-TOC was false-positive in 2 cases (4.9%). (111)In-OCT was true-negative in both cases. The false-positive findings of the (99m)Tc-TOC studies were caused by nonspecific uptake in the bowel. In 1 case, (99m)Tc-TOC correctly identified a metastasis in the lumbar spine but both scan results were false-positive because of an inflammatory process. In 21 patients with SSTR-expressing tumors, the semiquantitative region-of-interest analysis showed that (99m)Tc-TOC achieved higher tumor-to-normal tissue ratios than (111)In-OCT. CONCLUSION: This study revealed a higher sensitivity of (99m)Tc-TOC as compared with (111)In-OCT as an imaging agent for the localization of SSTR-expressing tumors. To avoid false-positive findings with (99m)Tc-OCT due to nonspecific tracer accumulation, additional scanning at 1-2 h after injection should be done.
Abstract: The aim of this study was to describe the anatomical structures that show uptake of the somatostatin analogue octreotide in patients with thyroid-associated orbitopathy (TAO). The study population comprised a series of 20 TAO patients attending the out-patient thyroid clinic and 12 patients presenting head or neck tumours. Scintigraphy was carried out with our newly developed tracer, technetium-99m labelled EDDA-HYNIC-TOC ((99m)Tc-TOC). Morphological imaging was done with either magnetic resonance imaging or X-ray computed tomography without contrast medium. Both imaging procedures were done within an interval of 3-4 weeks. For the image fusion procedure, specific external reference markers were used for each imaging modality. The markers were screwed onto a reference frame, which was held in place via a vacuum-fixed mouthpiece. The anatomical structure showing tracer uptake that was most frequently recognised was the lacrimal gland, followed by the retronasal area, cervical lymph structures, salivary glands, the anterior insertion points of the extra-ocular muscles and discrete areas of the neck extensor muscles. The lacrimal gland and the retronasal area showed the highest and most frequent uptake of (99m)Tc-TOC in TAO patients, whereas such uptake did not occur in the retrobulbar space. In spite of knowledge of these results of image fusion, no changes in the involved structures could be detected on morphological imaging. It is concluded that binding of (99m)Tc-TOC is more frequently localised to the anterior compartment of the eye and to the neck. The previously used term "orbital" uptake should be abandoned and replaced by a descriptive term relating to the anatomically recognised structure showing tracer accumulation, i.e. the lacrimal gland. The uptake of octreotide by lymphoid and salivary glands opens a new field of investigation related to the physiology of somatostatin.
Abstract: After the discovery of several specific peptide receptors in a variety of cancer types more than 10 years ago, radiolabeled peptide analogs with adequate stability, receptor binding properties, and biokinetic behavior were introduced for imaging of neuroendocrine tumors, several adenocarcinomas, lymphoma, and melanoma. Although initially 123I or 111In were used for labeling, recent efforts have also concentrated on 99mTc or PET-radionuclides (18F,68Ga), as they result in better image resolution with lower radiation dose to patients. Scintigraphy with labeled somatostatin analogs (99mTc, 111In,18F,68Ga), with 123I-labeled vasoactive intestinal peptide, and recently 99mTc-bombesin/GRP-or-111In gastrin analogs, have shown a mean sensitivity of greater than 85% to localize deposits of tumors, with appropriate receptor expression frequently scarcely visible with other imaging procedures. Moreover, these observations introduced peptide-targeted metabolic radiotherapy for metastatic cancers. This development has produced a considerable amount of preclinical studies to broaden the impact of labeled peptide ligands on the management of cancer.
Abstract: Striatal dopamine transporter (DAT) function was evaluated in rats by in vivo SPECT-MRI coregistration using the radioligand 2-beta-carbomethoxy-3-beta-(4-[123I]iodophenyl)tropane (beta-[123I]CIT). The reconstructed transaxial resolution of 3.5 mm full width at half-maximum and the system sensitivity of 0.081 c/s/kBq using a 2.0-mm pinhole collimator aperture provided adequate spatial detail and sufficient sensitivity for imaging striatal beta-[123I]CIT uptake. SPECT images, coregistered onto a MRI template, showed high accuracy in the coronal and transverse planes (maximum mismatch of 1.3 mm). Following estimation of the in vivo binding equilibrium of beta-[123I]CIT in the healthy rat striatum, we evaluated the 6-hydroxydopamine-induced loss of striatal DAT function using beta-[123I]CIT SPECT and MRI coregistration and correlated these findings with dopaminergic cell counts in the substantia nigra pars compacta using TH immunohistochemistry. A subtotal unilateral DAT deficit was detected by beta-[123I]CIT SPECT in all animals which correlated significantly with the cell counting of the remaining dopaminergic neurons. beta-[123I]CIT pinhole SPECT provides a powerful and widely available tool for in vivo investigations of rat striatal DAT function. In contrast to classical autoradiography, the present method will be helpful in imaging dynamic changes of neurotransmission in the CNS by virtue of serial study designs. Depending on SPECT ligand availability, a wide range of other CNS receptors may be imaged as well using the presented in vivo technique.
Abstract: Because of the ideal properties of technetium-99m for imaging, more methods have been developed for labelling peptides and other biomolecules with this radionuclide that any other. While few detailed comparative studies have been performed, it has become apparent that the use of different labelling procedures can exert a profound effect on the pattern of biodistribution after intravenous administration of the radiotracer. The most significant influence of the labelling method is on the rate and route of excretion of the radionuclide. While some procedures tend to direct excretion towards the hepatobiliary route, others tend to favour renal clearance. Although the factors which exert this influence are still not fully understood, it is clear that the charge, lipophilicity and stability of the technetium-peptide complexes play major roles. A greater understanding of these factors will allow the development of improved radiotracers which demonstrate improved targeting potential as a result of lower uptake and consequent radiation dose by normal tissues.
Abstract: To determine whether erythropoietin (EPO) affects haem biosynthesis and iron transport, we studied the effects of EPO on the expression of erythroid 5-aminolevulinate synthase (eALAS), ferrochelatase and divalent metal transporter 1 (DMT-1) in human erythroid progenitor cells, and in the murine and human erythroid cell lines MEL and K562. Cytoplasmic e-ALAS mRNA levels were significantly increased after incubation of cells with EPO for at least 24 h, which could be the result of a transcriptional mechanism. In contrast, ferrochelatase or DMT-1 mRNA expression were not affected. Moreover, EPO also increased e-ALAS enzyme activity after only 4 h of stimulation, when mRNA levels were unchanged. The underlying mechanism was an effect of EPO on e-ALAS mRNA translation, which was under the control of iron regulatory proteins (IRP) 1 and 2. Thereby, EPO weakened the binding affinity of IRP-2 to the iron responsive element (IRE) within e-ALAS mRNA which resulted in the increased expression of e-ALAS IRE-controlled reporter gene constructs, following EPO stimulation. Our results show that EPO directly affected haem biosynthesis by stimulating the transcriptional and post-transcriptional expression of the key enzyme e-ALAS. These data provide new insights into the complex biochemical interaction between iron metabolism, haem biosynthesis and EPO biology.
Abstract: Labelling of the hydrophobic surfactant protein B (SP-B) under non-reducing conditions was achieved with [(99m)Tc(CO)(3)(H2O)(3)](+) prepared according to Alberto et al. (JACS, 1998). The binding of radioactivity was protein-specific, with an overall radiochemical yield of 50%. Gel electrophoresis and Westernblot analyses showed no structural changes of SP-B. Spreading properties and surface activity of (99m)Tc-labelled SP-B in an air/water interface coincided with those of unlabelled SP-B. (99m)Tc-SP-B seems to be a promising agent to observe surfactant spreading under clinical conditions. BACKGROUND: Therapeutic results for surfactant instillation in clinical trials are conflicting. The (99m)Tc-labelling of surfactant would allow to observe its spreading in the lung under clinical conditions. METHODS: [(99m)Tc(CO)(3)(H2O)(3)](+) was prepared as described by Alberto et al. (JACS, 1998). This carbonyl complex was used for the direct labelling of surfactant protein B (SP-B) under non-reductive conditions by direct incubation with SP-B at elevated temperature followed by extraction into CHCl(3)/MeOH. RESULTS: The hydrophobic protein SP-B was labelled with [(99m)Tc(CO)(3)(H2O)(3)](+). An overall radiochemical yield of about 50% was achieved. HPLC-analysis revealed a single radiolabelled species according to UV elution profile of SP-B, supported by paper and size exclusion chromatography. Gel electrophoresis confirmed that the dimer structure of SP-B was preserved. Spreading properties of (99m)Tc-labelled SP-B in an air/water interface coincided with those of unlabelled SP-B. Spreading of radioactivity observed in a glass trough of 26 cm x 27 cm with a gamma camera was completed during the first 7-9 sec after application of (99m)Tc-labelled SP-B. The corresponding decrease of surface tension to 45 mN/m at the peripheral surface tension sensors took 7 sec +/- 2 sec (MEAN +/- STD; n = 3). CONCLUSIONS: Direct and specific (99m)Tc-labelling of the hydrophobic surfactant protein B was achieved using the [(99m)Tc(CO)(3)(H2O)(3)](+) precursor. This procedure can easily be used to prepare specifically labelled surfactant mixtures with spreading properties that coincide with those of unlabelled surfactant.
Abstract: In this paper we describe the preclinical evaluation of 99mTc-hydrazinonicotinyl-Tyr3-octreotide (HYNIC-TOC) using different coligands for radiolabeling and a comparison of their in vitro and in vivo properties with 111In-diethylenetriaminepentaacetic acid (DTPA)-octreotide. METHODS: HYNIC-TOC was radiolabeled at high specific activities using tricine, ethylenediaminediacetic acid (EDDA), and tricine-nicotinic acid as coligand systems. Receptor binding was tested using AR42J rat pancreatic tumor cell membranes. Internalization and protein binding studies were performed, and biodistribution and tumor uptake were determined in AR42J tumor-bearing nude mice. RESULTS: All 99mTc-labeled HYNIC peptides showed retained somatostatin-receptor binding affinities (Kd < 2.65 nM). Protein binding and internalization rates were dependent on the coligand used. Specific tumor uptake between 5.8 and 9.6 percentage injected dose per gram (%ID/g) was found for the 99mTc-labeled peptides, compared with 4.3 %ID/g for 111In-DTPA-octreotide. Tricine as coligand showed higher activity levels in muscle, blood, and liver, whereas tricine-nicotinic acid produced significant levels of activity in the gastrointestinal tract. EDDA showed the most promising overall biodistribution profile, with tumor-to-liver and tumor-to-gastrointestinal tract ratios similar to those obtained with 111In-DTPA-octreotide, lower ratios in blood and muscle, but considerably higher tumor-to-kidney ratios. CONCLUSION: TOC can be radiolabeled to high specific activities using HYNIC as a bifunctional chelator. The high specific tumor uptake, rapid blood clearance, and predominantly renal excretion make 99mTc-EDDA-HYNIC-TOC a promising candidate for an alternative to 111In-DTPA-octreotide for tumor imaging.
Abstract: Radiochemical purity is an important quality parameter for radiopharmaceuticals. In this study, the radiochemical purity of 2090 samples out of 7000 routine preparations of 20 different 99Tcm radiopharmaceuticals was tested using standard methods over a period of more than 7 years. The mean radiochemical purity was 96.92% (standard deviation = 6.71%). Seventy-four preparations failed to meet radiochemical purity limits; that is, 3.54% of all preparations tested or 1.06% of all preparations in the observation period. The reasons for substandard preparations were mainly related to laboratory-specific conditions. The introduction of a dedicated quality control protocol allowed the elimination of many sources of labelling failures and could reduce the number of administered preparations with an insufficient radiochemical purity. We stress the need for quality control in the preparation of radiopharmaceuticals and provide original radiochemical purity values of routinely prepared 99Tcm radiopharmaceuticals.
Abstract: [111In-diethylene triamine penta-acetic acid-D-Phe1]-octreotide (DTPA-octreotide) scintigraphy has gained widespread acceptance as a diagnostic clinical procedure in oncology for imaging somatostatin receptor-positive tumours. However, indium-111 as a radiolabel has several drawbacks, including limited availability, suboptimal gamma energy and high radiation burden to the patient. We have recently reported on the preclinical development of 99mTc-EDDA/HYNIC-TOC, a new octreotide derivative which showed promising results both in vitro and in vivo. We now report our initial clinical experiences with this new radiopharmaceutical in ten oncological patients. The clinical diagnoses were: carcinoid syndrome (n=5), thyroid cancer (n=3), pancreatic cancer (n=1) and pituitary tumour (n=1). The biodistribution and kinetics of 99mTc-EDDA/HYNIC-TOC were compared with those of 111In-DTPA-octreotide in six cases, and with those of 111In-DOTA-TOC in five cases. With the new tracer tumours were imaged within 15 min after injection and showed the highest target/non-target ratios 4 h after injection. Tumour uptake persisted up to 20 h p.i. The rate of blood clearance was similar to that of 111In-DTPA-octreotide but faster than that of 111In-DOTA-TOC, while urinary excretion was lower compared with the 111In derivatives. Semi-quantitative region of interest analysis showed that 99mTc-EDDA/HYNIC-TOC produced higher tumour/organ (target/non-target) ratios than the 111In derivatives, especially in relation to heart and muscle. Significantly more lesions could be detected in 99mTc images. We conclude that 99mTcEDDA/HYNIC-TOC shows better imaging properties for the identification of somatostatin receptor-positive tumour sites than currently available 111In-labelled octreotide derivatives.
Abstract: The synthesis of conjugates of two somatostatin analogues, RC-160 and [Tyr3]octreotide with different bifunctional chelators for labeling with Tc-99m, is described. Conjugates with hydrazinonicotinamide (HYNIC) and two N3S compounds (benzoyl MAG3 and a N3S adipate derivative) were prepared on a small scale with high purity allowing evaluation of different bifunctional chelators on the same peptide without extensive peptide synthesis. High in vitro stability and retained binding affinity was found for all conjugates except for the N3S adipate. Peptide conjugates could be labeled at high specific activities (>1 Ci/micromol) with 99mTc, and different coligands were explored for the HYNIC conjugates. The resulting radiolabeled complexes were highly stable and showed binding affinity to somatostatin receptors in the nanomolar range. Varying labeling yield, stability, lipophilicity, and isomerism were found for different coligands used for labeling HYNIC conjugates, with lower lipophilicity, higher stability, and fewer coordination isomers for EDDA and tricine/nicotinic acid as ternary coligand compared to tricine. In particular, HYNIC complexes showed promising results for further in vivo evaluation.
Abstract: The aim of this study was to explore the effects of lipophilicity and stability on the biodistribution of 99mTc labelled peptides through the use of different co-ligands. 6-Hydrazinopyridine-3-carboxylic acid (HYNIC) was coupled to the somatostatin analogue RC160 and radiolabelled using a range of ethylendiaminediacetic acid (EDDA) and ethylenediaminetetraacetic acid (EDTA) derivatives as well as tricine and pyridine/tricine as co-ligands. After labelling with technetium-99m, chromatographic, stability, protein-binding, and rat biodistribution studies were performed. For most co-ligands, biodistribution correlated well with in vitro properties. Lipophilic substitution on EDDA resulted in higher protein binding, increased liver uptake, and intestinal excretion. Stabilisation of tricine with pyridines reduced blood levels and lowered liver uptake. EDTA derivatives showed high instability in vitro and in vivo.
Abstract: In this paper the preclinical evaluation of the somatostatin analogue RC160 labelled with technetium-99m using bifunctional chelators (BFCs) based on the hydrazinonicotinamide (HYNIC) and N(3)S system is described and a comparison made with [Tyr(3)]-octreotide (TOC). Conjugates of both peptides with HYNIC, and of RC160 with benzoyl-MAG(3) and an N(3)S-adipate derivative were prepared and radiolabelling performed at high specific activities using tricine, tricine/nicotinic acid and ethylenediamine-N,N'-diacetic acid (EDDA) as co-ligands for HYNIC conjugates. All conjugates and (99m)Tc-labelled peptides showed preserved binding affinity for the somatostatin receptor (IC50, Kd<5 nM). The biodistribution was markedly dependent on the BFC and co-ligand used, with the amidothiol ligands showing a greater degree of hepatobiliary clearance, the HYNIC/tricine complex higher blood levels and the HYNIC/EDDA complex the highest level of renal excretion and lowest blood levels. All peptide conjugates showed receptor-mediated uptake in tumour xenografts, but tumour uptake was significantly lower for the (99m)Tc-RC160 derivatives compared with (99m)Tc-EDDA/HYNIC-[Tyr(3)]-octreotide (0.2%-3.5%ID/g vs 9.7%ID/g) and correlated well with the reduced internalisation rate for RC160 derivatives. Our results show that the selection of the labelling approach as well as the right choice of the peptide structure are crucial for labelling peptides with (99m)Tc to achieve complexes with favourable biodistribution. Despite the relatively low tumour uptake compared with (99m)Tc-EDDA/HYNIC-[Tyr(3)]-octreotide, (99m)Tc-RC160 could play a role in imaging tumours that do not bind octreotide derivatives.
Abstract: A novel approach for the determination of the stannous content in cold kits for labelling with 99mTc is described. The method is based on differential pulse polarography on the hanging mercury drop electrode in a methanol/water/perchloric acid mixture and is easy to perform. Examples for the determination of tin(II) in fractionated technetium cold kits are shown. The stability of tin(II) in solution was mainly dependent on the storage temperature and the kit composition. The low stability of stannous ions under certain conditions was shown to be the main reason for low radiochemical purity. Limits and dangers of fractionating kits are discussed and related to content and instability of tin(II).
Abstract: Fatty acids are promptly taken up, metabolised and eliminated by healthy cardiomyocytes. Cardiomyopathy, coronary heart disease and chronic rejection are known to be associated with an impaired fatty acid metabolism. It was the aim of this study to investigate fatty acid metabolism in a rat heart transplant model and to correlate scintigraphic findings with histological changes. After right-side nephrectomy of Lewis recipients Brown Norway cardiac allografts were anastomosed to the renal vessels. Animals were given no immunosuppression. The metabolism of carrier-free 17-123 jodo-heptadecanoic acid (123J-HDA) with a specific activity of > 2 x 10(17) Bq/ml was scintigraphically measured between days 1 and 11. An increase in the grade of rejection was observed over time. Fifty-six frames of 30 s duration each were recorded. For the region of interest (native heart, transplanted heart, left kidney) frames 10-56 were superimposed, time-activity curves generated and monoexponentially fitted. Furthermore, elimination half-life and intercepts were calculated. Following scintigraphic evaluation the animals were killed and graft as well as native hearts excised for histological examination. The uptake of the tracer identified severe grades of rejection. Elimination half-life of the tracer was twice as long from hearts with mild rejection and more than 14 times as long in severe rejection compared with no rejection. Elimination half-life and amplitude did not permit discrimination between grades 1, 2 and 3 a, but significantly decreased in groups 3 b and 4. This method therefore seems to be a valuable tool for the noninvasive detection of severe acute cardiac allograft rejection. Since fatty acid metabolism is clearly stress-dependent it remains to be seen whether this method allows detection of earlier rejection in loaded hearts.
Abstract: Dementia of the Alzheimer-type (DAT) is characterized by progressive cognitive decline, variably combined with frontal lobe release signs, parkinsonian symptoms and myoclonus. The features of diffuse Lewy body disease (DLBD), the second most common cause of degenerative dementia, include progressive cognitive deterioration, often associated with levodopa-responsive parkinsonism, fluctuations of cognitive and motor functions, psychotic symptoms (visual and auditory hallucinations, depression), hypersensitivity to neuroleptics and orthostatic hypotension. A recent report suggests that positron emission tomography studies in patients with degenerative dementia may be useful in the differential diagnosis of DAT and DLBD. However, the diagnostic role of single-photon emission tomography (SPET) studies remains to be established. The aim of this study was therefore to evaluate regional cerebral perfusion [with either technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO) or 99mTc-ethyl cysteinate dimer (99mTc-ECD) SPET] and striatal dopamine transporter density [using iodine-123 2 beta-carboxymethoxy-3 beta-[4-iodophenyl]tropane (123I-beta-CIT) SPET] in patients with DAT and DLBD. Six patients with probable DAT and seven patients with probable DLBD were studied. Blinded qualitative assessment by four independent raters of 99mTc-HMPAO or 99mTc-ECD SPET studies revealed bilateral temporal and/or parietal hypoperfusion in all DAT patients. There was additional frontal hypoperfusion in two patients and occipital hypoperfusion in one patient. In the DLBD group, regional cerebral perfusion had a different pattern. In addition to temporoparietal hypoperfusion there was occipital hypoperfusion resembling a horseshoe defect in six of seven patients. In the DAT group, the mean 3-h striatal/cerebellar ratio of 123I-beta-CIT binding was 2.5 +/- 0.4, with an increase to 5.5 +/- 1.1 18 h after tracer injection. In comparison, in the DLBD patients the mean 3-h striatal/cerebellar ratio of 123I-beta-CIT binding was significantly reduced to 1.7 +/- 0.3, with a modest increase to 2.1 +/- 0.4 18 h after tracer injection (P < 0.05, Scheffe test, ANOVA). These results suggest that 99mTc-HMPAO or 99mTc-ECD and 123I-beta-CIT SPET may contribute to the differential diagnosis between DAT and DLBD, showing different perfusion patterns and more severe impairment of dopamine transporter function in DLBD than in DAT.
Abstract: Thyroid associated ophthalmopathy (TAO) is a disorder involving the soft tissues and extraocular muscles of the orbit seen mainly in cases of Graves' disease. Although an immunogenic pathogenesis has been proposed, the actual mechanisms of the in vivo retrobulbar involvement are not well defined. The recent introduction of the 111In-labeled somatostatin analog, octreotide, which can bind in vivo to the cell membrane of activated lymphocytes expressing somatostatin receptors, has provided a new investigational tool for diseases with a presumed immunological background. Based on this property, octreotide scans can be expected to be positive in cases of immunological disease showing tracer accumulation within affected sites. The aim of this study was to evaluate the utility of scintigraphic imaging with octreotide of the retrobulbar space in cases of TAO, including sequential studies of patients undergoing immunosuppressive therapy. We studied a series of 51 patients who had Graves' disease with varying degrees of TAO. Nine patients had received immunosuppressive therapy. The degree of orbital inflammation was classified according to the clinical activity score of Mourits. Both planar and tomographic imaging of the orbit were carried out using 111 MBq of the 111In-labeled octreotide (OctreoScan) 2 h after tracer injection. A significant tracer accumulation in the retrobulbar space was seen in all 20 patients with a high activity score, in 8 of 16 cases with a negative score, and in 11 of 20 cases with an intermediate Mourits' score. In cases of persistent eye disease in spite of immunosuppressive therapy, the octreotide scan remained positive. Successful therapy either with prednisolone, external radiation, or i.v. immunoglobulins showed a significant diminution of tracer uptake after finishing the therapeutic regime. Three-dimensional reconstruction of the images also revealed a significant tracer accumulation in the areas of the lacrimal gland, the nasal region, and the pituitary. Controls cases (n = 30) showed no uptake in the orbital region. We conclude that 111In octreotide scintigraphy is an objective method that identifies patients with active inflammatory eye disease, i.e., having significant tracer uptake in the retrobulbar space. This uptake appears to reflect an immunological process, since immunosuppressive therapy will significantly decrease tracer accumulation.
Abstract: The use of Microchannel Plate Analysers (Instant Imager, Canberra Packard), the so called Electronic Autoradiography, in Radiopharmacy is described. The system can be used for quality control of radiopharmaceuticals as well as for scientific research purposes. Quantitative analysis of 2-dimensional radioactive samples of all radionuclides used in Nuclear Medicine (especially 99mTc) can be performed in a very short time with little effort. Advantages and limitations for radiopharmaceutical work are described.
Abstract: Standard bone scintigraphy [using technetium-99m methylene diphosphonate (MDP)] is widely held to be the most sensitive method for the early detection of psoriatic arthropathy. Preliminary results of this study reveal that 99mTc human immunoglobulin (HIG) scintigraphy demonstrates a typical premature pattern of extradermal psoriatic disease in digits indicative of the early stage of psoriatic arthritis. This pattern was also found in a rare case of psoriatic arthropathy without skin lesions. 99mTc-HIG scintigraphy appears to reveal the initial inflammatory characteristics of later bone lesions. In the advanced stage of psoriatic arthritis, 99mTc-MDP and 99mTc-HIG scans were found to be equally sensitive in the detection of the affected joints. Thus 99mTc-HIG scintigraphy seems to be useful in the early detection of psoriatic arthropathy and also in advanced psoriatic arthritis, as well as for the detection of psoriatic arthropathy without skin lesions.
Abstract: Technetium-99m mercaptoacetyltriglycine (MAG3) has been used extensively as a renal function agent for several years. Radioimpurities in the MAG3 kit preparation are not only concentrated and excreted in the kidneys. Therefore proper quality control for renal studies is even more important to make possible a rapid and adequate interpretation of diagnostic studies. The standard method to determine the radiochemical purity is high-performance liquid chromatography (HPLC), which is time consuming and expensive. We set up a new simple thin-layer chromatography (TLC) method based on instant thin-layer silica gel strips as stationary phase for checking the main impurities, free pertechnetate and reduced hydrolysed 99mTc-colloid. Comparison of TLC and HPLC results showed no significant differences (t-test, P < 0.05); the correlation between the results obtained with the two methods in respect of the free pertechnetate content was excellent (r = 0.99913). The TLC method was also efficient in determining the percentage of 99mTc-colloid. The main impurity found in 37 routine preparations was free pertechnetate; the mean radiochemical purity was 97.95%. The time required to perform the analysis was less than 20 min. The new TLC system is a cheap, simple, fast, reliable and accurate method for the quality control of the MAG3 kit preparation, and is especially suitable for routine use.
Abstract: Radiopharmaceuticals are a special group of drugs since many are eventually prepared in the hospital and the nuclear medicine department is responsible for meeting quality criteria such as sterility, radionuclide, radiochemical and chemical purity of these drugs. We tested 266 preparations of 14 different radiopharmaceuticals from commercial kits for their radiochemical purity. Only four compounds showed deficiencies in labelling (anti-granulocyte MAb, HIG, HMPAO, MAG3, altogether 18 preparations). All of them were 99mTc-pharmaceuticals with a relatively low tin content of the kit. The reasons for the poor quality of these products could be found. This study shows the importance of a good quality control system (including other tests like sterility and environmental monitoring) to guarantee the safety and efficacy of radiopharmaceuticals prepared in the hospital.
