Abstract: BACKGROUND: Successful surgery for perianal fistula is contingent upon accurate pre-operative classification of the primary tract and its extensions. We aimed to find, using "evidence based medicine" (EBM) methods, the optimal technique for fistula classification: MRI, anal endosonography (AES) or clinical examination. METHODS: A clinical question was derived, "In patients suspected of having perianal fistula, how does MRI compare to AES and clinical assessment for discriminating simple from complex disease". A search of primary literature and secondary evidence resources was performed and expert opinion sought. Inclusion criteria were blinded prospective studies (level 2b +) of patients undergoing preoperative MRI, clinical examination +/- AES using a clinical outcome based reference standard. Retrieved literature was appraised using EBM methods. RESULTS: The highest-ranking evidence found was level 1b. MRI is more sensitive 0.97(CI 0.92-1.01) than clinical examination, 0.75(0.65-0.86) but comparable to AES, 0.92(0.85-0.99) for discriminating complex from simple disease. The positive LR for MRI confirming complex disease is 22.7 compared to 2.1 and 6.2 for clinical examination and AES, respectively. CONCLUSION: MRI is the optimal technique for discriminating complex from simple perianal fistula, although AES is superior to clinical examination, and may be used if MRI availability is restricted.
Abstract: AIM: To investigate whether automated diameter assessment was feasible for CT colonography. MATERIALS AND METHODS: Two experienced observers independently measured the maximum diameter of 50 polyps (colonoscopic reference size range 5-12 mm) from colonography datasets using conventionally placed software callipers and a variety of two-dimensional (2D) computed tomography (CT) window settings (colon, abdominal, bone, lung), and also three-dimensional (3D) perspective rendering. Polyps were also measured using automated polyp-segmentation software. Agreement between observers and with the colonoscopic reference measurement was determined using Bland-Altman, Wilcoxon, and Mann-Whitney U analyses. RESULTS: Inter-observer agreement was similar for all window displays: mean difference in millimetres (SD difference; 95% limits of agreement) ranged from 0 (1.7, -3.3, 3.3) for 2D colon to -1.1mm (1.6, -4.3, 2.0) for 3D, compared with -0.5 (2.09, -4.6, 3.6) for automated measurement. When compared to colonoscopy, the largest discrepancy occurred using the 3D display (mean difference 1.3mm, 2.5mm for each observer). There was also a significant difference between estimates and reference size when using the 2D abdominal and 3D displays (p=0.03, <0.001). CONCLUSION: Automated polyp measurement is possible in vivo. Automated and conventional methods have comparable inter-observer agreement. The greatest measurement error is encountered when using a 3D display for estimates of diameter.
Abstract: PURPOSE: To prospectively investigate the relative accuracy and reproducibility of manual and automated computer software measurements by using polyps of known size in a human colectomy specimen. MATERIALS AND METHODS: Institutional review board approval was obtained for the study; written consent for use of the surgical specimen was obtained. A colectomy specimen containing 27 polyps from a 16-year-old male patient with familial adenomatous polyposis was insufflated, submerged in a container with solution, and scanned at four-section multi-detector row computed tomography (CT). A histopathologist measured the maximum dimension of all polyps in the opened specimen. Digital photographs and line drawings were produced to aid CT-histologic measurement correlation. A novice (radiographic technician) and an experienced (radiologist) observer independently estimated polyp diameter with three methods: manual two-dimensional (2D) and manual three-dimensional (3D) measurement with software calipers and automated measurement with software (automatic). Data were analyzed with paired t tests and Bland-Altman limits of agreement. RESULTS: Seven polyps (<or=6-mm diameter) could not be extracted by using the software; 20 polyps (5-15-mm diameter) remained for analysis. Automated measurement was not significantly different from histologic size for the experienced reader (mean difference, 0.63 mm; P=.06) or novice reader (mean difference, 0.58 mm; P=.12). With manual 2D measurement and manual 3D measurement, the experienced reader (1.21-mm mean difference, P<.001, and 0.68-mm mean difference, P=.03, respectively) and novice reader (1.54-mm mean difference, P<.001, and 0.84-mm mean difference, P=.002, respectively) significantly underestimated polyp size. Interobserver agreement was good and similar for all three methods (95% limits of agreement span, approximately 2.5 mm). Intraobserver agreement was related to reader experience, with differences of up to 2.5 mm within expected limits of agreement. CONCLUSION: For polyps smaller than 1 cm, measurement differences of up to 2.5 mm are within the expected limits of inter- and intraobserver agreement for all measurement techniques. Automated and manual 3D polyp measurements are more accurate than manual 2D measurements.
Abstract: AIM: To investigate interpretative accuracy and reporting time for radiologists performing computed tomography (CT) colonography in day-to-day non-academic clinical practice. MATERIALS AND METHODS: Thirteen radiologists from seven centres, who were reporting CT colonography in non-academic daily clinical practice, interpreted a dataset of 15 colonoscopically validated cases in a controlled environment. Ten cases had either a cancer or polyp >10mm; one case had a medium polyp and four were normal. Correct case categorization and interpretation times were compared using analysis of variance to aggregated results obtained from both experienced observers and observers recently trained using 50 cases, working in an academic environment. The effect of experience was determined using Spearman's rank correlation. RESULTS: Individual accuracy was highly variable, range 53% (95% CI 27-79%) to 93% (95% CI 68-100%). Mean accuracy overall was significantly inferior to experienced radiologists (mean 75 versus 88%, p=0.04) but not significantly different from recently trained radiologists (p=0.48). Interpretation time was not significantly different to experienced readers (mean 12.4 min versus 11.7, p=0.74), but shorter than recently trained radiologists (p=0.05). There was a significant, positive, linear correlation between prior experience and accuracy (p<0.001) with no plateau. CONCLUSION: Accuracy for sub-specialist radiologists working in a non-academic environment is, on average, equivalent to radiologists trained using 50 cases. However, there is wide variability in individual performance, which generally falls short of the average performance suggested by meta-analysis of published data. Experience improves accuracy, but alone is insufficient to determine competence.
Abstract: PURPOSE: To determine whether computed tomographic (CT) perfusion measurements in prospectively recruited patients can be used to differentiate between diverticulitis and colorectal cancer and to compare this discrimination with that of standard morphologic criteria. MATERIALS AND METHODS: After institutional review board approval and written informed consent were obtained, 60 patients (24 men, 36 women; mean age, 69 years; range, 33.5-90.4 years; 20 patients with cancer, 20 with diverticulitis, and 20 with inactive diverticular disease) underwent CT perfusion imaging at the level of the colonic abnormality, and perfusion parameters were calculated. Analysis of variance was used to investigate any differences in perfusion between the patient groups. Two independent observers also analyzed an abdominopelvic CT study obtained immediately after the CT perfusion study and noted standard morphologic criteria for differential diagnosis. The sensitivity and specificity of CT perfusion measurements for determining the diagnostic category were compared with morphologic criteria by means of multivariate analysis to identify the most discriminatory criteria. RESULTS: Mean blood volume, blood flow, transit time, and permeability were significantly different between patients with cancer and those with diverticulitis (P < .0001); patients with cancer had the highest blood volume, blood flow, and permeability and the shortest transit time. The most discriminatory criteria for determining diagnostic category were blood volume, transit time, permeability, and presence of pericolonic nodes (P = .05, .02, .04, and .02, respectively). Blood volume and blood flow each had a sensitivity of 80% and had specificity of 70% and 75%, respectively, for cancer in comparison with standard morphologic criteria: less than 5 cm of bowel involvement (45% sensitivity, 95% specificity), presence of a mass (85% sensitivity, 90% specificity), pericolonic inflammation (75% sensitivity, 5% specificity), and pericolonic nodes (90% sensitivity, 45% specificity). CONCLUSION: CT perfusion measurements enable differentiation and better discrimination, in comparison with morphologic criteria, between cancer and diverticulitis.
Abstract: To establish the optimum barium-based reduced-laxative tagging regimen prior to CT colonography (CTC). Ninety-five subjects underwent reduced-laxative (13 g senna/18 g magnesium citrate) CTC prior to same-day colonoscopy and were randomised to one of four tagging regimens using 20 ml 40%w/v barium sulphate: regimen A: four doses, B: three doses, C: three doses plus 220 ml 2.1% barium sulphate, or D: three doses plus 15 ml diatriazoate megluamine. Patient experience was assessed immediately after CTC and 1 week later. Two radiologists graded residual stool (1: none/scattered to 4: >50% circumference) and tagging efficacy for stool (1: untagged to 5: 100% tagged) and fluid (1: untagged, 2: layered, 3: tagged), noting the HU of tagged fluid. Preparation was good (76-94% segments graded 1), although best for regimen D (P = 0.02). Across all regimens, stool tagging quality was high (mean 3.7-4.5) and not significantly different among regimens. The HU of layered tagged fluid was higher for regimens C/D than A/B (P = 0.002). Detection of cancer (n = 2), polyps >/=6 mm (n = 21), and </=5 mm (n = 72) was 100, 81 and 32% respectively, with only four false positives >/=6 mm. Reduced preparation was tolerated better than full endoscopic preparation by 61%. Reduced-laxative CTC with three doses of 20 ml 40% barium sulphate is as effective as more complex regimens, retaining adequate diagnostic accuracy.
Abstract: In this article we provide practical advice for optimizing computed tomography colonography (CTC) technique to help ensure that reproducible, high-quality examinations are achieved. Relevant literature is reviewed and specific attention is paid to patient information, bowel cleansing, insufflation, anti-spasmodics, patient positioning, CT technique, post-procedure care and complications, as well as practical problem-solving advice. There are many different approaches to performing CTC; our aim is to not to provide a comprehensive review of the literature, but rather to present a practical and robust protocol, providing guidance, particularly to those clinicians with little prior experience of the technique.
Abstract: OBJECTIVES: Colonoscopy is the gold standard for diagnosis of mucosal disease, but has a recognized "miss rate" for polyps probably because some lesions lie in areas of the colonic surface that do not enter the field of view. Using CT colonography (CTC) simulation this pilot study aimed to determine how much colonic surface is visualized with a standard, modern optical colonoscope (field of view 140 degrees ) with or without the addition of a retrograde viewing auxiliary imaging device (RVAID; 135 degrees ) and of a wide-angle (170 degrees ) colonoscope. METHODS: Supine CTC datasets for 20 patients were reviewed with customized CTC software that calculated the percentage of colonic surface seen and number and area of nonvisualized "missed" areas at a unidirectional three-dimensional (3D) endoluminal flythrough, approximating the view obtained at optical colonoscopy. The field of view could be varied from 0-180 degrees . The combination of a colonoscope with RVAID was simulated by an additional flythrough facing the rectum. RESULTS: Mean colonic surface area was 2,743 +/- 759 cm(2). Percentage colonic surface visualized at simulated optical colonoscopy with a 90 degrees , 140 degrees , and 170 degrees field of view was 68.0 +/- 5.2%, 86.6 +/- 3.3%, and 92.2 +/- 3.3%, respectively, P < 0.001. Simulation of a 140 degrees colonoscope with an RVAID resulted in almost complete surface visualization, 98.7 +/- 0.5%, with total missed area reduced 10-fold compared with a 170 degrees colonoscope, P < 0.001. CONCLUSION: CTC simulated 140 degrees optical colonoscopy visualizes over 85% of the colonic surface. 170 degrees colonoscopy provides a modest reduction in missed surface and the simulated addition of RVAIDs appears beneficial.
Abstract: AIM: Expert consensus recommends directed training and possibly in the future, formal accreditation before independent virtual colonoscopy (VC) reporting. We surveyed radiologists' experience of VC training, compared with barium enema, and assessed attitudes towards accreditation. MATERIALS AND METHODS: A questionnaire was sent to 78 consultant radiologists from 72 centres (65 National Health Service hospitals; seven independent primary screening centres) offering a VC service. RESULTS: Fifty-four (69%) eligible radiologists responded. They had interpreted 18,152 examinations (range 3-1500) in total versus 232,350 (13 times more) barium enemas. Twenty-two (41%) deemed their VC training as inadequate [including five (45%) of screening centre radiologists], and only 14 (26%) had attended a training workshop due to lack of availability (54%) or financial/study leave constraints (24%). Eleven (20%) radiologists routinely double-reported VC examinations versus 37 (69%) barium enemas, yet 21 (39%) considered requirements for VC training were greater than barium enema. Thirty-eight (70%) favoured accreditation beyond internal audit for VC versus 15(28%) for barium enema. Of these 38, seven (18%) favoured "one-off," and 18 (47%) periodic testing, with 16 (42%) favouring external audit alone or in combination with testing. Overall, 42 (78%) considered specific accreditation for reporting screening examinations appropriate and 45 (83%) respondents preferred a national radiological organization to regulate such a scheme. CONCLUSION: There is wide variability in reporting experience and recommendations for VC training have not been widely adopted, in part due to limited access to dedicated workshops. UK radiologists are generally in favour of VC accreditation, governed by a national radiology organization.
Abstract: Our purpose was to assess the effect of reader experience, fatigue, and scan findings on interpretation time for CT colonography. Nine radiologists (experienced in CT colonography); nine radiologists and ten technicians (both groups trained using 50 validated examinations) read 40 cases (50% abnormal) under controlled conditions. Individual interpretation times for each case were recorded, and differences between groups determined. Multi-level linear regression was used to investigate effect of scan category (normal or abnormal) and observer fatigue on interpretation times. Experienced radiologists (mean time 10.9 min, SD 5.2) reported significantly faster than less experienced radiologists and technicians; odds ratios of reporting times 1.4 (CI 1.1, 1.8) and 1.6 (1.3, 2.0), respectively (P<or=0.001). Experienced and less-experienced radiologists took longer to report abnormal cases; ratio 1.2 (CI 1.1,1.4, P<0.001) and 1.2 (1.0, 1.3, P=0.03), respectively. All groups took 70% as long to report the final five cases as they did with an initial five; ratio 0.7 (CI 0.6 to 0.8), P<0.001. For technicians only, accuracy increased with longer reporting times (P=0.04). Experienced radiologists report faster than do less-experienced observers and proportionally spend less time interpreting normal cases. Technicians who report more slowly are more accurate. All groups reported faster as the study period progressed.
Abstract: PURPOSE: To retrospectively determine the incidence of potentially serious adverse events associated with computed tomographic (CT) colonography performed in patients with symptoms of colorectal cancer. MATERIALS AND METHODS: Ethical approval and informed consent were waived, since the study was deemed a clinical audit and patients would not be approached. With a national survey in the United Kingdom, all departments offering CT colonography in everyday practice were identified. The lead gastrointestinal radiologist from all responding departments was interviewed, and the frequency of potentially serious adverse events associated with CT colonography performed in patients with symptoms of colorectal cancer, the total number of examinations performed, and technical factors possibly related to perforation were determined. Where a potentially serious adverse event was encountered, it was explored in detail. Responses were collated, and raw frequencies were determined. Fisher exact test was used to determine differences in event rates between groups. RESULTS: At 50 centers, 17 067 CT colonographic examinations (mean number per center, 359; range, 10-3000) were performed. No deaths were reported. Thirteen patients (one [0.08%] of 1313) had had a potentially serious adverse event related to the procedure. There were nine perforations: Four (44%) were asymptomatic and five (56%) were symptomatic, and perforation had an attributable cause, with a symptomatic perforation rate of 0.03% (one in 3413 patients). One patient required laparotomy. An inflated rectal balloon was used to perform 9378 examinations. There was no significant difference between the proportion of perforations associated with rectal balloon inflation (n = 6) and the proportion of those that were not (n = 2) (P = .3). CONCLUSION: Potentially serious adverse events related to CT colonography occurred in 0.08% of symptomatic patients.
Abstract: OBJECTIVE: The purpose of our study was to compare the effects of automated and manual carbon dioxide insufflation before CT colonography on distention and patient acceptance. SUBJECTS AND METHODS: One hundred forty-one symptomatic subjects underwent CT colonography using either an automated device (n = 47) or a manual method (n = 94) for carbon dioxide insufflation. CT data sets were assessed retrospectively in consensus by two blinded observers who graded distention for six colonic segments using a 4-point scale. An additional assessment of the overall clinical adequacy of distention (yes/no) was also made, and any learning curve was sought. Each patient completed a validated 24-point patient questionnaire reflecting patient satisfaction and discomfort. Distention scores, clinical adequacy, and questionnaire responses were analyzed using ordered logistic regression, Fisher's exact test, and the Mann-Whitney test statistic, respectively. RESULTS: Automated insufflation significantly improved distention overall (p = 0.001). For individual segments, distention was significantly improved in the sigmoid (p = 0.007) and descending (p < 0.001) colons when the patient was supine; and in the sigmoid (p = 0.02), descending (p = 0.001), and transverse (p = 0.02) colons when supine and prone positions were combined. No significant difference was seen in the clinical adequacy of distention, nor was there evidence of any learning curve for either insufflation method. Subjects were more weary after automated insufflation (p = 0.03), but no significant difference was seen for the remaining 23 questionnaire items or for feelings of bloating or discomfort. CONCLUSION: Automated carbon dioxide insufflation significantly improves colonic distention compared with manual insufflation. Benefit is greatest in the left colon, particularly when the patient is supine. Patient acceptance is similar to that for manual insufflation.
Abstract: OBJECTIVE: The purpose of our study was to assess the sensitivity of computer-assisted reader (CAR) software for polyp detection compared with the performance of expert reviewers. MATERIALS AND METHODS: A library of colonoscopically validated CT colonography cases were collated and separated into training and test sets according to the time of accrual. Training data sets were annotated in consensus by three expert radiologists who were aware of the colonoscopy report. A subset of 45 training cases containing 100 polyps underwent batch analysis using ColonCAR version 1.2 software to determine the optimum polyp enhancement filter settings for polyp detection. Twenty-five consecutive positive test data sets were subsequently interpreted individually by each expert, who was unaware of the endoscopy report, and before generation of the annotated reference via an unblinded consensus interpretation. ColonCAR version 1.2 software was applied to the test cases, at optimized polyp enhancement filter settings, to determine diagnostic performance. False-positive findings were classified according to importance. RESULTS: The 25 test cases contained 32 nondiminutive polyps ranging from 6 to 35 mm in diameter. The ColonCAR version 1.2 software identified 26 (81%) of 32 polyps compared with an average sensitivity of 70% for the expert reviewers. Eleven (92%) of 12 polyps > or = 10 mm were detected by ColonCAR version 1.2. All polyps missed by experts 1 (n = 4) and 2 (n = 3) and 12 (86%) of 14 polyps missed by expert 3 were detected by ColonCAR version 1.2. The median number of false-positive highlights per case was 13, of which 91% were easily dismissed. CONCLUSION: ColonCAR version 1.2 is sensitive for polyp detection, with a clinically acceptable false-positive rate. ColonCAR version 1.2 has a synergistic effect to the reviewer alone, and its standalone performance may exceed even that of experts.
Abstract: PURPOSE: To retrospectively compare primary three-dimensional (3D) endoluminal analysis with primary two-dimensional (2D) transverse analysis supplemented by computer-assisted reader (CAR) software for computed tomographic (CT) polyp detection and reader reporting times. MATERIALS AND METHODS: Ethical permission and patient consent were obtained from all donor institutions for use of CT colonography data sets. Twenty CT colonography data sets from 14 men (median age, 61 years; age range, 52-78 years) with 48 endoscopically proved polyps were selected. Polyp coordinates were documented in consensus by three unblinded radiologists to create a reference standard. Two radiologists read the data sets, which were randomized between primary 3D endoluminal views with 2D problem solving and 2D views supplemented by CAR software. Reading times and diagnostic confidence were documented. The CAR software highlighted possible polyps by superimposing circles on the 2D transverse images. Data sets were reread after 1 month by using the opposing analysis method. Detection rates were compared by using the McNemar test. Reporting times and diagnostic confidence were compared by using the paired t test and Mann-Whitney U test, respectively. RESULTS: Mean sensitivity values for polyps measuring 1-5, 6-9, and 10 mm or larger were 14%, 53%, and 83%, respectively, for 2D CAR analysis and 16%, 53%, and 67%, respectively, for primary 3D analysis. Overall sensitivity values were 41% for 2D CAR analysis and 39% for primary 3D analysis (P=.77). Reader 1 detected more polyps than reader 2, particularly when using the 3D fly-through method (P=.002). Mean reading times were significantly longer with the 3D method (P=.001). Mean false-positive findings were 1.5 for 2D analysis and 5.5 for 3D analysis. Reader confidence was not significantly different between analysis methods (P=.42). CONCLUSION: Two-dimensional CAR analysis is quicker and at least matches the sensitivity of primary 3D endoluminal analysis, with fewer false-positive findings.
Abstract: The extent measurement error on CT colonography influences polyp categorisation according to established management guidelines is studied using twenty-eight observers of varying experience to classify polyps seen at CT colonography as either 'medium' (maximal diameter 6-9 mm) or 'large' (maximal diameter 10 mm or larger). Comparison was then made with the reference diameter obtained in each patient via colonoscopy. The Bland-Altman method was used to assess agreement between observer measurements and colonoscopy, and differences in measurement and categorisation was assessed using Kruskal-Wallis and Chi-squared test statistics respectively. Observer measurements on average underestimated the diameter of polyps when compared to the reference value, by approximately 2-3 mm, irrespective of observer experience. Ninety-five percent limits of agreement were relatively wide for all observer groups, and had sufficient span to encompass different size categories for polyps. There were 167 polyp observations and 135 (81%) were correctly categorised. Of the 32 observations that were miscategorised, 5 (16%) were overestimations and 27 (84%) were underestimations (i.e. large polyps misclassified as medium). Caution should be exercised for polyps whose colonographic diameter is below but close to the 1-cm boundary threshold in order to avoid potential miscategorisation of advanced adenomas.
Abstract: BACKGROUND & AIMS: In isolation, computer-aided detection (CAD) for computed tomographic (CT) colonography is as effective as optical colonoscopy for detection of significant adenomas. However, the unavoidable interaction between CAD and the reader has not been addressed. METHODS: Ten readers trained in CT but without special expertise in colonography interpreted CT colonography images of 107 patients (60 with 142 polyps), first without CAD and then with CAD after temporal separation of 2 months. Per-patient and per-polyp detection were determined by comparing responses with known patient status. RESULTS: With CAD, 41 (68%; 95% confidence interval [CI], 55%-80%) of the 60 patients with polyps were identified more frequently by readers. Per-patient sensitivity increased significantly in 70% of readers, while specificity dropped significantly in only one. Polyp detection increased significantly with CAD; on average, 12 more polyps were detected by each reader (9.1%, 95% CI, 5.2%-12.8%). Small- (< or =5 mm) and medium-sized (6-9 mm) polyps were significantly more likely to be detected when prompted correctly by CAD. However, overall performance was relatively poor; even with CAD, on average readers detected only 10 polyps (51.0%) > or =10 mm and 24 (38.2%) > or =6 mm. Interpretation time was shortened significantly with CAD: by 1.9 minutes (95% CI, 1.4-2.4 minutes) for patients with polyps and by 2.9 minutes (95% CI, 2.5-3.3 minutes) for patients without. Overall, 9 readers (90%) benefited significantly from CAD, either by increased sensitivity and/or by reduced interpretation time. CONCLUSIONS: CAD for CT colonography significantly increases per-patient and per-polyp detection and significantly reduces interpretation times but cannot substitute for adequate training.
Abstract: PURPOSE: To investigate effect of attenuation of tagged fluid and viewing window on polyp conspicuity and measurement with porcine colonic specimen. MATERIALS AND METHODS: Eleven (3-10-mm-diameter) polyps were created in porcine colon and the specimen submerged in saline. Four-detector row CT was performed after gas distension and after filling with six barium sulfate suspensions (attenuation, 100-1000 HU). Two readers independently measured maximal two-dimensional polyp diameter on each data set with the following four viewing windows and window levels and window widths, respectively: colon (-150 HU, 1500 HU), lung (-500 HU, 1500 HU), bone (500 HU, 2500 HU), and abdomen (40 HU, 400 HU). In consensus, polyp conspicuity (compared with air data set) was assigned a grade of 1-4 for each viewing window (grade 1, not seen or barely visible; grade 4, optimally seen). For statistical analysis, conspicuity grades were collapsed to a two-point scale. Data were analyzed with Mann-Whitney, Kruskal-Wallis, and chi2 tests. RESULTS: Accuracy of polyp measurement was independent of viewing window for attenuation of tagged fluid of 100-300 HU but differed significantly for 500-1000 HU (P < .001); that for colonic and bone viewing windows was superior (median size difference, 1.0 mm; interquartile range, 0.5-1.5). Conspicuity differed significantly according to viewing window at all attenuation values (P < .001). For 100-300 HU with abdominal viewing window, 83% (24 of 29) of observations were assigned grade 3 or 4 (best). For 500-1000 HU with bone viewing window, 94% (30 of 32) of observations were assigned grade 3 or 4 (superior). Overall conspicuity was best with bone viewing windows at 700 HU. CONCLUSION: Polyp conspicuity and measurement in tagged data sets were optimized at 700 HU with bone viewing windows. At less than 300 HU, conspicuity improved with abdominal viewing windows.
Abstract: RATIONAL AND OBJECTIVES: To investigate the effect of colonic distension on polyp measurement accuracy and reader agreement. MATERIALS AND METHODS: Institutional review board permission was obtained. A sealed colectomy specimen from a patient with familial adenomatous polyposis was scanned using a four-detector-row computed tomography (CT) after half and full air distension. A histopathologist measured the maximum dimension of all polyps in the opened specimen. Digital photographs and line drawings were used to individually match polyps visible in the CT datasets. Two observers (radiologist, technician) independently estimated the maximum polyp diameter using both two-dimensional (2D) and three-dimensional (3D) surface rendering. Full-distension measurements were repeated 1 week later. Accuracy was analyzed using paired t-test. Observer agreement was assessed using Bland Altman limits of agreement. RESULTS: Twenty-three polyps (4-15 mm) were identified. 2D measurements were significantly smaller than histologic size at both half distension (radiologist first): mean difference [md] -1.1 mm, md -1.7 mm, and full distension md -1.1 mm, md 1.4 mm (all P < .001). 3D measurements were not significantly different from true size other than after half distension for the technician (md -0.7 mm, P = .01). 95% Bland Altman limits for interobserver agreement were narrower after full distension, and better using 2D (half-distension span of agreement approximately 4.7 mm and 6 mm for 2D and 3D, respectively). 2D intraobserver span of agreement between half and full distension was approximately 3.8 mm and 3.2 mm for the radiologist and technician, respectively, compared with 6.2 mm and 5.5 mm using 3D. CONCLUSION: 3D polyp measurement is more accurate than 2D. However, in the presence of suboptimal distension, inter- and intraobserver agreement is superior using 2D.
Abstract: This study investigated the variability in baseline computed tomography colonography (CTC) performance using untrained readers by documenting sources of error to guide future training requirements. Twenty CTC endoscopically validated data sets containing 32 polyps were consensus read by three unblinded radiologists experienced in CTC, creating a reference standard. Six readers without prior CTC training [four residents and two board-certified subspecialty gastrointestinal (GI) radiologists] read the 20 cases. Readers drew a region of interest (ROI) around every area they considered a potential colonic lesion, even if subsequently dismissed, before creating a final report. Using this final report, reader ROIs were classified as true positive detections, true negatives correctly dismissed, true detections incorrectly dismissed (i.e., classification error), or perceptual errors. Detection of polyps 1-5 mm, 6-9 mm, and > or =10 mm ranged from 7.1% to 28.6%, 16.7% to 41.7%, and 16.7% to 83.3%, respectively. There was no significant difference between polyp detection or false positives for the GI radiologists compared with residents (p=0.67, p=0.4 respectively). Most missed polyps were due to failure of detection rather than characterization (range 82-95%). Untrained reader performance is variable but generally poor. Most missed polyps are due perceptual error rather than characterization, suggesting basic training should focus heavily on lesion detection.
Abstract: OBJECTIVE: This article presents inter- and intraobserver agreement for estimates of polyp diameter using CT colonography, including the effects of different visualization displays and prior experience. MATERIALS AND METHODS: Four observers, three of whom had prior experience with CT colonography, estimated the maximum diameter of 48 polyps using three different visualization displays: 2D colonography window, 2D abdominal window, and 3D surface rendering. Each re-measured a subset of 10 polyps. Polyps measured 2 to 12 mm according to a colonoscopic reference. Inter- and intraobserver agreement and agreement with the reference measurement were determined using the Bland-Altman method, paired Student's t testing, analysis of variance, and analysis of covariance (ANCOVA), and by calculating the components of variance. RESULTS: CT measurements overestimated polyp diameter, a phenomenon found least using the 2D abdominal display. Generally, 95% limits of agreement encompassed different size categories for individual polyps: the widest spanned 14.6 mm (-4.6 mm to 10.0 mm) for an experienced observer using the 3D display. When using the 2D abdominal display, no significant difference was found between estimates and the reference value for the other two experienced observers (p = 0.83 and 0.23). All the observers' measurements were significantly different from the reference when using the 3D display (p < 0.001). The novice was significantly different from the experienced observers in some analyses. Inter- and intraobserver agreement were poorest for the 3D display. CONCLUSION: Measurement of polyp diameter from CT colonography is subject to variation contingent on the observer's experience and the viewing display used. Although 3D visualization display is commonly used for polyp detection, it should not be used for measurement.
Abstract: AIMS: To compare the subjective acceptability of CT colonography in comparison with barium enema in older symptomatic patients, and to ascertain preferences for future colonic investigation. MATERIALS AND METHODS: The study population comprised 78 persons aged 60 years or over with symptoms suggestive of colorectal neoplasia, who underwent CT colonography followed the same day by barium enema. A 25-point questionnaire was administered after each procedure and an additional follow-up questionnaire a week later. Responses were compared using Wilcoxon matched pairs testing, Mann-Whitney test statistics and binomial exact testing. RESULTS: Participants suffered less physical discomfort during CT colonography (p = 0.03) and overall satisfaction was greater compared with barium enema (p = 0.03). On follow-up, respondents reported significantly better tolerance of CT colonography (p = 0.002), and were less prepared to undergo barium enema again (p < 0.001). Of 52 subjects expressing an opinion, all preferred CT to barium enema. CONCLUSION: Patient satisfaction was higher with CT colonography than barium enema. CT colonography caused significantly less physical discomfort and was overwhelmingly preferred by patients.
Abstract: OBJECTIVE: To investigate inter- and intraobserver agreement of automated measurement of polyp diameter in vitro. METHODS: Two phantoms ("QRM" and "Whiting") containing simulated polyps of known diameter and volume were scanned using 16-detector row computed tomography. Two observers estimated polyp diameter using 3 methods: software calipers ("manual"), freehand boundary identification ("semiautomatic"), and automated software segmentation ("fully automatic"). RESULTS: Intraobserver 95% limits of agreement for diameter were narrowest for the fully automatic method (QRM span: 0.39 mm, 0.48 mm; Whiting span: 0.24 mm, 0 mm). Manual estimates were approximately 10 times wider (QRM span: 3.57 mm, 3.21 mm; Whiting span: 3.2 mm, 2.02 mm). Volume estimates were narrowest for the fully automatic method (span: 24.2 mm, 24.1 mm vs. 97.9 mm, 102.9 mm for semiautomatic measurement). Interobserver agreement for diameter was narrowest for the fully automatic method (QRM span: 0.12 mm, Whiting span: 0.16 mm), with the manual method approximately 18 times wider (QRM span: 2.87 mm, Whiting span: 2.18 mm). CONCLUSION: Fully automated measurement of polyp diameter and volume is technically feasible and results in superior inter- and intraobserver agreement.
Abstract: Virtual colonoscopy (CT colonography) is a technique whereby CT images of the cleansed and distended colon are acquired, ostensibly for detecting colonic neoplasia, although also providing additional diagnostic information from extracolonic organs. This article examines the current status of virtual colonoscopy, reviewing the technical parameters, performance characteristics, and issues surrounding implementation in routine clinical practice. Future directions for virtual colonoscopy are explored, including advances toward prepless examinations and automated interpretation.
Abstract: AIM: To determine the provision of computed tomography (CT) colonography in UK radiology departments. MATERIALS AND METHODS: A questionnaire relating to the availability of CT colonography, barriers to implementation, clinical indications, technique, and practitioners was posted to clinical directors of UK radiology departments. RESULTS: One hundred and thirty-eight departments responded. Fifty (36%) offered CT colonography in day-to-day clinical practice. Of those that did not, 68 of 87 (64%) cited limited scanner capacity as the main barrier. Of the 50 departments offering a service, 39 (78%) offered CT after incomplete colonoscopy, 36 (72%), after failed barium enema, and 37 (74%) as an alternative to barium enema. Of those offering a service, the number of studies performed varied between one per month (38%) to more than one per day (8%). Total experience varied between 20 or fewer studies (28%) to more than 300 (12%). Full bowel preparation was common (92%), as was dual positioning (90%). Colonography was interpreted by radiologists with a subspecialty interest in gastrointestinal imaging in 64% of centres offering a service. CONCLUSION: CT colonography is widely available in the UK, with approximately one-third of responders offering a service. Experience and throughput varies considerably. Limited CT scanner capacity is the major barrier to further dissemination.
Abstract: The purpose of this paper was to investigate the effect of radiologist experience and increasing exposure to CT colonography on reader performance. Three radiologists of differing general experience (consultant, research fellow, trainee) independently analysed 100 CT colonographic datasets. Readers had no prior experience of CT colonography and received feedback and training after the first 50 cases from an independent experienced radiologist. Diagnostic performance and reporting times were compared for the first and second 50 datasets and compared with the results of a radiologist experienced in CT colonography. Before training only the consultant reader achieved statistical equivalence with the reference standard for detection of larger polyps. After training, detection rates ranged between 25 and 58% for larger polyps. Only the trainee significantly improved after training ( P=0.007), with performance of other readers unchanged or even worse. Reporting times following training were reduced significantly for the consultant and fellow ( P<0.001 and P=0.03, respectively), but increased for the trainee ( P<0.001). In comparison to the consultant reader, the odds of detection of larger polyps was 0.36 (CI 0.16, 0.82) for the fellow and 0.36 (CI 0.14, 0.91) for the trainee. There is considerable variation in the ability to report CT colonography. Prior experience in gastrointestinal radiology is a distinct advantage. Competence cannot be assumed even after directed training via a database of 50 cases.
Abstract: First introduced a decade ago, computerized tomography (CT) colonography (virtual colonoscopy) is emerging as an important radiologic investigation for colorectal neoplasia, with diagnostic performance likely exceeding barium enema and comparable with optical colonoscopy. Employing state-of-the-art multislice technology, CT colonography allows a complete examination of the colon and surrounding organs in less than 30 seconds. This article reviews current techniques, indications, comparison with existing technologies, and diagnostic performance. Although already widely disseminated, important future developments, such as prepless bowel cleansing (laxative free) and computer-aided diagnosis, may establish CT colonography as the preferred first-line, whole-colon investigation.
Abstract: AIM: To determine whether the internet is a useful resource for patients seeking information on radiological procedures. MATERIALS AND METHODS: A systematic search of the world wide web was performed by means of four general search engines (AltaVista, Yahoo!, Infoseek and Excite). Twenty-eight suitable patient-directed websites on arteriography were identified for analysis. The value of this material was measured by establishing inclusion or exclusion of a number of factors relating to the procedure. Readability of the materials was evaluated using the Flesch reading ease score. RESULTS: Advice on preparation was included in 21 (75%) sites. Contraindications were found in 16 (57%) sites, risks in 6 (21%) and aftercare in 25 (89%). Result availability was discussed in 15 (54%) sites, with links to other radiology sites in 13 (46%). Visual aids were used in 6 (21%) sites and a contact address found in 27 (96%). Mean Flesch reading ease score was 57, with 46% of sites below the preferred minimum of 60. CONCLUSIONS: Few sites provide the range of information a patient needs before arriving for a procedure. In addition, the readability of the material on these sites is frequently set at a level incomprehensible to patients with lower levels of literacy.
