PubMed Health⌕ Search

Biomedical subjects

Stuart A Taylor

Publications and source records attributed to Stuart A Taylor.

At least 19 recordsLinked to original sources
PubMed2007

European Society of Gastrointestinal and Abdominal Radiology (ESGAR): consensus statement on CT colonography.

Rapid clinical dissemination of CT colonography (CTC) is occurring in parallel with continued research into technique optimisation and diagnostic performance. A need exists therefore for current guidance as to basic prerequisites for effective clinical implementation. A questionnaire detailing CTC technique, analysis, training and clinical implementation was developed by the European Society of Gastrointestinal and Abdominal Radiology (ESGAR) CTC committee and circulated to all faculty members of previous ESGAR "hands-on" CTC training courses. Responses were collated and a consensus statement produced. Of 27 invited to participate, 24 responded. Reasonable consensus was reached on bowel preparation, colonic distension, patient positioning, use of IV contrast and optimal scan parameters. Both primary 2D and primary 3D analysis were advocated equally, with some evidence that more experienced readers prefer primary 2D. Training was universally recommended, although there was no consensus regarding minimum requirements. CTC was thought superior to barium enema, although recommended for screening only in the presence of validated local experience. There was consensus that polyps 4 mm or less could be ignored assuming agreement from local gastroenterological colleagues. There is increasing consensus amongst European experts as to the current best practice in CTC.

Advisory Committees↗
PubMed2006

CT colonography: results and limitations.

Meta-analysis of data from studies of CT colonography suggests that it has excellent per-patient average sensitivity and average specificity for detection of adenomatous polyps and cancer. However, while its potential as a screening test is undoubted, there are several current limitations that will need to be overcome before it can be considered seriously by health policy makers. These revolve around issues of generalisability, which is inhibited most by a lack of trained observers and access to CT scanners, and a paucity of data relating to cost-effectiveness. Whether offering CT colonography as an alternative to competing strategies will genuinely enhance compliance also needs further and more detailed attention.

Adenoma↗
PubMed2006

CT colonography: automated measurement of colonic polyps compared with manual techniques--human in vitro study.

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.

Adolescent↗
PubMed2006

Computer assisted detection software for CT colonography: effect of sphericity filter on performance characteristics for patients with and without fecal tagging.

The aim of this study is to investigate the effect of changing sphericity filter values on performance of a computer assisted detection (CAD) system for CT colonography for data with and without fecal tagging. Colonography data from 138 patients with 317 validated polyps were divided into those with (86) and without (52) fecal tagging. Polyp coordinates were established by three observers and datasets analysed subsequently by a proprietary CAD system used at four discrete sphericity filter settings. Prompts were compared with the known coordinates in order to determine sensitivity and specificity. Sensitivity was highest at low sphericity; of 164 polyps 6 mm or more, 144 (87.8%) were detected at sphericity 0.3, and 132 (80.1%) at sphericity 0.9. Of 42 polyps measuring 10 mm or more, 40 (95.2%) were detected at sphericity 0.3, and 36 (85.7%) at sphericity 0.9. There was no significant difference in sensitivity for tagged and un-tagged data but specificity was reduced in tagged data at low sphericity and significantly reduced in untagged data at high sphericity. CAD had a sensitivity of 95.2% for polyps measuring 1 cm or more and 87.8% for polyps 6 mm or more when used at a sphericity setting of 0.3. Higher sphericity settings increased specificity while reducing sensitivity. The bowel preparation used significantly impacts on specificity.

Barium Sulfate↗
PubMed2006

Computed tomographic colonography: assessment of radiologist performance with and without computer-aided detection.

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.

Adenoma↗
PubMed2006

Reader error during CT colonography: causes and implications for training.

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.

Clinical Competence↗
PubMed2006

Potentially serious adverse events at CT colonography in symptomatic patients: national survey of the United Kingdom.

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.

Colonography, Computed Tomographic↗
PubMed2006

Polyp detection with CT colonography: primary 3D endoluminal analysis versus primary 2D transverse analysis with computer-assisted reader software.

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.

Aged↗
PubMed2006

Colonic polyps: effect of attenuation of tagged fluid and viewing window on conspicuity and measurement--in vitro experiment with porcine colonic specimen.

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.

Animals↗
PubMed2006

Automated insufflation of carbon dioxide for MDCT colonography: distension and patient experience compared with manual insufflation.

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.

Aged↗
PubMed2006

Computer-assisted reader software versus expert reviewers for polyp detection on CT colonography.

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.

Adult↗
PubMed2005

Virtual colonoscopy: current status and future directions.

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.

Cathartics↗
PubMed2005

CT colonography in the detection of colorectal polyps and cancer: systematic review, meta-analysis, and proposed minimum data set for study level reporting.

PURPOSE: To assess the methodologic quality of available data in published reports of computed tomographic (CT) colonography by performing systematic review and meta-analysis. MATERIALS AND METHODS: The MEDLINE database was searched for colonography reports published between 1994 and 2003, without language restriction. The terms colonography, colography, CT colonoscopy, CT pneumocolon, virtual colonoscopy, and virtual endoscopy were used. Studies were selected if the focus was detection of colorectal polyps verified with within-subject reference colonoscopy by using key methodologic criteria based on information presented at the Fourth International Symposium on Virtual Colonoscopy (Boston, Mass). Two reviewers independently abstracted methodologic characteristics. Per-patient and per-polyp detection rates were extracted, and authors were contacted, when necessary. Per-patient sensitivity and specificity were calculated for different lesion size categories, and Forest plots were produced. Meta-analysis of paired sensitivity and specificity was conducted by using a hierarchical model that enabled estimation of summary receiver operating characteristic curves allowing for variation in diagnostic threshold, and the average operating point was calculated. Per-polyp sensitivity was also calculated. RESULTS: Of 1398 studies considered for inclusion, 24 met our criteria. There were 4181 patients with a study prevalence of abnormality of 15%-72%. Meta-analysis of 2610 patients, 206 of whom had large polyps, showed high per-patient average sensitivity (93%; 95% confidence interval [CI]: 73%, 98%) and specificity (97%; 95% CI: 95%, 99%) for colonography; sensitivity and specificity decreased to 86% (95% CI: 75%, 93%) and 86% (95% CI: 76%, 93%), respectively, when the threshold was lowered to include medium polyps. When polyps of all sizes were included, studies were too heterogeneous in sensitivity (range, 45%-97%) and specificity (range, 26%-97%) to allow meaningful meta-analysis. Of 150 cancers, 144 were detected (sensitivity, 95.9%; 95% CI: 91.4%, 98.5%). Data reporting was frequently incomplete, with no generally accepted format. CONCLUSION: CT colonography seems sufficiently sensitive and specific in the detection of large and medium polyps; it is especially sensitive in the detection of symptomatic cancer. Studies are poorly reported, however, and the authors propose a minimum data set for study reporting.

Colonic Polyps↗
PubMed2004

CT colonography: effect of experience and training on reader performance.

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.

Clinical Competence↗
PubMed2003

Optimizing colonic distention for multi-detector row CT colonography: effect of hyoscine butylbromide and rectal balloon catheter.

PURPOSE: To investigate the effects of hyoscine butylbromide and an inflatable rectal balloon catheter on luminal distention during computed tomographic (CT) colonography. MATERIALS AND METHODS: One hundred thirty-six subjects undergoing CT colonography were randomized to receive either 20 mg or 40 mg of hyoscine butylbromide or no spasmolytic. Subjects were also independently randomized to undergo CT colonography with an inflatable rectal balloon catheter or a standard thin rectal tube. Multi-detector row CT colonography was performed with patients in prone and supine positions, with colonic segmental distention assessed by a single observer with a four-point scale. A simple assessment of whether distention was adequate for clinical interpretation was also made, and the effect of hyoscine butylbromide and catheter use was examined by using multivariate ordered logistic regression. RESULTS: Administration of hyoscine butylbromide was associated with significantly improved cecal (P =.05), ascending (P =.001), and transverse (P <.001) colonic distention when patients were supine and improved ascending (P <.001) and descending (P <.001) colonic distention when patients were prone. Compared with control subjects, patients given a spasmolytic had odds of 6.49 for clinically adequate distention throughout all colonic segments (P =.001). There was no incremental advantage with use of a 40-mg dose. In contrast, rectal balloon catheter use was not significantly associated with improved distention. CONCLUSION: Hyoscine butylbromide improves colonic distention during CT colonography and should be routinely administered where it is available. Use of a thin rectal tube for insufflation is adequate.

Adult↗
PubMed2003

Pilonidal sinus disease: MR imaging distinction from fistula in ano.

PURPOSE: To describe magnetic resonance (MR) imaging features in patients with proved pilonidal sinus disease and to compare these features with those in a matched group of patients with proved fistula in ano to determine the accuracy with which MR imaging can be used to distinguish between the two diseases. MATERIALS AND METHODS: Seven patients with pilonidal sinus disease underwent MR imaging with a body coil. The site and morphology of sepsis were noted, with particular reference to natal cleft sepsis and deep-seated sepsis, including intersphincteric anal canal sepsis and any enteric communication. Comparison was made with 14 age- and sex-matched patients with fistula in ano. Categoric frequencies were compared to calculate differences between the groups and sensitivities, specificities, and predictive values. RESULTS: All patients with pilonidal sinus had natal cleft sepsis, but five (71%) had sepsis at deep-seated sites more characteristic of fistula in ano. Eight patients with fistula in ano (57%) had natal cleft sepsis that was thought characteristic of pilonidal sinus. No patient with pilonidal sinus had intersphincteric sepsis or an enteric communication, in contrast to all patients with fistula in ano having both (P <.001). Natal cleft sepsis reached the subcutaneous tissues overlying the coccyx and sacrum in only one patient with fistula (7%), in contrast to six (86%) with pilonidal sinus (P <.001). MR imaging had a sensitivity of 86% (six of seven), specificity of 100% (14 of 14), positive predictive value of 100% (six of six), and negative predictive value of 93% (14 of 15) for diagnosis of pilonidal sinus disease. CONCLUSION: MR imaging features of perianal and deep-seated sepsis, characteristic of fistula in ano, are also found in patients with pilonidal sinus, but the absence of intersphincteric sepsis or enteric opening allows reliable MR imaging distinction between the two.

Adolescent↗
PubMed2003

Multi-detector row CT colonography: effect of collimation, pitch, and orientation on polyp detection in a human colectomy specimen.

PURPOSE: To investigate the effects of orientation, collimation, pitch, and tube current setting on polyp detection at multi-detector row computed tomographic (CT) colonography and to determine the optimal combination of scanning parameters for screening. MATERIALS AND METHODS: A colectomy specimen containing 117 polyps of different sizes was insufflated and imaged with a multi-detector row CT scanner at various collimation (1.25 and 2.5 mm), pitch (3 and 6), and tube current (50, 100, and 150 mA) settings. Two-dimensional multiplanar reformatted images and three-dimensional endoluminal surface renderings from the 12 resultant data sets were examined by one observer for the presence and conspicuity of polyps. The results were analyzed with Poisson regression and logistic regression to determine the effects of scanning parameters and of specimen orientation on polyp detection. RESULTS: The percentage of polyps that were detected significantly increased when collimation (P =.008) and table feed (P =.03) were decreased. Increased tube current resulted in improved detection only of polyps with a diameter of less than 5 mm. Polyps of less than 5 mm were optimally depicted with a collimation of 1.25 mm, a pitch of 3, and a tube current setting of 150 mA; polyps with a diameter greater than 5 mm were adequately depicted with 1.25-mm collimation and with either pitch setting and any of the three tube current settings. Small polyps in the transverse segment (positioned at a 90 degrees angle to the z axis of scanning) were significantly less visible than those in parallel or oblique orientations (P <.001). The effective radiation dose, calculated with a Monte Carlo simulation, was 1.4-10.0 mSv. CONCLUSION: Detection of small polyps (<5 mm) with multi-detector row CT is highly dependent on collimation, pitch, and, to a lesser extent, tube current. Collimation of 1.25 mm, combined with pitch of 6 and tube current of 50 mA, provides for reliable detection of polyps 5 mm or larger while limiting the effective radiation dose. Polyps smaller than 5 mm, however, may be poorly depicted with use of these settings in the transverse colon.

Colon↗