Natural History of Colorectal Polyps Undergoing Longitudinal in Vivo CT Colonography Surveillance.

Background The natural history of colorectal polyps is not well characterized due to clinical standards of care and other practical constraints limiting in vivo longitudinal surveillance. Established CT colonography (CTC) clinical screening protocols allow surveillance of small (6-9 mm) polyps. Purpose To assess the natural history of colorectal polyps followed with CTC in a clinical screening program, with histopathologic correlation for resected polyps. Materials and Methods In this retrospective study, CTC was used to longitudinally monitor small colorectal polyps in asymptomatic adult patients from April 1, 2004, to August 31, 2020. All patients underwent at least two CTC examinations. Polyp growth patterns across multiple time points were analyzed, with histopathologic context for resected polyps. Regression analysis was performed to evaluate predictors of advanced histopathology. Results In this study of 475 asymptomatic adult patients (mean age, 56.9 years ± 6.7 [SD]; 263 men), 639 unique polyps (mean initial diameter, 6.3 mm; volume, 50.2 mm3) were followed for a mean of 5.1 years ± 2.9. Of these 639 polyps, 398 (62.3%) underwent resection and histopathologic evaluation, and 41 (6.4%) proved to be histopathologically advanced (adenocarcinoma, high-grade dysplasia, or villous content), including two cancers and 38 tubulovillous adenomas. Advanced polyps showed mean volume growth of +178% per year (752% per year for adenocarcinomas) compared with +33% per year for nonadvanced polyps and -3% per year for unresected, unretrieved, or resolved polyps (P < .001). In addition, 90% of histologically advanced polyps achieved a volume of 100 mm3 and/or volume growth rate of 100% per year, compared with 29% of nonadvanced and 16% of unresected or resolved polyps (P < .001). Polyp volume-to-diameter ratio was also significantly greater for advanced polyps. For polyps observed at three or more time points, most advanced polyps demonstrated an initial slower growth interval, followed by a period of more rapid growth. Conclusion Small colorectal polyps ultimately proving to be histopathologically advanced neoplasms demonstrated substantially faster growth and attained greater overall size compared with nonadvanced polyps. Clinical trial registration no. NCT00204867 © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Dachman in this issue.

CT Colonography Reporting and Data System (C-RADS): Version 2023 Update.

The CT Colonography Reporting and Data System (C-RADS) has withstood the test of time and proven to be a robust classification scheme for CT colonography (CTC) findings. C-RADS version 2023 represents an update on the scheme used for colorectal and extracolonic findings at CTC. The update provides useful insights gained since the implementation of the original system in 2005. Increased experience has demonstrated confusion on how to classify the mass-like appearance of the colon consisting of soft tissue attenuation that occurs in segments with acute or chronic diverticulitis. Therefore, the update introduces a new subcategory, C2b, specifically for mass-like diverticular strictures, which are likely benign. Additionally, the update simplifies extracolonic classification by combining E1 and E2 categories into an updated extracolonic category of E1/E2 since, irrespective of whether a finding is considered a normal variant (category E1) or an otherwise clinically unimportant finding (category E2), no additional follow-up is required. This simplifies and streamlines the classification into one category, which results in the same management recommendation.

Artificial intelligence tool detection of intravenous contrast enhancement using spleen attenuation.

PURPOSE: To assess the ability of an automated AI tool to detect intravenous contrast material (IVCM) in abdominal CT examinations using spleen attenuation. METHODS: A previously validated automated AI tool measuring the attenuation of the spleen was deployed on a sample of 32,994 adult (age ≥ 18) patients (mean age, 61.9 ± 14.7 years; 13,869 men, 19,125 women) undergoing 65,449 supine position CT examinations (41,020 with and 24,429 without IVCM by DICOM header) from January 1, 2000 to December 31, 2021. After exclusions, receiver operating characteristic (ROC) curve analysis was performed to determine the optimal threshold for binary classification of IVCM status (non-contrast vs IVCM enhanced), which was then applied to the sample. Discordant examinations (i.e., IVCM status determined by AI tool did not match DICOM header) were manually reviewed to establish ground truth. Repeat ROC curve and contingency table analysis were performed to assess AI tool performance. RESULTS: ROC analysis of the initial study sample of 61,783 CT examinations yielded AUC of 0.970 with Youden index suggesting an optimal spleen attenuation threshold of 65 Hounsfield units (HU). Manual review of 2094 discordant CT examinations revealed discordance due to DICOM header error in 1278 (61.0%) and AI tool misclassification in 410 (19.6%), with 406 (9.4%) meeting exclusion criteria. Analysis of 61,377 CT examinations in the final study sample yielded AUC of 0.999 with accuracy of 99.3% at the 65 HU threshold. Error rate for DICOM header information was 2.1% (1278/61,377) versus 0.7% (410/61,377) for the AI tool. CONCLUSION: The automated spleen attenuation AI tool was highly accurate for detection of IVCM at a threshold of 65 HU.

Growth rates and histopathological outcomes of small (6-9 mm) colorectal polyps based on CT colonography surveillance and endoscopic removal.

BACKGROUND AND AIMS: The natural history of small polyps is not well established and rests on limited evidence from barium enema studies decades ago. Patients with one or two small polyps (6-9 mm) at screening CT colonography (CTC) are offered CTC surveillance at 3 years but may elect immediate colonoscopy. This practice allows direct observation of the growth of subcentimetre polyps, with histopathological correlation in patients undergoing subsequent polypectomy. DESIGN: Of 11 165 asymptomatic patients screened by CTC over a period of 16.4 years, 1067 had one or two 6-9 mm polyps detected (with no polyps ≥10 mm). Of these, 314 (mean age, 57.4 years; M:F, 141:173; 375 total polyps) elected immediate colonoscopic polypectomy, and 382 (mean age 57.0 years; M:F, 217:165; 481 total polyps) elected CTC surveillance over a mean of 4.7 years. Volumetric polyp growth was analysed, with histopathological correlation for resected polyps. Polyp growth and regression were defined as volume change of ±20% per year, with rapid growth defined as +100% per year (annual volume doubling). Regression analysis was performed to evaluate predictors of advanced histology, defined as the presence of cancer, high-grade dysplasia (HGD) or villous components. RESULTS: Of the 314 patients who underwent immediate polypectomy, 67.8% (213/314) harboured adenomas, 2.2% (7/314) with advanced histology; no polyps contained cancer or HGD. Of 382 patients who underwent CTC surveillance, 24.9% (95/382) had polyps that grew, while 62.0% (237/382) remained stable and 13.1% (50/382) regressed in size. Of the 58.6% (224/382) CTC surveillance patients who ultimately underwent colonoscopic resection, 87.1% (195/224) harboured adenomas, 12.9% (29/224) with advanced histology. Of CTC surveillance patients with growing polyps who underwent resection, 23.2% (19/82) harboured advanced histology vs 7.0% (10/142) with stable or regressing polyps (OR: 4.0; p<0.001), with even greater risk of advanced histology in those with rapid growth (63.6%, 14/22, OR: 25.4; p<0.001). Polyp growth, but not patient age/sex or polyp morphology/location were significant predictors of advanced histology. CONCLUSION: Small 6-9 mm polyps present overall low risk to patients, with polyp growth strongly associated with higher risk lesions. Most patients (75%) with small 6-9 mm polyps will see polyp stability or regression, with advanced histology seen in only 7%. The minority of patients (25%) with small polyps that do grow have a 3-fold increased risk of advanced histology.

Technical Adequacy of Fully Automated Artificial Intelligence Body Composition Tools: Assessment in a Heterogeneous Sample of External CT Examinations.

BACKGROUND. Clinically usable artificial intelligence (AI) tools analyzing imaging studies should be robust to expected variations in study parameters. OBJECTIVE. The purposes of this study were to assess the technical adequacy of a set of automated AI abdominal CT body composition tools in a heterogeneous sample of external CT examinations performed outside of the authors' hospital system and to explore possible causes of tool failure. METHODS. This retrospective study included 8949 patients (4256 men, 4693 women; mean age, 55.5 ± 15.9 years) who underwent 11,699 abdominal CT examinations performed at 777 unique external institutions with 83 unique scanner models from six manufacturers with images subsequently transferred to the local PACS for clinical purposes. Three independent automated AI tools were deployed to assess body composition (bone attenuation, amount and attenuation of muscle, amount of visceral and sub-cutaneous fat). One axial series per examination was evaluated. Technical adequacy was defined as tool output values within empirically derived reference ranges. Failures (i.e., tool output outside of reference range) were reviewed to identify possible causes. RESULTS. All three tools were technically adequate in 11,431 of 11,699 (97.7%) examinations. At least one tool failed in 268 (2.3%) of the examinations. Individual adequacy rates were 97.8% for the bone tool, 99.1% for the muscle tool, and 98.9% for the fat tool. A single type of image processing error (anisometry error, due to incorrect DICOM header voxel dimension information) accounted for 81 of 92 (88.0%) examinations in which all three tools failed, and all three tools failed whenever this error occurred. Anisometry error was the most common specific cause of failure of all tools (bone, 31.6%; muscle, 81.0%; fat, 62.8%). A total of 79 of 81 (97.5%) anisometry errors occurred on scanners from a single manufacturer; 80 of 81 (98.8%) occurred on the same scanner model. No cause of failure was identified for 59.4% of failures of the bone tool, 16.0% of failures of the muscle tool, or 34.9% of failures of the fat tool. CONCLUSION. The automated AI body composition tools had high technical adequacy rates in a heterogeneous sample of external CT examinations, supporting the generalizability of the tools and their potential for broad use. CLINICAL IMPACT. Certain causes of AI tool failure related to technical factors may be largely preventable through use of proper acquisition and reconstruction protocols.

Positive oral contrast material for CT evaluation of non-traumatic abdominal pain in the ED: prospective assessment of diagnostic confidence and throughput metrics.

OBJECTIVE: Evaluate the impact of positive oral contrast material (POCM) for non-traumatic abdominal pain on diagnostic confidence, diagnostic rate, and ED throughput. MATERIALS AND METHODS: ED oral contrast guidelines were changed to limit use of POCM. A total of 2,690 abdominopelvic CT exams performed for non-traumatic abdominal pain were prospectively evaluated for diagnostic confidence (5-point scale at 20% increments; 5 = 80-100% confidence) during a 24-month period. Impact on ED metrics including time from CT order to exam, preliminary read, ED length of stay (LOS), and repeat CT scan within 7 days was assessed. A subset of cases (n = 729) was evaluated for diagnostic rate. Data were collected at 2 time points, 6 and 24 months following the change. RESULTS: A total of 38 reviewers were participated (28 trainees, 10 staff). 1238 exams (46%) were done with POCM, 1452 (54%) were performed without POCM. For examinations with POCM, 80% of exams received a diagnostic confidence score of 5 (mean, 4.78 ± 0.43; 99% ≥ 4), whereas 60% of exams without POCM received a score of 5 (mean, 4.51 ± 0.70; 92% ≥ 4; p < .001). Trainees scored 1,523 exams (57%, 722 + POCM, 801 -POCM) and showed even lower diagnostic confidence in cases without PCOM compared with faculty (mean, 4.43 ± 0.68 vs. 4.59 ± 0.71; p < 0.001). Diagnostic rate in a randomly selected subset of exams (n = 729) was 54.2% in the POCM group versus 56.1% without POCM (p < 0.655). CT order to exam time decreased by 31 min, order to preliminary read decreased by 33 min, and ED LOS decreased by 30 min (approximately 8% of total LOS) in the group without POCM compared to those with POCM (p < 0.001 for all). 205 patients had a repeat scan within 7 days, 74 (36%) had IV contrast only, 131 (64%) had both IV and oral contrast on initial exam. Findings were consistent both over a 6-month evaluation period as well as the full 24-month study period. CONCLUSION: Limiting use of POCM in the ED for non-traumatic abdominal pain improved ED throughput but impaired diagnostic confidence, particularly in trainees; however, it did not significantly impact diagnostic rates nor proportion of repeat CT exams.

Positive Oral Contrast Solution at MDCT for Suspected Acute Appendicitis in Adults: Rate of Appendiceal Luminal Filling of Normal and Inflamed Appendixes.

OBJECTIVE. The purpose of this study was to assess the rate of appendiceal filling with a positive oral contrast solution at MDCT performed for suspected acute appendicitis in adults. MATERIALS AND METHODS. We performed a retrospective review of MDCT in 684 consecutive adult patients with suspected acute appendicitis in a 19-month period. Patients were excluded if no positive oral contrast solution (500 mL each of water and polyethylene glycol and 30 mL diatrizoate) was given or if the appendix was not visible or absent. After exclusion, images of 519 patients (mean age ± SD, 37.4 ± 16.0 years; 335 women, 184 men) were reviewed for cecal contrast opacification and appendiceal filling. Imaging findings were recorded as positive or negative for acute appendicitis using all available clinical and pathologic data as a reference standard. A control series of CT colonography (CTC) screening examinations (overnight preparation with universal cecal opacification) in 2552 adults without symptoms of appendicitis was also reviewed. RESULTS. Cecal opacification was confirmed in 313/519 (60.3%) patients, with no difference between those considered to be positive (68/107, 63.6%) or negative (245/412, 59.5%) for appendicitis (p = 0.506). When positive oral contrast solution reached the cecum, appendiceal filling was seen in none of the 68 (0%) with appendicitis and in 205 of the 245 (83.7%) without appendicitis (p < 0.0001). Among CTC control subjects, appendiceal filling was similar to the cohort considered to be without appendicitis (2240/2552 [87.8%], p = 0.070). CONCLUSION. In MDCT for suspected acute appendicitis, luminal filling of the noninflamed appendix exceeds 80% when positive oral contrast solution reaches the cecum, indicating results similar to screening CTC. The appendix did not fill in proven acute appendicitis, indicating appendiceal filling may allow exclusion of appendicitis with high certainty. These results suggest positive oral contrast solution may augment diagnostic accuracy and confidence in cases of suspected acute appendicitis.

Clinical Implementation of a Focused MRI Protocol for Hepatic Fat and Iron Quantification.

OBJECTIVE. The purpose of this article is to describe our institutional experience with the clinical implementation of a novel focused rapid chemical shift-encoded MRI protocol specifically intended to detect and quantify hepatic steatosis and iron overload, highlighting usage statistics and issues related to cost. CONCLUSION. Focused MRI examinations for specific clinical indications, such as this protocol for detection and quantification of hepatic steatosis and iron overload, are feasible in a busy clinical practice and add value for patients and referring providers.

Volumetric Textural Analysis of Colorectal Masses at CT Colonography: Differentiating Benign versus Malignant Pathology and Comparison with Human Reader Performance.

RATIONALE AND OBJECTIVES: To (1) apply a quantitative volumetric textural analysis (VTA) to colorectal masses at CT colonography (CTC) for the differentiation of malignant and benign lesions and to (2) compare VTA with human performance. MATERIALS AND METHODS: A validated, quantitative VTA method was applied to 63 pathologically proven colorectal masses (mean size, 4.2 cm; range, 3-8 cm) at noncontrast CTC in 59 adults (mean age, 66.5 years; range, 45.9-91.6 years). Fifty-one percent (32/63) of the masses were invasive adenocarcinoma, and the remaining 49% (31/63) were large benign adenomas. Three readers with CTC experience independently assessed the likelihood of malignancy using a 5-point scale (1 = definitely benign, 2 = probably benign, 3 = indeterminate, 4 = probably malignant, 5 = definitely malignant). Areas under the curve (AUCs) and accuracy levels were compared. RESULTS: VTA achieved optimal sensitivity of 83.6% vs 91.7% for human readers (P = .034), with specificities of 87.5% and 77.4%, respectively (P = .007). No significant difference in overall accuracy was seen between VTA and human readers (85.5% vs 84.7%, P = .753). The AUC for differentiating benign and malignant lesions was 0.936 for VTA and 0.917 for human readers. Intraclass correlation coefficient among the human readers was 0.76, indicating good to excellent agreement. CONCLUSION: VTA demonstrates excellent performance for distinguishing benign from malignant colorectal masses (≥3 cm) at CTC, comparable yet potentially complementary to experienced human performance.

Monitoring Fatty Liver Disease with MRI Following Bariatric Surgery: A Prospective, Dual-Center Study.

Purpose To longitudinally monitor liver fat before and after bariatric surgery by using quantitative chemical shift-encoded (CSE) MRI and to compare with changes in body mass index (BMI), weight, and waist circumference (WC). Materials and Methods For this prospective study, which was approved by the internal review board, a total of 126 participants with obesity who were undergoing evaluation for bariatric surgery with preoperative very low calorie diet (VLCD) were recruited from June 27, 2010, through May 5, 2015. Written informed consent was obtained from all participants. Participants underwent CSE MRI measuring liver proton density fat fraction (PDFF) before VLCD (2-3 weeks before surgery), after VLCD (1-3 days before surgery), and 1, 3, and 6-10 months following surgery. Linear regression was used to estimate rates of change of PDFF (ΔPDFF) and body anthropometrics. Initial PDFF (PDFF0), initial anthropometrics, and anthropometric rates of change were evaluated as predictors of ΔPDFF. Mixed-effects regression was used to estimate time to normalization of PDFF. Results Fifty participants (mean age, 51.0 years; age range, 27-70 years), including 43 women (mean age, 50.8 years; age range, 27-70 years) and seven men (mean age, 51.7 years; age range, 36-62 years), with mean PDFF0 ± standard deviation of 18.1% ± 8.6 and mean BMI0 of 44.9 kg/m2 ± 6.5 completed the study. By 6-10 months following surgery, mean PDFF decreased to 4.9% ± 3.4 and mean BMI decreased to 34.5 kg/m2 ± 5.4. Mean estimated time to PDFF normalization was 22.5 weeks ± 11.5. PDFF0 was the only strong predictor for both ΔPDFF and time to PDFF normalization. No body anthropometric correlated with either outcome. Conclusion Average liver proton density fat fraction (PDFF) decreased to normal (< 5%) by 6-10 months following surgery, with mean time to normalization of approximately 5 months. Initial PDFF was a strong predictor of both rate of change of PDFF and time to normalization. Body anthropometrics did not predict either outcome. Online supplemental material is available for this article. © RSNA, 2018.

Opportunistic Screening for Hereditary Hemochromatosis With Unenhanced CT: Determination of an Optimal Liver Attenuation Threshold.

OBJECTIVE: The purpose of this study was to assess whether a specific liver attenuation threshold for unenhanced CT allows both sensitive opportunistic detection of unsuspected hereditary hemochromatosis and low overall screening test-positive rates. MATERIALS AND METHODS: We used a standard ROI placement method on unenhanced CT studies of 3357 consecutive adults (mean age, 57.0 years) with no symptoms of liver disease who underwent colorectal screening. Hepatic attenuation (in HU) was measured to assess test-positive rates at various liver attenuation thresholds. To assess sensitivity, unenhanced hepatic CT attenuation was also measured in 12 patients with hereditary hemochromatosis (mean age, 48.3 years), who were homozygous for the HFE C282Y mutation. All scans were obtained at 120 kV. Serum ferritin levels were recorded for the hereditary hemochromatosis cohort. RESULTS: Mean liver attenuation ± SD among screened adults was 59.4 ± 12.7 HU, compared with 78.7 ± 13.1 HU (range, 59-105 HU) in the hereditary hemochromatosis cohort (p < 0.001). Screening test-positive rates were 30.6% (n = 1028) at 65 HU, 8.2% (n = 275) at 70 HU, 1.2% (n = 39) at 75 HU, and 0.2% (n = 7) at 80 HU. Corresponding sensitivities for hereditary hemochromatosis at these thresholds were 83.3% (10/12) at 65, 70, and 75 HU; and 50.0% (6/12) at 80 HU. Serum ferritin levels were elevated in all patients with hereditary hemochromatosis (mean, 1678 ng/mL; range, 477-3991 ng/mL). CONCLUSION: An unenhanced CT liver attenuation threshold of 75 HU was sensitive (83.3%) for hereditary hemochromatosis while maintaining an acceptably low screening test-positive rate (1.2%). An unexplained liver attenuation of 75 HU or more on unenhanced CT should trigger appropriate laboratory investigation for iron overload; early intervention with phlebotomy can limit or prevent organ damage in patients with hemochromatosis.

Validation of a motion-robust 2D sequential technique for quantification of hepatic proton density fat fraction during free breathing.

BACKGROUND: Current chemical-shift-encoded (CSE) MRI techniques for measuring hepatic proton density fat fraction (PDFF) are sensitive to motion artifacts. PURPOSE: Initial validation of a motion-robust 2D-sequential CSE-MRI technique for quantification of hepatic PDFF. STUDY TYPE: Phantom study and prospective in vivo cohort. POPULATION: Fifty adult patients (27 women, 23 men, mean age 57.2 years). FIELD STRENGTH/SEQUENCE: 3D, 2D-interleaved, and 2D-sequential CSE-MRI acquisitions at 1.5T. ASSESSMENT: Three CSE-MRI techniques (3D, 2D-interleaved, 2D-sequential) were performed in a PDFF phantom and in vivo. Reference standards were 3D CSE-MRI PDFF measurements for the phantom study and single-voxel MR spectroscopy hepatic PDFF measurements (MRS-PDFF) in vivo. In vivo hepatic MRI-PDFF measurements were performed during a single breath-hold (BH) and free breathing (FB), and were repeated by a second reader for the FB 2D-sequential sequence to assess interreader variability. STATISTICAL TESTS: Correlation plots to validate the 2D-sequential CSE-MRI against the phantom and in vivo reference standards. Bland-Altman analysis of FB versus BH CSE-MRI acquisitions to evaluate robustness to motion. Bland-Altman analysis to assess interreader variability. RESULTS: Phantom 2D-sequential CSE-MRI PDFF measurements demonstrated excellent agreement and correlation (R2 > 0.99) with 3D CSE-MRI. In vivo, the mean (±SD) hepatic PDFF was 8.8 ± 8.7% (range 0.6-28.5%). Compared with BH acquisitions, FB hepatic PDFF measurements demonstrated bias of +0.15% for 2D-sequential compared with + 0.53% for 3D and +0.94% for 2D-interleaved. 95% limits of agreement (LOA) were narrower for 2D-sequential (±0.99%), compared with 3D (±3.72%) and 2D-interleaved (±3.10%). All CSE-MRI techniques had excellent correlation with MRS (R2 > 0.97). The FB 2D-sequential acquisition demonstrated little interreader variability, with mean bias of +0.07% and 95% LOA of ± 1.53%. DATA CONCLUSION: This motion-robust 2D-sequential CSE-MRI can accurately measure hepatic PDFF during free breathing in a patient population with a range of PDFF values of 0.6-28.5%, permitting accurate quantification of liver fat content without the need for suspended respiration. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;48:1578-1585.

Process improvement methodologies uncover unexpected gaps in stroke care.

Background The diagnosis and treatment of acute stroke requires timed and coordinated effort across multiple clinical teams. Purpose To analyze the frequency and temporal distribution of emergent stroke evaluations (ESEs) to identify potential contributory workflow factors that may delay the initiation and subsequent evaluation of emergency department stroke patients. Material and Methods A total of 719 sentinel ESEs with concurrent neuroimaging were identified over a 22-month retrospective time period. Frequency data were tabulated and odds ratios calculated. Results Of all ESEs, 5% occur between 01:00 and 07:00. ESEs were most frequent during the late morning and early afternoon hours (10:00-14:00). Unexpectedly, there was a statistically significant decline in the frequency of ESEs that occur at the 14:00 time point. Conclusion Temporal analysis of ESEs in the emergency department allowed us to identify an unexpected decrease in ESEs and through process improvement methodologies (Lean and Six Sigma) and identify potential workflow elements contributing to this observation.

Flat Serrated Polyps at CT Colonography: Relevance, Appearance, and Optimizing Interpretation.

Serrated polyps are a recently recognized family of colonic polyps with subgroups that harbor future malignant potential. In the past, the significance of these lesions to the colorectal cancer carcinogenesis pathway was not recognized nor well understood. It is now known that serrated polyps account for approximately one-fourth of all sporadic colorectal cancers. The sessile serrated polyp (SSP) (also known as a sessile serrated adenoma [SSA]) is the main lesion of interest given its prevalence and subtle presentation. These lesions are often flat-only minimally raised from the colonic surface-and occur in the right colon. These lesions have been a likely common cause of screening failure at colonoscopy, although detection has improved with improved recognition over time. Although detection is difficult with image-based screening, serrated lesions can be detected at CT colonography. The prevalence in CT colonography screening populations mirrors the rates at colonoscopy for similar size categories. CT colonography allows identification of SSPs despite their minimally raised profile owing to the phenomenon of lesional contrast material coating. This contrast material coat aids in lesion detection by highlighting the subtle morphologic changes as well as increasing confidence that a true lesion exists despite a flat morphology. It is important to optimize contrast material coating with specific bowel preparations and other technical parameters. Radiologists should be aware of these technical and interpretation issues. Armed with this knowledge, radiologists should expect excellent results in detection of these subtle but important lesions. ©RSNA, 2017.

Extracolonic Findings at Screening CT Colonography: Prevalence, Benefits, Challenges, and Opportunities.

OBJECTIVE: Extracolonic findings at screening CT colonography (CTC) represent imaging findings incidentally detected outside the colon and rectum. Confusion regarding rates reported in the literature fuels controversy over the relative benefits versus harms of extracolonic findings. CONCLUSION: From an evidence-based approach, this article reviews the prevalence and benefits of and challenges raised by extracolonic findings, as well as opportunities to further leverage the effect of screening CTC. The role of the radiologist in handling these lesions responsibly is emphasized.

CT Colonographic Screening of Patients With a Family History of Colorectal Cancer: Comparison With Adults at Average Risk and Implications for Guidelines.

OBJECTIVE: The purposes of this study were to compare rates of lesion detection at CT colonographic (CTC) screening of adults without symptoms who had and who did not have a family history of colorectal cancer according to American Cancer Society guidelines and to consider the clinical implications. MATERIALS AND METHODS: Over 134 months, consecutively registered CTC cohorts of adults without symptoms who had (n = 156; 88 [56.4%] women; 68 [43.6%] men; mean age, 56.3 years) and who did not have (n = 8857; 4757 [53.7%] women; 4100 [46.3%] men; mean age, 56.6 years) an American Cancer Society-defined family history of colorectal cancer (first-degree relative with diagnosis before age 60 years or two first-degree relatives with diagnosis at any age) were compared for relevant colorectal findings. RESULTS: For the family history versus no family history cohorts, the frequency of all nondiminutive polyps (≥ 6 mm) reported at CTC was 23.7% versus 15.5% (p = 0.007); small polyps (6-9 mm), 13.5% versus 9.1% (p = 0.068); and large polyps (≥ 10 mm), 10.2% versus 6.5% (p = 0.068). The rate of referral for colonoscopy was greater for the family history cohort (16.0% vs 10.5%; p = 0.035). However, the frequencies of proven advanced adenoma (4.5% vs 3.2%; p = 0.357), nonadvanced adenoma (5.1% vs 2.6%; p = 0.070), and cancer (0.0% vs 0.4%; p = 0.999) were not significantly increased. The difference in positive rates between the two cohorts (11.5% vs 4.3%; p < 0.001) was primarily due to nonneoplastic findings of no colorectal cancer relevance, such as small hyperplastic polyps, diverticular disease, and false-positive CTC findings. CONCLUSION: Although the overall CTC-positive and colonoscopy referral rates were higher in the family history cohort, the clinically relevant frequencies of advanced neoplasia and cancer were not sufficiently increased to preclude CTC screening. These findings support the use of CTC as a front-line screening option in adults with a family history of colorectal cancer.

Workflow Dynamics and the Imaging Value Chain: Quantifying the Effect of Designating a Nonimage-Interpretive Task Workflow.

PURPOSE: To assess the impact of separate non-image interpretive task and image-interpretive task workflows in an academic neuroradiology practice. MATERIALS AND METHODS: A prospective, randomized, observational investigation of a centralized academic neuroradiology reading room was performed. The primary reading room fellow was observed over a one-month period using a time-and-motion methodology, recording frequency and duration of tasks performed. Tasks were categorized into separate image interpretive and non-image interpretive workflows. Post-intervention observation of the primary fellow was repeated following the implementation of a consult assistant responsible for non-image interpretive tasks. Pre- and post-intervention data were compared. RESULTS: Following separation of image-interpretive and non-image interpretive workflows, time spent on image-interpretive tasks by the primary fellow increased from 53.8% to 73.2% while non-image interpretive tasks decreased from 20.4% to 4.4%. Mean time duration of image interpretation nearly doubled, from 05:44 to 11:01 (p = 0.002). Decreases in specific non-image interpretive tasks, including phone calls/paging (2.86/hr versus 0.80/hr), in-room consultations (1.36/hr versus 0.80/hr), and protocoling (0.99/hr versus 0.10/hr), were observed. The consult assistant experienced 29.4 task switching events per hour. Rates of specific non-image interpretive tasks for the CA were 6.41/hr for phone calls/paging, 3.60/hr for in-room consultations, and 3.83/hr for protocoling. CONCLUSION: Separating responsibilities into NIT and IIT workflows substantially increased image interpretation time and decreased TSEs for the primary fellow. Consolidation of NITs into a separate workflow may allow for more efficient task completion.

Subclonal diversity arises early even in small colorectal tumours and contributes to differential growth fates.

OBJECTIVE AND DESIGN: The goal of the study was to determine whether the mutational profile of early colorectal polyps correlated with growth behaviour. The growth of small polyps (6-9 mm) that were first identified during routine screening of patients was monitored over time by interval imaging with CT colonography. Mutations in these lesions with known growth rates were identified by targeted next-generation sequencing. The timing of mutational events was estimated using computer modelling and statistical inference considering several parameters including allele frequency and fitness. RESULTS: The mutational landscape of small polyps is varied both within individual polyps and among the group as a whole but no single alteration was correlated with growth behaviour. Polyps carried 0-3 pathogenic mutations with the most frequent being in APC, KRAS/NRAS, BRAF, FBXW7 and TP53. In polyps with two or more pathogenic mutations, allele frequencies were often variable, indicating the presence of multiple populations within a single tumour. Based on computer modelling, detectable mutations occurred at a mean polyp size of 30±35 crypts, well before the tumour is of a clinically detectable size. CONCLUSIONS: These data indicate that small colon polyps can have multiple pathogenic mutations in crucial driver genes that arise early in the existence of a tumour. Understanding the molecular pathway of tumourigenesis and clonal evolution in polyps that are at risk for progressing to invasive cancers will allow us to begin to better predict which polyps are more likely to progress into adenocarcinomas and which patients are at greater risk of developing advanced disease.

Colorectal Findings at Repeat CT Colonography Screening after Initial CT Colonography Screening Negative for Polyps Larger than 5 mm.

Purpose To determine the rate and types of polyps detected at repeat computed tomographic (CT) colonography screening after initial negative findings at CT colonography screening. Materials and Methods Among 5640 negative CT colonography screenings (no polyps ≥ 6 mm) performed before 2010 at one medical center, 1429 (25.3%; mean age, 61.4 years; 736 women, 693 men) patients have returned for repeat CT colonography screening (mean interval, 5.7 years ± 0.9; range, 4.5-10.7 years). Positive rates and histologic findings of initial and repeat screening were compared in this HIPAA-compliant, institutional review board-approved study. For all patients with positive findings at repeat CT colonography, the findings were directly compared against the initial CT colonography findings. Fisher exact, Pearson χ2, and Student t tests were applied as indicated. Results Repeat CT colonography screening was positive for lesions 6 mm or larger in 173 (12.1%) adults (compared with 14.3% at initial CT colonography screening, P = .29). In the 173 patients, 29.5% (61 of 207) of nondiminutive polyps could be identified as diminutive at the initial CT colonography and 12.6% (26 of 207) were missed. Large polyps, advanced neoplasia (advanced adenomas and cancer), and invasive cancer were seen in 3.8% (55 of 1429), 2.8% (40 of 1429), and 0.14% (two of 1429), respectively, at follow-up, compared with 5.2% (P = .02), 3.2% (P = .52), and 0.45% (P = .17), respectively, at initial screening. Of 42 advanced lesions in 40 follow-up screenings, 33 (78.6%) were right sided and 22 (52.4%) were flat, compared with 45.4% (P < .001) and 11.3% (P < .001), respectively, at initial screening. Large right-sided serrated lesions were confirmed in 20 individuals (1.4%), compared with 0.5% (P < .001) confirmed at initial screening. Conclusion Positive rates for large polyps at repeat CT colonography screening (3.7%) were lower compared with those at initial screening (5.2%). However, more advanced right-sided lesions were detected at follow-up CT colonography, many of which were flat, serrated lesions. The cumulative findings support both the nonreporting of diminutive lesions and a 5-10-year screening interval. © RSNA, 2016 An earlier incorrect version of this article appeared online. This article was corrected on August 30, 2016.