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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Prospective Evaluation of Reduced Dose Computed Tomography for the Detection of Low-Contrast Liver Lesions: Direct Comparison with Concurrent Standard Dose Imaging.

OBJECTIVES: To prospectively compare the diagnostic performance of reduced-dose (RD) contrast-enhanced CT (CECT) with standard-dose (SD) CECT for detection of low-contrast liver lesions. METHODS: Seventy adults with non-liver primary malignancies underwent abdominal SD-CECT immediately followed by RD-CECT, aggressively targeted at 60-70 % dose reduction. SD series were reconstructed using FBP. RD series were reconstructed with FBP, ASIR, and MBIR (Veo). Three readers-blinded to clinical history and comparison studies-reviewed all series, identifying liver lesions ≥4 mm. Non-blinded review by two experienced abdominal radiologists-assessing SD against available clinical and radiologic information-established the reference standard. RESULTS: RD-CECT mean effective dose was 2.01 ± 1.36 mSv (median, 1.71), a 64.1 ± 8.8 % reduction. Pooled per-patient performance data were (sensitivity/specificity/PPV/NPV/accuracy) 0.91/0.78/0.60/0.96/0.81 for SD-FBP compared with RD-FBP 0.79/0.75/0.54/0.91/0.76; RD-ASIR 0.84/0.75/0.56/0.93/0.78; and RD-MBIR 0.84/0.68/0.49/0.92/0.72. ROC AUC values were 0.896/0.834/0.858/0.854 for SD-FBP/RD-FBP/RD-ASIR/RD-MBIR, respectively. RD-FBP (P = 0.002) and RD-MBIR (P = 0.032) AUCs were significantly lower than those of SD-FBP; RD-ASIR was not (P = 0.052). Reader confidence was lower for all RD series (P < 0.001) compared with SD-FBP, especially when calling patients entirely negative. CONCLUSIONS: Aggressive CT dose reduction resulted in inferior diagnostic performance and reader confidence for detection of low-contrast liver lesions compared to SD. Relative to RD-ASIR, RD-FBP showed decreased sensitivity and RD-MBIR showed decreased specificity. KEY POINTS: • Reduced-dose CECT demonstrates inferior diagnostic performance for detecting low-contrast liver lesions. • Reader confidence is lower with reduced-dose CECT compared to standard-dose CECT. • Overly aggressive dose reduction may result in misdiagnosis, regardless of reconstruction algorithm. • Careful consideration of perceived risks versus benefits of dose reduction is crucial.

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.

Colorectal Polyps Missed with Optical Colonoscopy Despite Previous Detection and Localization with CT Colonography.

PURPOSE: To retrospectively evaluate and characterize nondiminutive colorectal polyps prospectively detected by using computed tomographic (CT) colonography but not confirmed with subsequent nonblinded optical colonoscopy (OC). MATERIALS AND METHODS: This study was institutional review board approved; the need for signed informed consent was waived. Over 113 months, 9336 adults (mean age, 57.1 years) underwent CT colonography, which yielded 2606 nondiminutive (≥6 mm) polyps. Of 1731 polyps that underwent subsequent nonblinded OC (ie, endoscopists provided advanced knowledge of specific polyp size, location, and morphologic appearance at CT colonography), 181 (10%) were not confirmed with initial endoscopy (ie, discordant), of which 37 were excluded (awaiting or lost to follow-up). After discordant polyp review, 66 of the 144 lesions were categorized as likely CT colonography false-positive findings (no further action) and 78 were categorized as potential OC false-negative (FN) findings. RESULTS: Thirty-one of 144 (21.5%) of all discordant lesions were confirmed as FN findings at OC, including 40% (31 of 78) of those with OC and/or CT colonography follow-up. OC FN lesions were an average of 8.5 mm ± 3.3 in diameter and were identified with higher confidence at prospective CT colonography (on a 3-point confidence scale: mean, 2.8 vs 2.3; P = .001). OC FN findings were more likely than concordant polyps to be located in the right colon (respectively, 71% [22 of 31] vs 47% [723 of 1535]; P = .010). Most (81% [21 of 26]) OC FN lesions that were ultimately resected were neoplastic (adenomas or serrated lesions), of which 43% (nine of 21) were characterized as advanced lesions, and 89% (eight of nine) of advanced lesions occurred in the right colon. CONCLUSION: In clinical practice, polyps prospectively identified with CT colonography but not confirmed with subsequent nonblinded (ie, despite a priori knowledge of the CT colonography findings) OC require additional review because a substantial proportion may be FN findings. Most FN findings found with OC demonstrated clinically significant histopathologic results, and a majority of advanced lesions occurred in the right colon.

Serrated Polyps at CT Colonography: Prevalence and Characteristics of the Serrated Polyp Spectrum.

Purpose To report the prevalence and characteristics of serrated polyps identified in a large, average-risk population undergoing screening computed tomographic (CT) colonography. Materials and Methods This HIPAA-compliant retrospective study was approved by the institutional review board of the University of Wisconsin School of Medicine and Public Health. The need for informed consent was waived. Nine thousand six hundred examinations from 8289 patients were enrolled in a single-institution CT colonography-based screening program (from 2004 to 2011) and were evaluated for the presence of nondiminutive serrated lesions and advanced adenomas. The prevalence and characteristics of these lesions were tabulated. Generalized estimating equation regressions of polyp characteristics that may contribute to visualization of serrated lesions were investigated, including polyp size, location, and morphologic appearance; histologic findings; and presence or absence of contrast material tagging. Results Nondiminutive serrated lesions (≥6 mm) were seen at CT colonography-based screening with a prevalence of 3.1% (254 of 8289 patients). Sessile serrated adenomas (SSAs) and traditional serrated adenomas (TSAs) constituted 36.8% (137 of 372) and 4.3% (16 of 372) of serrated lesions, respectively; hyperplastic polyps (HPs) accounted for 58.9% (219 of 372 lesions). SSA and TSA tended to be large (mean size, 10.6 mm and 14.1 mm, respectively), with size categories and polyp subgroups significantly associated (P < .0001). SSA tended to be proximal in location (91.2%, 125 of 137 lesions) and flat in morphologic appearance (39.4%, 54 of 137 lesions) compared with TSA and HP. The presence of high-grade dysplasia in serrated lesions was uncommon when compared with advanced adenomas (one of 372 lesions vs 22 of 395 lesions, respectively; P < .0001). Multivariate analysis showed that contrast material tagging markedly improved serrated polyp detection with an odds ratio of 40.4 (95% confidence interval: 10.1, 161.4). Conclusion Serrated lesions are seen at CT colonography-based screening with a nondiminutive prevalence of 3.1%. These lesions tend to be large, flat, and proximal in location. Adherent contrast material coating on these polyps aids in their detection, despite an often flat morphologic appearance. (©) RSNA, 2016 Online supplemental material is available for this article.

Potentially Important Extracolonic Findings at Screening CT Colonography: Incidence and Outcomes Data From a Clinical Screening Program.

OBJECTIVE: The effect of detection of extracolonic findings at screening CT colonography (CTC) remains controversial. Our objective is to analyze the incidence and outcomes of unsuspected potentially significant (CT Colonography Reporting and Data System [C-RADS] extracolonic category E4) findings in a population undergoing clinical CTC screening. SUBJECTS AND METHODS: Over the course of 99 months (April 1, 2004, through June 30, 2012), 7952 consecutive asymptomatic adults (3675 men and 4277 women; mean [± SD] age, 56.7 ± 7.3 years) underwent first-time screening CTC. Examinations were prospectively interpreted by radiologists within our abdominal imaging section, and extracolonic findings were recorded and categorized. Potentially significant (i.e., C-RADS extracolonic category E4) findings were retrospectively reviewed with additional analysis of follow-up (range, 2-10 years) and ultimate clinical outcome. RESULTS: Overall, 2.5% (202/7952) of patients had a potentially significant (C-RADS category E4) extracolonic finding for which further imaging (56%; 113/202) or clinical follow-up (44%; 89/202) was recommended. No patients had multiple category E4 findings. Twenty-two patients were lost to follow-up. Of the remaining 180 patients, 68% (123/180) proved to have clinically significant disease, including 23% (42/180) with malignant or potentially malignant neoplasms and 32% (57/180) with abdominal aortic or other visceral artery aneurysms requiring treatment or surveillance. The most commonly involved organs and systems included the vascular system (26%; 53/202), the genitourinary system (18%; 36/202), the liver (15%; 30/202), the gastrointestinal system (9.9%; 20/202), the lungs (9.4%; 19/202), and the gynecologic system (6.9%; 14/202). CONCLUSION: Potentially significant extracolonic findings in asymptomatic adults at screening CTC are uncommon (2-3% of cases). However, most of these findings (68%) will prove to be clinically significant, including a number of malignancies and aneurysms requiring treatment or surveillance.