Fat fraction and R2 * values of various liver masses: Initial experience with 6-point Dixon method on a 3T MRI system.

Purpose: To assess the feasibility of the 6-point Dixon method for evaluating liver masses. We also report our initial experience with the quantitative values in various liver masses on a 3T system. Materials and methods: Of 251 consecutive patients for whom 6-point Dixon was employed in abdominal magnetic resonance imaging scans between October 2020 and October 2021, 117 nodules in 117 patients with a mass diameter of more than 1 cm were included in the study. Images for measuring the proton density fat fraction (PDFF) and R2 * values were obtained using the iterative decomposition of water and fat with echo asymmetry and least-squares estimation-quantitative technique for liver imaging. Two radiologists independently measured PDFF (%) and R2 * (Hz). Inter-reader agreement and the differences between readers were examined using intra-class correlation coefficient (ICC) and the Bland-Altman method, respectively. PDFF and R2 * values in differentiating liver masses were examined. Results: The masses included hepatocellular carcinoma (n = 59), cyst (n = 20), metastasis (n = 14), hemangioma (n = 8), and others (n = 16). The ICCs for the region of interest (mm2), PDFF, and R2 * were 0.988 (95 % confidence interval (CI): 0.983, 0.992), 0.964 (95 % CI: 0.949, 0.975), and 0.962 (95 % CI: 0.941, 0.975), respectively. The differences of measurements between the readers showed that 5.1 % (6/117) and 6.0% (7/117) for PDFF and R2 * , respectively, were outside the 95 % CI. Conclusion: Our observation indicates that the 6-point Dixon method is applicable to liver masses.

Diagnostic Performance in Low- and High-Contrast Tasks of an Image-Based Denoising Algorithm Applied to Radiation Dose-Reduced Multiphase Abdominal CT Examinations.

BACKGROUND. Anatomic redundancy between phases can be used to achieve denoising of multiphase CT examinations. A limitation of iterative reconstruction (IR) techniques is that they generally require use of CT projection data. A frequency-split multi-band-filtration algorithm applies denoising to the multiphase CT images themselves. This method does not require knowledge of the acquisition process or integration into the reconstruction system of the scanner, and it can be implemented as a supplement to commercially available IR algorithms. OBJECTIVE. The purpose of the present study is to compare radiologists' performance for low-contrast and high-contrast diagnostic tasks (i.e., tasks for which differences in CT attenuation between the imaging target and its anatomic background are subtle or large, respectively) evaluated on multiphase abdominal CT between routine-dose images and radiation dose-reduced images processed by a frequency-split multiband-filtration denoising algorithm. METHODS. This retrospective single-center study included 47 patients who underwent multiphase contrast-enhanced CT for known or suspected liver metastases (a low-contrast task) and 45 patients who underwent multiphase contrast-enhanced CT for pancreatic cancer staging (a high-contrast task). Radiation dose-reduced images corresponding to dose reduction of 50% or more were created using a validated noise insertion technique and then underwent denoising using the frequency-split multi-band-filtration algorithm. Images were independently evaluated in multiple sessions by different groups of abdominal radiologists for each task (three readers in the low-contrast arm and four readers in the high-contrast arm). The noninferiority of denoised radiation dose-reduced images to routine-dose images was assessed using the jackknife alternative free-response ROC (JAFROC) figure-of-merit (FOM; limit of noninferiority, -0.10) for liver metastases detection and using the Cohen kappa statistic and reader confidence scores (100-point scale) for pancreatic cancer vascular invasion. RESULTS. For liver metastases detection, the JAFROC FOM for denoised radiation dose-reduced images was 0.644 (95% CI, 0.510-0.778), and that for routine-dose images was 0.668 (95% CI, 0.543-0.792; estimated difference, -0.024 [95% CI, -0.084 to 0.037]). Intraobserver agreement for pancreatic cancer vascular invasion was substantial to near perfect when the two image sets were compared (κ = 0.53-1.00); the 95% CIs of all differences in confidence scores between image sets contained zero. CONCLUSION. Multiphase contrast-enhanced abdominal CT images with a radiation dose reduction of 50% or greater that undergo denoising by a frequency-split multiband-filtration algorithm yield performance similar to that of routine-dose images for detection of liver metastases and vascular staging of pancreatic cancer. CLINICAL IMPACT. The image-based denoising algorithm facilitates radiation dose reduction of multiphase examinations for both low- and high-contrast diagnostic tasks without requiring manufacturer-specific hardware or software.

Mucinous cystic neoplasms of the liver with biliary prolapse.

OBJECTIVES: To describe the prevalence, clinical and radiological findings of biliary prolapse in pathologically proven mucinous cystic neoplasm of the liver (MCN-L). METHODS: Thirty-four patients, all female with median age 50 years (range, 14-82), with histologically confirmed MCN-L were enrolled. Median tumor size was 9 cm (range, 2-21 cm). Fifty-seven examinations (17 ultrasound, 25 CT, and 15 MR) among 34 MCN-Ls were reviewed. Two radiologists retrospectively assessed images for tumor location, size and other morphological features of the tumor, presence of biliary prolapse and upstream bile duct dilatation. Ultrasound, CT, and MR were assessed separately. Clinical features were evaluated. Clinical and radiological characteristics of MCN-L with and without biliary prolapse were compared. RESULTS: 15% (5/34) of MCN-Ls showed biliary prolapse confirmed at pathology. None of MCN-Ls were associated with invasive carcinoma. Patients with biliary prolapse were significantly younger than those without (median 27 years [22-56] vs. median 51 years [14-82], p = 0.03). MCN-Ls with biliary prolapse were significantly smaller than those without (median 6.4 cm [2.2-7.5] vs. median 9.6 cm [3.1-21], p = 0.01). The upstream bile duct was dilated more frequently in MCN-Ls with biliary prolapse (100% vs. 38%, p = 0.02). Jaundice was significantly more common in MCN-Ls with biliary prolapse (80 vs 3%, p = 0.0005). Other clinical or radiological features were not significantly different between two groups. CONCLUSIONS: Biliary prolapse was found in 15% of MCN-Ls. MCN-Ls with biliary prolapse were significantly smaller and were more commonly associated with upstream bile duct dilation and jaundice than those without biliary prolapse.

Eosinophilic Disorders of the Gastrointestinal Tract and Associated Abdominal Viscera: Imaging Findings and Diagnosis.

Eosinophilic gastrointestinal disorders (EGIDs) are inflammatory conditions of the gastrointestinal tract that are characterized by tissue eosinophilia and end-organ dysfunction or damage. Primary EGIDs are associated with atopy and other allergic conditions, whereas secondary EGIDs are associated with underlying systemic diseases or hypereosinophilic syndrome. Within the spectrum of EGIDs, eosinophilic esophagitis is the most prevalent. Eosinophilic gastroenteritis and eosinophilic colitis are relatively uncommon. Eosinophilic infiltration of the liver, biliary tree, and/or pancreas also can occur and mimic other inflammatory and malignant conditions. Although endoscopic evaluation is the method of choice for eosinophilic esophagitis, radiologic evaluation of the esophagus plays an important role in the assessment of disease severity. CT and MR enterography are the modalities of choice for demonstrating specific forms of eosinophilic gastroenteritis. CT and MRI are important in the detection of abdominal visceral involvement in EGIDs. Diagnosis is often challenging and relies on symptoms, imaging findings, histologic confirmation of tissue eosinophilia, and correlation with peripheral eosinophilia. Imaging is crucial for identifying characteristic organ-specific findings, although imaging findings are not specific. When promptly treated, EGIDs usually have a benign clinical course. However, a delayed diagnosis and associated surgical interventions have been associated with morbidity. Therefore, a radiologist's knowledge of the imaging findings of EGIDs in the appropriate clinical settings may aid in early diagnosis and thereby improve patient care. An overview of the clinical features and imaging findings of EGIDs and the eosinophilic disorders of associated abdominal viscera is provided. Online supplemental material is available for this article. ©RSNA, 2022.

Predicting Risk of Surgery in Patients With Small Bowel Crohn's Disease Strictures Using Computed Tomography and Magnetic Resonance Enterography.

BACKGROUND: We aimed to determine if patient symptoms and computed tomography enterography (CTE) and magnetic resonance enterography (MRE) imaging findings can be used to predict near-term risk of surgery in patients with small bowel Crohn's disease (CD). METHODS: CD patients with small bowel strictures undergoing serial CTE or MRE were retrospectively identified. Strictures were defined by luminal narrowing, bowel wall thickening, and unequivocal proximal small bowel dilation. Harvey-Bradshaw index (HBI) was recorded. Stricture observations and measurements were performed on baseline CTE or MRE and compared to with prior and subsequent scans. Patients were divided into those who underwent surgery within 2 years and those who did not. LASSO (least absolute shrinkage and selection operator) regression models were trained and validated using 5-fold cross-validation. RESULTS: Eighty-five patients (43.7 ± 15.3 years of age at baseline scan, majority male [57.6%]) had 137 small bowel strictures. Surgery was performed in 26 patients within 2 years from baseline CTE or MRE. In univariate analysis of patients with prior exams, development of stricture on the baseline exam was associated with near-term surgery (P = .006). A mathematical model using baseline features predicting surgery within 2 years included an HBI of 5 to 7 (odds ratio [OR], 1.7 × 105; P = .057), an HBI of 8 to 16 (OR, 3.1 × 105; P = .054), anastomotic stricture (OR, 0.002; P = .091), bowel wall thickness (OR, 4.7; P = .064), penetrating behavior (OR, 3.1 × 103; P = .096), and newly developed stricture (OR: 7.2 × 107; P = .062). This model demonstrated sensitivity of 67% and specificity of 73% (area under the curve, 0.62). CONCLUSIONS: CTE or MRE imaging findings in combination with HBI can potentially predict which patients will require surgery within 2 years.

Computed tomography and magnetic resonance enterography imaging measurements and observations, in combination with patient symptoms, can potentially predict which patients will require surgery within 2 years with modest degree of accuracy.

Deep-learning model observer for a low-contrast hepatic metastases localization task in computed tomography.

PURPOSE: Conventional model observers (MO) in CT are often limited to a uniform background or varying background that is random and can be modeled in an analytical form. It is unclear if these conventional MOs can be readily generalized to predict human observer performance in clinical CT tasks that involve realistic anatomical background. Deep-learning-based model observers (DL-MO) have recently been developed, but have not been validated for challenging low contrast diagnostic tasks in abdominal CT. We consequently sought to validate a DL-MO for a low-contrast hepatic metastases localization task. METHODS: We adapted our recently developed DL-MO framework for the liver metastases localization task. Our previously-validated projection-domain lesion-/noise-insertion techniques were used to synthesize realistic positive and low-dose abdominal CT exams, using the archived patient projection data. Ten experimental conditions were generated, which involved different lesion sizes/contrasts, radiation dose levels, and image reconstruction types. Each condition included 100 trials generated from a patient cohort of 7 cases. Each trial was presented as liver image patches (160×160×5 voxels). The DL-MO performance was calculated for each condition and was compared with human observer performance, which was obtained by three sub-specialized radiologists in an observer study. The performance of DL-MO and radiologists was gauged by the area under localization receiver-operating-characteristic curves. The generalization performance of the DL-MO was estimated with the repeated twofold cross-validation method over the same set of trials used in the human observer study. A multi-slice Channelized Hoteling Observers (CHO) was compared with the DL-MO across the same experimental conditions. RESULTS: The performance of DL-MO was highly correlated to that of radiologists (Pearson's correlation coefficient: 0.987; 95% CI: [0.942, 0.997]). The performance level of DL-MO was comparable to that of the grouped radiologists, that is, the mean performance difference was -3.3%. The CHO performance was poorer than the grouped radiologist performance, before internal noise could be added. The correlation between CHO and radiologists was weaker (Pearson's correlation coefficient: 0.812, and 95% CI: [0.378, 0.955]), and the corresponding performance bias (-29.5%) was statistically significant. CONCLUSION: The presented study demonstrated the potential of using the DL-MO for image quality assessment in patient abdominal CT tasks.

MRI-detected extramural venous invasion of rectal cancer: Multimodality performance and implications at baseline imaging and after neoadjuvant therapy.

MRI is routinely used for rectal cancer staging to evaluate tumor extent and to inform decision-making regarding surgical planning and the need for neoadjuvant and adjuvant therapy. Extramural venous invasion (EMVI), which is intravenous tumor extension beyond the rectal wall on histopathology, is a predictor for worse prognosis. T2-weighted images (T2WI) demonstrate EMVI as a nodular-, bead-, or worm-shaped structure of intermediate T2 signal with irregular margins that arises from the primary tumor. Correlative diffusion-weighted images demonstrate intermediate to high signal corresponding to EMVI, and contrast enhanced T1-weighted images demonstrate tumor signal intensity in or around vessels. Diffusion-weighted and post contrast images may increase diagnostic performance but decrease inter-observer agreement. CT may also demonstrate obvious EMVI and is potentially useful in patients with a contraindication for MRI. This article aims to review the spectrum of imaging findings of EMVI of rectal cancer on MRI and CT, to summarize the diagnostic accuracy and inter-observer agreement of imaging modalities for its presence, to review other rectal neoplasms that may cause EMVI, and to discuss the clinical significance and role of MRI-detected EMVI in staging and restaging clinical scenarios.

Magnetic resonance imaging features of small-duct primary sclerosing cholangitis.

PURPOSE: To evaluate the biliary tree and hepatic parenchymal findings on magnetic resonance imaging (MRI) and magnetic resonance cholangiopancreatography (MRCP) in small-duct primary sclerosing cholangitis (SD-PSC). METHODS: Thirty-nine patients with biopsy-proven primary sclerosing cholangitis (PSC) without any bile duct abnormality on MRCP (n = 15) or ERCP (n = 24) at the time of diagnosis were identified. Follow-up MRCP was available in 36/39 patients (12/15 Baseline MRCP group and 24 Baseline ERCP group). Two radiologists in consensus assessed the MRI/MRCP findings. The baseline MRI/MRCP of 15 SD-PSC patients was compared with MRI/MRCP of 15 normal healthy potential liver donors (Control group). Comparisons were made between SD-PSC patients and the Control group, and between baseline and follow-up MRI/MRCP findings in the SD-PSC patients. RESULTS: In the 15 Baseline MRCP SD-PSC subjects, the biliary tree was normal with a trend of larger bile ducts compared to the Control group. Periductal enhancement (arterial phase: 70%, 7/10; delayed phase: 90%, 9/10), heterogeneous parenchymal signal on T2-weighted (53%, 8/15) and post contrast-enhanced images (70%, 7/10), and enlarged periportal lymph nodes (73%, 11/15) were frequently present in patients with SD-PSC. Eight (33%) of 24 SD-PSC patients who had normal MRCP at baseline MRCP or initial follow-up MRCP after normal baseline ERCP showed large-duct PSC (LD-PSC) features on follow-up and the 10-year cumulative incidence for progression to LD-PSC rate was 8.5%. CONCLUSION: SD-PSC patients have a normal biliary tree but frequently have peribiliary enhancement, abnormal parenchymal signal intensity, and periportal lymphadenopathy. One-third shows progression to LD-PSC on follow-up.

LI-RADS: a conceptual and historical review from its beginning to its recent integration into AASLD clinical practice guidance.

The Liver Imaging Reporting and Data System (LI-RADS®) is a comprehensive system for standardizing the terminology, technique, interpretation, reporting, and data collection of liver observations in individuals at high risk for hepatocellular carcinoma (HCC). LI-RADS is supported and endorsed by the American College of Radiology (ACR). Upon its initial release in 2011, LI-RADS applied only to liver observations identified at CT or MRI. It has since been refined and expanded over multiple updates to now also address ultrasound-based surveillance, contrast-enhanced ultrasound for HCC diagnosis, and CT/MRI for assessing treatment response after locoregional therapy. The LI-RADS 2018 version was integrated into the HCC diagnosis, staging, and management practice guidance of the American Association for the Study of Liver Diseases (AASLD). This article reviews the major LI-RADS updates since its 2011 inception and provides an overview of the currently published LI-RADS algorithms.

Use of gadoxetate disodium in patients with chronic liver disease and its implications for liver imaging reporting and data system (LI-RADS).

Use of gadoxetate disodium, a hepatobiliary gadolinium-based agent, in patients with chronic parenchymal liver disease offers the advantage of improved sensitivity for detecting hepatocellular carcinoma (HCC). Imaging features of liver observations on gadoxetate-enhanced MRI may also serve as biomarkers of recurrence-free and overall survival following definitive treatment of HCC. A number of technical and interpretative pitfalls specific to gadoxetate exist, however, and needs to be recognized when protocoling and interpreting MRI exams with this agent. This article reviews the advantages and pitfalls of gadoxetate use in patients at risk for HCC, and the potential impact on Liver Imaging Reporting and Data System (LI-RADS) imaging feature assessment and categorization. Level of Evidence: 5 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2019;49:1236-1252.

Recommendation for terminology: Nodules without arterial phase hyperenhancement and with hepatobiliary phase hypointensity in chronic liver disease.

LEVEL OF EVIDENCE: 5 Technical Efficacy Stage: 3 J. Magn. Reson. Imaging 2018;47:1169-1171.

Differentiation of Hepatocellular Carcinoma from Other Hepatic Malignancies in Patients at Risk: Diagnostic Performance of the Liver Imaging Reporting and Data System Version 2014.

Purpose To evaluate the diagnostic performance and interrater reliability of the Liver Imaging Reporting and Data System (LI-RADS) version 2014 in differentiating hepatocellular carcinoma (HCC) from non-HCC malignancy in a population of patients at risk for HCC. Materials and Methods This retrospective HIPAA-compliant institutional review board-approved study was exempt from informed consent. A total of 178 pathology-proven malignant liver masses were identified in 178 patients at risk for HCC but without established extrahepatic malignancy from August 2012 through August 2015. Two readers blinded to pathology findings and clinical follow-up data independently evaluated a liver protocol magnetic resonance or computed tomography study for each lesion and assigned LI-RADS categories, scoring all major and most ancillary features. Statistical analyses included the independent samples t test, x2 test, Fisher exact test, and Cohen k. Results This study included 136 HCCs and 42 non-HCC malignancies. Specificity and positive predictive value of an HCC imaging diagnosis (LR-5 or LR-5V) were 69.0% and 90.5%, respectively, for reader 1 (R1) and 88.3% and 95.5%, respectively, for reader 2 (R2). Tumor in vein was a common finding in patients with non-HCC malignancies (R1, 10 of 42 [23.8%]; R2, five of 42 [11.9%]). Exclusion of the LR-5V pathway improved specificity and positive predictive value for HCC to 83.3% and 92.9%, respectively, for R1 (six fewer false-positive findings) and 92.3% and 96.4%, respectively, for R2 (one fewer false-positive finding). Among masses with arterial phase hyperenhancement, the rim pattern was more common among non-HCC malignancies than among HCCs for both readers (R1: 24 of 36 [66.7%] vs 13 of 124, [10.5%], P < .001; R2: 27 of 35 [77.1%] vs 21 of 123 [17.1%], P < .001) (k = 0.76). Exclusion of rim arterial phase hyperenhancement as a means of satisfying LR-5 criteria also improved specificity and positive predictive value for HCC (R1, two fewer false-positive findings). Conclusion Modification of the algorithmic role of tumor in vein and rim arterial phase hyperenhancement improves the diagnostic performance of LI-RADS version 2014 in differentiating HCC from non-HCC malignancy. © RSNA, 2017 Online supplemental material is available for this article.

Imaging Features of Biphenotypic Primary Liver Carcinoma (Hepatocholangiocarcinoma) and the Potential to Mimic Hepatocellular Carcinoma: LI-RADS Analysis of CT and MRI Features in 61 Cases.

OBJECTIVE: The purpose of this study was to determine the frequency with which biphenotypic primary liver carcinoma (also called hepatocholangiocarcinoma) may be misclassified as hepatocellular carcinoma (HCC) when only Liver Imaging Reporting and Data System (LI-RADS) major features are used and after consideration of ancillary features. MATERIALS AND METHODS: A review of all pathologically proven biphenotypic primary liver carcinomas diagnosed at one institution from 2006 to 2014 was performed. Two subspecialized abdominal imagers independently reviewed cases using LI-RADS version 2014 and assigned major features, ancillary features, and additional findings. The number of lesions meeting imaging criteria for HCC was determined after assessment of major features alone and after the addition of ancillary features. RESULTS: Sixty-one patients (30 men, 31 women; mean age, 62 years; range, 22-89 years) with biphenotypic primary liver carcinomas who underwent pretreatment multiphasic contrast-enhanced MRI (48 patients) or CT (13 patients) were included. According to LI-RADS major features alone, 33 (54.1%) lesions met criteria for HCC and therefore might have been misclassified. Thirteen had arterial phase hyperenhancement, washout, and a capsule. Twenty had arterial phase hyperenhancement with either washout (15 lesions) or a capsule (five lesions). After evaluation of ancillary features, 29 of these potential mimics exhibited at least one ancillary feature favoring non-HCC malignancy, possibly leading to appropriate reclassification. Of the four carcinomas that met criteria for HCC by major features and did not have ancillary features favoring non-HCC malignancy, two (3.3% of all tumors) fell within the Milan criteria. CONCLUSION: Most biphenotypic primary liver carcinomas have features of non-HCC malignancy and can be correctly categorized as such. Addition of ancillary features to major features may improve diagnostic accuracy over systems in which only major features are used.

Histogram analysis for characterization of indeterminate adrenal nodules on noncontrast CT.

OBJECTIVE: To determine the effectiveness of the CT histogram method to characterize indeterminate adrenal nodules above 10 Hounsfield units (HU) on noncontrast CT. MATERIALS AND METHODS: Retrospective review of clinical CT data from January 2005 through 2008 identified 194 indeterminate adrenal nodules (>10 HU on noncontrast CT) in 175 patients. 20 nodules in 18 patients were excluded due to large standard deviation (SD > 30) of HU values. Of the remaining 174 nodules, 131 were classified as benign lipid-poor nodules based on size stability for ≥1 year (104), in- and opposed-phase MRI (17), adrenal washout CT (3), or biopsy (7). 43 were classified as malignant by size increase over a short time (30), avid FDG uptake on PET/CT (15), or biopsy (5). Histogram analysis was performed by drawing a circular region of interest on all adrenal nodules. Mean attenuation, total number of pixels, number of negative pixels, and percentage of negative pixels were recorded for each nodule. RESULTS: At the threshold value of >10% negative pixels, 59/131 benign nodules were correctly characterized, but 1/43 malignant nodules was falsely characterized as benign (sensitivity 45%, specificity 98%, positive predictive value 98%). With a slightly higher threshold value of >15% negative pixels, there were no false benign judgments. 36 nodules had more than 15% negative pixels, all of which were benign (sensitivity 27%, specificity 100%, positive predictive value 100%). In the subgroup of benign nodules measuring 11-20 HU, 80% and 54% were identified with threshold values of >10% and >15% negative pixels, respectively. CONCLUSION: The CT histogram method with a threshold value of >10% negative pixels can identify many benign adrenal nodules with attenuation values >10 HU on unenhanced CT with extremely high specificity. A threshold of >15% negative pixels can achieve 100% specificity. This method is highly robust provided very "noisy" CT examinations (SD > 30) are eliminated.

Hepatobiliary agents and their role in LI-RADS.

The Liver Imaging Reporting and Data System (LI-RADS) was introduced with the goal of standardizing the diagnosis of hepatocellular carcinoma. The 2014 version of LI-RADS incorporates the use of hepatobiliary contrast agents (HBAs) into the diagnostic algorithm, including gadoxetate disodium and gadobenate dimeglumine. Three new ancillary features are introduced: hepatobiliary phase (HBP) hypointensity and HBP hypointense rim favor malignancy, while HBP isointensity favors benignity. HBP hyperintensity favors neither malignancy nor benignity. In this review, we describe how to use these new features as well as numerous pitfalls associated with the use ofHBAs, including hemangiomas, cholangiocarcinomas, and focal confluent fibrosis. Importantly, findings on the HBP are not included as major criteria and therefore the criteria for the diagnosis of LI-RADS 5 observations remain unchanged, and so congruence with the Organ Procurement Transplant Network system remains intact. Additionally, we review how the major features in LI-RADS, arterial phase hyperenhancement, threshold growth, and washout and capsule appearance, may be affected with HBAs. Notably with HBAs, hypointensity on the delayed phase, termed the transitional phase, does not qualify as washout appearance due to the possibility of early parenchymal enhancement. It is hoped that the incorporation of HBAs into LI-RADS will help create consistency when interpreting HBA enhanced MRIs.

CT colonography for the detection of nonpolypoid adenomas: sensitivity assessed with restricted national CT colonography trial criteria.

OBJECTIVE: The purpose of this study was to determine the prevalence of nonpolypoid adenomas and the sensitivity of CT colonography (CTC) in their detection by use of the restricted criteria of height-to-width ratio<50% and height elevation≤3 mm. MATERIALS AND METHODS: In the National CT Colonography Trial (American College of Radiology Imaging Network protocol 6664), a cohort of 2531 participants without symptoms underwent CTC and screening colonoscopy. The CTC examinations were interpreted with both 2D and 3D techniques. Nonpolypoid adenomatous polyps identified with CTC or colonoscopy were retrospectively reviewed to determine which polyps met the restricted criteria. The prevalence of nonpolypoid adenomas and the prospective sensitivity of CTC were determined. Descriptive statistics were used to report the prevalence, size, and histologic features. The sensitivities (with 95% CIs) for nonpolypoid and polypoid lesions were compared by two-sided Z test for independent binomial proportions. RESULTS: The retrospective review confirmed 21 nonpolypoid adenomas, yielding a prevalence of 0.83% (21 of 2531 participants). Eight (38.1%) were advanced adenomas, many (50% [4/8]) only because of large size (≥10 mm). The overall per polyp sensitivity of CTC (combined 2D and 3D interpretation) for detecting nonpolypoid adenomas≥5 mm (n=21) was 0.76; ≥6 mm (n=16), 0.75; and ≥10 mm (n=5), 0.80. These values were not statistically different from the sensitivity of detecting polypoid adenomas (p>0.37). CONCLUSION: In this large screening population, nonpolypoid adenomas had a very low prevalence (<1%), and advanced pathologic features were uncommon in polyps<10 mm in diameter. Most nonpolypoid adenomas are technically visible at CTC. The prospective sensitivity is similar to that for polypoid adenomas when the interpretation combines both 2D and 3D review.

Validation of organ procurement and transplant network (OPTN)/united network for organ sharing (UNOS) criteria for imaging diagnosis of hepatocellular carcinoma.

BACKGROUND: Imaging diagnosis of hepatocellular carcinoma (HCC) presents an important pathway for transplant exception points and priority for cirrhotic patients. The purpose of this retrospective study is to evaluate the validity of the new Organ Procurement and Transplant Network (OPTN) classification system on patients undergoing transplantation for HCC. METHODS: One hundred twenty-nine patients underwent transplantation for HCC from April 14, 2006 to April 18, 2011; a total of 263 lesions were reported as suspicious for HCC on pretransplantation magnetic resonance imaging. Magnetic resonance imaging examinations were reviewed independently by two experienced radiologists, blinded to final pathology. Reviewers identified major imaging features and an OPTN classification was assigned to each lesion. Final proof of diagnosis was pathology on explant or necrosis along with imaging findings of ablation after transarterial chemoembolization. RESULTS: Application of OPTN imaging criteria in our population resulted in high specificity for the diagnosis of HCC. Sensitivity in diagnosis of small lesions (≥1 and <2 cm) was low (range, 26%-34%). Use of the OPTN system would have resulted in different management in 17% of our population who had received automatic exception points for HCC based on preoperative imaging but would not have met criteria under the new system. Eleven percent of the patients not meeting OPTN criteria were found to have T2 stage tumor burden on pathology. CONCLUSIONS: The OPTN imaging policy introduces a high level of specificity for HCC but may decrease sensitivity for small lesions. Management may be impacted in a number of patients, potentially requiring longer surveillance periods or biopsy to confirm diagnosis.

The National CT Colonography Trial: assessment of accuracy in participants 65 years of age and older.

PURPOSE: To conduct post-hoc analysis of National CT Colonography Trial data and compare the sensitivity and specificity of computed tomographic (CT) colonography in participants younger than 65 years with those in participants aged 65 years and older. MATERIALS AND METHODS: Of 2600 asymptomatic participants recruited at 15 centers for the trial, 497 were 65 years of age or older. Approval of this HIPAA-compliant study was obtained from the institutional review board of each site, and informed consent was obtained from each subject. Radiologists certified in CT colonography reported lesions 5 mm in diameter or larger. Screening detection of large (≥10-mm) histologically confirmed colorectal neoplasia was the primary end point; screening detection of smaller (6-9-mm) colorectal neoplasia was a secondary end point. The differences in sensitivity and specificity of CT colonography in the two age cohorts (age < 65 years and age ≥ 65 years) were estimated with bootstrap confidence intervals (CIs). RESULTS: Complete data were available for 477 participants 65 years of age or older (among 2531 evaluable participants). Prevalence of adenomas 1 cm or larger for the older participants versus the younger participants was 6.9% (33 of 477) versus 3.7% (76 of 2054) (P < .004). For large neoplasms, mean estimates for CT colonography sensitivity and specificity among the older cohort were 0.82 (95% CI: 0.644, 0.944) and 0.83 (95% CI: 0.779, 0.883), respectively. For large neoplasms in the younger group, CT colonography sensitivity and specificity were 0.92 (95% CI: 0.837, 0.967) and 0.86 (95% CI: 0.816, 0.899), respectively. Per-polyp sensitivity for large neoplasms for the older and younger populations was 0.75 (95% CI: 0.578, 0.869) and 0.84 (95% CI: 0.717, 0.924), respectively. For the older and younger groups, per-participant sensitivity was 0.72 (95% CI: 0.565, 0.854) and 0.81 (95% CI: 0.745, 0.882) for detecting adenomas 6 mm in diameter or larger. CONCLUSION: For most measures of diagnostic performance and in most subsets, the difference between senior-aged participants and those younger than 65 years was not statistically significant.

CT colonography screening: ready for prime time?

Every year more than one million new patients are diagnosed with colon cancer worldwide. Although multiple prospective randomized trials and observational studies have demonstrated that mortality from colon cancer can be reduced with screening and removal of adenomatous polyps, compliance with screening guidelines remains low. Recent CT colonography (CTC) trials have shown that CTC is capable of demonstrating adenomatous polyps > or =10 mm (and in most cases > or = 6 mm) with sensitivities comparable to those for optical colonoscopy. Based on these results, at least two expert panels have recommended CTC as an option for colorectal cancer screening. Despite these endorsements, the Centers for Medicare and Medicaid Services (CMS) in the United States recently decided to deny coverage of CTC for colorectal cancer screening. This article addresses the reservations raised by CMS and provides a perspective on whether CTC is ready for routine use as a colorectal cancer screening test.

Contrast safety in the cancer patient: preventing contrast-induced nephropathy.

Cancer patients undergo frequent imaging examinations. Computed tomography (CT) examinations for tumor staging and assessment of treatment response generally require administration of intravascular contrast medium. Iodinated contrast agents for CT are associated with the risk of contrast-induced nephrotoxicity (CIN), particularly in patients with impaired renal function and diabetes. In many cancer patients the risk of complications from intravascular contrast medium administration is compounded by advanced age, dehydration and coadministration of nephrotoxic chemotherapeutic drugs. In this article I review the definition, clinical manifestations, possible mechanisms and risk factors for CIN, and provide recommendations for prevention of this potentially life-threatening complication.