CT colonography's role in the COVID-19 pandemic: a safe(r), socially distanced total colon examination.

PURPOSE: To describe the favorable procedural profile of CT colonography (CTC) during the COVID-19 pandemic. CONCLUSION: Postponement of cancer screening due to COVID-19 has resulted in a backlog of individuals needing to undergo structural examination of the colon. The experience during the initial COVID-19 surge with urgent evaluation of the colon for transplant patients prior to transplant suggests that CTC can be done in a lower risk manner as compared to other structural examinations. The procedural profile of CTC is advantageous during this pandemic as maintaining social distancing and preserving healthcare supplies including PPE are of paramount importance. CTC is an important option to utilize in the screening armamentarium to allow effective screening of average risk asymptomatic individuals in the COVID-19 era.

Use of Screening CT Colonography by Age and Race: A Study of Potential Access Barriers Related to Medicare Noncoverage Based on Data From the ACR's National CT Colonography Registry.

OBJECTIVE: The primary objectives of this investigation were to evaluate the use of screening CT colonography (CTC) examinations by age comparing individuals of Medicare-eligible age to younger cohorts and to determine if the association between use of CTC and Medicare-eligible age varies by race. Although the Affordable Care Act requires commercial insurance coverage of screening CTC, Medicare does not cover screening CTC. MATERIALS AND METHODS: Using the ACR's CTC registry, the distribution of procedures by age was evaluated using a negative binomial model with patient age (to capture overall trend), indicator of Medicare-eligible age (to capture immediate changes in trend at age 65), and their interaction (to capture gradual changes after age 65) as independent variables. The association between the number of screening CTCs and age was compared by racial identity. RESULTS: The CTC registry contained data on 12,648 screening examinations. Between ages 52 and 64, the number of screening examinations increased; each additional age year was associated with a 5.3% (P < .001) increase in the number of screenings. However, after age 65, the number of screening examinations decreased by -6.9% per additional year of age above 65 compared with the trend between ages 52 and 64 (P < .001). The modal age group for CTC use was 65 to 69 years in white and 55 to 59 in black individuals. CONCLUSION: After age 65, the number of screening CTC examinations decreased, likely due, at least in part, to lack of Medicare coverage. Medicare noncoverage may have a disproportionate impact on black patients and other racial minorities.

Pearls and Pitfalls of Interpretation in CT Colonography.

The accuracy of computed tomography (CT) colonography (CTC) requires that the radiologist be well trained in the recognition of pitfalls of interpretation. In order to achieve a high sensitivity and specificity, the interpreting radiologist must be well versed in the causes of both false-positive and false-negative results. In this article, we review the common and uncommon pitfalls of interpretation in CTC.

Abnormal Pouchogram Predicts Pouch Failure Even in Asymptomatic Patients.

BACKGROUND: Anastomotic complications after restorative total proctocolectomy with IPAA for ulcerative colitis alter functional outcomes and quality of life and may lead to pouch failure. Routine contrast enema of the pouch assesses anastomotic integrity before ileostomy reversal, but its clinical use is challenged. OBJECTIVE: The purpose of this research was to assess the relationship among preoperative clinical characteristics, abnormal pouchography, and long-term pouch complications. DESIGN: This was a retrospective chart review. SETTINGS: The study was conducted at a tertiary care center between 2000 and 2010. PATIENTS: Ulcerative colitis patients with IPAA undergoing pouchography before ileostomy closure were included. MAIN OUTCOME MEASURES: Patient demographics, incidence of pouch-related complications, and findings on pouchogram were recorded. Primary outcome was pouch failure, defined as excision or permanent diversion of the ileoanal pouch. Independent predictors of pouch failure were determined by multivariate regression. RESULTS: A total of 262 patients with ulcerative colitis were included. Contrast extravasation was seen in 27 patients (10.3%): 14 (51.9%) were clinically asymptomatic at the time of pouchogram. Six (22.2%) of 27 patients with extravasation developed pouch failure despite normalization of the pouchogram before ileostomy closure. Forty patients (15.3%) were found to have pouch-anal anastomotic stenosis; only 1 developed pouch failure. Pre-IPAA serum albumin and hemoglobin levels were inversely associated with contrast extravasation (serum albumin: OR = 0.42; hemoglobin: OR = 0.77; p < 0.05). Contrast extravasation was associated with delayed takedown operation (average = 67 d), increased risk (OR = 5.25; p < 0.01), and shorter time (median = 32.0 vs 72.5 mo; HR = 5.88; p < 0.05) to pouch failure, as well as increased risk of pouch-related complications (p < 0.05). LIMITATIONS: The study was limited by its retrospective nature and small number of patients who developed pouch failure. CONCLUSIONS: Pouchography before ileostomy takedown is useful in identifying patients with ulcerative colitis at risk for postoperative complications. Radiologic resolution of IPAA-related leak does not reliably predict healing; caution is warranted in this subgroup. See Video Abstract at http://links.lww.com/DCR/A818.

Structured reporting and quality control in CT colonography.

Standardized recommended techniques for performing and reporting CT colonography (CTC) examinations were developed by a consensus of experts. Published reporting guidelines, known as the CT colonography reporting and data system supplemented by recently updated comprehensive recommendations were incorporated into the American College of Radiology (ACR) practice guidelines. The application of continuous quality improvement to the practice of CT was aided by the development of an ACR national data registry (NRDR) for CTC that addressed both process and outcome quality measures. These measures can be used to benchmark an institution's CTC practice as compared to all participants. This article will discuss the best practices for reporting CTC and describe the use of NRDR to foster quality CTC performance.

Missed Acute Appendicitis on Multidetector Computed Tomography and Magnetic Resonance Imaging: Legal Ramifications, Challenges, and Avoidance Strategies.

The failure to diagnose acute appendicitis (AA) is the third most common medical malpractice allegation related to gastrointestinal disease. There is a paucity of detailed data on this topic; however, publications by Whang et al and by Berlin and Berlin, which analyzed all types of malpractice suits against radiologists, have shown that the incidence of litigation has increased over time in the United States. This is likely true for cases of AA as well. The misinterpretation of cross-sectional imaging in patients with suspected appendicitis may be caused by suboptimal technique, errors of omission, i.e, missing key findings, failure to review a portion of the examination, and satisfaction of search error. This article summarizes the published legal, clinical, and imaging literature regarding litigation in cases of missed AA, and reviews optimized multidetector computed tomography and magnetic resonance imaging protocols for the diagnosis of AA, with examples shown of challenging cases.

Quantitative radiology: automated measurement of polyp volume in computed tomography colonography using Hessian matrix-based shape extraction and volume growing.

BACKGROUND: Current measurement of the single longest dimension of a polyp is subjective and has variations among radiologists. Our purpose was to develop a computerized measurement of polyp volume in computed tomography colonography (CTC). METHODS: We developed a 3D automated scheme for measuring polyp volume at CTC. Our scheme consisted of segmentation of colon wall to confine polyp segmentation to the colon wall, extraction of a highly polyp-like seed region based on the Hessian matrix, a 3D volume growing technique under the minimum surface expansion criterion for segmentation of polyps, and sub-voxel refinement and surface smoothing for obtaining a smooth polyp surface. Our database consisted of 30 polyp views (15 polyps) in CTC scans from 13 patients. Each patient was scanned in the supine and prone positions. Polyp sizes measured in optical colonoscopy (OC) ranged from 6-18 mm with a mean of 10 mm. A radiologist outlined polyps in each slice and calculated volumes by summation of volumes in each slice. The measurement study was repeated 3 times at least 1 week apart for minimizing a memory effect bias. We used the mean volume of the three studies as "gold standard". RESULTS: Our measurement scheme yielded a mean polyp volume of 0.38 cc (range, 0.15-1.24 cc), whereas a mean "gold standard" manual volume was 0.40 cc (range, 0.15-1.08 cc). The "gold-standard" manual and computer volumetric reached excellent agreement (intra-class correlation coefficient =0.80), with no statistically significant difference [P (F≤f) =0.42]. CONCLUSIONS: We developed an automated scheme for measuring polyp volume at CTC based on Hessian matrix-based shape extraction and volume growing. Polyp volumes obtained by our automated scheme agreed excellently with "gold standard" manual volumes. Our fully automated scheme can efficiently provide accurate polyp volumes for radiologists; thus, it would help radiologists improve the accuracy and efficiency of polyp volume measurements in CTC.

Errors in CT colonography.

CT colonography (CTC) is a colorectal cancer screening modality which is becoming more widely implemented and has shown polyp detection rates comparable to those of optical colonoscopy. CTC has the potential to improve population screening rates due to its minimal invasiveness, no sedation requirement, potential for reduced cathartic examination, faster patient throughput, and cost-effectiveness. Proper implementation of a CTC screening program requires careful attention to numerous factors, including patient preparation prior to the examination, the technical aspects of image acquisition, and post-processing of the acquired data. A CTC workstation with dedicated software is required with integrated CTC-specific display features. Many workstations include computer-aided detection software which is designed to decrease errors of detection by detecting and displaying polyp-candidates to the reader for evaluation. There are several pitfalls which may result in false-negative and false-positive reader interpretation. We present an overview of the potential errors in CTC and a systematic approach to avoid them.

CT colonography with computer-aided detection: recognizing the causes of false-positive reader results.

Computed tomography (CT) colonography is a screening modality used to detect colonic polyps before they progress to colorectal cancer. Computer-aided detection (CAD) is designed to decrease errors of detection by finding and displaying polyp candidates for evaluation by the reader. CT colonography CAD false-positive results are common and have numerous causes. The relative frequency of CAD false-positive results and their effect on reader performance on the basis of a 19-reader, 100-case trial shows that the vast majority of CAD false-positive results were dismissed by readers. Many CAD false-positive results are easily disregarded, including those that result from coarse mucosa, reconstruction, peristalsis, motion, streak artifacts, diverticulum, rectal tubes, and lipomas. CAD false-positive results caused by haustral folds, extracolonic candidates, diminutive lesions (<6 mm), anal papillae, internal hemorrhoids, varices, extrinsic compression, and flexural pseudotumors are almost always recognized and disregarded. The ileocecal valve and tagged stool are common sources of CAD false-positive results associated with reader false-positive results. Nondismissable CAD soft-tissue polyp candidates larger than 6 mm are another common cause of reader false-positive results that may lead to further evaluation with follow-up CT colonography or optical colonoscopy. Strategies for correctly evaluating CAD polyp candidates are important to avoid pitfalls from common sources of CAD false-positive results.

The challenges of CT colonography reimbursement.

CT colonography has been shown to be an effective method to screen for colorectal cancer. However, at present, full endorsement and reimbursement for screening CT colonography, particularly by the US Preventive Services Task Force and CMS, respectively, are absent, so this screening option is infrequently used, and optical colonoscopy remains the de facto standard screening option. The authors summarize the past accomplishments that led to the current state of reimbursement and outline the remaining challenges and road to full acceptance and reimbursement of screening CT colonography nationally.

Suspected extracolonic neoplasms detected on CT colonography: literature review and possible outcomes.

RATIONALE AND OBJECTIVES: This study summarizes the literature on the detection of cancer among indeterminate extracolonic findings on computed tomographic (CT) colonography in five targeted organs. MATERIALS AND METHODS: We searched PubMed for English-language literature published between January 1, 1994, and December 31, 2010. We describe extracolonic findings in the kidney, lung, liver, pancreas, and ovary suspect for malignancy as they are associated with high mortality. For each organ, we calculated the median prevalence, positive predictive value (PPV), and false positive rate of malignancy and a pooled false-positive rate across studies. RESULTS: Of 91 publications initially identified, 24 were eligible for review. Indeterminate renal masses on CT colonography had 20.5% median PPV and low pooled false positive rate of 1.3% (95% confidence interval 0.6-2.0). In contrast, indeterminate masses of the lung, liver, pancreas, and ovary had low PPV (median values ranged from 0% to 3.8%). Indeterminate masses of the ovary resulted in the highest pooled false-positive rate of 2.2%. Results were similar in studies of both screening and nonscreening populations. We estimated the probability of false positive results through the detection of significant extracolonic findings as 46 per 1000 for men and 68 per 1000 for women. CONCLUSIONS: Indeterminate renal masses newly detected on CT colonography have an estimated one in five chance of malignancy and therefore warrant further follow-up to provide a definitive diagnosis. Conversely, indeterminate masses of the lung, liver, pancreas, and ovary are associated with high false positive rates and merit more conservative clinical follow-up.

BMI-based radiation dose reduction in CT colonography.

RATIONALE AND OBJECTIVES: There is potential for x-ray dose reduction in computed tomography colonography (CTC) relative to body mass index (BMI). We evaluated the association between BMI and three-dimensional (3D) CTC image quality to assess the potential utility of BMI as the basis for radiation dose reduction in CTC. MATERIALS AND METHODS: Ninety-six consecutive patients underwent CTC and were randomized for scanning at 15 or 30 mAs. Extremely obese patients (BMI > 50) were excluded. Each patient was scanned supine and prone on a multidetector CT scanner. Postprocessing CTC visualization was performed on a dedicated workstation. Three independent observers assessed 3D image quality using a four-point scale. Image noise was measured in both the abdomen and pelvis. The association between BMI and image noise was examined using random-effects linear regression models. Logistic regression was used to examine the relationship between BMI, mAs, and conspicuity scores. RESULTS: Statistically significant differences in image noise were observed between 15 and 30 mAs in both the abdomen and pelvis, and the difference was greater with increasing BMI. A positive relationship was detected between BMI and noise in the abdomen (P < .001) and pelvis (P < .001). Inverse correlation was identified between BMI and conspicuity scores in the abdomen (P = .01) and pelvis (P < .001). Overall conspicuity scores were reduced for both 15 and 30 mAs groups as BMI increased. CONCLUSION: The radiation dose for CTC can be reduced by 40% and 70% below commonly employed doses for overweight and normal BMI patients, respectively, by using a BMI-adjusted dose reduction approach. Conspicuity scores dropped in obese patients with reduced dose suggesting that standard accepted doses should be utilized in that group.

Ectopic pancreas presenting with pancreatitis and a mesenteric mass.

Ectopic pancreas is defined by the presence of abnormally situated pancreatic tissue that lacks contact with normal pancreas and possesses its own duct system and vascular supply. Ectopic pancreas in the gastrointestinal tract is not uncommon. Moreover, there are several reported cases of adult ectopic pancreatitis in the literature, but to date, only two cases of pediatric ectopic pancreatitis have been reported. We describe a 15-year-old female with acute right upper quadrant pain and elevated serum lipase and amylase, in whom the radiological diagnosis was mesenteric soft tissue mass with adjacent inflammatory changes. The surgical pathology diagnosis, however, was mesenteric ectopic pancreas complicated by pancreatitis. We advocate for ectopic pancreatitis to be considered in a pediatric patient with acute abdominal pain, laboratory findings consistent with pancreatitis, and imaging findings of a mesenteric mass and normal orthotopic pancreas.

CAD-associated reader error in CT colonography.

RATIONALE AND OBJECTIVES: Computed tomographic colonographic interpretation with computer-aided detection (CAD) may be superior to unaided viewing, although polyp characteristics may influence accuracy. Reader error due to polyp characteristics was evaluated in a multiple-case, multiple-reader trial of computed tomographic colonography with CAD. MATERIALS AND METHODS: Two experts retrospectively reviewed 52 positive cases (74 polyps) and categorized them as hard, moderate, or easy to detect. Each case was evaluated without and with CAD. Features that may influence a reader's ability to detect a polyp or to accept or reject a CAD mark were tabulated. The association between polyp characteristics and detection rates in the trial was assessed. The difference in detection rates (CAD vs unassisted) was calculated, and regression analysis was performed. RESULTS: Of 64 polyps found by CAD, experts categorized 20 as hard, 28 as moderate, and 16 as easy to detect. Reader characterization errors predominated (47.3%) over other errors. Factors associated with lower detection rates included small size, flat morphology, and resemblance to a thickened fold. CAD was superior for polyps resembling lipomas compared to those that did not resemble lipomas (average increase in detection rate with CAD, 12.8% vs 5.5%; P < .05). CONCLUSIONS: Polyp characteristic may impair computed tomographic colonographic interpretation augmented by CAD. Readers can avoid errors of measurement by evaluating diminutive polyp candidates with sample measurements. Caution should be taken when evaluating focally thick folds and when using visual impression to dismiss a polyp candidate as a lipoma when it is submerged in densely tagged fluid.