Matthew A. Barish

A Comparison of Virtual and Conventional Colonoscopy for the Detection of Colorectal Polyps

BACKGROUND Virtual colonoscopy is a new method of imaging the colon in which thin-section, helical computed tomography (CT) is used to generate high-resolution, two-dimensional axial images. Three-dimensional images of the colon simulating those obtained with conventional colonoscopy are then reconstructed off-line. We compared the performance of virtual and conventional colonoscopy for the detection of colorectal polyps. METHODS We prospectively studied 100 patients at high risk for colorectal neoplasia (60 men and 40 women; mean age, 62 years). We performed virtual colonoscopy immediately before conventional colonoscopy. We inserted a rectal tube and insufflated the colon with air to the maximal level that the patient could tolerate. We administered 1 mg of glucagon intravenously immediately before CT scanning to minimize the degree of smooth-muscle spasm and peristalsis and to reduce the patients discomfort. RESULTS The entire colon was clearly seen by virtual colonoscopy in 87 patients and by conventional colonoscopy in 89. Fifty-one patients had normal findings on conventional colonoscopy. In the other 49, we identified a total of 115 polyps and 3 carcinomas. Virtual colonoscopy identified all 3 cancers, 20 of 22 polyps that were 10 mm or more in diameter (91 percent), 33 of 40 that were 6 to 9 mm (82 percent), and 29 of 53 that were 5 mm or smaller (55 percent). There were 19 false positive findings of polyps and no false positive findings of cancer. Of the 69 adenomatous polyps, 46 of the 51 that were 6 mm or more in diameter (90 percent) and 12 of the 18 that were 5 mm or smaller (67 percent) were correctly identified by virtual colonoscopy. Although discomfort was not specifically recorded, none of the patients requested that virtual colonoscopy be stopped because of discomfort or pain. CONCLUSIONS In a group of patients at high risk for colorectal neoplasia, virtual and conventional colonoscopy had similar efficacy for the detection of polyps that were 6 mm or more in diameter.

ACR Colon Cancer Committee White Paper: Status of CT Colonography 2009

PURPOSE To review the current status and rationale of the updated ACR practice guidelines for CT colonography (CTC). METHODS Clinical validation trials in both the United States and Europe are reviewed. Key technical aspects of the CTC examination are emphasized, including low-dose protocols, proper insufflation, and bowel preparation. Important issues of implementation are discussed, including training and certification, definition of the target lesion, reporting of colonic and extracolonic findings, quality metrics, reimbursement, and cost-effectiveness. RESULTS Successful validation trials in screening cohorts both in the United States with ACRIN and in Germany demonstrated sensitivity > or = 90% for patients with polyps >10 mm. Proper technique is critical, including low-dose techniques in screening cohorts, with an upper limit of the CT dose index by volume of 12.5 mGy per examination. Training new readers includes the requirement of interactive workstation training with 2-D and 3-D image display techniques. The target lesion is defined as a polyp > or = 6 mm, consistent with the American Cancer Society joint guidelines. Five quality metrics have been defined for CTC, with pilot data entered. Although the CMS national noncoverage decision in May 2009 was a disappointment, multiple third-party payers are reimbursing for screening CTC. Cost-effective modeling has shown CTC to be a dominant strategy, including in a Medicare cohort. CONCLUSION Supported by third-party payer reimbursement for screening, CTC will continue to further transition into community practice and can provide an important adjunctive examination for colorectal screening.

Texture Feature Extraction and Analysis for Polyp Differentiation via Computed Tomography Colonography

Image textures in computed tomography colonography (CTC) have great potential for differentiating non-neoplastic from neoplastic polyps and thus can advance the current CTC detection-only paradigm to a new level with diagnostic capability. However, image textures are frequently compromised, particularly in low-dose CT imaging. Furthermore, texture feature extraction may vary, depending on the polyp spatial orientation variation, resulting in variable results. To address these issues, this study proposes an adaptive approach to extract and analyze the texture features for polyp differentiation. Firstly, derivative (e.g. gradient and curvature) operations are performed on the CT intensity image to amplify the textures with adequate noise control. Then Haralick co-occurrence matrix (CM) is used to calculate texture measures along each of the 13 directions (defined by the first and second order image voxel neighbors) through the polyp volume in the intensity, gradient and curvature images. Instead of taking the mean and range of each CM measure over the 13 directions as the so-called Haralick texture features, Karhunen-Loeve transform is performed to map the 13 directions into an orthogonal coordinate system so that the resulted texture features are less dependent on the polyp orientation variation. These simple ideas for amplifying textures and stabilizing spatial variation demonstrated a significant impact for the differentiating task by experiments using 384 polyp datasets, of which 52 are non-neoplastic polyps and the rest are neoplastic polyps. By the merit of area under the curve of receiver operating characteristic, the innovative ideas achieved differentiation capability of 0.8016, indicating the CTC diagnostic feasibility.

An Adaptive Paradigm for Computer-Aided Detection of Colonic Polyps

Most previous efforts in developing computer-aided detection (CADe) of colonic polyps apply similar measures or parameters to detect polyps regardless of their locations under an implicit assumption that all the polyps reside in a similar local environment, e.g. on a relatively flat colon wall. In reality, this implicit assumption is frequently invalid, because the haustral folds can have a very different local environment from that of the relatively flat colon wall. We conjecture that this assumption may be a major cause of missing the detection of polyps, especially small polyps (<10 mm linear size) located on the haustral folds. In this paper, we take the concept of adaptiveness and present an adaptive paradigm for CADe of colonic polyps. Firstly, we decompose the complicated colon structure into two simplified sub-structures, each of which has similar properties, of (1) relatively flat colon wall and (2) ridge-shaped haustral folds. Then we develop local environment descriptions to adaptively reflect each of these two simplified sub-structures. To show the impact of the adaptiveness of the local environment descriptions upon the polyp detection task, we focus on the local geometrical measures of the volume data for both the detection of initial polyp candidates (IPCs) and the reduction of false positives (FPs) in the IPC pool. The experimental outcome using the local geometrical measures is very impressive such that not only the previously-missed small polyps on the folds are detected, but also the previously miss-removed small polyps on the folds during FP reduction are retained. It is expected that this adaptive paradigm will have a great impact on detecting the small polyps, measuring their volumes and volume changes over time, and optimizing their management plan.

Image Interpretation Session: Sunday, November 25, 2001

The Sunday afternoon Image Interpretation Session remains a highly attended and anticipated highlight of the annual meeting of the Radiological Society of North America. Now an established RSNA tradition since its introduction in 1939, this year’s session promises to be another challenging and entertaining encounter with 10 unknown cases, two each in the categories of musculoskeletal, abdominal, thoracic, ultrasound, and neurologic imaging. All of the cases for discussion have been seen at Boston Medical Center over the past year, and thus reflect the disease mix of an active urban academic medical center. The panel is composed of five internationally known authorities, who will have the opportunity to demonstrate their individual approach to elucidating and organizing the radiologic findings to arrive at a reasonable differential diagnosis. We hope to make this session not the “ultimate board certification examination,” but rather a real-life approach by experienced radiologists to cases encountered in a...

Image Interpretation Session

The Sunday afternoon Image Interpretation Session remains a highly attended and anticipated highlight of the annual meeting of the Radiological Society of North America. Now an established RSNA tradition since its introduction in 1939, this year’s session promises to be another challenging and entertaining encounter with 10 unknown cases, two each in the categories of musculoskeletal, abdominal, thoracic, ultrasound, and neurologic imaging. All of the cases for discussion have been seen at Boston Medical Center over the past year, and thus reflect the disease mix of an active urban academic medical center. The panel is composed of five internationally known authorities, who will have the opportunity to demonstrate their individual approach to elucidating and organizing the radiologic findings to arrive at a reasonable differential diagnosis. We hope to make this session not the “ultimate board certification examination,” but rather a real-life approach by experienced radiologists to cases encountered in a...

Image Interpretation Session1

The Sunday afternoon Image Interpretation Session remains a highly attended and anticipated highlight of the annual meeting of the Radiological Society of North America. Now an established RSNA tradition since its introduction in 1939, this year’s session promises to be another challenging and entertaining encounter with 10 unknown cases, two each in the categories of musculoskeletal, abdominal, thoracic, ultrasound, and neurologic imaging. All of the cases for discussion have been seen at Boston Medical Center over the past year, and thus reflect the disease mix of an active urban academic medical center. The panel is composed of five internationally known authorities, who will have the opportunity to demonstrate their individual approach to elucidating and organizing the radiologic findings to arrive at a reasonable differential diagnosis. We hope to make this session not the “ultimate board certification examination,” but rather a real-life approach by experienced radiologists to cases encountered in a...