CT colonography: Performance and program outcome measures in an older screening population
ABSTRACT To evaluate computed tomographic (CT) colonography performance and program outcome measures in an older cohort (65-79 years) of an established large-scale colorectal cancer screening program.
This HIPAA-compliant study was approved by the institutional review board; informed consent waived. Retrospective analysis of the 65-79-year-old cohort (n = 577) from the University of Wisconsin CT colonography screening program (n = 5176) was undertaken. Performance and outcome measures including advanced neoplasia prevalence and colonoscopy referral, extracolonic finding, extracolonic work-up, and complication rates were obtained by using a CT colonography database and review of medical records. Comparisons between the older cohort and the general screening population were made by using the Student t, Pearson chi(2), and Fisher exact tests. A P value <or= .05 was considered to indicate a significant difference.
With a 6-mm threshold for positivity, the overall referral rate to optical colonoscopy was 15.3% (88 of 577), leading to 277 polypectomies and the removal of 103 nondiminutive adenomas. For adenomas, the per-patient positivity rates were 10.9% (63 of 577) and 6.8% (39 of 577) at the 6- and 10-mm thresholds, respectively. The prevalence of advanced neoplasia was 7.6% (44 of 577). Fifty-four adenomas met advanced status, and five unsuspected cancers were detected. The advanced neoplasias identified were typically large, with a mean size of 21 mm. Potentially important extracolonic findings were seen in 15.4% (89 of 577) of patients, with a work-up rate of 7.8% (45 of 577). The majority of important extracolonic diagnoses were vascular aneurysms (n = 18). No major complications were encountered.
CT colonography is a safe and effective screening modality for the older population.
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Conference Paper: A parallel digital architecture for delta-sigma modulation[Show abstract] [Hide abstract]
ABSTRACT: A major drawback of delta-sigma modulation is the high oversampling ratios required, especially for single-bit quantization. Accordingly, much of the research in the area has focused on lowering the sampling rate through various parallelization approaches. However, this research has been overwhelmingly concentrated on continuous and discrete-time analog modulator implementations for A/D converters, and not on reducing the critical path in a digital implementation for D/A conversion. In this paper the popular time-interleaved modulator is paired with a vector quantizer implementation of a finite-length modulator to form a parallel implementation of a delta-sigma DAC with a reduced critical path.Circuits and Systems, 2002. MWSCAS-2002. The 2002 45th Midwest Symposium on; 09/2002
Chapter: Extracolonic Findings[Show abstract] [Hide abstract]
ABSTRACT: Computed tomography colonography (CTC), also referred to as virtual colonoscopy, is a noninvasive CT examination of the colon that has shown promise as a tool for colorectal cancer screening. In most cases, CTC is performed without i.v. contrast at a reduced radiation dose. Therefore, in addition to intraluminal images of the colon, a noncontrast CT of the entire abdomen and pelvis, and often the lower thorax, is obtained. This allows CTC to image many organs other than the colon during a routine study, unlike other colon screening examinations such as endoscopy or barium enema. This ability can be seen as a double-edged sword (Hara 2005). In fact, the ability to evaluate extracolonic structures can present a clinical dilemma. On the one hand, CTC may incidentally demonstrate asymptomatic malignant diseases or other clinically important conditions, thus possibly decreasing morbidity or mortality. On the other hand, CTC may reveal numerous find-ings of no clinical relevance. This could result in costly additional diagnostic examinations with an increase in morbidity and an overall negative effect on a patient's health (Sosna et al. 2005). Only a minority of the extracolonic findings observed by means of CTC are clinically important (Zalis et al. 2005; Pickhardt et al. 2003; Hara et al. 2000). Excessive caution and ambiguity in the description of findings, which are almost certainly benign, can lead to considerable follow-up examination costs and unnecessary anxiety for the patient (Zalis et al. 2005). But there are also technical considerations to put forth. In fact, it is also important for the interpreting radiologist to remain cognizant of the diagnostic limitations imposed by the reduced X-ray dose and infrequent use of intravenous contrast material that are typical when screening colorectal cancer via CTC.12/2009: pages 165-173;
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ABSTRACT: To retrospectively evaluate the frequency of recommendations for additional imaging (RAIs) for important extracolonic findings and polyp prevalence among a cohort of seniors (age ≥ 65 years) and nonseniors (age < 65 years) undergoing low-dose computed tomographic (CT) colonography. Institutional review board approval was obtained for this HIPAA-compliant retrospective study. Four hundred fifty-four patients (204 nonseniors: mean age, 52 years; 250 seniors: mean age, 69 years) underwent CT colonography at an outpatient facility. Cases were prospectively reported by one of four abdominal radiologists with expertise in CT colonography. The dictated reports were reviewed to determine the frequency of polyps (≥6 mm), the number of extracolonic findings, and the number of RAIs generated. The Fisher exact test was used to compare the percentage of seniors and nonseniors with at least one reported polyp, with at least one extracolonic finding, as well as the frequency of RAIs. The percentage of patients with at least one reported polyp was 14.2% (29 of 204) for the nonsenior group and 13.2% (33 of 250) for seniors, which was not significantly different (P = .772). The percentage of patients with at least one extracolonic finding was 55.4% (113 of 204) for nonseniors and 74.0% (185 of 250) for seniors (P < .0001). The percentage of patients in which an RAI was suggested was 4.4% (nine of 204) for nonseniors and 6.0% (15 of 250) for seniors, which was not significantly different (P = .450). Extracolonic findings were more frequent in seniors than in nonseniors; however, there was no significant difference in the frequency of RAIs between the two groups. http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11102144/-/DC1.Radiology 04/2011; 259(3):767-74. DOI:10.1148/radiol.11102144 · 6.21 Impact Factor