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.
"Our analyses suggest that patients who undergo initial CTC, with or without subsequent OC, may experience lower rates of serious gastrointestinal, other gastrointestinal and cardiovascular events compared to patients who receive initial OC. This finding is intuitively reasonable, given that CTC does not require sedation and the intention of CTC is to selectively refer the approximately 8–15% of patients with suspected clinically significant polyps (N6 mm) and masses to OC for further evaluation (Kim et al., 2007, 2010; Macari et al., 2011). However, it is important to recognize that we were unable to fully adjust for differences between the groups based upon the information available in claims data. "
[Show abstract][Hide abstract] ABSTRACT: To evaluate gastrointestinal and cardiovascular adverse event risks associated with optical colonoscopy (OC) among Medicare outpatients who received computed tomography colonography (CTC) as their initial method of colorectal evaluation.
Medicare claims were compared between 6,114 outpatients ≥ 66 years who received initial CTC and 149,202 outpatients who received initial OC between January 2007 and December 2008. OC patients were matched on county of residence and year of evaluation. Outcomes included lower gastrointestinal bleeding, gastrointestinal perforation, other gastrointestinal events and cardiovascular events resulting in an emergency department visit or hospitalization within 30 days.
Among 1,000 outpatients undergoing initial CTC, 12.4 experienced lower gastrointestinal bleeding, 0.7 perforation, 18.0 other gastrointestinal events and 45.5 cardiovascular events within 30 days. After multivariate adjustment, risks of lower gastrointestinal bleeding, other gastrointestinal events and cardiovascular events were higher with initial OC than CTC, with or without subsequent OC (OR 1.91 95CI [1.47,2.49], OR 1.35 95CI [1.07,1.69] and OR 1.38 95CI [1.18,1.62], respectively); however, perforation risk did not differ (p=0.10). This pattern is similar in older and symptomatic populations.
Rates of gastrointestinal bleeding, other gastrointestinal events and cardiovascular events are lower following initial CTC than OC, but rates of perforation do not differ.
[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
[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.
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