Radiation risks from exposure to chest computed tomography.
ABSTRACT Since 1972, when the first clinical computed tomography (CT) scanner was installed, amazing advances in CT technology have spurned its rapid growth and increasing utilization. Although CT scans are often performed for clinically valid indications that enable proper medical decision-making, the introduction of some protocols has outpaced the scientific data supporting their appropriateness. Considering the growing volume of CT scans performed and the appurtenant risks of radiation exposure, any exposure of patients to radiation for unnecessary or undocumented indications is worrisome. In this paper, the radiation risks associated with chest CT in 3 specific scenarios are discussed: (1) lung cancer screening, for which scientific data demonstrating a reduction in lung cancer mortality is lacking; (2) CT coronary artery angiography, for which the peer reviewed scientific literature is in evolution as its clinical utility is defined and expanded; and (3) CT pulmonary angiography, which is now widely utilized as the imaging modality of choice in the diagnosis of pulmonary emboli. The risks and benefits of these studies will be reviewed in light of the population radiation burden and the appropriateness of each examination.
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ABSTRACT: Venous thromboembolism and pulmonary embolism (VTE/PE) remain a diagnostic challenge. The computed tomography pulmonary angiogram (CTPA) has emerged as a popular diagnostic test for PE. However, there is limited data on diagnostic yield and complications in actual clinical settings. Our goal was to determine the diagnostic yield for PE and rate of renal complications following CTPA in a large community hospital setting. A retrospective chart review of 1,514 patients who underwent CTPA in the emergency department or during the initial 24 hours of admission to a community-based academic hospital. Of 1,514 CTPAs, 125 were positive for VTE/PE yielding a positive diagnosis in 8.2%. Dyspnea was the most common symptom in patients and a normal physical exam was the most common finding. Among the 925 patients with adequate data to calculate the rate of contrast-induced nephropathy (CIN), 25.8% had an increase of at least 25% in serum creatinine following the CTPA. Pre-existing diabetes and age were the most important predictors of CIN. CTPA has a low diagnostic yield for PE in a community setting, and in some patient populations, the rate of contrast-induced nephropathy may be higher than previously reported in the literature. Due to the retrospective nature of this study we were limited in using pre-test scoring systems and in measuring the impact of alternative CT diagnoses on patient management.07/2012; 2(2). DOI:10.3402/jchimp.v2i2.17722
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ABSTRACT: BACKGROUND: There is growing concern over the long-term radiation exposure from serial computed tomographic (CT) scan follow-up after endovascular aneurysm repair (EVAR) of abdominal aortic aneurysms (AAAs). Screening for endoleaks with non-contrast-enhanced volumetric CT has been shown to significantly reduce radiation doses. We evaluated the use of NCT as the primary method of follow-up after EVAR of AAAs. METHODS: Our institutional post-EVAR CT protocol consisted of contrast-enhanced CT angiography (CTA) 1 month after repair, followed by NCT at 3 or 6 and 12 months, and annually thereafter. At each follow-up scan, immediate 3-dimensional volume analysis was performed. If the volume change was <2%, NCT follow-up was continued. If the volume increased by ≥2% on nonenhanced images, contrast-enhanced CT was performed immediately to identify potential endoleaks. All images were reviewed by an experienced cardiovascular radiologist. End points included identification of endoleak, reintervention, and rupture. RESULTS: Over a 7-year period, 126 patients were followed. Serial CTA was performed in 59 patients, while 67 patients were followed with the NCT protocol. The mean follow-up was 2.07 years. There were no differences in age, sex, or initial aneurysm volume or size. There were 35 total endoleaks identified. Twenty of these were early endoleaks (<30 days post-EVAR). The remaining 15 leaks were late in nature (10 in the contrast group and 5 in the noncontrast group; P = 0.17). NCT aneurysm sac volume changes prompted contrasted studies in all 5 late leaks. The mean volume change was 11.2 cm(3), an average change of 5.88%. These findings were not significantly different than the late leaks found by routine contrast studies (8.9 cm(3); 4.98% [P = 0.58]). There were no delayed ruptures or emergent reinterventions in the NCT group. CONCLUSIONS: Serial NCT appears to be safe and effective as the sole means of follow-up after EVAR for AAAs. AAA volume increases of ≥2% should prompt further contrast-enhanced CT imaging. Changes of <2% can be safely followed with serial NCT. This protocol requires dedicated cardiovascular radiologist involvement, and patients should be retained in the radiology suite until real-time image evaluation can be completed.Annals of Vascular Surgery 05/2013; 27(8). DOI:10.1016/j.avsg.2012.10.021 · 1.03 Impact Factor
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ABSTRACT: This Directed Reading article describes the physical principles and instrumentation of computed tomography (CT) and outlines several recent advances in CT technology. First, the history of CT is presented with emphasis on the contributions of two pioneers who earned the Nobel Prize for the development of the first clinically useful CT scanner. Second, the essential physical principles—most notably radiation attenuation, Lambert-Beer's Law—and the calculation of CT numbers using attenuation data are described. The third major topic will focus on CT technology, including a description of the major system components, the evolution of CT data acquisition systems, image reconstruction fundamentals and common digital image postprocessing operations such as windowing and three-dimensional (3D) techniques. The next section of this article addresses the elements of spiral/helical CT principles and technology. The limitations of conventional CT are first presented and provide a motivation for the development of volume CT scanners. Data acquisition, including detector technology and slip-ring technology, is reviewed, followed by a description of image reconstruction basics for multislice CT (MSCT) scanning. In particular, MSCT detector technology, pitch and various advantages are outlined, followed by a discussion of the advantages of MSCT scanning. The final section of this reading reviews the elements of MSCT applications, such as 3D imaging, virtual reality imaging and the basics of cardiac CT imaging. The article concludes with an introduction of the use of CT in other areas, such as radiation therapy and nuclear medicine.Journal of Medical Imaging and Radiation Sciences 06/2010; 41(2):87-109. DOI:10.1016/j.jmir.2010.04.001