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Radiation Dose and Exposure Indicators
Published in Ken Holmes, Marcus Elkington, Phil Harris, Clark's Essential Physics in Imaging for Radiographers, 2021
Absorbed dose in gray’s is defined as the energy absorbed by tissue per unit mass. The radiation output from a CT procedure is described by using the volume CT dose index (CTDIvol) and the dose length product (DLP). The CTDIvol is calculated using standard phantoms and is an estimate of the average X-ray output for any given CT examination. The DLP is the total X-ray output integrated throughout the entire examination and is calculated by multiplying the CTDIvol by the scanned length. This calculation does not take a patient’s body habitus into account therefore the size specific dose estimate (SSDE) is calculated by multiplying the CTDIvol by a correction factor based on patient size.
Introduction
Published in A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha, Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha
The significant features of a CT system that have made volume CT possible include the high-powered X-ray tube, slip ring technology, advanced detector design and interpolation algorithms. Contemporary X-ray tube and generators can produce a range of voltages (kV) appropriate for different clinical applications. The capability to produce a variety of X-ray spectra facilitates a balance between image quality, highest SNR ratio and lowest possible patient dose.
The Rationale for Intervention to Reduce the Risk of Cardiovascular Disease
Published in James M. Rippe, Lifestyle Medicine, 2019
James M. Rippe, Theodore J. Angelopoulos
High-speed computed tomography (CT Scanning) of the coronary arteries has been demonstrated in several studies to detect pre-clinical atherosclerosis.159 Advances such as volume CT scanning (VCT) may further enhance the precision and predictive value of these technologies. At the current time, these technologies remain investigational. Concern has also been raised about the potential to overinterpret predictive values from imaging techniques such as coronary calcium scoring. In one study, 41% of all future vascular events occurred in individuals with a coronary calcium score lower than 100, and 17% occurred with a coronary calcium score of zero.160 In this study, individuals with high risk scores by Framingham criteria but low coronary calcium scores still remained at high risk of CVD. Another imaging test which has been employed to attempt to assess risk of CVD is ultrasound measurement of the common carotid intima-media thickness (CIMT). With regard to CIMT, a meta-analysis of 14 population-based cohorts reported a consistent and statically significant 9% increase of future vascular risk for each 0.1 mm increase in CIMT thickness.161 This same analysis, however, found that CIMT measurement did not improve clinical accuracy once risk estimates and re classification were utilized to adjust for usual risk factors.162 In addition, Framingham investigators have reported limited usefulness for CIMT in this prediction.163
Robotic bronchoscopy: potential in diagnosing and treating lung cancer
Published in Expert Review of Respiratory Medicine, 2023
Jennifer D. Duke, Janani Reisenauer
Another landmark study supporting lung cancer screening was the NELSON trial published in 2020. This randomized trial compared LDCT screening at increasing intervals (baseline study and additional screenings at years 1.0, 3.0, and 5.5) versus no screening of 15,789 current or former smokers aged 50 to 74 (84% male) in Europe [4]. The average adherence to CT screening was 90.0% over the 10-year follow-up period. At 10 years of follow-up, the incidence of lung cancer was 5.58 cases per 1000 person-years in the screening group and 4.91 cases per 1000 person-years in the control group; lung-cancer mortality was 2.50 deaths per 1000 person-years and 3.30 deaths per 1000 person-years, respectively. The cumulative rate ratio for death from lung cancer at 10 years was 0.76 (95% confidence interval [CI], 0.61 to 0.94; P = 0.01) in the screening group as compared with the control group, demonstrating that lung-cancer mortality was significantly lower among those who underwent volume CT screening than among those who underwent no screening [4]. The NELSON trial was not powered to detect differences in all-cause mortality unlike the NLST trial.
A Combination of Preoperative Computed Tomography-Defined Sarcopenia and Systemic Inflammation on Survival in Patients with Poorly Differentiated Neuroendocrine Neoplasms Following Radical Resection
Published in Nutrition and Cancer, 2022
Jie Jia, Xiangyu Zeng, Chengguo Li, Lei Yang, Yongzhou Huang, Xin Tong, Qi Jiang, Peng Zhang, Kaixiong Tao
Abdominal CT scans were routinely performed within 7 day prior to surgery. Two adjacent axial images within the same series at the third lumbar vertebra (L3) were selected to analyze the total muscle cross-sectional area and an average was taken. All CT examinations were performed with one of the following three scanners: dual source CT scanner (SOMATOM Definition, Siemens, Germany),64-detector spiral CT scanner (SOMATOM Definition AS+, Siemens, Germany), 320-row dynamic volume CT scanner (Aquilion One, Toshiba, Japan). Images were reconstructed into soft tissue window with a slice thickness of 1.5 mm or 2 mm and an interval of 1.5 mm or 2 mm, respectively. Two independent, trained researchers used ImageJ software (National Institutes of Health, Washington, MD, USA) to measure the L3 total cross-sectional skeletal muscle area (SMA). The skeletal muscle mass index (SMI cm2/m2) was calculated by dividing the L3 SMA (cm2) by the height squared (m2). According to Martin et al.’s definition, sarcopenia was defined as an SMI <43 cm2/m2 for men with body mass index (BMI) <25 kg/m2, an SMI <53 cm2/m2 for men with a BMI ≥25 kg/m2, and an SMI <41 cm2/m2 for women (19).
Factors predicting the occurrence of aortic valve calcification in patients with coronary artery calcification in China
Published in Acta Cardiologica, 2022
Shou-Quan Cheng, Nai-Feng Liu, Li-Juan Fang, Min Li
CT imaging was performed using a 320-row-detector dynamic volume CT (GE Revolution; General Electric, Boston, MA, United States). All CT coronary angiography studies were evaluated by at least two certified assessors (a cardiologist and a radiologist). CAC was defined as calcification along the coronary artery. AoVC was defined as calcium deposition in the main aortic valve or nodular deposition in the aortic valve ring. MVC was defined as calcium deposits in the mitral ring and/or lobe area. All CCTA images were visually evaluated for aortic or mitral/annular calcification [15]. A qualitative assessment of aortic and mitral calcifications was performed based on non-contrast CT imaging using the Agatston score [16]. A threshold of 130 Hounsfield units was used to identify the calcifications.