The effect of mAs variation upon computed tomography image quality as evaluated by in vivo and in vitro studies.

Abstract

The effect of different mAs settings on computed tomobraphy (CT) image quality was evaluated by a clinical study and phantom studies. In the clinical portion of this study, a number of CT images, obtained at various mAs settings, were reviewed by experienced CT interpreters. From these same images, graphs were charted of the root-mean-standard deviation (RMSD) vs. body size; there appeared to be a linear relationship between noise, as measured by RMSD, and body size. A performance phantom was used to evaluate the effect of the different mAs settings on resolution. There was some loss in low contrast resolution at 6 and 20 mAs; however, the resolution was identical at 40 and 100 mAs.

Patient-specific Radiation Dose and Cancer Risk for Pediatric Chest CT

“…However, the results of this study show that chest diameter or circumference is a stronger predictor of dose and risk than weight and body length and should perhaps replace the other body size indexes for the purpose of protocol design and assignment. This is in line with the recommendation of Haaga et al ( 35 ) and Haaga ( 36 ), who advocated the use of patient diameter to determine parameters such as tube current.…”

Radiation dose reduction in pediatric CT

“…The Victoreen-AAPM Test Object (Victoreen, Nuclear Associates, Carle Place, NY) with water insert was scanned with a Picker 600 CT (Picker International, Cleveland, OH) unit at 130 KVP, extended scan angle of 398 °, and scan time of 1.8 s for tube currents of 5, 35, 65, 95, 125 and 155 mA at 10-mm slice increments to simulate abdominal CT images, The images were reconstructed using a high resolution algorithm on a 256 x 256 image matrix. The image noise, taken as the standard deviation (SD) of the CT numbers from regions of interest in areas of pure water, was plotted against mAs ( Fig.…”

CT-Guided Lumbar Nerve Root Injections: Are We Using the Correct Radiation Dose Settings?

“…11,12 Although body weight is a more frequent measure of body size, several researchers favor the use of cross-sectional diameter, in a similar manner to our study, because it correlates with the distance of the pathway traversed by the x-ray beam, and is also easy to measure on the scout image before the procedure. 13,14 After identifying patients of smaller body habitus, the next clinically relevant step is to prescribe the most optimal low tube current. The lowest absolute tube current in our cohort of 80 patients was 20 mA and the lowest mean tube current by a proceduralist in our study was 42 mA.…”