Distributions of scatter-to-primary and signal-to-noise ratios per pixel in digital chest imaging
1 Department of Radiation Physics, Linköping University, SE-581 85 Linköping, Sweden
2 Joint Department of Physics, The Royal Marsden NHS Trust, Fulham Road, London SW3 6JJ, UK
* Corresponding author: gusul{at}imv.liu.se
The aim of this work was to calculate distributions of scatter-to-primary ratios (
s/p) and signal-to-noise ratios per pixel (SNRp) in chest images. Such distributions may provide useful information on how physical image quality (contrast, SNR) is distributed over the posterior/anterior (PA) chest image. A Monte Carlo computer program was used for the calculations, including a model of both the patient (voxel phantom) and the imaging system (X-ray tube, anti-scatter grid and image detector). The calculations were performed for three PA thicknesses 20, 24 and 28 cm. For a 24 cm patient, the s/p varies between 0.5 in the lung to 2.5 behind the spine and heart. The corresponding variation of the SNRp is a factor of 3, with the highest values in the lung. Increasing the patient thickness from 20 to 28 cm increases the s/p by a factor of 2.2 behind the spine and heart.