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The purpose of this study was to obtain information on optimum exposure parameter combination on simulated thorax and abdomen examinations using Direct-Digital Radiography (DR) and Computed Radiography (CR) systems. An in-house phantom dedicated for quick QC was utilized as an image quality quantification tool in term of contrast. The optimization was performed on Philips Essenta DR, CR Fuji Profect CS, and CR Agfa 10-X. Exposures were performed using corresponding clinical setting with combinations of kVp, mAs, filters, and a variation of simulated patient thicknesses. The Figure of Merit (FOM) was employed as optimization parameter, calculated as ratio of squared Signal Difference to Noise Ratio (SDNR) and surface dose for every measurement. The image quality was evaluated using Modulation Transfer Function (MTF) and Contrast Consistency (CV). Based on FOM, MTF, and CV calculations, acquisitions optimization for thorax examination using DR was obtained on 55-63 kVp, 5-8 mAs, with additional filter 1 mm Al + 0.1 mm Cu. For abdomen examination, the optimized results were 81-102 kVp, 8-12.5 mAs, with additional filters 1 mm Al+0.1 mm Cu and 1 mm Al+0.2 mm Cu. On the other hand, the optimized results using CR on thorax examination were on the range of 55-63 kV, 4-8 mAs, also with the same additional filters with DR. The results of optimization of abdomen examination were on the range of 85-102 kV, 8-20 mAs, and again with the same additional filters. This gave information that different receptors used on the same x-ray unit produced almost similar optimization conditions.

In this study, two CR receptors (Agfa CR-85X and Agfa CR-10X) and two DDR receptors (Brivo DR-F and Essenta) were characterized in terms of detector sensitivity and image quality. An in-house phantom was specially designed to accommodate image quality assessment for quick QC and is tested as a purpose of this study. The reference quantitative aspect that were used to characterize the imaging units are the correlation between Pixel Value and image receptor dose, whereas evaluation of image quality based on the modules on the in-house phantom uses new proposed metrics (coefficient of linearity, CL, and coefficient of variance, CV). Each system’s unique Pixel Value-dose characteristics are also expressed in the results of the in-house phantom’s metrics (i.e. CL and CV). In addition, the constancy of measured modulation transfer function suggests potential use for system quality judgment. As all characterizations (Pixel Value-dose characteristics, MTF, and new metrics) indicated on unique result for each systems, the study implies that the designed in-house phantom as well as its proposed metric can be promising to be used to characterize digital radiography systems during quick QC.

Computed Tomography (CT) is an x-ray modality for scanning organ in three dimensional images. Image acquisition is performed by rotating x-ray tube that match with table movements, there by the tube can cover patient body in a spiral scan. Patient table movements by gantry rotation divided by the width of the collimator on the isocenter is known as a pitch, which affects the image quality and radiation dose in the patient. A dose distribution profile has been observed along the z-axis of the in-house thorax phantom simulation in an elliptical cylinder form with the size of 28 cm x 21 cm and 22 cm length. Phantom was equipped with a lung simulation object using a cork with a Hounsfield Unit (123.1 HU), a spine using Teflon material (918.6 HU), and 9 bar and a cylinder to place 1 cm x 25 cm gafchromic films. The position of the film was marked with point position 1 – 9 for the series of coordinates (0,0), (5, 0), (10, 0), (-5, 0), (-10, 0), (0, 4), (0, 8), (0, -4), (0, -8) cm. The phantom images were performed with an exposure condition by 120 kV, 100 mAs and pitch variations (0.8, 1.0 and 1.5). The minimum dose occured at the beginning and end of the scan for all profiles and pitch values. The average dose of lung material (1, 2, 4, and 5) in the range 2.32-2.88 mGy for pitch 0.8 and 1.0 respectively, and 2.25 -2.68 mGy for pitch 1.5. The dose in lung was relatively lower compared to the dose in soft tissue and bone. The maximum dose does not always occur in the middle of the z-axis, but it was fluctuated as it was influenced by the pitch values in the range of 10 - 12 cm. It can be concluded that the use of pitch 0.8 and 1.0 did not provide a significant dose difference and reduced the average dose on pitch 1.5. Moreover, the maximum dose does not always occur in the middle of the z-axis due to an isotropic material.