Impact of Software Parameter Settings on Image Quality of Virtual Grid Processed Radiography Images

Abstract

Objectives Mobile radiography systems are commonly used in the intensive care unit. The use of a physical antiscatter grid with these systems is uncommon because of drawbacks. In 2015, Virtual Grid (Fujifilm, Tokyo, Japan) became available for chest and abdomen examinations. In this study, we compared image quality (IQ) with a contrast-detail phantom (CDRAD 2.0; Artinis Medical Systems, Zetten, the Netherlands) of digital radiographs acquired without any grid (gridless) with those corrected for scatter by either software (SW)-based scatter correction (Virtual Grid) or a physical grid (grid). Furthermore, we determined the optimal Virtual Grid settings that lead to the best contrast-detail IQ score (inverse IQ figure). Materials and Methods Images were obtained with a cassette spot film device with an inserted portable flat-panel detector (Fujifilm, Tokyo, Japan). The CDRAD phantom was sandwiched between polymethylmethacrylate (PMMA) with total thicknesses of 12, 16, 21, and 26 cm to simulate patient attenuation and scatter. Tube voltages of 81, 90, 109, and 125 kVp were used to make the radiographs. In total, 12 different Virtual Grid settings (grid ratio, line pairs (lp)/cm, and type of interstitial material) were applied for every phantom thickness and tube voltage. Results An average increase of 32% in IQ was obtained when Virtual Grid images with a SW grid ratio 10:1 were compared with gridless images (P < 0.001). Increasing the SW grid ratio to 20:1 resulted in a further increased IQ. With a phantom thickness of 12 cm PMMA, Virtual Grid outperformed the removable physical grid presented in the cassette spot film device. The linear mixed-effects model showed that IQ is mainly affected by PMMA, tube voltage, and the SW grid ratio. Conclusions Virtual Grid improves images obtained without physical grid for a wide range of experimental conditions. Despite the different possible settings of the Virtual Grid SW, the most important parameter affecting IQ is the SW grid ratio.

Characterizing Scatter Correction Software of 5 Mobile Radiography Units

“…The effects on the IQ of changing the SC SW grid ratio is also described in our former article. 7 Further research should be performed to investigate if our current results are applicable to other grid characteristics.…”

“…The IQ of radiographs obtained at bedside is often compromised because of the lack of use of the physical scatter rejection grid. Because the first SC SW applications were released in 2015, multiple SC SW products have become available to improve the IQ of bedside gridless images 7 . To our knowledge, no studies of intercomparisons of different mobile radiography systems with the possibility to apply such software on the images have been published.…”

“…We recently reported on a study 7 that was conducted with a contrast-detail phantom and Virtual Grid (Fujifilm, Tokyo, Japan) software where the IQ of the SC SW images could approximately be the same as the physical grid images depending on the experimental conditions. The previously cited articles/white papers conclude that SC SW improves chest radiographs and dose reduction should be possible to obtain radiographs without IQ loss.…”

Efficacy of the scatter correction algorithm in portable chest radiography

“…To overcome these practical constraints, several scatter correction post-processing algorithms (SCA) have been developed for use with portable radiography units, intending to reduce the effects of scattered radiation on IQ, including the Philips “Skyflow” [ 19 – 23 ], Fuji “Virtual Grid Software” [ 24 – 26 ], and Shimadzu SCA [ 27 ]. The detailed technical information in the Shimadzu SCA “White-Paper” is limited.…”

“…Both “Skyflow” and “Virtual-Grid” software have been shown to improve the IQ in phantom and clinical images [ 19 – 26 ]. However, no studies assessing the efficacy of the Shimadzu SCA have been published.…”