Comparison of conventional and through glass portable chest computed radiography: A Phantom study

Background: Since the outbreak of COVID-19, modified hospital unit or area for chest radiography of positive cases have become necessary. To date, relatively few studies have been investigated on the effects of portable chest radiography through glass barrier. Objectives: Our goal was to evaluate exposure technique and radiation dose between conventional and through glass portable chest computed radiography. Materials and methods: Experiments using an anthropomorphic phantom were performed for acquired portable chest PA radiography at SID 180 cm with glass door being open and closed. The EI and DI values were optimized to provide the appropriate exposure technique for glass barrier. Entrance surface air kerma and scatter survey were made to assess the radiation dose both inside and outside the room. Finally, HVL measurement of primary X-ray beam and after transmission through glass were determined. Results: Based on the fixed kVp and mAs technique, the EI value with glass barrier was less than the EI without the glass. Imaging through glass barrier showed the average EI reduction of 10.4% for Carestream and 37% for Konica. The average entrance surface air kerma reduction was 56.6% over a range of 90-120 kVp. The appropriate exposure technique for conventional portable chest PA using computed radiography was 100 kVp 2.5 mAs. With the same kVp setting, doubling the mAs is required for imaging through glass barrier to produce good diagnostic image quality (100 kVp and 4.0 mAs). The acceptable EI and DI ranges for CR used were EI=1742, DI=-0.02 (without glass) and EI=1795, DI=0.11 (with glass) for Carestream and EI=352, DI=-0.03 (without glass) and EI=373, DI=0.22 (with glass) for Konica respectively. The primary beam after transmission through the glass thickness 5 mm was 36%. The measured scatter of inside room compared to outside was very low at 1-2 meters. Increasing od HVL from 3.9 to 6.1 mm Al indicates the effect of beam hardening by glass. Conclusion: These experiments confirmed that through glass portable chest computed radiography are feasible and safe. The findings of this study have several practical implications which minimizes risk to radiographers during their work.