Effects of Kilovoltage on Image Quality and Entrance Surface Dose in Lumbar Spine Digital Radiography

Digital radiography possesses a wide dynamic range and has a major advantage in producing an acceptable image of diagnostic value even though overexposure occurs. Lumbar spine (LS) radiography is the most common examinations that gives high radiation dose to patients and accounts for the highest collective population dose of any conventional radiographic examinations. As such, this study was carried out to ascertain the impact of image quality and entrance surface dose (ESD) with different exposure settings in the anteroposterior (AP) and lateral LS.

The torso of the PBU-50 phantom was exposed to medium and high kilovoltage peak (kVp). A total of 14 images for LS were obtained. Relative image quality was assessed using Leeds Test Objects TOR CDR whilst the ESD was ascertained using an optically stimulated luminescence dosimeter.

The results of Friedman test indicated a significant difference in image quality when using medium and high kVp. Wilcoxon signed-rank test also reflected a significant difference in ESD between the use of medium and high kVp for both AP and lateral LS.

Significant differences in image quality and ESD were obtained using medium and high kVp with medium kVp resulting in high contrast but low contrast sensitivity and vice versa. The findings of the present study indicated that the recommended kVp for AP LS was from 75kVp to 81kVp whilst for lateral LS the recommended kVp was from 85kVp to 90kVp for an average adult patient.