Evaluation of surface dose and image quality using the half-scan mode in chest computed tomography-guided...

The authors aimed to evaluate the effects of the half-scan mode on image quality and physician exposure to radiation in computed tomography (CT)-guided interventional radiology (IVR) to the right lung using an intermittent CT fluoroscopy technique for measuring phantom surface dose distribution and image noise. For the half-scan mode, settings at 0°, 90°, 180°, and 270° were used as the central axis of the X-ray exposure range on the chest phantom. With the center of the ventral side in the chest phantom defined as 0°, optically stimulated luminescent dosimeters were attached at five positions at 30° intervals on the right side of the phantom surface. Securing a space for device operation during the procedure is necessary. The couch was shifted downward by 50 mm to reproduce the conditions used for measurement in clinical settings. Image noise and contrast-to-noise ratio were measured to assess image quality; subjective evaluation was performed using simulated lung nodules placed in the phantom. The phantom surface dose distribution in the measured half-scan mode depended on the angle setting. Additionally, the phantom surface dose in the half-scan mode at the 90° setting was reduced by approximately 50%; however, image quality was clearly decreased. In CT-guided IVR to the right lung, using a lead drape and half-scan mode according to the procedural situation is important.