Distance from x-ray beam affects magnification of single marker calibration in non-linear fashion

Abstract

Abstract Background Preoperative templating commonly employs the use of a pre-determined size of an external calibration marker used to estimate the size of the final implant. Due to positioning differences of the ball to the X-ray beam, the size of the final implant can be incorrect by several cups sizes. The purpose of this study was to quantify the changes in magnification of a 25mm ECM at several distances between the XR emitter and receiver. Methods We placed 25mm X-ray ball at 100mm distances from the X-ray beam emitter, from 112 to 612mm and measured the size of the external calibration marker on our Picture Archiving and Communication Systems (PACS). Results We found a non-linear size increase as the ECM was placed closer to the X-ray beam with the closest ECM at 612 mm from the plate 5 cup sizes larger than the ECM 112mm from the plate. Conclusion Position of the ECM from the X-ray plate increases the apparent size in a nonlinear fashion as it is moved farther form the x-ray detection plate and closer to the x-ray emitter.