Application of a mobile C-arm fluoroscopy system to bone densitometry by utilizing a dual energy X-ray spectrum

We examined the dual energy X-ray spectrum necessary for bone mineral measurements in a mobile fluoroscopic C-arm. We used a dual kVp (peak kilovoltage) exposure and a low-energy absorption filter. Tube voltages were chosen as 40 kVp and 70 kVp for the measurement of the bone mineral density (BMD) on peripheral sites, and copper sheets were used as low energy absorption filters. Spectra were measured with a pin-hole collimator and YAP : Cc scintillation detector and were compared to those calculated by using the SPECT-78 program. Bone mineral densities were measured with different thicknesses of aluminum and acryl that simulated bone and soft tissue, respectively. The dual energy X-ray spectrum measured at 40 kVp and 70 kVp with a 0.5-mm copper filter was similar in shape to the calculated one. The BMD obtained from the dual energy Xray source and the C-arm system was highly linear and was independent of the soft tissue thickness. The precision errors for the measured BMD were within 1 %.X111sciescopuskc