Dose from tomosynthesis of the bony anatomy: Comparison with digital radiography and CT

Abstract

Introduction Digital x-ray tomosynthesis can be employed to evaluate MSK/orthopedic conditions, such as revelation of subtle fractures, avoiding CT scan when standard exam is not sufficient. Purpose The purpose of this study is to evaluate effective doses from tomosynthesis of bony anatomy and compare them with doses from CT and digital radiography. Materials and methods We simulated tomosynthesis acquisitions of the hip, lumbar spine and shoulder using PCXMC20Rotation. Tomosynthesis projections were simulated using parameters from FujiFilm FDR AcSelerate with fixed mAs/projection, FID = 130 cm, 0.2 mm Cu filtration. For the same anatomical district, we also simulated radiographs with PCXMC2.0 and CT scans, performed on a Siemens Somatom Definition CT scanner, with CT-Expo (120 kVp, Z-current modulation). Effective doses were computed for all techniques. Results Hip tomosynthesis [60 projections (60° total angle), 5 mAs/projection, 80 kVp] delivers an effective dose of 0.8 mSv, 15 times the dose of an AP radiograph of the same anatomy and 20% of the dose delivered by CT [CTDI vol, mean = 9.5Gy]. Shoulder tomosynthesis [60 projections (60° total angle), 4mAs/projection, 65 kVp] delivers an effective dose of 0.4 mSv, 3 times the dose delivered by an AP radiograph of the same anatomy and 20% of the dose delivered by CT [CTDI vol, mean = 12Gy]. Finally, lumbar spine tomosynthesis [45 projections (40° total angle), 12.5 mAs/projection, 100kVp] delivers an effective dose of 1.8 mSv, 8 times the dose of a LL+AP radiograph and 22% of the dose delivered by CT [CTDI vol, mean = 17Gy]. Conclusion Dosimetric evaluation of radiographic tomosynthesis for bony anatomy shows that it spares 80% of the dose of a CT scan.