Effective dose to patients from bone densitometry

Tissue or Organ doses for bone densitometries with dual energy X-ray absorptiometry (DXA) and single energy quantitative computed tomography (SEQCT) were determined with two types of thermoluminescent dosimeters embedded in a Rando Phantom. The dose measurements were performed under the condition according to the common clinical use. In DXA, the resultant effective dose per examination was 8.5 μSv for male and 14.6 μSv for female. In SEQCT, the effective dose per examination for both sexes was 0.5 mSv at 80kV, 1.3mSv at 120kV, and 2.2 mSv at 140 kV, respectively. The effective dose for male was lower than that for female by a few percent. The merits between DXA and SEQCT and between different voltages were discussed by taking into account the effective dose and the medical information obtainable. In conclusion, if there was no significant difference between diagnostic abilities of DXA and SEQCT, DXA should be preferable to SEQCT. However, CR and CT images with high- quality are also obtained with SEQCT, and these images give us clinically useful additional information which cannot be available with DXA. The results also showed that SEQCT with lower tube voltage was preferable to that with higher tube voltage because of the lower effective dose. (author)