Exposure levels from radiology procedures used in myeloma diagnostics

Purpose: Myeloma diagnostics have traditionally been performed using a radiographic skeletal survey. CT scanning has been suggested as a replacement and has been introduced in our institution. Effective doses have been reported in the literature, without correlation with body mass index (BMI). We have evaluated the effective doses imparted to the patients during this procedure.Methods and Materials: Length, weight and dose-length product were collected for each patient and CT examination. Conversion factors based on BMI were generated using Monte Carlo based simulations on voxel-based phantoms (n=5). For each phantom size a sex and BMI-specific conversion factor was generated. Subsequently individual conversion factors were generated through exponential curve fitting. Finally, the effective dose was calculated for each patient based on sex and BMI.Results: The sex averaged conversion factors for underweight, normal weight and obese patients (BMI = 18, 21 and 25, respectively) were 0.011, 0.011 and 0.010 mSv/mGycm, respectively. The median effective dose for a scan length from the top of the head to the knees was 5.1 mSv (n=256, range = [2.7, 12.6]) for all patients. Dose levels in our institution are comparable with published data but higher than for conventional skeletal imaging.Conclusion: CT scanning for myeloma diagnostics in our institution showed higher doses than has been published for conventional skeletal imaging but is still comparable to other investigations into this methodology. The advantages in terms of shorter examination times are perceived to be positive for the predominantly elderly patients where dose concerns are of less importance. (Less)