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Comparison of internal dose estimates obtained using organ‐level, voxel S value, and Monte Carlo techniques
Author(s) -
Grimes Joshua,
Celler Anna
Publication year - 2014
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4892606
Subject(s) - monte carlo method , voxel , dosimetry , nuclear medicine , internal dosimetry , internal dose , mathematics , medicine , physics , medical physics , statistics , radiology
Purpose: The authors’ objective was to compare internal dose estimates obtained using the Organ Level Dose Assessment with Exponential Modeling (OLINDA/EXM) software, the voxel S value technique, and Monte Carlo simulation. Monte Carlo dose estimates were used as the reference standard to assess the impact of patient‐specific anatomy on the final dose estimate.Methods: Six patients injected with 99m Tc‐hydrazinonicotinamide‐Tyr 3 ‐octreotide were included in this study. A hybrid planar/SPECT imaging protocol was used to estimate 99m Tc time‐integrated activity coefficients (TIACs) for kidneys, liver, spleen, and tumors. Additionally, TIACs were predicted for 131 I, 177 Lu, and 90 Y assuming the same biological half‐lives as the 99m Tc labeled tracer. The TIACs were used as input for OLINDA/EXM for organ‐level dose calculation and voxel level dosimetry was performed using the voxel S value method and Monte Carlo simulation. Dose estimates for 99m Tc, 131 I, 177 Lu, and 90 Y distributions were evaluated by comparing (i) organ‐level S values corresponding to each method, (ii) total tumor and organ doses, (iii) differences in right and left kidney doses, and (iv) voxelized dose distributions calculated by Monte Carlo and the voxel S value technique.Results: The S values for all investigated radionuclides used by OLINDA/EXM and the corresponding patient‐specific S values calculated by Monte Carlo agreed within 2.3% on average for self‐irradiation, and differed by as much as 105% for cross‐organ irradiation. Total organ doses calculated by OLINDA/EXM and the voxel S value technique agreed with Monte Carlo results within approximately ±7%. Differences between right and left kidney doses determined by Monte Carlo were as high as 73%. Comparison of the Monte Carlo and voxel S value dose distributions showed that each method produced similar dose volume histograms with a minimum dose covering 90% of the volume (D90) agreeing within ±3%, on average.Conclusions: Several aspects of OLINDA/EXM dose calculation were compared with patient‐specific dose estimates obtained using Monte Carlo. Differences in patient anatomy led to large differences in cross‐organ doses. However, total organ doses were still in good agreement since most of the deposited dose is due to self‐irradiation. Comparison of voxelized doses calculated by Monte Carlo and the voxel S value technique showed that the 3D dose distributions produced by the respective methods are nearly identical.