Dosimetry software Hermes Internal Radiation Dosimetry

from quantitative image reconstruction to voxel-level absorbed dose distribution

Abstract

Objective 

The aim of this work is to validate a software package called Hermes Internal Radiation Dosimetry (HIRD) for internal dose assessment tailored for clinical practice. The software includes all the necessary steps to perform voxel-level absorbed dose calculations including quantitative reconstruction, image coregistration and volume of interest tools.

Methods 

The basics of voxel-level dosimetry methods and implementations to HIRD software are reviewed. Then, HIRD is validated using simulated SPECT/CT data and data from ¹⁷⁷Lu-DOTATATE-treated patients by comparing absorbed kidney doses with OLINDA/EXM-based dosimetry. In addition, electron and photon dose components are studied separately in an example patient case.

Results 

The simulation study showed that HIRD can reproduce time–activity curves accurately and produce absorbed doses with less than 10% error for the kidneys, liver and spleen. From the patient data, the absorbed kidney doses calculated using HIRD and using OLINDA/EXM were highly correlated (Pearson’s correlation coefficient, r=0.98). From Bland–Altman plot analysis, an average absorbed dose difference of −2% was found between the methods. In addition, we found that in ¹⁷⁷Lu-DOTATATE-treated patients, photons can contribute over 10% of the kidney’s total dose and is partly because of cross-irradiation from high-uptake lesions close to the kidneys.

Conclusion 

HIRD is a straightforward voxel-level internal dosimetry software. Its clinical utility was verified with simulated and clinical ¹⁷⁷Lu-DOTATATE-treated patient data. Patient studies also showed that photon contribution towards the total dose can be relatively high and voxel-level dose calculations can be valuable in cases where the target organ is in close proximity to high-uptake organs.