Clinical Implementation of PLANET®Dose for Dosimetric Assessment after 177Lu-DOTATATE: Comparison with Dosimetry Toolkit® and OLINDA/EXM® V1.0

Abstract

Background: Recently, commercial software tools have become available for dosimetry evaluations in clinical settings. The aim of this study was to compare a commercial dosimetry workstation (PLANETâDose) and the dosimetry approach (GE Dosimetry Toolkit® and OLINDA/EXM® V1.0) currently used in our department for quantification of the absorbed dose in organs at risk after peptide receptor radionuclide therapy with 177Lu-DOTATATE.Methods: First, an evaluation on phantom, with data acquisition at 5 time points, was performed to determine the SPECT calibration factor variations over time and to compare the Time Integrated Activity Coefficients (TIACs) and absorbed doses obtained with the two tools. Then, the two tools were used for dosimetry evaluation in 21 patients with neuroendocrine tumours after the first and second injection of 7.2 ± 0.2 GBq of 177Lu-DOTATATE (40 dosimetry analyses with each software). SPECT/CT images were acquired at 4h, 24h, 72h and 192h after 177Lu-DOTATATE injection and were reconstructed using the Xeleris software (General Electric). The liver, spleen and kidney masses, TIACs and absorbed doses were calculated using i) GE Dosimetry Toolkit® (DTK) and OLINDA/EXM® V1.0 and ii) the Local Deposition Method (LDM) or Dose voxel-Kernel convolution (DK) on PLANETâDose. Results: With the phantom, the 3D calibration factors showed a slight variation (0.8% and 3.3%) over time and TIACs of 225.19h and 217.52h were obtained with DTK and PLANETâDose, respectively. In patients, the mean of the relative standard deviations was -1% for the organ masses, 5.6%, for the TIACs, and 4.4% for the absorbed doses. The Lin’s concordance correlation coefficient was 0.99 and the Bland-Altman plot analysis estimated that the difference of absorbed dose values between methods ranged from -0.58 Gy to 0.84 Gy for approximately 95% of the 40 dosimetry analyses. A difference of 2.2% was obtained between the absorbed doses to organs at risk calculated with LDM and DK (PLANETâDose). Conclusions: The absorbed doses to organs at risk obtained with the new workstation are concordant with those calculated with the currently used software and in agreement with the literature. These results validate the use of PLANETâDose in clinical routine for patient dosimetry after targeted radiotherapy with 177Lu-DOTATATE.

Effect of predicted lung mass versus fixed mass regimes on lung dose in SIRT (90Y)

“…Alternatively, voxel-based dosimetry has been developed as a trade-off method based on dose-point kernels. The dose kernels involve both self-dose and crossfire contribution between the voxels, however, assuming homogenous activity distribution in each voxel is still a drawback [19,20]. Moreover, the range of beta particles is almost voxel-sized making the local energy deposition method feasible use, however, this feasibility deteriorates in lung dose as the lung density is quite less than soft tissue.…”

Assessment of cross‐dose contributions from tumors within computational phantoms using a Geant4 radiation dosimetry tool exploiting hybrid analytical/voxelised geometries

“…7 User-friendly, accessible and extensively tested codes such as OLINDA/EXM 5 or IDAC-Dose 6 are widely used by the nuclear medicine community to estimate organ doses for new and for established radiopharmaceuticals. 8,9 In general, these software rely on the use of tabulated organ S-values estimated with Monte Carlo simulations for computational phantoms to estimate self -and cross-organ doses; they can also allow the estimation of self -dose to spherical tumors of various masses. However, since in these codes the spherical tumors are an independent geometry to the phantom, they do not allow the assessment of the contribution to the radiation dose received by the healthy organs from the activity localized in a tumor, or vice versa.…”