Clinical implementation of PLANET® Dose for dosimetric assessment after [177Lu]Lu-DOTA-TATE: comparison with Dosimetry Toolkit® and OLINDA/EXM® V1.0

Abstract

Background The aim of this study was to compare a commercial dosimetry workstation (PLANET® Dose) and the dosimetry approach (GE Dosimetry Toolkit® and OLINDA/EXM® V1.0) currently used in our department for quantification of the absorbed dose (AD) to organs at risk after peptide receptor radionuclide therapy with [177Lu]Lu-DOTA-TATE. Methods An evaluation on phantom was performed to determine the SPECT calibration factor variations over time and to compare the Time Integrated Activity Coefficients (TIACs) obtained with the two approaches. Then, dosimetry was carried out with the two tools in 21 patients with neuroendocrine tumours after the first and second injection of 7.2 ± 0.2 GBq of [177Lu]Lu-DOTA-TATE (40 dosimetry analyses with each software). SPECT/CT images were acquired at 4 h, 24 h, 72 h and 192 h post-injection and were reconstructed using the Xeleris software (General Electric). The liver, spleen and kidneys masses and TIACs were determined using Dosimetry Toolkit® (DTK) and PLANET® Dose. The ADs were calculated using OLINDA/EXM® V1.0 and the Local Deposition Method (LDM) or Dose voxel-Kernel convolution (DK) on PLANET® Dose. Results With the phantom, the 3D calibration factors showed a slight variation (0.8% and 3.3%) over time, and TIACs of 225.19 h and 217.52 h were obtained with DTK and PLANET® Dose, respectively. In patients, the root mean square deviation value was 8.9% for the organ masses, 8.1% for the TIACs, and 9.1% and 7.8% for the ADs calculated with LDM and DK, respectively. The Lin’s concordance correlation coefficient was 0.99 and the Bland–Altman plot analysis estimated that the AD value difference between methods ranged from − 0.75 to 0.49 Gy, from − 0.20 to 0.64 Gy, and from − 0.43 to 1.03 Gy for 95% of the 40 liver, kidneys and spleen dosimetry analyses. The dosimetry method had a minor influence on AD differences compared with the image registration and organ segmentation steps. Conclusions The ADs to organs at risk obtained with the new workstation PLANET® Dose are concordant with those calculated with the currently used software and in agreement with the literature. These results validate the use of PLANET® Dose in clinical routine for patient dosimetry after targeted radiotherapy with [177Lu]Lu-DOTA-TATE.

Data-driven gated PET/CT: implications for lesion segmentation and quantitation

“…Lesion volumes were not affected by changes in registration, but the gating process from DDG reduces volume. The typical amount of volume decrease observed in this study was larger than, but still similar to, previous work on DDG-PET [ 11 , 25 , 26 , 35 ]. The larger changes in volume observed in this work may result from this study’s selection bias—only prospectively identified cases with clinically relevant misregistration.…”

“…Some prior DDG-PET studies have typically noted an approximate increase in SUV max of 10% from the DDG process [ 11 , 25 , 35 ], whereas in another study the DDG-PET method most closely resembling ours used here led to an approximate increase of 20% [ 15 ]. A very recent study that used the same DDG-PET method as here, but with an EE breath-hold CT protocol, found very similar increases in SUV max as observed here for DDG-PET (~ 25%) [ 26 ].…”

“…Our goal here was to ensure this study used data from consecutive patients that had received the DDG PET/CT protocol, and therefore, we did not make any specific selections on the basis of radiotracer. Recent work has shown that the use of DDG-PET as applied in this study (GE’s Q.Static, using a motion threshold) can be affected by specific radiotracers [ 26 ]. The DDG-PET/CT approach implemented here is enabled by a prospective cine-CT that is initiated only when PET/CT misregistration is identified in the clinic.…”

“…The DDG-PET/CT approach implemented here is enabled by a prospective cine-CT that is initiated only when PET/CT misregistration is identified in the clinic. It is not a fully prospective DDG protocol as discussed or used in previous work [ 11 , 13 , 25 , 26 ]. Another limitation is therefore the inherent selection bias for cases studied here.…”

“…As DDG-PET continues to gain in clinical use, EDG-based methods for CT will become impractical to match with DDG-PET, requiring equally capable techniques for DDG-CT [ 10 , 16 , 22 – 24 ]. Some other recent work has combined prospective DDG-PET with end-expiration (EE) breath-hold CT to progress toward better matching between DDG-PET and CT [ 25 , 26 ].…”