A whole body dosimetry protocol for peptide-receptor radionuclide therapy (Prrt): 2d planar image and hybrid 2d+3d SPECT/CT image methods: Journal of Visualized Experiments

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Abstract

Peptide-receptor-radionuclide-therapy (PPRT) is a targeted therapy that combines a short-range energy radionuclide with a substrate with high specificity for cancer cell receptors. After injection, the radiotracer is distributed throughout the entire body, with a higher uptake in tissues where targeted receptors are overexpressed. The use of beta/gamma radionuclide emitters enables therapy imaging (beta-emission) and post-therapy imaging (gamma-emission) to be performed at the same time. Post-treatment sequential images permit absorbed dose calculation based on local uptake and wash-in/wash-out kinetics. We implemented a hybrid method that combines information derived from both 2D and 3D images. Serial whole-body images and blood samples are acquired to estimate the absorbed dose to different organs at risk and to lesions disseminated throughout the body. A single 3D-SPECT/CT image, limited to the abdominal region, overcomes projection overlap on planar images of different structures such as the intestines and kidneys. The hybrid 2D+3D-SPECT/CT method combines the effective half-life information derived from 2D planar images with the local uptake distribution derived from 3D images. We implemented this methodology to estimate the absorbed dose for patients undergoing PRRT with177Lu-PSMA-617. The methodology could, however, be implemented with other beta-gamma radiotracers. To date, 10 patients have been enrolled into the dosimetry study with177Lu-PSMA-617 combined with drug protectors for kidneys and salivary glands (mannitol and glutamate tablets, respectively). The median ratio between kidney uptake at 24 h evaluated on planar images and 3D-SPECT/CT is 0.45 (range:0.32-1.23). The comparison between hybrid and full 3D approach has been tested on one patient, resulting in a 1.6% underestimation with respect to full 3D (2D: 0.829 mGy/MBq, hybrid: 0.315 mGy/MBq, 3D: 0.320 mGy/MBq). Treatment safety has been confirmed, with a mean absorbed dose of 0.73 mGy/MBq (range:0.26-1.07) for kidneys, 0.56 mGy/MBq (0.33-2.63) for the parotid glands and 0.63 mGy/MBq (0.23-1.20) for submandibular glands, values in accordance with previously published data. © 2020 Journal of Visualized Experiments.
Original languageEnglish
JournalJ. Visualized Exp.
Volume2020
Issue number158
DOIs
Publication statusPublished - 2020

Keywords

  • Dosimetry
  • Hybrid dosimetry
  • Issue 158
  • Medicine
  • Protectors
  • PSMA
  • SPECT
  • Theragnostics
  • Whole-body planar imaging
  • dipeptide
  • lutetium
  • Lutetium-177
  • PSMA-617
  • radioisotope
  • receptor
  • single heterocyclic rings
  • adult
  • diagnostic imaging
  • human
  • male
  • metabolism
  • middle aged
  • neoplasm
  • radiometry
  • single photon emission computed tomography-computed tomography
  • three-dimensional imaging
  • Adult
  • Dipeptides
  • Heterocyclic Compounds, 1-Ring
  • Humans
  • Imaging, Three-Dimensional
  • Lutetium
  • Male
  • Middle Aged
  • Neoplasms
  • Radioisotopes
  • Radiometry
  • Receptors, Peptide
  • Single Photon Emission Computed Tomography Computed Tomography

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