{"entity":{"id":"spect-dosimetry-workflow","kind":"technology","name":"SPECT dosimetry workflow for radionuclide therapy","aka":["post-therapy dosimetry","EANM dosimetry SOP"],"tldr":"After a radioactive treatment injection, patients are scanned two or three times over about a week so doctors can calculate exactly how much radiation dose the tumour and organs like the kidneys actually received, and adjust future doses if needed.","summary":"Clinical radionuclide-therapy dosimetry follows a standard sequence: sequential quantitative SPECT/CT (or hybrid planar-plus-SPECT/CT) imaging at multiple time points after administration, segmentation of source organs and tumours, fitting of time-activity curves to obtain the time-integrated activity in each region, and conversion to absorbed dose using either organ-level S-values (MIRD/OLINDA formalism) or voxel-level convolution/Monte Carlo methods. The EANM Dosimetry Committee's standard operational procedures, most recently the 2022 guideline for 177Lu-labelled somatostatin-receptor- and PSMA-targeting ligands, recommend using the same SPECT/CT system throughout a patient's dosimetry study, medium-energy collimators for 177Lu, iterative reconstruction with CT-based attenuation, scatter and (where available) collimator-response correction, and 60-120 projection angles at roughly 30-40 seconds per projection.\n\nFor kidney dosimetry, the guideline recommends three SPECT/CT acquisitions between 24 hours and 7 days after the first therapy cycle (with at least two days between the final two time points), reducing to a single acquisition at a matched time point for subsequent cycles, with the region of interest drawn to include the full renal cortex and medulla but exclude the pelvis. Tumour dosimetry follows a similar multi-time-point protocol, placing particular weight on a late imaging time point because tumour retention is typically slower than that of normal organs. A minimum of three time points is generally advised to characterise each exponential phase of the time-activity curve; two or three points at around 2, 4 and 24 hours are often sufficient for many source organs, but bone marrow and whole-body kinetics may need additional early sampling. Related standard operational procedures exist for 131I-mIBG neuroendocrine tumour therapy and for 90Y radioembolisation (99mTc-MAA pre-therapy and 90Y peri-therapy dosimetry).","asOf":"2026-09-22","links":[{"label":"EANM dosimetry committee recommendations for dosimetry of 177Lu-labelled SSTR- and PSMA-targeting ligands (Eur J Nucl Med Mol Imaging 2022)","url":"https://link.springer.com/article/10.1007/s00259-022-05727-7"},{"label":"PMC full text of the EANM 177Lu dosimetry recommendations","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC9015994/"},{"label":"EANM guidance document: dosimetry for first-in-human studies and phase 0/1 clinical trials (PMC 2024)","url":"https://pmc.ncbi.nlm.nih.gov/articles/PMC10957710/"},{"label":"EANM: Radionuclide therapy management technologist guide","url":"https://eanm.org/wp-content/uploads/2024/06/EANM22_TechGuide.pdf"}],"tags":["dosimetry","clinical protocol","PRRT"],"related":["quantitative-spect","monte-carlo-dosimetry","radioligand-dosimetry","prrt","lu177-radioligand-therapy","tc-99m","lu-177","i-131","y-90"],"indications":[],"sections":[],"technologies":[],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":["quantitative-spect","monte-carlo-dosimetry"],"notes":[],"principle":"The patient is scanned with quantitative SPECT/CT at several defined time points after the therapy injection so that a time-activity curve can be fitted for each organ and tumour; integrating that curve gives the total number of decays in each region, which is then converted into an absorbed radiation dose using standardised organ- or voxel-level conversion factors.","strengths":[],"limitations":[],"since":"First EANM dosimetry SOPs (radioiodine) 2008; MIRD Pamphlet 26 on quantitative 177Lu SPECT dosimetry 2016; PRRT/PSMA-specific guideline 2022"},"route":"/technologies/spect-dosimetry-workflow/","neighbours":{"technology":[{"id":"lu177-radioligand-therapy","kind":"technology","name":"Lutetium-177 radioligand therapy","route":"/technologies/lu177-radioligand-therapy/"},{"id":"monte-carlo-dosimetry","kind":"technology","name":"Monte Carlo dosimetry","route":"/technologies/monte-carlo-dosimetry/"},{"id":"prrt","kind":"technology","name":"Peptide receptor radionuclide therapy (PRRT)","route":"/technologies/prrt/"},{"id":"quantitative-spect","kind":"technology","name":"Quantitative SPECT","route":"/technologies/quantitative-spect/"},{"id":"radioligand-dosimetry","kind":"technology","name":"Radioligand dosimetry","route":"/technologies/radioligand-dosimetry/"}],"isotope":[{"id":"i-131","kind":"isotope","name":"Iodine-131","route":"/isotopes/i-131/"},{"id":"lu-177","kind":"isotope","name":"Lutetium-177","route":"/isotopes/lu-177/"},{"id":"tc-99m","kind":"isotope","name":"Technetium-99m","route":"/isotopes/tc-99m/"},{"id":"y-90","kind":"isotope","name":"Yttrium-90","route":"/isotopes/y-90/"}]}}