Dozimetrija pri radionuklidni terapiji nevroendokrinih tumorjev z Lu-177: primerjava 2D in 3D modela

Strnad, Gašper (author), Simončič, Urban (mentor), Tomše, Petra (comentor)

Terapija z radiofarmakom [177Lu]Lu-DOTA-TATE je učinkovit način zdravljenja pri pacientih, ki imajo nevroendokrine tumorje z izraženimi somatostatisnkimi receptorji. Fizikalne lastnosti razpada Lu-177 omogočajo dober terapevtski učinek in hkrati slikanje porazdelitve radiofarmaka po telesu. Na Kliniki za nuklearno medicino po aplikaciji radiofarmaka pri vsakem pacientu izvedejo planarno slikanje celega telesa z gama kamero po ustaljenem protokolu in z uveljavljenim 2D dozimetričnim modelom. V tej nalogi izvedemo primerjavo standardnega 2D modela z novim 3D modelom, ki na KNM predhodno še ni bil v uporabi. Cilji naloge zajemajo umeritev SPECT/CT kamere glede na parametre slikanja, razvoj protokola za dozimetrijo po 3D metodi, njegovo vrednotenje in primerjava s predhodnim modelom.. Pri pacientih se poleg planarnih slik po terapiji izvede še eno slikanje abdomna s SPECT/CT kamero. V okviru naloge smo z upoštevanjem popravka časovne odvisnosti aktivnosti iz SPECT/CT slik ustrezno skalirali krivulje časovne odvisnosti aktivnosti na osnovi planarnih slik. Z uporabo programske opreme, ki omogoča izračun doze po MIRD shemi smo izračunali prejete absorbirane doze pri pacientih, ki so na KNM prejeli to terapijo. Pri istih parametrih slikanja smo slikali še fantom in izvedli test kalibracije, prilagojen za potrebe te naloge. Primerjali smo izračune doz po 2D in 3D metodi, ter razlike med izračunom doze po MIRD shemi z dvema različnima programoma. Razlike v končnem rezultatu obeh metod so bile znatne, z povprečnim odstopanjem absorbirane doze za 31,5%. Raziskali smo vpliv volumna pacientovih kritičnih organov na rezultate dozimetrije in korelacijo med spremembo integrala časovne odvisnosti aktivnosti od časa, odstopanjem volumna organov od standardnih in pa izračunano dozo po 3D modelu.

• Language: Slovenian
• Keywords: dozimetrija, SPECT, gama kamera, radiofarmak, MIRD, lutecij
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FMF - Faculty of Mathematics and Physics
• Year: 2024
• PID: 20.500.12556/RUL-154444
• COBISS.SI-ID: 185273603
• Publication date in RUL: 15.02.2024

Secondary language

• Language: English
• Title: Dosimetry of radionuclide therapy of neuroendocrine tumors with Lu-177: comparison of 2D and 3D model

Abstract

Therapy with the radiopharmaceutical [177Lu]Lu-DOTA-TATE is an effective method for treating patients with neuroendocrine tumors expressing somatostatin receptors. The physical decay properties of Lu-177 allow for a good therapeutic effect and also imaging of the radiopharmaceutical distribution throughout the body. At the Department of Nuclear Medicine, after the administration of the radiopharmaceutical, whole-body planar imaging is performed on each patient using a gamma camera following an established protocol and a conventional 2D dosimetric model. In this study, we compare the standard 2D model with a new 3D model that has not been previously used at the Department of Nuclear Medicine. The objectives of the study include the calibration of the SPECT/CT camera in regards with our imaging parameters, development of a protocol for dosimetry using the 3D method, its evaluation, and a comparison with the previous model. In addition to planar images, patients undergo post-therapy abdominal imaging with a SPECT/CT camera. In the context of the study, we applied corrections for activity from SPECT/CT images on the time dependant activity curves obtained using planar images. Using the software that is intended to do dosimetry calculations according to the MIRD scheme, we computed the absorbed doses received by patients who underwent this therapy at the Department of Nuclear Medicine. Under the same imaging parameters, we conducted a phantom quantitative calibration test tailored to the needs of this study. We compared dose calculations using 2D and 3D methods, as well as differences in dose calculation using the MIRD scheme with two different softwares. The differences in the final results between the two methods were significant, with an average deviation of 31.5% in absorbed dose. We explored the influence of the volume of critical organs in patients on dosimetry results and the correlation between changes in the integral of the time-dependent activity curve over time, deviations from standard organ volumes, and the calculated dose using the 3D model.

• Keywords: dosimetry, SPECT, gamma camera, radiopharmaceutical, MIRD, lutetium