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Master Thesis

Dosimétrie personnalisée en radiothérapie interne sélective : comparaison de la segmentation du volume perfusé basée sur le cone-beam CT versus la TEMP/TDM aux 99mTc-MAA

Abstract : Purpose: to compare the reliability and accuracy of the pre-treatment dosimetry predictions using cone- beam CT (CBCT) versus 99mTc-labeled macroaggregated albumin (MAA) SPECT/CT for perfused volume segmentation in patients with hepatocellular carcinoma treated by selective internal radiation therapy (SIRT) using 90Y-glass microspheres. Materials and methods: fifteen patients (8 men, 7 women) with a mean age of 68.3 ± 10.5 [SD] years (range: 47–82 years) who underwent a total of 17 SIRT procedures using 90Y-glass microspheres for unresectable hepatocellular carcinoma from December 2014 to June 2019 were retrospectively included. Pre-treatment dosimetry data were calculated from 99mTc-MAA SPECT/CT using either CBCT or 99mTc-MAA SPECT/CT to segment the perfused volumes. Post-treatment dosimetry data were calculated using 90Y imaging (SPECT/CT or PET/CT). The whole liver, non-tumoral liver, and tumor volumes were segmented on CT or MRI data. The mean absorbed doses of the tumor (DT), non-tumoral liver, perfused liver (DPL) and perfused non-tumoral liver were calculated. Intra- and interobserver reliabilities were investigated by calculating Lin’s concordant correlation coefficients (\uD835\uDF0Cc values). The differences (biases) between pre- and post-treatment dosimetry data were assessed using the modified Bland– Altman method (for non-normally distributed variables), and systematic bias was evaluated using Passing–Bablok regression. Results: the intra- and interobserver reliabilities were good-to-excellent (\uD835\uDF0Cc 0.80–0.99) for all measures using both methods. Compared with 90Y imaging, the median differences were 5.8 Gy (IQR: −12.7; 16.1) and 5.6 Gy (IQR: −13.6; 10.2) for DPL-CBCT and DPL-99mTc-MAA SPECT/CT, respectively. The median differences were 1.6 Gy (IQR: −29; 7.53) and 9.8 Gy (IQR: −28.4; 19.9) for DT -CBCT and DT -99mTc-MAA SPECT/CT respectively. Passing– Bablok regression analysis showed that both CBCT and 99mTc-MAA SPECT/CT had proportional biases and thus tendencies to overestimate DT and DPL at higher post-treatment doses. Conclusion: CBCT may be a reliable segmentation method, but it does not significantly increase the accuracy of dose prediction compared with that of 99mTc-MAA SPECT/CT. At higher doses both methods tend to overestimate the doses to tumors and perfused livers.
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https://dumas.ccsd.cnrs.fr/dumas-02975190
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Submitted on : Thursday, October 22, 2020 - 2:45:22 PM
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Manuel Martin. Dosimétrie personnalisée en radiothérapie interne sélective : comparaison de la segmentation du volume perfusé basée sur le cone-beam CT versus la TEMP/TDM aux 99mTc-MAA. Sciences du Vivant [q-bio]. 2020. ⟨dumas-02975190⟩

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