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Comparison of voxel-wise absorbed dose distributions derived from 177Lu-PSMA activity recovered by two SPECT reconstruction methods: OSEM and Astonish

2025Dissertação de mestrado Acesso aberto
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dc.contributor.authorAlmeida,Marta Maçarico Cardoso
dc.contributor.institutionFaculty of Sciences
dc.contributor.institutionDepartment of Physics
dc.contributor.supervisorFerreira,Paulo
dc.contributor.supervisorSampaio,Jorge Miguel de Brito Almeida
dc.date.accessioned2026-02-04T16:15:01Z
dc.date.available2026-02-04T16:15:01Z
dc.date.issued2025
dc.descriptionTese de mestrado, Engenharia Biomédica e Biofísica, 2025, Universidade de Lisboa, Faculdade de Ciências
dc.description.abstractRadioligand therapy (RLT) with [177Lu]Lu-PSMA is an emerging and effective treatment for metastatic castration-resistant prostate cancer (mCRPC), an advanced and aggressive stage of prostate cancer (PCa) in which the disease progresses despite androgen deprivation therapy (ADT). As with others targeted radionuclide therapies (TRT), there is significant inter-patient variability in treatment response and potential for toxicity, particularly to organs at risk (OARs). Therefore, accurate dosimetry assessment is essential to optimize therapeutic efficacy while minimizing adverse effects. Thus, to support the development of personalized dosimetry and assist clinicians in treatment planning, this study aimed to compare voxel-wise absorbed dose distributions (ADDs) derived from single photon emission tomography (SPECT) images reconstructed using two different methods. Since reconstruction algorithms can influence the quantification of radiopharmaceutical uptake, assessing their impact on dose estimation is essential. Fourteen patients undergoing [ 177Lu]Lu-PSMA therapy between December 2023 and February 2025 were included in this study, comprising a total of forty-eight treatments cycles. Post-treatment, SPECT imaging was performed at three time points, complemented by a single CT scan per cycle for attenuation correction. SPECT images were reconstructed using both OSEM and Astonish methods to allow comparative dosimetric analysis. OAR (left and right kidneys, liver and spleen) segmentation was performed automatically on the CT images. Absorbed dose rate distributions were obtained by convolution of the activity with dose-voxel kernel (DVK). The OpenDose3D and TotalSegmentator extensions of the open-source 3DSlicer software environment were used. On average, the kidneys received the highest absorbed doses among the OARs, both in absolute terms and normalized with the administered activity, while liver showed more homogeneous values and the spleen showed marked variability between patients. Despite modest systematic differences between OSEM and Astonish reconstructions, particularly for the kidneys, variability between patients was the dominant factor, emphasizing the need for individualized dosimetry.en
dc.formatapplication/pdf
dc.identifier.urihttp://hdl.handle.net/10400.5/116883
dc.language.isoeng
dc.subjectMetastatic Castration-Resistant Prostate Cancer
dc.subject177Lu-PSMA RLT
dc.subjectPersonalized Dosimetry
dc.subjectAbsorbed Dose
dc.subject3DSlicer
dc.titleComparison of voxel-wise absorbed dose distributions derived from 177Lu-PSMA activity recovered by two SPECT reconstruction methods: OSEM and Astonishen
dc.typemaster thesis
dspace.entity.typePublication
rcaap.rightsopenAccess

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