Dados do Trabalho

Título

Functional and Pseudo-Diffusion Magnetic Resonance Imaging for Stereotactic Radiosurgery Planning

Descrição sucinta do(s) objetivo(s)

Advanced imaging biomarkers, such as IntraVoxel Incoherent Motion (IVIM) perfusion (Fig. 1) and resting-state functional Magnetic Resonance Imaging (rs-fMRI), could improve precision of Stereotactic Radiosurgery (SRS) and Stereotactic Body Radiation Therapy (SBRT). These methods could enhance target volume delineation and preservation of Organs At Risk (OARs), optimizing treatment efficacy. In Prostate Cancer (PCa), SBRT with simultaneous integrated boost (SIB) could leverage IVIM derived parameters —diffusion (D), vascular volume fraction (f) and microcapillary perfusion (D*)— to refine target characterization and deliver high doses to specific areas. For brain tumors (BrT), rs-fMRI combined with white matter segmentation allows improved OARs protection by identifying neural networks critical to cognitive and motor functions. This project aims to simulate the implementation of IVIM and rs-fMRI in SRS planning and assess their efficacy compared with standard planning techniques.

Material(is) e método(s)

Twenty-one patients (12 PCa and 9 BrT) underwent imaging on a 3 T MRI scanner. For PCa, an IVIM protocol (Fig. 2) was implemented and pseudo-diffusion images were processed using a custom Python-based algorithm (Fig. 3), facilitating the delineation of Gross Tumor Volume (GTV) and Planning Target Volume (PTV). In BrT cases, rs-fMRI was employed to map Resting-State Networks (RSNs) using an independent component analysis method. Treatment plans were generated using Volumetric Modulated Arc Therapy (VMAT), assessing dosimetric impact through isodose curves and dose-volume histograms (Fig. 4). Comparative analyses were performed between IVIM/rs-fMRI-based plans and conventional VMAT protocols to evaluate differences in GTV coverage and OARs dose exposure.

Resultados e discussão

For PCa, IVIM-integrated SIB-SBRT demonstrated enhanced GTV delineation, allowing precise tumor boundary definition. Some OARs (urethra, bladder, rectum) exhibited increased maximum dose (5-39%). GTV coverage improved while respecting OARs dose constraints compared to conventional VMAT treatment. In BrT, RSNs were successfully integrated into the treatment planning system (Fig. 5), facilitating optimized neural pathway preservation. Isodose distribution analysis confirmed precise target coverage.

Conclusões

The integration of IVIM and rs-fMRI into SRS and SBRT simulations demonstrates potential for enhancing treatment precision, improving tumor targeting, and minimizing toxicity (BrT). This methodology offers a patient-specific radiotherapy planning, particularly for PCa and BrT. Future studies incorporating PSMA-PET/MR and tractography could refine treatment strategies, enhancing clinical outcomes.

Palavras Chave

IntraVoxel Incoherent Motion; Resting-State functional Magnetic Resonance Imaging; Radiotherapy Planning

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