MR-CBCT image-guided system for radiotherapy of orthotopic rat prostate tumors

Abstract

Multi-modality image-guided radiotherapy is the standard of care in contemporary cancer management; however, it is not common in preclinical settings due to both hardware and software limitations. Soft tissue lesions, such as orthotopic prostate tumors, are difficult to identify using cone beam computed tomography (CBCT) imaging alone. In this study, we characterized a research magnetic resonance (MR) scanner for preclinical studies and created a protocol for combined MR-CBCT image-guided small animal radiotherapy. Two in-house dual-modality, MR and CBCT compatible, phantoms were designed and manufactured using 3D printing technology. The phantoms were used for quality assurance tests and to facilitate end-to-end testing for combined preclinical MR and CBCT based treatment planning. MR and CBCT images of the phantoms were acquired utilizing a Varian 4.7 T scanner and XRad-225Cx irradiator, respectively. The geometry distortion was assessed by comparing MR images to phantom blueprints and CBCT. The corrected MR scans were co-registered with CBCT and subsequently used for treatment planning. The fidelity of 3D printed phantoms compared to the blueprint design yielded favorable agreement as verified with the CBCT measurements. The geometric distortion, which varied between -5% and 11% throughout the scanning volume, was substantially reduced to within 0.4% after correction. The distortion free MR images were co-registered with the corresponding CBCT images and imported into a commercial treatment planning software SmART Plan. The planning target volume (PTV) was on average 19% smaller when contoured on the corrected MR-CBCT images relative to raw images without distortion correction. An MR-CBCT based preclinical workflow was successfully designed and implemented for small animal radiotherapy. Combined MR-CBCT image-guided radiotherapy for preclinical research potentially delivers enhanced relevance to human radiotherapy for various disease sites. This novel protocol is wide-ranging and not limited to the orthotopic prostate tumor study presented in the study.

Development and Validation of a Clinically Relevant Workflow for MR-Guided Volumetric Arc Therapy in a Rabbit Model of Head and Neck Cancer

“…We therefore evaluated our MR-guided RT approach using a single high dose to obtain proof-of-concept. While MR-guided RT has been reported in rat models of prostate, pancreas, and brain tumors [34][35][36], to the best of our knowledge, the potential of this approach has not been previously demonstrated in HNSCC. Our results also highlight the superior targeting ability of VMAT with minimal dose to OAR.…”

“…While we were able to achieve good co-registration to enable MR-guided treatment planning, we did not investigate the potential geometric distortions among the MR, CT and CBCT images. Future studies should evaluate and correct for these potential distortions to further improve the accuracy of MR-guided RT [35]. Second, our study was focused on evaluation of primary tumor response to RT.…”

Three‐dimensional printing in radiation oncology: A systematic review of the literature

“…While many studies acknowledged the need for 3D printing expertise for consistent fabrication of accurate interventions, few reports explicitly described methods to teach current providers how to effectively use, design, and evaluate 3D printing applications. 46,47 Additionally, there were few studies describing the workflow systems for efficiently incorporating 3D…”

A deep learning and Monte Carlo based framework for bioluminescence imaging center of mass-guided glioblastoma targeting

“…Furthermore, despite recent advances in precision imaging systems dedicated to small animals, current state-of-the-art systems deliver a substantial imaging radiation dose to achieve the highest resolution required for targeting (Verhaegen et al 2011). There have been several attempts to reduce the delivered dose by using magnetic resonance (MR) guided treatment planning (Gutierrez et al 2015, Chiu et al 2018, Vanhove and Goethals 2019. However, since this technology is not yet integrated into modern pre-clinical irradiation platforms, CT-MR registration is required, which causes geometric uncertainties (Verhaegen et al 2018).…”