Low Dose Rate Brachytherapy (LDR-BT) is a technique for treating localized prostate cancer by implanting radioactive seeds. In conventional practice, the delivery of seeds is performed using transrectal ultrasonography (TRUS) imaging for implant guidance and checked using computed-tomography for post-implant dosimetry. In the case of TRUS, accuracy can be compromised due to sub-optimal imaging. Magnetic Resonance Imaging (MRI), however, is known to provide better soft-tissue contrast, therefore, increasing the ability to detect small lesions; for that reason, the integration of intraoperative MRI in BT workflows has been investigated over the last two decades. The fusion of preoperative MR-images during TRUS-brachytherapy is possible. However, the image registration process introduces a source of uncertainty. Manual, real-time intra-operative LDR-BT is challenging under MRI due to confined space and procedural workflows. This motivates the development of MRI-compatible robots for prostate BT, with potential advantages of improved source placement accuracy and final dosimetry. In this paper, the state-of-art of technological components in MRI compatible robots, especially for LDR-BT, has been presented. This systematic review helps us to position an ongoing Cooperative Brachytherapy project, developing a real-time MRI-guided robot for adaptive LDR-BT. The design approach includes integrating separate modules: imaging, dose planning, needles, and robot.

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In this paper, a novel concept for a phantom of the prostate is introduced. To study and improve automated, robotized medical interventions, reliable phantoms are essential. During brachytherapy and biopsy, the prostate will undergo displacements and changes in orientation due to the needle insertion. Therefore, there is a shift in the target regions for radioactive seed deposition or biopsy acquisition. These shifts need to be taken into account for precise dosimetry. Furthermore, the organ can undergo deformations due to edemas with the same shifting result. Therefore, in this paper we propose a bioinspired phantom (BIP) for the prostate that is equipped with sensors and coupled with a numerical simulation for estimating deformations due to external forces. We have also put in place a cavity inside the phantom where pressure can be applied to enable the emulation of prostate growth due to inflammation. The phantom is conceived in such a way that it will be MRIsafe. It can thus be deployed for the in-bore study of automated brachytherapy and biopsy. In our evaluation, we verify that the changes in pose of the phantom can be correctly estimated and that these motions are plausible from a clinical point of view.