Treatment efficacy prediction of focused ultrasound therapies using multi-parametric magnetic resonance imaging

Magnetic resonance guided focused ultrasound (MRgFUS) is one of the most attractive emerging minimally invasive procedures for breast cancer, which induces localized hyperthermia, resulting in tumor cell death. Accurately assessing the post-ablation viability of all treated tumor tissue and surrounding margins immediately after MRgFUS thermal therapy residual tumor tissue is essential for evaluating treatment efficacy. While both thermal and vascular MRI-derived biomarkers are currently used to assess treatment efficacy, currently, no adequately accurate methods exist for the in vivo determination of tissue viability during treatment. The non-perfused volume (NPV) acquired three or more days following MRgFUS thermal ablation treatment is most correlated with the gold standard of histology. However, its delayed timing impedes real-time guidance for the treating clinician during the procedure. We present a robust deep-learning framework that leverages multiparametric MR imaging acquired during treatment to predict treatment efficacy. The network uses qualtitative T1, T2 weighted images and MR temperature image derived metrics to predict the three day post-ablation NPV. To validate the proposed approach, an ablation study was conducted on a dataset (N=6) of VX2 tumor model rabbits that had undergone MRgFUS ablation. Using a deep learning framework, we evaluated which of the acquired MRI inputs were most predictive of treatment efficacy as compared to the expert radiologist annotated 3 day post-treatment images.

Mitochondrial reactive oxygen species impact human fibroblast responses to protracted γ-ray exposures

Purpose: Continuous exposure to ionizing radiation at a low dose rate poses significant health risks to humans on deep space missions, prompting the need for mechanistic studies to identify countermeasures against its deleterious effects. Mitochondria are a major subcellular locus of radiogenic injury, and may trigger secondary cellular responses through the production of reactive oxygen species (mtROS) with broader biological implications. Methods and Materials: To determine the contribution of mtROS to radiation-induced cellular responses, we investigated the impacts of protracted γ-ray exposures (IR; 1.1 Gy delivered at 0.16 mGy/min continuously over 5 days) on mitochondrial function, gene expression, and the protein secretome of human HCA2-hTERT fibroblasts in the presence and absence of a mitochondria-specific antioxidant mitoTEMPO (MT; 5 µM). Results: IR increased fibroblast mitochondrial oxygen consumption (JO2) and H2O2 release rates (JH2O2) under energized conditions, which corresponded to higher protein expression of NADPH Oxidase (NOX) 1, NOX4, and nuclear DNA-encoded subunits of respiratory chain Complexes I and III, but depleted mtDNA transcripts encoding subunits of the same complexes. This was associated with activation of gene programs related to DNA repair, oxidative stress, and protein ubiquination, all of which were attenuated by MT treatment along with radiation-induced increases in JO2 and JH2O2. IR also increased secreted levels of interleukin-8 and Type I collagens, while decreasing Type VI collagens and enzymes that coordinate assembly and remodeling of the extracellular matrix. MT treatment attenuated many of these effects while augmenting others, revealing complex effects of mtROS in fibroblast responses to IR. Conclusion: These results implicate mtROS production in fibroblast responses to protracted radiation exposure, and suggest potentially protective effects of mitochondrial-targeted antioxidants against radiogenic tissue injury in vivo.

Design and evaluation of an open-source block face imaging system for 2D histology to magnetic resonance image registration

This study introduces a comprehensive hardware-software framework designed to enhance the quality of block face image capture-an essential intermediary step for registering 2D histology images to ex vivo magnetic resonance (MR) images. A customized camera mounting and lighting system is employed to maintain consistent relative positioning and lighting conditions. Departing from traditional transparent paraffin, dyed paraffin is utilized to enhance contrast for subsequent automatic segmentation. Our software facilitates fully automated data collection and organization, complemented by a real-time Quality Assurance (QA) section to assess the captured image's quality during the sectioning process. The setup is evaluated and validated using rabbit muscle and rat brain which underwent MR-guided focused ultrasound ablations. The customized hardware system establishes a robust image capturing environment. The software with a real-time QA section, enables operators to promptly rectify low-quality captures, thereby preventing data loss. The execution of our proposed framework produces robust registration results for H&E images to ex vivo MR images.•The presented hardware-software framework ensures the uniformity and resilience of the block face image capture process, contributing to a more reliable and efficient registration of 2D histology images to ex vivo MR images.