No abstract

Brain tumor patients often experience functional deficits that extend beyond the tumor site. While resting-state functional MRI (rsfMRI) has been used to map such functional connectivity changes in brain tumor patients, the interplay between abnormal tumor vasculature and the rsfMRI signal is still not well understood. Therefore, there is an exigent need for new tools to elucidate how the blood‑oxygenation-level-dependent (BOLD) rsfMRI signal is modulated in brain cancer. In this initial study, we explore the utility of a preclinical model for quantifying brain tumor-induced changes on the rsfMRI signal and resting-state brain connectivity. We demonstrate that brain tumors induce brain-wide alterations of resting-state networks that extend to the contralateral hemisphere, accompanied by global attenuation of the rsfMRI signal. Preliminary histology suggests that some of these alterations in brain connectivity may be attributable to tumor-related remodeling of the neurovasculature. Moreover, this work recapitulates clinical rsfMRI findings from brain tumor patients in terms of the effects of tumor size on the neurovascular microenvironment. Collectively, these results lay the foundation of a preclinical platform for exploring the usefulness of rsfMRI as a potential new biomarker in patients with brain cancer.

The feasibility of dual-energy imaging using a fast kV-switching method on an angiographic C-arm CT system was investigated. Direct measurements of beam quality in the x-ray field demonstrate the stability of the kV-switching method. Phantom and in vivo experiments showed that images did not deviate from those of corresponding kV-constant scans. All performed experiments confirmed the capability of performing fast kV-switching scans on a clinically available C-arm CT system. More complex material decomposition tasks and postprocessing steps will be part of future investigations.

The uniformity results identified major factors degrading image quality. The quantitative results will guide selection of calibration points to mitigate the loss of uniformity. The unique combination of dual-energy and fluoroscopy imaging capabilities with a flat-panel photon-counting detector may enable new applications in interventional radiology.

Background Digital subtraction angiography (DSA) remains the gold standard for angiographic evaluation of cerebrovascular pathology, however, multiple acquisitions requiring additional time and radiation are often needed. In contrast, 3D-DSA provides volumetric information from a single injection but neglects temporal information. Four-dimensional-DSA (4D-DSA) combines temporal information of 2D-DSA with volumetric information of 3D-DSA to provide time-resolved tomographic 3D reconstructions, potentially reducing procedure time and radiation. This work evaluates the diagnostic quality of virtual single-frame 4D-DSA relative to 2D-DSA images by assessing clinicians’ ability to evaluate cerebrovascular pathology. Methods Single-frame images of four projections from 4D-DSA and their corresponding 2D-DSA images (n = 15) were rated by two neurointerventional radiologists. Images were graded based on diagnostic quality (0 = non-diagnostic, 1 = poor, 2 = acceptable, 3 = good). Dose area product (DAP) for each case was recorded for all 2D-DSA, 4D-DSA acquisitions, and the overall procedure. Results The mean diagnostic quality of all four 4D-DSA projections from both raters was 1.75 while the mean of 2D-DSA projections was 2.8. Student’s t-test revealed significant difference in diagnostic quality between 4D-DSA and 2D-DSA at all four projections (p < 0.001). On average 4D-DSA acquisitions accounted for 30% dose compared to the overall average aggregated dose per procedure. Conclusions The difference in image quality between virtual single-frame 4D-DSA and their respective 2D-DSA images is statistically significant. Furthermore, 4D-DSA acquisitions require less radiation dose than conventional procedures with 2D-DSA acquisitions.