Point-Spread-Function-Aware Slice-to-Volume Registration: Application to Upper Abdominal MRI Super-Resolution

MR image acquisition of moving organs remains challenging despite the advances in ultra-fast 2D MRI sequences. Post-acquisition techniques have been proposed to increase spatial resolution a posteriori by combining acquired orthogonal stacks into a single, high-resolution (HR) volume. Current super-resolution techniques classically rely on a two-step procedure. The volumetric reconstruction step leverages a physical slice acquisition model. However, the motion correction step typically neglects the point spread function (PSF) information. In this paper, we propose a PSF-aware slice-to-volume registration approach and, for the first time, demonstrate the potential benefit of Super-Resolution for upper abdominal imaging. Our novel reconstruction pipeline takes advantage of different MR acquisitions clinically used in routine MR cholangiopancreatography studies to guide the registration. On evaluation of clinically relevant image information, our approach outperforms state-of-the-art reconstruction toolkits in terms of visual clarity and preservation of raw data information. Overall, we achieve promising results towards replacing currently required CT scans

Intra-Operative Assessment of Cancer with X-Ray Phase Contrast Computed Tomography

X-ray Phase-Contrast Computed Tomography (PC-CT) increases contrast in weakly attenuating samples, such as soft tissues. In Edge-Illumination (EI) PC-CT, phase effects are accessed from amplitude modulation of the x-ray beam using alternating transmitting and attenuating masks placed prior to the sample and detector. A large field of view PC-CT scanner using this technique was applied to two areas of cancer assessment, namely excised breast and esophageal tissue. For the breast tissue, Wide Local Excisions (WLEs) were studied intra-operatively using PC-CT for the evaluation of tumor removal in breast conservation surgery. Images were acquired in 10 minutes without compromising on image quality, showing this can be used in a clinical setting. Longer, higher resolution PC-CT images were also taken, with analysis showing previously undetected thinning of tumor strands. This would allow a second use of the system for “virtual histopathology”, outside of surgery. For the esophagus samples, tissues were taken from esophagectomy surgery, where the lower part of the esophagus is removed, and the stomach relocated. For the assessment of ongoing therapy, accurate staging of tumors in the removed esophagus is essential, with the current gold standard provided by histopathology. PCCT images were acquired on several samples and compare well with histopathology, with both modalities showing similar features. Examples are shown where staging of tumor penetration is possible with PC-CT images alone, which is hoped will be an important step in performing the imaging and staging intra-operatively