Matthew Getzin

Low-field designs for interior MRI and CT coupling

The combination of CT and MRI for simultaneous image acquisition has not yet been successfully prototyped. To overcome the geometric conflict and electromagnetic interference between CT and MRI hardware, low-field magnet arrays are utilized. Using 3D magnetic field modeling software, several permanent magnet array designs are proposed yielding homogeneous field magnitudes of ~0.3-0.35 T. The results demonstrate potential configurations to enable interior MRI while working synergistically with x-ray hardware for simultaneous data acquisition.

Carotid plaque characterization using CT and MRI scans for synergistic image analysis

Noninvasive determination of plaque vulnerability has been a holy grail of medical imaging. Despite advances in tomographic technologies , there is currently no effective way to identify vulnerable atherosclerotic plaques with high sensitivity and specificity. Computed tomography (CT) and magnetic resonance imaging (MRI) are widely used, but neither provides sufficient information of plaque properties. Thus, we are motivated to combine CT and MRI imaging to determine if the composite information can better reflect the histological determination of plaque vulnerability. Two human endarterectomy specimens (1 symptomatic carotid and 1 stable femoral) were imaged using Scanco Medical Viva CT40 and Bruker Pharmascan 16cm 7T Horizontal MRI / MRS systems. μCT scans were done at 55 kVp and tube current of 70 mA. Samples underwent RARE-VTR and MSME pulse sequences to measure T1, T2 values, and proton density. The specimens were processed for histology and scored for vulnerability using the American Heart Association criteria. Single modality-based analyses were performed through segmentation of key imaging biomarkers (i.e. calcification and lumen), image registration, measurement of fibrous capsule, and multi-component T1 and T2 decay modeling. Feature differences were analyzed between the unstable and stable controls, symptomatic carotid and femoral plaque, respectively. By building on the techniques used in this study, synergistic CT+MRI analysis may provide a promising solution for plaque characterization in vivo.

Enhancing spatial resolution for spectral μCT with aperture encoding

Recent advances in X-ray imaging technologies have paved the way for use of energy-discriminating photon-counting detector arrays. These detectors show promise in clinical and preclinical applications. Multi-energy or spectral CT images can be visualized in multi-colors. Despite the advantages offered by the spectral dimension of acquired data, higher image resolution is still desirable, especially in challenging tasks such as on-site studies of resected pathological tissues. Here we propose to enhance image resolution of a spectral X-ray imaging system by partially blocking each detector element with an absorption grating (for reduced aperture), commonly used for Talbot-Lau interferometry. After acquiring X-ray data at an initial grating-detector configuration, the grating is shifted to expose previously blocked portions so that each measurement contains new information. All the acquired data are then combined into an augmented system matrix and subsequently reconstructed using an iterative algorithm. Our proof of concept simulations are performed with MCNP6.1 code and the experiment was performed using a Hamamatsu microfocus X-ray source, an absorption grating, and an Xray camera. Our results demonstrate that the gratings commonly used for x-ray phase-contrast imaging have a utility for super-resolution imaging performance.

Investigation into multiphysics coupling via semiconducting nanophosphors

In an attempt to strengthen the case for the design and manufacture of multi-modal imaging machines capable of simultaneous and synergistic computed tomography (CT) and magnetic resonance imaging (MRI) as proposed by Ge Wang as early as 2012, a series of experiments using various combinations of nanophosphors, agar gels, a fiber optic coupled UV LED, and micro-MRI have been proposed and performed. The aim of these experiments is to elucidate the ability, if any, of UV-excited nanophosphors to modulate MRI parameters (T1, T2, and T2*). The majority of our findings have been difficult to interpret, although some hints of the coupling were seen in previously reported studies. This paper briefly describes the next set experiments and discusses the improvements that need to be made to achieve statistical confidence in any phenomena that may be recorded. This work is an important step in the coupling of seemingly unrelated imaging modalities and could serve as a stepping-stone for further insight into the future of imaging.