Maximally spaced projection sequencing in electron paramagnetic resonance imaging

Abstract

Electron paramagnetic resonance imaging (EPRI) provides 3D images of absolute oxygen concentration (pO2) in vivo with excellent spatial and pO2 resolution. When investigating such physiologic parameters in living animals, the situation is inherently dynamic. Improvements in temporal resolution and experimental versatility are necessary to properly study such a system. Uniformly distributed projections result in efficient use of data for image reconstruction. This has dictated current methods such as equal-solid-angle (ESA) spacing of projections. However, acquisition sequencing must still be optimized to achieve uniformity throughout imaging. An object-independent method for uniform acquisition of projections, using the ESA uniform distribution for the final set of projections, is presented. Each successive projection maximizes the distance in the gradient space between itself and prior projections. This maximally spaced projection sequencing (MSPS) method improves image quality for intermediate images reconstructed from incomplete projection sets, enabling useful real-time reconstruction. This method also provides improved experimental versatility, reduced artifacts, and the ability to adjust temporal resolution post factum to best fit the data and its application. The MSPS method in EPRI provides the improvements necessary to more appropriately study a dynamic system.

Three novel accurate pixel-driven projection methods for 2D CT and 3D EPR imaging

“…The mathematical phantom is what is shown in Fig. 13; the and number of measurements on a virtual spatial projection is 64; the sampling pattern is equal solid angle pattern [20]; the sampling order is Maximally spaced projection sequencing (MSPS) [21].…”

Real‐time image reconstruction for pulse EPR oxygen imaging using a GPU and lookup table parameter fitting

“…Projection acquisition schemes have been developed that provide approximately uniform sampling throughout the imaging process. Such acquisition schemes enable reconstruction of useful intermediate images from incomplete projection data, which closely approximate the final image reconstructed from complete projection data . For EPRI data acquired using these robust techniques, the real‐time reconstruction presented in this work allows for the visualization of the buildup of an oxygen image as data are acquired.…”

Fast dynamic electron paramagnetic resonance (EPR) oxygen imaging using low-rank tensors

“…Imaging projections were ordered using maximally spaced projection sequencing (MSPS) [39]; the navigator projections were chosen as the first 5 projections in the MSPS sequence. Acquisition of imaging and navigator projections was interleaved as shown in Fig.…”