Performance of a novel collimator for high‐sensitivity brain SPECT

Abstract

We assessed improvements in performance in detection and estimation tasks due to a novel brain single photon computed tomography collimator. Data were acquired on the CeraSPECT scanner using both new and standard collimators. The new variable focusing collimator SensOgrade samples the projections unequally, with central regions more heavily represented, to compensate for attenuation of counts from central brain structures. Furthermore, it utilizes more of the cylindrical crystal surface. Two phantom studies were performed. The first phantom was a 21-cm-diameter cylindrical background containing nine spheres ranging from 0.5 to 5 cm3 in volume. 99mTc sphere to background activity ratio was 10:1. Twenty-nine 10-min datasets were acquired with each collimator. The second phantom was the Radiology Support Devices (Long Beach, CA) striatal phantom with striatal-background ratios of 10:1 on the left and 5:1 on the right. Twenty-nine 4-min datasets were acquired with each collimator. Perfusion imaging using 99mTc-HMPAO was also performed in three healthy volunteers using both collimators under identical simulations. Projections were reconstructed by filtered backprojection with an unwindowed ramp filter. The nonprewhitening matched filter signal-to-noise ratio (NPW-SNR) was computed as a surrogate for human performance in detecting spherical lesions. Sphere activity concentration, radius, and location coordinates were simultaneously estimated by fitting images to an assumed model using an iterative nonlinear algorithm. Resolution recovery was implicit in the estimation procedure, as the point spread function was incorporated into the model. NPW-SNR for sphere detection was 1.5 to 2 times greater with the new collimator; for the striatal phantom the improvement in SNR was 54%. The SNR for estimating sphere activity concentration improved by 46 to 89% for spheres located more than 5 cm from the phantom center. Images acquired with the standard collimator were too noisy in the central regions to allow estimation of sphere activity. In 99mTc-HMPAO human studies, SNR was improved by 21 to 41% in the cortex, 66% in the basal ganglia, and 74% in the thalamus. The new collimator leads to substantially improved detection and estimation performance throughout the brain. The higher sensitivity will be particularly important for dynamic imaging.

Inclusion of quasi-vertex views in a brain-dedicated multi-pinhole SPECT system for improved imaging performance

“…Moreover, MPC provides improved penetration characteristics which makes its use more suited for high-energy photon-emitting isotope imaging (e.g., 111 In, 123 I) (Van Audenhaege et al 2013, Könik, Auer, De Beenhouwer, Kalluri, Zeraatkar, Furenlid & King 2019). Research has focused on the development of high-resolution high-sensitivity multi-pinhole systems designed specifically for brain imaging, such as the CeraSPECT (Batis 2011), the InspiraHD system (Stoddart & Stoddart 1992, El Fakhri et al 2006, and recently the G-SPECT (Beekman et al 2015, Chen et al 2018, Chen et al 2019). Among these systems, the best performance was reported for the G-SPECT with a 3 mm spatial resolution associated to a 0.04% sensitivity in a central volume of the brain (10 cmdiameter, 6 cm-axial length cylindrical volume) (Chen et al 2019).…”

Optimized sampling for high resolution multi-pinhole brain SPECT with stationary detectors

“…Some dedicated brain SPECT scanners, e.g. CeraSPECT, inSpira HD or NeuroFocus (Stoddart and Stoddart 1992, Fakhri et al 2006, Sensakovic et al 2014, Stam et al 2018, have been developed, but resolutions are still around 7 mm and some are not manufactured anymore. Such a limited resolution hampers detection of small localized perfusion abnormalities which can compromise accuracy of diagnosis and early detection of neuropathology while a low sensitivity requires a relatively high tracer dose and long scanning time resulting in patient discomfort as well as increased risk of motion artefacts.…”

Simulations of a Multipinhole SPECT Collimator for Clinical Dopamine Transporter (DAT) Imaging

“…An annular SPECT system consisting of a three-segment parallel-beam rotating collimator within a stationary annular crystal (CeraSPECT™) provided 8.3 mm resolution and 0.022% sensitivity at the central axis [6, 7]. The collimators of this system were replaced with variable focusing collimators (SensOgrade™) to further increase the sensitivity (by a factor of 1.4–2) [8]. A slit/slat collimator, offered a resolution of 6 mm and sensitivity of 0.051% at the center of the FOV with 35% multiplexing [9].…”