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

Abstract

Brain perfusion SPECT can be used in the diagnosis of various neurologic or psychiatric disorders, e.g. stroke, epilepsy, dementia and posttraumatic stress disorder. As traditional SPECT provides limited resolution and sensitivity, we recently proposed a high resolution focusing multi-pinhole clinical SPECT scanner dubbed G-SPECT-I (Beekman et al 2015). G-SPECT-I achieves data completeness in the scan region of interest by making small translations of the patient bed while using projections from all bed positions together for image reconstruction. A strategy to restrict the number of bed translations is desired to minimize overhead time. Previously we presented optimized bed translation paths for focused partial brain imaging, while here we focus on whole brain imaging which is the common procedure in perfusion studies. Thus, a series of noise-free scans using a reduced number of bed positions were simulated and compared to an oversampled reference scan acquired with 128 bed positions. Noisy simulations were included to validate the utility of the optimized sequences in more realistic situations. Brain Uptake Ratios (BURs) and left-right Asymmetry Indices (AIs) in 51 selected Regions of Interest (ROIs) were calculated for assessment. Results show that images were barely affected by decreasing the number of bed positions from 128 down to 18 (mean deviation from the reference of only 2.2% and 1.5% for the BUR and AI respectively) while slightly larger deviations (2.9% and 2.7% respectively) were obtained when using 12 positions. For both 18-and 12-position sequences these deviations due to sampling were much smaller than those induced by noise (mean deviation of 6.5% and 8.6% respectively). Given an associated total overhead for bed movement of half a minute (18 positions) or 20 seconds (12 positions), G-SPECT-I can be a clinical platform that brings new protocols for fast (dynamic) whole brain SPECT and motion correction into reach.

Evaluation of a variable‐aperture full‐ring SPECT system using large‐area pixelated CZT modules: A simulation study for brain SPECT applications

“…However, if we compare our proposed scanner with an experimental dedicated multi‐pinhole brain SPECT system, 47,48 the dedicated system has good spatial resolution (~4.8 mm FWHM in the center of the cylindrical volume of interest) and the caudate and putamen in the brain phantom are well differentiated due to the magnification of the pinhole collimator for a small spherical volume having a 21 cm‐diameter. In addition, the investigational multi‐pinhole dedicated brain SPECT (e.g., G‐SPECT) having a high spatial resolution (below 3 mm) and a high sensitivity of 415 cps/MBq takes only 30 s for a total brain perfusion scan with optimized bed position sequences 49,50 . However, these dedicated brain designs using multi‐pinhole collimators have a significant limitation as for general‐purpose imaging scenarios (e.g., bone SPECT) due to a small cylindrical volume of interest 48 .…”

“…In addition, the investigational multi-pinhole dedicated brain SPECT (e.g., G-SPECT) having a high spatial resolution (below 3 mm) and a high sensitivity of 415 cps/MBq takes only 30 s for a total brain perfusion scan with optimized bed position sequences. 49,50 However, these dedicated brain designs using multi-pinhole collimators have a significant limitation as for general-purpose imaging scenarios (e.g., bone SPECT) due to a small cylindrical volume of interest. 48 In contrast, our proposed detector head geometry could be radially extended and still could have shorter scan time by swiveling individual detectors, which will be further investigated to optimize the acquisition mode with a slightly common axis of rotation if needed.…”

SPECT/CT: Standing on the Shoulders of Giants, It Is Time to Reach for the Sky!

“…Both these approaches may be the basis for developing fully stationary detector systems, which could represent the next revolution in SPECT gantry design. The resulting clinical SPECT images achieve resolutions down to 3 mm, with exciting preliminary clinical data in brain and cardiac imaging (39). However, the technique has not yet been implemented in hybrid SPECT/CT system designs.…”

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

“…In this context, the use of multi-pinhole collimation (MPC) has proven to be successful in significantly enhancing the clinical imaging of the brain, thyroid or heart (Beekman & van der Have 2007, Van Audenhaege et al 2015. MPC offers an excellent sensitivity to spatial resolution trade-off for brain imaging (Chen et al 2019), while reducing the fraction of down-scatter counts (Könik, Auer, De Beenhouwer, Kalluri, Zeraatkar, Furenlid & King 2019). 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).…”