Pixel-based subsets for rapid multi-pinhole SPECT reconstruction

Branderhorst, Woutjan; Vastenhouw, Brendan; Beekman, Freek J.

doi:10.1088/0031-9155/55/7/015

Cited by 104 publications

(83 citation statements)

References 34 publications

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“…Reconstruction was to cubic voxels of 0.4-mm length. Thirty iterations (32 subsets) of pixel-based ordered-subset expectation maximization (14) were performed for the Jaszczak phantom and mouse bone scans. Fifteen iterations (32 subsets) were performed for all other scans, as determined from prior investigation.…”

Section: Data Processing and Image Reconstructionmentioning

confidence: 99%

Performance Assessment of a Preclinical PET Scanner with Pinhole Collimation by Comparison to a Coincidence-Based Small-Animal PET Scanner

et al. 2014

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PET imaging of rodents is increasingly used in preclinical research, but its utility is limited by spatial resolution and signal-to-noise ratio of the images. A recently developed preclinical PET system uses a clustered-pinhole collimator, enabling high-resolution, simultaneous imaging of PET and SPECT tracers. Pinhole collimation strongly departs from traditional electronic collimation achieved via coincidence detection in PET. We investigated the potential of such a design by direct comparison to a traditional PET scanner. Methods: Two small-animal PET scanners, 1 with electronic collimation and 1 with physical collimation using clustered pinholes, were used to acquire data from Jaszczak (hot rod) and uniform phantoms. Mouse brain imaging using 18 F-FDG PET was performed on each system and compared with quantitative ex vivo autoradiography as a gold standard. Bone imaging using 18 F-NaF allowed comparison of imaging in the mouse body. Images were visually and quantitatively compared using measures of contrast and noise. Results: Pinhole PET resolved the smallest rods (diameter, 0.85 mm) in the Jaszczak phantom, whereas the coincidence system resolved 1.1-mm-diameter rods. Contrast-to-noise ratios were better for pinhole PET when imaging small rods (,1.1 mm) for a wide range of activity levels, but this reversed for larger rods. Image uniformity on the coincidence system (,3%) was superior to that on the pinhole system (5%). The high 18 F-FDG uptake in the striatum of the mouse brain was fully resolved using the pinhole system, with contrast to nearby regions equaling that from autoradiography; a lower contrast was found using the coincidence PET system. For shortduration images (low-count), the coincidence system was superior. Conclusion: In the cases for which small regions need to be resolved in scans with reasonably high activity or reasonably long scan times, a first-generation clustered-pinhole system can provide image quality in terms of resolution, contrast, and the contrast-to-noise ratio superior to a traditional PET system. Smal l-animal PET is an increasingly important tool in biomedical research. A recent development in scanner technology has been the introduction of a focused, clustered-pinhole collimator that enables simultaneous high-spatial-resolution PET and SPECT imaging. Physical collimation of the 511-keV photons produced by positron-electron annihilation, using clustered pinholes, is a substantial change in scanner design as compared with electronic collimation via coincidence detection. Clustered pinholes can offer improved spatial resolution (1) in rodent images, despite a low fraction of single 511-keV photons being detected as compared with the fraction of detected photon pairs in traditional PET. Such scanners are likely suited to different applications. The commonly encountered sensitivity-resolution trade-off has been investigated previously: it has been known for several decades that an improvement in image quality can be achieved via a gain in spatial resolution, even if this gain...

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Section: Data Processing and Image Reconstructionmentioning

confidence: 99%

Performance Assessment of a Preclinical PET Scanner with Pinhole Collimation by Comparison to a Coincidence-Based Small-Animal PET Scanner

et al. 2014

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“…The list-mode data of the 20 WB scans with different activities were reconstructed using the statistical iterative algorithm (13)(14)(15) as implemented in the U-SPECT-II system software version 34i3, into image matrices of 123 · 131 · 259 pixels of 0.375 mm in all directions, resulting in image sizes of 46 · 49 · 97 mm 3 . The photopeak window was 126-154 keV, corresponding to a width of 20% of the peak energy (140 keV).…”

Section: Reconstruction Settingsmentioning

confidence: 99%

Using the NEMA NU 4 PET Image Quality Phantom in Multipinhole Small-Animal SPECT

Harteveld¹,

Meeuwis²,

Disselhorst³

et al. 2011

J Nucl Med

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Several commercial small-animal SPECT scanners using multipinhole collimation are presently available. However, generally accepted standards to characterize the performance of these scanners do not exist. Whereas for small-animal PET, the National Electrical Manufacturers Association (NEMA) NU 4 standards have been defined in 2008, such standards are still lacking for small-animal SPECT. In this study, the image quality parameters associated with the NEMA NU 4 image quality phantom were determined for a small-animal multipinhole SPECT scanner. Methods: Multiple whole-body scans of the NEMA NU 4 image quality phantom of 1-h duration were performed in a U-SPECT-II scanner using 99m Tc with activities ranging between 8.4 and 78.2 MBq. The collimator contained 75 pinholes of 1.0-mm diameter and had a bore diameter of 98 mm. Image quality parameters were determined as a function of average phantom activity, number of iterations, postreconstruction spatial filter, and scatter correction. In addition, a mouse was injected with 99m Tc-hydroxymethylene diphosphonate and was euthanized 6.5 h after injection. Multiple whole-body scans of this mouse of 1-h duration were acquired for activities ranging between 3.29 and 52.7 MBq. Results: An increase in the number of iterations was accompanied by an increase in the recovery coefficients for the small rods (RC rod ), an increase in the noise in the uniform phantom region, and a decrease in spillover ratios for the cold-air-and water-filled scatter compartments (SOR air and SOR wat ). Application of spatial filtering reduced image noise but lowered RC rod . Filtering did not influence SOR air and SOR wat . Scatter correction reduced SOR air and SOR wat . The effect of total phantom activity was primarily seen in a reduction of image noise with increasing activity. RC rod , SOR air , and SOR wat were more or less constant as a function of phantom activity. The relation between acquisition and reconstruction settings and image quality was confirmed in the 99m Tc-hydroxymethylene diphosphonate mouse scans. Conclusion: Although developed for small-animal PET, the NEMA NU 4 image quality phantom was found to be useful for small-animal SPECT as well, allowing for objective determination of image quality parameters and showing the tradeoffs between several of these parameters on variation of acquisition and reconstruction settings.

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“…SPECT images were reconstructed using projections from all bed positions simultaneously (14) using pixel-based ordered-subset expectation maximization (15). Three photopeak energy window settings were tested: a window set at the 440 keV photopeak, a window set at 79 keV, or both energy windows simultaneously.…”

Section: Image Reconstructionmentioning

confidence: 99%

Utilizing High-Energy γ-Photons for High-Resolution ²¹³Bi SPECT in Mice

et al. 2015

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The combined α-, γ-, and x-ray emitter 213 Bi (half-life, 46 min) is promising for radionuclide therapy. SPECT imaging of 213 Bi is challenging, because most emitted photons have a much higher energy (440 keV) than common in SPECT. We assessed 213 Bi imaging capabilities of the Versatile Emission Computed Tomograph (VECTor) dedicated to (simultaneous) preclinical imaging of both SPECT and PET isotopes over a wide photon energy range of 25-600 keV. Methods: VECTor was equipped with a dedicated clustered pinhole collimator. Both the 79 keV x-rays and the 440 keV γ-rays emitted by 213 Bi could be imaged. Phantom experiments were performed to determine the maximum resolution, contrast-to-noise ratio, and activity recovery coefficient for different energy window settings. Additionally, imaging of [ 213 Bi-DOTA,Tyr 3 ]octreotate and 213 Bi-diethylene triamine pentaacetic acid (DTPA) in mouse models was performed. Results: Using 440 keV γ-rays instead of 79 keV x-rays in image reconstruction strongly improved the resolution (0.75 mm) and contrast-to-noise characteristics. Results obtained with a single 440 keV energy window setting were close to those with a combined 79 keV/440 keV window. We found a reliable activity recovery coefficient down to 0.240 MBq/mL with 30-min imaging time. In a tumor-bearing mouse injected with 3 MBq of [ 213 Bi-DOTA,Tyr 3 ]octreotate, tumor uptake could be visualized with a 1-h postmortem scan. Imaging a nontumor mouse at 5-min frames after injection of 7.4 MBq of 213 Bi-DTPA showed renal uptake and urinary clearance, visualizing the renal excretion pathway from cortex to ureter. Quantification of the uptake data allowed kinetic modeling and estimation of the absorbed dose to the kidneys. Conclusion: It is feasible to image 213 Bi down to a 0.75-mm resolution using a SPECT system equipped with a dedicated collimator. Newoppor tunities for high linear energy transfer radionuclide therapy with the a-particle emitters 225 Ac and 213 Bi are increasingly being investigated (1-3). The research for peptide receptor radionuclide therapy with a-particles is mostly focused on labeling peptides with 213 Bi. Not only is the short half-life of 46 min for 213 Bi in good accordance with the rapid targeting to receptor-positive tumors and the rapid clearance of peptides, it also raises less concern for detrimental effects because of the absence of nonspecific uptake by daughters detached from its peptide or linker due to a-decay recoil (4). 213 Bi offers the best imaging opportunities through its 440 keV g-ray and is therefore important for biodistribution and dosimetry studies (5). All other g-rays and x-rays emitted by 213 Bi and its daughters are too low either in abundance or in energy to be suitable for imaging, possibly with the exception of the x-rays from 213 Bi at 77 and 79 keV if appropriate correction methods for down-scatter of the 440 keV g-rays are applied (Supplemental Table 1; supplemental materials are available at http://jnm.snmjournals.org (6)). Patient imaging of the uptake patte...

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Pixel-based subsets for rapid multi-pinhole SPECT reconstruction

Cited by 104 publications

References 34 publications

Performance Assessment of a Preclinical PET Scanner with Pinhole Collimation by Comparison to a Coincidence-Based Small-Animal PET Scanner

Performance Assessment of a Preclinical PET Scanner with Pinhole Collimation by Comparison to a Coincidence-Based Small-Animal PET Scanner

Using the NEMA NU 4 PET Image Quality Phantom in Multipinhole Small-Animal SPECT

Utilizing High-Energy γ-Photons for High-Resolution ²¹³Bi SPECT in Mice

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Pixel-based subsets for rapid multi-pinhole SPECT reconstruction

Cited by 104 publications

References 34 publications

Performance Assessment of a Preclinical PET Scanner with Pinhole Collimation by Comparison to a Coincidence-Based Small-Animal PET Scanner

Performance Assessment of a Preclinical PET Scanner with Pinhole Collimation by Comparison to a Coincidence-Based Small-Animal PET Scanner

Using the NEMA NU 4 PET Image Quality Phantom in Multipinhole Small-Animal SPECT

Utilizing High-Energy γ-Photons for High-Resolution 213Bi SPECT in Mice

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Utilizing High-Energy γ-Photons for High-Resolution ²¹³Bi SPECT in Mice