Effect of resolution improvement on required count density in ECT imaging: a computer simulation

Muehllehner, G.

doi:10.1088/0031-9155/30/2/005

Cited by 76 publications

(35 citation statements)

References 12 publications

(3 reference statements)

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“…When appreciating the relatively low peak counting rate, one has to take into account that PET image quality is a strongly nonlinear function of spatial resolution: a 2-fold improvement of spatial resolution may compensate for approximately a 32-fold reduction of statistics (19), or 4 times worse sensitivity with 2 times better spatial resolution can yield improved image quality (20). Thus, the high resolution of the instrument compensates profusely for the slightly lower peak counting rates and, together with the high sensitivity, enables low-dose animal imaging.…”

Section: Discussionmentioning

confidence: 99%

Performance Evaluation of the Small-Animal nanoScan PET/MRI System

et al. 2013

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nanoScan is a high-resolution integrated system for consecutive PET and MR imaging of small laboratory animals. We evaluated the performance of the system, using the NEMA NU 4-2008 protocol for the PET component and the NEMA MS 1-2007, MS 2-2008, and MS 3-2007 standards for the MR imaging component. Methods:The imaging system uses magnetically shielded position-sensitive photomultiplier tubes and a compact 1-T permanent-magnet MR imaging platform. Spatial resolution, sensitivity, counting rate capabilities, and image quality parameters were evaluated in accordance with the aforementioned NEMA standards. Further in vivo evaluation experiments complement the physical validation results. Results: The spatial resolution of the PET system enabled the 0.8-mm rods of a Derenzo phantom to be resolved. With point source and 2-dimensional filtered backprojection reconstruction, the resolution varied from 1.50 to 2.01 mm in full width at half maximum in the radial direction and from 1.32 to 1.65 mm in the tangential direction within the radius of 25 mm. Peak absolute sensitivity was 8.41%. Scatter fraction was 17.3% and 34.0%, and maximum noise-equivalent counting rate was 406 and 119 kcps in the mouselike and ratlike phantom, respectively. The image quality test found a nonuniformity of 3.52% and a spillover ratio of 6.2% and 5.8% in water and air, respectively. In testing of the MR imaging component, artifact-free images with high signal-to-noise ratio were recorded. Geometric distortion was below 5%, and image uniformity was at least 94.5% and 96.6% for the 60-and 35-mm radiofrequency coils, respectively. Conclusion: The nanoScan integrated small-animal PET/MR imaging system has excellent spatial resolution and sensitivity. The performance characteristics of the PET and the MR imaging components are not compromised as a result of their integration onto a single platform. Because of its combination of features and performance parameters, the system provides crucial advantages for preclinical imaging studies over existing PET/CT systems, especially in neurologic and oncologic research.Key Words: preclinical PET; PET/MR imaging; small-animal imaging; performance evaluation; multimodality imaging The unique advantages of molecular imaging with PET in various fields of biomedical research have clearly been shown during the past few decades. PET can play a significant role in the development of therapeutic drugs and molecular imaging biomarkers, in the exploration of physiologic and biochemical processes, and in the in vivo mapping of receptor transmitters and enzymes (1,2). Because of the increasing availability of animal disease models, there is growing interest in using PET for studies on small animals (3,4). In vivo anatomic and biochemical studies on rodents require dedicated scanners with high resolution and sensitivity.PET can localize picomolar concentrations of a labeled molecule (5) but does not provide the anatomic context of the tracer. Resolving brain morphology is of unique importance in dedicated central nervo...

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Section: Discussionmentioning

confidence: 99%

Performance Evaluation of the Small-Animal nanoScan PET/MRI System

et al. 2013

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“…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 necessitates a drop in sensitivity (2).…”

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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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“…The point sensitivity is comparable to the sensitivity of a dualhead system with LEHR parallel-beam collimators but the volume sensitivity is 4 times lower. However, the resolution is 2 times better, a trade-off that is supported by Muehllehner [1]. A quantitative study based on CNR-measurements will also be performed to further investigate the resulting image quality.…”

Section: Discussionmentioning

confidence: 89%

Design of a static full-ring multi-pinhole collimator for brain SPECT

Audenhaege

Holen

Deprez

et al. 2011

2011 IEEE Nuclear Science Symposium Conference Record

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Abstract-In clinical practice, brain SPECT is mostly performed using a dual-head SPECT scanner with fan-beam or parallel-beam collimators rotating around the patient's head. The resolution of such a system is typically about 6-8 mm, which is rather poor to image the complex structures of the human brain.We developed a non-rotating multi-pinhole collimator for brain SPECT imaging with a resolution of 4 mm. A full-ring geometry allows for complete transaxial sampling. This enables the use of a stationary collimator. The collimator is a tungsten ring with two rows of pinholes. Each pinhole can individually be opened or closed with shutters. A sequence of shutter movements is performed to obtain an acquisition setup that simulates a rotational movement. The collimator is designed for the LaPET system (a PET detector ring made of 24 LaBr3 detectors) and is optimized to maximize the system performance, resulting in a collimator radius of 145 mm and a pinhole diameter of 2 mm. This system has a sensitivity that is 4 times lower than a dual-head system with LEHR parallel-beam collimators. However, the resolution is 2 times better, a trade-off that is supported by Muehllehner [1]. Monte-Carlo simulated projections of a resolution phantom are successfully reconstructed and the resulting image shows that a resolution of 4 mm is indeed achieved.

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Effect of resolution improvement on required count density in ECT imaging: a computer simulation

Cited by 76 publications

References 12 publications

Performance Evaluation of the Small-Animal nanoScan PET/MRI System

Performance Evaluation of the Small-Animal nanoScan PET/MRI System

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

Design of a static full-ring multi-pinhole collimator for brain SPECT

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