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sharing sensitive information, make sure youre on a federal Multi-pinhole (MPH) collimators have been proposed to address resolution-sensitivity tradeoff issues together with sampling issues (33). Nine detectors are placed along the transaxial direction covering 180. Optimized image acquisition for dopamine transporter imaging with ultra-high resolution clinical pinhole SPECT. Figure 6 illustrates the MPH multiplexing with a rectangular detector. In their work, they investigated whether the optimal collimator-detector geometry can improve the tumor-to-background ratio. J Nucl Med 2018;59:abst 585. A full-ring multi-lofthole collimator, which consists of a tungsten ring with loftholes, is mounted on the system with a shutter mechanism that controls the projection overlapping and also provides complete angular sampling without the need for rotational acquisition. The system resolution was set to 810 mm, which is similar to that of a brain SPECT scanner and the number of detectors was arranged to maximize the sensitivity (0.0180.032%) (98). Phys Med Biol 2009;54:N267-72. The new PMC design is here! On the other hand, sensitivity, which is also spatially variant, is the ratio of the detected photons to the emitted photons and can be expressed as detected percentage or as cps/MBq (SI unit of radioactivity). This is particularly an issue for the case of down-scatter from higher-energy photons, as for those emitted by 123I with ~23% abundance in addition to its primary photon. (A) G-SPECT-I system with three optical cameras and a user interface for volume-of-interest (VOI) selection; (B) multi-pinhole collimator of G-SPECT-I system. Other methods of reducing penetration are based on clustered pinholes (45,46) or the use of smaller pinhole aperture sizes (43,44). A sample 9-pinhole collimator (MPGP) mounted on a clinical SPECT scanner. The https:// ensures that you are connecting to the All 54 pinholes distributed over three rings are focused on the complete data volume [CDV: the spherical object shown (A) in the FOV]. The thickness of the pinhole plate is 1 cm and each pinhole has a knife edge at the half depth of the pinhole plate. Right: Lofthole with a circular aperture and a rectangular exit window [courtesy of Van Audenhaege et al. HHS Vulnerability Disclosure, Help Evaluation of a multi-pinhole collimator for imaging small animals with different sizes. Jaszczak RJ, Li J, Wang H, Zalutsky MR, Coleman RE. (A) Transparent plates compress the breast and a VOI is selected using optical cameras.

They estimated that the in-plane (normal to the axis of rotation) resolution loss was 0.320.63 mm FWHM and the cross-plane (aligned with the axis of rotation) resolution loss was 0.210.42 mm FWHM. [. The effects of object activity distribution on multiplexing multi-pinhole SPECT. The first one is a two-sphere phantom comprised of two spherical sources with a diameter of 5 mm, one located at the CFOV and the other located 20 mm offset from the CFOV. (40) compared W and depleted uranium-238 (DU-238) pinhole apertures with different pinhole diameters (1, 2, 3, and 4 mm) for imaging breast lesions using 99mTc tracers. Development and application of high-sensitivity and high-resolution fully 3D SPECT imaging techniques using two different collimator designs. Funk et al. Point source, brain and cardiac phantoms were simulated and images were reconstructed with OS-EM algorithm. A 49-pinhole SPECT system was designed and investigated by simulations for use as a computer-aided robotic system for head, breast, thorax, arms and legs imaging in radiation therapy (Figure 20) by Bowsher et al. (67) designed a high-resolution detector that directs CsI fibers towards the pinhole so that the scintillation light can be transported along the same line as the gamma ray travels before it interacts with the crystal. Angular sampling of the base configuration was enhanced by adding the temporal shuttering of two additional apertures per detector positioned laterally to either side of the central aperture. Simulation study on a stationary data acquisition SPECT system with multi-pinhole collimators attached to a triple-head gamma camera system. Doctor Dissertation. The ROR is set to 167 mm to provide a FOV of 20 cm to accommodate the patients head, without touching the patients shoulder. He is founder, shareholder, and part time CEO of MILabs B.V, a company that develops pinhole PET and SPECT systems like the U-SPECT and G-SPECT-I scanners that were addressed in the present paper. Several research groups have shown that multiplexing may misplace the activity in the reconstruction (56-59). One of the first MPH collimators was developed in 1978 when Vogel et al. Shown are the 2 cm thick aperture plate with a single aperture per detector and the 23 hexagonal detectors (courtesy of Dr. Kesava S. Kalluri). King et al. in 1993 (77) and developed by Klein et al. Huang et al. U-SPECT-II: an ultra-high-resolution device for molecular small-animal imaging. (35) showed that the artifacts reduced when either helical sampling (bed movement in constant intervals between angular steps) or order-subsets sampling (bed movement in a repeating sequence to different axial positions) were utilized, since both methods provide improved axial sampling. Vaissier et al. Left: (A) pod geometry. Smith et al. Ogawa et al. Van Audenhaege K, Vanhove C, Vandenberghe S, Van Holen R. The evaluation of data completeness and image quality in multiplexing multi-pinhole SPECT. Lead shielding was used inside the collimator to prevent multiplexing of the pinhole projections. Role of neuroimaging in Alzheimers disease, with emphasis on brain perfusion SPECT. Single photon emission computed tomography (SPECT), multi-pinhole, collimator, brain, cardiac.

52nd Annual Meeting of the Society of Nuclear Medicine, 2005. Simplified illustration of projection images generated using a spherical phantom. Molecular breast tomosynthesis with scanning focus multi-pinhole cameras. Lyon, France: IEEE NSS/MIC Conf. Wang Y. They assessed the feasibility of maneuvering the SPECT collimator system around the patient in position for radiation therapy, allowing an unrestricted therapy procedure. In these systems, 75 gold circular pinholes were arranged in a cylindrical-shaped collimator and there is another outer lead cylinder with square holes that act as a shielding for the detector, which completely solves the problem of multiplexing as discussed in the next section. These two iterative steps are repeated until the multiplexing artifacts are considered to be eliminated or adequately reduced. Several strategies have been attempted to further improve the detection efficiency in MPH SPECT (30). The pinhole acceptance angle is 32.5 and peripheral pods are tilted towards the central pod by 16.25. Characterization of a multi-pinhole molecular breast tomosynthesis scanner. At the same location, the MPH geometric sensitivity is 87 cps/MBq (0.009%) which is similar to that of the low energy ultra-high resolution fan beam collimator with an improved resolution (4.7 vs. 7.4 mm). Since multiplexing allows the projection size to be larger than that of the non-multiplexing design, it could potentially allow a larger magnification factor to improve spatial resolution and increase the sensitivity if the larger magnification is obtained by bringing the pinholes closer to the source. VECTor: a preclinical imaging system for simultaneous submillimeter SPECT and PET. Gullberg GT, Zeng GL, Datz FL, Christian PE, Tung CH, Morgan HT. They performed GATE simulations with various phantoms to evaluate the system performance. Lyon, France: IEEE Nuclear Science Symposium, Medical Imaging Conference Record, 2016. During this process, determination of the incident angle of gamma-photons on the detector is crucial. Each detector-pinhole combination focuses and covers the heart, which is modeled as an 18 cm diameter sphere (Figure 22). For imaging smaller objects than the detector (e.g., organs or tumors), the trade-off between spatial resolution and sensitivity compared to a conventional parallel-hole collimator can be improved upon with the use of converging collimators for organ-specific SPECT applications (31). Chou KL, Hurtig HI, Stern MB, Colcher A, Ravina B, Newberg A, Mozley PD, Siderowf A. Aguiar P, Pino F, Silva-Rodriguez J, Pavia J, Ros D, Ruibal A, El Bitar Z. Analytical, experimental, and Monte Carlo system response matrix for pinhole SPECT reconstruction. Comparison of simultaneous dual-isotope multipinhole SPECT with rotational SPECT in a group of patients with coronary artery disease. Spatial resolution was found to be 1.0 cm at 12.7 cm from the pinhole plate and the system sensitivity was found to be 750 cps/MBq at 11.5 cm from the pinhole plate (76). No.00CH37149), 2000. Parallax or DOI effect due to gamma-rays entering the detector at oblique angles. Left: experimental setup of the 9-pinhole MPI SPECT system with a torso phantom. In their designs, the patient lies prone on a specially designed bed with the scanner underneath. The site is secure. Shrestha U, Sciammarella M, Alhassen F, Yeghiazarians Y, Ellin J, Verdin E, Boyle A, Seo Y, Botvinick EH, Gullberg GT. Myocardial phantom simulation results showed that with more than eight pinholes for each detector, one can obtain similar image quality to that of the parallel hole collimator. Yan et al. Bocher M, Blevis IM, Tsukerman L, Shrem Y, Kovalski G, Volokh L. A fast cardiac gamma camera with dynamic SPECT capabilities: design, system validation and future potential. Systematic review of the diagnostic utility of SPECT imaging in dementia.

Available online: Tornai MP, Pieper BC, Bowsher JE, Jaszczak RJ. Van Audenhaege K, Van Holen R, Vanhove C, Vandenberghe S. Collimator design for a multipinhole brain SPECT insert for MRI. demonstrated that for 123I DaTscan imaging, total scatter, multiple scatters, and penetration events for the low energy high resolution (LEHR) parallel-hole collimators were 2.5, 7.6 and 14 times more than that of an MPH collimator within the 15% photopeak window and with a 2-cm thick tungsten aperture plate (37). (7) proposed the placement of an MPH collimator on one head of a SPECT system and a fan-beam collimator on the other head (Figure 15).

(86). Dashed lines inside the detector and the pinhole plate show their central plane, respectively. AdaptiSPECT-C is a multi-detector MPH brain SPECT designed jointly by groups at UMass Medical School and the University of Arizona (91) for clinical brain imaging with improved resolution and sensitivity. The projections with multiplexing might lead to artifacts in image reconstruction because of the overlapped ambiguous region where detected events could have come through more than one aperture. The degree of multiplexing can be defined as Eq. will also be available for a limited time. Some research groups are working on the elimination of the DOI effect for MPH SPECT. DiFilippo et al. The shape of keel-edge collimators minimizes gamma penetration near the edge of the aperture (Figure 3). The UCSF 20-pinhole SPECT collimator (courtesy of Dr. Youngho Seo). Effects of pinhole material and aperture size on lesion contrast and SNR breast SPECT. See: https://creativecommons.org/licenses/by-nc-nd/4.0/. Two groups of five detectors are tilted and positioned on each side of the nine detectors in the main row. Preliminary Investigation of Axial and Angular Sampling in Multi-Pinhole AdaptiSPECT-C with XCAT Phantoms. Emission tomography: the fundamentals of PET and SPECT. A stationary hemispherical SPECT imager for three-dimensional brain imaging. A comparison of FDG-PET and blood flow SPECT in the diagnosis of neurodegenerative dementias: A systematic review. Review of SPECT collimator selection, optimization, and fabrication for clinical and preclinical imaging. One of them is to allow overlapping of projections, i.e., multiplexing, from different pinholes (56). The smallest diameter collimator contains 54 pinholes with a bore diameter of 398 mm. Five pinholes are located on a pinhole plate for the triple-head SPECT system. Busca P, Fiorini C, Butt AD, Occhipinti M, Peloso R, Quagliaet R, al. Lead and tungsten pinhole inserts for I-131 SPECT tumor imaging: experimental measurements and photon transport simulations. The hole diameter is 3 mm and the aperture-to-detector distance is set to 70 mm. Zeraatkar N, Kalluri K, Furenlid LR, Zubal GI, King MA. King MA, Mukherjee JM, Konik A, Zubal IG, Dey J, Licho R. Design of a multi-pinhole collimator for I-123 DaTscan imaging on dual-headed SPECT systems in combination with a fan-beam collimator. It has a C-shaped gantry, which accommodates multiple cadmium zinc telluride (CZT) detectors (Figure 12). Vanhove C, Defrise M, Lahoutte T, Bossuyt A. Three-pinhole collimator to improve axial spatial resolution and sensitivity in pinhole SPECT. Evaluation of early-stage Parkinsons disease with 99mTc-TRODAT-1 imaging. Beekman et al. Photon cross sections, attenuation coefficients, and energy absorption coefficients from 10 keV to 100 GeV 1969 National Bureau of Standards (U.S.) Rep. NSRDS-NBS 29. Wernick MN, Aarsvold JN. The choice of aperture depends on the photon energy for the specific application. Design of a selectable pinhole module for use in adaptive SPECT collimators. (C) Top view showing the 0.3-mm square-pinhole aperture, located 2 mm below the opening on the top, and 5 mm above the large opening on the bottom [courtesy of Moore et al. The MPH collimator provides high resolution and sensitivity for imaging the striatal region and the fan beam collimator provides lower resolution but complete sampling of the brain. (53) and further developed by Xia et al. Fast spiral SPECT with stationary gamma-cameras and focusing pinholes. The 20-pinhole SPECT collimator (Figure 14) was developed at the University of California, San Francisco and is mounted on a GE Inifinia Hawkeye scanner. Highlights lecture EANM 2015: the search for nuclear medicines superheroes. Design and performance of a multi-pinhole collimation device for small animal imaging with clinical SPECT and SPECTCT scanners. Single photon emission computed tomography (SPECT) is an important imaging modality for various applications in nuclear medicine. When gamma rays interact with the detector, the exact location of interaction through the detector along the depth direction is usually unknown. Conversely, collimators with smaller holes provide better spatial resolution with lower sensitivity. The 45 detector modules are arranged in 3 rows in the proposed dynamic MPH cardiac SPECT design [courtesy of Uzun Ozsahin et al. Monte Carlo simulations of a digital mouse phantom with different numbers of pinholes. Uzun Ozsahin D, Blackberg L, Moghadam N, El Fakhri G, Sabet H. GATE simulation of a high-performance stationary SPECT system for cardiac imaging. FRCDC has the least penetration owing to its smallest acceptance angle under the same FOV, making it the best for high energy applications. National Library of Medicine To facilitate early diagnosis for potential treatment, the development of high-resolution brain SPECT is in demand. Bhusal et al. This stationary system has the potential to be integrated with an MRI system. (33)]. (D) Perpendicular cross-section through collimator-detector set-up showing the pinhole geometry. The preliminary prototype design of AdaptiSPECT-C together with a cropped XCAT phantom positioned inside. Van Audenhaege et al. In 2007 Beekman and van der Have (1) provided a comprehensive review on the development of pinhole collimated SPECT technology for preclinical and clinical applications. This article reviews the basic principles of MPH collimators and introduces currently available and proposed clinical MPH SPECT systems. Experimental projections and axial SPECT images from the Defrise phantom imaged under different pinhole configurations [courtesy of Mok et al. Based on the same resolution with the LEHR collimator, the total sensitivity is 0.035%, which is 2.5 times better than LEHR collimator. Each pinhole is coupled to a 7.6 cm wide circular detector with an active area of 7 cm in diameter. For (C), there is ~93% usage with ~33% multiplexing and no truncation. FASTSPECT is a high-resolution dynamic MPH SPECT system dedicated to clinical brain imaging originally proposed by Rowe et al. Conventional photomultiplier tubes (PMTs) should be replaced with SiPMs when designing a SPECT/MRI system, not only due to the fact that PMTs are affected by the strong magnetic field of MRI, but also due to the space constraints of the MRI bore, especially when considering the collimators for SPECT. They evaluated 3 to 12 knife-edge pinholes for each camera with no multiplexing (Figure 24). (42)]. van der Have F, Vastenhouw B, Ramaker RM, Branderhorst W, Krah JO, Ji C, Staelens SG, Beekman FJ. Thus, the reconstruction procedure alternates between two different iterative processes, i.e., first, estimating separated projection data for each pinhole and second, using the separated projection estimates to reconstruct an image.

A collimator is made of high-atomic number and high-density materials such as tungsten and lead which highly absorb incident photons except those traveling through holes of known angulation. where Pmultiplexing and Pnon-zero represent the number of pixels with multiplexing in the projection and number of pixels with non-zero value in the projection, respectively. Pinhole aperture design for 131I tumor imaging. Each camera has an active area of 400 mm 200 mm. Mok et al. Pinhole versus parallel-hole collimators for parathyroid imaging: An intraindividual comparison. where d is the physical hole diameter, is the incident angle, l is the imaging distance, is the attenuation coefficient of the aperture material, and is the acceptance angle of the pinhole (Figure 2). (36)]. (52). In: Proceedings of IEEE NSS-MIC, 2015. The increasing clinical need for dedicated diagnostic systems with improved performance for imaging specific organs, e.g., the heart and brain, has led to the development of single photon emission computed tomography (SPECT) systems with better resolution, sensitivity and throughput (1-12) than standard general-purpose SPECT systems.

(97). DC-SPECT was proposed and evaluated by Uzun Ozsahin et al. Erlandsson K, Kacperski K, van Gramberg D, Hutton BF. Specifications such as pinhole aperture size and number of pinholes open can be adjusted based on individual patients and applications (92). Their design consists of an 8-pinhole collimator that can be integrated to a small FOV gamma camera, especially for thyroid imaging.

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dual cone pinhole sconce