The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform

Stephen C. Moore - One of the best experts on this subject based on the ideXlab platform.

  • Review of SPECT Collimator selection, optimization, and fabrication for clinical and preclinical imaging.
    Medical physics, 2015
    Co-Authors: Karen Van Audenhaege, Roel Van Holen, Stefaan Vandenberghe, Christian Vanhove, Scott D. Metzler, Stephen C. Moore
    Abstract:

    In single photon emission computed tomography, the choice of the Collimator has a major impact on the sensitivity and resolution of the system. Traditional parallel-hole and fan-beam Collimators used in clinical practice, for example, have a relatively poor sensitivity and subcentimeter spatial resolution, while in small-animal imaging, pinhole Collimators are used to obtain submillimeter resolution and multiple pinholes are often combined to increase sensitivity. This paper reviews methods for production, sensitivity maximization, and task-based optimization of collimation for both clinical and preclinical imaging applications. New opportunities for improved collimation are now arising primarily because of (i) new Collimator-production techniques and (ii) detectors with improved intrinsic spatial resolution that have recently become available. These new technologies are expected to impact the design of Collimators in the future. The authors also discuss concepts like septal penetration, high-resolution applications, multiplexing, sampling completeness, and adaptive systems, and the authors conclude with an example of an optimization study for a parallel-hole, fan-beam, cone-beam, and multiple-pinhole Collimator for different applications.

  • approximation of hexagonal holes by square holes in monte carlo simulation of gamma camera collimation
    IEEE Transactions on Nuclear Science, 2002
    Co-Authors: D J De Vries, Stephen C. Moore
    Abstract:

    For Monte Carlo simulations, fast calculation of the distance traveled by a photon in the septal material of parallel-hole Collimators can be facilitated by using a square-hole design. Square holes can provide the same geometric efficiency, resolution and lead content (g/cm/sup 2/) as a comparable hexagonal-hole Collimator by appropriate scaling of the hexagonal-hole septal width and hole size. Our objective was to study the validity of using square holes to estimate the hexagonal-hole Collimator response. The geometric, penetration and Collimator scatter components were compared for low-energy (LE) and medium-energy (ME) designs, using square- and hexagonal-holes and a 320 keV point source in air. The resolution (FWHM) was virtually identical for both hole shapes. The amount of penetration, and to a lesser extent Collimator scatter, depended upon hole shape and pattern. However, for a 20% photopeak image, the difference in the total square-hole estimate relative to the hexagonal-hole was 10% and 3% for the LE and ME Collimators, respectively. For an extended source and ME Collimators, the relative difference was 3% for Cr-51 and 0.8% for Ga-67. When the two-dimensional penetration artifact is not critical and a small error in the amount of penetration is acceptable (e.g., when using energy-appropriate Collimators), square-holes can be substituted for hexagonal-holes to decrease by 36% to 50% the time required for simulation.

  • Collimator design for single photon emission tomography.
    European journal of nuclear medicine, 1992
    Co-Authors: Stephen C. Moore, K. Kouris, Ian Cullum
    Abstract:

    We discuss recent trends in Collimator design and technology, with emphasis on theoretical and practical issues of importance for single photon emission tomography (SPET). The well-known imaging performance parameters of parallel-hole Collimators are compared with those of fan-beam Collimators, which have enjoyed considerable success in recent years, particularly for brain SPET. We review a simplistic approach to the Collimator optimization problem, as well as more sophisticated “task-dependent” treatments and important considerations for SPET Collimator design. Practical guidance is offered for understanding trade-offs that must be considered for clinical imaging. Finally, selective comparisons among different SPET systems and Collimators are presented for illustrative purposes.

Michael A King - One of the best experts on this subject based on the ideXlab platform.

  • primary scatter and penetration characterizations of parallel hole and pinhole Collimators for i 123 spect
    Physics in Medicine and Biology, 2019
    Co-Authors: Arda Konik, Benjamin Auer, Jan De Beenhouwer, Kesava Kalluri, Navid Zeraatkar, Lars R Furenlid, Michael A King
    Abstract:

    Multi-pinhole (MPH) Collimators are known to provide better trade-off between sensitivity and resolution for preclinical, as well as for smaller regions in clinical SPECT imaging compared to conventional Collimators. In addition to this geometric advantage, MPH plates typically offer better stopping power for penetration than the conventional Collimators, which is especially relevant for I-123 imaging. The I-123 emits a series of high-energy (>300 keV, ~2.5% abundance) gamma photons in addition to the primary emission (159 keV, 83% abundance). Despite their low abundance, high-energy photons penetrate through a low-energy parallel-hole (LEHR) Collimator much more readily than the 159 keV photons, resulting in large downscatter in the photopeak window. In this work, we investigate the primary, scatter, and penetration characteristics of a single pinhole Collimator that is commonly used for I-123 thyroid imaging and our two MPH Collimators designed for I-123 DaTscan imaging for Parkinson's Disease, in comparison to three different parallel-hole Collimators through a series of experiments and Monte Carlo simulations. The simulations of a point source and a digital human phantom with DaTscan activity distribution showed that our MPH Collimators provide superior count performance in terms of high primary counts, low penetration, and low scatter counts compared to the parallel-hole and single pinhole Collimators. For example, total scatter, multiple scatter, and Collimator penetration events for the LEHR were 2.5, 7.6 and 14 times more than that of MPH within the 15% photopeak window. The total scatter fraction for LEHR was 56% where the largest contribution came from the high-energy scatter from the back compartments (31%). For the same energy window, the total scatter for MPH was 21% with only 1% scatter from the back compartments. We therefore anticipate that using MPH Collimators, higher quality reconstructions can be obtained in a substantially shorter acquisition time for I-123 DaTscan and thyroid imaging.

  • Advantage of pinhole Collimators over parallel hole Collimators in reducing downscatter for I-123 imaging
    2015 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS MIC), 2015
    Co-Authors: Arda Konik, Jan De Beenhouwer, Michael A King
    Abstract:

    Previously, we proposed an inexpensive method to improve the performance of the existing general-purpose dual-camera SPECT systems for brain imaging with I-123 (DaTscan) by using a specifically designed multi-pinhole (MPH) Collimator on one of the detector heads. We present here our preliminary work investigating the downscatter of the low-abundance high-energy photons of I-123 for our MPH Collimator in comparison to a single-pinhole and a parallel-hole Collimator. These investigations were conducted with GATE Monte Carlo simulations and validated with experimental studies on a Philips Prism2000 SPECT system (1.905 cm crystal) for which we have single-pinhole and parallel-hole Collimators. The downscatter fractions (DSF) obtained from the Prism2000 experiments were 26.8% for the parallel-hole (LEUHR) and 3.4% for the single-pinhole Collimators, which are similar to the simulation results: 26.3% for the LEUHR and 4.2% for the single-pinhole. DSF for the MPH (0.9525 cm crystal) was only 1.5% because of the large tungsten Collimator plate. These quantitative results are in good agreement with the energy spectra obtained from the simulations and real acquisitions. Thus, our study shows that an additional benefit of using pinhole systems is the negligible downscatter for I-123 brain imaging.

Seigo Kinuya - One of the best experts on this subject based on the ideXlab platform.

  • Standardization of the heart-to-mediastinum ratio of ^123I-labelled-metaiodobenzylguanidine uptake using the dual energy window method: feasibility of correction with different camera–Collimator combinations
    European Journal of Nuclear Medicine and Molecular Imaging, 2008
    Co-Authors: Shinro Matsuo, Kenichi Nakajima, Koichi Okuda, Masaya Kawano, Takehiro Ishikawa, Tetsuo Hosoya, Junichi Taki, Seigo Kinuya
    Abstract:

    Background Although the heart-to-mediastinum (H/M) ratio in a planar image has been used for practical quantification in ^123I-metaiodobenzylguanidine (MIBG) imaging, standardization of the parameter is not yet established. We hypothesized that the value of the H/M ratio could be standardized to the various camera–Collimator combinations. Methods and results Standard phantoms consisting of the heart and mediastinum were made. A low-energy high-resolution (LEHR) Collimator and a medium-energy (ME) Collimator were used. We examined multi-window correction methods with ^123I- dual-window (IDW) acquisition, and planar images were obtained with IDW correction and the LEHR Collimator. The images were obtained using the following gamma camera systems: GCA 9300A (Toshiba, Tokyo), E.CAM Signature (Toshiba/Siemens, Tokyo) and Varicam (GE, Tokyo). Cardiac phantom studies demonstrated that contamination of the H/M count ratio was greater with the LEHR Collimator and least with the ME Collimator. The corrected H/M ratio with the LEHR Collimator was similar to that with ME Collimators. The uncorrected H/M ratio with the ME Collimator was linearly related to the H/M ratio with IDW correction with the LEHR Collimator. The relationship between the uncorrected H/M ratios determined with the LEHR (E.CAM) and the ME Collimators was y  = 0.56 x  + 0.49, where y = H/M ratio with the E.CAM and x = H/M ratio with the ME Collimator. The average normal values for the low-energy Collimator ( n =18) were 2.2±0.2 (initial H/M ratio) and 2.42±0.2 (delayed H/M ratio), and for the low/medium-energy (LME) Collimator ( n =14) were 2.63±0.25 (initial H/M ratio) and 2.87±0.19 (delayed H/M ratio). H/M ratios in previous clinical studies using LEHR Collimators are comparable to those with ME Collimators. Conclusion The IDW-corrected H/M ratios determined with the LEHR Collimator were similar to those determined with the ME Collimator. This finding could make it possible to standardize the H/M ratio in planar imaging among various Collimators in the clinical setting.

  • correction of iodine 123 labeled meta iodobenzylguanidine uptake with multi window methods for standardization of the heart to mediastinum ratio
    Journal of Nuclear Cardiology, 2007
    Co-Authors: Kenichi Nakajima, Koichi Okuda, Takehiro Ishikawa, Junichi Taki, Kosuke Matsubara, Nobutoku Motomura, Ryo Maeda, Nasima Akhter, Seigo Kinuya
    Abstract:

    Background To overcome differences in the choice of Collimator for an iodine-123 (123I)-labeled meta-iodobenzylguanidine (MIBG) heart-to-mediastinum (H/M) ratio, we examined multi-window correction methods with 123I dual-window (IDW) and triple-energy window (TEW) acquisition. Methods and Results Standard phantoms, which consisted of the heart, mediastinum, lung, and liver, were generated. Three correction methods were compared: TEW and two IDW methods (IDW0 and IDW1). Low-energy high-resolution (LEHR), medium-energy (ME), and 123I-specific low-medium-energy high-resolution (LMEHR) Collimators were used. Clinical studies were performed in 10 patients. In the phantom study, the H/M ratio was significantly underestimated without correction, with both the LEHR and ME Collimators (70% and 88% of the true value). When H/M with the LEHR Collimator was divided by uncorrected H/M with the ME Collimator, the ratio (mean ± SD) was 80% ± 5%, 98% ± 5%, 104% ± 7%, and 98% ± 5% for the no-correction, TEW, IDW0, and IDW1 methods, respectively. Clinical studies with the LEHR Collimator after TEW and IDW correction (uncorrected average H/M ratio, 1.86 ± 0.23; TEW, 2.47 ± 0.46, P = .0015; IDW, 2.46 ± 0.46, P = .0017) provided comparable values to the uncorrected ME Collimator (2.56 ± 0.46, P = NS vs TEW and IDW). Conclusions The H/M ratio with the ME Collimator, after application of the TEW or IDW methods, was close to the theoretical value in the phantom study. However, the corrected H/M ratios with the LEHR Collimator provided comparable H/M ratios to the uncorrected ME data in phantom and clinical studies.

Yusuke Inoue - One of the best experts on this subject based on the ideXlab platform.

  • acquisition protocols and correction methods for estimation of the heart to mediastinum ratio in 123i metaiodobenzylguanidine cardiac sympathetic imaging
    The Journal of Nuclear Medicine, 2013
    Co-Authors: Yusuke Inoue, Yutaka Abe, Yoshihiro Itoh, Yuji Asano, Kei Kikuchi, Yutaka Sakamoto, Keiji Matsunaga, Yutaka Ogino, Takahiro Iizuka, Hideki Mochizuki
    Abstract:

    UNLABELLED: Septal penetration of high-energy photons affects quantitative results in imaging of (123)I-labeled tracers. We investigated acquisition protocols (Collimator choice and energy window setting) and correction methods for estimating the heart-to-mediastinum (H/M) ratio in cardiac (123)I-metaiodobenzylguanidine (MIBG) imaging. METHODS: Four hours after (123)I-MIBG injection, 40 patients successively underwent planar anterior chest imaging with the medium-energy (ME) (ME method) and low-energy high-resolution (LEHR) (LEHR method) Collimators. A 20% energy window was used for both Collimators. Another 40 patients were imaged successively with the ME Collimator and a 20% window (ME method), the low-medium-energy (LME) Collimator and a 20% window (LME20 method), and the LME Collimator and a 15% window (LME15 method). The H/M ratios obtained by the LEHR, LME20, and LME15 methods were corrected using their correlations with the H/M ratio obtained by the ME method (empiric correction). The (123)I-dual-window (IDW) correction was also applied to remove the influence of high-energy photons. RESULTS: Without correction, severe underestimation of the H/M ratio was shown for the LEHR method using the ME method as a standard, and this underestimation increased with increasing H/M ratios. Underestimation substantially decreased using the LME20 method and further using the LME15 method. Empiric correction reduced the error in the H/M ratio by the LEHR method, but the error was still evident. After empiric correction, the H/M ratios with the LME Collimator were comparable to those with the ME Collimator. The IDW correction only partially reduced underestimation by the LEHR method and caused a small overestimation for the LME15 method. CONCLUSION: The use of an LME Collimator appears to be acceptable for cardiac (123)I-MIBG imaging as an alternative to an ME Collimator, and the application of a 15% energy window is recommended when an LME Collimator is used. Empiric correction is also expected to improve exchangeability between H/M ratios calculated with ME and LME Collimators. Neither the use of an LEHR Collimator nor the use of IDW correction is recommended.

  • effect of Collimator choice on quantitative assessment of cardiac iodine 123 mibg uptake
    Journal of Nuclear Cardiology, 2003
    Co-Authors: Yusuke Inoue, Akira Suzuki, Ichiro Shirouzu, Toru Machida, Yasunori Yoshizawa, Fumihide Akita, Satoshi Ohnishi, Kohki Yoshikawa, Kuni Ohtomo
    Abstract:

    Abstract Background Quantitative accuracy in iodine 123 studies may be impaired by septal penetration. We evaluated the effect of Collimator choice on estimation of the heart-to-mediastinum (H/M) ratio in cardiac I-123 metaiodobenzylguanidine (MIBG) imaging. Methods and results A low-energy high-resolution (LEHR) Collimator, special LEHR (SLEHR) Collimator, and medium-energy (ME) Collimator were used. In experiments in which a phantom of simple geometry was used, the use of the LEHR Collimator provided the lowest contrast accuracy, suggesting the effect of septal penetration. Thoracic phantom studies demonstrated contamination of heart and mediastinum counts by lung and liver activities, which was greatest with the LEHR Collimator and least with the ME Collimator. In 8 patients anterior chest views were acquired successively with the three Collimators after I-123 MIBG injection. H/M ratios were significantly higher with the SLEHR Collimator than with the LEHR Collimator and were still higher with the ME Collimator. The difference in H/M ratios between the LEHR and ME Collimators showed a high positive correlation with the lung-to-mediastinum ratio. Conclusions Collimator choice substantially influences estimation of the H/M ratios in cardiac I-123 MIBG imaging. The use of an ME Collimator provides high quantitative accuracy and may enhance reliability in the evaluation of cardiac sympathetic nerve function.

R.c. Reba - One of the best experts on this subject based on the ideXlab platform.

  • Performance comparison of ultra-ultra high resolution Collimators to low-energy high resolution Collimators
    The Journal of Nuclear Medicine, 2012
    Co-Authors: Christopher Leyson, Jurgen Seidel, Roberto Maass-moreno, R.c. Reba
    Abstract:

    2409 Objectives We compared the performance of a unique ultra-ultra high resolution (UUHR) Collimator to that of a low-energy high resolution (LEHR) Collimator. The UUHR Collimator was designed to accommodate SPECT scanning in a biosafety level-4 (BSL-4) environment where a containment tube spanning the BSL-4 area and the imaging room limits the SPECT orbit. Methods We measured the system spatial resolution (FWHM) and the Collimator sensitivity following the NEMA performance standard. Reconstructed SPECT image resolution was determined using three 99mTc point sources inside the containment tube. In addition, we acquired SPECT images of a Jaszczak resolution phantom (Data Spectrum, Hillsborough NC) containing hot spheres to measure recovery coefficients. Results Resolution degradation at increasing distance from the Collimators was less for UUHR Collimators than for LEHR Collimators. With UUHR Collimators, we achieved a similar resolution at 35 cm as with LEHR Collimators at 20 cm. Collimator sensitivity at 10 cm was 56.4 cpm/µCi (UUHR) and 168 cpm/μCi (LEHR). At a 33-cm radius orbit, the SPECT resolution of a central point source was 10.6 mm (transaxial) and 11.2 mm (axial) with UUHR Collimators, whereas resolution deteriorated to 17.3 mm (transaxial) and 18.8 mm (axial) with LEHR Collimators. The two largest of six total groups of rods in the resolution phantom were resolved in UUHR-collimated images but not in the LEHR-collimated images. Recovery coefficients for a 25-mm diameter sphere were 1.02 (UUHR Collimators) and 0.72 (LEHR Collimators). Conclusions By using UUHR Collimators, we achieved a SPECT resolution of about 10-12 mm FWHM in our BSL-4 setting, which is similar to the resolution typically obtained in clinical settings using LEHR Collimators. However, the improvement in spatial resolution with UUHR Collimators comes at the price of reduced sensitivity compared to LEHR Collimators. Research Support This work was performed under Battelle Memorial contract HHSN272200200016I with NIAID