2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)最新文献

{"title":"Directional resolution of limited-angle multi-pinhole SPECT cameras","authors":"Sarah G Cuddy-Walsh, R. Clackdoyle, R. Wells","doi":"10.1109/NSSMIC.2014.7430996","DOIUrl":"https://doi.org/10.1109/NSSMIC.2014.7430996","url":null,"abstract":"Small animal and clinical SPECT cameras based on multi-pinhole detector arrangements typically boast spatial resolutions of 1-2mm and 4mm respectively. However, directional variability of the local imaging capability within the field-of-view (FOV) can impact our ability to detect abnormalities. We aimed to demonstrate the dependence of resolution on object position and orientation within the FOV in a multi-pinhole configuration using a resolution model validated by maximum likelihood expectation maximization (MLEM) reconstructions. The local directional resolution model was based on the smallest angle of view to all pinholes with respect to the normal to the resolution direction. The test configuration was two arcs of 16 pinholes covering 150° in 10° intervals connected by 2 pinholes at each end totaling 36 pinholes. Pinholes were 45mm from the Z-axis, the focal length was 132mm, and detectors were 215mm×215mm leading to a ~28.5mm radius FOV. For validation, a simulated phantom of 3-disks (radius of 5.75mm, 0.75mm thick, and 1.5mm center-to-center spacing) was shifted to different positions in both the X- and Y-directions where differences in resolution were predicted by the theory. At each position the disks were oriented to align their normals with the X and Y-axes. Simulations using idealized pinholes were performed with noise-free forward projections without attenuation and scatter effects (256×256 pixels of 0.84mm×0.84mm in size) and forty iterations of MLEM reconstructions (128-cubed with 0.375mm-cubed voxel size). As predicted by the model, disks with the normal in the Y-direction were reconstructed with nearly uniform resolution at all positions along the X-axis of the FOV. The same was true for disks with the normal in the X-direction at various Y-positions. However, at many of those locations, the resolution behaved poorly when the disk phantom was rotated 90°. Overall, the analytical model and simulations reconstructed using MLEM demonstrated a strong dependence of resolution on position and orientation of an object within the FOV. The greatest resolution losses were observed for positions outside of the hemisphere enclosed by the pinhole array.","PeriodicalId":144711,"journal":{"name":"2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126938340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Efficient Bregman iteration in fully 3D PET","authors":"László Szirmay-Kalos, B. Tóth, G. Jakab","doi":"10.1109/NSSMIC.2014.7430798","DOIUrl":"https://doi.org/10.1109/NSSMIC.2014.7430798","url":null,"abstract":"Positron Emission Tomography reconstruction is ill posed. The result obtained with the iterative ML-EM algorithm is often noisy, which can be controlled by regularization. Common regularization methods penalize high frequency features or the total variation, thus they compromise even valid solutions that have such properties. Bregman iteration offers a better choice enforcing regularization only where needed by the noisy data. Bregman iteration requires a nested optimization, which poses problems when the algorithm is implemented on the GPU where storage space is limited and data transfer is slow. Another problem is that the strength of the regularization is set by a single global parameter, which results in overregularization for voxels measured by fewer LORs. To handle these problems, we propose a modified scheme that merges the two optimization steps into one, eliminating the overhead of Bregman iteration. The algorithm is demonstrated for a 2D test scenario and also in fully 3D reconstruction. The benefits over TV regularization are particularly high if the data has higher variation and point like features. The proposed algorithm is built into the TeraTomo™ system.","PeriodicalId":144711,"journal":{"name":"2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132851799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Optimisation of IQ.SPECT in Myocardial Perfusion Imaging - comparison with conventional SPECT and Echocardiography imaging","authors":"E. Joel, Y. Bouchareb, A. Haroon, M. Luqman, M. Newell, H. Jan","doi":"10.1109/NSSMIC.2014.7430861","DOIUrl":"https://doi.org/10.1109/NSSMIC.2014.7430861","url":null,"abstract":"IQ.SPECT technology performs Myocardial Perfusion Imaging (MPI) in less than five minutes compared to conventional 20-25 minute scans. The aim of this study was to optimise the IQ.SPECT reconstruction and compare with conventional MPI scanning and Echocardiography using perfusion and ECG-gated imaging. 18 patients were imaged using IQ.SPECT in addition to conventional SPECT and the IQ.SPECT reconstruction parameters were optimised to produce comparable findings with conventional SPECT. Images were analysed quantitatively using QPS and QGS software and qualitatively by clinician scoring. IQ.SPECT LVEF values were compared to those obtained using conventional MPI and Echocardiography. Optimum reconstruction parameters for perfusion images were found to be: 6 subsets, 6 iterations, with a Gaussian filter cut-off of 8, and for gated images: 3 subsets, 15 iterations with a Gaussian filter cut-off of 10. No significant difference was found between perfusion images from IQ.SPECT and those from conventional SPECT. IQ.SPECT LVEF values differed, on average, by 15% from those using conventional SPECT and by 25% from those using Echocardiography. The disagreement between LVEF values suggests that caution is needed for borderline LVEF.","PeriodicalId":144711,"journal":{"name":"2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130794667","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparison of transmission- and emission-based attenuation correction for TOF-PET/MRI","authors":"P. Mollet, S. Vandenberghe","doi":"10.1109/NSSMIC.2014.7430783","DOIUrl":"https://doi.org/10.1109/NSSMIC.2014.7430783","url":null,"abstract":"PET quantification requires accurate correction for the attenuation of 511 keV photons in tissue. In PET/CT imaging, the attenuation map is derived from a CT image. Contrary to CT, a direct conversation from MRI intensity values to attenuation coefficients is not applicable. Hence, attenuation correction remains one of the major challenges in the development of PET-MR scanners. Many studies have shown the feasibility of MR-based attenuation correction in clinical practice. However, some drawbacks remain. Alternatively, methods have been suggested to derive the attenuation map from the emission data or by using an external transmission source inside the FOV of the PET scanner. In this work three approaches based on transmission and/or emission data were evaluated and compared with a simulation study using GATE. In the first approach an annulus shaped transmission source was inserted inside the FOV of the PET scanner. An iterative MLTR-MLEM algorithm was used to reconstruct the attenuation and the PET image sequentially. In the second approach only the emission data is used and the attenuation coefficients and the PET image are reconstructed simultaneously with the MLAA algorithm. Finally, an MLAA+ method is proposed in which both the emission and transmission data are used for determining the attenuation map and the PET image simultaneously. Results show that the use of TOF information in the emission-based approach is mandatory and the algorithm can be improved significantly by including additional transmission data coming from an external source, especially in cases where the attenuation medium is not fully supported by the activity distribution. Additionally, the presence of the transmission data allows compensation for the low-frequency cross-talk between the reconstructed attenuation coefficients and the PET image. The absolute error of reconstructed attenuation coefficients in the lungs, soft tissue and spine was respectively more then 40%, 15% and 9% higher when only emission data was used. Contrary, in the MLTR approach, where the transmission-data is extracted from the emission data using TOF information, misclassifications cause inaccuracies in the reconstructed attenuation maps and higher inter-tissue variance in the reconstructed PET image compared to emission based methods. These effects are also reduced when the attenuation map and activity distribution are reconstructed simultaneously.","PeriodicalId":144711,"journal":{"name":"2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130468514","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"MRI-based pseudo-CT generation using sorted atlas images in whole-body PET/MRI","authors":"Hossein ARABI, H. Zaidi","doi":"10.1109/NSSMIC.2014.7430833","DOIUrl":"https://doi.org/10.1109/NSSMIC.2014.7430833","url":null,"abstract":"In this work, we propose a novel approach for MRI-based generation of pseudo-CT images in whole-body PET/MRI based on Hofmann's pattern recognition and atlas registration approach. The major improvement emanates from sorting registered atlas images based on voxelwise local normalized cross-correlation and choosing the most similar atlas image for Gaussian process regression (GPR) analysis. Furthermore, prior knowledge derived from the correlation between lung volume and attenuation coefficients was embedded in the GPR kernel for accurate patient-specific prediction of lung attenuation coefficients. Modifying the GPR algorithm improved the similarity index of bone extraction from 0.55 to 0.61 and enabled significant bias reduction of tracer uptake (SUV) in bony regions. Incorporating prior knowledge about lung volume in the GPR algorithm resulted in SUVmean bias reduction from 8.9% to 4.1% in the whole lung region. Overall, the proposed algorithm provided more accurate PET quantification in the lungs and bony regions.","PeriodicalId":144711,"journal":{"name":"2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130477790","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impact of impurities Cs+, Mg2+, Fe2+, and Sn2+ on scintillation performance of SrI2(Eu)","authors":"S. Lam, S. Swider, A. Datta, S. Motakef","doi":"10.1109/NSSMIC.2014.7431195","DOIUrl":"https://doi.org/10.1109/NSSMIC.2014.7431195","url":null,"abstract":"In this study, the impact of impurities on the scintillation performance of SrI2(Eu) was characterized along with their segregation behavior. Single crystals of SrI2 codoped with 4% Eu and 0.2% X = {Cs, Mg, Fe, Sn} were grown by the vertical Bridgman-Stockbarger method from the melt. Pulse-height gamma ray spectroscopy measurements demonstrated that samples codoped with Cs, Mg, and Fe were slightly degraded in light yield and energy resolution. No significant impact on the decay time and emission peak centroid, 1.5 μs and 428 nm, respectively, were observed. However, the Sn-codoped sample possessed only 55% of the light yield and only half the resolution of SrI2(Eu). In addition to its Eu2+ 5d-4f emission at 428 nm, a broader emission above 550 nm was observed in this sample, accompanied by a shorter decay time of 1.1 μs. Moreover, Sn did not segregate as well as Cs, Mg, and Fe, and thus cannot be removed as easily during growth or zone refining purification. Finally, the results of this study will aid in developing a better understanding of how codoping influences light output.","PeriodicalId":144711,"journal":{"name":"2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131678509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High energy resolution pixel detectors based on boron oxide vertical Bridgman grown CdZnTe crystals","authors":"A. Zappettini, D. Macera, G. Benassi, N. Zambelli, D. Calestani, M. Ahangarianabhari, Yongbiao Shi, G. Rotondo, B. Garavelli, P. Pozzi, G. Bertuccio","doi":"10.1109/NSSMIC.2014.7431283","DOIUrl":"https://doi.org/10.1109/NSSMIC.2014.7431283","url":null,"abstract":"CdZnTe crystals are used for the realization of X-ray detectors. In particular, pixel detectors can be exploited for many application fields such as medical diagnostics, security, and industrial inspection. In the last years, CdZnTe crystals have routinely been grown by the boron oxide encapsulated vertical Bridgman technique. In this work, it is shown that linear array detectors have been prepared based on this material. The detectors show low leakage current and have been coupled to a specifically designed research-grade low noise ASIC. The detectors show good spectroscopic characteristics and no polarization effects, meeting the requirements for the realization of high throughput, multi-energy scanners.","PeriodicalId":144711,"journal":{"name":"2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"133 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131684457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Detection of petawatt laser-induced muon source for rapid high-Z material detection","authors":"W. Dreesen, J. A. Green, M. Browder, J. Wood, D. Schwellenbach, T. Ditmire, G. Tiwari, C. Wagner","doi":"10.1109/NSSMIC.2014.7431088","DOIUrl":"https://doi.org/10.1109/NSSMIC.2014.7431088","url":null,"abstract":"A proof-of-concept investigation of a rapid detection system for shielded high-Z material using a petawatt laser-based muon source is presented. Unlike cosmic-ray muons, a laser-induced muon beam has unique characteristics that can be exploited for use in a rapid detection system. These characteristics include: (1) a near-point source of muons, (2) well-characterized muon energies, (3) directionality of the beam, and (4) well-defined timing of the muons. A detector system is being developed that combines multiple muon detection technologies to characterize an active muon source. This detection system and the associated data acquisition and analysis techniques are designed to search for deflections of the muon beam as it passes through high-Z materials. Additionally, the ability of the system to differentiate muons from the expected secondary particles, such as high-energy gammas and electrons, is being explored. The detector system's ability to differentiate muons from other particles, muon angular distribution, and measured muon flux will be discussed.","PeriodicalId":144711,"journal":{"name":"2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129018083","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A PET/MR compatible device for production of Radiowater","authors":"H. Sipila, V. Haaslahti, V. Saunavaara, M. Teras","doi":"10.1109/NSSMIC.2014.7430870","DOIUrl":"https://doi.org/10.1109/NSSMIC.2014.7430870","url":null,"abstract":"Perfusion studies can be performed with fMRI or using radioactive perfusion tracers such as 15O radiowater. Hybride imaging with PET/MRI allows simultaneous perfusion studies with two different metdos. A novel PET MR compatible Hidex automatic Radiowater Generator (RWG) based on two-membrane diffusion chamber technique was designed. Cyclotron produced 15O2 gas is converted with H2 gas in a furnace to water vapour. A copper RF feed through for radioactive plastic gas lines was installed on the floor of the scanner room next to the Hidex lead shield. O-15 labelled water is led in gas phase, water vapour, under the RF cage into the lead shield of the Hidex RWG. Radioactive water vapour is mixed with saline in a sterile diffusion chamber. The system is designed for continuous and bolus production of radiowater with 600 to 1200 ml/min saline flow. The system can also be used for proton only cyclotrons. The Hidex RWG is designed to fulfil special requirements when installed next to a PET MR device. The Hidex RWG is installed at 3 metres distance from the 3T MRI scanner in about 0.75mT field strength. The lead shield is paramagnetic and in the diffusion chamber integrated pinch valves are operated with compressed air. Positron sensitive radioactivity detectors for recording production rate and the injected dose are based on fibre optics coupled with plastic scintillators. Photomultiplier tubes and all control electronics are installed in the control room of the Philips Ingenuity TF PET MR.","PeriodicalId":144711,"journal":{"name":"2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125351550","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An FBP-type reconstruction method for CBCT with significantly displaced detector","authors":"Li Zhang, Dufan Wu","doi":"10.1109/NSSMIC.2014.7430941","DOIUrl":"https://doi.org/10.1109/NSSMIC.2014.7430941","url":null,"abstract":"In conebeam CT (CBCT), detector displacement is an efficient way to enlarge the field of view (FOV). When the displacement is severe, existing analytical methods will suffer artifacts induced by insufficient sampling. In this work, pre-weighting, post-weighting and Katsevich-type filter backprojection (FBP) as well as backprojection filtration (BPF) methods are investigated for the reconstruction task in dental CBCT. A simple but efficient continuity correction method is proposed for the post-weighting and Katsevich-type FBP. During the padding step, the conjugated projection is scaled by a factor to keep the padded projection continuous. The improved FBP-type algorithm greatly reduced the artifacts brought by the detector displacement. Simulation data and clinical dental CBCT data are used to verify the proposed procedure.","PeriodicalId":144711,"journal":{"name":"2014 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC)","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125495946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}