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| FEATURED STORIES - MARCH 2017 | ||
"The TRIMAGE PET Data Acquisition System: Initial Results"by Giancarlo Sportelli, Salleh Ahmad, Nicola Belcari, Maria Giuseppina Bisogni, Niccolò Camarlinghi, Antonino Di Pasquale, Simeone Dussoni, Julien Fleury, Matteo Morrocchi, Emanuele Zaccaro, and Alberto Del Guerra We present the first results obtained with a prototype of the PET read-out electronics of the trimodal PET/MRI/EEG TRIMAGE scanner. The read-out is based on the 64-channel TRIROC ASIC and on an acquisition board that will control up to 12 ASICs. The output of each ASIC is processed in parallel and sent to a host system that in the final version will receive data from 18 acquisition boards. Blocks of 64 SiPMs are one-to-one coupled to a dual-layer staggered LYSO crystal matrix and read by a single ASIC. The FPGA reads the sparse output from the ASICs and reconstructs for each event a full image of the light pattern coming from the LYSO matrix. This pattern can be then processed on-line or sent to the host PC for post-processing. Early tests were conducted by using a prototype board with single LYSO crystals of 3.3mm×3.3mm×8mm and dual layer staggered LYSO matrices. Results show that the ASIC can sustain input rates above 58 kHz on all its channels, with small variations depending on the discriminating thresholds, being this limit due its digital output stage. With the single crystals setup, we obtained an energy resolution of 10.7% at 511 keV and a coincidence time resolution of 420 ps FWHM. With the staggered matrix the obtained mean energy resolution was 16% on the top layer and 18% on the bottom layer. The flood maps obtained with the LYSO matrix setup show that the pixels on both the staggered levels are clearly identifiable. more... |
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"Crystal Delay and Time Walk Correction Methods for Coincidence Resolving Time Improvements of a Digital-Silicon-Photomultiplier-Based PET/MRI Insert"by David Schug, Bjoern Weissler, Pierre Gebhardt, and Volkmar Schulz Our group has built the MRI compatible PET insert Hyperion IID, which is based on digital silicon photomultipliers [digital photon counters (DPCs)]. We characterized its performance for two different scintillator configurations already in previous publications. For this paper, we reused the raw detector data that were used in previous publications and stored for offline analysis. We reprocessed these data in order to improve the timing performance of the PET scanner. Different crystal delay and time walk calibration and correction methods are evaluated with respect to the coincidence resolving time (CRT) of the scanner. For all applied correction methods, we report CRTs both for a preclinical and a clinical scintillator configuration for all DPC trigger schemes and several energy windows. The newly obtained results were compared with the previously published values, and the additional benefit of using a time walk correction was evaluated. Previously published CRTs could be improved using a refined version of the original crystal delay calibration method without applying a walk correction by 6.3%-10.9% for a wide energy window ranging from 250–625 keV, and we could show an additional improvement of up to 2.6% by adding a walk correction. Using trigger scheme 1 and a very narrow energy window around the photopeak (500–520 keV), we could reach CRT values on system level of 208/240 ps for the clinical/preclinical scintillator configuration. more... |
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"Serial FDG-PET/MR Imaging for Head and Neck Cancer Radiation Therapy: A Pilot Study"by Sharmili Roy, Dennis Lai-Hong Cheong, Jianhua Yan, John J. Totman, Thian Ng, Lih Kin Khor, Julian Goh, and Ivan W. K. Tham Radiation therapy (RT), with or without chemotherapy, can be an effective organ-preserving treatment strategy for many patients with head and neck cancer. Loco-regional failure, however, can occur in a significant minority of patients. Typically, treatment response is assessed months after radiotherapy to allow the tumor to regress and to avoid confounding acute therapy effects. This paper investigates the use of hybrid 18-Flurodeoxyglucose (18F-FDG) positron emission tomography/ magnetic resonance (PET/MR) imaging for early visualization of tumor changes during treatment. Qualitative and quantitative comparison of changes in the anatomical and functional parameters is presented by multi-point serial scanning of head and neck cancer patients undergoing RT. Parameters derived from diffusion weighted imaging and PET imaging are found to trend differently in the patient with recurrence in comparison to patients without recurrence. By reporting feasibility and early findings of PET/MR within treatment, this study suggests that PET/MR has the potential to demonstrate mid-treatment tumor changes. A combination of anatomical and functional parameters can be used to guide potential treatment re-planning for patients who do not respond well to the initially planned treatment strategy more... |
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"Hyperpolarized 13C-MRSI and PET (hyperPET) in an Osteomyelitis Pig Model: A Pilot Study"by Sofie Rahbek, Henrik Gutte, Helle H. Johannesen, Janne Koch, Louise K. Jensen, Kristine Dich-Jorgensen, Henrik E. Jensen, Adam E. Hansen, and Andreas Kjaer Hyperpolarized 13C-pyruvate magnetic resonance spectroscopic imaging (MRSI) is a real-time metabolic imaging technique, which can be combined with positron emission tomography (PET). In this pilot study, we explore the potential of combined hyperpolarized 13C-MRSI and FDG-PET for imaging of infection. METHODS: Three pigs were inoculated with S. aureusbacteria in the right tibia and saline in the left tibial bone. FDG-PET, 1H-MRI and 13C-MRSI was performed using a clinical whole-body PET/MR system (Siemens Biograph mMR, Erlangen, Germany). Hyperpolarized13C-pyruvate was prepared using a SpinLab System (GE Healthcare, Pittsburgh, PA, USA). 13C-lactate to 13C-pyruvate ratio and FDG SUV was reported in anatomical regions of interest covering bone and regions of inflammation and abscess defined on 1H-MRI. Histopathological examination was performed of both legs. RESULTS: An abscess was observed outside the right (infected bone) on 1H-MRI and confirmed by histopathology. In the abscess the 13C-lactate to 13C-pyruvate ratio was increased as compared to the inflammatory region of the control leg. 18F-FDG uptake showed no clear trend when comparing abscess versus inflammation, but showed an increase considering the infected bone versus the control. In the abscess, the FDG-PET signal distribution had highest intensity in the abscess membrane, whereas the maximum of the13C lactate ratio appears in the abscess cavity. DISCUSSION: The apparent different spatial enhancement pattern of FDG uptake and 13C lactate ratio in abscess suggests that they are independent biomarkers and that hyperpolarized 13C-MRSI is a method with potential for clinical imaging of infection and treatment response. more... |
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"Estimation of Left Ventricular Motion from Cardiac Gated Tagged MRI Using an Image-Matching Deformable Mesh Model"by Felipe M. Parages, Thomas S. Denney, Jr., Himanshu Gupta, Steven G. Lloyd, Louis J. Dell'Italia, and Jovan G. Brankov In this paper, we propose a deformable mesh model (DMM) method for left-ventricular (LV) motion-estimation from cardiac-gated tagged magnetic resonance imaging (MRI). DMM starts by partitioning short-axis (SA) and long-axis (LA) images at end-diastole (ED) in a collection of non-overlapping mesh elements (triangles). Next, mesh elements are deformed attempting to track temporal changes in pixel intensities by minimizing an image-matching cost function from frame to frame. Finally, dense motion fields can be obtained at any frame from the displacement of mesh nodes, without any additional user interaction. For validation, 23 human tagged MRI studies were used, allocated as 7 normal, 9 hypertensive (HTN), and 7 with mitral regurgitation (MR). DMM end-systolic (ES) motion and strains were quantitatively compared to a "gold-standard" feature-based (FB) motion analysis method that includes manual tagline editing. DMM motion achieves subpixel average displacement error of SA landmarks with respect to FB. 3-D ES strains obtained from DMM correlate well with FB method (ρ ranging from 0.79 to 0.97). Finally, we show temporal curves for several DMM strain components, grouped according to the condition of patients (normal and diseased). These curves are qualitatively compared to a strain from unwrapped harmonic phase motion estimation algorithm. DMM produces robust temporal curves, which capture strain fluctuations reported in medical literature for HTN and MR conditions. This makes it a viable alternative to analyze motion from images at phases suffering from low contrast-to-noise ratio that may convey important information about the presence of certain cardiac pathologies. more... |
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A PUBLICATION OF THE IEEE NUCLEAR AND PLASMA SCIENCES SOCIETY |
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| MARCH 2017 | VOLUME 1 | NUMBER 2 | ITRPFI | (SSN 2469-7311) | ||
SCINTILLATORS AND DETECTORS Feasible Energy Calibration for Multi-Threshold Photon-Counting Detectors Based on Reconstructed XRF Spectra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . R. Li, L. Li, and Z. Chen CAMERA DESIGN AND IMAGING PERFORMANCE Near Theoretical Gigabit Link Efficiency for Distributed Data Acquisition Systems . . . . . . . . . . . . . . . . F. T. Abu-Nimeh and W.-S. Choong IMAGE RECONSTRUCTION AND DATA PROCESSING A Study of Dynamic PET Frame-Binning on the Reference Logan Binding Potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. Wallstén, J. Axelsson, M. Karlsson, K. Riklund, and A. Larsson Improved PET-Based Voxel-Resolution Myocardial Blood Flow Analysis . . . . . . . . . . . . J. M. M. Anderson, J. R. Votaw, and M. Piccinelli Estimation of Left Ventricular Motion from Cardiac Gated Tagged MRI Using an Image-Matching Deformable Mesh Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F. M. Parages, T. S. Denney, Jr., H. Gupta, S. G. Lloyd, L. J. Dell’Italia, and J. G. Brankov 5TH CONFERENCE ON PET/MR AND SPECT/MR, COLOGNE, GERMANY, MAY 23-25, 2016 Serial FDG-PET/MR Imaging for Head and Neck Cancer Radiation Therapy: A Pilot Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S. Roy, D. L.-H. Cheong, J. Yan, J. J. Totman, T. Ng, L. K. Khor, J. Goh, and I. W. K. Tham Hyperpolarized 13C-MRSI and PET (hyperPET) in an Osteomyelitis Pig Model: A Pilot Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . S. Rahbek, H. Gutte, H. H. Johannesen, J. Koch, L. K. Jensen, K. Dich-Jorgensen, H. E. Jensen, A. E. Hansen, and A. Kjaer The TRIMAGE PET Data Acquisition System: Initial Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G. Sportelli, S. Ahmad, . . . . . . . N. Belcari, M. G.Bisogni, N. Camarlinghi, A. Di Pasquale, S. Dussoni, J. Fleury, M. Morrocchi, E. Zaccaro, and A. Del Guerra Crystal Delay and Time Walk Correction Methods for Coincidence Resolving Time Improvements of a Digital-Silicon- Photomultiplier-Based PET/MRI Insert . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D. Schug, B. Weissler, P. Gebhardt, and V. Schulz Intercrystal Scatter Rejection for Pixelated PET Detectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. Ritzer, P. Hallen, D. Schug, and V. Schulz |
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