1
|
Choi CH, Felder J, Lerche C, Shah NJ. MRI Coil Development Strategies for Hybrid MR-PET Systems: A Review. IEEE Rev Biomed Eng 2024; 17:342-350. [PMID: 37015609 DOI: 10.1109/rbme.2022.3227337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Simultaneously operating MR-PET systems have the potential to provide synergetic multi-parametric information, and, as such, interest surrounding their use and development is increasing. However, despite the potential advantages offered by fully combined MR-PET systems, implementing this hybrid integration is technically laborious, and any factors degrading the quality of either modality must be circumvented to ensure optimal performance. In order to attain the best possible quality from both systems, most full MR-PET integrations tend to place the shielded PET system inside the MRI system, close to the target volume of the subject. The radiofrequency (RF) coil used in MRI systems is a key factor in determining the quality of the MR images, and, in simultaneous acquisition, it is generally positioned inside the PET system and PET imaging region, potentially resulting in attenuation and artefacts in the PET images. Therefore, when designing hybrid MR-PET systems, it is imperative that consideration be given to the RF coils inside the PET system. In this review, we present current state-of-the-art RF coil designs used for hybrid MR-PET experiments and discuss various design strategies for constructing PET transparent RF coils.
Collapse
|
2
|
Selfridge AR, Cherry SR, Judenhofer MS. Optimization of a depth of interaction encoding PET block detector for a PET/MRI insert. Phys Med Biol 2018; 63:235031. [PMID: 30520420 DOI: 10.1088/1361-6560/aaef59] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Preclinical positron emission tomography, combined with magnetic resonance imaging (PET/MRI), is increasingly used as a tool to simultaneously characterize functional processes in vivo. Many emerging preclinical applications, however, are limited by PET detection sensitivity, especially when generating short imaging frames for quantitative studies. One such application is dynamic multifunctional imaging, which probes multiple aspects of a biological process, using relationships between the datasets to quantify interactions. These studies have limited accuracy due to the relatively low sensitivity of modern preclinical PET/MRI systems. The goal of this project is to develop a preclinical PET/MRI insert with detection sensitivity above 15% (250-750 keV) to improve quantitation in dynamic PET imaging. To achieve this sensitivity, we have developed a detector module incorporating a 2 cm thick crystal block, which will be arranged into a system with 8 cm axial FOV, targeting mice and rats. To maintain homogenous spatial resolution, the detector will incorporate dual-ended depth-of-interaction (DOI) encoding with silicon photomultiplier (SiPM) based photodetector arrays. The specific aim of this work is to identify a detector configuration with adequate performance for the proposed system. We have optimized the SiPM array geometry and tested two crystal array materials with pitch ranging from 0.8 to 1.2 mm and various surface treatments and reflectors. From these configurations, we have identified the best balance between crystal separation, energy resolution, and DOI resolution. The final detector module uses two rectangular SiPM arrays with 5 × 6 and 5 × 4 elements. The photodetector arrays are coupled to a 19 × 19 array of 1 mm pitch LYSO crystals with polished surfaces and a diffuse reflector. The prototype design has 14.3% ± 2.9% energy resolution, 3.57 ± 0.88 mm DOI resolution, and resolves all elements in the crystal array, giving it sufficient performance to serve as the basis for the proposed high sensitivity PET/MRI insert.
Collapse
Affiliation(s)
- Aaron R Selfridge
- Department of Biomedical Engineering, UC Davis, Davis, California, United States of America. Author to whom any correspondence should be addressed
| | | | | |
Collapse
|
3
|
Yamamoto S, Tomita H. Development of a high-resolution alpha-particle imaging system for detection of plutonium particles from the Fukushima Daiichi nuclear power plant. RADIAT MEAS 2018. [DOI: 10.1016/j.radmeas.2018.05.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
|
4
|
Omidvari N, Cabello J, Topping G, Schneider FR, Paul S, Schwaiger M, Ziegler SI. PET performance evaluation of MADPET4: a small animal PET insert for a 7 T MRI scanner. Phys Med Biol 2017; 62:8671-8692. [PMID: 28976912 DOI: 10.1088/1361-6560/aa910d] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
MADPET4 is the first small animal PET insert with two layers of individually read out crystals in combination with silicon photomultiplier technology. It has a novel detector arrangement, in which all crystals face the center of field of view transaxially. In this work, the PET performance of MADPET4 was evaluated and compared to other preclinical PET scanners using the NEMA NU 4 measurements, followed by imaging a mouse-size hot-rod resolution phantom and two in vivo simultaneous PET/MRI scans in a 7 T MRI scanner. The insert had a peak sensitivity of 0.49%, using an energy threshold of 350 keV. A uniform transaxial resolution was obtained up to 15 mm radial offset from the axial center, using filtered back-projection with single-slice rebinning. The measured average radial and tangential resolutions (FWHM) were 1.38 mm and 1.39 mm, respectively. The 1.2 mm rods were separable in the hot-rod phantom using an iterative image reconstruction algorithm. The scatter fraction was 7.3% and peak noise equivalent count rate was 15.5 kcps at 65.1 MBq of activity. The FDG uptake in a mouse heart and brain were visible in the two in vivo simultaneous PET/MRI scans without applying image corrections. In conclusion, the insert demonstrated a good overall performance and can be used for small animal multi-modal research applications.
Collapse
Affiliation(s)
- Negar Omidvari
- Department of Nuclear Medicine, Klinikum rechts der Isar, Technical University of Munich, Ismaninger Str. 22, 81675 Munich, Germany
| | | | | | | | | | | | | |
Collapse
|
5
|
Yamamoto S, Watabe T, Ikeda H, Kanai Y, Ichikawa K, Nakao M, Kato K, Hatazawa J. Development of a PET/OMRI combined system for simultaneous imaging of positron and free radical probes for small animals. Med Phys 2016; 43:5676. [PMID: 27782727 DOI: 10.1118/1.4963215] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Positron emission tomography (PET) has high sensitivity for imaging radioactive tracer distributions in subjects. However, it is not possible to image free radical distribution in a subject by PET. Since free radicals are quite reactive, they are related to many diseases, including but not limited to cancer, inflammation, strokes, and heart disease. The Overhauser enhanced magnetic resonance imaging (OMRI) is so far the only method that images free radical distribution in vivo. By combining PET and OMRI, a new hybrid imaging modality might be developed that can simultaneously image the radioactive tracer and free radical distributions. For this purpose, the authors developed a PET/OMRI combined system for small animals. METHODS The developed PET/OMRI system used an optical fiber-based PET system combined with a permanent magnet-based OMRI system. The optical fiber-based PET system uses flexible optical fiber bundles. Eight optical fiber-based block detectors were arranged in a 56 mm diameter ring to form a PET system. The LGSO blocks were located inside the field-of-view (FOV) of the OMRI, and the position sensitive photomultiplier tubes were positioned behind the OMRI to minimize the interference between the PET and the OMRI. The OMRI system used a 0.0165 T permanent magnet. The system has an electron spin resonance coil to enhance the MRI signal using the Overhauser effect to image the free radical in the FOV of the PET/OMRI system. RESULTS The spatial resolution and sensitivity of the optical fiber-based PET system were 1.2 mm FWHM and 1.2% at the central FOV, respectively. The OMRI system imaged the distribution of a nitroxyl radical (NXR) solution. The interference between PET and OMRI was small. Simultaneous imaging of the positron radiotracer and the NXR solution was successfully conducted with the developed PET/OMRI system for phantom and small animal studies. CONCLUSIONS The authors developed a PET/OMRI combined system with the potential to provide interesting new results in molecular imaging research, such as in vivo molecular and free radical distributions.
Collapse
Affiliation(s)
- Seiichi Yamamoto
- Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya, Aichi 461-8673, Japan
| | - Tadashi Watabe
- Department of Molecular Imaging in Medicine, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan
| | - Hayato Ikeda
- Department of Molecular Imaging in Medicine, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan
| | - Yasukazu Kanai
- Department of Molecular Imaging in Medicine, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan
| | - Kazuhiro Ichikawa
- Innovation Center for Medical Redox Navigation, Kyushu University, Fukuoka 812-8582, Japan
| | | | - Katsuhiko Kato
- Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya, Aichi 461-8673, Japan
| | - Jun Hatazawa
- Department of Molecular Imaging in Medicine, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan
| |
Collapse
|
6
|
Du J, Yang Y, Bai X, Judenhofer MS, Berg E, Di K, Buckley S, Jackson C, Cherry SR. Characterization of Large-Area SiPM Array for PET Applications. IEEE TRANSACTIONS ON NUCLEAR SCIENCE 2016; 63:8-16. [PMID: 27182077 PMCID: PMC4863987 DOI: 10.1109/tns.2015.2499726] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The performance of an 8 × 8 array of 6.0 × 6.0 mm2 (active area) SiPMs was evaluated for PET applications using crystal arrays with different pitch sizes (3.4 mm, 1.5 mm, 1.35 mm and 1.2 mm) and custom designed five-channel front-end readout electronics (four channels for position information and one channel for timing information). The total area of this SiPM array is 57.4 × 57.4 mm2, and the pitch size is 7.2 mm. It was fabricated using enhanced blue sensitivity SiPMs (MicroFB-60035-SMT) with peak spectral sensitivity at 420 nm. The performance of the SiPM array was characterized by measuring flood histogram decoding quality, energy resolution, timing resolution and saturation at several bias voltages (from 25.0 V to 30.0 V in 0.5 V intervals) and two different temperatures (5 °C and 20 °C). Results show that the best flood histogram was obtained at a bias voltage of 28.0 V and 5 °C and an array of polished LSO crystals with a pitch as small as 1.2 mm can be resolved. No saturation was observed up to a bias voltage of 29.5 V during the experiments, due to adequate light sharing between SiPMs. Energy resolution and timing resolution at 5 °C ranged from 12.7 ± 0.8% to 14.6 ± 1.4 % and 1.58 ± 0.13 ns to 2.50 ± 0.44 ns, for crystal array pitch sizes of 3.4 mm and 1.2 mm respectively. Superior flood histogram quality, energy resolution and timing resolution were obtained with larger crystal array pitch sizes and at lower temperature. Based on our findings, we conclude that this large-area SiPM array can serve as a suitable photodetector for high-resolution small-animal PET or dedicated human brain PET scanners.
Collapse
Affiliation(s)
- Junwei Du
- Department of Biomedical Engineering, University of California, Davis, CA 95616 USA
| | - Yongfeng Yang
- Department of Biomedical Engineering, University of California, Davis, CA 95616 USA
| | - Xiaowei Bai
- Department of Biomedical Engineering, University of California, Davis, CA 95616 USA
| | - Martin S Judenhofer
- Department of Biomedical Engineering, University of California, Davis, CA 95616 USA
| | - Eric Berg
- Department of Biomedical Engineering, University of California, Davis, CA 95616 USA
| | - Kun Di
- Department of Biomedical Engineering, University of California, Davis, CA 95616 USA
| | - Steve Buckley
- SensL Technologies Ltd., 6800 Airport Business Park, Cork, Ireland
| | - Carl Jackson
- SensL Technologies Ltd., 6800 Airport Business Park, Cork, Ireland
| | - Simon R Cherry
- Department of Biomedical Engineering, University of California, Davis, CA 95616 USA
| |
Collapse
|
7
|
Yamamoto S, Okumura S, Watabe T, Ikeda H, Kanai Y, Toshito T, Komori M, Ogata Y, Kato K, Hatazawa J. Development of a prototype Open-close positron emission tomography system. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2015; 86:084301. [PMID: 26329212 DOI: 10.1063/1.4929329] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We developed a prototype positron emission tomography (PET) system based on a new concept called Open-close PET, which has two modes: open and close-modes. In the open-mode, the detector ring is separated into two halved rings and subject is imaged with the open space and projection image is formed. In the close-mode, the detector ring is closed to be a regular circular ring, and the subject can be imaged without an open space, and so reconstructed images can be made without artifacts. The block detector of the Open-close PET system consists of two scintillator blocks that use two types of gadolinium orthosilicate (GSO) scintillators with different decay times, angled optical fiber-based image guides, and a flat panel photomultiplier tube. The GSO pixel size was 1.6 × 2.4 × 7 mm and 8 mm for fast (35 ns) and slow (60 ns) GSOs, respectively. These GSOs were arranged into an 11 × 15 matrix and optically coupled in the depth direction to form a depth-of-interaction detector. The angled optical fiber-based image guides were used to arrange the two scintillator blocks at 22.5° so that they can be arranged in a hexadecagonal shape with eight block detectors to simplify the reconstruction algorithm. The detector ring was divided into two halves to realize the open-mode and set on a mechanical stand with which the distance between the two parts can be manually changed. The spatial resolution in the close-mode was 2.4-mm FWHM, and the sensitivity was 1.7% at the center of the field-of-view. In both the close- and open-modes, we made sagittal (y-z plane) projection images between the two halved detector rings. We obtained reconstructed and projection images of (18)F-NaF rat studies and proton-irradiated phantom images. These results indicate that our developed Open-close PET is useful for some applications such as proton therapy as well as other applications such as molecular imaging.
Collapse
Affiliation(s)
- Seiichi Yamamoto
- Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Satoshi Okumura
- Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Tadashi Watabe
- Department of Molecular Imaging in Medicine, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Hayato Ikeda
- Department of Molecular Imaging in Medicine, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Yasukazu Kanai
- Department of Molecular Imaging in Medicine, Osaka University Graduate School of Medicine, Osaka, Japan
| | - Toshiyuki Toshito
- Department of Proton Therapy Physics, Nagoya Proton Therapy Center, Nagoya City West Medical Center, Nagoya, Japan
| | - Masataka Komori
- Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Yoshimune Ogata
- Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Katsuhiko Kato
- Department of Radiological and Medical Laboratory Sciences, Nagoya University Graduate School of Medicine, Nagoya, Japan
| | - Jun Hatazawa
- Department of Molecular Imaging in Medicine, Osaka University Graduate School of Medicine, Osaka, Japan
| |
Collapse
|
8
|
Yamamoto S, Hamamura F, Watabe T, Ikeda H, Kanai Y, Watabe H, Kato K, Ogata Y, Hatazawa J. Development of a PET/Cerenkov-light hybrid imaging system. Med Phys 2014; 41:092504. [DOI: 10.1118/1.4893535] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
|
9
|
Abstract
Hybrid PET/MR systems have rapidly progressed from the prototype stage to systems that are increasingly being used in the clinics. This review provides an overview of developments in hybrid PET/MR systems and summarizes the current state of the art in PET/MR instrumentation, correction techniques, and data analysis. The strong magnetic field requires considerable changes in the manner by which PET images are acquired and has led, among others, to the development of new PET detectors, such as silicon photomultipliers. During more than a decade of active PET/MR development, several system designs have been described. The technical background of combined PET/MR systems is explained and related challenges are discussed. The necessity for PET attenuation correction required new methods based on MR data. Therefore, an overview of recent developments in this field is provided. Furthermore, MR-based motion correction techniques for PET are discussed, as integrated PET/MR systems provide a platform for measuring motion with high temporal resolution without additional instrumentation. The MR component in PET/MR systems can provide functional information about disease processes or brain function alongside anatomic images. Against this background, we point out new opportunities for data analysis in this new field of multimodal molecular imaging.
Collapse
Affiliation(s)
- Jonathan A Disselhorst
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University of Tübingen, Tübingen, Germany; and
| | - Ilja Bezrukov
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University of Tübingen, Tübingen, Germany; and Max-Planck-Institute for Intelligent Systems, Tübingen, Germany
| | - Armin Kolb
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University of Tübingen, Tübingen, Germany; and
| | - Christoph Parl
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University of Tübingen, Tübingen, Germany; and
| | - Bernd J Pichler
- Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University of Tübingen, Tübingen, Germany; and
| |
Collapse
|
10
|
Tamura M, Matsui H, Hirohara S, Kakiuchi K, Tanihara M, Takahashi N, Nakai K, Kanai Y, Watabe H, Hatazawa J. Selective accumulation of [62Zn]-labeled glycoconjugated porphyrins as multi-functional positron emission tomography tracers in cancer cells. Bioorg Med Chem 2014; 22:2563-70. [DOI: 10.1016/j.bmc.2014.02.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2013] [Revised: 02/14/2014] [Accepted: 02/14/2014] [Indexed: 02/05/2023]
|