PET/MRI insert using digital SiPMs: Investigation of MR-compatibility

Wehner, Jakob; Weissler, Bjöern; Dueppenbecker, Peter Michael; Gebhardt, Pierre; Schug, David; Ruetten, Walter; Kießling, Fabian; Schulz, Volkmar

doi:10.1016/j.nima.2013.08.077

Cited by 56 publications

(72 citation statements)

References 13 publications

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“…Some authors have reported on the performance parameters of SiPM-based full-ring preclinical PET systems or MRI inserts (4,10,18,19). However, only some of the NEMA NU 4 measurement protocols have been performed on these systems.…”

Section: Discussionmentioning

confidence: 99%

“…A limitation of this study is that we did not take into account the performance of the systems in high magnetic fields. However, other research groups have already proved the stability and proper performance of SiPMs in MRI systems (18,19). Although both MiniPET systems have a relatively small field of view compared with other preclinical PET systems (16,21,25), the main goal of this study was to compare SiPM with PMT technology while keeping scintillation crystal geometry, system matrix, slice rebinning algorithm, and even image reconstruction identical.…”

Section: Discussionmentioning

confidence: 99%

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A Promising Future: Comparable Imaging Capability of MRI-Compatible Silicon Photomultiplier and Conventional Photosensor Preclinical PET Systems

et al. 2015

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We recently completed construction of a small-animal PET systemthe MiniPET-3-that uses state-of-the-art silicon photomultiplier (SiPM) photosensors, making possible dual-modality imaging with MRI. In this article, we compare the MiniPET-3 with the MiniPET-2, a system with the same crystal geometry but conventional photomultiplier tubes (PMTs). Methods: The standard measurements proposed by the National Electrical Manufacturers Association NU 4 protocols were performed on both systems. These measurements included spatial resolution, system sensitivity, energy resolution, counting rate performance, scatter fraction, spillover ratio for air and water, recovery coefficient, and image uniformity. The energy windows were set to 350-650 keV on the MiniPET-2 and 360-662 keV on the MiniPET-3. Results: Spatial resolution was approximately 17% better on average for the MiniPET-3 than the MiniPET-2. The systems performed similarly in terms of peak absolute sensitivity (∼1.37%), spillover ratio for air (∼0.15), spillover ratio for water (∼0.25), and recovery coefficient (∼0.33, 0.59, 0.81, 0.89, and 0.94). Uniformity was 5.59% for the MiniPET-2 and 6.49% for the MiniPET-3. Minor differences were found in scatter fraction. With the ratlike phantom, the peak noise-equivalent counting rate was 14 kcps on the MiniPET-2 but 24 kcps on the MiniPET-3. However, with the mouselike phantom, these values were 55 and 91 kcps, respectively. The optimal coincidence time window was 6 ns for the MiniPET-2 and 8 ns for the MiniPET-3. Conclusion: Images obtained with the SiPM-based Mini-PET-3 small-animal PET system are similar in quality to those obtained with the conventional PMT-based MiniPET-2.Key Words: MiniPET; small-animal PET scanner; performance evaluation; instrumentation; molecular imaging J Nucl Med 2015; 56:1948 56: -1953 56: DOI: 10.2967 Ef forts to integrate PET and MRI have advanced significantly in recent years, fostered mainly by new photosensor technologies (1-4). Conventional photomultiplier tube (PMT) detectors benefit from high signal gain in the range of 10 5 -10 7 (5,6). Low noise and fast transit time (;100 ps) are also available today and have made PMTs the first candidate for applications involving time-of-flight PET technology. In addition, PMTs have lower noise than avalanche photodiode or silicon photomultiplier (SiPM) detectors (5). However, in strong magnetic fields PMTs cannot produce position maps that are acceptable for imaging purposes. In contrast, avalanche photodiodes can be used efficiently as a photosensor for PET when near strong magnets. Some successful approaches using avalanche photodiodes have already been introduced for combined PET/MRI applications (2,7,8). However, avalanche photodiodes have significantly higher rise times than PMTs (up to 2-3 ns) (5), preventing the timing resolution from being adequate for time-of-flight PET. The low gain (;10 2 ) is also a disadvantage of avalanche photodiodes (2,5).By coupling lutetium oxyorthosilicate crystals with new SiPM technology, a timing resolutio...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

A Promising Future: Comparable Imaging Capability of MRI-Compatible Silicon Photomultiplier and Conventional Photosensor Preclinical PET Systems

et al. 2015

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“…Wehner et al (19) based on SiPM technology with fully front-end digitizers. The signals from PET detectors are directly digitized and processed within the magnetic field.…”

Section: Petmentioning

confidence: 99%

Principles of PET/MR Imaging

et al. 2014

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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.

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“…For example, digital optical communication over fiber was used to avoid electrical data connections in an MRI-compatible preclinical PET scanner. 11,12 While this technique has the advantage of avoiding the mutual interference that can accompany electrical cables, digitally compresses event data onto a single fiber, and achieves excellent timing resolution, it also requires digital processing electronics housed within the detector modules. These components can draw high power, generate considerable heat, and require more stringent shielding design for operation in an MRI.…”

Section: Introductionmentioning

confidence: 99%

Optical delay encoding for fast timing and detector signal multiplexing in PET

Grant

Levin

2015

Medical Physics

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Purpose: The large number of detector channels in modern positron emission tomography (PET) scanners poses a challenge in terms of readout electronics complexity. Multiplexing schemes are typically implemented to reduce the number of physical readout channels, but often result in performance degradation. Novel methods of multiplexing in PET must be developed to avoid this data degradation. The preservation of fast timing information is especially important for time-of-flight PET. Methods: A new multiplexing scheme based on encoding detector interaction events with a series of extremely fast overlapping optical pulses with precise delays is demonstrated in this work. Encoding events in this way potentially allows many detector channels to be simultaneously encoded onto a single optical fiber that is then read out by a single digitizer. A two channel silicon photomultiplier-based prototype utilizing this optical delay encoding technique along with dual threshold time-over-threshold is demonstrated. Results: The optical encoding and multiplexing prototype achieves a coincidence time resolution of 160 ps full width at half maximum (FWHM) and an energy resolution of 13.1% FWHM at 511 keV with 3 × 3 × 5 mm 3 LYSO crystals. All interaction information for both detectors, including timing, energy, and channel identification, is encoded onto a single optical fiber with little degradation. Conclusions: Optical delay encoding and multiplexing technology could lead to time-of-flight PET scanners with fewer readout channels and simplified data acquisition systems. C 2015 American Association of Physicists in Medicine. [http://dx

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PET/MRI insert using digital SiPMs: Investigation of MR-compatibility

Cited by 56 publications

References 13 publications

A Promising Future: Comparable Imaging Capability of MRI-Compatible Silicon Photomultiplier and Conventional Photosensor Preclinical PET Systems

A Promising Future: Comparable Imaging Capability of MRI-Compatible Silicon Photomultiplier and Conventional Photosensor Preclinical PET Systems

Principles of PET/MR Imaging

Optical delay encoding for fast timing and detector signal multiplexing in PET

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