Assessment of MR compatibility of a PET insert developed for simultaneous multiparametric PET/MR imaging on an animal system operating at 7 T

Wehrl, Hans F.; Judenhofer, Martin S.; Thielscher, Axel; Martirosian, Petros; Schick, Fritz; Pichler, Bernd J.

doi:10.1002/mrm.22591

Cited by 53 publications

(53 citation statements)

References 19 publications

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“…To assess the influence of the PET insert on MR measurement, a uniform corn oil (which has good chemical and thermal stability and appropriate T1, T2, and proton density values that are within the biological range) phantom with T1 and T2 relaxation times of 423 and 130 ms, respectively, was scanned. Main magnetic field (B0) stability, image quality, and temporal stability of image intensity were evaluated following similar procedures used in Wehrl et al and Hong et al (23,24). Great care was taken to ensure that the relative positions of the phantom, radiofrequency coil, and main magnet were not changed during the comparative assessment.…”

Section: Assessment Of Mutual Interference Between Pet and Mrimentioning

confidence: 99%

Simultaneous Multiparametric PET/MRI with Silicon Photomultiplier PET and Ultra-High-Field MRI for Small-Animal Imaging

Yoon

Kim

et al. 2016

J Nucl Med

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Visualization of biologic processes at molecular and cellular levels has revolutionized the understanding and treatment of human diseases. However, no single biomedical imaging modality provides complete information, resulting in the emergence of multimodal approaches. Combining state-of-the-art PET and MRI technologies without loss of system performance and overall image quality can provide opportunities for new scientific and clinical innovations. Here, we present a multiparametric PET/MR imager based on a smallanimal dedicated, high-performance, silicon photomultiplier (SiPM) PET system and a 7-T MR scanner. Methods: A SiPM-based PET insert that has the peak sensitivity of 3.4% and center volumetric resolution of 1.92/0.53 mm 3 (filtered backprojection/ordered-subset expectation maximization) was developed. The SiPM PET insert was placed between the mouse body transceiver coil and gradient coil of a 7-T small-animal MRI scanner for simultaneous PET/MRI. Mutual interference between the MRI and SiPM PET systems was evaluated using various MR pulse sequences. A cylindric corn oil phantom was scanned to assess the effects of the SiPM PET on the MR image acquisition. To assess the influence of MRI on the PET imaging functions, several PET performance indicators including scintillation pulse shape, flood image quality, energy spectrum, counting rate, and phantom image quality were evaluated with and without the application of MR pulse sequences. Simultaneous mouse PET/MRI studies were also performed to demonstrate the potential and usefulness of the multiparametric PET/MRI in preclinical applications. Results: Excellent performance and stability of the PET system were demonstrated, and the PET/MRI combination did not result in significant image quality degradation of either modality. Finally, simultaneous PET/MRI studies in mice demonstrated the feasibility of the developed system for evaluating the biochemical and cellular changes in a brain tumor model and facilitating the development of new multimodal imaging probes. Conclusion: We developed a multiparametric imager with high physical performance and good system stability and demonstrated its feasibility for small-animal experiments, suggesting its usefulness for investigating in vivo molecular interactions of metabolites, and cross-validation studies of both PET and MRI.Key Words: PET/MRI; silicon photomultiplier (SiPM); hybrid imaging; multi-parametric imaging; dual-modality imaging probe Asubst antial role of small-animal imaging has been pinpointed in numerous studies in terms of understanding the underlying mechanism of human diseases and elucidating the efficacy of new therapeutic approaches. Among the in vivo small-animal imaging modalities, which are scaled down to dedicated devices from clinical ones, PET is the most-sensitive technique that is readily translatable to the clinic (1). Spatial and temporal distributions of compounds labeled with a positron-emitting radionuclide are noninvasively measured by the PET scanner. Consequently, the PET scanner p...

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Section: Assessment Of Mutual Interference Between Pet and Mrimentioning

confidence: 99%

Simultaneous Multiparametric PET/MRI with Silicon Photomultiplier PET and Ultra-High-Field MRI for Small-Animal Imaging

Yoon

Kim

et al. 2016

J Nucl Med

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“…Preclinical PET/MR imaging hardware for small-animal studies has advanced (2)(3)(4)12,22,(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40). Although most preclinical PET/MR imaging systems are designed for imaging mice, there is significant interest in cardiac research using rats, especially the spontaneously hypertensive rat model of hypertensive left ventricle hypertrophy.…”

Section: Cardiac Pet/mr Imaging Current State Of Cardiac Pet/mr Imagingmentioning

confidence: 99%

“…However, technology development for rat imaging has been more challenging. To overcome these challenges, a novel imaging system has been designed at the University of Tuebingen (3,4,27,35). This system offers potential for further cardiac research in preclinical studies.…”

Section: Cardiac Pet/mr Imaging Current State Of Cardiac Pet/mr Imagingmentioning

confidence: 99%

Preclinical and Translational PET/MR Imaging

et al. 2014

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Combined PET and MR imaging (PET/MR imaging) has progressed tremendously in recent years. The focus of current research has shifted from technologic challenges to the application of this new multimodal imaging technology in the areas of oncology, cardiology, neurology, and infectious diseases. This article reviews studies in preclinical and clinical translation. The common theme of these initial results is the complementary nature of combined PET/MR imaging that often provides additional insights into biologic systems that were not clearly feasible with just one modality alone. However, in vivo findings require ex vivo validation. Combined PET/MR imaging also triggers a multitude of new developments in image analysis that are aimed at merging and using multimodal information that ranges from better tumor characterization to analysis of metabolic brain networks. The combination of connectomics information that maps brain networks derived from multiparametric MR data with metabolic information from PET can even lead to the formation of a new research field that we would call cometomics that would map functional and metabolic brain networks. These new methodologic developments also call for more multidisciplinarity in the field of molecular imaging, in which close interaction and training among clinicians and a variety of scientists is needed. Mol ecular imaging of small animals for biomedical research is an emerging field (1). It penetrates successfully into areas that are historically dominated by ex vivo molecular biology methods and therefore bears an enormous potential. Exploiting the full range of options of noninvasive visualization and quantification of metabolism, disease-specific dysfunction, therapy response, and cell trafficking requires that specific biomarkers yield information about molecular and functional processes as well as morphologic details. Single-modality imaging, such as stand-alone PET, SPECT, MR imaging, CT, or ultrasound, is often unable to provide the desired comprehensive information. Dedicated small-animal PET/CT and SPECT/CT scanners have been well received in the biomedical imaging sciences and have set the stage for a new combined imaging modality, PET/MR imaging, which has been introduced and successfully applied in biomedical studies (2,3). PET and MR imaging are both distinct modalities offering great versatility for advanced imaging applications in various fields of biomedicine. The combination of these two modalities into a single device merges functional and morphologic information from MR imaging with molecular PET data. The strength of PET lies in its high detection sensitivity and accurate quantification, but PET lacks good spatial resolution and tissue contrast. MR imaging, however, enables highresolution imaging of morphology with good soft-tissue contrast, detects endogenous metabolite distributions using spectroscopy, and allows dynamic acquisition of tissue perfusion and additional functional parameters (4).Thus, PET/MR imaging paves the way for noninvasive imaging to...

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“…A distorted magnetic field can decrease the MR image quality, especially for sequences that particularly rely on field uniformity, such as MR spectroscopy and echo planar imaging. However, several studies have shown that with sufficient shimming, the presence of additional PET hardware does not significantly affect the magnetic field homogeneity (8,9,30).…”

Section: Mrmentioning

confidence: 99%

“…The homogeneity of the radiofrequency field could be influenced by the additional PET components, affecting the flip angle. Only very small radiofrequency field map differences have been reported in preclinical (30) and clinical (8) insert-based PET/MR systems.…”

Section: Mrmentioning

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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Assessment of MR compatibility of a PET insert developed for simultaneous multiparametric PET/MR imaging on an animal system operating at 7 T

Cited by 53 publications

References 19 publications

Simultaneous Multiparametric PET/MRI with Silicon Photomultiplier PET and Ultra-High-Field MRI for Small-Animal Imaging

Simultaneous Multiparametric PET/MRI with Silicon Photomultiplier PET and Ultra-High-Field MRI for Small-Animal Imaging

Preclinical and Translational PET/MR Imaging

Principles of PET/MR Imaging

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