Characterization of a preclinical PET insert in a 7 tesla MRI scanner: beyond NEMA testing

[EN] This study evaluates the performance of the Bruker positron emission tomograph (PET) insert combined with a BioSpec 70/30 USR magnetic resonance imaging (MRI) scanner using the manufacturer acceptance protocol and the NEMA NU 4-2008 for small animal PET. The PET insert is made of 3 rings of 8 monolithic LYSO crystals (50 x 50 x 10 mm(3)) coupled to silicon photomultipliers (SiPM) arrays, conferring an axial and transaxial FOV of 15 cm and 8 cm. The MRI performance was evaluated with and without the insert for the following radiofrequency noise, magnetic field homogeneity and image quality. For the PET performance, we extended the NEMA protocol featuring system sensitivity, count rates, spatial resolution and image quality to homogeneity and accuracy for quantification using several MRI sequences (RARE, FLASH, EPI and UTE). The PET insert does not show any adverse effect on the MRI performances. The MR field homogeneity is well preserved (Diameter Spherical Volume, for 20 mm of 1.98 +/- 4.78 without and -0.96 +/- 5.16 Hz with the PET insert). The PET insert has no major effect on the radiofrequency field. The signal-to-noise ratio measurements also do not show major differences. Image ghosting is well within the manufacturer specifications (<2.5%) and no RF noise is visible. Maximum sensitivity of the PET insert is 11.0% at the center of the FOV even with simultaneous acquisition of EPI and RARE. PET MLEM resolution is 0.87 mm (FWHM) at 5 mm off-center of the FOV and 0.97 mm at 25 mm radial offset. The peaks for true/noise equivalent count rates are 410/240 and 628/486 kcps for the rat and mouse phantoms, and are reached at 30.34/22.85 and 27.94/22.58 MBq. PET image quality is minimally altered by the different MRI sequences. The Bruker PET insert shows no adverse effect on the MRI performance and demonstrated a high sensitivity, sub-millimeter resolution and good image quality even during simultaneous MRI acquisition.We acknowledge the KU Leuven core facility, Molecular Small Animal Imaging Center (MoSAIC), for their support with obtaining scientific data presented in this paper. This work was supported by Stichting tegen Kanker (2015-145, Christophe M. Deroose) and Hercules foundation (AKUL/13/029, Uwe Himmelreich) for the purchase of the PET and MRI equipment respectively. The work was supported by the following funding organizations: European Commission for the PANA project (H2020-NMP-2015-two-stage, grant 686009) and the European ERA-NET project 'CryptoView' (3rd call of the FP7 program Infect-ERA).Gsell, W.; Molinos, C.; Correcher, C.; Belderbos, S.; Wouters, J.; Junge, S.; Heidenreich, M.... (2020). Characterization of a preclinical PET insert in a 7 tesla MRI scanner: beyond NEMA testing. Physics in Medicine and Biology. 65(24):1-16. https://doi.org/10.1088/1361-6560/aba08cS1166524Balezeau, F., Eliat, P.-A., Cayamo, A. B., & Saint-Jalmes, H. (2011). Mapping of low flip angles in magnetic resonance. Physics in Medicine and Biology, 56(20), 6635-6647. doi:10.1088/0031-9155/56/20/008Benlloch, J. M., González, A. J., Pani, R., Preziosi, E., Jackson, C., Murphy, J., … Schwaiger, M. (2018). The MINDVIEW project: First results. European Psychiatry, 50, 21-27. doi:10.1016/j.eurpsy.2018.01.002Cal-Gonzalez, J., Rausch, I., Shiyam Sundar, L. K., Lassen, M. L., Muzik, O., Moser, E., … Beyer, T. (2018). Hybrid Imaging: Instrumentation and Data Processing. Frontiers in Physics, 6. doi:10.3389/fphy.2018.00047Clark, D. P., & Badea, C. T. (2014). Micro-CT of rodents: State-of-the-art and future perspectives. Physica Medica, 30(6), 619-634. doi:10.1016/j.ejmp.2014.05.011Drzezga, A., Souvatzoglou, M., Eiber, M., Beer, A. J., Fürst, S., Martinez-Möller, A., … Schwaiger, M. (2012). First Clinical Experience with Integrated Whole-Body PET/MR: Comparison to PET/CT in Patients with Oncologic Diagnoses. Journal of Nuclear Medicine, 53(6), 845-855. doi:10.2967/jnumed.111.098608Gonzalez, A. J., Aguilar, A., Conde, P., Hernandez, L., Moliner, L., Vidal, L. F., … Benlloch, J. M. (2016). A PET Design Based on SiPM and Monolithic LYSO Crystals: Performance Evaluation. IEEE Transactions on Nuclear Science, 63(5), 2471-2477. doi:10.1109/tns.2016.2522179Gonzalez, A. J., Pincay, E. J., Canizares, G., Lamprou, E., Sanchez, S., Catret, J. V., … Correcher, C. (2019). Initial Results of the MINDView PET Insert Inside the 3T mMR. IEEE Transactions on Radiation and Plasma Medical Sciences, 3(3), 343-351. doi:10.1109/trpms.2018.2866899Grant, A. M., Lee, B. J., Chang, C.-M., & Levin, C. S. (2017). Simultaneous PET/MR imaging with a radio frequency-penetrable PET insert. Medical Physics, 44(1), 112-120. doi:10.1002/mp.12031Habte, F., Ren, G., Doyle, T. C., Liu, H., Cheng, Z., & Paik, D. S. (2013). Impact of a Multiple Mice Holder on Quantitation of High-Throughput MicroPET Imaging With and Without Ct Attenuation Correction. Molecular Imaging and Biology, 15(5), 569-575. doi:10.1007/s11307-012-0602-yHammer, B. E., Christensen, N. L., & Heil, B. G. (1994). Use of a magnetic field to increase the spatial resolution of positron emission tomography. Medical Physics, 21(12), 1917-1920. doi:10.1118/1.597178Jadvar, H., & Colletti, P. M. (2014). Competitive advantage of PET/MRI. European Journal of Radiology, 83(1), 84-94. doi:10.1016/j.ejrad.2013.05.028Judenhofer, M. S., Catana, C., Swann, B. K., Siegel, S. B., Jung, W.-I., Nutt, R. E., … Pichler, B. J. (2007). PET/MR Images Acquired with a Compact MR-compatible PET Detector in a 7-T Magnet. Radiology, 244(3), 807-814. doi:10.1148/radiol.2443061756Kinahan, P. E., Townsend, D. W., Beyer, T., & Sashin, D. (1998). Attenuation correction for a combined 3D PET/CT scanner. Medical Physics, 25(10), 2046-2053. doi:10.1118/1.598392Ko, G. B., Yoon, H. S., Kim, K. Y., Lee, M. S., Yang, B. Y., Jeong, J. M., … Lee, J. S. (2016). Simultaneous Multiparametric PET/MRI with Silicon Photomultiplier PET and Ultra-High-Field MRI for Small-Animal Imaging. Journal of Nuclear Medicine, 57(8), 1309-1315. doi:10.2967/jnumed.115.170019Lee, B. J., Grant, A. M., Chang, C.-M., Watkins, R. D., Glover, G. H., & Levin, C. S. (2018). MR Performance in the Presence of a Radio Frequency-Penetrable Positron Emission Tomography (PET) Insert for Simultaneous PET/MRI. IEEE Transactions on Medical Imaging, 37(9), 2060-2069. doi:10.1109/tmi.2018.2815620Loening, A. M., & Gambhir, S. S. (2003). AMIDE: A Free Software Tool for Multimodality Medical Image Analysis. Molecular Imaging, 2(3), 131-137. doi:10.1162/153535003322556877Mannheim, J. G., Schmid, A. M., Schwenck, J., Katiyar, P., Herfert, K., Pichler, B. J., & Disselhorst, J. A. (2018). PET/MRI Hybrid Systems. Seminars in Nuclear Medicine, 48(4), 332-347. doi:10.1053/j.semnuclmed.2018.02.011Maramraju, S. H., Smith, S. D., Junnarkar, S. S., Schulz, D., Stoll, S., Ravindranath, B., … Schlyer, D. J. (2011). Small animal simultaneous PET/MRI: initial experiences in a 9.4 T microMRI. Physics in Medicine and Biology, 56(8), 2459-2480. doi:10.1088/0031-9155/56/8/009Molinos, C., Sasser, T., Salmon, P., Gsell, W., Viertl, D., Massey, J. C., … Heidenreich, M. (2019). Low-Dose Imaging in a New Preclinical Total-Body PET/CT Scanner. Frontiers in Medicine, 6. doi:10.3389/fmed.2019.00088Nagy, K., Tóth, M., Major, P., Patay, G., Egri, G., Häggkvist, J., … Gulyás, B. (2013). Performance Evaluation of the Small-Animal nanoScan PET/MRI System. Journal of Nuclear Medicine, 54(10), 1825-1832. doi:10.2967/jnumed.112.119065Nanni, C., & Torigian, D. A. (2008). Applications of Small Animal Imaging with PET, PET/CT, and PET/MR Imaging. PET Clinics, 3(3), 243-250. doi:10.1016/j.cpet.2009.01.002Omidvari, N., Cabello, J., Topping, G., Schneider, F. R., Paul, S., Schwaiger, M., & Ziegler, S. I. (2017). PET performance evaluation of MADPET4: a small animal PET insert for a 7 T MRI scanner. Physics in Medicine & Biology, 62(22), 8671-8692. doi:10.1088/1361-6560/aa910dOmidvari, N., Topping, G., Cabello, J., Paul, S., Schwaiger, M., & Ziegler, S. I. (2018). MR-compatibility assessment of MADPET4: a study of interferences between an SiPM-based PET insert and a 7 T MRI system. Physics in Medicine & Biology, 63(9), 095002. doi:10.1088/1361-6560/aab9d1Raylman, R. R., Majewski, S., Lemieux, S. K., Velan, S. S., Kross, B., Popov, V., … Marano, G. D. (2006). Simultaneous MRI and PET imaging of a rat brain. Physics in Medicine and Biology, 51(24), 6371-6379. doi:10.1088/0031-9155/51/24/006Roncali, E., & Cherry, S. R. (2011). Application of Silicon Photomultipliers to Positron Emission Tomography. Annals of Biomedical Engineering, 39(4), 1358-1377. doi:10.1007/s10439-011-0266-9Schug, D., Lerche, C., Weissler, B., Gebhardt, P., Goldschmidt, B., Wehner, J., … Schulz, V. (2016). Initial PET performance evaluation of a preclinical insert for PET/MRI with digital SiPM technology. Physics in Medicine and Biology, 61(7), 2851-2878. doi:10.1088/0031-9155/61/7/2851Shao, Y., Cherry, S. R., Farahani, K., Meadors, K., Siegel, S., Silverman, R. W., & Marsden, P. K. (1997). Simultaneous PET and MR imaging. Physics in Medicine and Biology, 42(10), 1965-1970. doi:10.1088/0031-9155/42/10/010Steinert, H. C., & von Schulthess, G. K. (2002). Initial clinical experience using a new integrated in-line PET/CT system. The British Journal of Radiology, 75(suppl_9), S36-S38. doi:10.1259/bjr.75.suppl_9.750036Stortz, G., Thiessen, J. D., Bishop, D., Khan, M. S., Kozlowski, P., Retière, F., … Sossi, V. (2017). Performance of a PET Insert for High-Resolution Small-Animal PET/MRI at 7 Tesla. Journal of Nuclear Medicine, 59(3), 536-542. doi:10.2967/jnumed.116.187666Townsend, D. W. (2008). Combined Positron Emission Tomography–Computed Tomography: The Historical Perspective. Seminars in Ultrasound, CT and MRI, 29(4), 232-235. doi:10.1053/j.sult.2008.05.006Vandenberghe, S., & Marsden, P. K. (2015). PET-MRI: a review of challenges and solutions in the development of integrated multimodality imaging. Physics in Medicine and Biology, 60(4), R115-R154. doi:10.1088/0031-9155/60/4/r115Vaquero, J. J., & Kinahan, P. (2015). Positron Emission Tomography: Current Challenges and Opportunities for Technological Advances in Clinical and Preclinical Imaging Systems. Annual Review of Biomedical Engineering, 17(1), 385-414. doi:10.1146/annurev-bioeng-071114-040723Von Schulthess, G. K., & Schlemmer, H.-P. W. (2008). A look ahead: PET/MR versus PET/CT. European Journal of Nuclear Medicine and Molecular Imaging, 36(S1), 3-9. doi:10.1007/s00259-008-0940-9Wehner, J., Weissler, B., Dueppenbecker, P. M., Gebhardt, P., Goldschmidt, B., Schug, D., … Schulz, V. (2015). MR-compatibility assessment of the first preclinical PET-MRI insert equipped with digital silicon photomultipliers. Physics in Medicine and Biology, 60(6), 2231-2255. doi:10.1088/0031-9155/60/6/2231Wehrl, H. F., Judenhofer, M. S., Thielscher, A., Martirosian, P., Schick, F., & Pichler, B. J. (2010). Assessment of MR compatibility of a PET insert developed for simultaneous multiparametric PET/MR imaging on an animal system operating at 7 T. Magnetic Resonance in Medicine, 65(1), 269-279. doi:10.1002/mrm.22591Yamamoto, S., Imaizumi, M., Kanai, Y., Tatsumi, M., Aoki, M., Sugiyama, E., … Hatazawa, J. (2010). Design and performance from an integrated PET/MRI system for small animals. Annals of Nuclear Medicine, 24(2), 89-98. doi:10.1007/s12149-009-0333-6Yamamoto, S., Watabe, T., Watabe, H., Aoki, M., Sugiyama, E., Imaizumi, M., … Hatazawa, J. (2011). Simultaneous imaging using Si-PM-based PET and MRI for development of an integrated PET/MRI system. Physics in Medicine and Biology, 57(2), N1-N13. doi:10.1088/0031-9155/57/2/n1Zaidi, H., Montandon, M.-L., & Alavi, A. (2008). The Clinical Role of Fusion Imaging Using PET, CT, and MR Imaging. PET Clinics, 3(3), 275-291. doi:10.1016/j.cpet.2009.03.00

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Correction to: Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

The original version of this article unfortunately contained a mistake

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Characterization of preclinical PET insert for 7T: beyond NEMA testing.

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Acute changes in rat brain metabolism after intravenous administration of alcohol, cocaine, and nicotine: A simultaneous PET/MR study with dynamic 1HMRS and continuous infusion 18FDG.

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PolyGate: Benefits of a spatially resolved navigator for self-gating cardiac imaging in multiple rodents.

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MRI-based retrospective gating for PET reconstruction in rats: implementation and proof of principle study

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MRI-based retrospective gating for PET reconstruction in rats: implementation and proof of principle study

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Low-Dose Imaging in a New Preclinical Total-Body PET/CT Scanner

Ionizing radiation constitutes a health risk to imaging scientists and study animals. Both PET and CT produce ionizing radiation. CT doses in pre-clinical in vivo imaging typically range from 50 to 1,000 mGy and biological effects in mice at this dose range have been previously described. [18F]FDG body doses in mice have been estimated to be in the range of 100 mGy for [18F]FDG. Yearly, the average whole body doses due to handling of activity by PET technologists are reported to be 3-8 mSv. A preclinical PET/CT system is presented with design features which make it suitable for small animal low-dose imaging. The CT subsystem uses a X-source power that is optimized for small animal imaging. The system design incorporates a spatial beam shaper coupled with a highly sensitive flat-panel detector and very fast acquisition (<10 s) which allows for whole body scans with doses as low as 3 mGy. The mouse total-body PET subsystem uses a detector architecture based on continuous crystals, coupled to SiPM arrays and a readout based in rows and columns. The PET field of view is 150 mm axial and 80 mm transaxial. The high solid-angle coverage of the sample and the use of continuous crystals achieve a sensitivity of 9% (NEMA) that can be leveraged for use of low tracer doses and/or performing rapid scans. The low-dose imaging capabilities of the total-body PET subsystem were tested with NEMA phantoms, in tumor models, a mouse bone metabolism scan and a rat heart dynamic scan. The CT imaging capabilities were tested in mice and in a low contrast phantom. The PET low-dose phantom and animal experiments provide evidence that image quality suitable for preclinical PET studies is achieved. Furthermore, CT image contrast using low dose scan settings was suitable as a reference for PET scans. Total-body mouse PET/CT studies could be completed with total doses of <10 mGy.status: publishe