NEMA characterization of the SAFIR prototype PET insert

Khateri, Parisa; Lustermann, W.; Ritzer, Christian; Tsoumpas, Charalampos; Dissertori, G.

doi:10.1186/s40658-022-00454-2

“…The performance reports for each test were again based on the protocol’s instruction. Finally, the achieved performance results were compared to the performance parameters reported for a set of reference scanners featuring similarly sized crystals, including the SAFIR prototype system, as tabulated in [ 3 ].…”

Section: Methodsmentioning

confidence: 99%

“…As a back-projection filter the STIR-default Colsher filter ( , cut-off 0.5 cycles in both axial and planar directions) was used. A known downside of this algorithm is its requirement for cylindrical projection data; for a detector with block geometry like SAFIR-I, direct interpolation of the data to fit the cylindrical geometry leads to image degradation with severe streak artifacts [ 3 , 5 , 11 , 12 ]. In order to partially ameliorate the degradation, the raw data from SAFIR-I were first sorted into projection data using its true, generic block geometry and then rebinned into a cylindrical projection [ 5 , 11 , cf.…”

Section: Methodsmentioning

confidence: 99%

“…The inserts are specified to enable quantitative, truly simultaneous PET/MRI research in mice and rats, with a spatial resolution of around in the center of the Field Of View (FOV), at injected activities extending up to . Exploitation of the associated high count rates, specifically the corresponding low noise, enables an exceptional image frame acquisition speed in the order of one diagnostically relevant frame every few seconds [ 1 , 3 , cf.]. This high frame rate is required for capturing fast tracer kinetics, which was not possible with existing small-animal PET systems [ 1 , cf.].…”

Section: Introductionmentioning

confidence: 99%

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SAFIR-I: first NEMA NU 4-2008-based performance characterization

Bebié,

Lustermann,

Debus

et al. 2023

EJNMMI Phys

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Background Small Animal Fast Insert for MRI detector I (SAFIR-I) is a novel Positron Emission Tomography insert for a $$7\,\hbox {T}$$ 7 T Bruker BioSpec 70/30 Ultra Shield Refrigerated Magnetic Resonance Imaging (MRI) system. It facilitates truly simultaneous quantitative imaging in mice and rats at injected activities as high as $$500\,\hbox {MBq}$$ 500 MBq . Exploitation of the resulting high count rates enables quick image formation at few seconds per frame. In this investigation, key performance parameters of SAFIR-I have been determined according to the evaluations outlined in the National Electrical Manufacturers Association (NEMA) Standards Publication NU 4-2008 (NEMA-NU4) protocol. Results Using an energy window of 391 to $$601\,\hbox {keV}$$ 601 keV and a Coincidence Timing Window of $$500\,\hbox {ps}$$ 500 ps , the following performance was observed: The average spatial resolution at $$5\,\hbox {mm}$$ 5 mm radial offset (Full Width at Half Maximum) is $$2.54\,\hbox {mm}$$ 2.54 mm when using Filtered Backprojection, 3D Reprojection reconstruction. For the mouse- and rat-like phantoms, the maximal Noise-Equivalent Count Rates (NECRs) are $$1368\,\hbox {kcps}$$ 1368 kcps at the highest tested average effective concentration of $$14.7\,\hbox {MBq}\,\hbox {cc}^{-1}$$ 14.7 MBq cc - 1 , and $$713\,\hbox {kcps}$$ 713 kcps at the highest tested average effective concentration of $$1.72\,\hbox {MBq}\,\hbox {cc}^{-1}$$ 1.72 MBq cc - 1 , respectively. The NECR peak is not yet reached for either of these cases. The peak sensitivity is $$1.46\,\%$$ 1.46 % . The Image Quality phantom uniformity standard deviation is $$4.8\,\%$$ 4.8 % . The Recovery Coefficient for the $$5\,\hbox {mm}$$ 5 mm rod is $$(1.08 \pm 0.10)$$ ( 1.08 ± 0.10 ) . The Spill-Over Ratios are $$(0.22 \pm 0.03)$$ ( 0.22 ± 0.03 ) and $$(0.22 \pm 0.02)$$ ( 0.22 ± 0.02 ) , for the water- and air-filled cylinder, respectively. An accuracy of $$4.3\,\%$$ 4.3 % was achieved for the quantitative calibration of reconstructed voxel values. Conclusions The measured performance parameters indicate that the various design goals have been achieved. SAFIR-I offers excellent performance, especially at the high activities it was designed for. This facilitates planned experiments with fast tracer kinetics in small animals. Ways to potentially improve performance can still be explored. Simultaneously, further performance gains can be expected for a forthcoming insert featuring 2.7 times longer axial coverage named Small Animal Fast Insert for MRI detector II (SAFIR-II).

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“…The multiple cells can provide a proportional signal to the input light by summing all the activated cells. Currently, SiPMs have displaced PMTs in most of the modern TOF-PET systems [46][47][48][49][50][51] and combined PET/MR scanners [52][53][54][55][56]. However, there is still space for other MR-compatible photosensors, such as APDs [57,58], being an active research field.…”

Section: Nai (Tlmentioning

confidence: 99%

Recent advances in combined Positron Emission Tomography and Magnetic Resonance Imaging

Galve,

Rodriguez-Vila,

Herraiz

et al. 2024

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Hybrid imaging modalities combine two or more medical imaging techniques offering exciting new possibilities to image the structure, function and biochemistry of the human body in far greater detail than has previously been possible to improve patient diagnosis. In this context, simultaneous Positron Emission Tomography and Magnetic Resonance (PET/MR) imaging offers great complementary information, but it also poses challenges from the point of view of hardware and software compatibility. The PET signal may interfere with the MR magnetic field and vice-versa, posing several challenges and constrains in the PET instrumentation for PET/MR systems. Additionally, anatomical maps are needed to properly apply attenuation and scatter corrections to the resulting reconstructed PET images, as well motion estimates to minimize the effects of movement throughout the acquisition. In this review, we summarize the instrumentation implemented in modern PET scanners to overcome these limitations, describing the historical development of hybrid PET/MR scanners. We pay special attention to the methods used in PET to achieve attenuation, scatter and motion correction when it is combined with MR, and how both imaging modalities may be combined in PET image reconstruction algorithms.

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“…In addition to the FBP which is required for NEMA, point sources are often additionally reconstructed with an iterative method (Liang et al 2020, Khateri et al 2022). This originates from the well known degradation of the spatial resolution by FBP for systems with gaps in the detector ring (Hallen et al 2020).…”

Section: Spatial Resolutionmentioning

confidence: 99%

Setup and characterisation according to NEMA NU 4 of the phenoPET scanner, a PET system dedicated for plant sciences

Hinz,

Jahnke,

Metzner

et al. 2024

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The phenoPET system is a plant dedicated Positron Emission Tomography (PET) scanner consisting of fully digital photo multipliers with lutetium-yttrium oxyorthosilicate crystals and located inside a custom climate chamber. Here, we present the setup of phenoPET, its data processing and image reconstruction together with the performance according to the NEMA standard for small animal PET systems. The spatial resolution for a 22Na point source at a radial distance of 5mm to the center of the Field-of-View (FOV) is 1.45mm, 0.82mm and 1.88mm with Filtered Back Projection in radial, tangential and axial direction, respectively. A hot rod phantom with 18F gives a spatial resolution of up to 1.6mm. The peak noise-equivalent count rates are 550kcps@35.08MBq, 308kcps@33MBq and 45kcps@40.60MBq for the mouse, rat and monkey size scatter phantoms, respectively. The scatter fractions for these phantoms are 12.63%, 22.64% and 55.90%. We observe a peak sensitivity of up to 3.6% and a total sensitivity of up to SA,tot=2.17%. For the NEMA image quality phantom we observe a uniformity of %STD=4.22% with Ordinary Poisson Maximum Likelihood Expectation-Maximization with 52 iterations. Here, recovery coefficients of 0.12, 0.64, 0.89, 0.93 and 0.91 for 1mm, 2mm, 3mm, 4mm and 5mm rods are obtained and spill-over ratios of 0.08 and 0.14 for the water-filled and air-filled inserts, respectively. The phenoPET and its laboratory are now in routine operation for the administration of [11C]CO2 and non-invasive measurement of transport and allocation of 11C-labelled photoassimilates in plants.

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NEMA characterization of the SAFIR prototype PET insert

Cited by 5 publications

References 34 publications

SAFIR-I: first NEMA NU 4-2008-based performance characterization

SAFIR-I: first NEMA NU 4-2008-based performance characterization

Recent advances in combined Positron Emission Tomography and Magnetic Resonance Imaging

Setup and characterisation according to NEMA NU 4 of the phenoPET scanner, a PET system dedicated for plant sciences

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