The Jülich Experience With Simultaneous 3T MR-BrainPET: Methods and Technology

Caldeira, Liliana; Kops, Elena Rota; Yun, Seong Dae; Silva, Nuno da; Mauler, Jörg; Weirich, Christoph; Scheins, J.; Herzog, Hans; Tellmann, Lutz; Lohmann, Philipp; Langen, Karl‐Josef; Lerche, Christoph; Shah, N. Jon

doi:10.1109/trpms.2018.2863953

Cited by 18 publications

(41 citation statements)

References 58 publications

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“…All patients underwent a dynamic FET PET scan from 0 to 40 min post-injection of 3 MBq of FET per kg body weight. All patients were measured on a stand-alone PET scanner (ECAT EXACT HR+, Siemens Medical Systems, Inc., Erlangen, Germany) in 3D mode (32 rings, axial field of view, 15.5 cm; spatial resolution, 5 mm full-width at half maximum) [ 55 ]. The reconstructed dynamic dataset consisted of 14 time frames (5 × 1 min; 5 × 3 min; 4 × 5 min) with a reconstructed voxel size of 2.0 × 2.0 × 2.4 mm 3 .…”

Section: Methodsmentioning

confidence: 99%

FET PET Radiomics for Differentiating Pseudoprogression from Early Tumor Progression in Glioma Patients Post-Chemoradiation

Lohmann

Elahmadawy

Gutsche

et al. 2020

Cancers

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Currently, a reliable diagnostic test for differentiating pseudoprogression from early tumor progression is lacking. We explored the potential of O-(2-[18F]fluoroethyl)-L-tyrosine (FET) positron emission tomography (PET) radiomics for this clinically important task. Thirty-four patients (isocitrate dehydrogenase (IDH)-wildtype glioblastoma, 94%) with progressive magnetic resonance imaging (MRI) changes according to the Response Assessment in Neuro-Oncology (RANO) criteria within the first 12 weeks after completing temozolomide chemoradiation underwent a dynamic FET PET scan. Static and dynamic FET PET parameters were calculated. For radiomics analysis, the number of datasets was increased to 102 using data augmentation. After randomly assigning patients to a training and test dataset, 944 features were calculated on unfiltered and filtered images. The number of features for model generation was limited to four to avoid data overfitting. Eighteen patients were diagnosed with early tumor progression, and 16 patients had pseudoprogression. The FET PET radiomics model correctly diagnosed pseudoprogression in all test cohort patients (sensitivity, 100%; negative predictive value, 100%). In contrast, the diagnostic performance of the best FET PET parameter (TBRmax) was lower (sensitivity, 81%; negative predictive value, 80%). The results suggest that FET PET radiomics helps diagnose patients with pseudoprogression with a high diagnostic performance. Given the clinical significance, further studies are warranted.

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Section: Methodsmentioning

confidence: 99%

FET PET Radiomics for Differentiating Pseudoprogression from Early Tumor Progression in Glioma Patients Post-Chemoradiation

Lohmann

Elahmadawy

Gutsche

et al. 2020

Cancers

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“…However, in our case, the mean bias values were positive for both regions. Note that the differences of around 2% are probably due to our higher PET sensitivity of 6% [ 36 ], compared to 3% of the HRRT system [ 37 ]. In addition, based on data obtained from the fit analysis (slope changes), we also observed a negative bias for high activity concentration regions when the frame length was shortened (low counts).…”

Section: Discussionmentioning

confidence: 99%

Bias evaluation and reduction in 3D OP-OSEM reconstruction in dynamic equilibrium PET studies with 11C-labeled for binding potential analysis

et al. 2021

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Iterative image reconstruction is widely used in positron emission tomography. However, it is known to contribute to quantitation bias and is particularly pronounced during dynamic studies with 11C-labeled radiotracers where count rates become low towards the end of the acquisition. As the strength of the quantitation bias depends on the counts in the reconstructed frame, it can differ from frame to frame of the acquisition. This is especially relevant in the case of neuro-receptor studies with simultaneous PET/MR when a bolus-infusion protocol is applied to allow the comparison of pre- and post-task effects. Here, count dependent changes in quantitation bias may interfere with task changes. We evaluated the impact of different framing schemes on quantitation bias and its propagation into binding potential (BP) using a phantom decay study with 11C and 3D OP-OSEM. Further, we propose a framing scheme that keeps the true counts per frame constant over the acquisition time as constant framing schemes and conventional increasing framing schemes are unlikely to achieve stable bias values during the acquisition time range. For a constant framing scheme with 5 minutes frames, the BP bias was 7.13±2.01% (10.8% to 3.8%) compared to 5.63±2.85% (7.8% to 4.0%) for conventional increasing framing schemes. Using the proposed constant true counts framing scheme, a stabilization of the BP bias was achieved at 2.56±3.92% (3.5% to 1.7%). The change in BP bias was further studied by evaluating the linear slope during the acquisition time interval. The lowest slope values were observed in the constant true counts framing scheme. The constant true counts framing scheme was effective for BP bias stabilization at relevant activity and time ranges. The mean BP bias under these conditions was 2.56±3.92%, which represents the lower limit for the detection of changes in BP during equilibrium and is especially important in the case of cognitive tasks where the expected changes are low.

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“…Simultaneous image acquisition from positron emission tomography/magnetic resonance imaging (PET/MRI) has attracted researchers' attention for more than two decades owing to its specific advantages, such as providing spatial and temporal correlation of functional and morphological data, as well as allowing kinetic study of tissues' functional behaviors. [1][2][3][4][5] Compared to dual-modality PET/computed tomography (PET/CT) scanners, simultaneous PET/MRI scanner provides biological and anatomical data without additional radiation dose. 6,7 However, realizing a practical simultaneous PET/MRI scanner requires redesigning the front-end electronics of the PET scanner prior to its insertion in an MRI bore to ensure low electromagnetic interferences (EMI) between the two modalities.…”

Section: Introductionmentioning

confidence: 99%

“…Simultaneous image acquisition from positron emission tomography/magnetic resonance imaging (PET/MRI) has attracted researchers’ attention for more than two decades owing to its specific advantages, such as providing spatial and temporal correlation of functional and morphological data, as well as allowing kinetic study of tissues’ functional behaviors 1–5 . Compared to dual‐modality PET/computed tomography (PET/CT) scanners, simultaneous PET/MRI scanner provides biological and anatomical data without additional radiation dose 6,7 .…”

Section: Introductionmentioning

confidence: 99%

MRI‐compatibility study of a PET‐insert based on a low‐profile detection front‐end with submillimeter spatial resolution

et al. 2020

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The LabPET II detection module is a potential candidate to create an magnetic resonance imaging (MRI) compatible positron emission tomography (PET)-insert with submillimeter spatial resolution for small animal applications. However, the feasibility of such an insert is hampered by the large radial size of the LabPET II front-end electronics and by components containing ferromagnetic materials. In this paper, a new low-profile front-end design based on the LabPET II architecture, called "low-profile detection module," is investigated. Materials and methods: The performance of the low-profile detection module in the presence of MRI-like RF signals and gradient coil pulses was independently examined. The baseline of the analog signal, its RMS noise level, and the energy resolution, determined by a dual time-over-threshold (dTOT) method for each pixel of the new low-profile detection module, was measured in the presence of RF signals at different frequencies equivalent to the Larmor frequency of 3, 7, and 9.4 T MRI. The same parameters were investigated in the presence of a gradient coil switching at frequencies from 10 to 100 kHz. The performance of the low-profile detection module inside a 7 T MRI and its effects on an MR image have also been studied using gradient echo sequences. The same measurements were repeated for the shielded low-profile detection module, inside and outside the MRI. Results: Our results show that pulses in both the kilohertz and megahertz ranges cause up to 50% increase in the noise level of the baseline (DC analog signal at the output of the shaper filter) and up to 17% degradation in TOT energy resolution. By inserting a conducting composite layer as shielding around the low-profile detection module, these degrading effects were avoided. The performance measurement of the low-profile PET detection module inside a 7 T small animal MRI scanner confirmed that the shielded low-profile detection module behavior was similar inside and outside the MRI bore. In addition, gradient echo images of a water-filled phantom without and with the shielded and unshielded low-profile detection modules were acquired. The results demonstrated no evidence of artifacts in the MR image, either due to eddy currents or ferromagnetic materials with the shielded modules. Conclusion: A low-profile detection module based on the LabPET II technology was shown to be a viable candidate as a PET-insert for simultaneous PET/MRI applications considering its thin radial size and its EMI immunity due to placing it between two electronic boards. In comparison to the standard LabPET II detection module, it provides better performance in the presence of electromagnetic interferences, but a shielding layer is still required. When properly shielded, the proposed lowprofile detection module can be operated inside an MRI without degrading the PET count rate or the MRI performance.

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The Jülich Experience With Simultaneous 3T MR-BrainPET: Methods and Technology

Cited by 18 publications

References 58 publications

FET PET Radiomics for Differentiating Pseudoprogression from Early Tumor Progression in Glioma Patients Post-Chemoradiation

FET PET Radiomics for Differentiating Pseudoprogression from Early Tumor Progression in Glioma Patients Post-Chemoradiation

Bias evaluation and reduction in 3D OP-OSEM reconstruction in dynamic equilibrium PET studies with 11C-labeled for binding potential analysis

MRI‐compatibility study of a PET‐insert based on a low‐profile detection front‐end with submillimeter spatial resolution

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