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Purpose: To present the validation of a new Flexible Ultra‐Short Echo time (FUSE) pulse sequence using a short‐T2 phantom. Methods: FUSE was developed to include a range of RF excitation pulses, trajectories, dimensionalities, and long‐T2 suppression techniques, enabling real‐time interchangeability of acquisition parameters. Additionally, we developed an improved 3D deblurring algorithm to correct for off‐resonance artifacts. Several experiments were conducted to validate the efficacy of FUSE, by comparing different approaches for off‐resonance artifact correction, variations in RF pulse and trajectory combinations, and long‐T2 suppression techniques. All scans were performed on a 3 T system using an in‐house short‐T2 phantom. The evaluation of results included qualitative comparisons and quantitative assessments of the SNR and contrast‐to‐noise ratio. Results: Using the capabilities of FUSE, we demonstrated that we could combine a shorter readout duration with our improved deblurring algorithm to effectively reduce off‐resonance artifacts. Among the different RF and trajectory combinations, the spiral trajectory with the regular half‐inc pulse achieves the highest SNRs. The dual‐echo subtraction technique delivers better short‐T2 contrast and superior suppression of water and agar signals, whereas the off‐resonance saturation method successfully suppresses water and lipid signals simultaneously. Conclusion: In this work, we have validated the use of our new FUSE sequence using a short T2 phantom, demonstrating that multiple UTE acquisitions can be achieved within a single sequence. This new sequence may be useful for acquiring improved UTE images and the development of UTE imaging protocols. [ABSTRACT FROM AUTHOR]

Background: The positron emission tomography (PET) ligand 68Ga-Glu-urea-Lys(Ahx)-HBED-CC (68Ga-PSMA-11) targets the prostate-specific membrane antigen (PSMA), upregulated in prostate cancer cells. Although 68Ga-PSMA-11 PET is widely used in research and clinical practice, full kinetic modeling has not yet been reported nor have simplified methods for quantification been validated. The aims of our study were to quantify 68Ga-PSMA-11 uptake in primary prostate cancer patients using compartmental modeling with arterial blood sampling and to validate the use of standardized uptake values (SUV) and image-derived blood for quantification. Results: Fifteen patients with histologically proven primary prostate cancer underwent a 60-min dynamic 68Ga-PSMA-11 PET scan of the pelvis with axial T1 Dixon, T2, and diffusion-weighted magnetic resonance (MR) images acquired simultaneously. Time-activity curves were derived from volumes of interest in lesions, normal prostate, and muscle, and mean SUV calculated. In total, 18 positive lesions were identified on both PET and MR. Arterial blood activity was measured by automatic arterial blood sampling and manual blood samples were collected for plasma-to-blood ratio correction and for metabolite analysis. The analysis showed that 68Ga-PSMA-11 was stable in vivo. Based on the Akaike information criterion, 68Ga-PSMA-11 kinetics were best described by an irreversible two-tissue compartment model. The rate constants K1 and k3 and the net influx rate constants Ki were all significantly higher in lesions compared to normal tissue (p < 0.05). Ki derived using image-derived blood from an MR-guided method showed excellent agreement with Ki derived using arterial blood sampling (intraclass correlation coefficient = 0.99). SUV correlated significantly with Ki with the strongest correlation of scan time-window 30–45 min (rho 0.95, p < 0.001). Both Ki and SUV correlated significantly with serum prostate specific antigen (PSA) level and PSA density. Conclusions: 68Ga-PSMA-11 kinetics can be described by an irreversible two-tissue compartment model. An MR-guided method for image-derived blood provides a non-invasive alternative to blood sampling for kinetic modeling studies. SUV showed strong correlation with Ki and can be used in routine clinical settings to quantify 68Ga-PSMA-11 uptake. [ABSTRACT FROM AUTHOR]