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The neuronal tricarboxylic acid and glutamate/glutamine (Glu/Gln) cycles play important roles in brain function. These processes can be measured in vivo using dynamic 1H–[13C] MRS during administration of 13C‐labeled glucose. Proton‐observed carbon‐edited (POCE) MRS enhances the signal‐to‐noise ratio (SNR) compared with direct 13C‐MRS. Ultra‐high field further boosts the SNR and increases spectral dispersion; however, even at 7 T, Glu and Gln 1H‐resonances may overlap. Further gain can be obtained with selective POCE (selPOCE). Our aim was to create a setup for indirect dynamic 1H–[13C] MRS in the human brain at 7 T. A home‐built non‐shielded transmit–receive 13C‐birdcage head coil with eight transmit–receive 1H‐dipole antennas was used together with a 32‐channel 1H‐receive array. Electromagnetic simulations were carried out to ensure that acquisitions remained within local and global head SAR limits. POCE‐MRS was performed using slice‐selective excitation with semi‐localization by adiabatic selective refocusing (sLASER) and stimulated echo acquisition mode (STEAM) localization, and selPOCE‐MRS using STEAM. Sequences were tested in a phantom containing non‐enriched Glu and Gln, and in three healthy volunteers during uniformly labeled 13C‐glucose infusions. In one subject the voxel position was alternated between bi‐frontal and bi‐occipital placement within one session. [4‐13C]Glu‐H4 and [4‐13C]Gln‐H4 signals could be separately detected using both STEAM‐POCE and STEAM‐selPOCE in the phantom. In vivo, [4,5‐13C]Glx could be detected using both sLASER‐POCE and STEAM‐POCE, with similar sensitivities, but [4,5‐13C]Glu and [4,5‐13C]Gln signals could not be completely resolved. STEAM‐POCE was alternately performed bi‐frontal and bi‐occipital within a single session without repositioning of the subject, yielding similar results. With STEAM‐selPOCE, [4,5‐13C]Glu and [4,5‐13C]Gln could be clearly separated. We have shown that with our setup indirect dynamic 1H–[13C] MRS at 7 T is feasible in different locations in the brain within one session, and by using STEAM‐selPOCE it is possible to separate Glu from Gln in vivo while obtaining high quality spectra. [ABSTRACT FROM AUTHOR]

Background: Magnetic Resonance Spin TomogrAphy in Time‐domain (MR‐STAT) can reconstruct whole‐brain multi‐parametric quantitative maps (eg, T1, T2) from a 5‐minute MR acquisition. These quantitative maps can be leveraged for synthetization of clinical image contrasts. Purpose: The objective was to assess image quality and overall diagnostic accuracy of synthetic MR‐STAT contrasts compared to conventional contrast‐weighted images. Study Type: Prospective cross‐sectional clinical trial. Population: Fifty participants with a median age of 45 years (range: 21–79 years) consisting of 10 healthy participants and 40 patients with neurological diseases (brain tumor, epilepsy, multiple sclerosis or stroke). Field Strength/Sequence: 3T/Conventional contrast‐weighted imaging (T1/T2 weighted, proton density [PD] weighted, and fluid‐attenuated inversion recovery [FLAIR]) and a MR‐STAT acquisition (2D Cartesian spoiled gradient echo with varying flip angle preceded by a non‐selective inversion pulse). Assessment: Quantitative T1, T2, and PD maps were computed from the MR‐STAT acquisition, from which synthetic contrasts were generated. Three neuroradiologists blinded for image type and disease randomly and independently evaluated synthetic and conventional datasets for image quality and diagnostic accuracy, which was assessed by comparison with the clinically confirmed diagnosis. Statistical Tests: Image quality and consequent acceptability for diagnostic use was assessed with a McNemar's test (one‐sided α = 0.025). Wilcoxon signed rank test with a one‐sided α = 0.025 and a margin of Δ = 0.5 on the 5‐level Likert scale was used to assess non‐inferiority. Results: All data sets were similar in acceptability for diagnostic use (≥3 Likert‐scale) between techniques (T1w:P = 0.105, PDw:P = 1.000, FLAIR:P = 0.564). However, only the synthetic MR‐STAT T2 weighted images were significantly non‐inferior to their conventional counterpart; all other synthetic datasets were inferior (T1w:P = 0.260, PDw:P = 1.000, FLAIR:P = 1.000). Moreover, true positive/negative rates were similar between techniques (conventional: 88%, MR‐STAT: 84%). Data Conclusion: MR‐STAT is a quantitative technique that may provide radiologists with clinically useful synthetic contrast images within substantially reduced scan time. Evidence Level: 1 Technical Efficacy: Stage 2 [ABSTRACT FROM AUTHOR]

Purpose: CXCR4 (over)expression is found in multiple human cancer types, while expression is low or absent in healthy tissue. In glioblastoma it is associated with a poor prognosis and more extensive infiltrative phenotype. CXCR4 can be targeted by the diagnostic PET agent [68Ga]Ga-Pentixafor and its therapeutic counterpart [177Lu]Lu-Pentixather. We aimed to investigate the expression of CXCR4 in glioblastoma tissue to further examine the potential of these PET agents. Methods: CXCR4 mRNA expression was examined using the R2 genomics platform. Glioblastoma tissue cores were stained for CXCR4. CXCR4 staining in tumor cells was scored. Stained tissue components (cytoplasm and/or nuclei of the tumor cells and blood vessels) were documented. Clinical characteristics and information on IDH and MGMT promoter methylation status were collected. Seven pilot patients with recurrent glioblastoma underwent [68Ga]Ga-Pentixafor PET; residual resected tissue was stained for CXCR4. Results: Two large mRNA datasets (N = 284; N = 540) were assesed. Of the 191 glioblastomas, 426 cores were analyzed using immunohistochemistry. Seventy-eight cores (23 tumors) were CXCR4 negative, while 18 cores (5 tumors) had both strong and extensive staining. The remaining 330 cores (163 tumors) showed a large inter- and intra-tumor variation for CXCR4 expression; also seen in the resected tissue of the seven pilot patients—not directly translatable to [68Ga]Ga-Pentixafor PET results. Both mRNA and immunohistochemical analysis showed CXCR4 negative normal brain tissue and no significant correlation between CXCR4 expression and IDH or MGMT status or survival. Conclusion: Using immunohistochemistry, high CXCR4 expression was found in a subset of glioblastomas as well as a large inter- and intra-tumor variation. Caution should be exercised in directly translating ex vivo CXCR4 expression to PET agent uptake. However, when high CXCR4 expression can be identified with [68Ga]Ga-Pentixafor, these patients might be good candidates for targeted radionuclide therapy with [177Lu]Lu-Pentixather in the future. [ABSTRACT FROM AUTHOR]

The neuronal tricarboxylic acid and glutamate/glutamine (Glu/Gln) cycles play important roles in brain function. These processes can be measured in vivo using dynamic 1 H-[ 13 C] MRS during administration of 13 C-labeled glucose. Proton-observed carbon-edited (POCE) MRS enhances the signal-to-noise ratio (SNR) compared with direct 13 C-MRS. Ultra-high field further boosts the SNR and increases spectral dispersion; however, even at 7 T, Glu and Gln 1 H-resonances may overlap. Further gain can be obtained with selective POCE (selPOCE). Our aim was to create a setup for indirect dynamic 1 H-[ 13 C] MRS in the human brain at 7 T. A home-built non-shielded transmit-receive 13 C-birdcage head coil with eight transmit-receive 1 H-dipole antennas was used together with a 32-channel 1 H-receive array. Electromagnetic simulations were carried out to ensure that acquisitions remained within local and global head SAR limits. POCE-MRS was performed using slice-selective excitation with semi-localization by adiabatic selective refocusing (sLASER) and stimulated echo acquisition mode (STEAM) localization, and selPOCE-MRS using STEAM. Sequences were tested in a phantom containing non-enriched Glu and Gln, and in three healthy volunteers during uniformly labeled 13 C-glucose infusions. In one subject the voxel position was alternated between bi-frontal and bi-occipital placement within one session. [4- 13 C]Glu-H4 and [4- 13 C]Gln-H4 signals could be separately detected using both STEAM-POCE and STEAM-selPOCE in the phantom. In vivo, [4,5- 13 C]Glx could be detected using both sLASER-POCE and STEAM-POCE, with similar sensitivities, but [4,5- 13 C]Glu and [4,5- 13 C]Gln signals could not be completely resolved. STEAM-POCE was alternately performed bi-frontal and bi-occipital within a single session without repositioning of the subject, yielding similar results. With STEAM-selPOCE, [4,5- 13 C]Glu and [4,5- 13 C]Gln could be clearly separated. We have shown that with our setup indirect dynamic 1 H-[ 13 C] MRS at 7 T is feasible in different locations in the brain within one session, and by using STEAM-selPOCE it is possible to separate Glu from Gln in vivo while obtaining high quality spectra., (© 2024 The Author(s). NMR in Biomedicine published by John Wiley & Sons Ltd.)

Purpose: This study evaluates the radiographic appearance of lacrimal gland tissue after placement of a glaucoma drainage implant (GDI) to characterize the impact of the device on the gland's imaging patterns., Methods: We performed retrospective chart review of departmental records at two urban academic medical centers, which were systematically searched using procedure codes to identify adult glaucoma patients who underwent unilateral superotemporal GDI from January 1995 to December 2015. Radiology records were cross-checked to identify the subset of patients who underwent postoperative orbital CT or MRI. Chart review collected data on glaucoma diagnosis, management, examination findings, and clinical complaints. Imaging studies were reviewed for orbital changes using qualitative assessment of the radiographic appearances and computer-guided calculations to quantify asymmetries., Results: A review of all eye operations in the inclusion period identified 315 patients with GDI, 13 of whom were eligible for inclusion. Elapsed time from device placement to imaging averaged 41.9 months, and the average clinical follow-up was 56.4 months. Radiographic lacrimal gland changes were appreciable in 69% (9 of 13) of patients, most commonly with posterior displacement and flattening of the gland (7 of 13). ImageJ analysis revealed significantly smaller lacrimal glands in orbits with GDI ( P = 0.04). No clear correlation was found between gland changes and clinical dry eye symptoms., Conclusion: GDI placement was associated with radiographically-appreciable lacrimal gland changes in two-thirds of patients, with changes occurring in a predictable pattern of lacrimal gland flattening, posteriorization, and volume loss. Radiographic changes correlated with clinical symptoms in few patients., Competing Interests: There are no conflicts of interest.