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Purpose: In vivo1H and 31P magnetic resonance spectroscopic imaging (MRSI) provide complementary information on the biology of prostate cancer. In this work we demonstrate the feasibility of performing multiparametric imaging (mpMRI) and 1H and 31P spectroscopic imaging of the prostate using a 31P and 1H endorectal radiofrequency coil (ERC) in combination with a multitransmit body array at 7 Tesla (T). Methods: An ERC with a 31P transceiver loop coil and 1H receive (Rx) asymmetric microstrip (31P/1H ERC) was designed, constructed and tested in combination with an external 8‐channel 1H transceiver body array coil (8CH). Electromagnetic field simulations and measurements and in vivo temperature measurements of the ERC were performed for safety validation. In addition, the signal‐to‐noise (SNR) benefit of the 1H microstrip with respect to the 8CH was evaluated. Finally, the feasibility of the setup was tested in one volunteer and three patients with prostate cancer by performing T2‐weighted and diffusion‐weighted imaging in combination with 1H and 31P spectroscopic imaging. Results: Electromagnetic field simulations of the 31P loop coil showed no differences in the E‐ and B‐fields of the 31P/1H ERC compared with a previously safety validated ERC without 1H microstrip. The hotspot of the specific absorption rate (SAR) at the feed point of the 31P/1H ERC loop coil was 9.42 W/kg when transmitting on 31P at 1 W. Additional in vivo measurements showed a maximum temperature increase at the SAR hotspot of 0.7°C over 6 min on 31P at 1.9 W transmit (Tx) power, indicating safe maximum power levels. When transmitting with the external 1H body array at 40W for 2:30 min, the temperature increase around the ERC was < 0.3°C. Up to 3.5 cm into the prostate the 1H microstrip of the ERC provided higher SNR than the 8CH. The total coil combination allowed acquisition of an mpMRI protocol and the assessment of 31P and 1H metabolites of the prostate in all test subjects. Conclusion: We developed a setup with a 31P transceiver and 1H Rx endorectal coil in combination with an 8‐channel transceiver external body array coil and demonstrated its safety and feasibility for obtaining multiparametric imaging and 1H and 31P MRSI at 7T in patients with prostate cancer within one MR examination. [ABSTRACT FROM AUTHOR]

Purpose: To design and evaluate an 8/15‐channel transmit/receive (Tx/Rx) head‐neck RF coil combination with region‐specific B 1 + shimming for whole‐brain MRI with focus on improved functional MRI of the cerebellum at 7 T. Methods: An 8‐channel transceiver RF head coil was combined with a 7‐channel receive‐only array. The noise parameters and acceleration capabilities of this 8Tx/15Rx coil setup were compared with a commercially available 1Tx/32Rx RF head coil. Region‐specific 8‐channel B 1 + shimming was applied when using the 8Tx/15Rx RF coil. To evaluate the capability for functional MRI of the cerebellum, temporal SNR and statistical nonparametric maps for finger‐tapping experiments with 14 healthy subjects were derived by applying a variable slice thickness gradient‐echo echo‐planar functional MRI sequence. Results: The 8Tx/15Rx setup had a lower maximum noise correlation between channels, but higher average correlations compared with the 1Tx/32Rx coil. Both RF coils exhibited identical g‐factors in the cerebellum with R = 3 acceleration. The enlarged FOV of the 8Tx/15Rx coil in combination with region‐specific B 1 + shimming increased homogeneity of the transmission field and temporal SNR in caudal cerebellar regions. Temporal SNR losses in cranial parts were reduced, resulting in more highly significant voxels in the caudally activated areas and identical patterns in the cranial cerebellar parts during a finger‐tapping task. Conclusion: Compared with the 1Tx/32Rx RF coil, the presented 8Tx/15Rx RF coil combination successfully improves functional MRI of the human cerebellum at 7 T while maintaining whole‐brain coverage. A clear temporal SNR gain in caudal cerebellar regions is shown. [ABSTRACT FROM AUTHOR]

Purpose: Current methods for mitigation of transmit field B 1 + inhomogeneities at ultrahigh field (UHF) MRI by multi‐channel radiofrequency (RF) shimming rely on accurate B 1 + mapping. This can be time consuming when many RF channels have to be mapped for in vivo body MRI, where the B1 maps should ideally be acquired within a single breath‐hold. Therefore, a new B 1 + mapping technique (B1TIAMO) is proposed. Methods: The performance of this technique is validated against an established method (DREAM) in phantom measurements for a cylindrical head phantom with an 8‐channel transmit/receive (Tx/Rx) array. Furthermore, measurements for a 32‐channel Tx/Rx remote array are conducted in a large body phantom and the | B 1 + | map reliability is validated against simulations of the transmit RF field distribution. Finally, in vivo results of this new mapping technique for human abdomen are presented. Results: For the head phantom (8‐channel Tx/Rx coil), the single | B 1 + | comparison between B1TIAMO, the direct DREAM measurements, and simulation data showed good agreement with 10–19% difference. For the large body phantom (32‐channel Tx/Rx coil), B1TIAMO matched the RF field simulations well. Conclusion: The results demonstrate the potential to acquire 32 accurate single‐channel B 1 + maps for large field‐of‐view body imaging within only a single breath‐hold of 16 s at 7T UHF MRI. Magn Reson Med 79:2652–2664, 2018. © 2017 International Society for Magnetic Resonance in Medicine. [ABSTRACT FROM AUTHOR]

Purpose To assess the feasibility of prostate 1H MR spectroscopic imaging (MRSI) using low-power spectral-spatial (SPSP) pulses at 7T, exploiting accurate spectral selection and spatial selectivity simultaneously. Methods A double spin-echo sequence was equipped with SPSP refocusing pulses with a spectral selectivity of 1 ppm. Three-dimensional prostate 1H-MRSI at 7T was performed with the SPSP-MRSI sequence using an 8-channel transmit array coil and an endorectal receive coil in three patients with prostate cancer and in one healthy subject. No additional water or lipid suppression pulses were used. Results Prostate 1H-MRSI could be obtained well within specific absorption rate (SAR) limits in a clinically feasible time (10 min). Next to the common citrate signals, the prostate spectra exhibited high spermine signals concealing creatine and sometimes also choline. Residual lipid signals were observed at the edges of the prostate because of limitations in spectral and spatial selectivity. Conclusion It is possible to perform prostate 1H-MRSI at 7T with a SPSP-MRSI sequence while using separate transmit and receive coils. This low-SAR MRSI concept provides the opportunity to increase spatial resolution of MRSI within reasonable scan times. Magn Reson Med 75:933-945, 2016. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]