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Purpose: To demonstrate the feasibility of using octafluorocyclobutane (OFCB, c‐C4F8) for T1 mapping of lungs in 19F MRI. Methods: The study was performed at 7 T in three healthy rats and three rats with pulmonary hypertension. To increase the sensitivity of 19F MRI, a bent‐shaped RF coil with periodic metal strips structure was used. The double flip angle method was used to calculate normalized transmitting RF field (B1n+) maps and for correcting T1 maps built with the variable flip angle (VFA) method. The ultrashort TE pulse sequence was applied for acquiring MR images throughout the study. Results: The dependencies of OFCB relaxation times on its partial pressure in mixtures with oxygen, air, helium, and argon were obtained. T1 of OFCB linearly depended on its partial pressure with the slope of about 0.35 ms/kPa in the case of free diffusion. RF field inhomogeneity leads to distortion of T1 maps built with the VFA method, and therefore to high standard deviation of T1 in these maps. To improve the accuracy of the T1 maps, the B1n+ maps were applied for VFA correction. This contributed to a 2–3‐fold decrease in the SD of T1 values in the corresponding maps compared with T1 maps calculated without the correction. Three‐dimensional T1 maps were obtained, and the mean T1 in healthy rat lungs was 35 ± 10 ms, and in rat lungs with pulmonary hypertension – 41 ± 9 ms. Conclusion: OFCB has a spin‐rotational relaxation mechanism and can be used for 19F T1 mapping of lungs. The calculated OFCB maps captured ventilation defects induced by edema. [ABSTRACT FROM AUTHOR]

Purpose: Development of a novel quadrature inductively driven transceive wireless coil for breast MRI at 1.5 T. Methods: A quadrature wireless coil (HHMM‐coil) design has been developed as a combination of two linearly polarized coils: a pair of 'metasolenoid' coils (MM‐coil) and a pair of Helmholtz‐type coils (HH‐coil). The MM‐coil consisted of an array of split‐loop resonators. The HH‐coil design included two electrically connected flat spirals. All the wireless coils were coupled to a whole‐body birdcage coil. The HHMM‐coil was studied and compared to the linear coils in terms of transmit and SAR efficiencies via numerical simulations. A prototype of HHMM‐coil was built and tested on a 1.5 T scanner in a phantom and healthy volunteer. We also proposed an extended design of the HHMM‐coil and compared its performance to a dedicated breast array. Results: Numerical simulations of the HHMM‐coil with a female voxel model have shown more than a 2.5‐fold increase in transmit efficiency and a 1.7‐fold enhancement of SAR efficiency compared to the linearly polarized coils. Phantom and in vivo imaging showed good agreement with the numerical simulations. Moreover, the HHMM‐coil provided good image quality, visualizing all areas of interest similar to a multichannel breast array with a 32% reduction in signal‐to‐noise ratio. Conclusion: The proposed quadrature HHMM‐coil allows the B1+$$ {\mathrm{B}}_1^{+} $$‐field to be significantly better focused in the region‐of‐interest compared to the linearly polarized coils. Thus, the HHMM‐coil provides high‐quality breast imaging on a 1.5 T scanner using a whole‐body birdcage coil for transmit and receive. [ABSTRACT FROM AUTHOR]