Feasibility of 31 P spectroscopic imaging at 7 T in lung carcinoma patients.

Abstract

Currently, it is difficult to predict effective therapy response to molecular therapies for the treatment of lung cancer based solely on anatomical images. 31P MR spectroscopic imaging could provide as a non‐invasive method to monitor potential biomarkers for early therapy evaluation, a necessity to improve personalized care and reduce cost. However, surface coils limit the imaging volume in conventional 31P MRSI. High‐energetic adiabatic RF pulses are required to achieve flip angle homogeneity but lead to high SAR. Birdcage coils permit use of conventional amplitude modulated pulses, even over large FOV, potentially decreasing overall SAR massively. Here, we investigate the feasibility of 3D 31P MRSI at 7 T in lung carcinoma patients using an integrated 31P birdcage body coil in combination with either a dual‐coil or a 16‐channel receiver.Simulations showed a maximum decrease in SNR per unit of time of 8% for flip angle deviations in short TR low flip‐angle excitation 3D CSI. The minimal SNR loss allowed for fast 3D CSI without time‐consuming calibration steps (>10:00 min.). 31P spectra from four lung carcinoma patients were acquired within 29:00 minutes and with high SNR using both receivers. The latter allowed discrimination of individual phosphodiesters, inorganic phosphate, phosphocreatine and ATP. The receiver array allowed for an increased FOV compared to the dual‐coil receiver.3D 31P‐CSI were acquired successfully in four lung carcinoma patients using the integrated 31P body coil at ultra‐high field. The increased spectral resolution at 7 T allowed differentiation of multiple 31P metabolites related to phospholipid and energy metabolism. Simulations provide motivation to exclude 31P B1 calibrations, potentially decreasing total scan duration. Employing large receiver arrays improves the field of view allowing for full organ coverage. 31P MRSI is feasible in lung carcinoma patients and has potential as a non‐invasive method for monitoring personalized therapy response in lung tumors.