TH‐D‐201C‐05: Monitoring Response of Liver Cancer to Targeted Radiation Therapy with a Novel 31P/1H MRS Coil

Abstract

Purpose: To present a novel multi‐channel dual‐tuned 31P/1H MRS coil which allows for non‐invasive acquisition of in‐vivo phosphorus (31P) spectroscopy data from the whole liver. We hypothesize MRS data collected with this coil can improve the assessment of early tumor response to targeted radiation therapy. Method and Materials: A novel dual‐tuned 8‐channel 31P/1H coil for a Siemens 3T Tim Trio whole Body MRI scanner was designed and validated. The coil consists of two plates placed anterior and posterior of the patient's torso with four 31P receive elements (24×20 cm2) each. Furthermore each plate has one 31P transmit element and one 1H transmit‐receive element. Thus the coil allows for 31P MRS conventional MRI and 1H MRS during the same scan session. For our clinical study the 31P MRS data was acquired with a 2D slice selective free‐induction‐decay (FID) sequence using the following parameters: TE 2.3 ms TR 1 s field of view (FOV) 400×400×30 mm3 nominal voxel size 25×25×30 mm3 30 weighted averages. Each free‐induction‐decay (FID) was acquired with 2048 points over a bandwidth of 5000 Hz. The resulting scan time was about 25 min. Results: In vivo 31P liver spectra and 1H MRI images of the entire liver were successfully acquired in healthy volunteers and patients undergoing targeted radiation therapy. The optimized 31P MRS sequence allowed for identification and quantification of ATP phosphomonoesters (PME) phosphodiesters (PDE) and inorganic phosphate (Pi) metabolites throughout the liver on an axial slice. Metabolic differences between healthy and malignant liver tissue were clearly identified. Conclusions: We have shown that our novel 31P/1H MRS coil allows for assessing 31P metabolites in lesions located in deep tissue while being able to run conventional MRI imaging scans during the same scan session.