Anshuman Panda MS, Presenter: Nothing to Disclose

Scott Ray Jones MS, Abstract Co-Author: Nothing to Disclose

Kumaresan Sandrasegaran MD, Abstract Co-Author: Research grant, Siemens AG Consultant, Repligen Corporation

Ulrike Dydak PhD, Abstract Co-Author: Nothing to Disclose

Stereotactic Body Radiation Therapy (SBRT) and Selective Internal Radiation Therapy (SIRT) with 90Y are two targeted radiotherapy options currently employed in the clinic for treatment of unresectable Hepatocellular Carcinoma (HCC). However, current clinical protocols used for response evaluation of these treatments, which are based on conventional imaging techniques, are inadequate. We have recently shown successful application of 31P MR Spectroscopy (MRS) as a non-invasive tool to evaluate metabolic changes in focal liver lesions. The objective of the proposed abstract is to share our experiences regarding the clinical efficacy of 31P MRS in evaluation of HCC treatment response to targeted radiation therapies.

A novel dual-tuned 8-channel 31P/1H coil was used on a Siemens 3T MRI scanner to acquire 31P MRS data from the liver in five patients treated with SIRT, and three patients treated with SBRT. Multiple pre- and post-treatment scans were acquired from these subjects to evaluate data reproducibility and treatment response. A 2D slice selective 31P spectroscopic imaging sequence was used with a spatial resolution of 25x25x30 mm3 and an acquisition time of about 25 min. Quantification of the 31P metabolites was achieved by spectral fitting of the MRS data with use of prior knowledge.

The attached figure shows changes in the phosphomonoesther (PME)/ phosphodiesther (PDE) ratio for healthy (blue voxels) and malignant liver tissue (red voxels) of a cancer patient pre and 1-month post SBRT treatment. The PME/PDE ratio in the red voxels dropped by 28% compared to a variation in healthy tissue of only 7%, suggesting a positive treatment response, which was confirmed six months later also by conventional RECIST monitoring criteria.

Our preliminary analysis shows that 31P MRS has the potential to predict early response. However, tumor location, tumor motion, patient size, and technical complexities in data acquisition remain significant challenges for clinical routine. Reduction in scan time, implementation of motion correction (e.g. gating), and robust quantification techniques which minimize variability in the data may help to make 31P MRS a more clinically robust technique.

We hypothesize that 31P MRS data collected from this novel coil would improve early tumor response monitoring for patients treated with targeted radiation therapy techniques.

Panda, A, Jones, S, Sandrasegaran, K, Dydak, U, Efficacy of ³¹P MRS in Evaluation of Hepatocellular Carcinoma Response to Targeted Radiation Therapy.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11006175.html