Advancement of 31P Magnetic Resonance Spectroscopy Using GRAPPA Reconstruction on a 3D Volume
The overall objective of this research is to improve currently available metabolic imaging techniques for clinical use in monitoring and predicting treatment response to radiation therapy in liver cancer. Liver metabolism correlates with inflammatory and neoplastic liver diseases, which alter the intracellular concentration of phosphorus- 31 (31P) metabolites . It is assumed that such metabolic changes occur prior to physical changes of the tissue. Therefore, information on regional changes of 31P metabolites in the liver, obtained by Magnetic Resonance Spectroscopic Imaging (MRSI) [1,2], can help in diagnosis and follow-up of various liver diseases. Specifically, there appears to be an immediate need of this technology for both the assessment of tumor response in patients with Hepatocellular Carcinoma (HCC) treated with Stereotactic Body Radiation Therapy (SBRT) [3–5], as well as assessment of radiation toxicity, which can result in worsening liver dysfunction . Pilot data from our lab has shown that 31P MRSI has the potential to identify treatment response five months sooner than conventional methods , and to assess the biological response of liver tissue to radiation 24 hours post radiation therapy . While this data is very promising, commonly occurring drawbacks for 31P MRSI are patient discomfort due to long scan times and prone positioning within the scanner, as well as reduced data quality due to patient motion and respiration. To further advance the full potential of 31P MRSI as a clinical diagnostic tool in the management of liver cancer, this PhD research project had the following aims: I) Reduce the long acquisition time of 3D 31P MRS by formulating and imple- menting an appropriate GRAPPA undersampling scheme and reconstruction on a clinical MRI scanner II) Testing and quantitative validation of GRAPPA reconstruction on 3D 31P MRSI on developmental phantoms and healthy volunteers At completion, this work should considerably advance 31P MRSI as a clinical diagnos- tic tool for liver cancer, and potentially other cancer types, by reducing the amount of time needed to get relevant data for treatment efficacy of SBRT patients. Imple- mentation of this work into our ongoing clinical study will further provide insights into whether the 31P MSRI method can be an early predictor of normal tissue toxicity and/or treatment response.^
Andrew Hirsch, Purdue University, Ulrike Dydak, Purdue University.