3D 31P MRSI of human liver: A spatially resolved study of normal and malignant tissue in response to stereotactic body radiation therapy
Over 80% of all hepatocellular cancer (HCC) cases that present to the clinic do not qualify for surgical intervention. Stereotactic body radiotherapy (SBRT) therapy has gained increased attention as a relatively safe and effective alternative to surgical intervention. SBRT is a non-invasive highly conformal radiation therapy that is capable of delivering high doses of ionizing radiation to small treatment volumes. The high radiosensitivity of the liver requires strict radiation dose limits to maintain normal tissue complication probabilities to less than 5%. However, the radiosensitivity across the HCC patient population is highly variable and not well characterized. Indeed, the tolerance dose limits for HCC patients could be underestimated, but more information is needed before the relationships between radiation dose, biological response, and normal tissue toxicities can be clearly defined. Currently, imaging techniques capable of providing both spatial and functional information regarding the radiobiological response of both normal and malignant liver tissue are needed.^ The goal of this research is to investigate the feasibility of using three-dimensional (3D) 31P magnetic resonance spectroscopic imaging (MRSI) to evaluate the metabolic changes in normal and malignant liver tissue 24-72 hours after the first SBRT treatment fraction. The relationship between the observed 31P metabolic activity of adenosine triphosphate (ATP), inorganic phosphate (Pi), phosphomonoesthers (PME) and phosphodiesthers (PDE) are compared to an independently quantified estimate of regional radiation dose, and compared to standard clinical methods of evaluating the therapeutic response of both normal and malignant liver. The resulting analysis will characterize the use of 31P MSRI as an early predictor of normal tissue toxicity and/or treatment response and provide important data to determine if this method is feasible as a basis for individualized dose optimization strategies.^
Ulrike Dydak, Purdue University.
Health Sciences, Medicine and Surgery|Health Sciences, Radiology|Physics, General