Sci-Sat AM(1): Imaging-01: Tumour and normal tissue T2 and ADC distributions for a mouse model at 9.4T

Magnetic resonance (MR) measurements of relaxation times and diffusion coefficient in tissue have been demonstrated to be sensitive to biological changes induced by radiation therapy. We are currently using mouse models of human glioblastoma multiforme (GBM) to study tumour response to ionizing radiation by MRI at 9.4T. Utilizing conventional imaging techniques coupled with quantitative measurements of transverse relaxation time (T2) and apparent diffusion coefficient (ADC), we monitor changes during tumour growth and subsequent changes after single-fraction radiotherapy. In addition to tumour parameters, we have measured T2 and ADC in other structures that appear in the same transverse slices as tumour tissue. Here we report the measured distributions of T2 and ADC in tumour and in normal tissues that are likely to be encountered during MR imaging of tumour xenografts in mice, including liver, kidney, fat, skeletal muscle, spinal cord, and brain. Quantitative knowledge of these distributions in normal tissue is important in optimizing the sequences used for imaging of these tissues, and in optimizing continued measurements of T2 and ADC changes. Knowledge of parameter distributions in tumour is important because recent studies have suggested that the T2 and ADC responses after therapy may be the result of large shifts in smaller isolated pockets of tumour, rather than more moderate shifts in T2 and ADC over the whole tumour volume. These distributions provide a baseline measurement of typical distributions in advance of radiation therapy.