Frederick C. Damen PhD, Presenter: Nothing to Disclose

Shun-Yu Gao MD, Abstract Co-Author: Nothing to Disclose

Lei Tang MD, Abstract Co-Author: Nothing to Disclose

Yi Sui MS, Abstract Co-Author: Nothing to Disclose

Kejia Cai PhD, Abstract Co-Author: Nothing to Disclose

Ying-Shi Sun MD, PhD, Abstract Co-Author: Nothing to Disclose

Xiaohong Joe Zhou PhD, Abstract Co-Author: Nothing to Disclose

Parameters derived from non-Gaussian diffusion models, such as Fractional Order Calculus (FROC) model, have shown excellent correlation to important tissue properties such as heterogeneity and microstructure, opening new possibilities of using multi-parametric diffusion imaging markers for diagnosis and early assessment of tumor treatment. The purpose of this study is to monitor radiation therapy of metastatic brain tumors from small cell lung cancer in order to provide timely feedback on the success, or failure, of the treatment.

This study was performed, with IRB approval, on 5 patients (49.4±7.9 yr) with a total of 16 clinically proven metastatic brain tumors from small cell lung cancer. Diffusion weighted images were acquired using 17 b-values (0 – 4000 s/mm2) prior to radiation therapy and after every 3rd treatment. Diffusion coefficient D, intra-voxel tissue heterogeneity index β, and mean free diffusion length μ, were calculate by fitting the multi b-value diffusion images to the FROC model. ROIs were selected on pretreatment solid tumor regions, guided by T1+C, T2, FLAIR, and the DWI images. Means and standard deviations of D, β, and μ, were evaluated at each time point and analyzed verses the time relative to the start of treatment and accumulated radiation dosage (Gy) at 3Gy/fraction over 10 fractions given daily.

Tumor treatment responses consistent with positive post treatment neurological exams exhibited (a) increased mean (e.g., ΔD=0.2x10-3 mm2/s) and standard deviation (e.g., ΔD=0.1x10-3 mm2/s) of D, (b) decreased mean of β (e.g., Δβ=0.1), and (c) elevated mean of μ (e.g., Δμ=0.5μm). These findings can be explained by increased necrosis, decreased cellularity, and a high degree of intra-voxel tissue heterogeneity associated with treatment. Increased standard deviation of D suggested variation of treatment response throughout the tumors, as expected in haphazardly organized microstructures.

The additional information on intra-voxel heterogeneity provide by β, together with cellularity revealed by D and μ, can be used to more reliably and timely assess the radiation therapy efficacy of metastatic brain tumor from small cell lung cancer. Parameters from the FROC model may provide a sensitive way for monitoring cancer treatment.

Timely feedback on the efficacy of cancer treatment is useful for optimizing treatment strategies.

Damen, F, Gao, S, Tang, L, Sui, Y, Cai, K, Sun, Y, Zhou, X, Monitoring Radiation Therapy of Metastatic Brain Tumors from Small Cell Lung Cancer Using Non-Gaussian Diffusion MRI.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14012183.html