Ni-14 * the Diffusion Weighted Imaging Derived Inflection B-value as a Potential Marker for Brain Tumor Heterogeneity
Year: 2014
Type: conference-abstract
Abstract: BACKGROUND: Diffusion-weighted MR (DWI) images are collected at different diffusion weightings (b-values) and the corresponding signal decreases as b-value increases. Typically, images are collected at two b-values to calculate an apparent diffusion coefficient (ADC). Calculating ADC in this way involves the underlying assumption that the diffusion-related signal decay is monoexponential. However, studies have shown this is often not the case at higher b-values (b > 1000 s/mm2). In this study, a biexponential model is used to model the DWI signal in a rat U87 brain tumor model. The inflection b-value (binf) is also introduced. This parameter is the b-value where the signal begins to deviate from monoexponential. METHODS: Eight male Athymic nude rats were inoculated with U87 brain tumor cells and imaged on day 18 post-inoculation without any treatment. Pre and post contrast T1-weighted images were collected. DWI images were acquired prior to contrast injection with b = 0,50,100,150,200,400,600,800,1000,2000,3000 s/mm2. Tumor ROIs were determined from the contrast-enhancing region on the T1 + C images. Contralateral normal ROIs were also drawn. The DWI signal was fit with a biexponential model: S/S0 = ffast*exp(-b*Dfast) + (1-ffast)*exp(-b*Dslow). The inflection b-value was computed as the minimum of the third derivative of the natural log of the biexponential fit. Biexponential parameters and binf were compared between tumor and normal tissue with a paired two-sample t-test. RESULTS: No differences were seen between tumor and normal tissue for any of the biexponential parameters. The inflection b-value (binf) was significantly lower in tumor compared to normal tissue (1920(160) vs. 3280(340) respectively, P = 0.008). CONCLUSIONS: The inflection b-value (i.e. the b-value where the DWI signal deviates from monoexponential) was lower in tumor tissue compared to normal tissue. Deviation from monoexponential behavior is thought to occur due to the presence of multiple diffusion pools and restrictions to water movement. Therefore, binf is a potential marker of tumor heterogeneity and/or invasion.
Source: Neuro-Oncology
Authors: A. Cohen, K. Pechman, K. Schmainda
Institution: Medical College of Wisconsin
Language: English
Subfield: Radiology, Nuclear Medicine and Imaging
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W2330806355