Abstract
PurposeTo evaluate fitting quality and repeatability of four mathematical models for diffusion weighted imaging (DWI) during tumor progression in mouse xenograft model of prostate cancer.MethodsHuman prostate cancer cells (PC-3) were implanted subcutaneously in right hind limbs of 11 immunodeficient mice. Tumor growth was followed by weekly DWI examinations using a 7T MR scanner. Additional DWI examination was performed after repositioning following the fourth DWI examination to evaluate short term repeatability. DWI was performed using 15 and 12 b-values in the ranges of 0-500 and 0-2000 s/mm2, respectively. Corrected Akaike information criteria and F-ratio were used to evaluate fitting quality of each model (mono-exponential, stretched exponential, kurtosis, and bi-exponential).ResultsSignificant changes were observed in DWI data during the tumor growth, indicated by ADCm, ADCs, and ADCk. Similar results were obtained using low as well as high b-values. No marked changes in model preference were present between the weeks 1−4. The parameters of the mono-exponential, stretched exponential, and kurtosis models had smaller confidence interval and coefficient of repeatability values than the parameters of the bi-exponential model.ConclusionStretched exponential and kurtosis models showed better fit to DWI data than the mono-exponential model and presented with good repeatability.
Highlights
Diffusion weighed imaging (DWI) has extensively been used for cancer characterization in both pre-clinical [1, 2] and clinical settings [3] during the last decade
Significant changes were observed in DWI data during the tumor growth, indicated by ADCm, ADCs, and ADCk
Stretched exponential and kurtosis models showed better fit to DWI data than the mono-exponential model and presented with good repeatability
Summary
Diffusion weighed imaging (DWI) has extensively been used for cancer characterization in both pre-clinical [1, 2] and clinical settings [3] during the last decade. DWI is increasingly being used for monitoring cancer therapy responses [4]. DWI contrast is predominantly affected by microscopic motion of water molecules and water interactions with surroundings. The most recognized DWI imaging acquisition method is the Stejskal– Tanner pulsed field gradient method. With this method, motion caused by self diffusion of a proton is acquired by applying a pair of motion-encoding gradients. The signal attenuation depends on water diffusion coefficient (D [mm2/s]) as well as direction of the self diffusion of water [5]
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