Aims and objectives
The aim of the current poster was to compare four diffusion models including mono-exponential and bi-exponential both Gaussian and non-Gaussian in patients with rectal adenocarcinoma.
Gaussian mono-exponential model associated to the Apparent Diffusion Coefficient (ADC),
Intravoxel Incoherent Motion (IVIM) model ,
non-Gaussian mono-exponential Kurtosis model ,
and extended non-Gaussian bi-exponential model  were used for comparison.
Methods and materials
Sixteen consecutive patients with rectal adenocarcinoma underwent MRI examination before chemoradiation therapy or surgery.
Diffusion weighted imaging (DWI) using a Spin-Echo Echo Planar Imaging sequence was acquired on a Philips Ingenia 1.5T system utilizing 6 b-values (0,
1000) assymetrically sampled to acquire more data on the low b-value area were microperfusion effects are more evident.
Mono-exponential and bi-exponential diffusion models were used both in Gaussian and non-Gaussian form to fit the data and extract the relevant diffusion imaging biomarkers.
Diffusion data were post processed by an in house software (ICS,
FORTH) which is able to produce pixel based parametric maps of a number of model related parameters.
All pixel values belonging to the tumor,
as marked by an expert radiologist,
were used as input for signal intensity curves as a function of b-value.
Model specific curves were grafically overlaid on the data in order to gain insight into each model performance qualitatively.
For visual and quantitative evaluation of each approach,
statisticalmetrics permitted direct comparison...
Non-Gaussian diffusion models proved to be more accurate to Gaussian models in fitting rectal cancer multi b-value diffusion data,
possiblydue to their sensitivity to depict not only microperfusion effects but also increased tumor heterogeneity.
“Separation of diffusion and perfusion in intravoxel incoherent motion MR imaging,” Radiology,
Jensen and J.
“MRI quantification of non-Gaussian water diffusion by kurtosis analysis,” NMR Biomed.,
“Extension of the intravoxel incoherent motion model...