Aims and objectives
The aim of the current poster was to apply and compare four diffusion models including mono-exponentialand bi-exponentialboth Gaussian and non-Gaussian,
in hepatic metastases andnormal liver tissue.
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
10 patients with pancreatic cysts and no evidence of metastatic liverdisease (group A) and 10 consecutive patients with liver metastases (group B) underwent free breathing diffusion weighted imaging using 10 b values (0,
2000 and 3000).
ROIs inthe first group were drawn οn normal liver parenchyma avoiding vessels while for the second on liver metastatic tissue.
Four different models includingmono-exponential(Gaussian and non-Gaussian),as well as,
bi-exponential(Gaussian and non-Gaussian)were applied.
Mono-exponential and bi-exponential diffusion models were used both in Gaussian...
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 a 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 quantitative evaluation of each approach,
statisticalmetrics permitted direct comparison of the fitting...
Non-Gaussianbiexponentialdiffusion model proved to be more accurate in fitting hepatic metastases and normal liver tissue experimentaldata,as it can bothhighlight microperfusion effects in highly vascularized areas and also detect changes in tissue integrity as a result of perturbed diffusivity.
“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...