Jacobus F.A. Jansen
Notwithstanding recent advances in surgical and oncologic treatments, the overall survival rate of patients with head and neck squamous cell carcinoma (HNSCC) has unfortunately not improved considerably over recent years. A priori predictors of outcome are desperately needed to advance patient care; for example non-invasive imaging markers might have a role in clinical decision-making, allowing oncologists to intervene with alternative therapies if necessary.
One of these imaging techniques is diffusion-weighted imaging (DWI), which can provide detailed information regarding the microstructure of tissue. For the head and neck region, DWI has been used extensively for characterizing the precise pathology and evaluating treatment. Especially the apparent diffusion coefficient (ADC) metric has been proven to provide valuable information. Intriguingly, it has been reported that different DWI acquisition protocols (e.g., using different b-values) can yield substantially different ADC values,1 which is counterintuitive as the ADC is a generic property of tissue, and should be independent of the acquisition protocol. The explanation for this is the use of an incorrect assumption, commonly employed for clinical applications, namely that water diffusion in biologic tissues is Gaussian and hence the behavior of the DWI signal intensity mono-exponential. In a seminal paper by Jensen et al,2 the concept of diffusional kurtosis imaging (DKI) was introduced, which enables the assessment of the non-Gaussian diffusion behavior, by quantifying the excess kurtosis, Kapp, a dimensionless metric of the departure from a Gaussian form.
Our paper, which I wrote as a research scholar in the group of Amita Shukla-Dave at Memorial Sloan Kettering Cancer Center (MSKCC), describes the first application of the concept of DKI to an oncological setting, in particular HNSCC. We found that the DKI model not only yields a more reliable estimate of the ADC due to a significantly better fit, but also that in 44% of the tumors, the additional parameter Kapp was independent of the ADC, indicative of a potentially added value. Our paper was well received and has been cited prominently in the field, for example by researchers working on DKI in prostate,3 liver,4 lung,5 and brain6 pathology.
Currently in 2014, studies are ongoing evaluating the clinical added value of Kapp in HNSCC at MSKCC. Additionally, my collaborators at MSKCC and I have been actively pursuing methodological advancements of novel non-Gaussian diffusion models, for example by incorporating the intravoxel