Apparent Diffusion Coefficient as a Biomarker: Image Quality and Repeatability

Diffusion-weighted (DW) MRI is based on the Brownian motion of water in biological tissues. The technique has played a preponderant role in neuro-imaging over the last two decades and it is known to detect small changes before they are apparent on anatomical imaging.

In recent years DW MRI has been increasingly used in other parts of the body, demonstrating great diagnostic potential in cancer imaging. To date, DW MRI has been successfully used for tissue characterisation and tumour staging. However, the apparent diffusion coefficient (ADC) is a potential biomarker that could be used to monitor treatment response or evaluate post-therapeutic changes.

While DW MRI is a potentially powerful tool in diagnostic oncology, the lack of uniform protocols for imaging and data analysis hinder its clinical implementation. Large differences in ADC values are reported in the literature depending on the acquisition parameters, in particular the choice of b-values. A consensus and recommendation paper published in 2009 highlighted the importance of quality analysis, validation and reproducibility studies. To facilitate clinical research that make use of ADC as a biomarker and in particular multi-centre trial, we are carrying out research in the quality of ADC measurements. In particular, we have studied the repeatability of ADC both in-vitro and for a range of organs. We also investigated the effect of the choice of analysis (whole organ, volume, region of interest) on the ADC value.

Mean ADC
Figure 1. Mean ADC for the spleen for two visits and different analysis methods (Miquel et al., 2012)

ADCs are measured using MRI sequences that can be prone to artefacts, and in collaboration with Imperial College, we studied the differences in image quality between manufacturers and scanner magnetic field strength.

Comparison of Diffusion
Figure 2. Comparison of diffusion artefacts using different manufacturers (Lavdas et al., 2014)

For further details, please see:

Miquel ME, Scott AD, McDougall ND, Boubertakh R, Bharwani N, Rockall A (2012) In-vitro and in-vivo repeatability of abdominal diffusion weighted MRI. British Journal of Radiology 85:1507-12.

Lavdas I, Miquel ME, McRobbie DW, Aboagye EO (2014) Comparison between diffusion-weighted magnetic resonance imaging (DW-MRI) at 1.5T and 3T: A phantom study. Journal of Magnetic Resonance Imaging 40:682-90.

Jafar MM, Parsai A, Miquel ME (2016) Diffusion-weighted magnetic resonance imaging in cancer: Reported apparent diffusion coefficient, in-vitro and in-vivo reproducibility. orld Journal of Radiology 8:21-49.

Collaborators:

Ioannis Lavdas, Imperial College London