Apparent diffusion coefficient measurement of the parotid gland parenchyma

Maja Bruvo; Faisal Mahmood

doi:10.21037/qims-20-1178

Apparent diffusion coefficient measurement of the parotid gland parenchyma

Quant Imaging Med Surg. 2021 Aug;11(8):3812-3829. doi: 10.21037/qims-20-1178.

Authors

Maja Bruvo¹, Faisal Mahmood^{2

3}

Affiliations

¹ Radiography, Department of Technology, Faculty of Health, University College Copenhagen, Copenhagen, Denmark.
² Laboratory of Radiation Physics, Department of Oncology, Odense University Hospital, Odense, Denmark.
³ Research Unit for Oncology, Department of Clinical Research, University of Southern Denmark, Odense, Denmark.

Abstract

The measurements of apparent diffusion coefficient (ADC) with diffusion weighted magnetic resonance imaging (DW-MRI) is becoming a popular diagnostic and research tool for examination of parotid glands. However, there is little agreement between the reported ADC values of the parotid gland in published literature. In this review 43 studies on ADC measurement of the parotid glands were included. The analyses indicated several possible culprits of the observed ADC discrepancies. For example, DW-MRI examinations under gustatory stimulation gives higher ADC values compared to the unstimulated parotid gland (P=0.003). The diffusion weighting factors (b-values) can either increase (b-value <200 s/mm²) or decrease ADC values (b-values >1,000 s/mm²). The timing of follow-up DW-MRI after radiotherapy (RT) indicates correlation to the found ADC values (R² =0.39). Interestingly, the choice of regions of interest (ROI) appears not to affect the measurements of ADC (P=0.75). It can be concluded that there is a critical need for standardization of ADC measurement of the parotid glands to allow valid inter-study comparisons and eventually to reach consensus on the use of ADC as biomarker.

Keywords: Diffusion weighted magnetic resonance imaging (DW-MRI); apparent diffusion coefficient; parotid gland parenchyma.

Publication types

Review