Quantitative diffusion weighted MRI: a functional biomarker of nodal disease in Hodgkin lymphoma?

This study explores the relationship between MRI Apparent Diffusion Coefficient (ADC) and PET Standardized Uptake Value (SUV) measurements in pediatric Hodgkin lymphoma.

Sixteen patients (mean age 15.4 yrs, 8 male) with proven Hodgkin lymphoma were recruited and staged using PET-CT, anatomical MRI and additional 1.5T diffusion weighted imaging (DWI) prior to and following chemotherapy. Pre-treatment lymph nodes and anatomically paired post-treatment residual tissue located on MRI were matched to the corresponding PET-CT. Region of interest (ROI) analysis was used to extract quantitative measurements. Mean ADC (ADC(mean)) and maximum SUV (SUV(max)) were recorded and correlation assessed using Spearman statistics.

Fifty-three ROIs were sampled. Pre- and post-treatment ADC(mean) ranged from 0.77 × 10(−3) to 1.79 × 10(−3) (median 1.15 × 10(−3) mm(2)s(−1)) and 1.08 × 10(−3) to 3.18 ×10(−3) (median 1.88 × 10(−3) mm(2)s(−1)), and SUV(max) from 2.60 to 25.4 (median 8.85 mg/ml) and 1.00 to 3.50 mg/ml (median 1.90 mg/ml). Median post-treatment ADC(mean) was higher, and median SUV(max) lower than pretreatment values (p < 0.0001). There was an inverse correlation between pre-treatment ADC(mean) and SUV(max) (p = 0.005) and between fractional change ([post-treatment – pre-treatment]/pre-treatment)in ADC(mean) and SUV(max) (p =0.002).

Our results confirm a strong reciprocal relationship between nodal ADC(mean) and SUV(max) in Hodgkin lymphoma;supporting the potential application of quantitative DWI as a functional biomarker of disease.