Functional imaging of head and neck squamous cell carcinoma with diffusion-weighted MRI and FDG PET/CT: quantitative analysis of ADC and SUV

Abstract

Purpose: Head and neck squamous cell carcinoma (HNSCC) may cause a decreased apparent diffusion coefficient (ADC) on diffusion-weighted magnetic resonance imaging (DW MRI) and an increased standardized uptake value (SUV) on fluorodeoxyglucose (FDG) positron emission tomography (PET/CT). We analysed the reproducibility of ADC and SUV measurements in HNSCC and evaluated whether these biomarkers are correlated or independent.

Methods: This retrospective analysis of DW MRI and FDG PET/CT data series included 34 HNSCC in 33 consecutive patients. Two experienced readers measured tumour ADC and SUV values independently. Statistical comparison and correlation with histopathology was done. Intra- and inter-observer agreement for ADC and SUV measurements was assessed.

Results: Intraclass correlation coefficient (ICC) analysis showed almost perfect reproducibility (>0.90) for ADCmean, ADCmin, SUVmax and SUVmean values for intra-observer and inter-observer agreement. Mean ADCmean and ADCmin in HNSCC were 1.05 ± 0.34 × 10(-3) mm(2)/s and 0.65 ± 0.29 × 10(-3) mm(2)/s, respectively. Mean SUVmean and mean SUVmax were 7.61 ± 3.87 and 12.8 ± 5.0, respectively. Although statistically not significant, a trend towards higher SUV and lower ADC was observed with increasing tumour dedifferentiation. Pearson's correlation analysis showed no significant correlation between ADC and SUV measurements (r -0.103, -0.051; p 0.552, 0.777).

Conclusion: Our data suggest that ADC and SUV values are reproducible and independent biomarkers in HNSCC.

Fig. 1

Anatomically matched corresponding transverse slices of inverted b1000 (a), PET (b), fused T2-weighted, b1000 (c) and fused PET/CT (d) images of a 63-year-old male with primary squamous cell carcinoma of the hypopharynx staged T4a N2c M0. Both PET/CT and MRI fused images allow correct anatomic assessment of the hypopharyngeal lesion that invades the retrocricoarytenoid region and both piriform sinuses

Fig. 2

Anatomically matched corresponding transverse slices of inverted b1000 (a), PET (b), fused T2-weighted, b1000 (c) and fused PET/CT (d) images of a 59-year-old patient with primary undifferentiated carcinoma of the nasopharynx staged T4 N3 M0. Both PET/CT and MRI fused images allow correct anatomic assessment of the right nasopharyngeal carcinoma that extends to the skull base, parapharyngeal and retropharyngeal space

Fig. 3

Intra-observer reproducibility measurements in tumours of ADC_mean (a), SUV_mean (b), ADC_min (c) and SUV_max (d). Bland–Altman plots of relative difference values (in %) of measurements (y-axis) against relative mean values (in %) of measurements (x-axis). The mean absolute difference (bias) and 95 % CI of the mean difference (1.96 SD) are equally indicated

Fig. 4

Inter-observer reproducibility measurements in tumours of ADC_mean (a), SUV_mean (b), ADC_min (c) and SUV_max (d). Bland–Altman plots of relative difference values (in %) of measurements (y-axis) against relative mean values (in %) of measurements (x-axis). The mean absolute difference (bias) and 95 % CI of the mean difference (1.96 SD) are equally indicated

Fig. 5

Scatter plots represent results of linear regression between ADC_mean and SUV_mean (a), ADC_mean and SUV_max (b), ADC_min and SUV_mean (c) and ADC_min and SUV_max (d). ADCs are expressed in 10⁻³ mm²/s. For each scatter plot, the best-fit line is shown. No statistically significant correlation was found between ADC and SUV values