Relationships between histogram analysis of ADC values and complex 18F-FDG-PET parameters in head and neck squamous cell carcinoma

Abstract

Purpose: Histogram analysis is an emergent imaging technique to further analyze radiological images and to obtain imaging biomarker. In head and neck cancer, MRI and PET are routinely used in clinical practice. The aim of this study was to analyze associations between histogram based ADC parameters and complex FDG-PET derived parameters in head and neck squamous cell carcinoma (HNSCC).

Methods: 34 patients (26% female, mean age, 56.7 ± 10.2 years) with primary HNSCC were prospectively included into the study. ADC histogram parameters were calculated by inhouse made matlab software using a whole lesion measurement. For each tumor, maximum and mean standardized uptake values (SUVmax, SUVmean), Total Lesion Glycolysis (TLG) and Metabolic Tumor Volume (MTV) were determined on PET-images. Spearman's correlation coefficient (ρ) was used to analyze associations between investigated parameters. Benjamini-Hochberg correction was used to adjust for multiple testing. Mann-Whitney test was used for group discrimination. P-values < 0.05 were taken to indicate statistical significance.

Results: The correlation analysis in the whole tumor group revealed a statistically significant correlation between entropy and MTV as well as TLG (ρ = 0.67, P<0.0001 and ρ = 0.61, P = 0.0002 respectively). There were statistically significant differences between T1/2 and T3/4 tumors in the following parameters: entropy (2.07 ± 0.36 vs 2.61 ± 0.43, P = 0.007), SUVmax (10.79 ± 4.13 vs 17.93 ± 5.89, P = 0.007), SUVmean (6.39 ± 2.48 vs 9.81 ± 4.49, P = 0.01), SUVmin (4.09 ± 1.57 vs 6.34 ± 2.59, P = 0.03), MTV (9.50 ± 7.92 vs 20.36 ± 13.30, P = 0.02), TGU (55.97 ± 39.09 vs 212.3 ± 186.3, P = 0.002).

Conclusion: This study showed that entropy derived from ADC maps is strongly associated with MTV and TLG in HNSCC. Entropy, SUVmax, SUVmean, TLG and MTV were statistically significant higher in T3/4 tumors in comparison to T1/2 carcinomas.

Fig 1. Imaging findings in a 67 year old woman with cT3 cN2b cM0-oropharyngeal carcinoma.

a. Fused PET/CT image shows enhanced glucose metabolism in the main tumor as well as in lymph node metastases cervical. b. A polygonal VOI, that include the entire lesion in the axial, sagittal and coronal planes, was placed in the PET dataset (SUV_max threshold 40%). The acquired PET parameters are as follows: SUV_max = 16.82, SUV_mean = 10.01, SUV_min = 6.56, MTV = 10.5, and TLG = 105.03. c. ADC map of the lesion. d. ADC histogram. The histogram analysis parameters (× 10⁻³ mm²s^-1) are as follows: ADC_min = 0.41, ADC_mean = 0.87, ADC_max = 1.85, P10 = 0.65, P25 = 0.73, P75 = 0.97, P90 = 1.13, median = 0.83, mode = 0.76, kurtosis = 6.24, skewness = 1.37, and entropy = 2.93.

Fig 2

Correlation heat map in the overall sample (a). b. summarizes the correlations of well differentiated, c of poor differentiated HNSCC.

Fig 3

a. Associations between MTV and ADC entropy in the overall sample (ρ = 0.67, P<0.0001). b. Correlation between TLG and ADC entropy in the overall sample (ρ = 0.61, P = 0.0002).

Fig 4

a. Comparison of ADC entropy between different tumors. ADC entropy is statistically significant higher in T3/4 than T1/2 tumors (2.61 ± 0.43 vs 2.07 ± 0.36, p = 0.007). b. Comparison of SUVmax between different tumors. SUVmax is statistically significant higher in T3/4 than in T1/2 tumors (17.93 ± 5.89 vs 10.79 ± 4.13, p = 0.007). c. Comparison of TLG between different tumors. TLG is higher in T3/4 than in T1/2 tumors (212.3 ± 186.3 vs 55.97 ± 39.09, p = 0.002).