A Feasibility Study of Parametric Response Map Analysis of Diffusion-Weighted Magnetic Resonance Imaging Scans of Head and Neck Cancer Patients for Providing Early Detection of Therapeutic Efficacy

Abstract

The parametric response map (PRM) was evaluated as an early surrogate biomarker for monitoring treatment-induced tissue alterations in patients with head and neck squamous cell carcinoma (HNSCC). Diffusion-weighted magnetic resonance imaging (DW-MRI) was performed on 15 patients with HNSCC at baseline and 3 weeks after treatment initiation of a nonsurgical organ preservation therapy (NSOPT) using concurrent radiation and chemotherapy. PRM was applied on serial apparent diffusion coefficient (ADC) maps that were spatially aligned using a deformable image registration algorithm to measure the tumor volume exhibiting significant changes in ADC (PRM(ADC)). Pretherapy and midtherapy ADC maps, quantified from the DWIs, were analyzed by monitoring the percent change in whole-tumor mean ADC and the PRM metric. The prognostic values of percentage change in tumor volume and mean ADC and PRM(ADC) as a treatment response biomarker were assessed by correlating with tumor control at 6 months. Pixel-wise differences as part of PRM(ADC) analysis revealed regions where water mobility increased. Analysis of the tumor ADC histograms also showed increases in mean ADC as early as 3 weeks into therapy in patients with a favorable outcome. Nevertheless, the percentage change in mean ADC was found to not correlate with tumor control at 6 months. In contrast, significant differences in PRM(ADC) and percentage change in tumor volume were observed between patients with pathologically different outcomes. Observations from this study have found that diffusion MRI, when assessed by PRM(ADC), has the potential to provide both prognostic and spatial information during NSOPT of head and neck cancer.

Fractional Change in Apparent Diffusion Coefficient as an Imaging Biomarker for Predicting Treatment Response in Head and Neck Cancer Treated with Chemoradiotherapy

“…16 In the functional diffusion map, treatment response is evaluated on the basis of the fractional volume of significantly increased ADC within tumor. In the study by Galbán et al 17 of the functional diffusion map of HNSCC, the change in ADC assessed by the functional diffusion map was superior to the percentage change of the mean ADC in prediction of disease control after chemoradiotherapy. Therefore, in the future, more automated evaluations, such as a voxel-by-voxel approach, may be needed to estimate the change in ADC during treatment more accurately.…”

Difusion-Weighted MRI: from Brownian Motion to Head and Neck Tumor Characterization

“…A treatment-induced increase in ADC during therapy for head and neck squamous cell carcinoma has been confirmed in several studies, and results suggest that tumors that show a lower increase or even a decrease in ADC are more likely to fail treatment [24,28,30,31,32] (Fig. 14 & 15).…”

“…The general consensus appears to be that ADCs of malignant lymph nodes are significantly lower than those of normal lymph nodes [13,23,24]. Threshold ADC values (1.0-1.38x10 -3 mm 2 /s) have been reported to differentiate between malignant and benign lymph nodes [13,23,25] (Fig.…”

Evaluation of parametric response mapping to assess therapeutic response to human mesenchymal stem cells after experimental stroke

“…We first computed the 95% confidence interval (CI) for the classification of ADC values, as previously described. 23 Briefly, we empirically calculated, in the sham animals, the threshold that yields a significant change in ADC value for each voxel between D3 and D7. The ADC threshold (120 mm 2 /s) was determined by the 95% unchanged CI resulting from linear least squares analysis on the data combined from all 12 rats of the sham group (data not shown).…”