Optimization of b-values in diffusion-weighted imaging for esophageal cancer: Measuring the longitudinal length of gross tumor volume and evaluating chemoradiotherapeutic efficacy.

Purpose: To study the optimization of b-values of magnetic resonance-diffusion-weighted (MR-DWI) in evaluating the chemoradiotherapeutic efficacy for esophageal squamous cell carcinoma (ESCC) and measuring the longitudinal length of gross tumor volume (GTV) of ESCC. Materials and Methods: Eighteen patients with biopsy-proven ESCC were undergoing concurrent chemoradiotherapy (CCRT). Conventional magnetic resonance imaging (MRI) combined with DWI using b-values of 600 s/mm(2), 800 s/mm(2), and 1000 s/mm(2) was performed before CCRT and after the 1st, 3rd, 5th, and 10th weeks. The apparent diffusion coefficient (ADC) values of ESCC were derived from DWI using multiple b-values. The correlations between ADC values and apoptosis positive rates of ESCC cells obtained from the endoscope biopsy were statistically analyzed. Thirty-eight patients with confirmed ESCC who underwent radical surgery were analyzed. Longitudinal length of GTV of ESCC was measured using endoscopy, esophageal barium fluoroscopy, computed tomography (CT), and T2-weighted MRI and DWI using different b-values (b = 400, 600, and 800 s/mm(2)) before surgery and were compared with pathologic lesion length. Results: The ADC values of DWI images with different b-values are positively correlated with ESCC cell apoptosis positive ratios, the relation is significant, especially in the group of b = 1000 s/mm(2) (P < 0.01). The measured length of esophageal lesions from short to long was MR-DWI b = 800 s/mm(2), endoscopy, real tumor, MR-DWI b = 600 s/mm(2), esophageal barium fluoroscopy, CT, and MR-DWI b = 400 s/mm(2). Conclusion: MR-DWI b = 800 s/mm(2) and b = 1000 s/mm(2) are in favor of observing the chemoradiotherapeutic efficacy with time variation and evaluating the chemoradiotherapeutic efficacy, respectively. MR-DWI b = 600 s/mm(2) could be used as a supplementary means in measuring the length of ESCC.