MRI with DWI for the Detection of Posttreatment Head and Neck Squamous Cell Carcinoma: Why Morphologic MRI Criteria Matter

DWIMRI obtained 13 months after RTH and neck dissection for squamous cell carcinoma of the larynx and oropharynx. The patient had massive weight loss, malnutrition, and recurrent aspiration pneumonia. Endoscopy showed intact mucosa and fixed vocal cords bilaterally. Axial T2 (A), T1 (B), and contrast-enhanced T1 (C) show a triangular lesion (arrows) in the left true vocal cord with very low signal intensity on T2, low signal intensity on T1, and faint contrast enhancement suggesting post-RTH late fibrosis. In contrast, the right vocal cord (dashed arrows) displays high signal intensity on T2, low signal on T1, and enhancement. Findings on the right were interpreted as suggesting inflammatory edema. The b=1000 image (D) and ADC map (E) reveal no restricted diffusion in the right vocal cord (ADCmean = 1.643 × 10⁻³ mm²/s) and restricted diffusion with low ADC in the left vocal cord (ADCmean = 1.006 × 10⁻³ mm²/s). Because the nonfunctional larynx was the cause of malnutrition and recurrent aspiration pneumonia, laryngectomy was performed. F, Corresponding whole-organ histologic slice (H&E) shows extensive muscle fibrosis on the left (arrows) and inflammatory edema with denervation on the right (dashed arrows).

DWIMRI obtained 3 months after RTH and bucopharyngectomy for squamous cell carcinoma of the retromolar trigone. The patient had right reflex otalgia and progressing trismus. Endoscopy could not be performed. Axial T2 (A) and coronal STIR (B) images show a triangular, elongated, strongly hypointense lesion (arrows) on the right. There was no contrast enhancement (not shown). The diagnosis of benign post-RTH late fibrosis was made. The b=1000 image (C) reveals low signal. ADC map (D) likewise shows low signal (ADCmean = 0.731 × 10⁻³ mm²/s). Follow-up at 38 months (not shown) showed no recurrence but progressive scar retraction on MRI.

Box-and-whisker plots of ADCmean values in patients with post-RTH changes and post-RTH tumors. The horizontal lines represent the median values, and the bottom and the top of the box represent the 25th and 75th quartiles, respectively. Median ADCmean (25th–75th quartiles) for rHNSCC/sHNSCC = 1.061 (0.907–1.191) × 10⁻³ mm²/s. Median ADCmean (25th–75th quartiles) for post-RTH changes (late fibrosis and inflammatory edema together) = 1.671 (1.3355–1.915) × 10⁻³ mm²/s.

Box-and-whisker plots of ADCmean values in patients with post-RTH inflammatory edema, late fibrosis, and post-RTH HNSCCs. The horizontal lines represent the median values; the bottom and the top of the box represent the 25th and 75th quartiles, respectively. Median ADCmean (25th–75th quartiles) for rHNSCC/sHNSCC = 1.061 (0.907–1.191) × 10⁻³ mm²/s. Median ADCmean (25th–75th quartiles) for post-RTH inflammatory edema = 1.764 (1.575–1.938) × 10⁻³ mm²/s. Median ADCmean (25th–75th quartiles) for late fibrosis/mature scar post-RTH = 1.068 (0.939–1.152) × 10⁻³ mm²/s. There was no statistically significant difference between ADCmean in late fibrosis and rHNSCC/sHNSCC (P > .05). However, there was a significant difference between ADCmean in inflammatory post-RTH edema and late fibrosis (P < .05).