Role of diffusion-weighted echo-planar MR imaging in differentiation of residual or recurrent head and neck tumors and posttreatment changes

Abstract

Background and purpose: The purpose of this work was to evaluate whether diffusion-weighted MR imaging can be used in differentiating residual or recurrent head and neck tumors from postoperative or postradiation changes.

Materials and methods: This study included 32 patients clinically suspected for recurrent head and neck tumor after surgery (n=3), radiation therapy (n=13), or both (n=16). Diffusion-weighted MR imaging was done by using a single-shot spin-echo echo-planar sequence. The apparent diffusion coefficient (ADC) value of the suspected lesion was calculated and correlated with pathologic results.

Results: Adequate diffusion-weighted MR images and ADC maps were obtained in 30 patients (93.8%). The mean ADC value of residual or recurrent lesions (1.17 +/- 0.33 x 10(-3) mm(2)/s) was less than that of posttherapeutic changes (2.07 +/- 0.25 x 10(-3) mm(2)/s), and the difference was statistically significant (P<.001). When an ADC value of 1.30 x 10(-3) mm(2)/s was used as a threshold value for differentiation, the best results were obtained with an accuracy of 87%, sensitivity of 84%, specificity of 90%, positive predictive value of 94%, and negative predictive value of 76%.

Conclusions: Diffusion-weighted MR imaging with ADC measurement has promising results for differentiating residual or recurrent head and neck tumors from postoperative or postradiation changes.

Fig 1.

ADC map demonstrating the location of ROI in a patient with a recurrent nasopharyngeal mass.

Fig 2.

Recurrent oncocytic carcinoma of the right parotid gland. A, Axial T2WI, shown as ill defined, is seen at the site of the right parotid region after surgical resection and irradiation. B, Axial postcontrast T1WI shows the inhomogenous pattern of enhancement. Recurrence could not be excluded. C, ADC map shows low signal intensity at the site of the lesion with a mean ADC value of 1.07 ± 0.18 × 10⁻³ mm²/s. Biopsy revealed recurrent tumor.

Fig 3.

Recurrent squamous cell carcinoma of the nasal cavity. A, Axial postcontrast T1-weighted MR image shows that enhancing lesion is seen in the right side of the nasal cavity. Recurrent tumor cannot be differentiated from postradiation changes. B, ADC map shows hypointensity within the lesion with a low ADC value (1.17 ± 0.17 × 10⁻³ mm²/s).

Fig 4.

Recurrent squamous cell carcinoma of the oropharynx with metastatic cervical lymph node. A, Axial T2WI shows an ill-defined irregular mass of inhomogeneous signal intensity involving the right side of the oropharynx. An enlarged cervical lymph node (arrow) with inhomogeneous high signal intensity is also noted at the right side of the neck. B, ADC map shows low signal intensity of both the lesion and the lymph node with a mean ADC value of 1.20 ± 0.22 × 10⁻³ mm²/s and 1.05 ± 0.20 × 10⁻³ mm²/s, respectively, suggestive of tumor recurrence with metastatic lymph nodes. This was proved by biopsy.

Fig 5.

Bone marrow infiltration. A, Axial T2-weighted MR image shows an ill-defined inhomogeneous signal intensity involving the right greater wing of the sphenoid bone. B, ADC map shows low signal intensity at this region with a mean ADC value of 0.84 ± 0.30 × 10⁻³ mm²/s, suggestive of tumor infiltration, which was proved on bone marrow biopsy.

Fig 6.

Posttreatment changes after surgery and radiation therapy. A, Axial postcontrast T1WI shows an ill-defined, mildly enhancing mass at the region of the ethmoidal sinuses. Recurrence was suspected. B, ADC map shows high signal intensity at the site of the lesion denoting posttreatment fibrous tissue, which was proved by biopsy. The mean ADC value at the site of the posttreatment changes was 1.89 ± 0.19 × 10⁻³ mm²/s.

Fig 7.

Posttreatment changes after surgery and radiation therapy. A, Axial postcontrast T1WI shows a small ill-defined enhancing lesion at the site of the right parotid gland after surgical resection and irradiation. Recurrence could not be differentiated from posttreatment changes. B, ADC map shows low signal intensity at the site of the lesion with a mean ADC value of 1.07 ± 0.18 × 10⁻³ mm²/s. Biopsy revealed only attenuated fibrous tissue with no tumor cells.

Fig 8.

Box and whisker plot compares the mean ADCs of residual or recurrent tumors and posttreatment changes. The horizontal line is the median (50th percentile) of the measured values, the top and bottom of the box represent the 25th and 75th percentiles, respectively, and whiskers indicate the range from the largest to smallest observed data points. Note that despite the overlap between the ADC values of both groups, the ADCs of posttreatment changes are significantly higher than that of residual or recurrent tumors.