The added value of DW-MRI in characterization of tissue in treated head and neck tumors

الملخص EN

Treatment-induced tissue changes are menacing the early detection of recurrent tumor in the head and neck area.

The accuracy of conventional MRI techniques has been similar to CT scan in the post-radiotherapeutic neck. Objective: The aim of this prospective pilot study was to determine the additional value of diffusion-weighted imaging (DW-MRI) to conventional and dynamic contrast-enhanced MR imaging (DCE-MRI) to distinguish recurrent from nontumoral post-treatment changes in different head and neck tumors.

Materials and Methods: 20 patients with suspected recurrence of head and neck tumors either at the primary site or in neck nodes underwent imaging with MRI using the following protocols: T1W and fast T2W-SE images; pre and post-contrast DCE with delayed fat-suppressed post-contrast T1W images; DW- MRI, using a b-value = 1000 s/mm2.

A comparison between the results of the different modalities with the pathology results was done.

Results: Time intensity curves (TIC) for DCE-MRI, showed rapid and high amplitude of enhancement with short distribution time in 8 cases, gradual enhancement with slow washout in 5 cases and rapid enhancement with plateau in TIC in 7 patients.

The mean ADC value of recurrent lesions was 0.58± 0.24x10–3 mm2/s, while the mean value of post-therapeutic changes was 1.47 ± 0.31x10–3 mm2/s (p< 0.001).

If ADC ² 0.94x10–3 mm2/s, the lesion is malignant (specificity 100%), while if ADC ³1.4x10–3 mm2/s the lesion is benign (sensitivity 100%).

Still a value between 0.94 and 1.4x10–3 mm2/s is equivocal.

Using ROC, an ADC value of 0.94 x10-3 mm2/s was chosen as a threshold value to differentiate between recurrent lesions and post-treatment changes, and the best results were achieved with an overall accuracy of 93.3%, sensitivity of 93.3%, specificity of 93.3%, PPV of 100%, and NPV of 100%.

Conclusion: Addition of DW-MRI to DCE-MRI has remarkably improved the efficacy of differentiating recurrent head and neck tumors from post-therapy alterations.