Diagnostic value of retrospective PET-MRI fusion in head-and-neck cancer.

BACKGROUND: To assess the diagnostic value of retrospective PET-MRI fusion and to compare the results with side-by-side analysis and single modality use of PET and of MRI alone for locoregional tumour and nodal staging of head-and-neck cancer. METHODS: Thirty-three patients with head-and-neck cancer underwent preoperative contrast-enhanced MRI and PET/CT for staging. The diagnostic data of MRI, PET, side-by-side analysis of MRI and PET images and retrospective PET-MRI fusion were systematically analysed for tumour and lymph node staging using receiver operating characteristic (ROC) analysis. The results were correlated to the histopathological evaluation. RESULTS: The overall sensitivity/specificity for tumour staging for MRI, PET, side-by-side analysis and retrospective PET-MRI fusion was 79%/66%, 82%/100%, 86%/100% and 89%/100%, respectively. The overall sensitivity/specificity for nodal staging on a patient basis for MRI, PET, side-by-side analysis and PET-MRI fusion was 94%/64%, 94%/91%, 94%/82% and 94%/82%, respectively. MRI, PET, side-by-side analysis and retrospective image fusion were associated with correct diagnosis/over-staging/under-staging of N-staging in 70.4%/18.5%/11.1%, 81.5%/7.4%/11.1%, 81.5%/11.1%/7.4% and 81.5%/11.1%/7.4%, respectively.ROC analysis showed no significant differences in tumor detection between the investigated methods. The Area Under the Curve (AUC) for MRI, PET, side-by-side analysis and retrospective PET-MRI fusion were 0.667/0.667/0.702/0.708 (p > 0.05). The most reliable technique in detection of cervical lymph node metastases was PET imaging (AUC: 0.95), followed by side-by-side analysis and retrospective image fusion technique (AUC: 0.941), which however, was not significantly better then the MRI (AUC 0.935; p > 0.05). CONCLUSIONS: We found a beneficial use of multimodal imaging, compared with MRI or PET imaging alone, particular in individual cases of recurrent tumour disease. Side-by-side analysis and retrospective image fusion analysis did not perform significantly differently.

PET-MRI fusion in head-and-neck oncology: current status and implications for hybrid PET/MRI.

PURPOSE: To review the current status and clinical effect of PET-MRI image fusion in the staging of head-and-neck cancer and to show its implications for imaging with future hybrid PET/MRI scanners. MATERIALS AND METHODS: We reviewed the current literature in order to provide an overview of the potential of the combination of the anatomic and functional imaging capabilities of magnetic resonance imaging (MRI) and of the potential for molecular and metabolic imaging with Positron emission tomography (PET). The research question was whether these image devices might be of synergistic value. RESULTS: PET with [18F]-fluorodeoxyglucose has shown promising results for the assessment of lymph node involvement in cancer, the identification of distant metastasis and synchronous and metachronous tumors, and the evaluation of tumor recurrence or carcinoma of an unknown primary. For morphologic imaging, MRI has several advantages compared with computed tomography in the head-and-neck area. This is mainly because of the superior soft tissue contrast and fewer artifacts from dental implants. Moreover, MRI allows functional imaging, such as the assessment of perfusion with dynamic contrast-enhanced MRI. The published data indicate that image fusion should be beneficial in the case of the recurrence of oromaxillofacial cancer and in the evaluation of potential metastatic lymph nodes. However, retrospective image fusion is technically demanding in the head-and-neck area, mainly because of the varied patient positions used for the various scanners and the anatomic complexity of this region. CONCLUSIONS: Combined PET/MRI scanners might overcome the above-named problems. Both sequential and fully integrated PET/MRI scanners are now available in selected departments, and future studies will show whether hybrid PET/MRI is of greater clinical value than PET/CT and retrospective image fusion techniques.