18F-Fluorodeoxyglucose PET/MR Imaging in Head and Neck Cancer

Improved Cervical Lymph Node Characterization among Patients with Head and Neck Squamous Cell Carcinoma Using MR Texture Analysis Compared to Traditional FDG-PET/MR Features Alone

Accurate differentiation of benign and malignant cervical lymph nodes is important for prognosis and treatment planning in patients with head and neck squamous cell carcinoma. We evaluated the diagnostic performance of magnetic resonance image (MRI) texture analysis and traditional 18F-deoxyglucose positron emission tomography (FDG-PET) features. This retrospective study included 21 patients with head and neck squamous cell carcinoma. We used texture analysis of MRI and FDG-PET features to evaluate 109 histologically confirmed cervical lymph nodes (41 metastatic, 68 benign). Predictive models were evaluated using area under the curve (AUC). Significant differences were observed between benign and malignant cervical lymph nodes for 36 of 41 texture features (p < 0.05). A combination of 22 MRI texture features discriminated benign and malignant nodal disease with AUC, sensitivity, and specificity of 0.952, 92.7%, and 86.7%, which was comparable to maximum short-axis diameter, lymph node morphology, and maximum standard uptake value (SUVmax). The addition of MRI texture features to traditional FDG-PET features differentiated these groups with the greatest AUC, sensitivity, and specificity (0.989, 97.5%, and 94.1%). The addition of the MRI texture feature to lymph node morphology improved nodal assessment specificity from 70.6% to 88.2% among FDG-PET indeterminate lymph nodes. Texture features are useful for differentiating benign and malignant cervical lymph nodes in patients with head and neck squamous cell carcinoma. Lymph node morphology and SUVmax remain accurate tools. Specificity is improved by the addition of MRI texture features among FDG-PET indeterminate lymph nodes. This approach is useful for differentiating benign and malignant cervical lymph nodes.

PET/MR Imaging in Head and Neck Cancer

Head and neck squamous cell carcinoma (HNSCC) can either be examined with hybrid PET/MR imaging systems or sequentially, using PET/CT and MR imaging. Regardless of the acquisition technique, the superiority of MR imaging compared to CT lies in its potential to interrogate tumor and surrounding tissues with different sequences, including perfusion and diffusion. For this reason, PET/MR imaging is preferable for the detection and assessment of locoregional residual/recurrent HNSCC after therapy. In addition, MR imaging interpretation is facilitated when combined with PET. Nevertheless, distant metastases and distant second primary tumors are detected equally well with PET/MR imaging and PET/CT.

Clinical PET/MR

Oncologic imaging has been a major focus of clinical research on PET/MR over the last 10 years. Studies so far have shown that PET/MR with ¹⁸F-Fluorodeoxyglucose (FDG) overall provides a similar accuracy for tumor staging as FDG PET/CT. The effective radiation dose of whole-body FDG PET/MR is more than 50% lower than for FDG PET/CT, making PET/MR particularly attractive for imaging of children. However, the longer acquisition times and higher costs have so far limited broader clinical use of PET/MR technology for whole-body staging. With the currently available technology, PET/MR appears more promising for locoregional staging of diseases for which MR is the anatomical imaging modality of choice. These include brain tumors, head and neck cancers, gynecologic malignancies, and prostate cancer. For instance, PET imaging with ligands of prostate-specific membrane antigen, combined with multi-parametric MR, appears promising for detection of prostate cancer and differentiation from benign prostate pathologies as well as for detection of local recurrences. The combination of functional parameters from MR, such as apparent diffusion coefficients, and molecular parameters from PET, such as receptor densities or metabolic rates, is feasible in clinical studies, but clinical applications for this multimodal and multi-parametric imaging approach still need to be defined.

PET/MRI vs PET/CT in Head and Neck Imaging: When, Why, and How?

The increasing availability of hybrid PET/MRI systems has led to a breadth of new publications and opportunities for use of PET/MRI. While PET/CT has been a valuable tool for oncologic staging, including head and neck malignancy, there are several theoretical and practical advantages a PET/MRI system would have over PET/CT in head and neck imaging. This review article discusses the established role of PET/CT, early evidence for the role of PET/MRI, and protocol considerations for both PET/CT and PET/MRI as they apply to head and neck imaging.

Chapter 8 On the Horizon: Advanced Imaging Techniques to Improve Noninvasive Assessment of Cervical Lymph Nodes

Conventional imaging modalities are limited in the evaluation of lymph nodes as they predominantly rely on size and morphology, which have suboptimal sensitivity and specificity for malignancy. In this review we will explore the role of "on the horizon" advanced imaging modalities that can look beyond the size and morphologic features of a cervical lymph node and explore its molecular nature and can aid in personalizing therapy rather than use the "one-size-fits-all" approach.

Chapter 3 The Role of PET/CT in Squamous Cell Carcinoma of the Head and Neck

Head and neck squamous cell carcinoma is an important cause of cancer morbidity worldwide and has been stratified into human papillomavirus-related and human papillomavirus-unrelated subgroups that affect prognosis and now staging. Conventional anatomical imaging methods are suboptimal for the detection of regional and distant metastases that are important prognosticators associated with poor outcomes. Functional imaging with (F18)-fluorodeoxyglucose-positron emission tomography/computed tomography (PET/CT) is a useful tool in the management of head and neck squamous cell carcinoma, providing complementary physiological and anatomical information. In this article, optimal PET/CT technique will be reviewed and the pretreatment and posttreatment applications of PET/CT will be described. A simplified approach to imaging interpretation, including review of pearls and pitfalls will be discussed. An initial framework for follow-up evaluation will be provided.