Imaging of the Head and Neck following Radiation Treatment

Abstract

Squamous cell carcinoma of the head and neck occurs in approximately 40,000 patients annually in the United States and is often treated with radiation therapy. Radiological studies are obtained following treatment for head and neck malignancies to assess for recurrent tumor, posttreatment changes, and associated complications. Radiation treatment creates a difficult clinical picture for oncologists, head and neck surgeons, neuroradiologists, and neuropathologists. As post-treatment imaging studies are often discussed at radiology/pathology working conferences, knowledge of the imaging appearance of radiation-associated changes in the head and neck and the terminology used by neuroradiologists may not only aid in interpretation of the pathologic specimen, but also assist in communications with neuroradiologists and referring clinicians.

Diffusion-weighted and PET/MR Imaging after Radiation Therapy for Malignant Head and Neck Tumors

“…High-dose radiation therapy required for treatment of malignant head and neck tumors affects normal tissues included in the radiation therapy portal (12). Early effects typically occur after the first 1-2 weeks after the start of radiation therapy (49). They are seen in tissues with rapid cell renewal (epithelial and hematopoietic stem cells), where frequent mitosis is required to maintain organ function (12).…”

“…The radiologist performing imaging of the head and neck in patients who have undergone radiation therapy must differentiate between expected changes after radiation therapy, potential complications of radiation therapy, and residual or recurrent tumor (4,13,15,49). High-dose radiation therapy required for treatment of malignant head and neck tumors affects normal tissues included in the radiation therapy portal (12).…”

“…Radiation therapy-induced fibrosis is associated with expression of inflammatory cytokines (transforming growth factor [TGF]-b), which stimulate fibroblast proliferation, differentiation into fibrocytes, and collagen production. Fibrosis due to radiation therapy is a dynamic process with an apparently uncontrolled remodeling phase and increased severity over time (49,50). The extent of radiation therapyinduced fibrosis and organ atrophy may differ from one patient to another, even if identical radiation therapy treatments are used (50), and it has been suggested that genetic factors, additional chemotherapy, corticosteroid administration, and fractionation schedule may contribute to variability in individual radiosensitivity (51).…”

Decreased Tongue Volume Post Radiation

“…22 Osteoradionecrosis of the jaw is associated with diffuse enhancement of the masseter and pterygoid muscles, as well as adjacent soft tissues, while mucositis demonstrates enhancement and edema of the mucosa. 23,24 The imaging findings for skeletal muscles have only been described on the basis of the masticator muscles, 25 and, to date, have not been applied to the musculature of the tongue. Furthermore, imaging findings related to radiation changes have yet to be discussed in the context of head and neck cancers post-CRT.…”

Lymph Node Ultrasound-Guided Fine-Needle Aspiration

“…4,6 Solutions to improve the US image quality when faced with any of the previously mentioned factors include using the lowest frequency transducer available to increase tissue penetration (at the expense of losing resolution), adjusting the overall gain and time gain compensation functions on the US machine, and repositioning the transducer or patient to image the target from the thinnest area of subcutaneous fat if obesity is the problem or to scan away from or redirect the US beam away from overlying scar tissue if possible. However, interpretation of these imaging studies in patients with these particular factors presents a new set of problems.…”