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

Radiographics. 2015 Sep-Oct;35(5):1502-27. doi: 10.1148/rg.2015140029. Epub 2015 Aug 7.


Interpreting imaging studies of the irradiated neck constitutes a challenge because of radiation therapy-induced tissue alterations, the variable appearances of recurrent tumors, and functional and metabolic phenomena that mimic disease. Therefore, morphologic magnetic resonance (MR) imaging, diffusion-weighted (DW) imaging, positron emission tomography with computed tomography (PET/CT), and software fusion of PET and MR imaging data sets are increasingly used to facilitate diagnosis in clinical practice. Because MR imaging and PET often yield complementary information, PET/MR imaging holds promise to facilitate differentiation of tumor recurrence from radiation therapy-induced changes and complications. This review focuses on clinical applications of DW and PET/MR imaging in the irradiated neck and discusses the added value of multiparametric imaging to solve diagnostic dilemmas. Radiologists should understand key features of radiation therapy-induced tissue alterations and potential complications seen at DW and PET/MR imaging, including edema, fibrosis, scar tissue, soft-tissue necrosis, bone and cartilage necrosis, cranial nerve palsy, and radiation therapy-induced arteriosclerosis, brain necrosis, and thyroid disorders. DW and PET/MR imaging also play a complementary role in detection of residual and recurrent disease. Interpretation pitfalls due to technical, functional, and metabolic phenomena should be recognized and avoided. Familiarity with DW and PET/MR imaging features of expected findings, potential complications, and treatment failure after radiation therapy increases diagnostic confidence when interpreting images of the irradiated neck. Online supplemental material is available for this article.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Antineoplastic Agents / adverse effects
  • Antineoplastic Agents / therapeutic use
  • Artifacts
  • Brachytherapy / adverse effects
  • Brain / diagnostic imaging
  • Brain / pathology
  • Brain / radiation effects
  • Carcinoma, Squamous Cell / diagnostic imaging
  • Carcinoma, Squamous Cell / pathology
  • Carcinoma, Squamous Cell / radiotherapy
  • Cicatrix / diagnostic imaging
  • Cicatrix / etiology
  • Cicatrix / pathology
  • Combined Modality Therapy
  • Diffusion Magnetic Resonance Imaging / methods*
  • Edema / diagnostic imaging
  • Edema / etiology
  • Edema / pathology
  • Fibrosis
  • Head and Neck Neoplasms / diagnostic imaging
  • Head and Neck Neoplasms / drug therapy
  • Head and Neck Neoplasms / pathology
  • Head and Neck Neoplasms / radiotherapy*
  • Hematologic Diseases / chemically induced
  • Hematologic Diseases / diagnostic imaging
  • Hematologic Diseases / pathology
  • Humans
  • Incidental Findings
  • Multimodal Imaging / methods*
  • Necrosis
  • Neoplasm Recurrence, Local / diagnostic imaging
  • Neoplasm Recurrence, Local / pathology
  • Osteonecrosis / diagnostic imaging
  • Osteonecrosis / etiology
  • Osteonecrosis / pathology
  • Positron-Emission Tomography / methods*
  • Proton Therapy / adverse effects
  • Radiation Injuries / diagnostic imaging
  • Radiation Injuries / etiology
  • Radiation Injuries / pathology
  • Radiotherapy, Intensity-Modulated / adverse effects
  • Sialadenitis / diagnostic imaging
  • Sialadenitis / pathology
  • Thyroid Gland / radiation effects


  • Antineoplastic Agents