Diffusion-Weighted and PET/MR Imaging After Radiation Therapy for Head and Neck Tumors

Targeted CE per ARRT’s Discipline, Category, and Subcategory classification:
[Note: Discipline-specific Targeted CE credits may be less than the total Category A credits approved for this course.]

Magnetic Resonance Imaging: 2.50
Patient Care: 0.25
Patient Interactions and Management: 0.25
Image Production: 0.75
Physical Principles of Image Formation: 0.50
Data Acquisition, Processing, and Storage: 0.25
Procedures: 1.50
Neurological: 1.50

Nuclear Medicine Technology: 0.50
Image Production: 0.50
Instrumentation: 0.50

Radiation Therapy: 0.50
Patient Care: 0.50
Patient and Medical Record Management: 0.50

Outline

1. Introduction
2. DW and PET/MR Imaging
3. Hybrid PET/MR Imaging and Multimodality Image Fusion
4. Key Findings at MR, DW, and PET/MR Imaging
   1. Expected Changes after Radiation Therapy
      1. Mucositis, Dermatitis, Soft-Tissue Edema, and Fibrosis
      2. Scar Tissue
      3. Sialadenitis and Xerostomia
      4. Replacement of Hemopoietic Marrow by Fatty Marrow and Activation after Chemotherapy
      5. Physiologic Functional and Metabolic Findings
   2. Complications after Radiation Therapy
      1. Soft-Tissue Necrosis and Granulation Tissue
      2. Osteoradionecrosis and Chondroradionecrosis
      3. Arteriopathy and Cerebrovascular Complications after Radiation Therapy
      4. Thyroid Disorders
      5. Radiation Therapy-induced Brain Necrosis
      6. Cranial Nerve Palsy
      7. Radiation Therapy-induced Tumors
   3. Treatment Failure and Recurrent Disease
5. Pitfalls
   1. Susceptibility Artifacts from Dental Hardware or Osteosynthesis Material
   2. Miscoregistration Artifacts
   3. Insufficient Scanner Resolution and Low FDG Avidity
   4. False-Positive Findings Due to Inflammatory and Infectious Diseases
   5. Incidentalomas
6. Conclusion

Objectives

Upon completion of this course, students will:

1. identify the cancer type that represents the vast majority of malignant head and neck tumors in adults
2. list the particles used in external beam radiation therapy for head and neck tumors
3. describe the currently preferred radiation therapy option for the head and neck
4. identify the IMRT dose range delivered to high-risk areas
5. list the imaging techniques that are routinely used in clinical practice to evaluate head and neck cancers
6. describe pathologies that exhibit increased water diffusion on DW imaging
7. explain the units of measurement of the apparent diffusion coefficient (ADC)
8. understand the diagnostic capabilities of FDG PET/CT for detection of head and neck SCC
9. recognize the value of FDG PET/CT in the evaluation of head and neck SCC
10. list the pathologies that may demonstrate increased FDG uptake and lead to false-positive PET/CT image findings
11. describe the mean SUV range of head and neck SCCs at FDG PET/CT imaging
12. list the hybrid imaging system design that uses MR imaging-based attenuation correction maps to calculate SUVs
13. compare the SUVs of focal lesions calculated at PET/MR with those calculated at PET/CT
14. describe the timing of early effects of high-dose radiation therapy
15. list the tissue types that typically demonstrate late effects of irradiation
16. list the late effects of radiation therapy
17. list the areas affected by radiation therapy-induced superficial lymphedema
18. describe the tissue features present in a mature scar
19. identify the imaging features that occur in the presence of scar tissue
20. define the imaging feature known as “evil gray”
21. list the body areas that may demonstrate high physiologic nonspecific FDG uptake
22. describe atypical locations of brown fat
23. recognize the diagnostic technique used to detect local mucosal destruction
24. describe the imaging characteristics of soft-tissue necrosis following administration of gadolinium contrast agents
25. identify the diagnostic techniques recommended for correlation with morphologic imaging when differentiating recurrent disease from benign soft-tissue necrosis
26. understand the time frame for the occurrence of osteoradionecrosis after radiation therapy
27. recognize the increased risk for osteoradionecrosis associated with radiation therapy doses of 62-70 Gy
28. list the most reliable imaging signs of osteoradionecrosis
29. describe the percentage of patients who may demonstrate chondroradionecrosis with recurrent tumor
30. recognize the most common manifestation of radiation therapy-induced arteriopathy in the head and neck
31. understand the effect of radiation therapy in the risk for development of thyroid disorders
32. identify the brain region typically involved with radiation therapy-induced brain necrosis
33. list the predisposing factors for radiation therapy-induced optic neuropathy
34. list the pathologies that may lead to radiation therapy-induced tumors in the head and neck
35. describe the imaging techniques that have limited value for precise assessment of deep tumor spread in the irradiated neck
36. identify the diagnostic technique that may be superior to PET/CT, CECT, and MR imaging for detection of small metastatic nodes
37. describe the diagnostic capabilities of FDG PET when investigating recurrent tumors and nodes after radiation therapy
38. understand the impact of the positive predictive value of PET/CT in the evaluation of recurrent tumors
39. list the areas where second primary tumors in patients with head and neck SCC recurrence are most often detected
40. define miscoregistration due to geometric distortion
41. describe the parameters of PET reconstructions in the head and neck
42. list the imaging findings of peritumoral inflammation
43. describe the percentage of thyroid incidentalomas that can be malignant
44. identify the pathologic condition that exhibits very low signal intensity on both T1- and T2-weighted MR images
45. identify the pathologic condition that demonstrates low ADCs