SPECT/CT of Radioiodine Biodistributions

The role of SPECT/CT in assessing physiologic uptake of radioiodine, normal variants, and metastatic disease mimics is presented.

Course ID: Q00378 Category:
Modalities: ,


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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.]

Nuclear Medicine Technology: 2.50
Procedures: 2.50
Radionuclides and Radiopharmaceuticals: 0.50
Endocrine and Oncology Procedures: 1.50
Other Imaging Procedures: 0.50

Registered Radiologist Assistant: 1.00
Procedures: 1.00
Musculoskeletal and Endocrine Sections: 1.00

Radiation Therapy: 1.00
Patient Care: 0.50
Patient and Medical Record Management: 0.50
Procedures: 0.50
Treatment Sites and Tumors: 0.50


  1. Introduction
  2. Mechanisms of Radioiodine Uptake and Distribution
  3. Radioiodine SPECT/CT
    1. Imaging Protocol
    2. Head and Neck Region
    3. Thorax
    4. Abdomen and Pelvis
  4. Conclusion


Upon completion of this course, students will:

  1. know the isotopes used for traditional planar thyroid scintigraphy
  2. recognize the estimated patient dose range per region of interest from the CT portion of a SPECT/CT study
  3. identify the body regions typically associated with benign distributions of radioiodine
  4. understand the function of the sodium-iodide symporter (NIS) glycoprotein
  5. understand the relationships between NIS function and iodine concentration in thyroid cells
  6. identify the similarity between human and animal NIS genetic coding
  7. identify the hormones involved with concentration of iodine in breast milk
  8. recognize unusual sites of metastases that can be evaluated by SPECT/CT
  9. understand the process of thyroglobulin production in the thyroid follicles
  10. identify the hormones produced by the thyroid gland
  11. recognize standard techniques for elucidating areas of questionable radioiodine uptake
  12. identify the body regions where iodine is actively transported by NIS
  13. identify “third-space” bodily fluids where radioiodine may concentrate
  14. recognize a typical dose of 131I when administered orally with endogenous TSH
  15. recognize a typical dose of 131I when administered orally with exogenous recombinant human TSH
  16. recognize the imaging delay for planar whole-body images and static images of the neck and thorax after 131I administration
  17. understand the processes responsible for radioiodine uptake in the teeth
  18. understand the process responsible for radioiodine uptake in the mediastinal blood pool
  19. understand the purpose of leaving remnant thyroid tissue during thyroidectomy
  20. identify the causes for neck uptake to be labeled as equivocal or indeterminate on planar images
  21. identify the hyoid bone as a site of intense focal uptake in the midline of the central neck
  22. recognize the components of the “tripod” configuration of radioiodine uptake in the neck
  23. identify the processes that may cause focal oral uptake that can mimic osseous metastases
  24. understand the conditions that may arise from prior radioiodine treatment of the salivary glands
  25. identify the imaging techniques used to identify uptake at the site of a tracheostomy tube
  26. recognize the patterns of esophageal retention of radioiodine secretions
  27. understand the imaging characteristics found after esophagectomy or gastric pull-through surgery
  28. recognize the uptake pattern associated with excretion of radioiodine into breast milk
  29. identify the patterns of uptake associated with thymic tissue in pediatric patients
  30. identify the expected sites of physiologic radioiodine uptake in the abdomen and pelvis
  31. understand the imaging interventions that can be used to characterize physiologic radioactivity in the bowel resulting from enteric excretions
  32. identify the process that may cause uptake of radioiodine in the liver on post-therapy 131I images
  33. understand the cause of radioiodine accumulation in patients with diverticulitis or those who have undergone bowel surgery
  34. identify the radioisotopes that are routinely used for thyroid imaging procedures
  35. identify the radioisotopes that are routinely used for thyroid uptake procedures
  36. identify the radioisotope used in thyroid imaging that has the longest physical half-life
  37. recognize the emission energy associated with 123I
  38. recognize the compounds used for thyroid imaging that are associated with the greatest safety risks
  39. identify the collimators that are used during 123I sodium iodide imaging of the thyroid
  40. recognize an example of a normal range of RAIU thyroid function at 4 to 6 hours