I-123 thyroid imaging
 Patient preparation
- Discontinue any medications that interfere with thyroid uptake of rodioiodine.
- NPO for 4 hours prior to study.
|Photon energy||159 keV|
|Adult dose||Routine uptake and scan (100-400 microCi po); thyroid cancer scan (1.5 mCi po)|
|Physical half life||13.2 hours|
|Biological half life|
|Normal distribution||Thyroid, nasopharynx, salivary glands, stomach, colon, bladder, lactating breasts|
|Pharmacokinetics||Rapidly absorbed from GI tract; detectable activity within gland in minutes; reaches thyroid follicular lumen in 20-30 min; trapping and organification rapid; delayed imaging for background clearance; image at 6 and 24 hours; 10-30% uptake at 24 hours.|
|Target organ||Thyroid, bladder, stomach, SI|
|Other||Secreted in breast milk; crosses placenta; may cause cretinism; discontinue interfering medications|
 Dose and route of administration
100-400 microCi orally in capsule form
 Time of imaging
At 4-6 or 24 hours
- Camera: Gamma camera
- Collimator: 3- to 6-mm aperture pinhole collimator
- Window: 20% energy window centered at 159 keV.
- Position the patient supine with the chin up and the neck extended.
- Position the collimator so that the thyroid fills about two-thirds of the diameter of the field of view.
- Obtain anterior, 45-degree LAO and RAO views (move the collimator, if possible, rather than the patient).
- Obtain 100k-250k counts per view.
- Mark the chin and suprasternal notch.
- Note the position and mark palpable nodules and surgical scars.
- Place marker sources lateral to the thyroid to calibrate size.