Thyroid Uptake and Imaging Flashcards
RP
Dose
TcO4-: 2-10 mCi IV (For imaging – not organified)
I123: 200-400 μCi oral capsule (For uptake – organified)
Indications
Increased or decreased TSH Abnormal US Evaluate RAIU Evaluate hyper/hypothyroidism Locate ectopic thyroid tissue
Contraindications
Allergic to iodine
Thyroid meds
Pregnant or breastfeeding
Iodine contrast study
Patient Prep
No dietary iodine x1-2 weeks
No iodine contrast or thyroid meds x4-6 weeks
NPO x4-6 hour before and 1 hour after
Positioning
Uptake: Sitting with chin up and plastic on suprasternal notch at a Standard distance
Scan: Supine w/ pillow under shoulders to hyperextend neck
Target Organ
Critical Organ
Method of Localization
Route or Excretion
- Target Organ – Thyroid
- Critical Organ – Thyroid and Stomach
- Method of Localization – Active transport
- Route of Excretion – Urinary
Procedure
Image first
Inject TcO4- and wait 15-20 minutes
Images: ANT; ANT w/ marker; RAO; RAO w/ marker; LAO; LAO w/ marker
Uptake measurement
Count capsule in dose calibrator when patient arrives
Count capsule in thyroid phantom – standard
Put dose away then count room background
Administer dose and instruct pt to return in 4, 6, and 24 hrs
Count neck at standard distance for 1 min
Count thigh for 1 min for background
Decay correct
(neck – thigh) ÷ (standard – background)
Computer Set Up
LEHR or Pinhole
128x128 (2.0 zoom)
Statics: 50-100k counts
Normal
Symmetrical uptake Pyramidal lobe in 35% of patients TcO4- - salivary glands, stomach 123I – nasopharynx, salivary glands, stomach 4-6 hours: 5-20% 24 hours: 7-35%
Abnormal
Focal hot spots
Cold spots
Enlarged thyroid (increased uptake) – graves disease
Decreased uptake – Hashimoto’s thyroid (hypothyroidism)
Nodules or goiters – Plummers
Treatment
Surgery
Ablation
Meds
