Parathyroid Gland Imaging

1. Parathyroid Gland Imaging Frank P. Dawry

2. Physiology of Parathyroid Glands • Regulation of serum calcium levels via synthesis and release of parathyroid hormone (PTH) • Calcium release from bone – increased bone breakdown and resorption • Increase in GI tract absorption – increased calcium absorption in the bowel • Renal – increased release of serum phosphate levels -- direct inverse relationship to calcium levels Frank P. Dawry

3. Hyperparathyroidism condition of too much parathyroid hormone hyper = too muchparathyroid = parathyroid hormoneism = a disease or condition Frank P. Dawry

4. Indications In patients with hypercalcemia and elevated PTH levels Locate adenomas Single Multiple Identify glandular hyperplasia Shorten the operating time during surgery Finding hidden parathyroid glands – minimize exploration Contraindications Patient on calcium medications Patient on thyroid medications Frank P. Dawry

5. Anatomy Frank P. Dawry

6. Radiopharmaceuticals • Tc-99m Pertechnetate • Active transport into normal thyroid tissue • Tl-201 Thallous chloride • Behaves similar to potassium • Na/K pump • Enters thyroid and parathyroid tissue with blood flow • Tc-99m Sestamibi (Cardiolite) • Passive transport into thyroid and parathyroid tissue in proportion to blood flow • Remains longer in adenomas and hyperplastic tissue • Tc-99m Tetrofosmin (Myoview) • Passive transport into thyroid and parathyroid tissue in proportion to blood flow • Remains longer in adenomas and hyperplastic tissue Frank P. Dawry

7. Adult Dose Range • Tc-99m Pertechnetate • 5.0 – 12.0 mCi (185-444 MBq) • Tl-201 Thallous chloride • 2.0-3.0 mCi (74-111 MBq) • Tc-99m Sestamibi (Cardiolite) • 16.0-30.0 mCi (592-1110 MBq) • Tc-99m Tetrofosmin (Myoview) • 16.0-30.0 mCi (592-1110 MBq) • I-123 • 270 uCi (10 MBq) Frank P. Dawry

8. Equipment • LFOV camera • Pinhole and/or LEHR • Planar • 128x128 matrix • 1.0 million counts or 300-900 seconds/frame • SPECT • 360 degrees • 128x128 matrix • 20-25 seconds/stop Frank P. Dawry

9. Dual-Isotope Subtraction Technique Tl-201/Tc-99m – inferior Tc-99m/Cardiolite – superior Tc-99m/Myoview – little published data I-123/Cardiolite – superior I-123/Myoview – little published data Single-Nuclide Two-Phase (thyroid phase, parathyroid phase) Tc-99m Cardiolite Procedure Frank P. Dawry

10. Dual-Isotope SubtractionTechnique Variation • Administer I-123 • Wait 2-4 hours • Acquire 300 second acquisition using a pinhole collimator at 159 keV setting • Without moving the patient, inject ~15 mCi of Cardiolite • Wait 5 minutes • Acquire 300 second acquisition at 140 keV setting. • Possible to acquire both images at the same time using asymmetric windowing Frank P. Dawry

11. Processing • Normalize I-123 to thyroid counts in Tc-99m Cardiolite image • Subtract normalized I-123 image from Tc-99m Cardiolite image Positive = tissue remaining Frank P. Dawry

12. Raw I-123 image Draw ROI and obtain total counts in ROI Copy ROI to Sestamibi Image and obtain total counts in ROI Parathyroid Normalized I-123 Image multiply the Raw I-123 image counts by the ratio of I-123 ROI counts/Sestamibi ROI counts Subtracted Image Subtract normalized I-123 image from the Sestamibi image Frank P. Dawry

13. Frank P. Dawry

14. Single-Nuclide Two-Phase (thyroid phase, parathyroid phase) Technique • Inject Tc-99m Cardiolite • Wait 10 minutes • Acquire 300 second image of anterior neck using LEHR, 128x128 matrix • Acquire a planar static image again at 1 and 2 hours later Positive = slower washout structures within the image Frank P. Dawry

15. Frank P. Dawry

16. Combination of Dual-Isotope SubtractionTechnique andSingle-Nuclide Two-Phase Technique • Perform the Dual-Isotope SubtractionTechnique and have patient return 1 to 2 hours later to image the Sestamibi nuclide as in the Two-Phase Technique. Frank P. Dawry

17. SPECT/CT Frank P. Dawry