Frank P. Dawry Parathyroid Gland Imaging

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

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

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

Frank P. Dawry Anatomy

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

Frank P. Dawry Adult Dose Range Tc-99m Pertechnetate Tc-99m Pertechnetate 5.0 – 12.0 mCi ( MBq) 5.0 – 12.0 mCi ( MBq) Tl-201 Thallous chloride Tl-201 Thallous chloride mCi ( MBq) mCi ( MBq) Tc-99m Sestamibi (Cardiolite) Tc-99m Sestamibi (Cardiolite) mCi ( MBq) mCi ( MBq) Tc-99m Tetrofosmin (Myoview) Tc-99m Tetrofosmin (Myoview) mCi ( MBq) mCi ( MBq) I-123 I uCi (10 MBq) 270 uCi (10 MBq)

Frank P. Dawry Equipment LFOV camera LFOV camera Pinhole and/or LEHR Pinhole and/or LEHR Planar Planar 128x128 matrix 128x128 matrix 1.0 million counts or seconds/frame 1.0 million counts or seconds/frame SPECT SPECT 360 degrees 360 degrees 128x128 matrix 128x128 matrix seconds/stop seconds/stop

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

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

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

Frank P. Dawry Draw ROI and obtain total counts in ROI Raw I-123 image Copy ROI to Sestamibi Image and obtain total counts in ROI 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 Parathyroid

Frank P. Dawry

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

Frank P. Dawry

Combination of Dual-Isotope Subtraction Technique and Single-Nuclide Two- Phase Technique Perform the Dual-Isotope Subtraction Technique and have patient return 1 to 2 hours later to image the Sestamibi nuclide as in the Two-Phase Technique. Perform the Dual-Isotope Subtraction Technique and have patient return 1 to 2 hours later to image the Sestamibi nuclide as in the Two-Phase Technique.

Frank P. Dawry SPECT/CT