Frank P. DawryFrank P. Dawry

Parathyroid Gland ImagingParathyroid Gland Imaging

Frank P. DawryFrank P. Dawry

Physiology of Parathyroid GlandsPhysiology of Parathyroid Glands

Regulation of serum calcium levels via Regulation of serum calcium levels via synthesis and release of parathyroid synthesis and release of parathyroid hormone (PTH)hormone (PTH) Calcium release from bone – increased bone Calcium release from bone – increased bone

breakdown and resorptionbreakdown and resorption Increase in GI tract absorption – increased calcium Increase in GI tract absorption – increased calcium

absorption in the bowelabsorption in the bowel Renal – increased release of serum phosphate levels Renal – increased release of serum phosphate levels

-- -- direct inverse relationship to calcium levelsdirect inverse relationship to calcium levels

Frank P. DawryFrank P. Dawry

HyperparathyroidismHyperparathyroidism

condition of too much parathyroid hormonecondition of too much parathyroid hormone

hyper = too muchhyper = too muchparathyroid = parathyroid hormoneparathyroid = parathyroid hormoneism = a disease or conditionism = a disease or condition

Frank P. DawryFrank P. Dawry

IndicationsIndications In patients with hypercalcemiaIn patients with hypercalcemia

and elevated PTH levelsand elevated PTH levels Locate adenomasLocate adenomas

SingleSingle MultipleMultiple

Identify glandular hyperplasiaIdentify glandular hyperplasia Shorten the operating time during Shorten the operating time during

surgerysurgery Finding hidden parathyroid glands Finding hidden parathyroid glands

– minimize exploration– minimize exploration

ContraindicationsContraindications Patient on calcium Patient on calcium

medicationsmedications Patient on thyroid Patient on thyroid

medicationsmedications

Frank P. DawryFrank P. Dawry

AnatomyAnatomy

Frank P. DawryFrank P. Dawry

RadiopharmaceuticalsRadiopharmaceuticals Tc-99m PertechnetateTc-99m Pertechnetate

Active transport into normal thyroid tissueActive transport into normal thyroid tissue Tl-201 Thallous chlorideTl-201 Thallous chloride

Behaves similar to potassium Behaves similar to potassium Na/K pumpNa/K pump Enters thyroid and parathyroid tissue with blood flowEnters thyroid and parathyroid tissue with blood flow

Tc-99m Sestamibi (Cardiolite)Tc-99m Sestamibi (Cardiolite) Passive transport into thyroid and parathyroid tissue in Passive transport into thyroid and parathyroid tissue in

proportion to blood flowproportion to blood flow Remains longer in adenomas and hyperplastic tissueRemains longer in adenomas and hyperplastic tissue

Tc-99m Tetrofosmin (Myoview) Tc-99m Tetrofosmin (Myoview) Passive transport into thyroid and parathyroid tissue in Passive transport into thyroid and parathyroid tissue in

proportion to blood flowproportion to blood flow Remains longer in adenomas and hyperplastic tissueRemains longer in adenomas and hyperplastic tissue

Frank P. DawryFrank P. Dawry

Adult Dose RangeAdult Dose Range

Tc-99m PertechnetateTc-99m Pertechnetate 5.0 – 12.0 mCi (185-444 MBq)5.0 – 12.0 mCi (185-444 MBq)

Tl-201 Thallous chlorideTl-201 Thallous chloride 2.0-3.0 mCi (74-111 MBq)2.0-3.0 mCi (74-111 MBq)

Tc-99m Sestamibi (Cardiolite)Tc-99m Sestamibi (Cardiolite) 16.0-30.0 mCi (592-1110 MBq)16.0-30.0 mCi (592-1110 MBq)

Tc-99m Tetrofosmin (Myoview) Tc-99m Tetrofosmin (Myoview) 16.0-30.0 mCi (592-1110 MBq)16.0-30.0 mCi (592-1110 MBq)

I-123I-123 270 uCi (10 MBq)270 uCi (10 MBq)

Frank P. DawryFrank P. Dawry

EquipmentEquipment

LFOV cameraLFOV cameraPinhole and/or LEHRPinhole and/or LEHRPlanarPlanar

128x128 matrix128x128 matrix1.0 million counts or 300-900 seconds/frame1.0 million counts or 300-900 seconds/frame

SPECTSPECT360 degrees360 degrees128x128 matrix128x128 matrix20-25 seconds/stop20-25 seconds/stop

Frank P. DawryFrank P. Dawry

ProcedureProcedure

Dual-Isotope SubtractionDual-Isotope Subtraction

TechniqueTechnique Tl-201/Tc-99m – inferiorTl-201/Tc-99m – inferior Tc-99m/Cardiolite – superiorTc-99m/Cardiolite – superior Tc-99m/Myoview – little Tc-99m/Myoview – little

published datapublished data I-123/Cardiolite – superiorI-123/Cardiolite – superior I-123/Myoview – little I-123/Myoview – little

published datapublished data

Single-Nuclide Two-Phase Single-Nuclide Two-Phase (thyroid phase, (thyroid phase,

parathyroid phase)parathyroid phase) Tc-99m CardioliteTc-99m Cardiolite

Frank P. DawryFrank P. Dawry

Dual-Isotope SubtractionDual-Isotope SubtractionTechnique Technique

VariationVariation Administer I-123Administer I-123 Wait 2-4 hoursWait 2-4 hours Acquire 300 second acquisition using a pinhole Acquire 300 second acquisition using a pinhole

collimator at 159 keV settingcollimator at 159 keV setting Without moving the patient, inject ~15 mCi of CardioliteWithout moving the patient, inject ~15 mCi of Cardiolite Wait 5 minutesWait 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 Possible to acquire both images at the same time using asymmetric windowingasymmetric windowing

Frank P. DawryFrank P. Dawry

ProcessingProcessing

Normalize I-123 to thyroid counts in Tc-Normalize I-123 to thyroid counts in Tc-99m Cardiolite image99m Cardiolite image

Subtract normalized I-123 image from Tc-Subtract normalized I-123 image from Tc-99m Cardiolite image99m Cardiolite image

Positive = tissue remainingPositive = tissue remaining

Frank P. DawryFrank 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. DawryFrank P. Dawry

Frank P. DawryFrank P. Dawry

Single-Nuclide Two-Phase Single-Nuclide Two-Phase (thyroid phase, parathyroid phase)(thyroid phase, parathyroid phase)

TechniqueTechnique

Inject Tc-99m CardioliteInject Tc-99m Cardiolite Wait 10 minutesWait 10 minutes Acquire 300 second image of anterior neck Acquire 300 second image of anterior neck

using LEHR, 128x128 matrixusing LEHR, 128x128 matrix Acquire a planar static image again at 1 and 2 Acquire a planar static image again at 1 and 2

hours laterhours later

Positive = slower washout structures within the Positive = slower washout structures within the imageimage

Frank P. DawryFrank P. Dawry

Frank P. DawryFrank P. Dawry

Combination of Combination of Dual-Isotope Dual-Isotope SubtractionSubtraction

Technique Technique andand Single-Nuclide Two-Single-Nuclide Two-Phase Phase TechniqueTechnique

Perform the Dual-Isotope SubtractionPerform the Dual-Isotope SubtractionTechnique and have patient return 1 to 2 Technique and have patient return 1 to 2 hours later to image the Sestamibi nuclide hours later to image the Sestamibi nuclide as in the as in the Two-Phase Two-Phase Technique.Technique.

Frank P. DawryFrank P. Dawry

SPECT/CTSPECT/CT