NUCLEAR MEDICINE IN DIAGNOSIS AND TREATMENT OF Thyroid DISEASES

NUCLEAR MEDICINENUCLEAR MEDICINE ININDIAGNOSIS AND TREATMENT OF DIAGNOSIS AND TREATMENT OF Thyroid DISEASESThyroid DISEASES

M.MoslehiM.Moslehi

Nuclear physicianNuclear physician

Diagnostic AimDiagnostic Aim

Imaging MethodsImaging Methods

Advantages of Thyroid Advantages of Thyroid Scintigram over other Imaging Scintigram over other Imaging TechniquesTechniques

Allowing correlation of physical Allowing correlation of physical exam and anatomical imaging exam and anatomical imaging findings with physiology.findings with physiology.

PATIENT PREPARATIONPATIENT PREPARATION

Need to cease anti thyroid drugs or thyroxine Need to cease anti thyroid drugs or thyroxine replacement prior to scanning - ( in consultation replacement prior to scanning - ( in consultation with the referring doctor).with the referring doctor).

Scanning Techniques & Scanning Techniques & DevicesDevices

Scanning Techniques & Scanning Techniques & DevicesDevices

Scanning Techniques & Scanning Techniques & DevicesDevices

Radiopharmaceuticals

• Tc-99m pertechnetate– Trapped but non-organified – fast release

– E=140 keV, T/2=6 hours

• I-123– Optimal for diagnosis – pure gamma emitter

– E=159 keV, T/2=13 hours

• I-131– Used for therapy (beta radiation)

– Egama=364 keV, T/2=8 days

The thyroid

RADIONUCLIDE GENERATORSRADIONUCLIDE GENERATORS allow to separate chemically short-allow to separate chemically short-lived radioactive daughter nuclei with good characteristics for medical lived radioactive daughter nuclei with good characteristics for medical imaging from long-lived radioactive parent nuclei.imaging from long-lived radioactive parent nuclei.

Milking cow analogy

Comparison of lifespan death risk from nuclear Comparison of lifespan death risk from nuclear medicine procedures with the lifespan death medicine procedures with the lifespan death risk of smoking, driving in a highway and risk of smoking, driving in a highway and natural irradiationnatural irradiation

Type of scanType of scan DoseDose SmokingSmokingNo. of No. of

cigarettescigarettes

DrivingDrivingIn a In a

highwahighwayy

Brain scanBrain scan 2020((mCimCi))99m99mTc HMPAOTc HMPAO

149149 582582( ( KmKm))

BoneBone 202099m99mTc MDPTc MDP

7979 308308

KidneyKidney22 202099m99mTc DTPATc DTPA

4444 171171

Myocardial scanMyocardial scan 20-4020-4099m99mTc sestimibiTc sestimibi

164164 639639

Lung perfusion Lung perfusion scanscan

55 99m99mTc MAATc MAA

2828 109109

Lung Ventilation Lung Ventilation scanscan

101081m81mKrKr

<<11 0.50.5

Thyroid scanThyroid scan 5599m99mTc Tc

pertecnetatepertecnetate

2828 110110

INTERNATIONAL COMMISSION ON INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION RADIOLOGICAL PROTECTION ————————————————————————————————————————————————————————— ———————————————————

Nuclear medicine and Nuclear medicine and pregnant patientspregnant patients……Most diagnostic procedures are done with Most diagnostic procedures are done with

short-lived radionuclides (such as short-lived radionuclides (such as technetium-99technetium-99mm) that do not cause large ) that do not cause large fetal dosesfetal doses

Often, fetal dose can be reduced through Often, fetal dose can be reduced through maternal hydration and encouraging voiding maternal hydration and encouraging voiding of urineof urine

Some radionuclides do cross the placenta Some radionuclides do cross the placenta and can pose fetal risks (such as iodine-131)and can pose fetal risks (such as iodine-131)

INTERNATIONAL COMMISSION ON INTERNATIONAL COMMISSION ON RADIOLOGICAL PROTECTION RADIOLOGICAL PROTECTION ————————————————————————————————————————————————————————— ———————————————————

Nuclear medicine and Nuclear medicine and pregnant patient (cont’d)pregnant patient (cont’d)

The fetal thyroid accumulates iodine after The fetal thyroid accumulates iodine after about 10 weeks gestational ageabout 10 weeks gestational age

High fetal thyroid doses from radioiodine High fetal thyroid doses from radioiodine can result in permanent hypothyroidismcan result in permanent hypothyroidism

If pregnancy is discovered within 12 h of If pregnancy is discovered within 12 h of radio-iodine administration, prompt oral radio-iodine administration, prompt oral administration of stable potassium iodine administration of stable potassium iodine (60-130 mg) to the mother can reduce (60-130 mg) to the mother can reduce fetal thyroid dose. This may need to be fetal thyroid dose. This may need to be repeated several timesrepeated several times

Recommendations for cessation of breast Recommendations for cessation of breast

feedingfeeding radiopharamceutradiopharamceut

icicdosedose Imaging Imaging

procedureprocedureCessation Cessation

timetime

Tc-pertechnetateTc-pertechnetate 55 mcimci Thyroid scanThyroid scan 2424 hrshrs

Tc-DTPATc-DTPA 10-15mci10-15mci Renal scanRenal scan 1717 hrshrs

Tc-SCTc-SC 5mci5mci Liver-spleen Liver-spleen scanscan

1515 hrshrs

Tc-MDPTc-MDP 15-25mci15-25mci Bone scanBone scan 1717 hrshrs

Ga-67Ga-67 6-10mci6-10mci Infection and Infection and tumor scantumor scan

44 wkswks

TL-201TL-201 3mci3mci Myocardial Myocardial perfusion scanperfusion scan

33 wkswks

I-131I-131 10micro and 10micro and moremore

Thyroid scan Thyroid scan and therapyand therapy

discontinuediscontinue

TC-MAATC-MAA 3-5mci3-5mci Lung perfusion Lung perfusion scanscan

1010 hrshrs

Which oneWhich one??

I-131:I-131: is not the agent of choice is not the agent of choice for routine diagnostic for routine diagnostic scintigraphies (because of high scintigraphies (because of high energy emissions and the long energy emissions and the long half life).half life).

Technetium-99m:Technetium-99m: A frequently A frequently used alternative.used alternative.

Physical Characteristics of Physical Characteristics of Tc-99mTc-99m

Half life: 6 hrHalf life: 6 hr

Generator producedGenerator produced

Usual dose: 3-10 millicurieUsual dose: 3-10 millicurie

Tc-99m Thyroid Tc-99m Thyroid Scintigraphy: ApplicationsScintigraphy: Applications

Further evaluation of findings on physical Further evaluation of findings on physical examination.examination.

To determine the functional status of To determine the functional status of thyroid nodules.thyroid nodules.

Detection of extrathyroidal tissue (such Detection of extrathyroidal tissue (such as lingual thyroid).as lingual thyroid).

Differential diagnosis of hyperthyroidism.Differential diagnosis of hyperthyroidism.

Normal Thyroid Normal Thyroid ScintigramScintigram

Normal Thyroid ScintigramNormal Thyroid Scintigram

Thyroid NoduleThyroid Nodule

The major challenge is to determine The major challenge is to determine whether a thyroid nodule is benign whether a thyroid nodule is benign or malignantor malignant

Most important tools in the Most important tools in the assessment of thyroid nodulesassessment of thyroid nodules

History and clinical examHistory and clinical exam

Thyroid Function TestsThyroid Function Tests

Fine Needle Aspiration (FNA)Fine Needle Aspiration (FNA)

Thyroid ScanThyroid Scan

Scintigraphy in Evaluation of Scintigraphy in Evaluation of Thyroid NodulesThyroid Nodules

Can not be used to exclude or confirm Can not be used to exclude or confirm the malignancy.the malignancy.

FNA with Scintigraphy is a more direct FNA with Scintigraphy is a more direct meansmeans

Scintigraphic classification of Scintigraphic classification of thyroid nodulesthyroid nodules

Cold (Hypofunctioning)Cold (Hypofunctioning)

Hot (Functioning)Hot (Functioning)

Indeterminate: Function Indeterminate: Function equals to that of surrounding equals to that of surrounding normal thyroidnormal thyroid

A Functional Thyroid A Functional Thyroid NoduleNodule

A Functional Thyroid A Functional Thyroid NoduleNodule

Thyroid Nodules (continue)Thyroid Nodules (continue)

• Nonfunctioning nodules appear cold and Nonfunctioning nodules appear cold and require further evaluation by FNA. require further evaluation by FNA.

• Autonomously functioning nodules may Autonomously functioning nodules may appear hot . Only a few patients with appear hot . Only a few patients with autonomous nodules have been found to autonomous nodules have been found to have thyroid cancer , and only a few of have thyroid cancer , and only a few of these cancers were aggressive . these cancers were aggressive . Furthermore, in some of these patients, Furthermore, in some of these patients, the cancer was adjacent to the the cancer was adjacent to the autonomous nodule rather than within it.autonomous nodule rather than within it.

Multinodular GoiterMultinodular Goiter

Multinodular GoiterMultinodular Goiter

Cold NoduleCold Nodule

Cold NoduleCold Nodule

Differential Diagnosis of Differential Diagnosis of thyrotoxicosisthyrotoxicosis

GraveGrave’’s Diseases Disease

Toxic Multinodular goiterToxic Multinodular goiter

Toxic AdenomaToxic Adenoma

ThyroiditisThyroiditis

Thyrotoxicosis FactitiaThyrotoxicosis Factitia

GraveGrave’’s Diseases Disease

GraveGrave’’s Diseases Disease

ThyroiditisThyroiditis

Clinical Picture (can be confusing)Clinical Picture (can be confusing)

Plasma Levels of Thyroid Plasma Levels of Thyroid Hormones (may be misdiagnosed Hormones (may be misdiagnosed as Graveas Grave’’s Dis.)s Dis.)

Scan PatternScan Pattern

RAIURAIU

Subacute thyroiditis

Tc-99m pertechnetate

Ectopic Thyroid TissueEctopic Thyroid Tissue

lingual, substernal, pelvic/ovarian lingual, substernal, pelvic/ovarian teratoma (struma ovarii)teratoma (struma ovarii)

Pertechnetate is not useful for Pertechnetate is not useful for imaging the substernal area due to imaging the substernal area due to attenuation or superimposed blood attenuation or superimposed blood pool activitypool activity

Thyroglossal duct cystThyroglossal duct cyst

Midline along the migratory path of the embryologic gland, Midline along the migratory path of the embryologic gland, anywhere from the foramen cecum at the base of the anywhere from the foramen cecum at the base of the tongue to the lower necktongue to the lower neck

The vast majority of patients have normal thyroid scans.The vast majority of patients have normal thyroid scans.

Complications: Infection, and rarely papillary thyroid Complications: Infection, and rarely papillary thyroid carcinomacarcinoma

Physical Characteristics of I-131Physical Characteristics of I-131

Half-life of 8.05 days Half-life of 8.05 days

Emits a high energy gamma (364 Emits a high energy gamma (364 keV) and particulate emissions keV) and particulate emissions

Reactor producedReactor produced

Dose of I-131Dose of I-131

DiagnosticDiagnostic

1.1. Retrostenal Goiter: 50-200 MicrocurieRetrostenal Goiter: 50-200 Microcurie

2.2. whole body scans for following of whole body scans for following of thyroid carcinoma: 2-5 mCithyroid carcinoma: 2-5 mCi

TherapeuticTherapeutic1.1. Non-neoplastic applications: 5-29 mCiNon-neoplastic applications: 5-29 mCi

2.2. Differentiated thyroid CA: 100-200 mCiDifferentiated thyroid CA: 100-200 mCi

I-131 Thyroid Scintigraphy: I-131 Thyroid Scintigraphy: ApplicationsApplications

Evaluation of a substernal massEvaluation of a substernal mass

Detection of persistent residual Detection of persistent residual tissue after thyroid surgery for DTCtissue after thyroid surgery for DTC

Detection of regional cervical lymph Detection of regional cervical lymph node involvement or distant node involvement or distant metastatic involvementmetastatic involvement

Substernal Thyroid MassesSubsternal Thyroid Masses

I-131 is the preferred imaging agent due to I-131 is the preferred imaging agent due to mediastinal blood pool activity with Tc-99m mediastinal blood pool activity with Tc-99m and significant attenuation of low energy and significant attenuation of low energy gamma photons by sternum gamma photons by sternum

Most intra-thoracic goiters demonstrate Most intra-thoracic goiters demonstrate anatomic continuity, but not necessarily anatomic continuity, but not necessarily functional continuity with cervical thyroid functional continuity with cervical thyroid tissue.tissue.

Multinodular Goiter with Multinodular Goiter with Retrosternal ExtensionRetrosternal Extension

Radioactive Iodine Uptake Radioactive Iodine Uptake Test (RAIU)Test (RAIU)

useful assessment of thyroid useful assessment of thyroid function function

the higher the iodine uptake, the the higher the iodine uptake, the more active the gland more active the gland

Normal 24 hour RAIU = 8 to 35% Normal 24 hour RAIU = 8 to 35%

Normal 4 hour RAIU = 5 to 15%Normal 4 hour RAIU = 5 to 15%

IndicationsIndicationsTo confirm hyperthyroidism To confirm hyperthyroidism

To calculate therapeutic dose of I-131 To calculate therapeutic dose of I-131

To determine the cause of To determine the cause of thyrotoxicosisthyrotoxicosis

** high RAIU uptake in "true ** high RAIU uptake in "true hyperthyroidismhyperthyroidism““

** low RAIU in thyroiditis or who ** low RAIU in thyroiditis or who abuse thyroid abuse thyroid hormoneshormones

Therapeutic AimTherapeutic Aim

γγ-emitters-emitters

ββ-emitters-emitters

Radiation toxicityRadiation toxicity

• Critical site Critical site – stem cells of bone marrow stem cells of bone marrow

• May be affectedMay be affected– LiverLiver– ThyroidThyroid– Urinary tract Urinary tract

• SometimesSometimes– Normal tissue adjacent to the target Normal tissue adjacent to the target

tissue tissue

131131I therapyI therapy

• IndicationsIndications– Thyroid carcinomaThyroid carcinoma– ThyrotoxicosisThyrotoxicosis– Non-toxic goiterNon-toxic goiter

Results (Results (in hyperthyroidism)in hyperthyroidism)

Cure > 90% with a single doseCure > 90% with a single dose

Most patients eventually become Most patients eventually become hypothyroid (need for replacement hypothyroid (need for replacement hormone therapy)hormone therapy)

Lower risk of hypothyroidism after Lower risk of hypothyroidism after treatment of solitary hyperfunctioning treatment of solitary hyperfunctioning nodulesnodules

I-131 Therapy For Nontoxic I-131 Therapy For Nontoxic GoitersGoiters

Reduction of thyroid volume in Reduction of thyroid volume in patients with non-toxic patients with non-toxic multinodular goiter. multinodular goiter.

Goiter size can decreased by about Goiter size can decreased by about 40% after 1 year and 50-60% after 40% after 1 year and 50-60% after 3 to 5 years 3 to 5 years

The dose is approximately 100 uCi The dose is approximately 100 uCi of I-131 per gram of thyroid tissue, of I-131 per gram of thyroid tissue, corrected for RAIU at 24 hourscorrected for RAIU at 24 hours

Important Contra-indications For Important Contra-indications For Treatment of HyperthyroidismTreatment of Hyperthyroidism

Pregnancy should be ruled Pregnancy should be ruled out (avoiding of pregnancy 6 out (avoiding of pregnancy 6 to 12 months after treatment) to 12 months after treatment)

Minimal ComplicationsMinimal Complications

No statistically significant increase in thyroid and No statistically significant increase in thyroid and other malignanciesother malignancies

No reduction in fertilityNo reduction in fertility

No congenital defect in children of treated individualsNo congenital defect in children of treated individuals

Thyroid storm after therapy as a riskThyroid storm after therapy as a risk

Local neck pain, tenderness and swelling for few Local neck pain, tenderness and swelling for few daysdays

INTERNATIONAL INTERNATIONAL COMMISSION ON COMMISSION ON

RADIOLOGICAL RADIOLOGICAL PROTECTION PROTECTION ————————— —————————————————— —————————————————— —————————————————— ——————————— ——

Pre-conception irradiationPre-conception irradiationPre-conception irradiation of either Pre-conception irradiation of either

parent’s gonads has parent’s gonads has notnot been shown to been shown to result in increased risk of cancer or result in increased risk of cancer or malformations in childrenmalformations in children

This statement is from comprehensive This statement is from comprehensive studies of atomic bomb survivors as studies of atomic bomb survivors as well as studies of patients who had well as studies of patients who had been treated with radiotherapy when been treated with radiotherapy when they were childrenthey were children

Instructions for the Patient Instructions for the Patient (Received 131-I 5-29 mci)(Received 131-I 5-29 mci)

1.1. Avoid close contact with children and Avoid close contact with children and pregnant women for at least the first pregnant women for at least the first 2 days (occasional hug is not harmful)2 days (occasional hug is not harmful)

2.2. Maintain a careful distance from Maintain a careful distance from others for at least the first 2 days others for at least the first 2 days (two arm lengths).(two arm lengths).

3.3. Sleep alone in a room for at least the Sleep alone in a room for at least the first night.first night.

Instruction for the Patient Instruction for the Patient (cont,)(cont,)

4.4. Do not travel by airplane or mass Do not travel by airplane or mass transportation for at least the first day.transportation for at least the first day.

5.5. Do not travel on a prolonged Do not travel on a prolonged automobile trip ( >2 hours) with automobile trip ( >2 hours) with others for at least the first 2 days.others for at least the first 2 days.

6.6. Flush the toilet 3 times after use.Flush the toilet 3 times after use.

7.7. Avoid mouth to mouth contact for at Avoid mouth to mouth contact for at least 1 weekleast 1 week

Instruction for the Patient Instruction for the Patient (cont,)(cont,)

8.8.Clothing worn during the first 3 days Clothing worn during the first 3 days after the therapy dose that was after the therapy dose that was directly in contact with skin should directly in contact with skin should be laundered separately. be laundered separately.

9.9.Drink plenty of extra fluids for 2 Drink plenty of extra fluids for 2 daysdays

Radiation detectors at ports of Radiation detectors at ports of entryentry

• It is possible that patients treated It is possible that patients treated with 131I could trigger alarms at with 131I could trigger alarms at such detection sites for 95 days or such detection sites for 95 days or longer after treatment.longer after treatment.

• If, within 4 months of receiving 131I If, within 4 months of receiving 131I therapy, travel is planned a form therapy, travel is planned a form should be provided to the patientshould be provided to the patient

Contraindication of 131-I Contraindication of 131-I therapytherapy

• PregnancyPregnancy

• Breast feedingBreast feeding

Contraindication of 131-I Contraindication of 131-I therapytherapy• A pregnancy test must be performed before A pregnancy test must be performed before

thethe

time (usually within 72 hours).time (usually within 72 hours).

• Pregnancy should be delayed for at least 6 Pregnancy should be delayed for at least 6 months after radioiodine therapy, a delay months after radioiodine therapy, a delay based on the need to normalize thyroid based on the need to normalize thyroid levels for a successful pregnancy and levels for a successful pregnancy and healthy infant development, and to ensure healthy infant development, and to ensure that additional radiation treatment is not that additional radiation treatment is not imminent.imminent.

Contraindication of 131-I Contraindication of 131-I therapytherapy• Lactating breast concentrates a substantial Lactating breast concentrates a substantial

amount of iodideamount of iodide

• Breastfeeding must be stopped at least 6 Breastfeeding must be stopped at least 6 weeks before administration of 131I therapy, weeks before administration of 131I therapy, and a delay of 3 months will more reliably and a delay of 3 months will more reliably ensure that lactation-associated increase in ensure that lactation-associated increase in breast sodium iodide symporter activity has breast sodium iodide symporter activity has returned toreturned tonormal. .

Contraindication of 131-I Contraindication of 131-I therapytherapy

Breast feeding should not be Breast feeding should not be resumed after administration of 131I. resumed after administration of 131I. Breastfeeding can be safely Breastfeeding can be safely undertaken after future Pregnancies.undertaken after future Pregnancies.

Thank you