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NM By Myself > Thyroid NM > Flashcards

Thyroid NM Flashcards

1
Q

Thyroid location

A

Level of II and III tracheal rings
4-5 cm by 1.5-2 cm

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2
Q

Thyroid weight

A

6-20 g

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3
Q

Pyramidal lobe

A

At surgery 80%
Remnant of thyroglossal duct
Can hypertrophy after thyroid resection

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4
Q

C cells = parafollicular cells

A

From neural crest
1% of cell population
Secrete Calcitonin in response to Calcium elevation
Express somatostatin receptors, Calcitonin generated peptid, gastrin releasing peptide
Medullary thyroid carcinoma
Independent of TSH
Inable to concentrate iodine

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5
Q

Nontoxic multinodular goiter

A

Increased thyroid hormone production
Only nodules >1 cm should be evaluated or <1 cm if malignant nature
Non palpable nodules ==same risk of malignancy as US confirmed palpable same size
Areas of iodine def - - goiter
4-17% fulfill criteria of malignant change, but majority is not malignant
Therapy with I131 to avoid surgery
100 microCi per g of thyroid tissue

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6
Q

Toxic Adenoma = Plummer Disease

A

TSH receptor mutation - - receptor is always activated - - rest of gland rest
Treatment with I131 in the phase of דיכוי - - kill adenomatous cells
Fixed max activity 16 mCi
Risk - genetic, female

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7
Q

Graves disease

A

AB to TSH receptor
60-80% of thyrotoxicosis
High iodine intake
Women, 20-50

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8
Q

Graves disease US

A

Diffusely enlarged
Increased vascularity on Doppler - - thyroid inferno
vs Hashimoto (normal blood flow)

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9
Q

Graves disease treatment

A

Antithyroid drugs = PTU, methimazole - - bone marrow tox, liver tox, relapse
Radioiodine therapy
Thyroidectomy when large goiter - - bleeding, laryngeal edema, hypopara, damage of recurrent laryngeal nerve

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10
Q

Graves disease Radionuclide treatment

A

I131 - - progressive destruction by beta, highly effective, cure rate 100%
Radiation thyroiditis 1-2 weeks after - - pain in anterior cervical region, thyrotoxic crisis (cytolysis)
Persistent hyperthyroidism - - second dose 8-12 months later
Fixed dose 5, 10, 15 mCi
Can conceive 6 months after
Use steroids if Ophtalmopathy

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11
Q

Hashimoto thyroiditis

A

Most common autoimmune disease, endocrine disorder, cause of hypothyroidism
Chronic inflammation
Enlarged, lymphocytic infiltration of thyroid, hypothyroidism
Primary ass with autoimmune disease

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12
Q

Hashimoto thyroiditis US

A

Hypoecho
Ground glass
Pseudonodules = bag of marbles
Tiny cystic lesions = Swiss cheese - - 2-3 mm
Fibrosis - - septa

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13
Q

Other forms of thyroiditis

A

Infectious (not viral)
De Quervain = subacute - - viral - - release of preformed thyroid hormone - - hypoecho to one lobe or a portion of lobe - - painful, palpable
Autoimmune
Riedels = chronic sclerosing thyroiditis - - overgrowth of connective tissue
Postpartum
Amiodarone

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14
Q

Risk for malignancy US

A

Microcalcification
Irregular or microlobulated margins
Hypoecho
Taller-than-wide
Hypervascular

Combi of at least 2

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15
Q

Tc pert

A

Beta and gamma, 140 keV, 6h
Iodomimetic
Transport through Na/I symporter, no organification
Max accumulation 15-20 min after IV, plateau 30 min
Image not later than after 30 min
1-10 mCi
5 min or 100000-200000 counts
High dose, high count, no preparation, lower radiation exposure
Nursing in 12-24h

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16
Q

I123

A

Pure gamma, 159 keV, 13h
Higher specificity and persistence of accumulation due to organification
Higher resolution, better visualisation of retrosternal, children, in case of low thyroid uptake
3-4h after PO 100-400 microCi
10 min or 50000-100000 counts
Breast feeding in 48 h

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17
Q

I131

A

Beta and gamma 364 keV 8 days
Limited to uptake test, monitoring of DTC treatment, ectopic thyroid (retrosternal, lingual, struma ovarii), dosimetric pretreatment evaluation
High gamma–no sternal attenuation
24h after PO
10 min or >50000 counts

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18
Q

Pitfalls

A

Medication, CT contrast - - no uptake
Acute/subacute thyroiditis
Therapy with TSH suppressive doses of HRT
Hyperthyroidism (too much hormones)
Local contamination
Esophageal activity - - drink water

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19
Q

Nodules

A

Hot = hyperfunctioning - - almost never malignant
Cold = hypofunctioning - - 3-15% malignant
Indeterminate - - 3-15% malignant
Predictive value is low, esp if nodule <1 cm

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20
Q

RAIU

A

I131 PO 30-100 microCi
Measure at 4h and 24h
24h <20% - - no therapy

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21
Q

Radionuclide Therapy

A

I131, beta, 2.4 mm range in tissue
Cellular necrosis, inflammation, follicles destruction, fibrosis
Goal - to achieve hypothyroidism and reduce volume

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22
Q

Radionuclide therapy of benign
preparation

A

2 weeks low-iodine diet
4 weeks CeCT
3 months Amiodarone (definitive treatment for Amiodarone-induced thyrotoxicosis
3 weeks Lugol, topical iodine, Li (can block release from thyroid)

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23
Q

Radionuclide therapy and
Elderly, heart disease, systemic illness

A

Pretreatment with thionamides (PTU, MTMZL) to avoid radiation induced thyroiditis
Stop 3-5 days before, resume 2-3 days after to prevent thyroid storm
Beta blockers - no need to stop

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24
Q

Radionuclide therapy and pregnancy

A

Abs Contra
Fetal thyroid concentrates iodine by week 10-13
Stop breastfeeding and no resume

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25
Q

Radionuclide therapy and iodine sensitivity

A

Safe

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26
Q

Surgery benign

A

Tracheal narrowing <1 cm - - steroids
<5-6 mm - - surgery
80 g gland - - surgery

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27
Q

Induced hypothyroidism

A

2-3 months after radioiodide therapy
Levothyroxine as soon as TSH elevation is detected

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28
Q

Radioiodide therapy side effects

A

Inflammation with edema
Transitory hyperthyroidism - - steroids and beta blockers to prevent
Rare - - autoimmune thyroid disease 2-6 months after
Ophtalmopathy - - stop smoking, take steroids, start HRT after treatment

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29
Q

Efficacy of radioiodine treatment

A

Volume reduction to 30-40% within 1 year
Further reduction to 50-60% next year
Within 2-3 years hypothyroidism

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30
Q

Malignant thyroid disease

A

Thyroid nodule - - 4-5% of all thyroid nodules
Women
Sporadic/familial
Differentiated TC: papillary and follicular
Anaplastic TC = Stage IV
Medullary TC

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31
Q

Thyroid cancer M

A

Lung (PTC and young)
Bone (FTC and old)
Skin
Brain

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32
Q

Associated disease with Thyroid cancer

A

Gardner syndrome
Cowden syndrom - - FTC
RET oncogene
Hashimoto - - thyroid lymphoma

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33
Q

PET indication for thyroid cancer

A

DTC
Post Thyroidectomy
Eleveted Thyroglobulin
Negative I131 WBS
Tumor become iodine insensitive - - flip-flop - - FDG avid

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34
Q

ATC

A

Stage IV
IVB unresectable
Rapid grow - - big firm nodule, recently developed, 3-15 cm
Dysphonia
Dysphagia, dyspnea
30-40% regional LN and vocal cord paralysis
Surgery, chemo, EBRT
Very poor prognosis
Death from airway obstruction

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35
Q

Dedifferentiation of DTC

A

44% of ATC had previous or concurrent DTC

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36
Q

ATC mutations

A

BRAF V600E
RAS + BRAF - - resistance to vemurafenib

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37
Q

MTC

A

C-cells
Sporadic 75%
MEN2 - - 100% MTC, 50% pheo, 20-30% PHP
Hereditary - - RET mutation
Only 1% low diff - - do not produce Calcitonin - - marker
Well-diff

38
Q

Elevated Calcitonin

A

Renal failure
Autoimmune disease
Hyperpara
FTC
Net of Pancreas
Prostate ca
Lung ca

39
Q

Calcitonin in stimulation test with calcium, pentagastrin

A

Do not increase

40
Q

MTC treatment

A

Surgery
I131-MIBG
Y90- and Lu177 DOTA - TOC/NOC/TATE
Advanced/recurrent/metastatic - - TKI

41
Q

ATA guideline FNA

A

> 1 cm with high suspicion
1 cm with intermediate suspicion
1.5 cm with low suspicion
2 cm with very low suspicion (spongiform)

42
Q

Cytology

A

Thy1 - nondiagnostic aspirate
Thy2 - benign
Thy3 - cytology is not diagnostic
Thy4 - suspicious for malignant
Thy5 - malignant

43
Q

DTC NM

A

Espression of NIS gene reduced - - cold nodule - - can be benign nonfunctioning adenoma
Thyroid scan low specificity
FDG - - 4% increased focal uptake in thyroid - - incidentaloma - - 20% malignant

44
Q

ATC NM

A

High levels of GLUT1 and GLUT3– FDG the best
US, CT, MRI for defining local extent

45
Q

MTC NM

A

Neuroendocrine features
Express receptors for somatostatin - - MIBG image and therapy, FDOPA, radiolabeled somatostatin analogs therapy
FDG is suboptimal
Normal Calcitonin - - excellent response - - 10 year survival 100%
Useless imaging if Calcitonin <150 pg/mL

46
Q

Calcitonin >150 pg/mL

A

Neck US
LN recurrence most common

47
Q

Calcitonin >500 pg/mL

A

CT, MRI, PET

48
Q

Thyroid cancer T

A
49
Q

Thyroid cancer N

A

VI, VII
II-V
retropharyngeal

50
Q

Thyroid cancer M0

A

<55 years - - Stage I

51
Q

Thyroid cancer M1

A

<55 years - - Stage II

52
Q

Thyroid cancer surgery

A

FTC - - solitary nodule
PTC - multifocal growth - - total Thyroidectomy - - vocal cords palsy, permanent hypopara
PTC in single small nodule - - lobectomy + neck US
Central LN dissection

53
Q

Adjuvant ablation of postsurgical remnant

A

DTC - - to eliminate any residual, macroscopically normal thyroid left
TSH stimulation > 30 microIU/mL: stop L-thyroxine for 4-6 weeks or rhTSH 0.9 mg IM 2 days
I131 ablation 30-100 mCi
WBS 4-7 days after

54
Q

No benefit from ablation

A

Tumor <1.5 cm
LN negative
Unifocal microcarcinoma T1a

55
Q

Ablation preparation

A

2 weeks low-iodine diet
Stop L thyroxine for 4-6 weeks to TSH > 30 microIU/mL or rhTSH
Urine iodine content
Iodine / creatinine ratio <250 microg/g
NPO from midnight

56
Q

LN suspicious

A

FNA, Tg
<1 cm - - I131 therapy
Bigger - - surgery, radioiodine therapy

57
Q

Recurrent DTC

A

Poorly diff - - do not concentrate iod
FDG
TKI sorafenib and Lenvatinib

58
Q

Thyroid stunning

A

Prior diagnostic I131 - - non ablative up to 10 Gy - - reduced NIS expression in response to irradiation induced DNA damage - - 50% reduced ability to concentrate and store radioiodide - - reduced uptake
If I131 as preablation assessment - - no more than 2 mCi and ablation within 48-72 h

59
Q

I123 used as preablation assessment

A

Auger electrons
No stunning effect

60
Q

15% of DTC dedifferentiate

A

After several courses of I131
Retinoic acid
Selumetinib
Reinduce iodine uptake ability

61
Q

DTC +MTS, non iodine avid, rapidly grow

A

Only Doxorubicin

62
Q

Radioiodine ablation
Relative Contra

A

Bone marrow depression
Impaired pulmonary function - - significant accumulation
Intracranial DTC lesion - - oedema and compression
Functional deficit of salivary gland

63
Q

Radioiodine ablation
Side effects

A

Hypothyroidism 2-3 weeks after reintroduction of L-thyroxine
Nausea, gastric pain - - PPI
Sialoadenitis - - fluids and lemon juice
Loss or change of taste
Steroid to prevent radiation induced inflammation
Transient impairment of male gonadal function

64
Q

Second malignancy or leukemia

A

After repeat ablation + EBRT
>500 mCi

65
Q

Exposure to I131 affects outcome of pregnancy and offspring

A

No evidence

66
Q

Diffuse lung MTS

A

Radiation fibrosis if 150 mCi at short intervals <6 months
<80 mCi after 48h

67
Q

Levothyroxine treatment
PTC, FTC Post-op

A

To correct post op hypothyroidism
To suppress secretion of TSH
Young - - higher dose
T3 and T4 should be normal
No adverse effects on bone maturation, final height, pubertal development
Not to take the morning before blood test - - increase T4 by 25%
Aim - - TSH 0.1-0.5 microIU/mL

68
Q

Iodine daily requirement

A

150 microg
Bread, milk, seafood

69
Q

24h uptake <10-15%

A

Stimulation with recombinant human TSH
0.3 mg for MNG
0.9 mg for DTC

70
Q

Measure radioiodine dose for MNG

A

Thyroid mass * 3.7 MBq = initial activity
Uptake 30% - - thyroid mass *3.7 : 0.3

71
Q

Most common of all thyroid disease

A

MNG

72
Q

Most common cause of hyperthyroidism

A

Graves
Toxic Adenoma

73
Q

Graves disease risk

A

Infections
Iodine intake
Smoking
Psychic stress

74
Q

Graves disease lab

A

Elevated bilirubin, liver enzymes, ferritin
Microcytic anemia. Thrombocytopenia

75
Q

Thyroid scintigraphy
Indication

A

All cases of thyroid nodule
MNG if TSH is low
Ectopic thyroid
Retrosternal goiter

76
Q

C cells vs follicular cells

A

Junction of Upper 1/3 and lower 2/3, along central axis
Functional independence from TSH
Inability to concentrate and retain iodide
Production and secretion of Calcitonin

77
Q

Ablation
Indication

A

DTC moderate - high risk
No role - in ATC and poorly diff TC - - do not concentrate iodine

78
Q

Benefits from adjuvant ablation

A

Decrease recurrence
Early detection
Sensitive I131 WBS
Any subsequent I131 therapy will be more effective

79
Q

Ablation successful

A

90% if uptake in residue <2% - - residual mass <2g
2/3 if uptake in residue >2% - - residual mass >2g

80
Q

T3 three times per day

A

Tachycardia

81
Q

DTC follow up after primary treatment 6-12 m

A

Serum Tg - - 20-25% anti Tg autoAB interfere - - not reliable
Undetectable under L-thyroxine suppressive therapy - - confirm with TSH stimulation test - - can be avoided if basal Tg <0.1 ng/mL, but reserved for gray zone 0.1-1 ng/mL

Cutoff Tg 2 ng/mL (FDA 2.5 ng/mL)
I131 WBS
Neck US

82
Q

Bulkier recurrence limited to LN

A

Surgery

83
Q

No uptake on post treatment WBS

A

Stop treatment with I131

84
Q

Uptake %

A

Graves 50-80%
MNG 20-30%
Normal 4h 4-15%
Normal 24h 10-30%

85
Q

Tc pert high radiation dose to thyroid

A

Beta
High gamma
Long T1/2
Contaminants I124 and I125 increase radiation dose

86
Q

Cold nodule

A

10-30% risk of malignancy

87
Q

Nodule hot on Tc pert, but cold on I123

A

2-3%

88
Q

Uptake dd thyroiditis vs Graves

A

Thyroiditis - - abnormally low
Graves - - abnormally high

89
Q

Thyroid whole body scan biodistribution

A

Stomach, urinary clearance
Remnant thyroid or MTS

90
Q

1 weeks after administration of 100 mCi I131

A

Residual tissue in thyroid bed
Local MTS under ablation
Physiological liver uptake
No uptake in stomach and small bowel - - >48h

91
Q

FDG thyroid cancer

A

ATC
MTC
Hurtle cell

92
Q

FDG diffuse bilateral uptake

A

Thyroiditis
Graves
Hypothyroidism

NM By Myself (25 decks)

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