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MBBS II ERS > L16 - Radiology and Radioactive iodine therapy > Flashcards

L16 - Radiology and Radioactive iodine therapy Flashcards

1
Q

List the imaging techniques to confirm enlargement of thyroid gland?

A

Ultrasound

CT

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2
Q

List the imaging technique for thyroid function?

A

Radionucleotide scan

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3
Q

List the imaging techniques to characterize nodules and masses?

A

Ultrasound

Radionucleotide

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4
Q

List imaging techniques for evaluating thyroid carcinoma?

A

Evaluate local disease: US, CT, MRI

Detect recurrence after thyroidectomy / treatment: US, CT, MRI, radionuclide scan

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5
Q

Limitation of CXR for imaging thyroid?

A

Cannot evaluate soft tissue structure, evaluate extent of local invasion/ compression, characterize thyroid lesion

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6
Q

Advantages of using ultrasound for thyroid imaging?

A

No radiation

High frequency probe good for superficial structure evaluation: characterize nodule, vascularity

Excellent spatial resolution, sensitive to tiny nodules

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7
Q

List 5 physical features pf thyroid nodules that may be identified by ultrasound imaging?

A
  1. Solid vs. cystic (internal necrosis)
  2. Vascularity (colour doppler)
  3. Calcification
  4. size and number of nodules
  5. Margin of nodules
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8
Q

Solid vs cystic thyroid nodule: which is more likely malignant?

A

Purely cystic: very rarely malignant

Purely solid: 23% malignant

Mixed solid & cystic: 14% malignant

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9
Q

Thyroid Ultrasound shows Rung-down artifacts: bright dots with comet tails. What is indicated?

A

inspissated colloid calcifications (colloid aggregates)

= benign cyst

Unlike microcalcification which indicated malignancy

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10
Q

How does vascularity of thyroid lesion indicate malignancy?

A

Complete avascular= unlikely malignant

Intrinsic/intranodular vascularity: 69-74% malignant (e.g. papillary carcinoma)

Perinodular vascularity: 22% malignant

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11
Q

Is thyroid nodule calcification a sign of malignancy?

A

Nonspecific – both in benign and malignant conditions

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12
Q

Define 3 types of thyroid nodule calcification and their asso. neoplasm?

A

Microcalcifications (punctate calcification, psammoma bodies)
 Common in papillary carcinoma (also in follicular, anaplastic carcinomas)
 Benign: follicular adenoma, Hashimoto thyroiditis

Coarse calcifications: common in medullary carcinoma

Dystrophic calcifications: multinodular goiter

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13
Q

How does the margin of thyroid nodules indicate malignancy?

A

Irregular margin = likely malignant

e.g. anaplastic carcinoma&raquo_space; local invasion beyond capsuleinto surrounding tissues (e.g. to vertebral muscle, vertebral body, displace carotid artery)

Well-defined = follicular adenoma

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14
Q

How does the size of thyroid nodule indicate malignancy?

A

> 4cm = likely malignant

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15
Q

How does the number of thyroid nodules indicate malignancy?

A

Non-specific, cant use to indicate malignancy

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16
Q

Define the echogenic nature and vascularity of thyroid nodules in Grave’s?

A

 Diffuse enlargement of thyroid=homogenously hypoechoic (very dark)

 Increase vascularity (thyroid inferno)

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17
Q

List 3 clinical uses for ultrasound related to thyroid pathologies?

A
  1. Characterize nodule
  2. Assess neck for lymph node metastasis in thyroid cancer
  3. Guides fine needle aspiration (FNA)/biopsy for cytology
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18
Q

Major limitation of Fine needle aspiration cytology in thyroid cancer ddx?

A

Cannot distinguish between:
Follicular adenoma and Follicular carcinoma

Requires histology: Rely on capsular or venous invasion

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19
Q

What is the most sensitive and specific imaging for ddx benign vs malignant thyroid nodules?

A

Ultrasound + FNAC (fine needle aspiration cytology)

20
Q

Indication for CT and MRI in thyroid diseases?

A

CANCER
Cross-sectional anatomy: intrathoracic extension of goiter

  • Post-surgery or radiology: surverillance*** for recurrence of cancer
  • Evaluate local, regional and distant metastasis***
21
Q

Compare the function of 99m-Tc pertechetate vs Iodide scan for thyroid?

A

99m-Tc pertechnetate: Trapped by thyroid tissue but not incorporated into thyroglobulin for organification = NO FUNCTION CHECK

Iodide = Trapped and organified = FUNCTION CHECK

22
Q

Which iodide isotopes are used for thyroid scans?

A

I-123, I-124

I-131 = more for treatment, notoriously high false-negative rate

23
Q

What is indicated by “hot” and “cold” nodules seen on radionucleotide scans of thyroid??

A

Hot = increase uptake, Cold = no uptake
Shows ectopic thyroid gland + evaluate function

Hot: Hyperthyroidism, Iodine deficiency, functional adenoma: EXCLUDE CANCER

Cold: Hypothyroid/ adenomas/thyroiditis: COLD= CANCER, mostly benign, 20% malignant

24
Q

Radionucleotide scans are sufficient for dx of thyroid cancer. T or F?

A

Always require needle biopsy/aspiration

25
Q

Multinodular goiter produces “hot nodules” T or F?

A

False

Mixture of hot and cold

26
Q

3 clinical uses for radionucleotide scans for thyroid diseases?

A
  • Assess metabolic function: Hot or Cold
  • Shows position of ectopic thyroid glands
  • Surveillance after treatment with whole-body I-131 scan
27
Q

Increased thyroglobulin always shows up on 131-I scans. T or F?

A

False

High rate of false negative on 131-I

Need to use 99mTc-MIBI or 18F-FDG PET/CT scans for higher specificity and sensitivity

28
Q

List the iodine isotopes for thyroid treatment

A

I-131

29
Q

List the iodine isotopes for prostate cancer imaging and treatment

A

I-125

30
Q

List the iodine isotopes for thyroid imaging

A

I-123 I-124

31
Q

Describe the radiation emitted by I-131 and how it’s used for thyroid diseases?

A

I-131 trapped inside follicles

destructive beta- particles = destroy parenchymal cells w/o damage to surrounding tissue

Gamma-radiation detected externally for thyroid function monitoring

32
Q

Which thyroid diseases are treated by I-131?

A
  • benign thyroid disease/ hyperthyroidism: GRAVE’S ***
  • Toxic multinodular goiter ***and thyroiditis
  • well-differentiated thyroid cancer (e.g. papillary and follicular)
  • Iodine-induced hyperthyroidism (amiodarone)
  • Ectopic/ metastatic thyroid cancer
33
Q

Admin of I-131?

A

orally, sodium iodide, capsule

34
Q

Limitation of I-131 in identifying metastasis? think about which tissue take up

A

Uptake by Salivary gland, esophagus, thymus, breast, Liver, stomach, colon, bladder

> > easily misinterpret as metastasis

35
Q

C/O of I-131 therapy for hyperthyroidism?

A
  • Absolute contraindication: pregnancy and lactation
  • Relative contraindication: children and adolescents

Worsening Grave’s ophthalmopathy

36
Q

Indications for using I-131 to treat hyperthyroidism?

A

Poor compliance, ADR and recurrence after anti-thyroid drugs

Patients with CVS diseases : Cardiac arrhythmias, heart failure

thyrotoxic periodic paralysis

37
Q

ADR and long-term safety of I-131/ Radioactive iodine?

A

1) Mild, well-tolerated: Neck swelling, painful swallowing
2) Nausea, GI discomfort
3) High risk of HYPOthyroidism after one year
4) Rare: radiation cystitis, gastritis, fibrosis
5) Very rare: Bone marrow suppression, anaplastic anaemia, leukemia

No long-term effect on fertility, cancer, congential malformations

38
Q

Treatment for hypothyroidism caused by I-131?

A

regular serum thyroid function test and thyroxine replacement

39
Q

List advantages of I-131 therapy for thyroid diseases?

A
  • Cost effective
  • Few adverse effects
  • Out-patient therapy
  • Reduction in goiter size
40
Q

List disadvantages of I-131 therapy for thyroid diseases?

A
  • Radiation exposure
  • Risk of exacerbation of ophthalmopathy
  • Need to delay pregnancy and avoid breastfeeding
  • Radiation thyroiditis: 10%
41
Q

Treatment of Differentiated Thyroid Cancer ?

A

Total thyrodectomy/ lobectomy +/- radioactive iodine

I-131:

  • for eradication of residual cells
  • reduce risk of metastasis
  • increase sensitivity of serum thyroglobulin and I-131 WBS for surveillance
42
Q

Anti-thyroid medication can be taken concurrently with I-131 therapy. T or F?

A

False

Stop anti-thyroid medications 4-14 days before RAI (hyperthyroidism)

43
Q

Precautions and preparations before starting I-131 therapy?

A
  • No breastfeeding and practice contraception for 4 weeks before (female)
  • Low iodine diet for 2 weeks: cut seafood, dairy, soy
  • Stop all T4/T3 therapy or switch to recombinant human TSH: increase radioactive iodine uptake by tumour cells
44
Q

Which patients need recombinant human TSH before I-131 therapy?

A
  • Hypopituitarism
  • Severe ischemic heart disease
  • psychiatric disturbance
  • Functional metastasis causing TSH suppression
45
Q

Precautions after I-131 therapy?

A
  • Distant/ social isolation (radioactive)
  • No pregnancy, breastfeeding, fathering for a year
  • No iodine food, meds
46
Q

Indication for I-131 whole body scan?

A
  • Screen for residual thyroid uptake or distant metastasis
47
Q

Summarize all the long-term follow-ups after I-131 therapy?

A

Regular monitoring with serum thyroglobulin

131I-whole body scan 6-12 months after:detect any relapse/metastasis

thyroxine (TSH suppression therapy) to keep TSH below the lower limit

MBBS II ERS (37 decks)

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