Adrenal & parathyroid

ENDOCRINE SYSTEM:ADRENAL

NMT 431

1UAB

Adrenal Imaging

Clinical Indications

Radiopharmaceutical used

Dosage & Administration

Technique

The Normal Scan

The Abnormal Scan

Artifacts & Pitfalls

Anatomy / Physiology

2UAB

Anatomy• Located bilaterally on

superior poles of both kidneys

• Each gland weighs only 6-7 grams

• Each gland consists of two parts:– Cortex (outer layer)– Medulla (inner layer)


3UAB

Cortex (outer layer) produces steroid hormones:AldosteroneCortisolAndrogens

Medulla (inner layer) produces catecholamines:Epinephrine (adrenaline)NorepinephrineDopamine


dopamine

4UAB

Hypothalamus - Pituitary – Adrenal cortex- feedback loop

• Hypothalamus synthesize and secrete corticotropin-releasing hormone (CRH) and vasopressin

• CRH and vasopressin stimulate the secretion of adrenocorticotropic hormone (ACTH) from anterior pituitary

• In response to stimulation by ACTH the adrenal cortices produce cortisol

• Cortisol in turn act back on the hypothalamus and pituitary (to suppress CRH and ACTH production) in a negative feedback cycle.

5UAB

Adrenal Cortex:

• Adrenal cortical pathology causing excessive production of one or more steroid hormones:

Hyperplasia (a proliferation of normal cells)Adenoma (a benign tumor)Carcinoma (a malignant tumor)


6UAB

http://upload.wikimedia.org/wikipedia/en/7/76/Adrenal_gland_%28cortex%29.JPG

Adrenal Cortex:• Adrenal cortical imaging indicated when source of

overproduction of steroid hormones is unknown in the presence of the following symptoms:– Increased level of cortisol (Cushing’s syndrome)– Increased level of aldosterone– Increased virilization

• Rule out adenoma; differentiate adenoma from hyperplasia


7UAB

Adrenal Medulla

Clinical indication: rule out pheochromocytoma


• Pheochromocytoma: a benign or malignant tumor of the adrenal medulla that secretes increased levels of epinephrine or norepinephrine

• Symptoms include unexplained hypertension, elevated levels of catecholamines, epinephrine, norepinephrine

8UAB

http://upload.wikimedia.org/wikipedia/en/2/21/Adrenal_gland_%28medulla%29.JPG

Adrenal Cortex: Radiopharmaceutical

• I-131 cholesterol (6-beta-iodomethyl-19-norcholesterol) (I-131 NP-59)

• Cholesterol is a precursor of steroid hormones; radiolabeled cholesterol when administered IV is incorporated into newly synthesized steroid hormones

• Investigational drug


9UAB

Adrenal Medulla: Radiopharmaceutical

• I-131 iobenguane (MIBG = methyliodobenzylguanidine)

• MIBG is structurally similar to norepinephrine


10UAB

Adrenal Cortex: Clinical Procedure

1) Patient preparation:

Dexamethasone (synthetic cortisol) may be given to suppress function of normal ACTH dependent adrenal tissue (by negative feedback) for approximately 4 days before receiving the tracer

Lugol’s solution (supersaturated solution of potassium iodide) to prevent uptake of free iodine by thyroid gland for several days before receiving the tracer

Signed consent required – investigational radiopharmaceutical


Technique

11UAB

Adrenal Cortex: Clinical Procedure

2) IV administration of I-131 cholesterol: 0.5-1 mCi

3) Image 2-4 days following tracer administration

Posterior abdominal view


Technique

12UAB

Adrenal Medulla: Clinical Procedure1) Patient preparation:

Lugol’s solution several days prior to tracer administration

2) IV administration of I-131 MIBG: ≈ 0.5 mCi

3) Image anterior and posterior head, thorax and abdomen 24-48 hrs post tracer administration; later images as indicated/needed


Technique

13UAB

Adrenal CortexNormal tracer biodistribution:

- liver

- tracer excretion into bile then bowel

- normal adrenal tissue not visualized (if pretreated with

Dexamethasone)

- Right adrenal is slightly superior to the left

The Normal Scan

(without dexamethasone suppression)

Principles & Practice of Nuclear Medicine – Early & Sodee

14UAB

Adrenal Cortex

Abnormal:

- increased tracer uptake in abnormal gland

The Abnormal Scan

NP-59 uptake in adrenal adenoma

Endocrine Surgery - By Schwartz, Pertsemlidis, Gagner

15UAB

Adrenal Medulla:

Normal tracer biodistribution:

heart, liver, spleen, salivary glands and bladder; no adrenal medulla uptake or only faintly visualized at 24 hrs

The Normal Scan

Principles & Practice of Nuclear Medicine – Early & Sodee16UAB

Adrenal Medulla:Abnormal:

- intense uptake in tumor - significant uptake persists

in later images

- in the case of a malignant tumor, uptake may be seen in liver, bone, lymph nodes, heart, lungs, etc. (metastases from primary tumor)

The Abnormal Scan

PheochromocytomaMIR teaching file

MIR teaching file

Metastatic pheochromocytoma17UAB

• Interfering Gall bladder activity (may image post fatty meal)

• Colonic activity (cathartics may be used)

• Many drugs interfere or promote MIBG uptake (careful medication hx needed; ideally, drugs withheld 2-3 weeks before test)


MIBG uptake in the muscles due to drug interference; Study was non-diagnostic

MIR teaching file

18UAB

19

Dexamethasone pre-treatment is done in order to:

a. stimulate normal adrenal tissueb. stimulate abnormal adrenal tissue c. inhibit normal adrenal tissued. inhibit abnormal adrenal tissue

UAB

Lugol’s solution is given before adrenal medulla imaging in order to block:

a. adrenal cortexb. adrenal medullac. thyroidd. parathyroid

20UAB

ENDOCRINE SYSTEM:PARATHYROID

NMT 431

21UAB

Parathyroid Imaging




Technique

The Normal Scan

The Abnormal Scan



22UAB

Anatomy

• Located beside, beneath, or within thyroid gland tissue

• Other locations: within thymus gland or mediastinum or among the great vessels


Some common ectopic parathyroid sites

Wikipedia

23UAB

Parathyroid Hormone (PTH)• Regulates calcium &

phosphate metabolism

– Bone: stimulates osteoclastic activity to increase bone resorption to make calcium & phosphorous available to other tissue

– Kidney: decreases

excretion of Ca & increases excretion of phosphorous

– GI tract: enhances calcium & phosphate absorption from bowel

Linus Pauling Institute, Oregon State University


24UAB

Thyroid – Parathyroid – feedback for calcium homeostasis

• Synthesis/secretion regulated by plasma Ca++ level by negative feedback mechanism


25UAB

Pathophysiology

• Hypoparathyroidism– Failure to respond to

lowered serum calcium levels resulting in hypocalcemia (muscle spasm, cardiac arrhythmia)


Hypoparathyroidism

26UAB

Pathophysiology

• Hyperparathyroidism– Primary

hyperparathyroidism: increased synthesis and release of PTH

– Major symptoms: kidney stones, osteoporosis, neurological disorders & abdominal pain)


Symptoms of

hyperparathyroidism

Adam, Inc.

27UAB

1) Localize hyperfunctioning parathyroid tissue (adenoma or hyperplasia) in primary hyperparathyroidism. May help surgeon identify lesion.

2) Localize hyperfunctioning parathyroid tissue (usually adenoma) in patients with persistent or recurrent disease


28UAB

Dual tracer technique

Tc-99m pertechnetate Tc-99m sestamibi (99mTc-MIBI)


Single tracer technique

Tc-99m sestamibi (99mTc-MIBI)

29UAB

Clinical Procedure1) ID patient; verify physician’s order; review clinical

indication for imaging

2) Explain procedure to patient; obtain relevant medical history


Technique

30UAB

Relevant Medical History

• Lab results: serum calcium, PTH levels; urine calcium level

• History of thyroid disease• Results of other imaging procedures• Physical exam findings (neck palpation)


Technique

31UAB

Clinical Procedure (cont’d)

3) Patient preparation - No special preparation - Assess patient’s ability to lie still

4) Administer radiopharmaceutical


Technique

32UAB

Clinical Procedure (cont’d)5a) Injection & Imaging – Dual tracer Subtraction technique

Patient must remain in position for all images Tc-99m pertechnetate: 4-5 mCi IV Position patient as for thyroid imaging; image neck

20-30 min later, Tc-99m sestamibi (MIBI): 20-25 mCi IV 30 min after sestamibi injection, image neck

Image mediastinum to rule out ectopic tissue


Technique

Subtraction technique

(Sestamibi thyroid image) – (99mTc-Pertechnetate image) = areas of abnormal tracer accumulation in parathyroid

33UAB

Clinical Procedure (cont’d)

5b) Injection & Imaging – Single tracer technique Patient injected and positioned as for thyroid imaging

Image neck at 30 min and 90-120 min

Image mediastinum to rule out ectopic tissue


Technique

34UAB

The Normal Scan

Radiographics 19 (3): 601. (1999)

(upper left) 99mTc pertechnetate image

(upper right) the early Tc- sestamibi image

(Lower left) Computer-subtraction image

Dual tracer Subtraction Technique

Single tracer delayed washout method

THE JOURNAL OF NUCLEAR MEDICINE; Vol. 38 No.6 June 1997

35UAB

The Abnormal Scan

Patient with a parathyroid carcinoma involving the left

upper thyroid gland

(Upper left) Technetium-99m-pertechnetate image(upper right) early Tc-sestamibi image

(lower left) computer-subtraction image

THE JOURNAL OF NUCLEAR MEDICINE; Vol. 38 No.6 June 1997

Dual tracer Subtraction Technique

36UAB

20 min 2 hrs

MIBI SPECT/CT

Mediastinal parathyroid adenoma

Single tracer delayed washout method

MIR teaching file

med.harvard.edu

The Abnormal Scan

SNM 2010 Image of the Year

99mTc-Sestamibi

37UAB

Sources of Error• Patient motion• Image misregistration• Small adenomas/hyperplastic/ectopic glands may be

difficult to detect• Thyroid adenomas/carcinomas may be

indistinguishable from parathyroid adenomas


38UAB

Education

Adrenal & parathyroid