FINALS-CLINICAL Flashcards by Unknown Unknown

Hyperthyroidism diseases

-Graves disease,
-toxic adenoma,
-toxic multinodular goiter

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I-131 Therapy is used for what diseases

-Hyperthyroidism: Graves disease, toxic adenoma, toxic multinodular goiter

-Thyroid cancer: Post-thyroidectomy remnant ablation, residual/metastatic disease

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During I-131 Low-iodine diet: Used at least ? prior I-131 therapy for thyroid cancer

2 weeks

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I-131 therapy avoid the following:

-iodized salt,
-dairy products,
-seafood,
-seaweed,
-sea kelp,
-canned fruit or vegetables,
-chocolate,
-commercially made bread,
-white flour,
-FDC red dye #3,
-multivitamins with iodine

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I-131 Outpatient treatment indicated for patients receiving ? I-131

< 33 mC1 (1.22 GBq)

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Approved for higher dose I-131, if certain criteria met

> Release calculations: Maximum bystander dose ? dose rate
at 1 meter = ? mrem/h for dose
< ? mCi

5 mSv (500 mrem),
48.5 mrem/h
< 221 mCi

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For I-131
Radiation safety precautions: Typical (for administered activity
> ? mCi, dose, patient
specific calculations of exact precautions are required)
> Not required for doses < ?mCi

> 33 mCi
7 mCi

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First ? days: Reduce radiation dose to others by containing bodily waste

2-3 days

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Maintain? distance from infants/children, women who may be pregnant, adults

6-foot

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synonyms of I-131 HYPERTHYROID THERAPY

Radioiodine (RAI) therapy
Thyroid ablation

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: ↑ Circulating thyroid hormone (thyrotoxicosis) from diseases that increase hormone production/release

Hyperthyroidism

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Targeted thyroid follicular cell destruction for hyperthyroidism caused by Graves disease, autonomous nodules, nodular goiters

I-131 therapy:

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(diffuse toxic goiter)

Graves disease

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> Responds well to RAI, favored therapy
Diffusely increased activity with radioiodine uptake (RAIU) usually very high (>50-80%)

Graves disease (diffuse toxic goiter

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Graves disease Diffusely increased activity with radioiodine uptake (RAIU) usually very high (>?-?%)

> 50-80%

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> May be asymptomatic requiring no therapy or cause hyperthyroidism (toxic nodular goiter)
Thyroid scan: Multiple hot and/or cold nodules, RAIU varies from normal to moderately elevated
Subclinical hyperthyroidism (↓ TSH, normal T4) may require treatment where risk of side effects high (e.g.,elderly)

Multinodular goiter (MNG)

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> Autonomously hyperfunctioning adenomatous tumor
Scan shows one hot nodule suppressing remaining thyroid, RAIU normal to ↑

Toxic adenoma (TA)

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Contraindications of I-131

Pregnancy
Breastfeeding
Low RAIU thyrotoxicosis etiologies
Hashitoxicosis

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> I-131 crosses placenta with fetal thyroid concentration beginning
?-?th gestational week

10-12th

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Low RAIU thyrotoxicosis etiologies that are not treated with I-131:

> Subacute thyroiditis:
Drug-induced thyrotoxicosis

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Breastfeeding

> Breastfeeding patients must be counseled to terminate breastfeeding and wait
? before RAI to avoid radiation dose to breasts

2 months

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: Self-limited post-inflammatory process may be difficult to
diagnose clinically but is differentiated by ↓↓ RAIU

Subacute thyroiditis

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Different diseases that are Drug-induced thyrotoxicosis

-Thyroiditis factitia:
-Amiodarone:
-Iodine-induced hyperthyroidism:

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Prescribed or surreptitiously ingested thyroid
hormone → clinical hyperthyroidism but ↓↓ RAIU

Thyroiditis factitia

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: May cause hyperthyroidism (up to 10%) lasting months

Amiodarone

: Rare hyperthyroidism in early Hashimoto disease > Diagnosis usually made clinically; ↑thyroid antibodies

Hashitoxicosis

: Usually due to IV contrast in patients with MNG, endemic goiter

Iodine-induced hyperthyroidism:

Things to Check before I-131 ■ Suppressed TSH < ? mU/L most sensitive test, ↑ thyroid hormone (T4 and T3) varies > Consider low iodine diet ? dsy to ? week not commonly required

0.1 mU/L 10 days - 2 weeks;

■RAIU normal values vary by lab: 4-6 hr - ?%, and 24 hr ?%

5-15% 10-30%

for I-131 therapy ■ Release patients: Dose rate at 1 m ≤ ? mSv/hr (? mrem/hr) or activity ≤ ? GBq (? mCi)

0.07 mSv/hr (7 mrem/hr) 1.2 GBq (33 mCi)

For I-131 therapy ■ Written order includes patient name, dosage, and route of administration, dated and signed by AU for doses > ? μCi (? MBq)

> 30 μCi (1.1MBq)

During I-131 Do not use medications that decrease I-131 uptake ■ Iodinated contrast: ? weeks after CT, up to ? weeks others ■ Iodine-containing supplements (kelp), cough medications: ? weeks ■ Thyroid hormone replacement: ?-? weeks T4; ?-? weeks T3

2-4 weeks 8 week 1-2 weeks 4-6 weeks 2-3 weeks

for I-131 do not take Antithyroid thioamide drugs: -Propylthiouracil (PTU) ?-? days; -methimazole ?-? days

3-5 days; 5-7 days

Dose determination of I-131 therapy Depends on

-diagnosis, -desired outcome, -gland size, -RAIU

Components of Patient Consent in I-131 therapy

 Written informed consent required prior to I-131 therapy  Both verbal and written radiation safety instructions  must be given List I-131 side effects  List physician emergency phone number  Provide written document verifying radioactive therapy in case of detection by monitoring devices at secure institutions during travel/work

Calculated doses to deliver ?-?μCi (?-?MBq) per gram thyroid may be used but have no proven benefit

80-200 μCi (2.96-7.4 MBq)

How to calculate dose (?% uptake/100)

(Desired dose x gland weight) divided by RAIU fraction (9% uptake/100)

■ Use ? doses for larger glands, low uptake, and Graves with rapid I-131 turnover (high RAIU at 4 hrs diminishing by 24 hrs)

higher dose

■ Generally, responds well to I-131 ■ Empiric 5-12 mCi (185-444 MBq) doses, euthyroid state possible ■ Attempts to achieve euthyroid state may be futile as hypothyroidism typical eventually from autoimmune gland destruction ■ High doses of 15 mCi (555 MBq) result in more rapid hypothyroidism,

Graves disease

> Graves disease ■ Generally, responds well to I-131 ■ Empiric ?-? mCi (?-? MBq) doses, euthyroid state possible ■ Attempts to achieve euthyroid state may be futile as hypothyroidism typical eventually from autoimmune gland destruction ■ High doses of ? mCi (? MBq) result in more rapid hypothyroidism,

5-12 mCi (185-444 MBq) 15 mCi (555 MBq)

■ Require higher doses than Graves, typically by more than 50% ■ Empiric doses of 20-29 mCi (740-1073 MBq) or more are routine ■ Calculated doses use upper end of range, 200 μCi (7.4 MBq)/gram ■ Reports of recombinant TSH (rhTSH) increasing I-131 effectiveness

> Toxic adenomas, nodular goiters

Toxic adenomas, nodular goiters ■ Require higher doses than Graves, typically by more than ?% ■ Empiric doses of ?-? mCi (?-? MBq) or more are routine ■ Calculated doses use upper end of range, ? μCi (?MBq)/gram ■ Reports of recombinant TSH (rhTSH) increasing I-131 effectiveness

50% 20-29 mCi (740-1073 MBq) 200 μCi (7.4 MBq)/gram

Expected Outcome of I-131 therapy  Response to I-131 occurs slowly as stores of hormone are depleted with some response by ?-? weeks, maximal effect by ?-?months Approximately 100% of patients require I-131 retreatment > 2nd dose usually higher (?-?%) and can be repeated at ?-? months

2-4 weeks 3-4 months (20-30%) 3-6 months

Monitor condition: Side effects more common in large glands with ?

high RAIU

Often used for transient ↑ hormone release without altering I-131 effects

> β-blocker (propranolol):

for minor neck tenderness

> Non-steroidal agents (acetaminophen)

For first signs worsening neck pain or possible thyroid storm

> Steroids (dexamethasone):

> May restart PTU/methimazole ?-? days after I-131 therapy as relief is slow > Plan continuous surveillance for ?

2-3 days hypothyroidism

Most feared complication(s) of I-131 HYPERTHYROID THERAPY

> Fetal I-131 exposure resulting in fetal demise or neonatal hypothyroidism > Thyroid storm frequently fatal medical emergency ■ Presents with fever, irritability, vomiting, diarrhea, and hypotension

complications of I-131 hyperthyroid are Treated aggressively with:

fluids, ẞ-blockers, and steroids

■ Painful neck and/or transient increase hyperthyroid symptoms from hormone release and autoimmune factors

Radiation thyroiditis

Other complications of I-131 THERAPY

> Nausea and vomiting > Radiation thyroiditis > Hypothyroidism > Worsening Graves exophthalmos rare, > Cancer

? is the most frequent complication, may occur after several months or many years -requires life-long thyroid hormone replacement -Incidence in 1st year correlates with I-131 dose but occurs in majority of patients after 10-25 yrs regardless of dose

Hypothyroidism

> Worsening Graves exophthalmos rare, treated with ?

steroids

Incidence in 1st year correlates with I-131 dose but occurs in majority of patients after ?-?yrs regardless of dose

10-25 yrs

> Cancer ■ No increased risk of secondary cancers, including ? or ?, at doses used for hyperthyroidism ■ Occasional thyroid cancer case reports suggest an association with the underlying thyroid disease/nodules rather than I-131 exposure

thyroid cancer or leukemia

(TSH)

Serum thyrotropin

RAI

RADIOACTIVE IODINE

Papillary, follicular, Hürthle cell, mixed thyroid cancer, anaplastic > Under 45 years old ■ Stage I: ? ■ Stage II: ?

■ Stage I: Any tumor size, nodes +/-, no metastases ■ Stage II: Any tumor size, nodes +/-, + metastases

Papillary, follicular, Hürthle cell, mixed thyroid cancer, anaplastic > above 45 years old Stage ? :Tumor < 2 cm (limited to thyroid), - nodes, no metastases

Stage I

Papillary, follicular, Hürthle cell, mixed thyroid cancer, anaplastic > above 45 years old Stage ? :Tumor 2-4 cm (limited to thyroid), - nodes, no metastases

STAGE II

Papillary, follicular, Hürthle cell, mixed thyroid cancer, anaplastic > above 45 years old Stage ? :Tumor size> 4 cm with no or minimal extrathyroidal extension or + level VI nodes, no metastases

STAGE III

Papillary, follicular, Hürthle cell, mixed thyroid cancer, anaplastic > above 45 years old Stage ? :Extrathyroidal extension of differentiated tumor, surgically res ectable anaplastic tumor; + level VI, cervical, superior mediastinal nodes; no metastases

STAGE IV A

Papillary, follicular, Hürthle cell, mixed thyroid cancer, anaplastic > above 45 years old Stage ? : Unresectable tumor, +/- nodes, no metastases

STAGE IV B

Papillary, follicular, Hürthle cell, mixed thyroid cancer, anaplastic > above 45 years old Stage ? : C: + Metastases

STAGE IV C

> Not amenable to RAI therapy

Anaplastic, medullary

RAI treatment with I-131 > High-energy beta emissions travel ? mm, ablate thyroid tissue > Non-thyroid tissues minimally affected > Whole-body scan (WBS) scan can be done using ?

0.8 mm gamma emissions

Indications of I-131 THYROID CANCER THERAPY

 Post-thyroidectomy remnant ablation  Recurrent or residual disease

> RAI ablation recommended for ■ Select stage I patients with:

-multifocal disease, -nodal metastases, -extrathyroidal, -vascular invasion, or more aggressive histology)-

> RAI ablation recommended for

■ Select stage I patients (multifocal disease, nodal metastases, extrathyroidal, vascular invasion, or more aggressive histology) ■ All patients < 45 yrs old with stage II ■ Most patients> 45 yrs old with stage II ■ Stage III/IV disease

> If ? only, RAI ablation not recommended

lobectomy

Dose of I-131 THYROID CANCER THERAPY: Usually ?-? mCi, depending on surgical pathological findings

100-150 mCi,

Recurrent or residual disease > Detected on physical exam, WBS, ultrasound, CT, MR > Regional lymphadenopathy > Distant metastases (lungs, bones) > Elevated serum thyroglobulin with unknown anatomic site > Higher dose RAI: ? ■RAI alone or as adjunct to surgery

150-200 mCi

Contraindications of THYROID CANCER THERAPY

 Pregnancy  Breastfeeding within 2 months of treatment

Things to Check THYROID CANCER THERAPY

> Pre-therapy WBS > RAI thyroid uptake measurement > Patient follows low-iodine diet for 1-2 weeks > Thyroid hormone withdrawal or recombinant human TSH (rhTSH) stimulation > Laboratory tests > Recent iodine load > Inpatient versus outpatient therapy

Pre-therapy WBS ■? risk patients: WBS may not be needed, controversial ■ ? risk patients: Evaluate for distant metastases, locoregional disease

Low to moderate risk High risk

■ Recurrence: ?to detect sites of disease, confirm disease is RAI- avid

WBS WHOLE BODY SCAN

Things to check in thyroid cancer therapy > RAI thyroid uptake measurement ■ ≥ ?% uptake in remnant → lower therapy dose > Patient follows low-iodine diet for ?-? weeks > Thyroid hormone withdrawal or ? stimulation

59% 1-2 weeks recombinant human TSH (rhTSH)

> Laboratory tests of thyroid cancer therapy ■ TSH >? mU/L if thyroid hormone withdrawal ■ Negative ? ■ Complete ? if previously treated with high doses of I-131

30 mU/L pregnancy test blood count

To check in thyroid cancer therapy > Recent iodine load ■ Contrast for angiogram, CT; high dietary iodine (e.g., sea kelp supplements) ■ Urine iodine level, should be < ? microgram/L for RAI treatment

< 200 microgram/L

thyroid cancer therapy > Inpatient versus outpatient therapy ■ Nuclear Regulatory Commission guidelines: Can be treated as outpatient if total effective dose equivalent to any other individual does not exceed ? mSv ■Most treated as ? ■ Inpatient treatment for very high doses, contraindications to early release (e.g., unable to follow radiation safety precautions) 

5.0 mSv outpatients

> Thyroid hormone withdrawal pre-WBS, therapy ■ Off levothyroxine for ?-? weeks (half-life of T4 is ? weeks) ■ Alternatively give ? (shorter T1⁄2) for 2-4 weeks, then triiodothyronine withdrawal for 2 weeks

4-6 weeks 2 weeks triiodothyronine

■ Currently FDA approved for scan, not therapy ■ Used prior to RAI therapy in patients with contraindication to withdrawal (e.g., psychiatric illness, elderly) ■ Avoids hypothyroid symptoms as patient stays on thyroid hormone ■ Decreased RAI dose to blood due to faster body clearance

> Or stimulate thyroid tissue with rhTSH

Low iodine diet before thyroid cancer therapy > less than ? micrograms/day > Start ?-? weeks prior to treatment

50 micrograms/day 1-2 weeks

 Dose of RAI (in general) > Low risk: ?mCi

100 mCi

 Dose of RAI (in general) > Higher risk, recurrent/residual disease: ?-? mCi

125-200 mCi

Dose of RAI (in general) > Occasionally treat with > ?-?mCi (recurrent, aggressive disease)

> 200-300 mCi

thyroid canacer therapy Patient NPO ?-? hrs prior to treatment

3-4 hrs

Post-procedure instructions for patient > Resume low-iodine diet ? hrs following I-131 ingestion ■ Normal diet may be resumed ?hrs post RAI > Encourage fluid intake ■ Frequent urination→ lower radiation dose to genitourinary tract > Begin using sour candy, gum ?-? hrs post treatment ■ Reduces stasis of I-131 in salivary glands ■ Reported increased salivary damage if given earlier than 24 hours > Resume thyroid hormone ?-? hrs post RAI therapy: continue thyroid hormone if rhTSH used

2 hrs 48 hrs 24-48 hrs 48-72 hrs

Expected Outcome > Better prognosis of thyroid cancer therapy:

-Age < 45 yrs -Small tumor, papillary/follicular -Females -Immediate treatment

Locoregional disease > Single dose of I-131: - ?% effective in eradicating disease

65%

> Single dose of I-131 ■ ?% effective for lung metastases ■ ?% effective for bone metastases

33% ■ 7%

PROBLEMS & COMPLICATIONS OF I-131 THYROID CANCER THERAPY

 Nausea  Diarrhea  Change in sense of taste  Sore throat  Radiation thyroiditis

Nausea > Common: prescribe?

antiemetic

Salivary gland complications > ?: Sour candy, gum use (> 24 hrs post RAI) may prevent > ? Worse in older patients, not common

Xerostomia Radiation parotitis:

Change in sense of taste > Usually returns to normal in ?-?months Sore throat > Due to local radiation dose from thyroid bed > ? for symptomatic relief  Radiation thyroiditis

1-6 months Throat lozenges

> Mild neck pain > More common when significant residual thyroid > Treat with nonsteroidal anti-inflammatory medication or corticosteroids

Radiation thyroiditis

Most feared complication(s) of I-131 THYROID CANCER THERAPY

> Radiation lung fibrosis ■ If diffuse pulmonary metastases, consider dosimetry > Bone marrow suppression ■ Consider dosimetry for very large doses, especially in children or renal insufficiency

Other complications of I-131 THYROID CANCER THERAPY

> Infertility ■ Possible very small risk of permanent infertility with multiple high doses in males > Anaplastic transformation of differentiated tumors ■ Few reported cases > Secondary malignancies ■ Very low risk; dose-related

RADIOPHARMACEUTICAL CHARACTERISTICS

 It is designed to mimic a natural physiologic process  The evaluation of function rather than anatomy  Use of gamma rays rather than x-rays  To minimize the patient radiation dose,

 To minimize the patient radiation dose, Radiopharmaceutical should have the following:

 Have a short half-life that is compatible with the duration and objectives of the nuclear medicine study  Produce monochromatic gamma rays with energies between 100 and 300 keV  Minimize production of particulate radiation such as beta particles, internal conversion electrons, and Auger electrons

Radiopharmaceutical should produce monochromatic gamma rays with energies between ? and ? keV

100 and 300 keV

Minimizing patient radiation dose

 Be non-toxic and contain no chemical or radionuclide contaminants  Localize in the organ or tissue of interest  Ideally, it should be readily and economically available

High Target/Nontarget Activity  The ability to detect and evaluate lesions depends largely on the ? of the radiopharmaceutical in the organ or lesion of interest.  To maximize the concentration of the radiopharmaceutical in the organ or lesion of interest and thus the image contrast, there should be little accumulation in other tissue and organs

concentration

Refers to the introduction of the radiopharmaceutical into a well-defined anatomic compartment

. Radiopharmaceutical Localization

Different LOCALIZATION PROCESS

1. COMPARTMENTAL LOCALIZATION AND LEAKAGE 2. CELL SEQUESTRATION 3. PHAGOCYTOSIS 4. PASSIVE DIFFUSION/SIMPLE EXCHANGE 5. ACTIVE TRANSPORT 6. METABOLISM 7. CAPILLARY BLOCKADE 8. CHEMOTAXIS 9. ANTIBODY-ANTIGEN COMPLEXATION 10. RECEPTOR BINDING 11. PHYSIOCHEMICAL ADSORPTION 12. PERFUSION

? is used to identify an abnormal opening in an otherwise closed compartment, as when labeled RBCs are used to detect gastrointestinal bleeding.

Compartmental leakage

with human serum albumin, plasma or RBC's

blood pool scanning

 RBCs are withdrawn from the patient, labeled with Tc-99m, and slightly damaged by in vitro heating in a boiling water bath for approximately 30 minutes.  After they have been injected, the spleen’s ability to recognize and remove () the damaged RBCs is evaluated. This procedure allows for the evaluation of both splenic morphology and function.

CELL SEQUESTRATION

In cell sequestration  RBCs are withdrawn from the patient, labeled with Tc-99m, and slightly damaged by in ? in a boiling water bath for approximately ? minutes.

vitro heating 30 mins

 The cells reticuloendothelial phagocytosis system is distributed in the liver (?%), spleen (?%), and bone marrow (?%).

85% 10% 5%

bone marrow (5%).  These cells recognize small foreign substances in the blood and remove them by ?

phagocytosis

he ? is part of the immune system, consists of the phagocytic cells located in reticular connective tissue, primarily monocytes and macrophages. -These cells accumulate in lymph nodes and the spleen. -The Kupffer cells of the liver and tissue histiocytes are also part of the ?.

reticuloendothelial system (RES)

? is simply the free movement of a substance from a region of high concentration to one of lower concentration.

Passive diffusion/simple exchange

Anatomic and physiologic mechanism exist in the brain tissue and surrounding vasculature that allow essential nutrients, metabolites, and lipid-soluble compounds to pass freely between the plasma and brain tissue while many water-soluble substances (including most radiopharmaceutical) are prevented from entering healthy brain tissue.  This system is called the ? -protects and regulates access to the brain.

blood-brain barrier

Disruptions of the blood-brain barrier can be produced by ?(3).  The disruption permits radiopharmaceutical such as Tc-99m DTPA, which is normally excluded by the blood-brain barrier, to follow the concentration gradient and enter the effected brain tissue.  Bone scanning with pyrophosphates.

- trauma, -neoplasm, and -inflammatory changes

? involves cellular metabolic processes that expend energy to concentrate the radiopharmaceutical into tissue against a concentration gradient above plasma levels.

Active transport

The classic example of actove transport is the ? and ?of radioactive iodide.

trapping and organification

Trapping of iodide in the thyroid gland occurs against a concentration gradient where it is oxidized to a highly reactive iodine by

peroxidase enzyme

Organification follows trapping of iodine, resulting in the production of radio-labeled ? and ?

triiodothyronine (T3) thyroxine (T4).

? is a glucose analogue: its increased uptake correlates with increased glucose metabolism. is used in approximately 85% of all clinical PET applications.  crosses the blood-brain barrier, where it is metabolized by brain cells.  enters cells via carrier-mediated diffusion (as does glucose) and is then phosphorylated and trapped in brain tissue for several hours as FDG-6-phosphate.

FDG fluorodeoxyglucose

FDG is fluorodeoxyglucose, is used in approximately ?% of all clinical PET applications.  FDG enters cells via carrier-mediated diffusion (as does glucose) and is then phosphorylated and trapped in brain tissue for several hours as ?

85% FDG-6-phosphate

 When particles slightly larger than RBCs are injected intravenously, they become trapped in the narrow capillary beds.  A common example in NM study is the assessment pulmonary perfusion by the injection of Tc-99m MAA, which is trapped in the pulmonary capillary bed.  Imaging the distribution of Tc-99m MAA provides a representative assessment of pulmonary perfusion.  The microemboli created by this radiopharmaceutical do not pose a significant clinical risk because only a very small percentage of the pulmonary capillaries are blocked and the MAA is eventually removed by biodegradation.

CAPILLARY BLOCKADE

? describes the movement of a cell such as a leukocyte in response to a chemical stimulus.

Chemotaxis

chemotaxis ? respond to products formed in immunologic reactions by migrating and accumulating at the site of the reaction as part of an overall inflammatory response.

111In-labeled leukocytes

An ? is a biomolecule (typically a protein) that is capable of inducing the production of, and binding to, an antibody in the body. The ? has a strong and specific affinity for the antibody.

antigen

? is also used in diagnostic imaging with such agents as In-Ill-labeled antibodies for the detection of colorectal carcinoma. -In addition, a variety of radio labeled (typically 1-131- labeled) monoclonal antibodies directed toward tumors are being used in an attempt to deliver tumoricidal radiation doses.

Antigen-antibody complexation

example of receptor binding, the uptake of ?, used for the localization of neuroendocrine and other tumors, is based on the binding of a somatostatin analog toreceptor sites in tumors.

In-111-octreotide

This class of radiopharmaceuticals is characterized by their high affinity to bind to specific receptor sites.  For example, the uptake of In-111-octreotide, used for the localization of neuroendocrine and other tumors, is based on the binding of a somatostatin analog to receptor sites in tumors.

RECEPTOR BINDING

PHYSIOCHEMICAL ADSORPTION  ? localization occurs primarily by adsorption in the mineral phase of the bone.  ? concentrations are significantly higher in amorphous calcium than in mature hydroxyapatite crystalline structures, which helps to explain its concentration in areas

Methylenediphosphonate (MDP)

is also an important diagnostic element in examinations such as renograms and cerebral and hepatic blood flow studies.  For example, the phase of a three-phase bone scan helps to distinguish between an acute process (e.g., osteomyelitis) and remote fracture. RADIATION PROTECTION

Perfusion

The means for achieving the objectives of radiation protection have evolved over many years to the point where, for some time, there has been a reasonably consistent approach throughout the world — namely the ? as espoused by the International Commission on Radiological Protection (ICRP).

‘system of radiological protection’,

The ? of a nuclear medicine facility, through the authorization issued by the regulatory body, has the prime responsibility for applying the relevant national regulations and meeting the conditions of the license. The ? may appoint other people to carry out actions and tasks related to these responsibilities, but the they retains overall responsibility.

licensee

In particular, ?(5) they all have key roles and responsibilities in implementing radiation protection in a nuclear medicine facility. Nuclear medicine specialist

-the nuclear medicine physician, -the medical physicist, - the nuclear medicine technologist, -the radiopharmacist and -the radiation protection officer (RPO)

The general medical and health care of the patient is, of course, the responsibility of the individual ? treating the patient. However, when the patient presents in the nuclear medicine facility, the ? has the particular responsibility for the overall radiation protection of the patient. -This means responsibility for the justification of a given nuclear medicine procedure for the patient, in conjunction with the referring medical practitioner, and responsibility for ensuring the optimization of protection in the performance of the examination or treatment.

physician nuclear medicine specialist

 The ? has a key position, and their skill and care to a large extent determine the optimization of the patient’s exposure.  are surrounded by patients full of radioactivity and receive a significant dose during injection of radiopharmaceuticals.

Nuclear medicine technologist

 Operator doses during injection are ?to ? mSv/hour.

0.01 to 0.02 mSv/hour.

 Handling of radionuclides requires the use of ? to minimize extremity doses.  Extremity doses need to be monitored using ? which are worn on a finger.

leaded syringes ring dosimeters

 NM operators risk intakes of radionuclides such as 131I and undergo ?(e.g., thyroid monitoring for iodine uptakes).  Protective clothing and handling precautions are required to minimize contamination.

mandatory bioassay

should be stored in fume hoods.

Volatile radionuclides(131I and 133Xe)

? should be performed of radionuclide use areas using a small piece of filter paper is wiped on an area and checked in a NaI well counter.

Wipe tests

Radioactive waste can be stored for ? half-lives prior to being surveyed and disposed of as regular waste. ’

ten half-lives

Annual effective doses for NM technologists’ range between ? and ?mSv\

1 and 5 mSv

PET poses considerable challenges because of the high energies of the annihilation photons (? keV), where two photons are emitted for every nuclear decay

511 keV)

In ? , very thick vial shields, syringe shields, and shadow shields are used to protect staff handling and administering ? radiopharmaceuticals.  ? imaging rooms and ? uptake rooms commonly have much thicker lead shielding than x-ray facilities

PET-Positron Emission tomography

It is highly recommended that the licensee appoints a person to oversee and implement radiation protection matters in the hospital. This person is called an ? -should have a good theoretical and practical knowledge of the properties and hazards of ionizing radiation, as well as protection. -In addition, the ?should possess necessary knowledge of all the appropriate legislation and codes of practice relating to the uses of ionizing radiation in the relevant medical area, e.g. nuclear medicine. -The ?, unless also a qualified medical physicist in nuclear medicine, has no responsibilities for radiation protection in medical exposure.

Radiation protection officer (RPO)

For instance, a ? in nuclear medicine should have a comprehensive knowledge of the imaging equipment used, including performance specifications, physical limitations of the equipment, calibration, quality control and image quality. -should also be qualified in handling radiation protection matters associated with nuclear medicine and has particular responsibilities for radiation protection in medical exposure, including the requirements pertaining to imaging (for diagnostic procedures), calibration, dosimetry and QA.

medical physicist

It is an important task for the ? to be actively involved in the planning and design of the nuclear medicine facility. Factors that are to be considered are: - -responsible for QA and for the local continuing education in radiation protection of the nuclear medicine staff and other health professionals.

medical physicist

Factors that are to be considered in facility design are:

— Safety of sources; — Optimization of protection for staff and the general public; — Preventing uncontrolled spread of contamination; — Maintaining low background where most needed; — Fulfilment of national requirements regarding pharmaceutical work.

In structural shielding calculations should include not only walls but also the floor and ceiling and must be made by a qualified ? ? should always be performed to ensure the correctness of the calculations.

medical physicist Radiation surveys

A ? is any area for which occupational exposure conditions are predictable and stable. They are kept under review even though specific additional protective measures and safety provisions are not normally needed.

supervised area

In a nuclear medicine facility, the rooms for preparation, storage (including radioactive waste) and injection of the radiopharmaceuticals will be ? Owing to the potential risk of contamination, the imaging rooms and waiting areas for injected patients might also be classified as ? The area housing a patient to whom therapeutic amounts of activity have been given will also be a ?

controlled areas

In the case of pure β emitters, such as ?(3), which are not excreted from the body, the area may not need to be classified as a controlled area.

90Yttrium, 89Strontium 32Phosphor

means checking the facility for the presence of radiation or radioactive contamination.

Workplace monitoring

The two basic types of workplace monitoring are ? and ?

-exposure monitoring and -contamination monitoring.

consists of measuring radiation levels (in microsieverts per hour) at various points using an exposure meter or survey meter.

monitoring. Exposure monitoring (sometimes called ‘monitoring’ or ‘radiation surveying’)

is the search for extraneous radioactive material deposited on surfaces.

Contamination monitoring

The ? in a nuclear medicine facility comprises many different types of waste. --It may be of high activity, such as a technetium generator, or of low activity, such as from biomedical procedures or research. In addition, it may have a long or short half-life and it may be in a solid, liquid or gaseous form -needs to be safely managed because it is potentially hazardous to human health and the environment.

radioactive waste

It is important that ?, in full compliance with all relevant regulations, is considered and planned for at the early stages of any projects involving radioactive materials. It is the responsibility of the ? to provide safe management of the radioactive waste. It should be supervised by the ? and local rules should be available.

safe waste management licensee RPO

? should be refrigerated or put in a freezer.

Biological waste

–The radiation dose to any organ or tissue is obtained by dividing the total energy absorbed in the organ by the organ mass.  Dividing the absorbed energy by the target organ mass absorbed in the organ by the organ mass.  is thus the absorbed dose in a target organ per unit cumulative activity in a source organ (i.e., Ssource→target).

S factor –

obtained by multiplying the source organ cumulative (A∞) and the source to target S factor.

organ dose

Organ dose (D)=

A∞× Ssource→target. source organ cumulative (A∞) x source to target S factor.

Highest organ doses from diagnostic nuclear medicine procedures are ∼?mGy.

∼50 mGy.

>As in radiology, the ? is the best indicator of patient risk in NM. >The average effective dose per procedures is ? mSv.

effective dose 5 mSv

>Effective doses in PET imaging are ∼?mSv.

∼10 mSv.

>CT scans performed for attenuation correction and fusion purposes alone use lower techniques with reduced effective doses of ∼? mSv

∼5 mSv

are sometimes used for therapeutic (not diagnostic) applications.

Radionuclides

 ? are ideal for therapy applications because the beta particle energy is primarily deposited in the organ taking up the radionuclide.

Beta emitters

 Target organ doses in 131I therapy applications are extremely high.  Administration of ? of 131 I can result in a high thyroid dose.  If half of this administered activity is taken up by the thyroid, the initial thyroid activity (A) is thus ?

370 MBq (10 mCi) 185 MBq (5 mCi).

 The physical and biologic half-lives of iodine are both ? days, so the effective half-life is ? days (i.e., 1/Te = 1/8 + 1/8).

8 days 4 days

(i.e., total number of nuclear transformations)

cumulative activity A∞

The cumulative activity A∞ (i.e., total number of nuclear transformations) in the patient’s thyroid is ?

1.44 × A × Te.

The thyroid dose to a patient receiving 370 MBq (10 mCi) of 131-I with a 50% thyroid uptake is thus ?

160,000 mGy (i.e., 160 Gy).

FINALS-CLINICAL Flashcards

(174 cards)