540 - Drug Delivery Systems - Exam Iv - Radiopharmacy

Front 1

Properties of an ideal diagnostic radiopharmaceutical:

Back 1

· Pure gamma emitter.
· Gamma energy of 100 - 250 keV.
· Effective half-life of 1.5 X test duration.
· High target:nontarget ratio.
· Minimal radiation dose to patient and nuclear medicine personal.
· Patient safety.
· Low chemical reactivity.
· Inexpensive
· Readily available
· Simple preparation and quality control if manufactured in house.

Front 2

What is a good effective half life for a diagnostic radiopharmaceutical and why?

Back 2

· Aim for 1½x the duration of the procedure
· This is a compromise between a desire to minimize radiation dose to patient and to maximize the signal, counting statistics and image quality for the technician.

Front 3

How do you calculate an effective half-life of a radiopharmaceutical?

Back 3

(1/t-effective) = (1/t-biological) + (1/t-physical)

Front 4

What do "extremes" look like in determining the effective half-life?

Back 4

1. Long biological half-life:
(1/t-effective) = (1/t-physical)
In this case, the half life is the physical half-life of the radionuclide.

i.e. Tc-99m sulfur colloid used to image the liver

2. Long physical half-life:
(1/t-effective) = (1/t-biological)
In this case, the half life is determined by how long the radionuclide stays in the body.

Front 5

Radiopharmaceutical used to image bone. Effective half-life: 6 hours

Back 5

Tc-99m methylene diphosphate (MDP). This is an example of the ideal radiopharmaceutical because the procedure takes 4 hours.

Front 6

How do you make Technitium-99m (Tc⁴⁺) from Pertechnetate anion (TcO₄⁻)

Back 6

Use the Stannous reduction method

· Mix pertechnetate with tin (Sn²⁺)
· Avoid atmospheric oxygen which will contaminate the reaction

Front 7

What are the radioisotopes of iodine?

Back 7

I-123, I-125, and I-131

Front 8

What are the properties of the iodine radionuclides?

Back 8

I-123 : ideal radionuclide, but expensive (100-400 µCi)

I-125 : low photon energy (30 keV)

I-131 : widely used, BUT: high energy gamma emitter (359 keV) AND beta emitter, long half-life

Front 9

What radionuclide is used to treat hyperthyroidism (Graves disease) and thyroid cancer? What precautions should you take?

Back 9

I-131 (ca. 30 mCi). Should delay pregnancy for at least 3-6 months after treatment (long half-life, after all...)

Front 10

What FOUR radionuclides are used to image new bone growth and what ONE radionucleide is used to treat bone pain?

Back 10

Bone growth:
· Ca-45
· Sr-85
· F-18
·Tc-99m methylene diphosphate (MDP)

Bone Pain:
· Sr-89 (a beta-emitter)

Front 11

What radionuclide is used to image the gall bladder and detect bile stones?

Back 11

Tc-99m labeled iminodiacetic acid (IDA)

Front 12

What radionuclide is used to image liver damage?

Back 12

Tc-99m sulfur colloid and Tc-99m micro-aggregated albumin. Healthy Kupffer cells phagocytose the colloidal particles while damaged liver areas show up as dim, "cold" spots.

Front 13

What radionuclide is used to image the entire heart?

Back 13

Tc-99m labeled red blood cells

Front 14

What radionuclide is used to image damaged heart tissue?

Back 14

Tc-99m (Sn)-tetracycline binds necrotic cardiac tissue (binds to calcium released)

Front 15

What radionuclide is used to image healthy heart tissue?

Back 15

I-123-16-iodo-9-hexadecanoic acid (used as an energy source in high-energy tissues)

Front 16

What radionuclide is used in cardiac stress tests?

Back 16

Tl-201 (a potassium analog, it is blood-flow dependent, so it concentrates in healthy tissue and avoids ischemic tissue)

Front 17

What radionuclide is used to image tumors?

Back 17

Ga-67 (it acts like iron, binds transferrin and accumulates at tumors / sites of inflammation)

Front 18

What TWO radionuclides are used for lung perfusion studies and how do they work?

Back 18

· Tc-99m macro-aggregated albumin is injected and accumulates in the lungs.
· Embolisms block blood flow so the Tc-99m doesn't image affected areas.
· Xe-133 gas is inhaled and images the entire lung.
· Any mismatch represents an area of the lung affected by an embolism.

Front 19

How is cerebral death diagnosed? What radionuclide is used?

Back 19

· Tc-99m pentetate (DTPA) follows blood flow and will normally distribute to the brain
· In cases of cerebral death, Tc-99m pentetate flows in the vessels outside the skull but is not detected in the brain.

Front 20

How is doxorubicin cardiotoxicity monitored?

Back 20

· Tc-99m labeled red blood cells are injected
· The left ventricle radioactivity is monitored at the beginning and ending of contractions.
· A healthy heart will have twice as much radioactive blood at end-diastole as at end-systole. Smaller differences indicate cardiotoxicity.

Front 21

Name NINE mechanisms of radiopharmaceutical localization and give examples of each :

Back 21

· Active Transport
- I-131 NaI for thyroid imaging

· Phagocytosis
- Tc-99m sulfur colloid for liver/spleen imaging

· Capillary blockade
- Tc-99m MAA for pulmonary perfusion imaging

· Cell Sequestration
- heat-damaged Tc-99m RBCs for spleen imaging

· Simple/Exchange Diffusion
- F-18 NaF for bone imaging

· Compartmental Localization
- Xe-133 gas for pulmonary perfusion

· Chemisorption
- In-111 platelets bound to a thrombus

· Antigen / Antibody Reaction
- In-111 Oncoscint for localization of ovarian/colorectal carcinoma

· Receptor Binding
- In-111 octoreotide binding to tumor somatostatin receptor sites

Front 22

Define : "Radiopharmaceutical"

Back 22

A chemical containing a radioactive isotope used for diagnosis, mitigation or treatment of disease.

Front 23

Define : "Isotope"

Back 23

Atoms with an equal number of protons but an unequal number of neutrons.

Front 24

What TWO tools are commonly used to visualize radioactivity?

Back 24

· a Gamma Camera - (2-D images)

· Single photon emission computerized tomography (SPECT) - (3-D images)

Front 25

What equipment is used to make materials radioactive and how does it work?

Back 25

A Cyclotron bombards elements with neutrons making them radioactive.

Front 26

How many protons, neutrons and nucleons are in the following? Which number would normally be left out?

14
      C
6

Back 26

Nucleons (protons + neutrons) : 14
- this information should always be given

Protons : 6
- this information is unique to the element (in this case "C") and is normally left blank

Neutrons : 8 (i.e. top-number - bottom number)

Front 27

What are the three basic forms of radioactive decay and what do they look like?

Back 27

Alpha - two protons and two neutrons

Beta - high energy "electron" (positron)

Gamma - high energy, ionizing radiation

Front 28

Which form of radioactive decay is the most damaging? Which is the most penetrating? Which is considered the most dangerous?

Back 28

Alpha - very damaging, awful penetration (blocked by paper)

Beta - moderately damaging, moderate penetration (blocked by aluminum foil)

Gamma - moderate-to-low damage, high penetration (blocked by lead)

Since gamma penetrates far and can disrupt chemical bonds, it's considered the most dangerous

Front 29

What is the radioactive decay law? (Differential AND Functional form)

Back 29

Differential:
∂A/∂t = -λA (λ ≥ 0)

Functional:
A = Aₒe^(-λt)

t₁/₂ = ln(2) / λ

Front 30

What TWO units are used to measure radioactivity?

Back 30

The Becquerel [Bq]
- SI unit of one disintegration per second

The Curie [Ci]
- Historical unit of 1 gram pure Ra-226

Front 31

How do activity and specific activity differ?

Back 31

Activity is disintegrations per unit time
(i.e. suppose a 5mg isotope has 20 mCi activity)

Specific activity is disintegractions per unit time per unit mass
(i.e. the 5mg isotope has 4 mCi/mg activity)

Front 32

What are the TWO units for absorbed radiation dose?

Back 32

The Gray [Gy]
- SI unit of 1 Joule per kg

The Radiation Absorbed Dose [rad]
- 100 ergs per g (equivalent to 0.01 Gy)

Front 33

What are the the TWO biological dose-equivalent units?

Back 33

The Sievert [Sv]
- the SI unit of 1 Gy x "quality factor"
- the quality factor varies among types of radiation (alpha, beta, etc)

The Radiation Equivalent Man (rem)
- 1 rem = QF x 1 rad
- 1 rem = 0.01 Sv
- Radiation sickness if > 100rem

Front 34

What are the TWO greatest sources of radiation exposure? What are "normal" exposures per year?

Back 34

Radon gas - 200 mrem/yr
Smoking - ~150 mrem/yr

Average person accumulates:
360 mrem/yr (non-smoker)

med X-rays/CAT scans generate 55 mrem/tr

Front 35

What are the values for the "Quality Factor" for different forms of radiation?

Back 35

β, ɣ, X-ray : 1

neutrons : 1 - 20

α-particles : 20

Front 36

What affects a radiation dose?

Back 36

· Type and energy of radiation
· Amount of radionuclide (total body dose)
· Radionuclide distribution in the body
· Relative size and sensitivity of tissues (rapidly differentiating cells – fetus, hematopoietic tissues, germ cells of the reproductive organs)
· Physical half-life
· Biological half-life
- Effective half-life

Front 37

By what direct and indirect actions can radiation cause damage?

Back 37

Indirect - ionizing radiation can create reactive ions, such as free radicals and peroxides and can alter sulfhydryl groups on proteins

Direct - DNA damage (mutagneic and carcinogenic)