Radiopharmaceuticals Part 1

radiopharmaceutical favorable energy

100-200 keV

radiopharmaceutical desired particulate emission

minimum possible, majority gamma rays, little to no beta

radiopharmaceutical ideal half life

long enough to perform the exam

radiopharmaceutical suitable chemical form

carrier-free, high specific activity

radiopharmaceutical desired characteristics (7)

1. favorable energy

2. minimum particulate emission

3. ideal half life

4. suitable chemical form

5. low toxicity

6. stability

7. availability

What is the most commonly used radionuclide?

Technetium-99m

target organ

organs we want to view with a scan

critical organ

organ that receives the highest radiation during a scan (not necessarily the target organ)

99m Tc Sodium Pertechnetate (Na^99mTcO₄^-) target organs

salivary glands, choroid plexus (brain), thyroid gland, gastric mucosa, functioning breast tissue, kidneys, bladder, colon, sweat

99m Tc Sodium Pertechnetate (Na^99mTcO₄^-) critical organ

colon (1-2 rad/10 mCi of tech)

Tech thyroid scan vs Iodine thyroid scan

Tech = anatomy
Iodine = physiology (ORGANIFIED)

I-131 Sodium Iodide photon energy

364 keV

I-131 Sodium Iodide half-life

8 days

I-131 Sodium Iodide uses today

treatment of hypothyroidism and differentiated thyroid cancer

*after treatment, image can be taken to verify where iodine was taken up

I-123 Sodium Iodide photon energy

159 keV

I-123 Sodium Iodide half-life

13.2 hours

I-123 Sodium Iodide decay

electron capture

I-123 Sodium Iodide uses today

diagnostic thyroid scans, whole-body thyroid cancer scans, MIBG imaging

I-123 ioflupane use

DaTscan for diagnosis of Parkinson disease

Lugols solution

administered to patient prior to DaTscan so that iodide will pass the thyroid and concentrate in the brain

I-131 and I-123 target organs

salivary glands, thyroid, gastric mucosa, bowel, and bladder

I-131 and I-123 bioelimination

primarily urinary excretion, some fecal excretion

Indium-111 half-life

67 hours

Indium-111 production

cyclotron

Indium-111 photon energies

173 keV and 247 keV

Indium-111 DTPA used for

intracranial cisternography (brain leakages)

Indium-111 oxine labeled white cells used for

scanning for infections

Thallium-201 half-life

73.1 hours

Thallium-201 decay

electron capture to mercury-201

Mercury-201 emissions

x-rays: 68-80 keV (94.5%)
gamma rays: 135 keV (2.5%) and 167 keV (10%)

Thallium-201 used for

myocardial viability studies

What radiopharmaceutical is used for routine stress testing to detect coronary artery disease?

Tc-99m labeled cardiac perfusion radiopharmaceuticals

Xenon-133

inert gas most commonly used for pulmonary ventilation studies

Xenon-133 half-life

5.2 days

Xenon-133 photon energy

81 keV

What is the most commonly used radiopharmaceutical in pulmonary ventilation studies?

Tc-99m labeled aerosols

commercial kits

contain reaction vial with stannous ion (tin), nonradioactive pharmaceutical to be labeled, other buffering and stabilizing agents

What are commercial kits flushed with?

nitrogen

Why are commercial kits flushed with nitrogen?

to prevent atmospheric oxygen interrupting the reaction

Why do commercial kits contain a stannous ion, tin?

Tin drops the valence of Tc-99m from +7 to +4, which makes it more willing to bond with tagging agents

Definition of specific activity

activity per unit mass (Ci/kg or Bq/g)

How is Xe sent to the hospital?

in a vial, then aerated

Where do we store MAA?

in the refrigerator

Ideal range for a gamma camera

100-200 keV

Do we prefer radionuclide to circulate through the body more or less?

less, we want to image the target organ sooner

What does NRC stand for?

Nuclear Regulatory Commission