Nuclear Medicine Radiopharmaceuticals Flashcards

Vocabulary practice flashcards generated from lecture notes on nuclear medicine radiopharmaceuticals, detailing mechanisms of localization, energy characteristics, preparation protocols, and imaging applications.

Ideal Radiopharmaceutical Energy

A favorable photon energy between $100\,\text{keV}$ and $200\,\text{keV}$ with a minimum of particulate (beta) emission.

Specific Activity

The radioactivity per unit weight of a radiopharmaceutical, expressed in $\text{mCi/mg}$.

Technetium-99m

The most commonly used radionuclide in nuclear medicine, featuring a principal gamma photon energy of $140\,\text{keV}$, a physical half-life of $6\,\text{hours}$, and no primary particulate radiations.

Tc-99m Sodium Pertechnetate

A radiopharmaceutical that rapidly concentrates in salivary glands, choroid plexus, thyroid gland, gastric mucosa, functioning breast tissue, kidneys, bladder, colon, and sweat, with the colon receiving $1\text{--}2\,\text{rad}/10\,\text{mCi}$ ($0.04\,\text{mGy/MBq}$) as the critical organ.

Iodine-131 Sodium Iodide

A radionuclide with a photon energy of $364\,\text{keV}$, a physical half-life of $8\,\text{days}$, and beta particle emissions, used for treating hyperthyroidism and differentiated thyroid cancer.

Iodine-123 Sodium Iodide

A radionuclide with a half-life of $13.2\,\text{hours}$ and principal photon energy of $159\,\text{keV}$ that decays by electron capture, used for diagnostic thyroid scans, whole-body thyroid cancer scans, and MIBG imaging.

Indium-111

A cyclotron-produced metal and iron analog with a physical half-life of $67\,\text{hours}$ and principal photon energies of $173\,\text{keV}$ ($89\%$) and $247\,\text{keV}$ ($94\%$).

Thallium-201

A potassium analog with a physical half-life of $73.1\,\text{hours}$ that decays by electron capture to mercury-201, emitting x-rays from $68\,\text{keV}$ to $80\,\text{keV}$ ($94.5\%$), used for myocardial viability studies.

Xenon-133

An inert gas with a physical half-life of $5.2\,\text{days}$ and principal gamma photon energy of $81\,\text{keV}$, used for pulmonary ventilation studies across initial breath, equilibrium, and washout phases.

Radiochemical Purity

The percentage of total radioactivity in a specimen that is in the specified or desired radiochemical form, which must meet USP standards of $90\%$ and is assayed using instant thin-layer chromatography (ITLC).

ITLC Quality Assurance for Tc-99m Diphosphonate

A testing method using acetone solvent on paper/ITLC strips to separate free pertechnetate (migrates with front) from bound agent and hydrolyzed reduced technetium (stay at origin), and saline solvent on silica gel strips to isolate hydrolyzed reduced technetium (stays at origin).

Active Transport (Localization)

A radiopharmaceutical localization mechanism involving the use of a normally operative metabolic pathway in the body to move a radiopharmaceutical across a cell membrane into the cell, such as I-123 NaI for thyroid imaging.

Phagocytosis (Localization)

A radiopharmaceutical localization mechanism involving physical entrapment of colloidal particles by Kupffer cells in the reticuloendothelial system, such as Tc-99m sulfur colloid for liver/spleen imaging.

Capillary Blockade

A radiopharmaceutical localization mechanism involving intentional microembolization of a capillary bed with particles, such as Tc-99m MAA for pulmonary perfusion imaging.

Cell Sequestration

A localization process by which the spleen recognizes and removes damaged red blood cells from circulation, such as heat-damaged autologous Tc-99m RBCs injected for a spleen scan without liver visualization.

Compartmental Localization

A localization mechanism involving the placement of a radiotracer in a fluid space and imaging of that space, such as Tc-99m RBCs for MUGAs, In-111 DTPA for cisternograms, or Xe-133 gas for pulmonary ventilation.

Chemisorption

A localization mechanism involving the surface binding of a radiopharmaceutical to a solid structure, such as Tc-99m medronate (MDP) or Tc-99m oxidronate (HDP) absorbing onto hydroxyapatite crystals in bone.

Chemotaxis (Localization)

The movement of cells in response to a chemical stimulus, utilized when white blood cells radiolabeled with In-111 oxine or Tc-99m exametazime (HMPAO) migrate to sites of inflammation or infection.

Tc-99m Sulfur Colloid

A radiopharmaceutical localized via phagocytosis by Kupffer cells in the liver ($85\%$), macrophages in the spleen ($10\%$), and bone marrow ($5\%$), with the liver as its critical organ.

Tc-99m MAA (Macroaggregated Albumin)

A pulmonary perfusion radiopharmaceutical localized by capillary blockade; $90\%$ of particles must measure $10\text{--}90\,\mu\text{m}$, with a recommended particle count of $200,000\text{--}700,000$ per injection and the lungs as the critical organ.

Tc-99m DTPA Aerosol

A pulmonary ventilation agent administered via nebulizer at an oxygen flow rate of $7\text{--}10\,\text{L/min}$; it localizes in alveolar sacs via simple diffusion, with the lungs as the critical organ.

Tc-99m Hepatobiliary Radiopharmaceuticals

HIDA analogs (Disofenin / Hepatolite and Mebrofenin / Choletec) that localize via active transport by hepatocytes along the bilirubin pathway, with the large intestine as the critical organ.

Tc-99m Methylene Diphosphonate (MDP)

A skeletal radiopharmaceutical that localizes via chemisorption to hydroxyapatite crystals, with $50\%$ of the dose taken up by bone and the remainder excreted by the kidneys, leaving the bladder wall as the critical organ.

Tc-99m Mertiatide (MAG3)

A renal dynamic radiopharmaceutical cleared by tubular secretion via active transport to measure effective renal plasma flow (ERPF); prepared by adding filtered air and heating at $100\,^\circ\text{C}$ for $10\,\text{minutes}$, with the bladder wall as the critical organ.

Tc-99m DMSA (Dimercaptosuccinic Acid)

A renal cortical imaging agent localized by active transport in the proximal tubules to evaluate renal scarring and pyelonephritis, cleared slowly by the kidneys with the kidneys as the critical organ.

Tc-99m Sestamibi (Cardiolite)

A lipophilic isonitrile cation that diffuses into myocytes and binds mitochondria via passive diffusion; it does not redistribute, requiring separate rest ($10\,\text{mCi}$) and stress ($30\,\text{mCi}$) doses with the colon as the critical organ.

Tc-99m Tetrofosmin (Myoview)

A lipophilic myocardial perfusion radiopharmaceutical that localizes near mitochondria via passive diffusion, featuring faster liver clearance than sestamibi and having the gallbladder as its critical organ.

Ultratag RBC Kit

A commercial kit containing a stannous chloride vial, syringe 1 (sodium hypochlorite), and syringe 2 (citric acid, sodium citrate, dextrose) used for in vitro labeling of red blood cells for MUGA, GI bleed, and hepatic hemangioma studies.

Tc-99m ECD (Bicisate / Neurolite)

A lipophilic cerebral perfusion agent that crosses the blood-brain barrier and localizes in gray matter via passive diffusion proportional to regional cerebral blood flow (rCBF), highlighting seizure foci (hot) or Alzheimer's hypoperfusion (cold).

Tc-99m Exametazime (HMPAO / Ceretec)

A lipophilic radiopharmaceutical used for brain perfusion imaging via passive diffusion, or for leukocyte labeling (without methylene blue) to detect infection sites via chemotaxis, with the spleen as the critical organ for labeled WBCs.

Indium-111 DTPA Cisternogram

An intrathecal nuclear medicine procedure with dose $500\,\mu\text{Ci}$ ($18.5\,\text{MBq}$) used to assess CSF shunt patency or CSF leaks via compartmental localization, with the spinal cord as the critical organ.