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RADIPHARMACEUTICAL 2

RADIPHARMACEUTICAL 2. NMT 241 Dr .Maha Khalid. Nuclear Medicine Vs Radiography. Nuclear Medicine = Function. Blood Flow: Myocardial, Brain • Metabolic Marker: 18 FDG , 123I-Fatty Acids • Organ Function: Phagocytosis/ Liver • Compartmental Localization: Cardiac , 133Xe,

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RADIPHARMACEUTICAL 2

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  1. RADIPHARMACEUTICAL 2 NMT 241 Dr .Maha Khalid

  2. Nuclear Medicine Vs Radiography

  3. Nuclear Medicine = Function • Blood Flow: Myocardial, Brain • • Metabolic Marker: 18 FDG, 123I-Fatty Acids • • Organ Function: Phagocytosis/ Liver • • Compartmental Localization: Cardiac, 133Xe, • GI Bleeding. • • Receptors Density: Dopamine • • Targeted: Antibodies • • Gastric Emptying: Real Meal Vs Barium Meal

  4. Biodistribution of Radiopharmaceuticals Determinants of Localization of Radioactive Drugs A. Organ characteristics B. Drug characteristics

  5. Biodistribution of Radiopharmaceuticals Determinants of Localization of Radioactive Drugs A. Organ characteristics  Relative Blood Flow to the organ  Types of capillaries in the organ  Capillary "density" or number per unit volume of tissue  Specific drug-receptor sites

  6. Biodistribution of Radiopharmaceuticals Determinants of Localization of Radioactive Drugs B. Drug characteristics  Molecular size and shape  Degree and strength of binding to plasma proteins  Lipid solubility  Specific drug receptor and transport mechanisms

  7. Chemical Structures Influencing Lipid Solubility

  8. Mechanisms of Localization • Active Transport • Phagocytosis • Cell Sequestration • Capillary Blockade • Simple or Exchange Diffusion • Compartmental Localization

  9. Active Transport • involves use of a normally operative metabolic pathway in the body for moving a radiopharmaceutical across a cell membrane and into the cell. Example: I-131 NaI for thyroid imaging

  10. Active Transport • is the movement of all types of molecules across a cell membrane against its concentration gradient (from low to high concentration). In all cells

  11. Active Transport - Thyroid scanning with iodide or pertechnetate • 43 year old female • Exophthalmus • Agitated • elevated free T4 • undetectable TSH • Tc-99m pertechnetate scan • RAIU 66% • Treatment 7.3mCi NaI-131

  12. Active Transport - Liver scanning with HIDA

  13. Phagocytosis • Process by which certain living cells called phagocytes ingest or engulf other cells or particles . Example: Tc-99m sulfur colloid for liver/spleen imaging.

  14. Phagocytosis - Liver scanning with colloids

  15. Cell Sequestration • A process in which the spleen withdraws some normal blood cells from circulation and holds them in case the body needs extra blood in an emergency . • Injection of damaged RBC's to produce a spleen scan with no visualization of the liver. Example: heat damaged autologous Tc-99m RBC's.

  16. Spleen scanning with colloids or heat damaged red blood cells

  17. Capillary blockade • Capillary blockade involves the intentional microembolization of a capillary bed with particles, permitting external visualization of the perfusion of this capillary bed. This is achieved by the IV injection of a radiolabeled, precipitated, biodegradable macroaggregate of human serum albumin commonly known as Tc-99m MAA 34.

  18. Simple or Exchange Diffusion • a mechanism whereby a radiotracer diffuses across cell membranes and then binds/attaches to a cell component. Example: Bone scanning with F-18 or Tc-99m phosphonates

  19. Bone Agents Structure MDP HDP Pyrophosphate

  20. Types of Bone Scans Whole Body Limited Three-phase

  21. Compartmental Localization • placement of a radiotracer in a fluid space and imaging of that fluid space. • Example: -Xe-133 gas for pulmonary perfusion. - Blood pool scanning of heart and vascular system with Tc-99m RBC

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