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Chapter 2 continued


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Chapter 2 continued

  1. 1. Chapter 2 Continued…
  2. 2. Most Chemical Reactions Involve Electrons – Bonds Break and/or Form
  3. 3. Fatty acids Lipase H2O Hydrolysis reaction Glycerol Triglyceride Most Chemical Reactions Involve Electrons – Bonds Break and/or Form Example: Digestion of fats and oils (triglycerides)
  4. 4. Nuclear Chemistry Involves Changes in the Nuclei of Elements Protons and neutrons are in the nucleus, and constitute the majority of atomic mass Electron “cloud” Negative charge
  5. 5. Nuclear Chemistry Involves Changes in the Nuclei of Elements Different atoms in reactants and products - yet the equation is balanced. Same mass, same charge on each side. + Example: Uranium-238 decay
  6. 6. Nuclear Radiation Common forms 1) Alpha particles 2) Beta particles 3) Positron particles 4) Gamma rays (not particles; electromagnetic radiation)
  7. 7. Electromagnetic Radiation A type of energy with electric and magnetic field components that travels as waves at the speed of light in a vacuum.
  8. 8. Notes…
  9. 9. Radiation Exposure Geiger counter measures radiation: Portable device with an argon filled chamber. Radiation ionizes Ar, generates electric current, and produces a clicking sound. Measure decay over time. Measuring radioactivity in a sample: 1 becquerel (Bq) = 1 disintegration / second 1 Ci = 3.7 x 1010 disintegrations / second = 3.7 x 1010 Bq 1 mCi = 10-3 Ci 1 µCi = 10-6 Ci Natural radiation surrounds us – cosmic rays, radiation in soil (e.g. radon) You do not need to remember Bq and Ci conversion factors
  10. 10. Problems β γ+ + ? 1) Complete the following nuclear equation: 2) Write a balanced nuclear equation for the β- emission of phosphorous-32, a radioisotope used to treat leukemia and other blood disorders. 3) The radioisotope xenon-118 is used in lung ventilation scans. Write a balanced nuclear equation for its decay by positron emission. 4) The half-life of phosphorous-32 is 14 days. Beginning with 5 g of 32 P, how much would remain after 42 days? 5) What type of shielding would healthcare workers use to protect themselves from gamma radiation emitted by cobalt-60? 6) A patient must be given a 4.5 mCi dose iodine-131, which is available as a solution that contains 3.5 mCi/mL. What volume of solution must be administered?
  11. 11. Nuclear Medicine Branch of medicine that utilizes radioactive materials to: A.Diagnose medical conditions B.Treat medical conditions
  12. 12. Detection of γ-radiation Diagnostic Nuclear Medicine Relies on Gamma Radiation Why γ-radiation for imaging instead of α- or β-radiation? Injection or ingestion of γ- ray emitter into patient 99m Tc, 131 I, 201 Tl
  13. 13. Can detect cancer, fractures not visible on x-ray, or damage from infection or illness 1) Inject Tc-99m MDP into patient 2)Bone absorbs Tc-99m MDP to a greater extent where there is injury, infection, or cancer due to higher metabolic activity 3)Tc-99m emits γ-radiation 4)Detect higher levels of γ-radiation where abnormality is located 99m Tc 99 Tc + γ Bone Scan Using Technetium-99m Tc-99m MDP Absorbed by bone Bone mineral: calcium hydroxyapatite [Ca5(PO4)3(OH)] t1/2 = 6 h MDP = methylene diphosphonate
  14. 14. Bone Scan of Prostate Cancer Patient Reveals Bone Metastases “Hot spot” in bladder due to Tc-99m MDP tracer excretion via urine Patients advised to drink plenty of fluids following scan Tc-99m MDP bone scan depicts metabolic activity Whereas x-rays CAT scans show anatomy and structure Front Back
  15. 15. Positron Emission Tomography (PET) 2 γ • PET radioisotopes emit positrons • Positrons collide with electrons to form gamma rays (annihilation) • The gamma rays are detected with external gamma camera Carbon-11, oxygen-15, nitrogen-13, fluorine-18 emit positrons and are used in PET. Fluorine-18 is most commonly used. 18 F 18 O + β+ e- positron electron gamma rays t1/2 = 109 min
  16. 16. Positron Emission Tomography (PET) Using 18 F-FDG 1) Inject 18 F-fluorodeoxyglucose (18 F-FDG) in patient 18 F-FDG is a radiolabeled glucose analog 2) 18 F-FDG accumulates in regions of high metabolic activity (glucose = energy source) a. Brain b. Heart c. Liver b. Cancer cells 2) Detect gamma radiation where 18 F-FDG is taken up O HO HO 18 F OH 18 F-fluorodeoxyglucose (18 F-FDG) OH glucose O HO HO OH OH OH PET depicts metabolic activity
  17. 17. “Hot spots” - regions of high glucose uptake Applications : Oncology – Diagnose tumors, measure response to therapy Neurology – Image brain for Alzheimer’s, epilepsy, stroke Cardiology – Assess blood flow, tissue damage to heart 18 F-FDG PET Depicts Metabolic Activity
  18. 18. Nuclear Medicine Branch of medicine that utilizes radioactive materials to: A.Diagnose medical conditions B.Treat medical conditions
  19. 19. Radiation damages DNA and interferes with cell division. Since cancer cells undergo rapid proliferation, they are more sensitive to radiation than normal cells. Cobalt-60 is an external gamma radiation source 60 Co 60 Ni + β- + γ t1/2 = 5 years β- radiation is blocked γ-radiation administered to patient Why is a 5 year half-life OK for this application? Radiation Therapy for Cancer – External Radiation Source “Gamma Knife”
  20. 20. Radiation Therapy for Cancer – Internal Administration of Radioisotopes Brachytherapy β-Radiation: high energy electrons penetrate tissue in small, localized regions. Iridium-192 implants for breast cancer Phosphorus-32 administered intravenously for leukemia NaH2 32 PO4 absorbed by bone t1/2 = 14 d t1/2 = 74 d What is the advantage of a radioisotope implant versus IV?
  21. 21. Iodine-131 for Thyroid Disorders Iodine-131 is more localized in the thyroid gland – the radiotherapy target Thyroid hormone thyroxine NaI from diet (iodized salt) Na131 I Normal thyroid Treatment for hyperthyroidism or thyroid cancer Radioactive thyroxine kills thyroid cells
  22. 22. Selection of Radioactive Isotopes for Nuclear Medicine 1)Radioisotope containing molecule must be taken up by the target organ 2)Radioisotope containing molecule should have different affinity for normal and diseased tissue (diagnose abnormalities or target cancer cells) 3)Radioisotope should have appropriate half-life 4)Radioisotope must undergo appropriate type of decay