7 k e V 5 9 T c 3 g % 8 I C (6.01 h) m (2.111x105 y) g1ģ1 Transient equilibrium is the basis of: Produce radionuclides using different chemical properties between the parent and child parent T1/2 child decay T1/ Sr d Rb b+,EC 1.3m Mo h mTc IT hģ0 Nuclear decay scheme 99Mo42 99mTc43 + e- + (87.6%)ĩ9mTc43 99Tc43 + 1 4 2. 876 For 99mTc, Max yield ~ 24 hrs ~3 Curies of Mo99 Nuclear Medicine Physics for Radiology Residents Sameer Tipnis, PhD, DABR Tb = Time taken to reduce the amount of radiopharmaceutical in the body by one half due to various clearance mechanisms (excreta, perspiration, etc.) Nuclear Medicine Physics for Radiology Residents Sameer Tipnis, PhD, DABRĢ0 Effective half life Te = Time to reduce radiopharmaceutical in the body by one half due to functional clearance and radioactive decay □ □□ = □ □□ + □ □□ Te = □□□□ □□+□□ if Tp > Tb, Te ≈ Tb if Tp Td 99Mo42 99mTc43 + e- + 66 h % 99mTc43 99Tc43 + 6 h They decay in parallel after tmax to achieve equilibrium. ![]() Photons useful for detection and imaging are: Gamma 2, 90% abundant, 171 keV Gamma 3, 94% abundant, 245 keV Marketed as ProstaScint by Mallinckrodt for imaging of prostate cancer cells Also used to label white blood cells for detection of inflammation Assuming none of the activity is excreted, what is the remaining activity at the time of imaging? A0 = 500 Ci t = 2 days = 48 hr Tp = 67 hr At = A0e-t = 0.693/Tp = 0.693/67 hr = hr-1 t = hr-1 x 48 hr = 0.5 At = 500 Ci x e-0.5 = 303 Ci Nuclear Medicine Physics for Radiology Residents Sameer Tipnis, PhD, DABRġ8 Indium In-111 decays by electron capture to cadmium Cd-111 (stable) ![]() Tp = time required for the number of radioactive atoms to reduce by one half Basic equations: Nt = N0e-t or At = A0e-t Tp = / = / Tp N0 = Initial number of radioactive atoms Nt = number of radioactive atoms at time t Nuclear Medicine Physics for Radiology Residents Sameer Tipnis, PhD, DABRġ6 8 t1/2 ~ 0.4% 10 t1/2 ~ 0.1% Nuclear Medicine Physics for Radiology Residents Sameer Tipnis, PhD, DABRġ7 A0 = 500 Ci t = 2 days = 48 hr Tp = 67 hrĪ pt is injected with 500 Ci of 111In (Tp = 67 hrs). Curie) 1 mCi = 37 MBq NM imaging: ~ 1 to 30 mCi (30 – 1100 MBq)ġ2 Question How many F-18 atoms are there in 10 mCi of FDG? (T1/2 = 110 min) A. Electron capture can be a competing mode of decay A to 2 A to 6 B to 3 B to 8 C to 1 C to 4 D to 5 D to 7ġ0 Radioactivity : decay constant with units of 1/sec or 1/hrĪ (t): disintegration rate at time t (decays/sec) N(t): number of nuclei at time t : decay constant with units of 1/sec or 1/hr = ln2/T1/2 = 0.693/T1/2 half life: T1/2 = ln2/ = 0.693/ġ1 Radioactivity unit in SI: 1 Bq = 1 disintegrations per second (Becquerel) traditional unit: 1 Ci = 3.7×1010 dps (1g of Ra-226, extracted first by Mme. G-ray emission or internal conversion follows if the child nucleus is in an excited state Any resultant electron vacancies are resolved through emission of characteristic X-rays and/or Auger electrons (radiation dose with no imaging benefit)ĩ Question Match the decay mode to the description below:Ī. Ga67 (gallium citrate): tumor localization Ga-67 used in tumor localization Also In-111, I-123, I-125 and Tl-201 No beta to contribute to doseĦ Nuclear decay scheme -decay I131 (NaI): thyroid disorders and cancerħ Nuclear decay scheme -decay Tc99m (various compounds): various usesĨ Following - and + decay and Electron Capture Sometimes drawn with vertical drop of 1.02 MeV for positron emission (rest mass equivalence of 2 electron electron masses) Also Rb 82 for myocardial imagingĥ Nuclear decay scheme EC (electron capture) -decay: AXZ AYZ+1 + e- + ~ -decay: AXZ AYZ-1 + e+ + e-capture: AXZ + e- AYZ-1 + -decay and internal conversion: no changes for A & ZĤ Nuclear decay scheme +-decay and EC (electron capture)į18 (FDG): cancer, myocardial disease, etc. ![]() Medical University of South Carolina for Sharing nuclear medicine presentation contentģ A Review Nuclear decay rules Based on conservation laws Medical College of Georgia And Sameer Tipnis, Ph.D. Department of Radiology and Imaging Medical College of GeorgiaĢ Medical College of Georgia And Sameer Tipnis, Ph.D.Ī note of thanks to Z. Radioactivity and Radioactive Decay Radionuclide Production Jerry Allison, Ph.D. Presentation on theme: "Nuclear Medicine Physics"- Presentation transcript:
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