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Radioactivity & it's applications in Medicine

Radioactivity & it's applications in Medicine



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Radioactivity Radioactivity Presentation Transcript

  • RADIOACTIVITY By: Payal Patel
  • LEARNING OBJECTIVES:  Isotopes  Radioactive decay & Half life  Applications of Radioactivity  Biological effect of radiation
  •  Atom: • Basic unit of mater • Consist central dense +ve charge nucleus and cloud of – ve charge • Nucleus: • Proton(P+): +ve charge • Neutron(n): no net charge • Electrons(e-): -ve charge
  •  Atomic weight of element = protons + neutrons  Atomic no = no of protons Mass no- upper left side Atomic no-left lower side e.g Deuterium
  • Isotopes:  Isotopes are elements having the same atomic number(protons) but different mass number(no. of protons & neutrons)  Isotopes are differ from each others in it’s no. of neutrons  They occupy the same place in periodic table  Isobars: elements having same mass no. but different atomic no
  •  Isotopes are may be stable or unstable  Nuclei of unstable atom will spontaneously decompose to form nuclei with higher stability this decomposition process is called Radioactivity.  During this process energy and particles are released this process called radiation.  It is also called radioactive decay
  •  Radioactive elements emit three types of radiation: 1. α-rays: 2. β-rays: 3. ɤ- rays:
  • • Consist 2P and 2n, +ve charge • It is Similar to Helium nucleus He+2 • When it released element change (atomic no reduced by 2 and mass no reduced by4) • It is not useful in clinical medicine because its penetration is very less, stop by few layers of paper. • It produce maximum ionization in the path
  • ΒETA-RAYS:  When neutron is split one proton and one electrone is generated  Thus element is change with one more no of atomic no. while mass no. is same  Element change to one higher no. in periodic table.  Electron thus emitted become the β-rays so they are –ve charged.  They less absorbed so have greater pentration  They can travel few feet in air but absorbed by metal sheet.
  • ɤ-RAYS:  It is in the form of electromagnetic waves.  It has no mass and no charge their for penetration power is maximum.  It’s penetration stop by thick layer of lead.  It is widely used for treatment of cancer cases.
  • UNIT OF RADIOACTIVITY:  Curie(Ci): used for measure radioactivity of the source.  1Ci=3.7 x 1010 disintegration/s  Rontgen(R): used for measurement of exposure dose  1R= 2 x 109 ion pairs/cc of air  Red: it is absorbed dose by tissue  1Red=1.5 x1012 ion pairs /g tissue
  •  Half life of radioactivity: • Time required for isotope to become half of it’s original value is called half life • It is constant for particular isotope  e.g. 131I-8days 125I-60days
  • APPLICATION:  In medical field radioactivity mainly apply for:  Research:  Diagnosis:  Treatment:
  • RESEARCH APPLICATION:  In research radioactivity is used as tracer technique.  Isotopes of an elements will have identical chemical reaction hence when a radio labeled compound administered these molecule are metabolized by body similar to normal molecule.  Used for study of all metabolic pathway, synthesis and degradation of substance in the body.  14C : metabolic pathway  3H : research in cell biology  32P : nucleic acid research
  • APPLICATION IN DIAGNOSIS:  In diagnosis radioactivity is used by two procedure: 1. In vivo 2. In vitro  In vivo: radioactivity administered into patient  It used for the study of dynamic function and organ scanning.  Gamma rays are given by injection, inhalation or by orally
  •  Study of dynamic function:  Thyroid uptake of radioactive iodine:  131 I used to detect functional derangement of thyroid gland  15 micro Ci of 131I is given IV  Normally 25% I is uptake by thyroid in 2hours and 50% within 24hours.  In hyperthyroidism uptake increased  Hypothyroidism uptake is decreased.
  •  Absorption test of B12 vitamin: 0.5-1.0 microgram of label 60CO is used  Normally excretion>15%  In pernicious anemia and deficiency excretion<5%  Pulmonary function: 133xenon  Fat absorption:131I  Renal clearance: 51Cr
  •  Organ scanning:  Thyroid scanning: 131I for scanning of size n shape of thyroid gland and detection of thyroid tumor  Brain scanning: 99TC(technetium) and 133In(indium) used for brain scanning and brain tumor detection.  Lung scanning: 131I used for early detection of pulmonary infarction when x-ray is normal  Bone scanning; 90Sr(strotium) for detection of osteoblastoma  Kidney scanning: 131I labelled hippuran
  •  In in vitro: sample is collected and it is analyzed by techniques involving use of radioisotopes  In vitro use for estimation of hormones ,tumor marker and other biological substance present in blood in very small quantities by RIA. e.g. 131I
  • APPLICATION IN TREATMENT:  Radioactivity is used for treatment of cancer.  Radiation when absorbed by the tissue produced ionization and cause physical and chemical changes in the cell. Thus nucleic acid in the cell is damaged. So cell division is not possible.  It mainly affecting the cell in dividing phase (s) so cancer tissue contain more dividing cell than normal tissue and they affected by radiation.  But single dose is not effective so small divided dose are given
  •  Depending on the source of radiation radiotherapy may classified as: 1. Unsealed sources 2. Sealed sources 3. Teletherapy
  •  Unsealed sources: Readioactive substance kept in liquid form and β rays are most effective radiation in this source. 50-100mCi 131I use for thyroid cancer 5mCi 32P use for polycythemia vera
  •  Sealed sources: • Radioactive source is covered by platinum alloy to absorb α and β radiation, so only ɤ rays are allowed to penetrate into the tissue. • if α and β rays are allow to pass they cause necrosis of tissue around the source. • It applied on the cancer directly or as a needle into tissue. • 137 Cs(cesium) used as sealed source • This is called Brachytherapy
  • Uterus Cervix Prostate Intraocular Skin Thyroid Bone This involves placing implants in the form of seeds, wires or pellets directly into the tumour. The benefit of such a method is that the tumour receives nearly all of the dose whilst healthy tissue hardly receives any. It is used for treatment of cancer of :
  • TELETHERAPY:  Here the source of radiation is kept at a distance from patient.  60 CO or 137Cs(cesium) used for teletherapy  ɤ rays can penetrate deep into the tissue to treat internal cancer without causing sever skin reaction  It is replaced by LINAC
  • RADIOSENSITIVITY  Lymphomas, neuroblastomas – highly sensitive  Epithelioma, cancer of oral cavity, cervix, breast & lung- moderatly sensitive  Malignant melanoma, osteosarcoma-poorly
  • BIOLOGICAL EFFECTS OF RADIATION ON NORMAL TISSUE:  Effect on skin: • Epilation(hair loss) • Damage to sweat gland • Acute radio dermatitis- erythema, blister • Chronic radio dermatitis- atropy of skin, hypo pigmentation, fibrosis, loss of elasticity  Mucous membrane: • Nausea • Vommitting • Diarrhea • Ulceration, bledding
  •  Blood cell: • Leucopenia • Thrombocytopenia  Reproductive organ: • Sterility 1000RED • Affect gene so produced genetic alteration in the offspring  Carcinogenic potential : Persons working with x-ray without any precausion
  • RADIATION SAFETY AND PROTECTION:  Important Protection is time, distance, and shield  Should wear a badge containing a piece of film  Minimum time should be spent near the radiation zone  Handling of radioactive material should be done from a maximum distance