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  4/10/20181 KA –MIT –Unit III –March, 2018, Sastra, Deemed University Medical Imaging Techniques Dr. K. Adalarasu 1 KA –MIT –Unit III –March, 2018, Sastra, Deemed University Textbook and Materials  Rafael C. Gonzalez, Richard E. Woods, “Digital Image Processing”, 2 nd Edition, Pearson Education, 2003  Digital Image Processing by Jayaraman, Veerakumar, 2012  Khandpur R.S, Handbook of Biomedical Instrumentation, 3/e, Tata McGraw Hill,New Delhi, 2014 2 KA –MIT –Unit III –March, 2018, Sastra, Deemed University Reference  William K. Pratt, “Digital Image Processing” , John Willey ,2001  Steve Webb, The physics of medical imaging,  Adam Hilger, Bristol, England, Philadelphia, USA, 1988  Jain A.K., “Fundamentals of Digital Image Processing”, PHI, 1995. 3 KA –MIT –Unit III –March, 2018, Sastra, Deemed University Radio Isotope Imaging 4  4/10/20182 KA –MIT –Unit III –March, 2018, Sastra, Deemed University Radio Isotopes in Medical Diagnosis  Used in medicine both for therapeuticas well as diagnosticapplications  Diagnostic practice  Small amounts of radioactive chemicals, called ‘tracers’ (or radio-pharmaceuticals),  Injected into an arm vein or administered through ingestion or inhalation   Amount of radioactivity at different points within the patient’s body, or in body fluids  Then examined by radiation detectors 5   KA –MIT –Unit III –March, 2018, Sastra, Deemed University Radio Isotopes in Medical Diagnosis  Detector    Amount of radioactivity can be measured within parts of organs as well as within the whole organ  Measurement of the uptake of radioactive iodine by the thyroid gland  Rate of uptake of iodine by the thyroid  Greatly increased in patients with disease characterizedby increased production of thyroid hormone (hyperthyroidism)  Disease that led to nervousness, tremor, weight loss and, in extreme cases, even death 6   KA –MIT –Unit III –March, 2018, Sastra, Deemed University Radio Isotopes in Medical Diagnosis  Decreased iodine uptake (hypothyroidism) by the thyroid  Had symptoms and signs of diminished thyroid function  Thyroid gland continues to be the organ most frequently examined by nuclear medicine  Imaging of organ functions is carried out non-invasively  Nuclear medical examination approach is primarily function-oriented  Vital processes such as blood circulation, metabolism and vitality of organs and tumourscan be displayed as functional images 7   KA –MIT –Unit III –March, 2018, Sastra, Deemed University Radio Isotopes in Medical Diagnosis  Radio-nuclide imaging depends on  Obtaining a suitable distribution of the radio-nuclide in the patient  Radio-nuclide is labelled to a compound  Which will be taken up or metabolized in some way by the human tissue to be studied  Patient receives the material, usually by intravenous injection   After a suitable delay, which may be minutes or hours to   Allow uptake in the target tissues and clearance from the blood, imaging can commence  Each taking 2–10 minutes 8  4/10/20183 KA –MIT –Unit III –March, 2018, Sastra, Deemed University Radio Isotopes in Medical Diagnosis  Dynamic studies can be performed with the gamma camera  Moment of injection and capturing frames of the data either photographically or digitally   At times ranging from minutes down to fractions of a second  Data can produce useful information on organ function, blood flow, clearance rates, etc 9KA –MIT –Unit III –March, 2018, Sastra, Deemed University Radio Isotopes in Medical Diagnosis  Tecnetium-99m (Tc-99m) -radio-nuclide used to  Examine the brain, liver, lungs, bones, thyroid, kidney and heart  Tecnetium-99m (Tc-99m)  Metastable nuclear isomer of technetium-99 (itself an isotope of technetium), symbolized as 99m Tc  That is used in tens of millions of medical diagnostic procedures annually  Emits readily detectable gamma rays with a photon energy of 140 keV (these 8.8 pm photons are about the same wavelength as emitted by conventional X-ray diagnostic equipment)  Half-life for gamma emission is 6.0058 hours 10   KA –MIT –Unit III –March, 2018, Sastra, Deemed University Radio Isotopes in Medical Diagnosis  TC-99m cannot be coupled with all required biologically active substances  So that with this radio-nuclide the spectrum of radio-pharmaceuticals for examinations of the organ metabolism is limited  Iodine-123 labelled substances  Which are used in many clinical examinations  Iodine-123 ( 123 I or I-123)  Half-life is 13.22 hours  Predominant energy of 159 keV(this is the gamma primarily used for imaging) 11   KA –MIT –Unit III –March, 2018, Sastra, Deemed University Radiation Detectors 12  4/10/20184 KA –MIT –Unit III –March, 2018, Sastra, Deemed University Radiation Detectors  Depending upon the radiation emitted by the radio isotope of the radiopharmaceutical   A suitable detector is selected and operated under optimum conditions  Radiation falls on a photographic plate  It would cause darkening when developed after exposure  Photographic method is useful for measuring the total exposure to radiation of workers 13KA –MIT –Unit III –March, 2018, Sastra, Deemed University Radiation Detectors  Ionization chamber   Geiger Muller Counter   Proportional Counter   Semiconductor detectors  Solid state detectors 14KA –MIT –Unit III –March, 2018, Sastra, Deemed University Ionization Chamber   When an atom is ionized  It forms an ion pair   If the electrons are attracted towards a positively charged electrode  Positive ions to a negatively charged electrode, a current would flow in an external circuit  Principle of the ionizing chamber   Magnitude of the current would be proportional to the amount of radioactivity present between the electrodes 15   KA –MIT –Unit III –March, 2018, Sastra, Deemed University Ionization Chamber   Chamber which is filled with gas and is provided with two electrodes  Very high insulation resistance used as the insulation between the inner and outer electrodes of the ion chamber   Polytetrafluoroethylene  Potential difference of a few hundred volts is applied between the two electrodes  Radioactive source is placed inside or very dose to the chamber  16
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