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Nuclear medicine scan.ppt
- 2. Created by Students AbdulAzizAlMahmoud AbdulRahman AlZaydi Abdullah AlWeleyi
- 3. Contents: First Speaker (AbdulAzizAlMahmoud) A. Introduction B. Radiopharmaceuticals Second Speaker (AbdulRahman AlZaydi) C. Gamma Camera Third Speaker (Abdullah AlWeleyi) D. Single Photon Emission Computed Tomography (SPECT) E. Conclusion
- 4. What is radiation? Radiationis a type of energy, which exists in our environment in many forms and comes from both natural and man-made sources. Light that allows us to see and the warmth we get from the sun or from nature are natural forms of radiation.
- 5. e.g. of man-maderadiation include the microwave radiation that is used for cooking and radio waves for communication over long distances ionizing radiation comes from both natural and man-made sources.
- 6. What is nuclearmedicine ? This is a branch of medicine that uses radiation from radioactive tracers to provide information about the function of specific organs. In some cases, radioactivity can be used to treat certain conditions such as an overactive thyroid.
- 7. Follow.. Nuclear medicinestudies use ionizing radiation, as do x-ray studies. radioactive tracers or radiopharmaceuticals commonly used are quickly eliminated from the body through its natural functions. In addition, the tracers used rapidly lose their radioactivity. In most cases, the dose of radiation necessary for a scan is very small. For example, a patient having a lung scan is exposed to the same dose of radiation they would receive from eight return air flights between Sydney and London.
- 8. What is pharmaceutical? The radioactive materials administered to patients are known as radiopharmaceuticals. These consist of : Chemical molecule which determines the behavior of the radiopharmaceutical in the body a radionuclide. The radiation emitted by the radionuclide may be detected from outside the body by a radionuclide imaging device (a gamma camera) or may be detected In a sample of a body fluid (e.g. plasma or urine)
- 9. Radiopharmaceuticals Diagnostic radiopharmaceuticals must deliverthe minimum possible radiation dose to the patient while still obtaining the required diagnostic information. Therapy radiopharmaceuticals must deliver the maximum radiation dose to the diseased organ or tumor, while minimizing the radiation dose to non target tissues such as the bone marrow. Ensure minimal irradiation of other parts.
- 10. What is ahalf-life? Nuclear medicines used for diagnosis or treatment generally have short half- lives. A half-life is the time it takes for the level of radioactivity to drop to half the starting level. Nuclear medicines typically have a half-life of several hours or days. This means they rapidly lose their radioactivity level within the predetermined half-life.
- 11. GAMMA CAMERA 1-Principle: The Gamma or Scintillation Camera is an imaging device that is most commonly used in nuclear medicine. It is also called the Anger Camera. Gamma Cameras detect radiation from the entire field of view simultaneously and therefore are capable of recording dynamic as well as static images of the area of interest in the patient. The gamma cameras usually consists of several components: a detector, a collimator, PM tube, a preamplifier, an amplifier, a pulsed-height analyzer (PHA), an X-, Y-positioning circuit, and display or recording device.
- 15. GAMMA CAMERA 2-Operation: The gammarays emitted by the radiopharmaceutical (in the patient) are first collimated (by a specific collimator) and then detected by a detector (usually scintillator)
- 17. Single Photon Emission ComputedTomography (SPECT) Tomograms: a series of views (profiles) are acquired at different angles around Filters: Fourier transform "Sampling and correction
- 18. (SPECT) SPECT isalso widely used and the process of injecting a radioactive tracer is the same as the PLANAR technique. Instead of being stationary, the gamma camera moves around the body providing a series of images. This takes about 20-30 minutes. SPECT and PLANAR imaging are highly convenient technologies as they use radiopharmaceuticals, which can be easily distributed, stored and mixed ready for use at nuclear medicine clinics and hospitals.
- 20. Collimator A collimatoris a device that narrows a beam of particles or waves. To "narrow" can mean either to cause the directions of motion to become more aligned in a specific direction (i.s., collimated or parallel) or to cause the spatial cross section of the beam to become smaller. Gamma rays are emitted isotropically (in all directions) Using only a detector would not result in an image because there will be no relationship between the position at which the gamma rays hit the detector and the origin of the gamma rays (in the patient)
- 24. Detector Detector, by whichincrease the thickness of a detector increase probability of Complete absorption of gamma ray. Detector are used in gamma camera, but this decrease the sensitivity Of the camera, because many gamma rays () may escape from the detector without interaction.
- 25. Detector ٠Spatial resolution:the smallest separation required between two small objects to be detected and distinguished as two separated objects ٠Energy resolution: bill width half maximum (FWHM) ٠Non-Uniformity: the slightly different response of different areas of the detector of the camera to a uniform radioactive source ٠Spatial distortion: random or systematic error of determining event location ٠Counting-rate: counts / unit of time. It is assessed as the Observed count-rate (gamma camera) vs. True count-rate (source activity) ٠Sensitivity: count-rate / unit of radioactivity
- 26. References: Books: 1_Nuclrear Medicine andPET/CT, sixth edition. 2_The Essential Physics of Medical Imaging, third edition. 3-Physics Radiobiology of Nuclear Medicine, third edition. Others: 1_Nuclear Medicine.ppt 2_Introduction to Nuclear Medicine.ppt 3_Imaging with Radionuclides.ppt
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Editor's Notes
- #5 " In radionuclide imaging (nuclear medicine) clinical data is derived from observing the distribution of a pharmaceutical administrated to the patient
- #6 " By incorporating a radionuclide into the pharmaceutical, measurements can be made of the distribution of this radiopharmaceutical by noting the amount of radioactivity present " These measurements may be carried out either in-vivo or in-vitro
- #7 " In vivo imaging is the most common type of procedure in nuclear medicine " It offers the potential, unique among all other imaging techniques, of demonstrating hmction rather than simply anatomy " It is usually carried out with the so-called gamma camera " In vitro measurements are made on samples of materials taken from the patient, such as urine, to determine the amount of the radioactivity present
- #10 ٠ Half life: how quickly the radioactivity will decay - Too short: the activity will have significantly decay before imaging has started - Too long: the patient will remain radioactive for a considerable time after the examination - Roughly, the half life should of a similar length of that of the exam (few hrs) (99mTc has a half life of 6 hrs) ٠ Type and energy of emission: - The higher the energy of the radiation the higher is the penetration, but - The more difficult to be stopped (detected) by the gamma camera - Ideally, 150 keV is preferred (99mTc emits 140 keV gamma ray) - It is necessary to avoid those radionuclides which have a and p emissions
- #11 ٠ Pharmaceutical labelling: it is the incorporation of the radionuclide with a pharmaceutical: - Thus, the radionuclide should be chemically suitable for labling. This is not easy to achieve as all the elements of biological interest, such as C, O, N have radioisotopes which do not meet the criteria above but instead emit positron - 99mTc has been successfully incorporated into (labelled with) a large range of pharmaceuticals ٠ Production of radionuclides: - The short-lived radionuclides produced by either reactor or cyclotron will decay significantly during transportation (to the hospital) - The third mode pf production, the generator, which used to produce 99mTc, provides the answer to the transportation problem
- #12 1. Principle ٠ The gamma camera is the principal instrument for imaging in nuclear medicine ٠ It consists of a large detector in front of which the patient is positioned ٠ Dual- and triple- detector gamma camera are also available ٠ The camera are controlled by computer which allow the operator to do the necessaty settings such as: - The study acquisition time or the number of counts to be acquired - The pulse height analysers (PHAs) to reject scattered radiation - The display mode: soft-copy and/or hard-copy (photographic film)
- #13 1. Principle ٠ The gamma camera is the principal instrument for imaging in nuclear medicine ٠ It consists of a large detector in front of which the patient is positioned ٠ Dual- and triple- detector gamma camera are also available ٠ The camera are controlled by computer which allow the operator to do the necessaty settings such as: - The study acquisition time or the number of counts to be acquired - The pulse height analysers (PHAs) to reject scattered radiation - The display mode: soft-copy and/or hard-copy (photographic film)
- #14 1. Principle ٠ The gamma camera is the principal instrument for imaging in nuclear medicine ٠ It consists of a large detector in front of which the patient is positioned ٠ Dual- and triple- detector gamma camera are also available ٠ The camera are controlled by computer which allow the operator to do the necessaty settings such as: - The study acquisition time or the number of counts to be acquired - The pulse height analysers (PHAs) to reject scattered radiation - The display mode: soft-copy and/or hard-copy (photographic film)
- #15 1. Principle ٠ The gamma camera is the principal instrument for imaging in nuclear medicine ٠ It consists of a large detector in front of which the patient is positioned ٠ Dual- and triple- detector gamma camera are also available ٠ The camera are controlled by computer which allow the operator to do the necessaty settings such as: - The study acquisition time or the number of counts to be acquired - The pulse height analysers (PHAs) to reject scattered radiation - The display mode: soft-copy and/or hard-copy (photographic film)
- #16 ٠ The gamma rays emitted by the radiopharmaceutical (in the patient) are first collimated (by a specific collimator) and then detected by a detector (usually scintillator) ٠ At the detector, the gamma rays are converted into visible light by the scintillation crystals ٠ This light is, in turn, transformed into electronic signals by an array of photomultiplier tubes (PMT) placed at the rear face of the crystals ٠ The output from the PMT is converted into three signals: X and Y (gives the spatial location of the scintillation) and Z which represents the energy deposited in the crystal ٠ The Z-signal passes through a pulse height analyzer (PHA) to check whether the energy is within the range of interest before display
- #17 ٠ The gamma rays emitted by the radiopharmaceutical (in the patient) are first collimated (by a specific collimator) and then detected by a detector (usually scintillator) ٠ At the detector, the gamma rays are converted into visible light by the scintillation crystals ٠ This light is, in turn, transformed into electronic signals by an array of photomultiplier tubes (PMT) placed at the rear face of the crystals ٠ The output from the PMT is converted into three signals: X and Y (gives the spatial location of the scintillation) and Z which represents the energy deposited in the crystal ٠ The Z-signal passes through a pulse height analyzer (PHA) to check whether the energy is within the range of interest before display
- #18 "Tomograms: a series of views (profiles) are acquired at different angles around the patient "Back-projection: reconstructs each profile at the appropriate angle " Filters: Fourier transform "Sampling and correction
- #21 ٠ Gamma rays are emitted isotropically (in all directions) ٠ Using only a detector would not result in an image because there will be no relationship between the position at which the gamma rays hit the detector and the origin of the gamma rays (in the patient) ٠ Therefore, a collimator must be employed ٠ The typical collimator consists of a lead plate through which runs an array of small holes ٠ Only those gamma rays which travel a long a hole axis will pass into the scintillation crystals, while the angled radiation will be absorbed by the lead
- #22 ٠ The two parameters describing collimator performance are: - Spatial resolution: the minimum separation needed between two small objects if they are to be distinguished (typically: 7mm) - Sensitivity: the proportion of those gamma rays incident on the collimator which pass through to the detector (typically: 0.1%) ٠ The performance of the collimator depends upon its dimensions ٠ It is not possible to optimise the both two parameters of a collimator ٠ The choice must be made depending upon the type of investigation ٠ Also different collimators are available for the deferent energy used - low energy: < 140 keV - Medium energy: < 260 keV - High energy: < 400 keV
- #23 " However, there are different types of collimator, based on sensitivity, resolution and energy: - Low energy - high resolution - Low energy - general purposes - Low energy - high sensitivity - Medium energy - general purposes - High energy - general purposes
- #24 3. Collimator ٠ Also, collimator is classified based on its design into four types: - Parallel-hole collimator: used for most studies - Converging collimator: for magnification - Diverging collimator: to minify a large object - Pin-hole collimator: a lead cone with a small hole for small object e.g. thyroid gland
- #25 " While the collimator modifies the gamma ray flux so as to create an image, it is the fltnction of the detector to convert the gamma rays into a usefltl image " This can be done in two stages: - The first stage is the conversion of the gamma rays into visible light by means of a scintillation crystals which is usually made of sodium iodide with thallium added NaI(Tl) - The second stage is these scintillations are turned into electrical signal by the PMTs
- #26 " The effectiveness of NaI(Tl) at stopping the gamma rays (the efficiency) depends not only on its density and Z number but also on the thickness of ctystal used " The scintillator ctystals are the most expensive part of the gamma camera " However, scintillation detector has lower energy resolution than the semiconductor detectors " These detectors need, however, cooling system