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Encyclopedia > Nuclear medicine
Shown above is the bone scintigraphy of a young woman.
Shown above is the bone scintigraphy of a young woman.

Nuclear medicine, in short is nuclear study used in medecine to cure varying illnesses and to diagnose parts of the body such as liver, brain, thyroid,skeletal system and such. Nuclear medicine is a branch of medicine and medical imaging that uses the nuclear properties of matter in diagnosis and therapy. Many procedures in nuclear medicine use pharmaceuticals that have been labeled with radionuclides (radiopharmaceuticals). In diagnosis, radioactive substances are administered to patients and the radiation emitted is measured. The majority of these diagnostic tests involve the formation of an image using a gamma camera. Imaging may also be referred to as radionuclide imaging or nuclear scintigraphy. Other diagnostic tests use probes to acquire measurements from parts of the body, or counters for the measurement of samples taken from the patient. In therapy, radionuclides are administered to treat disease or provide palliative pain relief. For example, administration of Iodine-131 is often used for the treatment of thyrotoxicosis and thyroid cancer. Image File history File linksMetadata Download high-resolution version (2875x2198, 865 KB) Description Scintigraphie (Gamma caméra) du squelette humain dune jeune femme (lésion visible sous lorbite droite). ... Image File history File linksMetadata Download high-resolution version (2875x2198, 865 KB) Description Scintigraphie (Gamma caméra) du squelette humain dune jeune femme (lésion visible sous lorbite droite). ... medicines, see Medication. ... Medical imaging designates the ensemble of techniques and processes used to create images of the human body (or parts thereof) for clinical purposes (medical procedures seeking to reveal, diagnose or examine disease) or medical science (including the study of normal anatomy and function). ... Pharmacology (in Greek: pharmacon is drug, and logos is science) is the study of how chemical substances interfere with living systems. ... A radiopharmaceutical is a radioactive pharmaceutical. ... A patient having his blood pressure taken by a doctor. ... Radiation hazard symbol. ... Diagrammatic cross section of a gamma camera detector A gamma camera is an imaging device, most commonly used as a medical imaging device in nuclear medicine. ... Palliative care (from Latin palliare, to cloak) is any form of medical care or treatment that concentrates on reducing the severity of disease symptoms or slowing the diseases progress, rather than providing a cure. ... Iodine-131 (131I), also called radioiodine, is a radioisotope of iodine. ... Hyperthyroidism (thyrotoxicosis or fast thyroid gland) is the clinical syndrome caused by an excess of circulating free thyroxine (T4) and free triiodothyronine (T3), or both. ... Thyroid cancer is malignant growth of the thyroid gland. ...


Nuclear medicine differ from most other imaging modalities in that the tests primarily show the physiological function of the system being investigated as opposed to the anatomy. In some centres, the nuclear medicine images can be superimposed on images from modalities such as CT or MRI to highlight which part of the body the radiopharmaceutical is concentrated in. This practice is often referred to as image fusion or co-registration. This article or section does not cite any references or sources. ... Human heart and lungs, from an older edition of Grays Anatomy. ... It has been suggested that Synchrotron X-ray tomographic microscopy, X-ray tomography be merged into this article or section. ... Magnetic Resonance Image showing a median sagittal cross section through a human head. ...


Nuclear medicine diagnostic tests are usually provided by a dedicated department within a hospital and may include facilities for the preparation of radiopharmaceuticals. The specific name of a department can vary from hospital to hospital, with the most common names being the nuclear medicine department and the radioisotope department. For the record label, see Hospital Records. ...

Contents

Diagnostic testing

Diagnostic tests in nuclear medicine exploit the way that the body handles substances differently when there is disease or pathology present. The radionuclide introduced into the body is often chemically bound to a complex that acts characteristically within the body; this is commonly known as a tracer. In the presence of disease, a tracer will often be distributed around the body and/or processed differently. For example, the ligand methylene-diphosphonate (MDP) can be preferentially taken up by bone. By chemically attaching technetium-99m to MDP, radioactivity can be transported and attached to bone via the hydroxyapatite for imaging. Any increased physiological function, such as due to a fracture in the bone, will usually mean increased concentration of the tracer. This often results in the appearance of a 'hot-spot' which is a focal increase in radio-accumulation, or a general increase in radio-accumulation throughout the physiological system. Some disease processes result in the exclusion of a tracer, resulting in the appearance of a 'cold-spot'. Many tracer complexes have been developed in order to image or treat many different organs, glands, and physiological processes. The types of tests can be split into two broad groups: in-vivo and in-vitro: Synthesis of copper(II)-tetraphenylporphine, a metal complex, from tetraphenylporphine and copper(II) acetate monohydrate. ... In chemistry, a ligand is an atom, ion, or molecule (see also: functional group) that generally donates one or more of its electrons through a coordinate covalent bond to, or shares its electrons through a covalent bond with, one or more central atoms or ions (these ligands act as a... Drawing shows patient lying on a table that slides under the scanner, a technician operating the scanner, and a monitor that will show images made during the scan. ... Hydroxylapatite is a naturally occurring form of calcium apatite with the formula Ca5(PO4)3(OH), but is usually written Ca10(PO4)6(OH)2 to denote that the crystal unit cell comprises two molecules. ... In biology, an organ (Latin: organum, instrument, tool) is a group of tissues that perform a specific function or group of functions. ... Human submaxillary gland. ... In vivo (Latin for (with)in the living). ... Wiktionary has a definition of: In vitro In vitro (Latin: within glass) means within a test tube, or, more generally, outside a living organism or cell. ...

  • In-vivo tests are measurements directly involving the patient. By far the most common are gamma camera imaging investigations, though non-imaging probes are also used to measure the levels of radioactivity within a patient.
  • In-vitro tests are measurements of samples taken from the patient (e.g. blood, urine, breath).

Types of studies

A typical nuclear medicine study involves administration of a radionuclide into the body by injection in liquid or aggregate form, ingestion while combined with food, inhalation in gaseous form or, rarely, injection of a radionuclide that has undergone micro-encapsulation. Some specialist studies require the labeling of a patient's own cells with a radionuclide (leukocyte scintigraphy and red cell scintigraphy). Most diagnostic radionuclides emit gamma rays, while the cell-damaging properties of beta particles are used in therapeutic applications. Refined radionuclides for use in nuclear medicine are derived from fission or fusion processes in nuclear reactors, which produce radioisotopes with longer half-lives, or cyclotrons, which produce radioisotopes with shorter half-lives, or take advantage of natural decay processes in dedicated generators, i.e. Molybdenum/Technetium or Strontium/Rubidium. A radionuclide is an atom with an unstable nucleus, which is a nucleus characterized of excess energy which is available to be imparted either to a newly-created radiation particle within the nucleus, or else to an atomic electron (see internal conversion) . The radionuclide, in this process, undergoes radioactive decay... This article or section cites very few or no references or sources. ... White Blood Cells is also the name of a White Stripes album. ... Nuclear medicine is the branch of medicine that uses unsealed radioactive substances in diagnosis and therapy. ... Human red blood cells Red blood cells are the most common type of blood cell and the vertebrate bodys principal means of delivering oxygen from the lungs or gills to body tissues via the blood. ... This article is about electromagnetic radiation. ... Beta particles are high-energy electrons emitted by certain types of radioactive nuclei such as potassium-40. ... For the generation of electrical power by fission, see Nuclear power plant An induced nuclear fission event. ... Core of a small nuclear reactor used for research. ... A pair of Dee electrodes with loops of coolant pipes on their surface at the Lawrence Hall of Science. ...


The most commonly used liquid radionuclides are:

The most commonly used gaseous/aerosol radionuclides are: General Name, Symbol, Number technetium, Tc, 43 Chemical series transition metals Group, Period, Block 7, 5, d Appearance silvery gray metal Standard atomic weight [98](0) g·mol−1 Electron configuration [Kr] 4d5 5s2 Electrons per shell 2, 8, 18, 13, 2 Physical properties Phase solid Density (near r. ... A nuclear isomer is a metastable state of an atom caused by the excitation of a proton or neutron in its nucleus so that it requires a change in spin before it can release its extra energy. ... Technetium-99m is a metastable nuclear isomer of technetium-99, symbolized as 99mTc. ... General Name, Symbol, Number iodine, I, 53 Chemical series halogens Group, Period, Block 17, 5, p Appearance violet-dark gray, lustrous Standard atomic weight 126. ... General Name, Symbol, Number thallium, Tl, 81 Chemical series poor metals Group, Period, Block 13, 6, p Appearance silvery white Atomic mass 204. ... General Name, Symbol, Number gallium, Ga, 31 Chemical series poor metals Group, Period, Block 13, 4, p Appearance silvery white   Standard atomic weight 69. ... General Name, Symbol, Number fluorine, F, 9 Chemical series halogens Group, Period, Block 17, 2, p Appearance Yellowish brown gas Atomic mass 18. ... General Name, Symbol, Number indium, In, 49 Chemical series poor metals Group, Period, Block 13, 5, p Appearance silvery lustrous gray Standard atomic weight 114. ...

General Name, Symbol, Number xenon, Xe, 54 Chemical series noble gases Group, Period, Block 18, 5, p Appearance colorless Standard atomic weight 131. ... General Name, Symbol, Number krypton, Kr, 36 Chemical series noble gases Group, Period, Block 18, 4, p Appearance colorless Standard atomic weight 83. ...

Imaging equipment

Diagrammatic cross section of gamma camera detector

The radiation emitted from the radionuclide inside the body is usually detected using a gamma camera. Traditionally, gamma-cameras have consisted of a gamma-ray detector, such as a single large thallium-doped sodium iodide NaI(Tl) scintillation crystal, coupled with an imaging sub-system such as an array of photomultiplier tubes and associated electronics. Solid-state gamma-ray detectors are available[1], but are not yet commonplace. Gamma-cameras employ lead or tungsten collimators to form an image on the crystal, accepting photons arriving perpendicular to the camera face, and rejecting off-axis photons which would degrade the desired image. Image File history File links Gamma_camera_cross_section. ... Image File history File links Gamma_camera_cross_section. ... Diagrammatic cross section of a gamma camera detector A gamma camera is an imaging device, most commonly used as a medical imaging device in nuclear medicine. ... A scintillator is a device or substance that absorbs high energy (ionizing) electromagnetic or charged particle radiation then, in response, fluoresces photons at a characteristic Stokes-shifted (longer) wavelength, releasing the previously absorbed energy. ... Photomultipliers, or photomultiplier tubes (PMT) are extremely sensitive detectors of light in the ultraviolet, visible and near infrared. ... Semiconductor devices are electronic components that exploit the electronic properties of semiconductor materials, principally silicon, germanium, and gallium arsenide. ... How a lead collimator filters a stream of rays. ...


Gamma-camera performance is usually a balance of spatial resolution against sensitivity. A typical gamma-camera will have a resolution of 4 to 6 mm and will be able to capture several hundred thousand gamma-ray 'events' per second. The gamma-camera detects the X and Y position of each gamma-ray event, using these coordinates to place a pixel in an image matrix to build a recognisable image. The units of a raw nuclear medicine image are 'counts' or 'kilocounts', referring to the number of gamma-ray events detected. In nuclear medicine, the value of an image pixel is the integral of gamma-ray events in that pixel position over time. That is, the pixel appears brighter as more counts are detected in that position. In non-tomographic images, the pixel can also be thought of as the line integral of radionuclide distribution of a perpendicular line extending from the pixel position through the body of the patient. Activity closer to the camera face will produce more information in the image than activity located deeper in the body, however, because of attenuation by tissues between the radionuclide event and the camera face. Tomographic imaging applies similar principles, taking multiple planar images from different angles and then refining them using a process known as filtered back projection generating three dimensional views of organs or areas of interest.


Since each nuclear medicine radionuclide has a unique gamma-ray emission energy spectrum, and since the energy of a gamma-ray is detected in a gamma-camera by the brightness of the scintillation associated with an event, gamma-cameras employ energy 'windows' to gate or limit the imaging process to gamma-ray events of particular energies. An energy window is usually tailored to the peak, most often with a plus or minus ten percent window, of the energy spectrum of a particular radionuclide, thus ignoring other gamma-rays that would otherwise contribute noise to the image. This allows noise caused by Compton scattering to be gated out. For the Irish mythological figure, see Naoise. ... In physics, Compton scattering or the Compton effect, is the decrease in energy (increase in wavelength) of an X-ray or gamma ray photon, when it interacts with matter. ...


Analysis

The end result of the nuclear medicine imaging process is a "dataset" comprising one or more images. In multi-image datasets the array of images may represent a time sequence (ie. cine or movie) often called a "dynamic" dataset, a cardiac gated time sequence, or a spatial sequence where the gamma-camera is moved relative to the patient. SPECT (single photon emission computed tomography) is the process by which images acquired from a rotating gamma-camera are reconstructed to produce an image of a "slice" through the patient at a particular position. A collection of parallel slices form a slice-stack, a three-dimensional representation of the distribution of radionuclide in the patient. Single photon emission computed tomography (SPECT) is a nuclear medicine tomographic imaging technique using gamma rays. ... 3D computer graphics are different from 2D computer graphics in that a three-dimensional representation of geometric data is stored in the computer for the purposes of performing calculations and rendering 2D images. ...


The nuclear medicine computer may require millions of lines of source code to provide quantitative analysis packages for each of the specific imaging techniques available in nuclear medicine,


Radiation dose

A patient undergoing a nuclear medicine procedure will receive a radiation dose. Under present international guidelines it is assumed that any radiation dose, however small, presents a risk. The radiation doses delivered to a patient in a nuclear medicine investigation present a very small risk of inducing cancer. In this respect it is similar to the risk from X-ray investigations except that the dose is delivered internally rather than externally.


The radiation dose from a nuclear medicine investigation is expressed as an effective dose with units of sieverts (usually given in millisieverts, mSv). The effective dose resulting from an investigation is influenced by the amount of radioactivity administered in megabecquerels (MBq), the physical properties of the radiopharmaceutical used, its distribution in the body and its rate of clearance from the body. In pharmacology an effective dose is the amount of drug that produces a therapeutic response in 50% of the people taking it. ... The sievert (symbol: Sv) is the SI derived unit of dose equivalent. ... The becquerel (symbol Bq) is the SI derived unit of radioactivity, defined as the activity of a quantity of radioactive material in which one nucleus decays per second. ... Half-Life For a quantity subject to exponential decay, the half-life is the time required for the quantity to fall to half of its initial value. ... A radiopharmaceutical is a radioactive pharmaceutical. ...


Effective doses can range from 6 μSv (0.006 mSv) for a 3 MBq chromium-51 EDTA measurement of glomerular filtration rate to 37 mSv for a 150 MBq thallium-201 non-specific tumour imaging procedure. The common bone scan with 600 MBq of technetium-99m-MDP has an effective dose of 3 mSv (1). General Name, Symbol, Number chromium, Cr, 24 Chemical series transition metals Group, Period, Block 6, 4, d Appearance silvery metallic Standard atomic weight 51. ... General Name, Symbol, Number thallium, Tl, 81 Chemical series poor metals Group, Period, Block 13, 6, p Appearance silvery white Atomic mass 204. ...


See also

Medical imaging designates the ensemble of techniques and processes used to create images of the human body (or parts thereof) for clinical purposes (medical procedures seeking to reveal, diagnose or examine disease) or medical science (including the study of normal anatomy and function). ... Image A: A normal chest X-ray. ... Image of a typical positron emission tomography (PET) facility Positron emission tomography (PET) is a nuclear medicine medical imaging technique which produces a three-dimensional image or map of functional processes in the body. ... SPECT (Single Photon Emission Computed Tomography) is a nuclear medicine tomographic imaging technique using gamma rays. ... Diagrammatic cross section of a gamma camera detector A gamma camera is an imaging device, most commonly used as a medical imaging device in nuclear medicine. ... It has been suggested that Chalk river unidentified deposits be merged into this article or section. ... This article is in need of attention. ... Therac-25 was a radiation therapy machine produced by Atomic Energy of Canada Limited. ... A Radionuclide cisternogram is medical test which involves injecting a tracer through a needle into a patients cerebral spinal fluids (CSF) to check to see if it is flowing properly, or determine if there is a leak (also known as a CSF fistula) from the brain into the nasal... A radionuclide is an atom with an unstable nucleus, which is a nucleus characterized of excess energy which is available to be imparted either to a newly-created radiation particle within the nucleus, or else to an atomic electron (see internal conversion) . The radionuclide, in this process, undergoes radioactive decay...

Reference

1. Notes for guidance on the clinical administration of radiopharmaceuticals and use of sealed radioactive sources. Administration of radioactive substances committee UK 1998.


External links

  • RadiologyInfo.org - The radiology information resource for patients: Nuclear Medicine
  • uic.com.au Uranium Information Center "Radioisotopes in Medicine: Nuclear Issues Briefing Paper 26", February 2006. A nice primer.
  • Nucmedinfo "Nuclear Medicine Information"
  • idoimaging.com - Free software for viewing and converting medical imaging files in NM and other modalities.
  • NucMe.com Nuclear medicine information for technologists and students

  Results from FactBites:
 
Nuclear medicine - Wikipedia, the free encyclopedia (1335 words)
Nuclear medicine is a branch of medicine and medical imaging that uses unsealed radioactive substances in diagnosis and therapy.
Nuclear medicine diagnostic tests are usually provided by a dedicated department within a hospital and may include facilities for the preparation of radiopharmaceuticals.
Since each nuclear medicine radionuclide has a unique gamma-ray emission energy spectrum, and since the energy of a gamma-ray is detected in a gamma-camera by the brightness of the scintillation associated with an event, gamma-cameras employ energy 'windows' to gate or limit the imaging process to gamma-ray events of particular energies.
Nuclear Medicine (747 words)
Nuclear medicine is a specialized area of radiology that uses very small amounts of radioactive materials, or radiopharmaceuticals, to examine organ function and structure.
Nuclear medicine imaging is a combination of many different disciplines, including chemistry, physics, mathematics, computer technology, and medicine.
Nuclear imaging examines organ function and structure, whereas diagnostic radiology is based on anatomy.
  More results at FactBites »

 
 

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