Scintigraphy
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Scintigraphy (from Latin ''scintilla'', "spark"), also known as a gamma scan, is a diagnostic test in
nuclear medicine Nuclear medicine or nucleology is a medical specialty involving the application of radioactive substances in the diagnosis and treatment of disease. Nuclear imaging, in a sense, is "radiology done inside out" because it records radiation emit ...
, where
radioisotope A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...
s attached to drugs that travel to a specific organ or tissue (
radiopharmaceuticals Radiopharmaceuticals, or medicinal radiocompounds, are a group of pharmaceutical drugs containing radioactive isotopes. Radiopharmaceuticals can be used as diagnostic and therapeutic agents. Radiopharmaceuticals emit radiation themselves, which is ...
) are taken internally and the emitted
gamma radiation A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically s ...
is captured by external detectors (
gamma camera A gamma camera (γ-camera), also called a scintillation camera or Anger camera, is a device used to image gamma radiation emitting radioisotopes, a technique known as scintigraphy. The applications of scintigraphy include early drug development ...
s) to form two-dimensional images in a similar process to the capture of
x-ray images Radiography is an imaging technique using X-rays, gamma rays, or similar ionizing radiation and non-ionizing radiation to view the internal form of an object. Applications of radiography include medical radiography ("diagnostic" and "therapeut ...
. In contrast, SPECT and ''
positron emission tomography Positron emission tomography (PET) is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes, and in other physiological activities including blood flow, ...
'' (PET) form 3-dimensional images and are therefore classified as separate techniques from scintigraphy, although they also use
gamma camera A gamma camera (γ-camera), also called a scintillation camera or Anger camera, is a device used to image gamma radiation emitting radioisotopes, a technique known as scintigraphy. The applications of scintigraphy include early drug development ...
s to detect internal radiation. Scintigraphy is unlike a diagnostic X-ray where external radiation is passed through the body to form an image.


Process

Scintillography is an
imaging Imaging is the representation or reproduction of an object's form; especially a visual representation (i.e., the formation of an image). Imaging technology is the application of materials and methods to create, preserve, or duplicate images. ...
method of nuclear events provoked by
collision In physics, a collision is any event in which two or more bodies exert forces on each other in a relatively short time. Although the most common use of the word ''collision'' refers to incidents in which two or more objects collide with great fo ...
s or charged current interactions among nuclear particles or ionizing radiation and
atom Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas ...
s which result in a brief, localised pulse of
electromagnetic radiation In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible ...
, usually in the
visible light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...
range ( Cherenkov radiation). This pulse (
scintillation Scintillation can refer to: *Scintillation (astronomy), atmospheric effects which influence astronomical observations *Interplanetary scintillation, fluctuations of radio waves caused by the solar wind *Scintillation (physics), a flash of light pro ...
) is usually detected and amplified by a
photomultiplier A photomultiplier is a device that converts incident photons into an electrical signal. Kinds of photomultiplier include: * Photomultiplier tube, a vacuum tube converting incident photons into an electric signal. Photomultiplier tubes (PMTs for s ...
or charged coupled device elements, and its resulting electrical waveform is processed by computers to provide two- and three-dimensional images of a subject or region of interest. Scintillography is mainly used in
scintillation camera A gamma camera (γ-camera), also called a scintillation camera or Anger camera, is a device used to image gamma radiation emitting radioisotopes, a technique known as scintigraphy. The applications of scintigraphy include early drug development ...
s in
experimental physics Experimental physics is the category of disciplines and sub-disciplines in the field of physics that are concerned with the observation of physical phenomena and experiments. Methods vary from discipline to discipline, from simple experiments and o ...
. For example, huge neutrino detection underground tanks filled with
tetrachloroethylene Tetrachloroethylene, also known under the systematic name tetrachloroethene, or perchloroethylene, and many other names (and abbreviations such as "perc" or "PERC", and "PCE"), is a chlorocarbon with the formula Cl2C=CCl2 . It is a colorless liq ...
are surrounded by arrays of photo detectors in order to capture the extremely rare event of a collision between the fluid's atoms and a
neutrino A neutrino ( ; denoted by the Greek letter ) is a fermion (an elementary particle with spin of ) that interacts only via the weak interaction and gravity. The neutrino is so named because it is electrically neutral and because its rest mass ...
. Another extensive use of scintillography is in medical imaging techniques which use
gamma ray A gamma ray, also known as gamma radiation (symbol γ or \gamma), is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nucleus, atomic nuclei. It consists of the shortest wavelength electromagnetic wav ...
detectors called
gamma camera A gamma camera (γ-camera), also called a scintillation camera or Anger camera, is a device used to image gamma radiation emitting radioisotopes, a technique known as scintigraphy. The applications of scintigraphy include early drug development ...
s. Detectors coated with materials which scintillate when subjected to gamma rays are scanned with optical photon detectors and
scintillation counter A scintillation counter is an instrument for detecting and measuring ionizing radiation by using the excitation effect of incident radiation on a scintillating material, and detecting the resultant light pulses. It consists of a scintillator w ...
s. The subjects are injected with special
radionuclide A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transfer ...
s which irradiate in the gamma range inside the region of interest, such as the
heart The heart is a muscular organ found in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon diox ...
or the
brain The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head ( cephalization), usually near organs for special ...
. A special type of gamma camera is the SPECT (Single Photon Emission Computed Tomography). Another medical scintillography technique, the Positron-emission tomography (PET), which uses the scintillations provoked by electron-positron annihilation phenomena.


By organ or organ system


Biliary system (cholescintigraphy)

Scintigraphy of the biliary system is called ''cholescintigraphy'' and is done to diagnose obstruction of the bile ducts by a gallstone (
cholelithiasis A gallstone is a stone formed within the gallbladder from precipitated bile components. The term cholelithiasis may refer to the presence of gallstones or to any disease caused by gallstones, and choledocholithiasis refers to the presence of mi ...
), a tumor, or another cause. It can also diagnose gallbladder diseases, e.g. bile leaks of biliary fistulas. In cholescintigraphy, the injected radioactive chemical is taken up by the liver and secreted into the bile. The radiopharmaceutical then goes into the bile ducts, the gallbladder, and the intestines. The gamma camera is placed on the abdomen to picture these perfused organs. Other scintigraphic tests are done similarly.


Lung scintigraphy

The most common indication for lung scintigraphy is to diagnose
pulmonary embolism Pulmonary embolism (PE) is a blockage of an artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream (embolism). Symptoms of a PE may include shortness of breath, chest pain particularly upon breathing ...
, e.g. with a ventilation/perfusion scan and may be appropriate for excluding PE in pregnancy. Less common indications include evaluation of
lung transplantation Lung transplantation, or pulmonary transplantation, is a surgical procedure in which one or both lungs are replaced by lungs from a donor. Donor lungs can be retrieved from a living or deceased donor. A living donor can only donate one lung lobe ...
, preoperative evaluation, evaluation of right-to-left shunts. In the ventilation phase of a ventilation/perfusion scan, a gaseous radionuclide
xenon Xenon is a chemical element with the symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...
or
technetium Technetium is a chemical element with the symbol Tc and atomic number 43. It is the lightest element whose isotopes are all radioactive. All available technetium is produced as a synthetic element. Naturally occurring technetium is a spontaneous ...
DTPA in an aerosol form (or ideally using Technegas, a radioaerosol invented in Australia by Dr Bill Burch and Dr Richard Fawdry) is inhaled by the patient through a mouthpiece or mask that covers the nose and mouth. The perfusion phase of the test involves the intravenous injection of radioactive technetium macro aggregated albumin (Tc99m-MAA). A gamma camera acquires the images for both phases of the study.


Bone

For example, the ligand methylene-diphosphonate (MDP) can be preferentially taken up by bone. By chemically attaching
technetium-99m Technetium-99m (99mTc) is a metastable nuclear isomer of technetium-99 (itself an isotope of technetium), symbolized as 99mTc, that is used in tens of millions of medical diagnostic procedures annually, making it the most commonly used medical r ...
to MDP, radioactivity can be transported and attached to bone via the
hydroxyapatite Hydroxyapatite, also called hydroxylapatite (HA), is a naturally occurring mineral form of calcium apatite with the formula Ca5(PO4)3(OH), but it is usually written Ca10(PO4)6(OH)2 to denote that the crystal unit cell comprises two entities ...
for imaging. Any increased physiological function, such as a fracture in the bone, will usually mean increased concentration of the tracer.


Heart

A ''thallium stress test'' is a form of scintigraphy, where the amount of
thallium Thallium is a chemical element with the symbol Tl and atomic number 81. It is a gray post-transition metal that is not found free in nature. When isolated, thallium resembles tin, but discolors when exposed to air. Chemists William Crookes a ...
-201 detected in cardiac tissues correlates with tissue blood supply. Viable cardiac cells have normal Na+/K+ ion exchange pumps. Thallium binds the K+ pumps and is transported into the cells. Exercise or
dipyridamole Dipyridamole (trademarked as Persantine and others) is a nucleoside transport inhibitor and a PDE3 inhibitor medication that inhibits blood clot formation when given chronically and causes blood vessel dilation when given at high doses over a ...
induces widening (
vasodilation Vasodilation is the widening of blood vessels. It results from relaxation of smooth muscle cells within the vessel walls, in particular in the large veins, large arteries, and smaller arterioles. The process is the opposite of vasoconstricti ...
) of normal coronary arteries. This produces coronary steal from areas of ischemia where arteries are already maximally dilated. Areas of infarct or ischemic tissue will remain "cold". Pre- and post-stress thallium may indicate areas that will benefit from myocardial
revascularization In medical and surgical therapy, revascularization is the restoration of perfusion to a body part or organ that has had ischemia. It is typically accomplished by surgical means. Vascular bypass and angioplasty are the two primary means of ...
. Redistribution indicates the existence of coronary steal and the presence of ischemic
coronary artery disease Coronary artery disease (CAD), also called coronary heart disease (CHD), ischemic heart disease (IHD), myocardial ischemia, or simply heart disease, involves Ischemia, the reduction of blood flow to the myocardium, heart muscle due to build-up o ...
.


Parathyroid

Tc99m- sestamibi is used to detect parathyroid adenomas.


Thyroid

To detect metastases/function of thyroid, the isotopes
technetium-99m Technetium-99m (99mTc) is a metastable nuclear isomer of technetium-99 (itself an isotope of technetium), symbolized as 99mTc, that is used in tens of millions of medical diagnostic procedures annually, making it the most commonly used medical r ...
or
iodine-123 Iodine-123 (123I) is a radioactive isotope of iodine used in nuclear medicine imaging, including single-photon emission computed tomography (SPECT) or SPECT/CT exams. The isotope's half-life is 13.2230 hours; the decay by electron capture to ...
are generally used, and for this purpose the iodide isotope does not need to be attached to another protein or molecule, because thyroid tissue takes up free iodide actively.


Renal and urinary systems


Full body

Examples are
gallium scan A gallium scan is a type of nuclear medicine test that uses either a gallium-67 (67Ga) or gallium-68 (68Ga) radiopharmaceutical to obtain images of a specific type of tissue, or disease state of tissue. Gallium salts like gallium citrate and gall ...
s, indium white blood cell scans, iobenguane scan (MIBG) and octreotide scans. The MIBG scan detects adrenergic tissue and thus can be used to identify the location of
tumor A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...
s such as
pheochromocytoma Pheochromocytoma (PHEO or PCC) is a rare tumor of the adrenal medulla composed of chromaffin cells, also known as pheochromocytes. When a tumor composed of the same cells as a pheochromocytoma develops outside the adrenal gland, it is referred ...
s and
neuroblastoma Neuroblastoma (NB) is a type of cancer that forms in certain types of nerve tissue. It most frequently starts from one of the adrenal glands but can also develop in the neck, chest, abdomen, or spine. Symptoms may include bone pain, a lump i ...
s.


Function tests

Certain tests, such as the Schilling test and urea breath test, use radioisotopes but are not used to produce a specific image.


History

Scintigraphic scanning was invented and proven by Neurologist and Radiologist professor dr. Bernard George Ziedses des Plantes. He presented the results in 1950 under the name 'indirect Autoradiograph’. In 1970, the Physikalisch-Medizinische Gesellschaft für Neuroradiologie (The Physics and Medical Society) instituted the ‘Ziedses des Plantes Medal'. It was first awarded to W. Oldendorf en G. Hounsfield in 1974 for Computer Tomography (CT). Later, in 1985, the medal was awarded to Ziedses des Plantes himself. In 1977 he received The Roentgen Medal.


See also

*
Gamma camera A gamma camera (γ-camera), also called a scintillation camera or Anger camera, is a device used to image gamma radiation emitting radioisotopes, a technique known as scintigraphy. The applications of scintigraphy include early drug development ...
* Medical imaging *
Nuclear medicine Nuclear medicine or nucleology is a medical specialty involving the application of radioactive substances in the diagnosis and treatment of disease. Nuclear imaging, in a sense, is "radiology done inside out" because it records radiation emit ...


References


External links

{{Medical imaging Scintigraphy