Single-photon emission computed tomography is often known by the abbreviation SPECT, which is the abbreviation for the single name of this study (Single Photon Emission Computed Tomography).
It should not be confused with computed tomography (CT) because of its similar name: while CT uses X-rays and a classical contrast agent, single-photon emission computed tomography is based on the delivery of a tracer (most commonly used here is Technetium-99m) is tracked by the body due to its - in the dose used harmless - radiation with gamma cameras, so without any exposure to X-rays.
In principle, the examination proceeds in the same way as the frequently performed scintigraphy, for example the thyroid gland or the lung. A distinction is made between two variants of this nuclear medicine diagnostic method: The static method only measures once where the radionuclide is located in the body at the time of examination; in the dynamic examination, repeated changes also make changes in the course of time visible.
The task of single-photon emission computed tomography is to check the functionality of specific organ systems and to detect possible disturbances. This is possible with the so-called tracer, a weak radioactive substance. The substance is usually injected at the beginning of the examination in the arm vein of the patient, for special organ examinations, however, it can also be swallowed or inhaled.
The slightly radiating radionuclide spreads in the organ to be examined and emits the weak gamma radiation there for a certain period of time. This is detected by special cameras, the so-called gamma cameras. The heads of the cameras rotate around the body of the patient during the examination and detect the radiation from different directions. Before a different waiting time is maintained depending on the examination, so that the tracer can accumulate optimally in the body. This enrichment is detected by the gamma cameras and rendered in computerized calculations in sectional images.
These are at least two-dimensional, sometimes even three-dimensional and therefore form a meaningful basis for the diagnosis of nuclear medicine. In the case of questions in which the metabolism in the organ, ie the course of the distribution of the radiopharmaceutical, is important, the recording will be repeated after a certain period of time, which may be minutes or even hours. A common type of examination in the field of single-photon emission computer tomography is the SPECT of the heart: it gives the cardiologist important information on the perfusion of the heart muscle tissue and can also be used in conjunction with the ECG (gated SPECT).
Evidence of constricted coronary arteries or heart failure is often detected early, so that appropriate prophylaxis, for example to prevent a heart attack, can be initiated. Another important function of single-photon emission computed tomography is the examination of brain function: from circulatory disturbances, which can cause a stroke, to degenerative processes such as Parkinson's disease, the diagnostic range is extensive. Also in the investigation of epilepsy patients or in certain tumor diseases, the nuclear medicine examination is used.
The sectional images also provide meaningful information about the metabolism in the bones, so that the diagnostics also find application in this area and, for example, provide the image basis for adequate therapy for inflammations or loose prostheses. Also in the NET, the neuroendocrine tumor, which is usually found in the digestive system, the SPECT is used for discovery. A special combination is the so-called SPECT / CT, which is realized with the help of special devices. It combines the ability of single-photon emission computed tomography to show functional processes in the body, with the advantage of CT in presenting morphological structures.
The single-photon emission computer tomography is usually performed in the supine position. Mostly she does not need special preparation. Only when examining specific organ systems may it be necessary to do this examination when the patient is fasting.
Single-photon emission computed tomography, like conventional scintigraphy, is a very low-risk method of examination. This is partly due to the fact that the patient is not exposed to X-rays during this examination (with the exception of the SPECT / CT special examination).
In addition, instead of a classical contrast agent, which could lead to an allergic reaction in some patients, especially in iodine-containing substances, the radioactive tracer (in many cases technetium) is used, which usually does not lead to side effects. The half-life of the used radiopharmaceuticals is very low, so that there is no danger even for the persons who come in contact with the patient after the examination. Only close physical contact with pregnant women or small children is not recommended for the day of the examination - similar to, for example, the frequently performed thyroid scintigraphy.
Even for nursing mothers, the nuclear medicine doctor recommends certain precautions that are relevant only for a short time. Patients who drink a lot after the examination can additionally speed up the excretion of the already low level of radioactivity from their body. The SPECT device should not be compared to the narrow and, for many patients, burdensome tube of the MRI. Due to the open parts of the device, single-photon emission computed tomography is also feasible for patients with claustrophobia.