Conventional scintigraphy
It is a method of detecting the distribution of radionuclides in the organ or tissue to be examined in the form of images.
The distribution of the radionuclide in the organism is determined by detectors in which the radiation is converted into light in flashes (scintillation).
Radionuclide is the name given to radioactive atoms. Radionuclides with gamma (g) rays are used in scintigraphy. The most commonly used radionuclide is Technetium 99m (Tc99m).
Technetium, which has a half-life of 6 hours, is easily obtained and has the appropriate energy for scintillation.
Indium-113m, Thallium-201, Iodine-123 and Gallium-67 are other radionuclide examples frequently used in scintigraphy.
Myocardial perfusion studies performed with Thallium-201 and Technetium 99m in scintigraphy, which is frequently used in cardiology, are diagnostic methods with a very high accuracy rate in the diagnosis of coronary ischemia and infarction.
Skeletal scintigraphy; It is used in the investigation of active bone lesions such as metastases.
It is the best diagnostic method after CT angiography in the detection of pulmonary embolism and infarction. For this, ventilation-perfusion scintigraphy is performed.
The absence of blood flow in testicular torsion can be demonstrated by scintigraphy.
Iodine-131 scintigraphy is used in the follow-up after surgery or ablation of thyroid cancer.
Single Photon Emission Computed Tomography (SPECT)
• It is a nuclear medicine tomographic imaging technique similar to computerized tomography devices but performed with gamma rays.
• SPECT converts 2D images scanned from different angles by a gamma camera into 3D tomographic images with the help of software.
• SPECT method often; It is used in myocardial perfusion scintigraphy and brain perfusion scintigraphy. However, with this method, it is possible to apply tomographic scans of organs such as bone, kidney, lung and liver. Better imaging can be achieved when SPECT images are combined with CT images.
Positron Emission Tomography (PET)
• Measurement of cerebral blood flow and oxygen metabolism, glucose and fatty acid metabolism, amino acid transport, evaluation of neurotransmitter synthesis and measurement of neuroreceptor density can be performed using radionuclide agents.
• The most commonly used radionuclide agent is 18-fluorodeoxy glucose (FDG).
• There are specific agents used for some cancers. PET examination can be performed with Ga-68 PSMA for prostate cancer and with Ga-68 DOTATATE for neuroendocrine tumors.
• Important usage areas of PET imaging:
• In detecting the presence and prevalence of brain tumors
• In the differentiation of recurrent tumor - radiation necrosis
• In detecting focal epilepsy focus
• In the differential diagnosis of dementia causes such as Alzheimer's disease, Parkinson's and Huntington's
• PET-CT is a hybrid imaging method and can be used in metastatic tumors of unknown primary, tumor staging and evaluation of response to treatment, as it shows the anatomical region where metabolic activity is increased.
