Nuclear Medicine is a branch of medicine which deals with the diagnostic and treatment of human diseases with the help of chemical molecules or biological materials labeled with radioactive elements.
Having been used for the benefit of the humankind since its definition by Antoine Henri Becquerel, a French chemist, in 1896, radioactivity is used in the diagnostic and treatment of diseases at an ever increasing rate. In addition to obtaining such information that cannot be received with any other methods, it offers patients the opportunity of a smooth and comfortable treatment in many diseases.
The fundamental philosophy of Nuclear Medicine studies is the administration of a radioactive molecule to a patient which can specifically localize into a system, organ or cell group in the body suffering from a disease. The decision to use this molecule for diagnostic or treatment depends on the type of radiation emitted by the involved radioactive element For instance, the radioactive elements emitting Gama and Positron radiations are generally used for diagnostic whereas the radioactive elements emitting Beta (negatron) and Alpha radiations are used for treatment.
The radioactive elements used in Nuclear Medicine are manufactured in special facilities, handled in accordance with specific rules and prepared according to special formulas before they are administered to patients In this whole process, radioactive elements, any molecules combined with them and radiopharmaceuticals, which are the compound of a radioactive element and molecule, are prepared according to Good Manufacturing Practices (GMP).
Radionuclide Treatment: This method is based on the irradiation of tissues and cells at a limited distance by ionized radiation. It is employed in the treatment of hyperthyroidism, thyroid cancer, rheumatoid arthritis, treatment resistant lymphoma, bone metastases, some neuro-endocrine tumors and castration resistant prostate cancers etc. with successful results.
Theranostic: It is the name given to the individualized medical method which involves administration of a single molecule labeled with two different radionuclides suitable for diagnostic and therapy. Focusing on on personalized Diagnostic Diagnostic and treatment, theranostic ensures transition from conventional medicine to modern individualized/personalized medicine approach. Theranostic paradigm is used with the aim of creating a single agent which allow diagnostic, treatment and monitoring the response to the treatment. Many diagnostic and treatment procedures conducted in nuclear medicine fall into the scope of theranostics. The development of molecular diagnostic tests and target-specific therapeutic agents in a dependent and collaborative manner and, in particular, focusing on the customization of treatment by targeting a specific sub-type of disease and genetic profile of the individual during the treatment facilitate drug development process and enable optimizing drug efficacy and safety. Diagnostic application is a means of helping to identify the sub-type of disease, its progression and characteristics of a patient. In addition to the assessment of patient response to a treatment, this information enables making decisions about the selection of timing, dosage, drug type and treatment procedure.
Diagnostic Applications: Diagnostic applications are generally performed by acquiring images in nuclear medicine. Images are acquired with the use of such devices that determine the progress of a radioactive molecule administered to the body through the body as well as the radiation emitted by the radioactive element outside the body. Furthermore, external measurements can also be made without imaging. The radioactive elements used for diagnostic are not harmful to human health. The radioactive dose applied is very low and the activities of these elements with a certain half-life decrease in a short period of time. Treatment administration, on the other hand, is carried out only by Nuclear Medicine Specialists under control for patients who need treatment.
Diagnostic Applications without Imaging: These applicationsare carried out by using radioactive substances directed to a specific target in the body and external reading of radioactivity emitted by them using a suitable device. For instance, the radioactive iodine administered to the body accumulates in the thyroid gland. It is possible to obtain numerical data about iodine metabolism of the gland by measurements made from the thyroid region at certain intervals. On the other hand, many tissues in the body which are very difficult to detect visually (breast cancer, parathyroid, colon cancer etc.) can be identified through radioactive materials and suitable devices which can detect radioactivity during surgical operations. Such practices guiding the surgeon have become fairly common in the recent years.
Diagnostic Applications With Imaging: These applications involve external imaging by camera systems with the use of radioactive substances directed to a specific target in the body.
Various devices are used in diagnostic applications based on imaging and both radioactive radiation tomography and computed tomography resulting from X-rays can be simultaneously obtained thanks to the current advanced technology. The images are divided into three groups depending on the radioactive substance used and specifications of the imaging device:
1) Planar Imaging: Commonly applied studies such as thyroid scintigraphy, renal scintigraphy, whole body bone scintigraphy etc. are the examples of this type of imaging. Planar imaging involves 2D imaging with the use of radioactive substances emitting gamma radiation and the devices called as gamma cameras and the majority of routine studies are in this nature.
2) SPECT (Single Photon Emission Computed Tomography): SPECT refers to the imaging of the radioactive substance distribution in the body in a three-dimensional manner, in other words, through tomography. Myocardial perfusion scintigraphy (cardiac scintigraphy) which is very commonly used today and brain perfusion scintigraphy are these types of studies. It is also possible to perform bone, renal, and lung scintigraphy through tomography planar imaging where the substances emitting gamma radiation and tomographic gamma cameras are used if desired.
3) PET (Positron Emission Tomography): PET is the name given to tomographic imaging method employed with radioactive molecules emitting a positron and special imaging devices. Currently, the most frequent application is the imaging of distribution after the administration of radioactive glucose (FDG) to the body. It is known that this is still the most sensitive method for the imaging of cancer tissues. “Hybrid systems” which can create tomographic images by detecting the gamma rays and positrons emitted from the patient and also from magnetic resonance and X-rays directed externally ( PET-CT, PET-MR, SPECT-CT etc..) are developed thanks to the current advanced technology.