Nuclear Medicine is a branch of medical science where radionuclides are used for diagnosis and treatment of various medical conditions. The emphasis is on function and chemistry rather than structure. Organ/tissue specific compounds which trace a particular physiological process are tagged with radionuclides and administered to the patient. These are called radiopharmaceuticals or radiotracers, which are usually injected into the bloodstream/locally or given orally, allowing you to see where they are localized in your body, and provide information about the function of various cells, tissues and organs.
These studies are possible by assessing the distribution of these radiotracers with the help of Single photon emission tomography (SPECT) and Positron emission tomography (PET) machines. Both types are usually used in conjunction with a computed tomography (CT) scan to help localize the site of radiotracer accumulation. PET-CT and SPECT-CT acquisitions can include the whole body, a limited portion of the body, or an organ.
Radionuclides are also used for therapy of malignant and non-malignant conditions. With the use of suitable radiopharmaceuticals ‘targeted therapy’ is also possible.
I. Positron emission tomography (PET-CT scan):
PET allows ‘noninvasive quantitative’ assessment of biochemical and functional processes.
Indications in Oncology:
II. Single Photon emission Computed Tomography (SPECT-CT scan):
It allows the clinician to assess the perfusion and functionality of specific tissues.
Indications for SPECT/CT include but are not limited to imaging of the following:
|Name of test||Radioactive tracer||Purpose of test|
|Bone scan||Tc-99m MDP||enables identification of spread of tumour to bone, active inflammation etc.,|
|Thyroid scan||Iodine-123, Tc-99m Pertechnetate||Imaging for thyroid cancer and thyroid function.|
|Renal scan||Tc-99m MAG3 or LLEC, DTPA, DMSA||To assess Parenchymal function and drainage, GFR measurement, to identify renal scars.|
|MIBI scan||Tc-99m sestamibi||Most commonly used to detect coronary artery disease; also used to locate parathyroid adenomas|
|Cardiac gated blood pool scan||Tc-99m labelled red blood cells||Monitor heart function in patients having chemotherapy.|
|Sentinel node scintigraphy||Tc-99m Sulfur/antimony colloid||Identify the pathway of lymphatic spread, most commonly performed in breast cancer and melanoma|
|Lung scan||Tc-99m Technegas/MAA||Used to detect clots in the lung (pulmonary emboli) and to measure lung function|
III. Nuclear Medicine therapies:
Targeted radionuclide therapy or Molecular radiation therapy:
A type of radiation therapy in which a radionuclide (a radioactive chemical) is linked to a cell-targeting molecule, such as a monoclonal antibody, and injected into the body. The cell-targeting molecule binds to a specific target found on the cells. This may help ‘kill the targeted cells’ while ‘limiting the harm to normal cells’.
Radiation risk to patients with Nuclear Medicine procedures:
All nuclear medicine procedures involve administering radioactive compounds, but the radiation dose patients receive is quite low. Radiation dose with most scans being below the natural background radiation they receive from the environment over the course of a year. Higher radiation dose is obtained from PET scans and Radionuclide therapies performed on cancer patients. But the benefit is greater compared to the risk.
With the advent of new Radiopharmaceuticals, PET/SPECT scans or Therapies, there is great scope for research in the field of Nuclear Medicine.
Being functional and metabolic process imaging, Nuclear Medicine scans can help to predict early response to a particular treatment and determine whether that treatment is effective for that person. Thus, ‘Personalized/Precision Medicine’ can be achieved with Nuclear Medicine.
Assessment of various physiological processes also allows for a better understanding of the disease. Thus, early diagnosis and/or better management is possible.
Facilities available in the Institute:
PET-CT is installed in the Institute.
Various Radionuclide therapies can be performed in Two bedded high dose therapy ward in due course.
SPECT-CT and Medical Cyclotron are in the process of procurement.
The Department is also involved in the interdisciplinary management of various Thyroid disease patients.