Every day applications of radiation medicine help millions of patients worldwide. Some techniques enable physicians to see inside the human body creating digital images using short-lived radioisotopes. These are called diagnostic techniques. Others which enable targeted and precise radiation treatment of cancer are therapeutic techniques.
In general, radiation and radioisotopes find applications in the following categories of health care:
External Radiation Therapy
It is used for controlling or eliminating cancerous growths formed by rapidly dividing cells. For radiotherapy to effect a cure, it is essential that the correct amount of radiation (absorbed dose) be delivered to the patient. Too small a dose, and one or more cancerous cells may survive, leading to recurrence of the disease. Too large a dose, and the healthy tissue surrounding the tumour may be destroyed. The radiation source is placed in a shielded housing and a well-defined beam of radiation emanating from the source is directed towards the tumour for treatment. Intense Cobalt-60 sources ranging from 9000 to 12000 curies encapsulated and supplied by Board of Radiation and Isotope Techology (BRIT) are being used in most of the 225 Teletherapy units set up in 62 cities in India for cancer treatment. Now-a-days, electron accelerators are being widely used for radiotherapy. The advantage of electron beam therapy lies in the precision with which it can irradiate and destroy tumours. Raja Ramanna Centre for Advanced Technology (RRCAT), Indore, has developed electron accelerator based teletherapy machine. In this machine, a microtron (a type of electron accelerator) accelerates electrons to an energy, which depending on the depth of the tumour varies from 6MeV to 12 MeV. For very deep tumours, the electron beam can be converted to X-rays, which then are equivalent to gamma rays from Cobalt-60 source.
Brachytherapy
It is an advanced cancer treatment wherein radioactive seeds or sources are placed in or near the tumor itself, giving a high radiation dose to the tumor while reducing the radiation exposure in the surrounding healthy tissues. In this procedure, thin catheters are first placed in the tumor and then connected to a High-Dose Rate (HDR) afterloader. This contains a single highly radioactive iridium pellet at the end of a wire. The pellet is pushed into each of the catheters one by one under computer control. The computer controls how long the pellet stays in each catheter (dwell time), and where along the catheter it should pause to release its radiation (dwell positions). With a few well-placed catheters in the tumor, HDR brachytherapy can provide a very precise treatment that takes only a few minutes. After a series of treatments, the catheters are removed, and there are no radioactive seeds left in the body. Cancers of prostate, breast, lung, uterus, cervix, head and neck are treated using brachytherapy techniques. Board of Radiation and Isotope Techology (BRIT) supplies Brachytherapy sources like Iridium-192 and Cesium-137 for cancer treatment.
Nuclear medicine
Nuclear medicine techniques make use of radiation emitted by radioisotopes. Detecting these emissions and transforming them into images is the basis of nuclear medicine techniques. Scientists have identified a number of chemicals that are absorbed by specific organs. With this knowledge, several radiopharmaceuticals have been developed. These are compounds that are tagged with radioisotopes for diagnostic or therapeutic purposes which are injected into the patient's body. Once a radiopharmaceutical enters the body, it is incorporated into natural biological processes and excreted normally. There are up to 200 radioisotopes routinely used as tracers in biological substances. The non-invasive nature of this technology, together with the ability to observe an organ functioning from outside the body, makes this technique a powerful diagnostic tool.
Radiopharmaceuticals injected into a patient produce a signal which can be seen using a gamma camera - a device that detects gamma radiation. Single-Photon Emission Computed Tomography (SPECT) uses a rotating gamma camera to obtain images from multiple angles of the organ being studied. For example, images of the heart taken with a SPECT gamma camera record how much blood is flowing into all parts of the heart muscle. These images help doctors to determine the severity of the heart disease. For low-risk patients, SPECT can avoid unnecessary referrals for very expensive procedures, such as cardiac catheterization or coronary angiography, by filtering out patients who don't need these procedures.
Similarly, Positron Emission Tomography (PET) is a precise and sophisticated imaging technique using radioisotopes. PET makes it possible to show both organ function and the development of the disease within it. Simple sugars, glucose, for example, can be labelled with signal emitting radioisotopes and injected into the patient. The PET scanner records the signals that these radioisotopes emit as they collect in organs targeted for examination. A computer then translates the signals into images.
It is used for controlling or eliminating cancerous growths formed by rapidly dividing cells. For radiotherapy to effect a cure, it is essential that the correct amount of radiation (absorbed dose) be delivered to the patient. Too small a dose, and one or more cancerous cells may survive, leading to recurrence of the disease. Too large a dose, and the healthy tissue surrounding the tumour may be destroyed. The radiation source is placed in a shielded housing and a well-defined beam of radiation emanating from the source is directed towards the tumour for treatment. Intense Cobalt-60 sources ranging from 9000 to 12000 curies encapsulated and supplied by Board of Radiation and Isotope Techology (BRIT) are being used in most of the 225 teletherapy units set up in 62 cities in India for cancer treatment. Now-a-days, electron accelerators are being widely used for radiotherapy. The advantage of electron beam therapy lies in the precision with which it can irradiate and destroy tumours. Raja Ramanna Centre for Advanced Technology (RRCAT), Indore, has developed electron accelerator based teletherapy machine. In this machine, a microtron (a type of electron accelerator) accelerates electrons to an energy, which depending on the depth of the tumour varies from 6MeV to 12 MeV. For very deep tumours, the electron beam can be converted to X-rays, which then are equivalent to gamma rays from Cobalt-60 source.
A new nuclear medicine procedure, called sentinel lymph node detection, allows for detection of lymph nodes that are free of breast cancer thus identifying patients who don't need aggressive surgery. It involves injecting a radiopharmaceutical near the breast tumour site. After the injection, the tracer is drained through the lymphatic vessels. The sentinel node is the first node in a chain of nodes through which breast cancer spreads. In the operating theatre, a hand-held gamma probe is used to locate the area of radioactivity and detect node location. Doctors find and remove the sentinel node, and then analyse it to detect even the smallest deposit of metastatic cancer cells.
Sometimes certain types of cancers may progress to a painful disorder of the bone, known as metastatic bone disease. Fortunately, advances have been made using radiopharmaceuticals to ease the associated severe pain. Radiopharmaceuticals, injected into the body, seek out cancer affected areas in the bone and accumulate in these affected areas. They work to kill cancer cells, thereby lessening existing bone-related pain and possibly even delaying the development of new areas of pain. In some cases, a single injection can relieve pain for an average of three to six months - without the disorientation, drowsiness and uncomfortable side effects of other types of pain treatment.
Technetium-99m (Tc-99m) is the main workhorse of diagnostic nuclear medicine practice. Iodine-131, as sodium iodide, is used for diagnosis and treatment of thyroid disorders. Sodium phosphate (Phosphorus-32 based) injection is used for or pain palliation in severe bone cancer cases. Another important radiopharmaceutical, Samarium-153- is effective in pain relief of terminally sick cancer patients. Board of Radiation and Isotope Techology (BRIT) supplies these radiopharmaceuticals and allied products to nearly 120 nuclear medicine centres in the country.
Other applications of radioisotopes in health care are continuously being developed. For example, coronary stents coated with Phosphorus-32 supplied to hospitals for clinical trials on cardiovascular radiation therapy have yielded good results. Methods have been developed to prepare Iodine - 125 source for treatment of occular tumors and prostate cancer. Holium-166 and Samarium-153 labelled hydroxyapatite particles have been developed for treating arthritis of large and medium-size joints respectively and tried on a number of patients.
The Radiation Medicine Centre (RMC) of Bhabha Atomic Research Centre (BARC) in Mumbai, has become the nucleus for the growth of nuclear medicine in the country and carries out a large number of patient investigations every year. Similarly Tata Memorial Centre (TMC), a fully autonomous aided institution of DAE, provides comprehensive treatment for cancer and allied diseases and is one of the best radiation oncology centres in the country. Every year nearly 40,000 new patients visit the clinics from all over India and neighbouring countries. Nearly 60% of these cancer patients receive primary care at the Hospital of which over 70% are treated almost free of any charges. Over 1000 patients attend the OPD daily for medical advice, comprehensive care or for follow-up treatment. Nearly 6300 major operations are performed annually and 6000 patients treated with Radiotherapy and Chemotherapy annually in multi-disciplinary programmes delivering established treatments.
These centres may be contacted at the following address:
Radiation Medicine Centre (RMC),Radiation Sterilisation of health care products
Radiation Sterilisation is another important application of radioisotopes towards health care offered on a commercial basis to the Indian medical industry. The ability of gamma radiation to kill micro-organisms is effectively made use of in radiation sterilisation of various medical products such as disposable syringes, surgical sutures, cotton dressing, drugs and related products etc. The advantage over conventional techniques is that the sterilisation is effected in the final packing so that the product remains sterile up to the point of use. Moreover, as it is a cold process, heat sensitive materials like plastics used in medical products are not adversely affected. The Irradiation Sterilisation of Medical Products (ISOMED) Plant at Trombay was the first unit to be started by the Department of Atomic Energy for this purpose. Over a million radiation sterilised midwifery kits and delivery packs, to be used in rural areas for preventing infection of mothers and helping to minimize infant mortality rate, have been distributed through rural health programmes funded by WHO and this has decreased infant mortality rate in the areas where these kits were supplied.
Further information on radiation Sterilization and related aspects is available at Board of Radiation and Isotope Techology (BRIT).