Nuclear Medicine

Kynzie and Savannah

What is Nuclear Medicine?

This is a branch of medicine that uses radiation to assist physicians to make quick and helpful decisions on behalf of their patients. Radiation can be used to treat organs or even tumors that are harmful to people. Nuclear medicine uses radioactive tracers. These radioactive tracers, when placed in the body, emit gamma rays. A huge portion of hospitals all over the world use nuclear medicine, and almost all of it is for a patient’s diagnosis. In the U.S. alone, there are over 20 million nuclear medicine procedures every year.

PET Machines

A PET machine, or positron emission tomography machine, uses nuclear medicine imaging to form a 3-dimensional picture of a target area in a body. Many modern PET machines also double as a CT x-ray scan, and can perform such scans simultaneously. PET machines are used to both diagnose a condition and monitor a preexisting condition.


A PET machine works by first injecting a radio tracer into the body. A radio tracer is a combination of a radioactive medicine and a natural chemical (glucose, water, or ammonia). Depending on the natural chemical used, the radio tracer will be attracted to certain areas of the body. For example, cancers use glucose in a unique way from how healthy tissues use that same glucose, so cancers can be targeted in PET machines.


The PET machine picks up and tracks the radio tracer while it is in the body by scanning for positions, which are emitted as the radio tracer is broken down. The machine can then convert what it picks up into an on-screen image. This image can show how certain parts of the body function, and if they are doing so correctly or not, by showing different colors according to different levels of positron emission. That image is then interpreted by a radiologist, and the patient can be diagnosed.

X-Rays

An x-ray is a test that doctors use to look at the bones or internal organs of a patient. X-rays are like electromagnetic waves, but they penetrate the different internal organs of the body at different levels. The image produced on the film shows you the distinct things inside the body due to the different levels of penetration.


By exposing the body to a very brief amount of electromagnetic radiation , the x-ray machine produces an image on film. When the electromagnetic radiation goes through the body, the different body tissues absorb different amounts of the radiation. On an x-ray, bones appear white in color because they absorb the most radiation. The lungs, however, absorb very little radiation and therefore appear black on the image.


An x-ray can be completed from front to back, or they can be contained to specific areas of the body. The radiation exposure that one would experience from one chest x-ray is almost equal to the amount of radiation that you are exposed to naturally for 10 days. And although x-rays expose the patient to radiation, they are very safe when they are done with care.

Using Radiation to Fight Cancer

Radiation therapy kills/damages cancer cells by using high energy rays to target cancer cells and keep them from reproducing.


Such therapy is highly dependent on the details of the cancer: the location, type, and stage all must be taken into consideration when reporting success rates. Some cancers, like Hodgkin's, prostate, and bone, respond fairly well with approximately 75% of patients being cured. Localized cancers also tend to respond well to radiation. Others, like centrally-located cancers or ones that have spread through the body, are usually not treated, or not treated successfully, using radiation therapy.

Cobalt-60

Cobalt-60 is a metal that is hard with a gray/blue tint. Under normal conditions it is a solid and is magnetic. Cobalt-60 is the radionuclide of the non radioactive Cobalt. It is a by-product of nuclear reactors and is used in linear accelerators. The gamma radiation from Cobalt-60 is primarily used to reveal problems that are internal either in objects or people.


This radionuclide is primarily used for radiotherapy in hospitals. The process is very similar to an x-ray. It has uses in medical devices used to treat inoperable deformities or brain tumors or blood vessels. A patient is put under a small amount of anesthesia and is positioned on a table. The machine is placed facing the tumor, and then it emits around 200 beams of gamma radiation at the area where the tumor is located. It could take anywhere from 30 minutes to 3 hours depending on the size, location, and severity of the tumor.

Iridium-192

Iridium-192, a radioisotope of iridium metal, has many uses, one of them being medical. In the medical field, this radioisotope takes a part in brachytherapy (a process of treating cancer by inserting certain radioactive implants directly into the target area's tissue). Iridium-192 implants deliver small doses of radiation at a much closer distance than that which is achieved by radiation therapy. The most common places for iridium-192 implants are in the head and breast. These implants are typically in a wire form, and are placed in the target area via catheter. The necessary dosage of radiation is given to the area, and then the implant wire is removed.


Usually, iridium-192 implants are very successful with providing radiation to localized treatment areas, in terms of being effective treating the tumor site while also keeping the exposure to radiation the rest of the body must undergo at an extreme low.

Radioisotopes

Most radioisotopes used in nuclear medicine are man made, in a supply and demand kind of way. Neutron-rich radioisotopes result from nuclear fission and have to be made in a reactor. Neutron-poor radioisotopes are different, because they have to be made in another machine called a cyclotron.


Radioisotopes made in a reactor include Cobalt-60, Iridium-192, and Bismuth-213 (primarily used in the fight against cancer). Radioisotopes made in a cyclotron include Gallium-67, Fluorine-18, and Iodine-124 (primarily used as tracers & in tumor imaging). The two types of radioisotopes decay differently and as a result, they have different properties and completely different uses. Scientists can make these two different types of radioisotopes by adding extra protons, creating a neutron-poor radioisotope, or by adding extra neutrons, creating a neutron-rich radioisotope.