There are many different types of medical imaging technologies, but the three major types are Radiologic Technology (which includes x-ray and computed tomography (CT scans)), magnetic resonance imaging (MRI), and nuclear medicine. Each type uses a different way of imaging the body. Radiologic technology uses x-rays to image the body, nuclear medicine uses radiopharmaceuticals and MRI uses strong magnetic fields and radiofrequency pulses.
The type of imaging ordered by your physician depends upon many factors. Most important, of course, is how well the technology will visualize the part of your body being studied. For instance, MRI can easily show the difference between the white matter and gray matter in your brain and spinal cord, whereas a CT scan is not as good at showing that detail. . Therefore, if the physician wants to see the gray and white matter, they order an MRI.
An x-ray image is produced when a small amount of radiation passes through a body part and is captured to produce a black-and-white image.
Body parts that are difficult for x-rays to pass through, such as bone, appear white on the x-ray image. Body parts that the x-rays pass through easily, such as the lungs or other areas filled with air, appear black. Soft tissue (like muscle), blood vessels and organs usually appear as various shades of gray on an x-ray image, depending upon what they are made of.
Once the x-ray radiation passes through the body, it is captured by an imaging plate, connected to a computer, which creates a visible image.
The x-rays delivered to a patient during a typical diagnostic imaging exam are the safest they have ever been. MRTs working in Radiologic Technology use the lowest possible dose of radiation to achieve a quality image. In addition, new techniques and equipment are constantly being developed to decrease the total amount of radiation received by the patient.
It is important to know that there are different types of radiation are all around us. Radiation comes from the atmosphere, the Earth’s crust and cosmic rays. There are even small amounts of radiation that comes from bananas! X-rays are a little stronger than these other examples and are used in medical settings. For comparison, just living life on this earth for a year, exposes you to an average of 3.3 millisieverts (mSv) of background radiation from the environment. A typical dental x-ray you may get is approximately 0.06 mSv. A chest x-ray is approximately 0.08 mSv and a mammogram is almost 1.0 mSv. A CT scan can be anywhere from 1-10 mSv depending on the part of the body being imaged.
Any exposure to radiation can pose a safety risk. However, whenever a test or procedure using x-rays is ordered, your physician has considered the benefits of an x-ray examination. They decided that the amount of information they will get from the test it outweighs the risk. This information can help doctors visualize what is happening and can help create a treatment plan.
Computed tomography (CT) also uses x-rays, but images the anatomy in a different way. Here, the source of the x-rays rotates around the patient during a CT scan, capturing detail from many angles. This is known as cross-sectional imaging. Each rotation of the x-ray beam produces a single “slice” of anatomy, like the slices in a loaf of bread. A computer can stack all the slices to create a whole 3-dimensional image of the body. Using this technology, physicians can view the inside the body’s structures, a feature not possible with general X-rays.
Contrary to popular belief, there is no X-rays used in an MRI. In the MRI scanner, hydrogen atoms in the patient’s body are exposed to a strong magnetic field. A radiofrequency pulse is then used.When the pulse is turned off, the atoms give off energy signals that are measured by the MRI machine. The computer processes these signals to create detailed images of human anatomy.
MRI technology is known for producing extremely detailed images. An MRI is better at capturing the small features between similar structures. For instance, it can easily show the difference between the white matter and gray matter in your brain and spinal cord, whereas a CT scan is not as detailed. Because of this, an MRI will be chosen when looking for small structures or when images of finer detail are needed.
Since MRI is non-invasive, the exam is painless. Depending on what specific issue they are looking for, your MRI may use a contrast agent to better see a part of your anatomy. If this is the case, the MRT will give you an injection prior to or during the exam. The MRT will ask you to lay down on the table. The table will move you slowly in and out of the MRI scanner. Sometimes, but not often, people feel a little dizzy when the MRI table moves into and out of position. Once you are in the correct spot, you will hear a loud knocking or buzzing sound throughout your exam. Your MRT will provide you with hearing protection. The exam room may be cold, to keep the machine at a correct temperature. Your MRT can provide you a blanket if you get cold. Exam times vary, however, your MRT is in the control room and is watching you through a glass window the whole time. You can also talk to them through an intercom if you need to.
A typical exam lasts less than 60 minutes but can be as short as 15 minutes or as long as 2 hours. You should always allow extra time in case the exam lasts longer than expected. For first timers undergoing an MRI, the shape and loud noises of the MRI machine can be intimidating. Depending on the scan required, your whole body may go into the MRI scanner. The body part being imaged needs to be in the center of the machine to produce the best image. If you feel nervous, let the MRT know, and they will try to work with you. There are many tools and resources that an MRT can do to help you get through the exam.
During the scan, you will be always in contact with an MRT. Even when they are not in the MRI room, you will be able to talk to them by intercom. You can ask the MRT to talk to you between scans to let you know how long the next one will be. A cooling fan can be turned on or up to give you the feeling of more air. The MRT is always able to see you through a large patient viewing window, but not be able to hear you during the loud sounds. A rubber squeeze ball will be given to you, to hold in your hand, in case you have trouble during a scan. This will get their attention. In some cases, a friend or family member may stay in the scan room with you during your exam. Please consult your MRI facility for their policy on this matter.
When you arrive for your MRI exam, you will be required to provide a health and surgical history. Anyone with surgical implants, including metallic or electronic implants should notify the MRT. They will consult with the radiologist or sometimes, your family doctor, to determine if you can be safely scanned. Many modern surgical implants can be scanned in the machine but may require planning ahead of time. Therefore, it is important to share your health and surgical history with your MRT. To help with future scans, be sure to ask your surgeon (or a family member’s surgeon) what exactly was implanted during the surgery/procedure or if you have an implant card. This information can save time when an urgent MRI is needed.
Nuclear Medicine uses small amounts of radioactive materials, or radiopharmaceuticals, to create images based on how your body is working. An MRT will introduce them into your body by injection, swallowing or inhalation. The radiopharmaceuticals travel through the body and accumulates in the area of interest. Different types of radiopharmaceuticals will accumulate in different areas. The correct one is chosen based on what your physician wants to see. After the correct amount of time has passed, the MRT will use a specialized camera (gamma camera or PET scanner) to detect the radiation coming from your body. The gamma camera software then transforms that into images, which are sent to a computer for the radiologists and other care providers in your care team to look at.
Common Nuclear Medicine procedures include investigation of the thyroid, brain, bones, lungs, and heart.
Radiation therapy uses high-energy radiation to kill cancer cells and shrink benign tumors or growths. This Higher energy radiation results in a higher dose compared to an x-ray or a CT scan. Therefore, MRTs ensure that the radiation be precisely targeted and the dose to the patient is carefully monitored. Radiation therapy is used as a method to treat cancer, but also used in palliative care to reduce pain or other troublesome symptoms. It can also be used to treat benign tumors and other noncancerous growths.
Radiation therapy works by applying a high energy radiation beam to the cancer cells over a period of time. This radiation damages the DNA of the cancer cells and causes them to die. When the damaged cells die, they are broken down and eliminated by the body’s natural processes
There are a few ways to deliver radiation therapy. Radiation Therapists most often use a machine in radiation treatment called a linear accelerator, or LINAC. These machines use external focused beams of high energy radiation that targets and kills the cancer cells while minimizing damage to healthy tissues. Alternatively, treatment may involve placing radioactive sources directly into the patient’s body, near or in the cancerous tumor. This is called brachytherapy.
Radiation therapy is given as a treatment to damage the DNA of cancer cells so that they are eliminated or decreased in size. Radiation therapy may be used alone or in combination with surgery, chemotherapy, or both.
Radiation therapy is also sometimes given as a palliative treatment. Palliative treatments are not intended to cure. Instead, they relieve symptoms and reduce the suffering caused by cancer.
An oncologist will prescribe Radiation Therapy as part of a treatment plan, depending on the type of cancer a patient has, the cancer’s location or the stage of the cancer.
While bones are seen well on x-rays and other medical images, soft tissues of the body can be difficult to see. Contrast agents highlight specific organs or blood vessels, making them more visible on a diagnostic image. Like their name suggests, they provide contrast between various types of tissue. Some contrast agents are designed for the patient to drink, while others are injected, delivered through an intravenous line, or administered into a body cavity. The most common types of contrast used in general radiography have traditionally been air, iodine and barium. Non-iodinated contrast media is increasingly more commonly used.
Special types of contrast agents also are used in magnetic resonance imaging. Gadolinium is a contrast dye used during some MRI exams. The clear solution is injected into your hand or arm with an intravenous (IV) line. It interacts with the MRI’s magnetic field, creating differences between organs and vessels.
If you develop sensitivities or react to a contrast, it will likely happen immediately. MRTs are trained to start IVs, inject the contrast, and manage any reactions that you may have. If you have had previous sensitivities or reactions to contrast, you should inform the MRT who will consult with the radiologist.