Medical imaging - Lecture notes 1 PDF

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Medical imaging (x-ray, CT scan, MRI and mammography)

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What is an MRI? An MRI (magnetic resonance imaging) scan is an imaging test that can give very detailed images of the inside of the body. Instead of using X-rays, MRI uses strong magnets, low-energy radio waves and a computer to produce images.

When is an MRI done? MRI scans can provide detailed pictures of any part of the body. MRI is used when it is considered to be the best test to help diagnose or assess your condition, or when simpler and less expensive tests have failed to give a diagnosis. MRI is often recommended for imaging the brain and spine because of the detailed, high-quality images it provides. It is also useful in assessing knee injuries and other sports injuries as it is good at showing problems with soft tissues such as muscles, tendons and ligaments. MRI is often used in addition to other tests, including other imaging tests such as ultrasound. MRI can sometimes show conditions or details that other imaging tests cannot provide.

How does an MRI work? The strong magnets in the MRI scanner create a magnetic field, which causes the hydrogen atoms in your body to line up in the same direction. Radio waves are then passed into the part of your body being scanned, moving the hydrogen atoms out of alignment. When the radio waves are turned off, the atoms realign, and as they do so they produce radio signals. The signals are transmitted to radio antennae, or receivers, and the computer picks up this information and generates images. Hydrogen atoms are found in water – H2O – and our bodies have a high composition of water, meaning hydrogen is found throughout the body. Because the hydrogen atoms in different types of body tissue realign at different speeds, they produce different signals. Diseased tissue also gives off a different signal from healthy tissue. This allows the scanner to tell the difference between different tissue types and detect damaged or diseased tissue

Common uses of MRI      

brain lesions multiple sclerosis Diagnostic assessment General health Increase effect of another treatment nerve pain (neuralgia)

Side effects and risks of an MRI

Risks Sometimes people who have had an injection of contrast dye may have an allergic reaction to the dye. In most cases allergic reactions are mild, and in the case of a more severe allergic reaction, you can be given medication to treat it. People with kidney problems may be at risk of complications related to the gadolinium contrast medium (dye) that may be used during an MRI. Your doctor may recommend having a blood test before the MRI to assess your kidney function. If you have any metal objects in your body, this can be a safety hazard during MRI scanning due to the metal heating up, moving, or electronic or mechanical devices malfunctioning. It’s important that your doctor and radiographer are aware of any metal implants or devices that you have, to determine whether it is safe for you to have an MRI.

Side effects     

headaches anxious mood fear of confined spaces (claustrophobia) pain muscle soreness

 nausea

what is an X-ray? an X-ray is a common imaging test that’s been used for decades. It can help your doctor view the inside of your body without having to make an incision. This can help them diagnose, monitor, and treat many medical conditions. Different types of X-rays are used for different purposes. For example, your doctor may order a mammogram to examine your breasts. Or they may order an X-ray with a barium enema to get a closer look at your gastrointestinal tract. There are some risks involved in getting an X-ray. But for most people, the potential benefits outweigh the risks. Talk to your doctor to learn more about what is right for you.

X-ray sources abound around us. They include the following:  o o o  o

o o o o o

Natural X-ray sources Astrophysical X-ray source, as viewed in X-ray astronomy X-ray background Naturally occurring radionuclides Artificial X-ray sources Radiopharmaceuticals in radio pharmacology  Radioactive tracer  Brachytherapy X-ray tube, a vacuum tube that produces X-rays when current flows through it X-ray laser X-ray generator, any of various devices using X-ray tubes, lasers, or radioisotopes Synchrotron, which produces X-rays as synchrotron radiation Cyclotron, which produces X-rays as cyclotron radiation

Side effects and risks of x-ray Risks x-rays can cause mutations in our DNA and, therefore, might lead to cancer later in life. For this reason, X-rays are classified as a carcinogen Trusted Source by both the World Health Organization (WHO) and the United States government. However, the benefits of X-ray technology far outweigh the potential negative consequences of using them. It is estimated that 0.4 percent of cancers in the U.S. are caused by CT scans Some scientists expect this level to rise in parallel with the increased use of CT scans in medical procedures. At least 62 million CT scans were carried out in America in 2007. According to one study, by the age of 75 years, X-rays will increase the risk of cancer by 0.6 to 1.8 percent Trusted Source. In other words, the risks are minimal compared to the benefits of medical imaging.

Each procedure has a different associated risk that depends on the type of X-ray and the part of the body being imaged.

Side effects While X-rays are linked to a slightly increased risk of cancer, there is an extremely low risk of short-term side effects. Exposure to high radiation levels can have a range of effects, such as vomiting, bleeding, fainting, hair loss, and the loss of skin and hair. However, X-rays provide such a low dose of radiation that they are not believed to cause any immediate health problems.

ACT scan A CT scanner emits a series of narrow beams through the human body as it moves through an arc. This is different from an X-ray machine, which sends just one radiation beam. The CT scan produces a more detailed final picture than an X-ray image. The CT scanner's X-ray detector can see hundreds of different levels of density. It can see tissues within a solid organ. This data is transmitted to a computer, which builds up a 3-D cross-sectional picture of the part of the body and displays it on the screen. Sometimes, a contrast dye is used because it can help show certain structures more clearly. For instance, if a 3-D image of the abdomen is required, the patient may have to drink a barium meal. The barium appears white on the scan as it travels through the digestive system. If images lower down the body are required, such as the rectum, the patient may be given a barium enema. If blood vessel images are the target, a contrast agent will be injected into the veins. The accuracy and speed of CT scans may be improved with the application of spiral CT, a relatively new technology. The beam takes a spiral path during the scanning, so it gathers continuous data with no gaps between images. CT is a useful tool for assisting diagnosis in medicine, but it is a source of ionizing radiation, and it can potentially cause cancer.

Sh a r eo nP i nt e r es t

uses it is useful for obtaining images of:       

soft tissues the pelvis blood vessels lungs brain abdomen bones

CT is often the preferred way of diagnosing many cancers, such as liver, lung, and pancreatic cancers. The image allows a doctor to confirm the presence and location of a tumor, its size, and how much it has affected nearby tissue. A scan of the head can provide important information about the brain, for instance, if there is any bleeding, swelling of the arteries, or a tumor. A CT scan can reveal a tumor in the abdomen, and any swelling or inflammation in nearby internal organs. It can show any lacerations of the spleen, kidneys, or liver. As a CT scan detects abnormal tissue, it is useful for planning areas for radiotherapy and biopsies, and it can provide valuable data on blood flow and other vascular conditions. It can help a doctor assess bone diseases, bone density, and the state of the patient's spine. It can also provide vital data about injuries to a patient's hands, feet, and other skeletal structures. Even small bones are clearly visible, as well as their surrounding tissue.

risks of ACT scan

Risks The amount of radiation involved is estimated to be around the same as a person would be exposed to in a space of between several months and several years of natural exposure in the environment. A scan is only given if there is a clear medical reason to do so. The results can lead to treatment for conditions that could otherwise be serious. When the decision is taken to perform a scan, doctors will ensure that the benefits outweigh any risk. Problems that could possibly arise from radiation exposure include cancer and thyroid issues. This is extremely unlikely in adults, and also unlikely in children. However, are more susceptible to the effects of radiation. This does not mean that health issues will result, but any CT scans should be noted on the child's medical record. In some cases, only a CT scan can show the required results. For some conditions, an ultrasound or MRI might be possible.

What is a mammogram? Mammograms are an important tool both the screening and in the diagnosis of breast cancer. The test involves placing your breast between two plates and using X-ray imaging to look for any suspicious findings. A mammogram alone cannot be used to diagnose breast cancer but can aid in the diagnosis by classifying normal or suspicious findings in detail. Mammograms can sometimes detect breast cancers in the earliest stages before any symptoms are present but can miss some cancers as well, especially in younger women who have dense breast tissue.

Risks Mammograms expose women to a small amount of radiation, the amount of which rarely causes illness. According to a 2016 study in the Annals of Internal Medicine, an estimated 125 of every 100,000 women who undergo an annual mammogram will develop radiation-induced breast cancer, of whom 16 (or 0.00016 percent) will die. (By comparison, among the same group of women, 968 breast cancer deaths could be avoided as a result of the mammograms.)

The risk of radiation from mammograms is expected to be higher in those who receive higher doses of radiation and in women who have larger breasts, as they require additional radiation to accurately view all breast tissue. For women who have breast implants, there is a small risk that an implant could rupture, and it's important to let the technician know you have implants before the procedure

Sources https://www.mydr.com.au/tests-investigations/mri-scan-magnetic-resonance-imaging https://en.wikipedia.org/wiki/X-ray_source https://www.verywellhealth.com/mammogram-what-to-expect-430283 https://www.nibib.nih.gov/science-education/science-topics/x-rays https://www.healthline.com/health/x-ray#followup https://www.medicalnewstoday.com/articles/219970.php#side-effects https://www.cdc.gov/cancer/breast/basic_info/mammograms.htm https://www.medicalnewstoday.com/articles/153201.php#uses...