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| Fig. 1: This shows the dosage of radiation based on the scan performed. (Courtesy of the DOE. Source: Wikimedia Commons) |
In modern-day medicine, Computed Axial Tomography (CAT scans, or CT scans) scans have become a common practice to provide further imagery in order to diagnose patients. The CT scan machine was initially invented in 1972 by two scientists, Godfrey Hounsfield and Allan Cormack to allow doctors to see the soft tissues which could not be captured by an X-Ray. The machine does this by capturing imagery in individual shots and piecing them together to provide an entire image to the radiologist all in the span of seconds. That being said, the scan emits high levels of radiation, which can be measured in millisieverts (mSv). [1] This radiation varies greatly based on the location of the scan, detail of the scan, and size of the patient. For example, one of the highest exposure tests is an abdominal CT scan. In this test, the patient is exposed to about 10 mSv of radiation, which is equal to 200 chest X-rays. This truly goes to show how much more powerful the CT scan is in terms of radiation, especially when it comes to making sure that each patient has the right dosage. Patients can be over-exposed to radiation if their measurements are not taken properly or the dose is not adequately. This can lead to massive levels of over-exposure, leading to a much higher health risks. [2]
While a single exposure to a CT scan is not life-altering, repeated exposure to high levels of ionizing radiation has been linked to cancer and other diseases. Ionizing radiation is defined as high energy wavelengths or particles that penetrate tissue to reveal the body's internal organs and structures, but in high quantities, have been known to cause damage to DNA, which can result in mutations later causing cancer. [3] As seen in Fig. 1, the amount of radiation exposure from just one head CT scan is enough exposure to overshadow years of limiting radiation exposure and impacts from radiation in many other life events. Depending on the test, the range of exposure to these rays varies. Each scan can have differing levels of radiation exposure, with head CT scans being one of the most concentrated. That being said, all CT scans are providing some type of risky exposure. The mSv radiation measurement varies from 0.001 for a simple X-Ray to 40.7 for a nuclear imaging cardiac stress test. Within the CT scan range, the mSv an be anywhere from 0.9 to 13.5 for just the radiation exposure of imagery. This is calculated based on the effective dose administered, which ranges from 0.4 to 12 mSv. [3] What is most concerning is the lack of accurate information reported on the radiation absorbed. In fact, the radiation impacts are often under-estimated and individuals are often not made aware of the long-term consequences of CT scans. In countries with mean of to mSv for radiation exposure among its population, the mortality rate of cancer is 0.97 sievert and can be a much larger risk to children and younger adults who are exposed earlier on in life. Radiation is a risk for malignancy in the form of cancer with the higher levels of exposure, especially with patients who have an exposure level greater than 100 mSv. [3]
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| Fig. 2: This is the imagery that is captured of a CT scan looking at a malignancy. Notice the focus on the left image on the specific mass in order to lessen radiation impact. (Source: Wikimedia Commons. |
One of the biggest ways to reduce this radiation is by finding the optimal dose for each patients radiation exposure based on type of scan, weight, and height. In order to calculate the Computed Tomography Dose Index (the CTDI), it requires measuring the Total area of D(z) under width T of central scan of multiple scan profiles = total area of single scan dose profile (including scatter tails). As seen in Fig. 2, the CT scan is focused on providing the right dosage by only concentrating on the specific area where the malignancy is determined to be.
In conclusion, the best ways to reduce the total impacts of radiation through CT scans would be a proper dosage for each patient as well as exhausting other options of imagery. Further, using more caution and lower mSv tests are the better response instead of rushing into a CT scan. According to a study conducted by the FDA, "30-50% of imaging tests are believed to be medically unnecessary". [1] The age at which individuals often get their first CT scans, particularly if in adolescence can have even higher rates of likelihood of attracting cancer later in life, especially if they are exposed to high levels of radiation before adulthood.
© Kaitlyn Claire Albertoli. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] K. Maher, Basic Physics of Nuclear Medicine (Platypus Global Media, 2011).
[2] S. G.Boodman, "Should You Worry about the Radiation from CT Scans?" Washington Post, 4 Jan 16.
[3] J. M. Albert, "Radiation Risk From CT: Implications for Cancer Screening," Am. J. Roentgenol. 201, W81 (2013).
