Introduction
A CAT scan, also known as a computed tomography (CT) scan, is a medical imaging technique that uses x-rays and computer processing to create cross-sectional images of the body (Source 1). CAT scans allow doctors to see detailed images of organs, bones, soft tissues and blood vessels. They are used to diagnose and monitor diseases, injuries, and other medical conditions.
The use of CAT scans has increased dramatically in recent years. While CAT scans provide valuable medical information, there is growing concern about the potential cancer risks from radiation exposure. Recent studies have suggested that the relatively high radiation doses delivered by some CAT scans may increase lifetime cancer risk (Source 2). This has prompted increased scrutiny over when CAT scans are medically justified versus when other lower-dose imaging alternatives might be reasonable.
How CAT Scans Work
CAT scans, also known as CT or computed tomography scans, are a type of X-ray imaging test. They combine multiple X-ray images taken from different angles to produce cross-sectional views and 3D images of internal organs and structures (Medical News Today, https://www.medicalnewstoday.com/articles/153201).
During a CAT scan, the patient lies on a table that slides into a large, tunnel-like machine. The machine rotates around the body and sends narrow beams of X-rays through the area being examined. As the X-rays pass through the body, they are picked up by detectors inside the scanner. The detectors measure the X-ray intensity and feed this information into a computer. The computer analyzes the data to create cross-sectional images of the body, which can then be examined on a monitor by a radiologist (Hopkins Medicine, https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/computed-tomography-ct-scan).
By combining many X-ray images taken from different angles, CAT scans provide more detailed information than conventional X-rays. They allow doctors to see tissues, organs, bones and blood vessels from multiple viewing angles. This helps diagnose conditions accurately and plan proper treatments.
Radiation Exposure from CAT Scans
CAT scans, also known as CT scans, use X-rays to take detailed pictures inside the body. The radiation exposure from a CT scan is much higher than conventional X-rays. According to the FDA, the effective doses from diagnostic CT scans are typically 1-10 mSv, compared to 0.1 mSv for a chest X-ray (FDA).
The amount of radiation depends on the type of CT scan. A CT scan of the abdomen and pelvis delivers about 10 mSv, while a head CT scan is around 2 mSv (WebMD). To put this in perspective, 10 mSv is comparable to 3 years of background radiation exposure, while 2 mSv is similar to 7 months.
By comparison, a chest X-ray delivers around 0.1 mSv, equivalent to 10 days of background radiation. Cell phone radiation exposure is about 0.00093 mSv per year. Even a long international flight is only 0.003-0.04 mSv (Harvard Health).
While CT scans involve more radiation than other imaging tests, the exposure needed for diagnostic tests remains relatively low compared to these other common sources of radiation.
Potential Risks of Radiation
Exposure to radiation, even at low doses from CAT scans, does carry potential health risks. The most concerning risk is an increased chance of developing cancer later in life. Ionizing radiation has been shown to cause DNA damage that can lead to cancerous mutations (EPA). The likelihood of developing cancer from radiation exposure increases along with the radiation dose. Patients receiving multiple CT scans over time accumulate greater exposure and have a higher cancer risk.
There are also concerns about possible effects beyond cancer. Studies have found potential links between radiation exposure and Circulatory diseases, cataracts, endocrine problems, cognitive impairment in children, premature aging, birth defects, and more. However, these other effects typically require higher radiation doses and the research is not yet conclusive (CDC). More research is still needed on the full scope of health effects from lower CAT scan radiation doses.
Protective Measures
There are several ways to reduce radiation exposure from CAT scans through protective measures. Proper shielding of sensitive organs not being directly imaged can help absorb scattered radiation and lower overall dose. This can be done through lead shielding devices or simply by having the patient cover sensitive areas with their hands or a lead apron (McCollough, 2009).
Dose regulation is also important, as many imaging facilities are taking steps to lower default radiation levels on their scanners below maximum levels. This ensures patients only get the minimum dose necessary for diagnostic quality images. Newer CT scanner technology like iterative reconstruction has enabled up to 50-75% radiation dose reduction while maintaining image quality (Yu, 2009). Continued innovation and regulation will be key to reducing CT radiation exposure over time.
Patient Considerations
Children are more susceptible to the harmful effects of radiation exposure from CAT scans compared to adults. Their cells are still rapidly dividing and growing, making them more vulnerable to DNA damage that could eventually lead to cancer later in life (https://www.cancer.gov/about-cancer/causes-prevention/risk/radiation/pediatric-ct-scans). Radiation exposure is cumulative over a lifetime, so multiple CAT scans or other imaging tests using radiation during childhood can significantly increase the risks.
Due to these concerns, alternatives like ultrasound or MRI should be considered for pediatric patients when possible. Ultrasound uses no ionizing radiation and MRI utilizes strong magnetic fields instead. While these modalities have some limitations compared to CAT scans, they may still provide the needed diagnostic information with less potential harm (https://pubs.rsna.org/doi/full/10.1148/radiol.2019181753). If a CAT scan is deemed medically necessary for a child, the lowest possible radiation dose should be used.
Overall, the risks versus benefits must be carefully weighed when ordering CAT scans for pediatric patients. Their long-term health and cancer susceptibility should be prioritized, favoring alternative imaging without radiation when feasible.
Provider Guidance
Healthcare providers should follow principles of ALARA (As Low As Reasonably Achievable) when ordering CT scans to minimize radiation exposure risk to patients. The ACR recommends only ordering CT scans when there is a clear medical benefit that outweighs the radiation risk. Providers should use the lowest dose necessary to obtain diagnostic image quality.
To follow ALARA principles, providers can take steps such as adjusting scan parameters based on patient size, using shielding, minimizing repeat scans, and avoiding multiphase scans when possible. Selected area or limited field-of-view scans can also reduce exposure. The ACR-ASNR CT Dose Check voluntary dose registry allows providers to compare their scan doses to regional and national benchmarks.
Referring providers should communicate necessary clinical information to the radiologist to allow appropriate protocol optimization. Radiologists should tailor protocols to answer the clinical question at the lowest reasonable dose. Ongoing education and protocol review helps ensure dose optimization.
Benefit vs. Risk Analysis
Doctors carefully weigh the medical need versus radiation risk when ordering CT scans for patients. According to the FDA, the benefits of an accurate diagnosis far outweigh the small risk posed by radiation exposure from a CT scan for most patients [1]. CT scans provide valuable diagnostic information that would be difficult or impossible to obtain otherwise.
However, the radiation exposure from CT scans is higher compared to conventional X-rays. According to RadiologyInfo.org, the radiation dose from a CT scan is about 50-500 times that of a conventional X-ray [2]. While the risk of developing cancer from the radiation exposure of one or a few scans is very small, this risk increases with multiple CT scans over time.
Therefore, doctors consider the patient’s medical history and only recommend CT scans when the clinical benefits outweigh the risks. They use the lowest radiation dose possible for adequate image quality. For some patients, such as children and young adults, doctors give special consideration to radiation concerns and utilize alternative imaging methods when feasible.
Conclusion
In summary, CAT scans utilize x-rays and produce higher radiation exposure than routine x-rays. While there are potential cancer risks from the radiation exposure, the benefits often outweigh these risks when the scan is medically justified. Patients should discuss with their doctor whether a CAT scan is appropriate for their situation. If so, providers can take steps to limit radiation exposure when possible, like adjusting scanner settings based on patient size. With reasonable precaution, CAT scans are a safe and useful diagnostic imaging tool when used judiciously.
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