Writer: Dhakshayini Suresh
What is a CT scan and what is its purpose?
A computerized tomography (CT), also known as Computerized axial tomography (CAT) scans, is a method of capturing several X-rays of the human body and combining it to produce a detailed image of body structures. The process through which it is done is that the scanner emits successive narrow beams which can record varying levels of density in the body. For example, it can even detect tissues within an organ. The collected data is saved in a computer, which is programmed to create a 3-D cross-sectional image of the body part in focus and display it on the screen. Contrast dyes are also a typical part of the procedure to develop more clear pictures; this is because different chemicals can appear as different colors on the scans (Ex: Barium appears as white). CT scans are very useful tools for doctors to identify internal damages/problems within patients which will allow them to provide an accurate diagnosis. CT scans can gather images of soft tissues, pelvis, lungs, brain, abdomen, bones, etc. Most importantly, CT Scans are successful in detecting cancer because they reveal the presence of tumors within the body.
Alternatives to CT Scans:
X-Rays: X-rays are a type of radiation called electromagnetic waves. X-ray imaging creates pictures of the inside of your body. The images show the parts of your body in different shades of black and white. This is because different tissues absorb different amounts of radiation. Calcium in bones absorbs x-rays the most, so bones look white. Fat and other soft tissues absorb less and look gray. Air absorbs the least, so lungs look black.
The most familiar use of x-rays is checking for fractures (broken bones), but x-rays are also used in other ways. For example, chest x-rays can spot pneumonia. Mammograms use x-rays to look for breast cancer. X-Rays, unlike CT scans, use only one radiation beam and emit far less radiation but are also very limited in the information they provide about the human body.
MRIs: Magnetic Resonance Imaging (MRI) uses a strong magnetic field and radio waves to create detailed images of the organs and tissues within the body. MRIs are almost always preferable to CTs for imaging the head, and usually for the spine, except during trauma or when MRIs are not practical – such as when there are metal clips in the head. Even without the ionizing radiation, MRIs provide equal or superior imaging. Unfortunately, since MRIs take so much longer, children often need to undergo sedation, with its own risks, in order to remain still long enough for an MRI.
Side effects of using CT Scans:
Like other X-ray imaging exams, CT scans expose you briefly to a small, targeted amount of ionizing radiation. The radiation helps create an image of structures inside your body. Although cells repair damage by this radiation, sometimes these repairs are imperfect, leading to DNA mutations in later years. Research shows that this kind of radiation may damage your DNA and lead to cancer. Although the risk of radiation killing someone is very small, radiation’s effect adds up over one’s lifetime. So, one has an increased risk with every additional CT scan.
New Discovery that lowers radiation from CT Scanning:
A new technique, through the University College London, sought a way to split a full X-ray beam into thin beamlets that can deliver the same quality of image at a much reduced radiation dose. In the new study, published in Physical Review Applied, researchers applied a mask with tiny slits over an X-ray beam, breaking up the beam into “beamlets”. They then moved the sample being imaged in a cycloidal motion that ensured the whole object was irradiated quickly so that no parts of it were missed. Furthermore, the beamlets allow for a sharper resolution of the images because the part of the CT scanner that “reads” the information from the X-ray can locate where the information is coming from far more precisely.
According to Dr. Charlotte Hagen, first author of the paper, "Being able to reduce the dose of a CT scan is a long-sought goal. Our technique opens new possibilities for medical research and we believe that it can be adjusted for use in medical scanners, helping to reduce a key source of radiation for people in many countries."
How is it different in its mechanisms?
Primarily, Conventional CT scans involve an X-ray beam being rotated around the patient. The new "cycloidal" method combines this rotation with a simultaneous backwards and forwards motion. This allows for a better “reading” of the object. Moreover, Professor Sandro Olivo notes, "This new method fixes two problems. It can be used to reduce the dose, but if deployed at the same dose it can increase the resolution of the image. This means that the sharpness of the image can be easily adjusted using masks with different-sized apertures, allowing greater flexibility and freeing the resolution from the constraints of the scanner's hardware."
Limits of this invention:
The primary issue with this technology is that it is relatively new. It claims to be an effective alternative to regular CT scanning but further research needs to be conducted on how effective this technology can be for all parts of the human body. Specific examples were not explicitly noted which means it does not offer a guarantee. While the process appears simple, the cost in producing the mask with the slits, on a large scale, should be determined to recognize whether it can be produced on a large scale for all hospitals that hold CT scans. Further research with human trials should also be conducted before this technology is popularly used.
Ongoing areas of research in CT scanning:
Imaging integration with radiation treatment planning
Higher resolution imaging for scans while attempting to lower scanning time.
Develop/improve the quantitative accuracy of PET imaging by enabling methods that compensate for degradation from respiratory motion.
New methods of designing detectors and electronics that can be easily scaled for use in a wide range of imaging system designs
CT scanning accounts for about a quarter of all Americans’ exposure to radiation. Several scientists, including those mentioned in the study, are attempting to find ways to deflect this problem so that people can still have internal damage detected without fearing radiation side effects. This new technology is a minor yet imperative advancement in healthcare and CT scanning.
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Greene, A. (2019, June 18). CTs, MRIs, Ultrasounds: Differences, Risk & Benefits. DrGreene.Com. https://www.drgreene.com/ct-scans
Lam, P. (2018, July 24). What to know about MRI scans. Medical News Today. https://www.medicalnewstoday.com/articles/146309
New CT scan method lowers radiation exposure. (2020). ScienceDaily. https://www.sciencedaily.com/releases/2020/07/200723115909.htm
What Is a CT Scan? (2017, February 3). WebMD. https://www.webmd.com/cancer/what-is-a-ct-scan#2
X-Rays. (2020, August 14). Medline Plus. https://medlineplus.gov/xrays.html