In this blog post, we will examine the principles and differences between MRI and CT scans and check how well we understand them.
In modern society, the medical field is constantly advancing and improving. People are living longer than their ancestors and strive for a more prosperous and happy life. In this process, the importance of health is becoming increasingly prominent, and the human instinct to maintain a healthy life is strongly at work. Perhaps due to this innate human instinct to preserve life, the demand for and research into medicine is becoming increasingly important and promising in society. Furthermore, as the saying goes, ‘losing your health is losing everything,’ advances in medicine are contributing greatly not only to prolonging life but also to improving the quality of life.
Comprehensively speaking, medicine is represented by pharmaceuticals and surgery, but the most basic form of medicine is screening and treatment. From this perspective, when ordinary people visit a hospital, the most common medical services they receive are preventive regular check-ups and necessary treatments. However, many people do not fully understand the principles and procedures behind the various tests conducted during these processes. Therefore, I will explain two medical diagnostic technologies that are commonly received but whose principles and processes are often misunderstood: MRI and CT scans.
CT (Computed Tomography) involves entering a large circular machine equipped with an X-ray generator and taking images. Unlike simple X-ray imaging, CT scans obtain cross-sectional images of the body by slicing it horizontally. The X-ray generator consists of a high-voltage generator and an X-ray tube, with the X-ray tube serving as the source of X-rays. X-rays, as we all know, were discovered by Röntgen in the late 19th century and have since become a fundamental element of diagnostic imaging. Initially, the technology was very simple, but as it evolved, more precise and efficient imaging became possible. For example, the invention of the Coolidge tube revolutionized X-ray imaging technology, and subsequent research and development led to the creation of more powerful and sophisticated X-ray devices.
Additionally, high-voltage generators typically operate by first increasing the voltage through a step-up transformer to 100–200 V, then sending it to the main transformer to further increase it to 3595 kV. Depending on the application, this system can accommodate X-ray imaging ranging from approximately 20 kV for routine X-ray imaging to 150 kV for high-voltage imaging. In other words, voltage controls the quality of X-rays, current controls their intensity, and a control unit is also required to regulate the exposure time. The quality of X-rays improves as voltage increases, resulting in shorter wavelengths and higher penetration. Intensity increases proportionally with current. Based on these fundamental principles, CT offers the advantage of clearly visualizing structures and abnormalities with minimal overlap.
CT is the primary imaging modality when lesions are suspected and precise examination is required for most organs and diseases. It plays a crucial role in rapidly assessing a patient’s condition and determining treatment strategies, especially in emergency situations. For example, the speed and accuracy of CT in diagnosing conditions such as internal bleeding from traffic accidents or severe trauma can be life-saving.
On the other hand, MRI (Magnetic Resonance Imaging) involves placing a person in a strong magnetic field and then briefly emitting high-frequency waves that cause hydrogen atoms to emit radio waves. After a short time, the hydrogen atoms relax and re-emit the radio waves, which are then calculated by a computer to produce an image. MRI is particularly effective for diagnosing conditions such as muscle, ligament, and brain disorders due to its superior resolution and contrast in soft tissues. Another important advantage of MRI is that it does not use radiation. This eliminates the risk of radiation exposure that can occur when patients undergo repeated examinations.
MRI and CT are currently the most fundamental and essential diagnostic tests for determining the nature of lesions when diagnosing diseases and treating patients, despite the global reliance on new technologies in medical technology and the development of alternative diagnostic tests. Although these two imaging techniques use different principles and methods to obtain images, their ultimate purpose is to accurately assess a patient’s condition and provide appropriate treatment. Doctors use these tests to save the lives of fathers, mothers, sons, and daughters in a family, thereby helping patients better understand their illnesses.
As medical technology advances, various alternative technologies may be invented to reduce the risks associated with X-rays. However, without further development of existing technologies, such innovations would not be possible. MRI and CT are not merely relics of the past but essential tools driving current and future medical innovations. Despite their clear differences and distinct purposes, it is important to recognize that their common goal of protecting our bodies from harm is at the core of both MRI and CT.
