How the MRI machine works 
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Magnetic resonance imaging (MRI) is a sophisticated medical imaging technique used to produce detailed images of the internal structures of the human body. The basic principle of operation of an MRI machine is the interaction of magnetic fields and radio waves with hydrogen nuclei (protons) present in the tissues of the body. This complex process produces high-resolution images that help diagnose a wide range of diseases.
The history of the invention of the MRI machine goes back to the mid-20th century, and many scientists and researchers took part in its creation. In the early 1970s, Raymond Damadian, a physician and scientist, conducted pioneering research into the concept of using nuclear magnetic resonance (NMR) to detect cancerous tissue in the human body. His work laid the foundation for the creation of the first MRI scanner. At the same time, chemist Paul Lauterbur and physicist Sir Peter Mansfield made significant breakthroughs in improving the imaging process by developing methods for spatial encoding of the signals produced by NMR. Their combined efforts led to the creation of the modern MRI machine, which revolutionized medical imaging.
The operation of an MRI machine involves several complex steps that culminate in obtaining accurate anatomical images. First, the patient is placed in an opening of the MRI scanner, which contains a powerful magnet. This magnet produces a strong magnetic field, usually between 0.5 and 3 Tesla (T), depending on the type of MRI machine. The magnetic field aligns the hydrogen nuclei inside the body along its direction, giving these nuclei a magnetic moment.
Radiofrequency (RF) pulses are then applied to the body, causing the hydrogen nuclei to absorb energy and move to a higher energy state. After the radio frequency pulse is turned off, the nuclei release the absorbed energy in the form of electromagnetic radiation known as NMR signals. These signals are detected by specialized coils in the MRI machine, which pick up weak radio frequency signals emitted by excited hydrogen nuclei.
The detected NMR signals undergo complex processing, including Fourier transform, to recover spatial information about the distribution of hydrogen nuclei in the body. By manipulating magnetic field gradients during scanning, MRI machines produce cross-sectional images of the body with exceptional clarity and detail. In addition, modern MRI sequences such as T1-weighted, T2-weighted, and diffusion-weighted images provide insight into various tissue characteristics and pathological changes.
One of the key benefits of MRI is the ability to image soft tissues such as the brain, spinal cord, muscles and organs with unmatched precision. Unlike other imaging techniques such as X-rays and CT scans, MRI does not use ionizing radiation, making it safe for repeated use, especially in children and pregnant patients. In addition, MRI’s multiplanar capabilities allow physicians to study anatomical structures from multiple perspectives, facilitating accurate diagnosis and treatment planning.
Over the years, advances in MRI technology have led to the development of specialized imaging techniques designed for specific clinical applications. For example, functional MRI (fMRI) can visualize brain activity by detecting changes in blood flow and oxygen saturation levels. Diffusion tensor imaging maps white matter tracts in the brain, which helps in the assessment of neurological conditions such as stroke and multiple sclerosis.
In conclusion, it should be noted that the operating principle of the MRI machine is based on the principles of nuclear magnetic resonance and electromagnetic induction. Through the collaborative efforts of pioneering scientists and engineers, MRI has emerged as a versatile imaging modality with a wide range of clinical applications. From humble beginnings to today’s capabilities, MRI continues to play a key role in modern medicine, offering a non-invasive and detailed look into the inner workings of the human body.