History and Development of MRI Scanning

Fig. 1: MRI Scan of the brain and spine. (Source: Wikimedia Commons).

Magnetic resonance imaging (MRI) was first accessible in the 1980's as evaluation recourse for surgical patients, especially in the digestive and urinary tracks. Magnets' radiofrequency and imaging provides useful pictures, which offer major advantages over other existing imaging techniques, as seen in Fig. 1. [1] MRI's appear to be safe because there is no use of ionizing radiation or iodinated contrast materials in the process. The biggest risk of an MRI scan is the projectile effect, which emphasizes the attraction of magnetic objects to the magnet in the scanner. Patients with rooted ferromagnetic objects and implants must take serious caution in the presence of an MRI. [2]

MRI scans are very complex and create many different magnetic reactions throughout a human body in order to produce the image that is needed. When a person enters the MRI scanner, the protons in the tissues, usually enclosed in water molecules, affiliate themselves in the pattern of the magnetic field. When the radiofrequency electromagnetic pulse is released from the scanner, the protons disperse and then realign into their original formation, which creates a signal. [2] This signal is then picked up by the computer and antenna and is converted into an image. Relaxation is the process by which the protons readjust themselves and protons go through two types of this process, T₁ and T₂. T₁ is longitudinal and places that are water-containing are shown as darkness, which makes it hard for T₁-weighted images to distinguish between normal and injured tissues. T₂-weighted images show great contrast between torn and assembled tissues, even though there is less anatomic detail compared to T_I imaging. [2]

Recent advances in MRI make gadolinium-based blood contrast agents available creating high-resolution pictures of the tree assessment of soft tissue vascularity function. [2] Introduction of endorectal coil now improves the quality of imagery in the analysis of different prostate cancers. Magnetic resonance urography is a recent development, which provides minute details of the collecting system and coronal section. [1] Intensity-modulated radiotherapy (IMRT) will provide clearer imaging of the prostate for analyzing cancer in patients, however, currently, the modality of imaging is too costly for experimental use. [3]

The limits and future dangers of magnetic resonance imaging is not yet determined. Data and research has suggested that combining high-speed MRI techniques with event-related task examples would potentially be used successfully to map brisk hemodynamic changes. [1]

© Jane Campbell. 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.

References

[1] M. A. Salam, Ed., Principles and Practice of Urology (Jaypee Bros. Medical, 2013).

[2] D. H. W. Grönemeyer, MD, et al., "Future of Advanced Guidance Techniques by Interventional CT and MRI," Mini. Invasiv. Ther. 4, 215 (1995).

[3] B. R. Rosen, R. L. Buckner, and A. M. Dale, "Event-Related Functional MRI: Past, Present, and Future," Proc. Natl. Acad. Sci. USA 95, 773 (1998).