Dr. Ruchira Sarbajna
Director, Analytical Division, R&D Centre, Viatris India, Hyderabad
Many of us mostly in our childhood and in our old age suffer from fractures due to accidents and unintended falls. So, when one falls and breaks his bones what comes to your mind? Go to doctor and get an X-ray! With advancements in the field of medical research, use of Magnetic Resonance Imaging (MRI) is gaining more popularity than the age-old X-ray. Why is it so? According to information, an MRI is considered the best way to diagnose all kind of fractures. It can visualize lower grade stress injuries, tissue, cartilage injuries, minute cracks & chips in our body. These mostly go undetected in an X-ray. MRI is also better able to distinguish between stress fractures and soft tissue injuries. I will not go into further details of what the MRI can do; it is best left to the medical practitioners! However, this small machine has a big brother – Nuclear Magnetic Resonance (NMR) and this plays a very important role in the field of science specifically Organic Chemistry. Organic Chemistry is spread in various applied fields – Pharmaceuticals, Polymer; Food & additives. This is one equipment scientists working on a molecule can live without. What does an NMR do? Well, it helps us to identify the structure of a compound such as whether the compound which is liquid in nature is an alcohol or an acid or a ketone. The MRI images have better resolution and provide detailed and minute information including of the surrounding organs. Whereas the X-ray image has less resolution and much of the information is not legible (Figure 1).
In NMR, scientists see the chemical structure of the compound and the impact of the environment on certain molecules. The NMR is mainly restricted to few elements – Hydrogen, Carbon, Nitrogen, Fluorine and Phosphorous. Characteristic signals are generated from the hydrogens (protons) present in a compound which confirm the compound. For example, consider Benzene (C6H6) and Toluene (C6H5-CH3). 1 proton is replaced by a methyl (CH3) group. All the protons in the benzene are in the same environment hence we will expect a single signal from all the six protons. But for Toluene, the environment has changed since one proton has been replaced by a methyl group. So we should expect 2 signals because of the 2 different environments.
While NMR uses radiation frequencies to generate information, MRI uses radiation intensities to generate information. In NMR spectroscopy, it helps to determine the chemical structure of matter whereas in MRI imaging, the goal is to generate a detailed image of the body. Simply said, MRI is the medical application to the NMR. Both the instruments use large magnetic field (1Tesla and above) and radio frequencies to generate images of the internal body while the NMR allows precise analysis of molecular constitution in a chemical micro-environment. MRI is a useful non-invasive and non-destructive diagnostic tool for imaging soft tissues such as the brain, heart and muscles, and for discovering tumors in many organs. Together, NMR and MRI revolutionized the practice of chemistry and medicine by providing fast, non-destructive, and non-invasive means for the observation of matter from the atomic to the macroscopic scale. You may say, MRI is a smaller version of NMR (nuclear magnetic resonance). The magnetic field is measured in Tesla and MRI equipment is available at 0.7 ; 1 or 1.5 Tesla whereas in a 21 Tesla magnetic field, the hydrogen nuclei (commonly referred to as protons) resonate at 900 MHz in an NMR equipment!
Thus, I nomenclate MRI as the Chote Miya of the NMR which is the Bade Miya!