NMR in Imaging – Magnetic Resonance Imaging (MRI)


Nuclear Magnetic Resonance (NMR) is a trusted diagnostic and research tool, thriving on the basis of an intrinsic atomic property known as spin. By employing advanced physics processes, NMR is used to create detailed imaging outputs, most notably, the Magnetic Resonance Imaging (MRI). This article endeavors to dissect the significant field of NMR in imaging, with an intensive focus on MRI technique.

Understanding nuclear magnetic resonance (NMR):

The NMR technique comprises exploiting the quantum mechanical phenomena of nuclear spin. When placed in an external magnetic field, atomic nuclei, with intrinsic angular momentum or spin, align along the field lines. They can exist in two energy states: parallel (lower energy state) or anti-parallel (higher energy state) to the direction of the field.

When these aligned spins are subjected to a radio-frequency pulse resonant with the difference in energy between the two states, nuclei absorb this energy and leap from a lower energy state to a higher state. Once the applied pulse is removed, these nuclei relax back to their original ground state emitting energy in return, a process which is time-dependent. This emitted energy recorded is the NMR signal.

Nuclear Magnetic Resonance in Imaging:

One application of NMR is in MRI, displaying the distribution of water and fat in the human body. The hydrogen nuclei (protons) present in water and fat are utilized due to their high abundance in the body and large magnetic moments. The rate at which these protons return to their equilibrium states differs between tissues, allowing different tissues to be distinguished visually.

Improving Image Resolution: From NMR to MRI:

The utilization of gradient fields is what sets MRI apart from NMR. By applying additional magnetic fields with linear gradients, a spatial encoding of signals is achieved. This means protons from different regions within the body will resonate at different frequencies and can be distinguished. This spatial resolution allows for three-dimensional visualization of tissues, which is just not possible using standard NMR techniques.

Magnetic Resonance Imaging (MRI):

MRI is a non-invasive procedure that uses powerful magnets and an advanced computer system to produce high resolution, detailed, three-dimensional images of inside the body. As it circumvents the harmful ionizing radiations, MRI is leveraged extensively in medical diagnostics to detect, monitor, and characterise diseases.

MRI Sequence:

The typical MRI sequence consists of firstly, proton alignment after placing the body part in the main magnetic field. Second, the application of a radiofrequency pulse causing the protons to resonate. Third, signal detection after removing the pulse and lastly, the compilation of detected signals into an accurate image using Fourier transform methods.

Applications of MRI:

With an extraordinary ability to distinguish soft tissues, MRI is routinely used to diagnose a multitude of medical conditions. Brain MRIs can detect stroke, tumor, aneurysm while Spine MRI can spot nerve damage and bone degeneration. Joint and musculoskeletal MRIs can point to arthritis, ligament tear, or tendonitis. It also finds use in Cardiology, Oncology, Gastroenterology, and Radiology.


Exploring the power laid within the atomic properties of matter, scientists have employed NMR to revolutionize the field of diagnostic imaging with MRI. The invaluable technique of MRI, from the field of NMR, sets an extraordinary example of quantum physics’ impressive reach into practical life, enriching the humanity’s healthcare armory against diseases.

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