Related Experiment Video
Updated: Jul 25, 2026
17:16
Registered Bioimaging of Nanomaterials for Diagnostic and Therapeutic Monitoring
Published on: December 10, 2010
Analytical approach to the MR signal
1School of Electrical and Computer Engineering, University of Oklahoma, Norman, Oklahoma 73019-1023, USA. ibrahim@ou.edu
Magnetic Resonance in Medicine
|August 10, 2005
Summary
This study analyzes magnetic resonance (MR) signals using reciprocity. The principle explains NMR signal reception but not spin excitation due to asymmetric permeability tensors.
Area of Science:
- Physics
- Magnetic Resonance Imaging (MRI)
- Nuclear Magnetic Resonance (NMR)
Background:
- The principle of reciprocity is a fundamental concept in electromagnetics.
- Its application to magnetic resonance (MR) signal analysis, particularly concerning spin excitation and reception, requires careful consideration of system asymmetries.
Purpose of the Study:
- To analytically evaluate the MR signal using the principle of reciprocity for arbitrary transmit and receive probes.
- To investigate the applicability of the standard reciprocity principle to spin excitation and NMR signal reception.
Main Methods:
- Analytical evaluation of the MR signal based on the principle of reciprocity.
- Examination of spin excitation considering the permeability tensor of transverse magnetization.
- Application of the standard reciprocity principle to calculate the NMR signal during reception.
Main Results:
- The standard principle of reciprocity is insufficient to explain spin excitation due to asymmetric permeability tensors in transverse magnetization.
- The NMR signal strength during reception is determined by the receive coil's circularly polarized field component.
- This component must have an opposite rotational sense to the excitation field for optimal signal detection.
Conclusions:
- The principle of reciprocity is applicable to the reception stage of NMR signal generation.
- Spin excitation in MR requires modifications to the standard reciprocity principle to account for material property asymmetries.
- Understanding these principles is crucial for optimizing MR coil design and signal interpretation.
Related Concept Videos
01:13¹H NMR: Complex Splitting
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
01:02¹H NMR: Interpreting Distorted and Overlapping Signals
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
00:58¹H NMR Signal Integration: Overview
The intensity of a signal, which can be represented by the area under the peak, depends on the number of protons contributing to that signal. The area under each peak is shown as a vertical line called an integral, with the integral value listed under it, as seen in the proton NMR spectrum of benzyl acetate. Each integral value is divided by the smallest integral value to obtain the ratio of the number of protons producing each signal. The ratio reveals the relative number of protons and not...
01:10Interpreting ¹H NMR Signal Splitting: The (n + 1) Rule
In the AX proton spin system, proton A can sense the two spin states of a coupled proton X, resulting in a doublet NMR signal with two peaks of equal (1:1) intensity. When proton A is coupled to two equivalent protons (AX2 spin system), the spin states of each X can be aligned with or against the external field, creating three possible scenarios. This results in a 1:2:1 triplet signal, where the central peak corresponds to the chemical shift of A and is twice as large or intense as the others.
01:25Applications Of NMR In Biology
Nuclear magnetic resonance (NMR) spectroscopy is a very valuable analytical technique for researchers. It has been used for more than 50 years as an analytical tool. F. Bloch and E. Purcell formulated NMR in 1946 and won the 1952 Nobel Prize in Physics for their work. Biological macromolecules such as proteins, nucleic acids, lipids, and organic molecules including pharmaceutical compounds, can be studied using this versatile tool that exploits the magnetic properties of certain nuclei.
The...
The...
01:24Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is a noninvasive medical imaging technique based on a phenomenon of nuclear physics discovered in the 1930s, in which matter exposed to magnetic fields and radio waves was found to emit radio signals. In 1970, a physician and researcher named Raymond Damadian noticed that malignant (cancerous) tissue gave off different signals than normal body tissue. He applied for a patent for the first MRI scanning device in clinical use by the early 1980s. The early MRI...