Name: nmr spectra and mri imaging
Uploaded: 2024-04-04T10:51:39.000Z
Duration: 1 min 7 s
Channel: JoVE

K12 Standards

Pennsylvania State Academic Standards

9-12

Physical Science

Waves and Electromagnetic Radiation

3.2.9-12.X

Nuclear Magnetic Resonance (NMR): Overview

La risonanza magnetica nucleare, o NMR, è un fenomeno esibito da alcuni nuclei in grado di assorbire la radiazione a radiofrequenza caratteristica in condizioni specifiche.
La risonanza magnetica mobile è ampiamente applicata nella spettroscopia e nell'imaging medico.
In entrambe queste applicazioni, il campione o il soggetto viene posto in un campo magnetico e irradiato con energia a radiofrequenza.
La spettroscopia NMR fornisce informazioni dettagliate sugli ambienti elettronici degli atomi nel campione. Genera uno spettro che rappresenta le frequenze di assorbimento caratteristiche del campione rispetto alle intensità di picco.
Lo spettro NMR può rivelare le strutture molecolari dei composti organici e delle macromolecole biologiche e può mostrare processi dinamici insieme alla cinetica di reazione.
In medicina, la risonanza magnetica, comunemente chiamata risonanza magnetica, utilizza la risonanza magnetica mobile per generare immagini dettagliate di organi e tessuti interni.

risonanza magnetica nucleare (nmr): panoramica

La risonanza magnetica nucleare (NMR) è un fenomeno esibito da alcuni nuclei che possono assorbire la caratteristica radiazione a radiofrequenza in determinate condizioni. La NMR è stata ampiamente applicata nella spettroscopia molecolare e nell'imaging diagnostico medico. In entrambe queste applicazioni, la molecola o il soggetto in studio viene posto in un campo magnetico e irradiato con energia a radiofrequenza.

La spettroscopia NMR genera uno spettro in cui le frequenze di assorbimento caratteristiche del campione vengono tracciate rispetto alle intensità di picco. Lo spettro NMR fornisce informazioni dettagliate sugli ambienti elettronici degli atomi nel campione. L'interpretazione dello spettro può aiutare a identificare le strutture molecolari dei composti organici e delle macromolecole biologiche, nonché a comprendere i processi dinamici insieme alla cinetica di reazione.

In medicina, la risonanza magnetica, comunemente chiamata MRI, è una tecnica di imaging non invasiva che evita l’uso di radiazioni dannose. La risonanza magnetica utilizza la risonanza magnetica per generare immagini dettagliate di organi e tessuti interni.

Risonanza Magnetica Nucleare (NMR): Panoramica

La risonanza magnetica nucleare (NMR) è un fenomeno esibito da alcuni nuclei in grado di assorbire la caratteristica radiazione a radiofrequenza sotto determinati ...

Education

Didattica

JoVE Core

Analytical Chemistry

Chimica Analitica

Unit 1

Unità 1

Principles of Nuclear Magnetic Resonance

Principi della Risonanza Magnetica Nucleare

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

nmr spectra and mri imaging

Nuclear magnetic resonance, or NMR, is a phenomenon that certain nuclei can show when they absorb radio frequency energy under the right conditions. Scientists use it in molecular spectroscopy and in medical imaging. In both cases, the sample or the person being studied is placed in a magnetic field and exposed to radio frequency energy.

In NMR spectroscopy, the result is a spectrum. This spectrum plots the absorption frequencies of the sample against peak intensity. The pattern gives detailed information about the electronic environments of atoms in the sample.

That information can help scientists identify the structures of organic compounds and biological macromolecules. It can also help explain dynamic processes and reaction kinetics, which is the study of how reactions change over time.

In medicine, NMR supports magnetic resonance imaging, or MRI. MRI is a noninvasive imaging method, so it avoids harmful radiation. It uses NMR to create detailed images of internal organs and tissues.

NMR Spectra and MRI Imaging

nuclear magnetic resonance (nmr): overview

Nuclear magnetic resonance, or NMR, is a phenomenon that certain nuclei can show when they absorb radio frequency energy under the right conditions. Scientists use it in molecular spectroscopy and in medical imaging. In both cases, the sample or the person being studied is placed in a magnetic field and exposed to radio frequency energy. In NMR spectroscopy, the result is a spectrum. This spectrum plots the absorption frequencies of the sample against peak intensity. The pattern gives detailed...

atomic nuclei: nuclear spin

Nuclear Spin and NMR-Active Nuclei

Atomic nuclei have nuclear spin, which comes from the spins of their protons and neutrons. These particle spins are intrinsic angular momentum, and each electron, proton, and neutron has a spin value of 1/2. In nuclei, proton spins pair with other protons, and neutron spins pair with other neutrons. They do not pair with each other, so the final nuclear spin depends on which nucleons are left unpaired. Even numbers of protons do not add to the nuclear spin, and even numbers of neutrons do not...

atomic nuclei: nuclear magnetic moment

Nuclear Spin States and Magnetic Alignment

Atomic nuclei can act like tiny magnets when they have a nonzero spin. Because they are positively charged and rotating, they generate a magnetic field and a magnetic moment. In the absence of an external magnetic field, this magnetic moment points in random directions. When an external magnetic field, B0, is applied, the nuclear magnetic moments can line up with the field or against it. These two directions create 2I + 1 orientations. A hydrogen nucleus is a proton, and it has spin 1/2, so it...

atomic nuclei: nuclear spin state overview

atomic-nuclei-nuclear-spin-state-overview

Zeeman Splitting in Nuclear Spin States

NMR-active nuclei have spin states that describe the orientation of their nuclear magnetic moments. Without a magnetic field, these moments point in random directions, and the spin states are degenerate, meaning they have the same energy. When an external magnetic field is applied, the nucleus can only take on 2I + 1 orientations, where I is the nuclear spin. A proton with spin 1/2 has two possible orientations. A quadrupolar nucleus with spin 1 has three possible orientations. The...

atomic nuclei: nuclear spin state population distribution

atomic-nuclei-nuclear-spin-state-population-distribution

Nuclear Spin Populations and NMR Signal

Nuclear spin populations help explain why NMR signals appear. In a magnetic field, nuclei can occupy a lower energy spin-up state or a higher energy spin-down state. Near absolute zero, most nuclei stay in the lower energy state. As temperature rises, thermal collisions spread the spins more evenly between the two states. The balance between the spin −1/2 and spin +1/2 populations is described by the Boltzmann distribution equation. In this equation, ΔE is the energy difference, k is the...

atomic nuclei: larmor precession frequency

atomic-nuclei-larmor-precession-frequency

Magnetic Field and Nuclear Precession

Magnetic field strength controls nuclear precession in NMR. A spinning nucleus has a magnetic moment, and that moment turns around an external magnetic field directed along the z-axis. This motion is called Larmor precession, and its angular frequency is the Larmor frequency. The Larmor frequency is directly proportional to the applied magnetic field, B0. The proportionality constant is the gyromagnetic ratio, gamma. This value is fixed for each nucleus because every nucleus has its own ratio...

atomic nuclei: magnetic resonance

Nuclear Spins and Resonance in a Magnetic Field

Nuclear spins can line up in a magnetic field and create nuclear magnetic resonance. In the lower energy state, slightly more spins are aligned than in the higher energy state. That small difference gives the nuclei a net magnetization along the z axis.

atomic nuclei: nuclear relaxation processes

atomic-nuclei-nuclear-relaxation-processes

Nuclear Spin Alignment and Relaxation

Nuclear spin alignment and relaxation describe how nuclear spins respond to a magnetic field and then return to equilibrium. Without an external magnetic field, nuclear spin states are degenerate, meaning they have the same energy, and the spins are randomly oriented. When a magnetic field is applied, the spins begin to precess, or wobble, and orient themselves either along the field in a lower energy state or against it in a higher energy state. At equilibrium, a slight excess of spins...

atomic nuclei: types of nuclear relaxation

atomic-nuclei-types-of-nuclear-relaxation

NMR Relaxation Paths in Atomic Nuclei

Nuclear relaxation in atomic nuclei helps restore the balance between energy levels in NMR systems. It occurs through two main paths: spin-lattice relaxation and spin-spin relaxation. Both are first-order exponential decay processes. Spin-lattice relaxation is also called longitudinal relaxation. In this process, excited spins give energy to the surrounding lattice as they move back to the lower energy level. Magnetic dipolar interactions are an important part of this mechanism. A common...

nmr spectrometers: overview

How NMR Spectrometers Record Signals

NMR spectrometers record signals from samples that contain NMR-active nuclei. The system uses a strong magnet, a radiofrequency transmitter, and a detector connected to a computer console. These parts work together to measure and display the spectrum of the sample. Early NMR instruments were continuous-wave spectrometers. In a frequency-sweep method, the magnetic field stays fixed while the rf signal is swept. In a field-sweep method, the radiofrequency signal stays fixed while the magnetic...

nmr spectrometers: radiofrequency pulses and pulse sequences

nmr-spectrometers-radiofrequency-pulses-and-pulse-sequences

NMR Pulse Angles and Signal Collection

NMR pulse angles and signal collection explain how radiofrequency energy starts a measurement. A pulse is a short burst of radio waves spread across a range of frequencies. It excites the nuclei in the sample at the same time. When a radiofrequency pulse is applied along the x-axis, nuclei absorb energy that matches their Larmor frequencies and reach resonance. The net magnetization vector moves away from the z-axis and toward the transverse plane. This rotation angle is called the flip angle.

nmr spectrometers: resolution and error correction

nmr-spectrometers-resolution-and-error-correction

NMR Peak Shape and Magnetic Field Shimming

NMR peak shape depends on the signal created after magnetic nuclei resonate and relax. The detected free induction decay is approximately exponential. When that decay is Fourier transformed, it becomes a Lorentzian peak in the frequency domain. A Lorentzian peak in an NMR spectrum is described by its amplitude, full width at half maximum, and position. Its width is governed by the spin-spin relaxation time alone. In real experiments, the sample and probe can make the magnetic field...

diamagnetic shielding of nuclei: local diamagnetic current

diamagnetic-shielding-of-nuclei-local-diamagnetic-current

How Electron Density Shields Nuclei in NMR

Electron density around a nucleus affects how strongly it is shielded in NMR spectroscopy. When an applied magnetic field acts on a molecule, the electrons begin to circulate. This creates a local diamagnetic current within the molecule. The circulating sigma-bonding electrons produce a local magnetic field, B local, that opposes the applied field, B0. The nucleus then feels an effective magnetic field, which is the difference between the applied field and the local field. This effect is...

key terms and concepts

Explore how NMR creates spectra in chemistry and supports MRI in medicine. Learn how magnetic fields and radio frequency energy reveal structures and images.

NMR Spectra and MRI Imaging | JoVE K12

analytical chemistry

JoVE Core Analytical Chemistry simplifies complex chemical principles by breaking them down into clear, engaging animations, making topics from SI Units to NMR spectroscopy more accessible and straightforward. Additionally, the scientist-in-action videos highlight the application of these concepts in real-world research conducted in laboratories globally.

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Velocity and Acceleration of a Wave

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Problem-Solving: Tuning of a Guitar String

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Energy and Power of a Wave

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3.2.9-12.T

Interference and Superposition of Waves

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Two ...

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Propagation Speed of Electromagnetic Waves

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Momentum And Radiation Pressure

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Students who demonstrate understanding can evaluate the claims, evidence, and reasoning behind the idea that electromagnetic radiation can be described either by a wave model or a particle model and that for some situations one model is more useful than the other.  Clarifying Statement: Emphasis is on how the experimental evidence supports the claim and how a theory is generally modified in light of new evidence.  Examples of a phenomenon could include resonance, interference, diffraction, and photoelectric effect.  Assessment Boundry: Assessment does not include using quantum theory.

3.2.9-12.V

Absorption of Radiation

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Students who demonstrate understanding can evaluate the validity and reliability of claims in published materials of the effects that different frequencies of electromagnetic radiation have when absorbed by matter.  Clarifying Statement: Emphasis is on the idea that photons associated with different frequencies of light have different energies, and the damage to living tissue from electromagnetic radiation depends on the energy of the radiation.  Examples of published materials could include trade books, magazines, web resources, videos, and other passages that may reflect bias.  Assessment Boundry: Assessment is limited to qualitative descriptions.

3.2.9-12.W

Energy Transfer in Chemical Reactions

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Interaction of EM Radiation with Matter: Spectroscopy

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Molecular Spectroscopy: Absorption and Emission

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Ultraviolet and Visible (UV&ndash;Vis) Spectroscopy: Overview

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Infrared (IR) Spectroscopy: Overview

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Raman Spectroscopy: Overview

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NMR Spectra and MRI Imaging

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