Atomic Structure and Motion Quiz
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Questions and Answers

What key elements in the human body are mentioned as being relevant to MRI?

  • Hydrogen, Sodium, Calcium, Potassium
  • Hydrogen, Oxygen, Carbon, Nitrogen (correct)
  • Hydrogen, Iron, Magnesium, Chlorine
  • Hydrogen, Phosphorus, Iodine, Chlorine

    • Which motion does not occur within an atom?

  • The nucleus rotating around a planet (correct)
  • The nucleus itself spinning about its own axis
  • Electrons orbiting the nucleus
  • Electrons spinning on their own axis

    • Which of the following nuclei is considered MR-active?

  • 15N (nitrogen) (correct)
  • 18O (oxygen)
  • 14C (carbon)
  • 12C (carbon)

    • What is the primary reason hydrogen is used as the main MR-active nucleus in MRI?

    <p>It is abundant in the human body.</p> Signup and view all the answers

    What does Faraday’s law of electromagnetic induction describe?

    <p>A magnetic field created by a charged moving particle.</p> Signup and view all the answers

    What does the magnetic moment of a nucleus represent?

    <p>The axis of north/south magnetic strength.</p> Signup and view all the answers

    Which of the following statements about the hydrogen nucleus is true?

    <p>It consists of a single proton with no neutrons.</p> Signup and view all the answers

    Which of the following is NOT a type of motion present within an atom?

    <p>Electrons collapsing</p> Signup and view all the answers

    What does AP stand for in anatomical terms?

    <p>Anteroposterior</p> Signup and view all the answers

    What is the primary use of the CISS sequence?

    <p>High-resolution 3-D imaging of the inner ear</p> Signup and view all the answers

    Which technique is used for fluid suppression in brain studies?

    <p>Turbo inversion recovery sequence</p> Signup and view all the answers

    What does DESS stand for?

    <p>Dual echo steady state</p> Signup and view all the answers

    What is the definition of acquisition time?

    <p>Time required to collect the image data</p> Signup and view all the answers

    What are the characteristics of dual echo sequences?

    <p>Two readout times for one TR combining proton-density and T2 weighting</p> Signup and view all the answers

    Which of the following describes the purpose of ECG triggering?

    <p>Data acquisition during specific phases of the cardiac cycle</p> Signup and view all the answers

    What is a characteristic of 3-D measurement in imaging?

    <p>Imaging of the entire volume of interest</p> Signup and view all the answers

    What occurs to the magnetic moments of hydrogen nuclei in the absence of an applied magnetic field?

    <p>They orientate randomly and produce no overall magnetic effect.</p> Signup and view all the answers

    What is the result of magnetic moments aligning parallel to the main magnetic field (B0)?

    <p>They result in net magnetization (M0).</p> Signup and view all the answers

    What does the precession frequency (w0) depend on according to the Larmor equation?

    <p>The gyromagnetic ratio and the magnetic field strength.</p> Signup and view all the answers

    What happens to hydrogen nuclei at higher magnetic field strengths?

    <p>They exhibit different precessional frequencies.</p> Signup and view all the answers

    How is the precessional frequency of hydrogen at 1.5 T expressed?

    <p>It is 63.87 MHz.</p> Signup and view all the answers

    What characterizes the net magnetic vector (NMV) when magnetic moments align anti-parallel to B0?

    <p>It represents high energy.</p> Signup and view all the answers

    What is true about the gyromagnetic ratio (γ) in relation to different MR-active nuclei?

    <p>It is a constant for a given MR-active nucleus.</p> Signup and view all the answers

    What occurs when hydrogen nuclei are placed parallel to the main magnetic field?

    <p>They behave with low energy.</p> Signup and view all the answers

    What is the primary purpose of using ECG triggering during data acquisition in MRI?

    <p>To ensure data is collected at specific heart phases</p> Signup and view all the answers

    Which statement best describes dual echo sequences in MRI?

    <p>They allow for simultaneous collection of proton-density and T2-weighted images.</p> Signup and view all the answers

    What is the significance of the CISS sequence in MRI?

    <p>It targets high-resolution imaging of the inner ear.</p> Signup and view all the answers

    In the context of MRI, what does the term 'Dark fluid' refer to?

    <p>A long TI sequence used for fluid suppression.</p> Signup and view all the answers

    What does the process of acquisition time in MRI refer to?

    <p>The duration required for gathering image data.</p> Signup and view all the answers

    Which type of coils are mentioned in the context of signal transmission in MRI?

    <p>Transmission, reception, and combined coils.</p> Signup and view all the answers

    Which imaging technique is defined by exciting the entire volume of interest instead of a single slice?

    <p>3-D measurement.</p> Signup and view all the answers

    What characterizes the DESS sequence in MRI imaging?

    <p>It features both axial and transverse magnetization in the signal.</p> Signup and view all the answers

    What is the orientation of hydrogen nuclei when they align parallel to the main magnetic field (B0)?

    <p>Low energy</p> Signup and view all the answers

    Which statement accurately describes precession frequency?

    <p>Precession frequency is determined by the Larmor equation.</p> Signup and view all the answers

    What happens to the overall magnetic effect of hydrogen nuclei in the absence of an applied magnetic field?

    <p>They have a magnetic moment but no alignment.</p> Signup and view all the answers

    At a magnetic field strength of 1.5 T, what is the precessional frequency of hydrogen?

    <p>63.87 MHz</p> Signup and view all the answers

    Which characteristic of the net magnetic vector (NMV) corresponds to the alignment of hydrogen nuclei anti-parallel to the main magnetic field (B0)?

    <p>High energy</p> Signup and view all the answers

    What does the gyromagnetic ratio (γ) signify in the context of MR-active nuclei?

    <p>It is a constant for each MR-active nucleus.</p> Signup and view all the answers

    In the Larmor equation, which variable represents precession frequency?

    <p>ω0</p> Signup and view all the answers

    At which magnetic field strength is the precessional frequency of hydrogen nuclei the lowest according to the provided information?

    <p>0.5 T</p> Signup and view all the answers

    What primarily determines the magnetic moment of a hydrogen nucleus in MRI?

    <p>Single proton's spin and charge</p> Signup and view all the answers

    Which motion is NOT associated with the atomic structure described?

    <p>Protons exchanging positions within the nucleus</p> Signup and view all the answers

    What is the reason behind the use of protium in MRI imaging?

    <p>It has a solo proton which provides a large magnetic moment</p> Signup and view all the answers

    What does Faraday's law of electromagnetic induction imply about the behavior of charged particles?

    <p>A moving charged particle generates both an electric field and a magnetic field</p> Signup and view all the answers

    Which component of an atom makes up most of its mass?

    <p>Protons and neutrons within the nucleus</p> Signup and view all the answers

    What best describes the function of hydrogen's magnetic moment in MRI?

    <p>It aligns with external magnetic fields, enhancing signal detection</p> Signup and view all the answers

    Which of the following nuclei does NOT qualify as MR-active?

    <p>12C (carbon)</p> Signup and view all the answers

    What happens when the magnetic moments of hydrogen nuclei are aligned anti-parallel to the main magnetic field?

    <p>They result in a reduction of net magnetization</p> Signup and view all the answers

    What is the primary characteristic of the CISS sequence in MRI imaging?

    <p>It is heavily T2-weighted and used for high-resolution imaging.</p> Signup and view all the answers

    Which of the following best describes the dual echo measurement in MRI?

    <p>It employs two distinct readout times for acquiring images.</p> Signup and view all the answers

    In MRI, what does the term 'Dark fluid' specifically refer to?

    <p>A long TI technique used to suppress cerebrospinal fluid in T2-weighted images.</p> Signup and view all the answers

    Which statement accurately reflects the purpose of ECG triggering in MRI?

    <p>It synchronizes image acquisition with specific phases of the cardiac cycle.</p> Signup and view all the answers

    What distinguishes a 3-D measurement technique from traditional imaging methods in MRI?

    <p>It captures the entire volume of interest in one imaging pulse.</p> Signup and view all the answers

    What does the acronym DESS stand for in the context of MRI imaging sequences?

    <p>Dual echo steady state.</p> Signup and view all the answers

    Which type of coil is specifically known for enhancing signal reception in MRI?

    <p>Transmitting and combined coils with flexibility to adapt to areas being scanned.</p> Signup and view all the answers

    What occurs to the magnetic moments of hydrogen nuclei when they align parallel to the main magnetic field (B0)?

    <p>They produce low energy potential.</p> Signup and view all the answers

    What is a major advantage of the Turbo inversion recovery sequence used in MRI?

    <p>It has a lengthy TI that facilitates fluid suppression.</p> Signup and view all the answers

    How is the precession frequency (w0) calculated according to the Larmor equation?

    <p>w0 = γ B0</p> Signup and view all the answers

    What happens to the precession frequency of hydrogen nuclei when the magnetic field strength is increased?

    <p>It increases linearly.</p> Signup and view all the answers

    In the context of MR-active nuclei, what does the gyromagnetic ratio (γ) represent?

    <p>The relationship between angular momentum and magnetic moment.</p> Signup and view all the answers

    At a magnetic field strength of 0.5 T, what is the precessional frequency of hydrogen nuclei?

    <p>21.29 MHz</p> Signup and view all the answers

    Which orientation of magnetic moments corresponds to high energy states in hydrogen nuclei?

    <p>Aligned anti-parallel to B0</p> Signup and view all the answers

    What is the characteristic of the net magnetic vector (NMV) when hydrogen nuclei align anti-parallel to B0?

    <p>It represents high energy.</p> Signup and view all the answers

    How do different MR-active nuclei influence precessional frequencies at various field strengths?

    <p>They have unique precessional frequencies that vary with the magnetic field's intensity.</p> Signup and view all the answers

    Which property is primarily responsible for the hydrogen nucleus being an effective MR-active nucleus?

    <p>It has a relatively large magnetic moment due to its single proton.</p> Signup and view all the answers

    What type of motion occurs within the nucleus of an atom that enhances its magnetic properties?

    <p>The nucleus spinning about its own axis.</p> Signup and view all the answers

    Faraday's law indicates the relationship between which two phenomena?

    <p>Moving charged particles and electric fields.</p> Signup and view all the answers

    Why is protium specifically chosen for MRI instead of other isotopes of hydrogen?

    <p>It provides the maximum magnetization due to its single proton.</p> Signup and view all the answers

    Which of the following elements is NOT considered MR-active based on their nuclei properties?

    <p>Bromine (Br)</p> Signup and view all the answers

    What aspect of the atomic structure directly influences the strength of the magnetic field generated by the hydrogen nucleus?

    <p>The alignment of the magnetic moments.</p> Signup and view all the answers

    What does the term 'net spin' refer to in the context of MR-active nuclei?

    <p>The collective spins of protons resulting in a magnetic moment.</p> Signup and view all the answers

    In MRI, why is Faraday's law significant for understanding the behavior of MR-active nuclei?

    <p>It outlines how moving charges create magnetic fields, integral to nuclear magnetic resonance.</p> Signup and view all the answers

    Study Notes

    Atomic Structure

    • All matter is made up of atoms that form molecules
    • Key elements in the human body include hydrogen, oxygen, carbon, and nitrogen
    • Atoms have a central nucleus with orbiting electrons
    • Nucleus contains protons (positive charge) and neutrons (no charge)
    • Electrons have a negative charge and orbit the nucleus
    • The nucleus is tiny but contains most of the atom's mass
    • The nucleus is composed of protons and neutrons (nucleons)
    • The nucleus occupies a tiny fraction of the atom's volume

    Motion of Atoms

    • Electrons spin on their own axis
    • Electrons orbit the nucleus
    • The nucleus spins on its own axis

    MR-active Nuclei

    • A nucleus with an uneven number of protons and neutrons has a net spin and is MR-active:
      • ¹H (hydrogen)
      • ¹³C (carbon)
      • ¹⁵N (nitrogen)
      • ¹⁷O (oxygen)
      • ¹⁹F (fluorine)
      • ²³Na (sodium)

    Hydrogen Nucleus

    • The isotope of hydrogen called protium is the most commonly used MR-active nucleus
    • It has a mass and atomic number of 1, and its nucleus consists of a single proton and no neutrons
    • Hydrogen is abundant in the human body and its single proton gives it a large magnetic moment
    • These characteristics mean the maximum amount of magnetization in the body is utilized

    Faraday's Law of Electromagnetic Induction

    • A magnetic field is created by a moving charged particle
    • The protium nucleus contains one positively charged proton that spins, making it a moving charged particle, which creates a magnetic field.
    • The nucleus acts as a small magnet with a north and south pole.
    • The north/south axis of each nucleus is represented by a magnetic moment
    • This magnetic moment can align with an external magnetic field (B0)

    Alignment

    • In the absence of an external magnetic field, the magnetic moments of hydrogen nuclei are randomly oriented
    • When placed in a strong static external magnetic field, the magnetic moments align with the field.
    • This alignment is called magnetization.
    • Nuclei aligned parallel to the field have a low energy (referred to as "spin up" nuclei)
    • Nuclei aligned anti-parallel to the field have a high energy (referred to as "spin down" nuclei)

    Net Magnetic Vector (NMV)

    • The NMV represents the overall magnetic field strength in a sample.
    • It is proportional to the external magnetic field strength (B0).

    Precession and Precessional (Larmor) Frequency

    • The magnetic moments of hydrogen nuclei precess around the B0 field.
    • Precession frequency (w0) is the speed at which magnetic moments precess around B0
    • The Larmor equation relates precession frequency, magnetic field strength, and gyromagnetic ratio: w0 = γB0
      • w0: precession frequency
      • B0: magnetic field strength
      • γ: gyromagnetic ratio (constant)
    • Precession frequency is proportional to the strength of the magnetic field.
    • For hydrogen:
      • At 1.5 T, the precessional frequency is 63.87 MHz.
      • At 1.0 T, the precessional frequency is 42.57 MHz.
      • At 0.5 T, the precessional frequency is 21.29 MHz.

    Atomic Structure

    • All matter is composed of atoms.
    • Atoms combine to form molecules.
    • Key elements in the human body are hydrogen, oxygen, carbon, and nitrogen.
    • Atoms have a central nucleus and orbiting electrons.
    • The nucleus contains protons (positive charge) and neutrons (no charge).
    • Electrons (negative charge) orbit the nucleus.

    Mass and Size of Nucleus

    • The nucleus is tiny but contains most of the atom's mass.
    • It is composed of protons and neutrons (collectively known as nucleons).
    • The nucleus occupies a minute fraction of an atom's volume.

    Motion in the Atom

    • Three types of motion occur within an atom:
      • Electrons spinning on their own axis
      • Electrons orbiting the nucleus
      • The nucleus itself spinning about its own axis

    MR-active Nuclei

    • MR-active nuclei have a net spin, meaning their protons and neutrons are not equal, resulting in a magnetic moment.
    • Common MR-active nuclei include:
      • 1H (hydrogen)
      • 13C (carbon)
      • 15N (nitrogen)
      • 17O (oxygen)
      • 19F (fluorine)
      • 23Na (sodium)

    The Hydrogen Nucleus

    • The isotope of hydrogen called protium is the most commonly used MR-active nucleus in MRI.
    • It has a mass and atomic number of 1, meaning its nucleus consists of a single proton and no neutrons.
    • Hydrogen is abundant in the human body and its single proton gives it a relatively large magnetic moment, maximizing the available magnetization for MRI.

    Faraday’s Law of Electromagnetic Induction

    • Faraday's law states that a magnetic field is created by a charged moving particle.
    • The protium nucleus's spinning proton, being charged, induces a magnetic field around it, acting as a small magnet.
    • Each hydrogen nucleus has a north and a south pole of equal strength, represented by its magnetic moment.

    Alignment

    • In the absence of an external magnetic field, hydrogen nuclei's magnetic moments are randomly oriented, producing no overall magnetic effect.
    • When placed in a strong static external magnetic field (B0), the magnetic moments of hydrogen nuclei align with it, resulting in:
      • Low energy: Nuclei aligned parallel to B0, referred to as "spine up" nuclei.
      • High energy: Nuclei aligned anti-parallel to B0, referred to as "spine down" nuclei.

    Net Magnetic Vector (NMV)

    • The alignment of hydrogen nuclei in an external magnetic field creates a net magnetic vector (NMV), also known as net magnetization (M0).
    • The strength of the NMV is directly proportional to the strength of the external magnetic field (B0).

    Precession and Precessional (Larmor) Frequency

    • When placed in an external magnetic field, hydrogen nuclei's magnetic moments precess around the field's axis.
    • The speed of this precession is called the precessional frequency (ω0) and is determined by the Larmor equation: ω0 = γB0
      • ω0: Precessional frequency
      • B0: Magnetic field strength
      • γ: Gyromagnetic ratio (a constant for a given nucleus)

    Magnetic Characteristics of Common Elements

    • The gyromagnetic ratio (γ) is a constant for a specific nucleus.
    • At different field strengths, the precessional frequencies of MR-active nuclei vary.
    • For hydrogen, at:
      • 1.5 T: 63.87 MHz
      • 1.0 T: 42.57 MHz
      • 0.5 T: 21.29 MHz

    Atomic Structure

    • All matter is composed of atoms.
    • Atoms combine to form molecules.
    • Key elements in the human body: hydrogen, oxygen, carbon, nitrogen.
    • Atoms have a central nucleus and orbiting electrons.
    • Nucleus contains protons (positive charge) and neutrons (no charge).
    • Electrons (negative charge) orbit the nucleus.

    Mass and Size of Nucleus

    • Nucleus is tiny but contains most of the atom's mass.
    • Composed of protons and neutrons (nucleons).
    • Nucleus occupies a minute fraction of an atom's volume.

    Motion in the Atom

    • Three types of motion are present within the atom:
      • Electrons spinning on their own axis
      • Electrons orbiting the nucleus
      • The nucleus itself spinning about its own axis.

    MR-active nuclei

    • Protons and Neutrons:
      • P=N Has no spine =0
      • P≠N Has net spine≠0
    • MR-active nuclei:
      • 1H (hydrogen)
      • 13C (carbon)
      • 15N (nitrogen)
      • 17O (oxygen)
      • 19F (fluorine)
      • 23Na (sodium).

    The Hydrogen Nucleus

    • The isotope of hydrogen called protium is the most commonly used MR-active nucleus in MRI.
    • It has a mass and atomic number of 1, so the nucleus consists of a single proton and has no neutrons.
    • It is used because hydrogen is very abundant in the human body and because the solitary proton gives it a relatively large magnetic moment.
    • These characteristics mean that the maximum amount of available magnetization in the body is utilized.

    Faraday's Law of Electromagnetic Induction

    • Faraday's law of electromagnetic induction states that a magnetic field is created by a charged moving particle (that creates an electric field).
    • The protium nucleus contains one positively charged proton that spins and moves.
    • Therefore, the nucleus has a magnetic field induced around it and acts as a small magnet.
    • The magnet of each hydrogen nucleus has a north and a south pole of equal strength.
    • The north/south axis of each nucleus is represented by a magnetic moment and is used in classical theory.
    • Motion + electricity = magnet

    Alignment

    • In the absence of an applied magnetic field, the magnetic moments of hydrogen nuclei are randomly orientated and produce no overall magnetic effect.
    • However, when placed in a strong static external magnetic field, the magnetic moments of hydrogen nuclei orientate with this magnetic field.
    • This is called alignment.

    Net Magnetic Vector (NMV)

    • Align parallel to the main magnetic field (B0) (Net magnetic vector, NMV)
      • Low energy
      • Spine up nuclei
    • Align Anti-parallel to the main magnetic field (B0)
      • High energy
      • Spine down nuclei

    Precession and Precessional (Larmor) Frequency

    • Precession frequency: The speed at which magnetic moments preces around B0 is called Precession frequency (w0).
    • Larmor equation:
      • W0 = y B0
      • Where:
        • W0: is the Precession frequency
        • B0: is the magnetic field strength of the magnet
        • Y: is the gyromagnetic ratio

    Glossary

    • Acquisition time = Period of time required to collect the image data.
    • AP Anteroposterior = from the front to the back of the body.
    • Axial= Orthogonal to the long axis of the body.
    • CISS= Constructive interference steady state: a sequence which supposedly minimizes the interference-induced artifacts of a true FISP sequence; the CISS sequence is heavily T2-weighted and currently is used primarily as a high-resolution 3-D sequence for the inner ear
    • Coil =Transmission or reception unit for the signals transmitted/ received by the magnet. There are transmission, reception, and combined transmission/reception coils, and they come as body and surface coils, the latter being available as rigid and flexible (wraparound) coils.
    • CSF = Cerebrospinal fluid.
    • Dark fluid = Turbo inversion recovery sequence: a technique with a long TI (approx. 2200ms for 1.0 and 1.5 T) used for fluid suppression, e.g., for suppressing the CSF in brain and spinal studies with T2 weighting (and long TE).
    • DESS = Dual echo steady state: gradient echo sequence where both axial and transverse magnetization adds to the signal, e.g.the FISP sequence and its temporally reversed form PSIF. In DESS the two sequences (FISP as a ratio of T1 to T2, and PSIF as mostly T2-weighted sequence) are added.
    • 3-D measurement = Volume measurement: imaging technique where each pulse excites not just a single slice but the entire volume of interest.
    • Dual echo = Dual measurement: sequences characterized by two readout times (TE) for one (comparatively long) TR. Normally dual echo combines proton-densityweighted (short TE) and T2-weighted (long TE) measurements.
    • ECG triggering (EGG gating)= Triggered by the signals of the heart: data acquisition takes place only during particular phases of the cardiac cycle (e.g. during systole or diastole); the patient has to be attached to a set of ECG leads.

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