Chapter 20: MAGNETIC RESONANCE IMAGING (MRI)

MRI of the joints or limbs demonstrates all of the following except: A. Ligaments B. Tendons C. Muscle D. Cortical bone

D. Cortical bone

MRI of the spine is not best for evaluating which of the following? A. Bone marrow changes B. Cord abnormalities C. Disk herniation D. Degree of scoliosis present in spine

D. Degree of scoliosis present in spine

TE can be defined simply as: A. Echo phase B. Time net C. Temporary echo D. Echo time

D. Echo time

The contrast agent commonly used for MR examinations is: A. Iodine 131 B. Lanthanum oxybromide C. Gadolinium oxysulfide D. Gadolinium-diethylene triamine pentaacetic acid

D. Gadolinium-diethylene triamine pentaacetic acid

True/False: Tissues filled with air do not produce a T1 or T2 signal and therefore appear as bright.

False (appear black)

True/False: High-field strength MRI magnets can produce up to 7 tesla

False -3 tesla

Artifacts

False features on an image caused by patient instability or equipment deficiencies

T1-weighted images of the abdomen are helpful in identifying tumors containing______________________and ______________.

Fat and hemorrhage

The most important contraindication to MRI of the brain involves torquing of_____________.

Ferromagnetic intracranial aneurysm clips

Torque

Force that causes or tends to cause a body to rotate

Filling factor

Measurement of the geometric relationship between the RF coil and the body

In addition to tumor detection, what other pathology may indicate the use of contrast media during an MRI scan?

Metastasis, infection, inflammatory processes, subacute cerebral infarcts, and neoplasms in the brain

Signal averaging

Method of improving SNR by averaging several FIDs or spin echoes

The MRI image represents differences in the patient's tissues in the number of____________________ and the rate at which they recover from radiofrequency stimulation.

Nuclei

The signal that is received by the antenna or the receiving coil comes from which part of the atoms in the body tissues?

Nucleus or proton

Pulse sequences using a combination of short TR and short TE is ______________

T1 relaxation

Relaxation of the nuclei as soon as the radiofrequency pulse is turned off can be divided into two categories: ________________and _______________.

T1 relaxation and T2 relaxation

identify the T1- and T2-weighted appearances for: Fat

T1: bright , T2: dark

identify the T1- and T2-weighted appearances for: CSF and water

T1: dark , T2: bright

identify the T1- and T2-weighted appearances for: Vessels

T1: dark , T2: dark

identify the T1- and T2-weighted appearances for: Muscle

T1: dark grey , T2: dark grey

identify the T1- and T2-weighted appearances for: gray brain matter

T1: dark grey , T2: light grey

identify the T1- and T2-weighted appearances for: Cortical bone

T1: dark, T2: dark

identify the T1- and T2-weighted appearances for: air

T1: dark, T2: dark

identify the T1- and T2-weighted appearances for: Red bone marrow

T1: light grey , T2: dark grey

identify the T1- and T2-weighted appearances for: White brain matter

T1: light grey , T2: dark grey

Pulse sequences using a combination of long TR and long TE is __________

T2 relaxation

The ________________rate is a measurement of normal kidney function

eGFR (estimated glomerular filtration rate)

The average amount of contrast media administered during an MRI examination is __________mL/kg; the injection rate should not exceed ___________mL/min.

0.2; 10

list of six structures or tissue types best demonstrated by MRI of the brain

1. Gray matter 2.Basal ganglia 3.Brainstem 4.White matter 5.Nerve tissue 6.Ventricles

List the ten absolute contraindications to patient MRI scanning

1. Internal pacemakers (unless certified as MRI safe)/ defibrillators 2. Ferromagnetic aneurysm clips 3. Metallic fragments in the eye 4. Cochlear implants 5. Starr-Edwards pre-6000 model prosthetic heart valve 6. Internal drug infusion pumps 7. Internal pain pumps (unless certified as MRI safe) 8. Neurostimulators 9. Bone growth stimulators 10. Ferromagnetic gastrointestinal surgical clips

What are three primary factors that determine the signal strength?

1. Spin density 2. T1 relaxation rate 3. T2 relaxation rate

List three types of histories that should be obtained from patients before an MRI exam.

1. Surgical history 2. Occupational history 3. Accidental history

T1-weighted MRI of the spine is effective in evaluating:

1.Cysts 2.Syrinxes 3.Lipomas

list of six possible pathologies best demonstrated by MRI of the brain

1.Hemorrhagic disorders 2.CVA (Cerebrovascular Accident) 3. White matter disease (multiple sclerosis or demyelinating disease) 4.Ischemic disorders 5. Neoplasm 6. Infectious diseases (such as AIDS and herpes)

list of the five MRI safety concerns:

1.Local heating of tissues and metallic objects 2.Gradient magnetic fields (time-varying magnetic fields). 3.Potential hazards of projectiles 4.Electromechanical implants 5.Torquing of ferromagnetic objects

List two major advantages of MRI over CT imaging of the spine:

1.MRI does not require the use of intrathecal ("within a sheath") contrast media. 2.MRI covers a large area of the spine in a single sagittal view.

List the four conditions or diseases best demonstrated with MRI of the joints:

1.Meniscal abnormalities 2.Avascular necrosis of the hip and other bony regions 3.Soft tissue masses 4.Bone marrow abnormalities

Patients with internal drug infusion pumps and cochlear implants are not allowed inside the___________-gauss line.

10

As a general rule, O2 tanks, IV pumps, and wheelchairs are not allowed inside the_________________-gauss line.

5

Pacemakers are not allowed inside the ______________--gauss line.

5

Meningioma

A hard, slow-growing vascular tumor

Chordoma

A malignant tumor arising from the embryonic remains of the notochord

Schwannoma

A new growth of the white substance of the nerve sheath

Acoustic neuroma

A tumor growing from nerve cells affecting the sense of hearing

Common strengths of magnets used in MRI range from: A. 1 to 3 tesla B. 5 to 7 tesla C. 12 to 15 tesla D. 15 to 20 tesla

A. 1 to 3 tesla

Pacemakers are not allowed inside the: A. 5-gauss line B. 2.5-gauss line C. 1.0-gauss line D. 0.5-gauss line

A. 5-gauss line

precessing nucleus produces_______________ in a nearby loop of wire. A. An alternating current B. A dipole C. A direct current D. Magnetic regression

A. An alternating current

In T1 relaxation, the spins of the exposed nuclei: A. Are relaxing back to a vertical orientation B. Stay in a horizontal position C. Are reduced in density D. Become out of phase with one another

A. Are relaxing back to a vertical orientation

On T1-weighted images, CSF appear: A. Dark B. Bright C. Same as white matter D. Same as gray matter

A. Dark

The signal strength and thus the brightness of points in the image are primarily determined by: A. Differences in T1 and T2 relaxation rates of tissues B. Differences in spin density of tissues C. The longitudinal component of nuclei D. Exposure of the nuclei to the static magnetic field

A. Differences in T1 and T2 relaxation rates of tissues

What type of objects are a concern when placed within the fringe field? A. Ferromagnetic B. Titanium C. Molded plastic D. Those containing water or other fluids

A. Ferromagnetic

The most common nuclei in the body that are used to receive and reemit radio waves are: A. Hydrogen B. Carbon C. Oxygen D. Phosphorus

A. Hydrogen

The largest drawback to MRI of the abdomen is: A. Motion artifacts B. Metallic implants C. Coil selection D. Sequence times

A. Motion artifacts

Resonance occurs when radio waves are: A. Of the same frequency as the precessing nuclei B. At the same rate as T1 relaxation C. At the same rate as T2 relaxation D. Received by an antenna

A. Of the same frequency as the precessing nuclei

Contrast agents are generally used in conjunction with: A. T1-weighted pulse sequences B. T2-weighted pulse sequences C. Spin density-weighted pulse sequences D. All of the above

A. T1-weighted pulse sequences

Local heating of tissues (referred to as SAR, or specific absorption ratio) is measured in: A. W/kg B. Joules/kg C. RF frequency D. W/cm2

A. W/kg

MRI of the brain allows visualization of: A. White matter disease B. Acute cerebral bleeds C. Small calcifications D. Skull anomalies

A. White matter disease

Contrast resolution

Ability of an imaging process to distinguish adjacent soft tissues from one another

Flip angle structures

Amount of rotation of the net magnetization vector produced by an RF pulse

Precession occurs as a result of _________________acting on a spinning nuclei.

An outside force (external magnetic field)

Cryogen

Atmospheric gases such as nitrogen and helium used for cooling

IV pumps, wheelchairs, and O2 tanks are not allowed inside the: A. 150-gauss line B. 50-gauss line C. 5-gauss line D. 1-gauss line

B. 50-gauss line

Which of the following properties results in a nucleus behaving like a small magnet? A. An even number of neutrons and protons B. An odd number of neutrons or protons C. An even number of electrons D. The presence of a magnet

B. An odd number of neutrons or protons

On T2-weighted images, CSF appear: A. Dark B. Bright C. Same as white matter D. Same as gray matter

B. Bright

Which of the following devices/equipment is required during a cardiac-gated MRI procedure? A. CT B. ECG C. PET D. Pulse oximeter

B. ECG

stray magnetic field that exists outside the MRI gantry is the definition for: A. RF field B. Fringe field C. Magnetic field D. Field of influence

B. Fringe field

TR and TE have a profound influence on: A. Image noise deletion B. Image contrast C. Signal averaging D. Image density

B. Image contrast

The MRI image represents differences in the number of: A. X-rays attenuated B. Nuclei and the rate of their recovery C. Frequencies of nuclei D. Radio waves

B. Nuclei and the rate of their recovery

Proton density refers to the of hydrogen nuclei. A. Quality B. Quantity C. Phase D. Wavelength

B. Quantity

Precession of magnetic nuclei can be altered by the application of: A. X-rays B. Radio frequencies C. Microwaves D. Visible light

B. Radio frequencies

The MRI process excites the nuclei in the body with: A. X-rays B. Radio frequencies waves C. Sound waves D. Visible light

B. Radio frequencies waves

Emitted signals from the exposed nuclei are _____________and sent to the computer. A. Evaluated B. Received by an RF coil (antenna) C. In resonance D. Precessing

B. Received by an RF coil (antenna)

TR can be defined simply as: A. Time reversal B. Repetition time C. Timing range D. Time of resonance

B. Repetition time

Which of the following types of MRI magnets requires the use of cryogens? A. Permanent B. Superconducting magnets C. Resistive D. Open magnets

B. Superconducting magnets

Neural activity is measured by __________________during a functional MRI procedure. A. Decreased RF signal B. Increased RF signal C. Blood oxygen level-dependent (BOLD) signal D. Water shift signal

C. Blood oxygen level-dependent (BOLD) signal

The ____________among T1, T2, and proton density signals of tissues produce(s) contrast in the MRI image. A. Similarities B. Phase C. Differences D. Frequency

C. Differences

The most important MRI safety contraindication in regard to the torquing of metallic objects is: A. Intra-abdominal surgical staples B. Stainless steel femoral rods C. Ferromagnetic intracranial aneurysm clips D. Titanium hip prosthesis

C. Ferromagnetic intracranial aneurysm clips

Precession of the magnetic nuclei occurs because of: A. Oscillation in the presence of other atoms B. Regression under the influence of a magnet C. The influence of a static magnetic field D. Ionization-exposed atoms

C. The influence of a static magnetic field

Which of the following is not a similarity between MRI and CT? A. The outward appearance of the unit B. The use of a computer to analyze information C. The use of ionizing radiation D. Images viewed as a slice of tissue

C. The use of ionizing radiation

In T2 relaxation, the spins of the exposed nuclei: A. Are vertical in orientation B. Move to the north C. Are reduced in density D. Become out of phase with one another

D. Become out of phase with one another

MRI has excellent ____________________, which allows visualization of soft tissue structures.

Contrast resolution

One tesla equals: A. 10,000 times the earth's magnetic field B. 0.00005 gauss C. 10 gauss D. 10,000 gauss

D. 10,000 gauss

The nuclei that receive and reemit radio waves are under the influence of: A. Gravitational force B. The sun and the planets C. X-ray energy D. A static magnetic field

D. A static magnetic field

Functional MRI is performed to study: A. Anatomy of the brain B. Specific functions of the brain C. Processes such as language, vision, movement, hearing, and memory D. All of the above

D. All of the above

Which of the following technical factors may be used in spine imaging? A. T1-weighted sequence B. T2-weighted sequence C. Gradient echo D. All of the above

D. All of the above

True/False: fMRI does not provide a measure of human cognition (learning).

False

Which of these pathologic conditions would indicate the use of contrast media during an MRI procedure? A. Cerebral bleed B. C-spine fracture C. HNP D. Inflammatory conditions of spine

D. Inflammatory conditions of spine

Primary safety concerns for the technologist, patient, and medical personnel are a result of: A. Fringe field strengths less than 1 gauss B. Gravitational pull on metallic objects C. Magnetic fields and heat production D. Interaction of magnetic fields with ferrometallic objects and tissues

D. Interaction of magnetic fields with ferrometallic objects and tissues

The angle of precession of the nuclei is altered because the: A. Nuclei must be vertical B. Magnetic force dominates C. Electrostatic properties of the nuclei dominate D. MR signal is strongest when nuclei are in a horizontal or transverse plane

D. MR signal is strongest when nuclei are in a horizontal or transverse plane

MRI of the brain includes the use of a standard head coil and: A. Prone position B. Cardiac gating C. Sedation D. T1-weighted and T2-weighted pulse sequences

D. T1-weighted and T2-weighted pulse sequences

True/False: Cardiac gating during an MRI procedure is a process in which heart wall motion is studied

False

True/False: Contrast media used in MRI carry a higher risk for allergic reaction as compared with iodinated contrast agents.

False

True/False: MR should be avoided in the first 6 months of pregnancy unless diagnosis is crucial for conditions

False

True/False: T1-weighted images demonstrate free air within the abdominal cavity

False

The danger of projectiles becomes ______________(greater or less) as ferromagnetic objects are moved toward the scanner because the field strength is _______________(directly or inversely) proportional to the cube of the distance from the bore of the magnet.

Greater; directly

Which nucleus is most suitable for MRI? and Why?

Hydrogen (single-proton nucleus) The large amount of hydrogen present in any organism (Hydrogen atoms are present in each water molecule, and the body is roughly 85% water.)

Turbulence

In flowing fluid, velocity component that fluctuates randomly

How does an increase in the length of application time of the radio wave affect the angle of precession of the exposed nuclei?

Increase in time increases the angle of precession

Define precession by comparing it to another, more well-known phenomenon.

It is similar to the wobble of a slowly spinning top

T1 relaxation is known as _____________________(transverse or longitudinal), or spin-lattice, relaxation

Longitudinal

Physiologic gating

MRI technique to minimize involuntary motion artifacts

MRI uses _______________and _______________to obtain a mathematically reconstructed image.

Magnetic fields and radio waves

Which component of the nucleus is affected by radio waves and static magnetic fields?

Proton

The nucleus emits______________ waves because it is a tiny magnet that is also ___________________.

Radio; precessing or rotating

The angle of precession of protons can be altered by the introduction of____________________.

Radiofrequency pulse

Spin echo

Reappearance of MR signal after the FID has disappeared

TR

Repetition time

Timing of the radio wave frequency to the rate of the precessing nuclei is an example of the concept of________________.

Resonance

Tesla (T)

SI unit of magnetic field intensity

Precession

Slow gyration of an axis of a spinning body caused by an application of torque

Describe the main purpose of the gradient magnetic fields (the magnetic field strengths through only specific regions or slices of body tissue)

So that the returning signal can be located (because only the precessing nuclei within these regions or slice transmit signals)

Which term is used to describe the amount of tissue heating delivered during an MRI procedure?

Specific absorption ratio (SAR)

The quantity of hydrogen nuclei per given volume of tissue is referred to as the_______________ , which is a______________ (major or minor) contributor to the appearance of the MR image

Spin (or proton) density; minor

T1

Spin lattice or longitudinal relaxation time

T2

Spin-spin or transverse relaxation time

Fringe field

Stray magnetic field that exists outside the imager

T2 relaxation is known as ____________________(transverse or longitudinal), or spin-spin, relaxation.

Transverse

True/False: A titanium hip prosthesis is an example of an MRI safe device

True

True/False: As magnet or field strength increases, quality and resolution of the MRI image increases.

True

True/False: Before administering gadolinium-DTPA (Gd-DTPA), creatinine levels should be checked

True

True/False: CT is considered a better clinical option in detecting acute bleeding in the brain.

True

True/False: CT is superior to MRI for evaluation of a vertebral arch fracture.

True

True/False: During the cardiac-gated MRI procedure, signal collection occurs at the same point during the cardiac cycle.

True

True/False: Flowing blood is not visualized with a conventional spin-echo pulse sequence

True

True/False: Functional MRI (fMRI) provides both an anatomic and functional assessment of the brain

True

True/False: Functional MRI of the brain exceeds the spatial resolution seen with PET and SPECT images

True

True/False: MR should be avoided in the first 3 months of pregnancy unless diagnosis is crucial for conditions such as acute appendicitis or other emergencies as determined by a physician.

True

True/False: fMRI does not require the injection of radiopharmaceuticals

True

True/False: fMRI studies neurological processes such as language, vision, movement, hearing, and memory.

True

What unit of measurement is used to calculate local heating of tissues?

W/kg (watts per kilogram)

T2-weighted images of the abdomen are useful to demonstrate changes in______________________.

Water content in tissues (associated with tumors and other abnormalities)

In an emergency situation, the patient is removed from the scan room because of the danger of _______________________.

ferromagnetic objects used in emergency situations becoming projectiles

The rate of precession of a proton in a magnetic field ______________________(increases or decreases) as the strength of the magnetic field increases

increases

Diagnosis of diseases such as those involving the CNS can be made with MRI by comparing the signals produced in ________________tissues versus _____________tissues.

normal tissues versus abnormal tissues.

Pulse sequences using a combination of long TR and short TE is _______________

proton density

What is the whole-body averaged SAR permitted for a 15-minute MRI procedure with a 1.5 Tesla system?

should not exceed 3.5 W/kg for 15 minutes of scanning