unit 3 - modules
The range of CT numbers or Hounsfield Units varies from 100 to 300. -100 to +300. -1000 to +3000. 1000 to +3000.
-1000 to +3000.
In order for a CT x-ray photon to be measured, it must, 1. enter the detector 2. be absorbed by the detector material 3. transmit through the detector to be back-projected 4. have sufficient energy to undergo a Compton interaction 5. be converted to light and then electrical energy as a signal 1, 3, 4, and 5 1, 2, and 5 1, 2, and 4 1, 4, and 5
1, 2, and 5
Current FDA standards limit the specific absorption rate (SAR) to 4 watts/kg of body weight. the patient's BMI. the ratio of their height to weight. 10 watts/kg for the head.
4 watts/kg of body weight.
Image noise in CT scanning depends on _______________________. pixel size detector efficiency slice thickness All of the above
All of the above
External, static magnetic field GBCA cryogen Bo active shimming
Bo
The most widely used technique for MR image reconstruction is back projection. interpolation. Fast Fourier transformation (FFT). Larmor equation precession (LEP).
Fast Fourier transformation (FFT).
The primary mathematical method used in the creation of computerized medical images is the ____ transformation. interpolation Hounsfield algorithm Fourier
Fourier
A series of tissue density values that evolved for CT measurements is called ____ units. Hounsfield H & D attenuation iterative
Hounsfield
Each pixel of information in the CT image contains numerical information in ___________ units. voxel reconstruction Hounsfield pixel
Hounsfield
The basic principle of MR physics involves an established relationship between an external magnetic field and the gyromagnetic ratio of an atom. This is expressed as the power conversion ratio Larmor equation. Hounsfield coefficient. H & D curve.
Larmor equation.
Same as precessional frequency T2 relaxation Larmor frequency gyromagnetic ratio NSF
Larmor frequency
Begins with a 90° RF pulse and is followed by a 180° RF pulse SE pulse sequence precession T2 relaxation Fast Fourier transformation (FFT).
SE pulse sequence
What is the SI unit of magnetic field strength? Ampere Tesla Dipole Ohm
Tesla
When most of the dipoles in an object are aligned, they create _________________. a magnetic domain paramagnetic material magnetic resonance a magnet
a magnet
In the event a CT patient needs emotional support for a procedure, during the acquisition patient restraints should be used. a patient family member should be allowed to attend to the patient. the department nurse should be asked to attend to the patient. the CT supervisor should stand by the patient.
a patient family member should be allowed to attend to the patient.
The ____ is how well the detectors convert incoming photons. capture efficiency absorption efficiency conversion efficiency response time
absorption efficiency
CT scan pitch uses all of the following technical parameters EXCEPT slice thickness. 360-degree gantry rotation. acquisition mAs . table increment.
acquisition mAs .
Uses RF coils to create a homogeneous field GBCA cryogen Bo active shimming
active shimming
Computed tomography sections are available as coronal. transverse. sagittal. all of the above
all of the above
MRI has been achieved with ____ magnets. resistive permanent superconductive all of the above
all of the above
MSCT scanners have evolved greatly over the last few years, particularly with regard to slice combinations, scanning speed, and clinical utility. As these scanners gather more slices of data per rotation, a major technological challenge is the amount of data handled by the computer. the number of images to be analyzed by the clinician. developing technologies to minimize dose. all of the above
all of the above
The CT console provides the radiographer access to the software program. data acquisition. data display. all of the above
all of the above
The CT radiation beam is collimated at the tube exit. at the detector entrance. pre-patient and post-patient. all of the above
all of the above
The CT table is made of carbon graphite. rated for maximum weight. motor-driven. all of the above
all of the above
The most common variable in operating an MRI unit is the ____ used to enhance image quality. TI TE TR all of the above
all of the above
The resolution of the CT image depends on the pixel. voxel. matrix size. all of the above
all of the above
The smaller the scan field size, the better the resolution. faster the scan time. less the risk of motion. all of the above
all of the above
Higher field strength MRI magnets permit shorter scan times. better resolution. stronger signal strength. all of the above.
all of the above.
Patient precautions with MR scanning include claustrophobia. not touching the inside of the gantry during scanning. ferromagnetic implants or prosthetic devices. all of the above.
all of the above.
The strength of an MR signal is directly proportional to the strength of the magnetic field directly proportional to the strength of BO. directly related to the tesla of the magnet. all of the above.
all of the above.
The calculation of CT numbers is based upon the calculation of half-value layers. half-lives. attenuation coefficients. pitch.
attenuation coefficients.
A ____ artifact is caused by attenuation of the beam as it passes through the patient. beam-hardening ring star streak
beam-hardening
As noise increases in a CT image, low contrast resolution increases. dose to the patient increases. low contrast resolution decreases. both a and c
both a and c
To prevent extraneous RF signals from degrading MR image quality, MR scan suites are enclosed in a copper cage. steel cage. Faraday cage. both a and c.
both a and c.
Increasing the number of signal averages (NSA) will decrease scan times increase the sampling of noise and not MR signal increase scan times both b and c
both b and c
In MRI, the primary visual factor is often called linearity. geometric shape. resolution. brightness.
brightness
The RF signal strength determines brightness. field strength. section thickness. spatial resolution.
brightness
The ____ is how well the detectors receive photons from the patient. capture efficiency absorption efficiency conversion efficiency response time
capture efficiency
From a patient safety viewpoint, it is important that cardiac monitoring wire leads not be looped or coiled on the patient. patients are provided with headphones to muffle the noise created by T1 relaxation times. renal function is assessed after scanning to measure kidney output. all of the above.
cardiac monitoring wire leads not be looped or coiled on the patient.
The actual response of proton spin to an RF pulse is to change the magnetic moment in a recovery circular motion. change the magnetic moment in a precessing corkscrew motion. remain stationary. change the magnetic moment in a precessing circular motion.
change the magnetic moment in a precessing corkscrew motion.
With MSCT scanners, resolution is primarily determined by prepatient collimation. dose. collimation at the detector. gantry rotation speed.
collimation at the detector.
CT imaging has excellent ______________ because of the narrow beam collimation. spatial frequency noise reduction contrast resolution spatial resolution
contrast resolution
The ____ is determined by how well the detector converts the absorbed photon information to a digital signal for the computer. capture efficiency absorption efficiency conversion efficiency response time
conversion efficiency
The process of modifying pixel values by a mathematical formula is called convolution. deconvolution. calculus. interpolation.
convolution.
The time between a 90-degree pulse and the echo during a spin-echo pulse sequence is spin density (ρ). repetition time (TR). echo time (TE). inversion time (TI).
echo time (TE).
The rotation of electrons on their axis is the property called ____________. magnetic force electron spin unified field theory magnetic induction
electron spin
The most recent generation of CT scanners use a ____ motion. translate-rotate helical linear elliptical
elliptical
When gradient coils are referred to, the long axis coil is referred to as the ____ gradient. selection phase encoding frequency encoding none of the above
frequency encoding
Contrast-enhanced MR images use ________ as the contrast material of choice. iodine barium gadolinium hydrogen
gadolinium
The ______________ determines the plane of acquisition Tesla resistive magnet gradient coils super conductive magnet
gradient coils
The characteristic MR noise that is uncomfortable for patients and staff is due the ________ turning on and off at a high frequency. external magnet external coils gradient coils RF coil
gradient coils
Unique value for each element, measured in MHz/T T2 relaxation Larmor frequency gyromagnetic ratio NSF
gyromagnetic ratio
First-generation CT scanners scanned the ____ only. head thorax abdomen pelvis
head
Many CT x-ray tubes have the capacity for millions of _________ with each exam. heat units rotations volts Hertz
heat units
CT scanners operate on ________________ voltage generation. single-phase three-phase high-frequency 12-pulse
high-frequency
A high variation in pixel values in a homogeneous phantom is a measure of ________. spatial resolution image noise contrast resolution motion artifact
image noise
Filtered back projection in CT refers to ___________________. spatial resolution prepatient collimation beam filtration image reconstruction
image reconstruction
To improve MR image quality of fast moving involuntary abdominal viscera such as small bowel increasing the NSA's can be effective. patients should be heavily sedated. patient should be told to suspend respiration. reducing magnetic field strengths is recommended.
increasing the NSA's can be effective.
The time between a 180-degree pulse and a 90-degree inversion pulse in an inversion recovery pulse system is spin density (ρ). repetition time (TR). echo time (TE). inversion time (TI).
inversion time (TI).
The CTDI dose measurement is slice-based. takes into account the total amount of irradiated tissue. represents the average total dose to the patient during the examination. measures entrance skin exposure (ESE).
is slice-based.
The source of magnetic fields within the body, that create an MR signal is the spinning nucleus of an atom are the neutrons. are the stationary electrons. all of the above.
is the spinning nucleus of an atom
In an MR gantry, the patient lies at the lowest gantry level. isocenter. geometric center. the center of the external coils.
isocenter.
The CT radiographer usually varies the ____ to control the primary beam. mA time kVp distance
mA
The magnetic field around an atom caused by the rotation of electrons is the property called ____________. magnetic force magnetic dipole magnetic domain magnetic induction
magnetic dipole
Each CT projection records variations in _________________________. density and contrast motion and noise spatial resolution and contrast resolution mass density and effective atomic number
mass density and effective atomic number
The pixel size is reduced when the _______ size is increased and the _____________ size is fixed. field of view, matrix matrix, field of view Hounsfield unit, field of view field of view, Hounsfield unit
matrix, field of view
The gyromagnetic ratio is the ratio of the magnetic moment to the moment of magnetic force force to the moment of inertia. moment to the moment of inertia. dipole to its center.
moment to the moment of inertia.
A patient safety concern with the use of gadolinium contrast agents in MR is oxygen toxicity. hydrogen saturation. suppressed T1 times. nephrogenic systemic fibrosis
nephrogenic systemic fibrosis
The first generation of computed tomography used ______ detector(s). one two three four
one
When gradient coils are referred to, the short axis coil is referred to as the ____ gradient. selection phase encoding frequency encoding none of the above
phase encoding
The degree of spatial resolution in any CT imaging system is limited to the size of the ___________. voxel FOV matrix pixel
pixel
A rotation of the axis of rotation SE pulse sequence precession T2 relaxation Fast Fourier transformation (FFT).
precession
A rotation of the axis of rotation SE pulse sequence precession T2 relaxation You Answered Fast Fourier transformation (FFT).
precession
The Larmor frequency is the ____ frequency. quantum precessional linear gradient
precessional
The patient dose in CT is determined by the ________________ collimator. predetector prepatient postpatient Both A and B
prepatient
The MHz frequency magnetic field for MRI is produced by a/an radio transmitter coil. optical cable. digital converter. high-frequency generator.
radio transmitter coil.
Contemporary CT scanners use solid state detectors. These detectors utilize sodium iodide crystals. rare earth ceramic scintillators. xenon gas. freon gas.
rare earth ceramic scintillators.
To achieve coronal or sagittal sections, the gantry is repositioned. the patient is repositioned. reconfiguration software is implemented. none of the above
reconfiguration software is implemented.
The time from the end of CT imaging to image appearance is called the ______ time. reconstruction translation projection Hounsfield
reconstruction
The time interval between pulse sequences is spin density (ρ). repetition time (TR). echo time (TE). inversion time (TI).
repetition time (TR).
A ____ artifact is caused by detector error. beam-hardening ring star streak
ring
The localization image produced by the CT scanner is technically called a/an volume rendered image. scout film. scanogram. FOV image.
scanogram.
The primary variable in the data collection procedure during MRI is the pulsing of the static magnetic field. stationary magnet. sequence of RF pulses. initial scanogram.
sequence of RF pulses.
In order to create a more homogenous magnetic field in MR, ______ is required. a radio frequency a k-space coil an autotransformer shimming
shimming
The concentration of scintillation detectors affects the ___________ of the CT image. spatial resolution contrast resolution overall density motion artifact
spatial resolution
The size of the tissue voxel determines brightness. field strength. section thickness. spatial resolution.
spatial resolution.
A popular MR technique for the visualization of fat, specifically in suspected pathologies, requires that patients avoid a fatty meal. special MR sequences can be tuned to receive signal from the resonant frequencies of hydrogen protons in fat or water. fat saturation techniques should be avoided. patients ingest a fatty meal during the MR scan, to observe the movement of lipid hydrogen protons as they precess.
special MR sequences can be tuned to receive signal from the resonant frequencies of hydrogen protons in fat or water.
The quantity of resonating spins in a tissue expressed as a percentage of the proton density of water is spin density (ρ). repetition time (TR). echo time (TE). inversion time (TI).
spin density (ρ).
The time required for precessing spins to align with the constant external field to 63% of the maximum possible strength is spin density (ρ). repetition time (TR). You Answered echo time (TE). spin-lattice relaxation time (T1).
spin-lattice relaxation time (T1).
The time required for precessing spins to align with the constant external field to 63% of the maximum possible strength is spin density (ρ). repetition time (TR). echo time (TE). spin-lattice relaxation time (T1).
spin-lattice relaxation time (T1).
The time required after precessing spins have aligned at an angle to the external field due to an RF pulse losing 63% of their coherence is spin density (ρ). spin-spin relaxation time (T2). echo time (TE). spin-lattice relaxation time (T1).
spin-spin relaxation time (T2).
A ____ artifact is caused by the presence of metal in the patient. beam-hardening ring star streak
star
Each of the following is an example of an RF pulse sequence EXCEPT stationary. spin-echo. gradient. inversion recovery.
stationary.
Each CT projection is ______________________. displayed on the monitor stored on the computer printed on film All of the above
stored on the computer
A ____ artifact is caused by motion. beam-hardening ring star streak
streak
Which can serve as both the transmitter and receiver of the MRI signal? the stationary magnet the gradient coils the RF coils the cryogen coils
the RF coils
Before performing an MR scan on a patient with compromised renal function, the patient should be NPO for 24 hours. the patient's GFR should be assessed. an IVU should be performed. an ultrasound study of the kidneys should be done.
the patient's GFR should be assessed.
Superconductive magnets used in MR are characterized by field strengths of 0.2 T-0.35 T. the use of liquid helium as a cryogen. resistive magnets with vertical fields. the ability to turn the magnetic field on and off at will.
the use of liquid helium as a cryogen.
To produce magnetic field gradients in MRI, electromagnetic coils are oriented in one dimension. two dimensions. three dimensions. four dimensions.
three dimensions.
Each sweep of the source-detector around the body during CT is called a __________. rotation reconstruction translation projection
translation
CT image data is acquired in the coronal plane and reconstructed in the axial plane . transverse plane and reconstructed in any plane. sagittal plane . axial plane and reconstructed in the coronal plane.
transverse plane and reconstructed in any plane.
A three-dimensional element of the digital image pixel voxel cryogen Faraday cage
voxel
The gantry of the CT unit contains the post-processing workstation. operator's interface. x-ray tube. all of the above
x-ray tube.
