RADT 440 Exam 4

What specifically do the CT detectors measure? A. attenuation B. patient dose C. primary radiation D. scatter radiation

A. attenuation

The RF signal strength determines: A. brightness B. field strength C. section thickness D. spatial resolution

A. brightness

First generation CT scanners scanned the ____ only A. head B. thorax C. abdomen D. pelvis

A. head

The MHz frequency magnetic field for MRI is produced by a(n): A. radiotransmitter coil B. optical cable C. digital converter D. none of the above

A. radiotransmitter coil

The concentration of scintillation detectors affects the _____ of the CT image. A. spatial resolution B. contrast resolution C. overall density D. motion artifact

A. spatial resolution

The new development in the fourth generation CT scanner is the _______. A. stationary detector array B. fan beam C. reduced patient dose D. ring artifact

A. stationary detector array

Which of the following statements is not true about the nuclei used in MRI A. they must be radioisotope forms of the nuclei B. they should be found in abundance in the human body C. they must have an odd number of protons and neutrons D. they must be affected by an external magnetic field

A. they must be radioisotope forms of the nuclei

MRI has been useful for imaging many areas of the body, particularly the brain, due to: A. the ability to see calcium deposits B. differentiation of gray matter from white matter C. new motion techniques D. fat suppression

B. differentiation of gray matter from white matter

Generally MRI is considered safe; however, there are some hazards, which would include: A. rapid echo spin B. local burns from wires on a patient C. headaches from the magnetic field D. spontaneous random molecular motion

B. local burns from wires on a patient

The principal drawback of the first generation CT scanner was the A. high patient dose B. long scanning time C. translate-rotate assembly D. degree of rotation

B. long scanning time

The pixel size is reduced when the _____ size is increased and the ______ size is fixed. A. FOV, matrix B. matrix, FOV C. hounsfield unit, FOV D. FOV, hounsfield unit

B. matrix, FOV

The wobbling motion of the proton when it is placed in a strong magnetic field is called: A. frequency B. precession C. resonance D. a signal

B. precession

The patient dose in CT is determined by the _____ collimator A. predetector B. prepatient C. post patient D. both a and b

B. prepatient

A _____ artifact is caused by detector error A. beam- hardening B. ring C. star D. streak

B. ring

Which can serve as both the transmitter and receiver of the MRI signal? A. stationary magnet B. gradient coils C. RF coils D. cryogen coils

C. RF coils

The calculation of CT umbers is based upon the calculation of A. half value layers B. half lives C. attenuation coefficients D. pitch

C. attenuation coefficients

The ____ is determined by how well the detector converts the absorbed photon information to a digital signal for the computer A. capture efficiency B. absorption efficiency C. conversion efficiency D. response time

C. conversion efficiency

There are a variety of magnet types that can be used for MRI. Resistive and superconductive magnets are both: A. permanent magnets B. weak magnets C. electromagnets D. used at up to 3 tesla

C. electromagnets

Each pixel of information in the CT image contains numerical information in ______ units. A. voxel B. reconstruction C. hounsfield D. pixel

C. hounsfield

CT is able to differentiate between tissues with similar densities compared with conventional radiography due to: A. digital magnification B. the use of computer for data processing C. improved contrast resolution D. axial slices

C. improved contrast resolution

Hydrogen is used for imaging in MRI because it: A. has a large nucleus B. has a large precession C. is the most common element in the body D. is the only nucleus that can be imaged

C. is the most common element in the body

The gyromagnetic ratio is the ratio of the magnetic: A. moment to the moment of magnetic force B. force to the moment of inertia C. moment to the moment of inertia D. none of the above

C. moment to the moment of inertia

In CT to achieve coronal or sagittal sections: A. the gantry is repositioned B. the patient is repositioned C. reconfiguration software is implemented D. none of the above

C. reconfiguration software is implemented

The more common type of magnet in clinical use today is the: A. permanent magnet B. resistive magnet C. superconductive magnet D. gradient coil magnet

C. superconductive magnet

To produce magnetic field gradients in MRI, electromagnetic coils are oriented in A. one dimension B. two dimensions C. three dimensions D. four dimensions

C. three dimensions

MRI has been achieved with ____ magnets A. resistive B. permanent C. superconductive D. all of the above

D. all of the above

Patient precautions with MR scanning include: A. claustrophobia B. not touching the inside of the gantry during scanning C. ferromagnetic implants or prosthetic devices D. all of the above

D. all of the above

The CT console provides the radiographer access to A. the software program B. data acquisition C. data display D. all of the above

D. all of the above

The CT table is A. made of carbon graphite B. rated for maximum weight C. motor-driven D. all of the above

D. all of the above

The resolution of the CT iamge depends on the A. pixel B. voxel C. matrix size D. all of the above

D. all of the above

A possible patient reaction to rapid venting of the supercooled liquid gases int he superconductive magnet into the examination room would be: A. tachycardia B. bradycardia C. embolus D. asphyxiation

D. asphyxiation

What is the name of the materials used as cooling agents in superconducting magnets? A. refrigerants B. halogens C. inhalants D. cryogens

D. cryogens

Fourth generation CT scanners use the following configuration: A. translate tube and rotating detectors B. rotating tube and detectors C. only rotating detectors D. only rotating tube

D. only rotating tube

T or F Magnetic field strength and distance are related according to the inverse square law

FALSE

T or F When a rapidly spinning nucleus is subjected to a magnetic field, it will stop spinning

FALSE

all tissues within the same strength magnetic field respond at the same relaxation rates

FALSE

the rate of precession decreases as the strength of the magnetic field increases

FALSE

T or F The HU of water is always 1

FALSE (it's 0)

T or F All protons in a nucleus of a given type of element will rotate with exactly the same frequency

TRUE

T or F CT radiation beams are double collimated

TRUE

T or F CT x-ray tubes produce a massive amount of heat as compared to conventional radiographic tubes

TRUE

T or F Motion is a problem in MRI because of extremely long scanning times

TRUE

T or F T is also known as transverse relaxation time

TRUE

T or F The paramagnetic contrast agent of choice for MRI is gadolinium

TRUE

T or F There is no known biological risk from the magnetic field of an MRI unit

TRUE

T/F the loud "knocking" heard during an MRI study is due to the gradient coils

TRUE

a series of tissue density values that evolved for CT measurements is called ---- units a. hounsfield b. h & d c. attenuation d. iterative

a. hounsfield

compared with CT image acquisition MRI can obtain images a. independently in any plane b. only in the sagittal plane c. only in the coronal plane d. in the sagittal and coronal planes

a. independently in any plane

the MHz frequency magnetic field for MRI is produced by a/an a. radio transmitter coil b. optical cable c. digital converter d. none of the above

a. radio transmitter coil

what imaging modality is most frequently used to study the soft tissue structures of the knee a. CT b. MRI c. conventional radiography d. ultrasound

b. MRI

the wobbling motion of the proton when it is placed in a strong magnetic field is called a. frequency b. precession c. resonance d. signal

b. precession

the Larmor frequency is the ---- frequency a. quantum b. precessional c. linear d. all of the above

b. precessional

Contemporary CT scanners use solid state detectors. These detectors utilize a. sodium iodide crystals b. rare earth ceramic scintillators c. xenon gas d. freon gas

b. rare earth ceramic scintillators

what is the principal disadvantage of third generation CT scanners a. slow speed b. ring artifacts c. patient dose d. poor reconstruction

b. ring artifacts

dose in CT is considered to be a. independent of size b. size dependent c. related to the CT numbers d. similar to a chest exam

b. size dependent

MRI depends on interactions with a. electrons b. the nucleus c. soft tissue d. ionizing radiation

b. the nucleus

superconductive magnets used in MR are characterized by a. field strength of .2T-.35T b. the use of liquid helium as cryogens c. resistive magnets with vertical fields d. the ability to turn the magnetic field on and off at will

b. the use of liquid helium as cryogens

CT scan pitch uses all of the following technical parameters EXCEPT a. slice thickness b. 360* gantry rotation c. acquisition mAs d. table increment

c. acquisition mAs

what is the major advantage of volume CT over standard CT imaging a. generates less tube heat units b. allows cardiovascular scanning because of shorter scanning times c. allows a volume of tissue to be examined rather than individual slices only d. requires less dose be given to the patient

c. allows a volume of tissue to be examined rather than individual slices only

MR spectroscopy is used to look at a. abdominal lesions b. blood flow c. chemical composition d. diffusion and perfusion

c. chemical composition

the most common reporting method of dose reporting on the present scanners is a. multiple scan average dose (MSAD) b. computed tomography dose index (CTDI) c. dose length product (DLP) d. computed tomography dose index volume

c. dose length product (DLP)

contrast enhanced MR images use ---- as the contrast material of choice a. iodine b. barium c. gadolinium d. hydrogen

c. gadolinium

CT scanners operate on ____ voltage generation a. single phase b. three phase c. high frequency d. twelve pulse

c. high frequency

the absorption of RF energy is referred to as a. frequency b. precession c. resonance d. proton density

c. resonance

A _____ artifact is caused by the presence of metal in the patient A. beam-hardening B. ring c. star d. streak

c. star

the ---- generation of CT scanners was the first to have the fan beam transect the entire patient at all times a. first b. second c. third d. fourth

c. third

the CT radiation beam is collimated a. at the tube exit b. at the detector entrance c. prepatient and postpatient d. all of the above

d. all of the above

the third generation of CT scanners allowed for further reduction in a. scanning time b. scattered radiation c. fan beam width d. both a and b

d. both a and b

A _____ artifact is caused by motion A. beam-hardening B. ring c. star d. streak

d. streak

the patient dose in CT is determined by the ---- collimator

prepatient