CT Test #3

The QC test that evaluates the standard deviation as complared to [(mA • Slice width) − 1/2] is: a. #1: Average CT Number of Water b. #3: High Contrast Resolution c. #4: Low Contrast Resolution d. #17: Noise Characteristics

#17: Noise Characteristics

The QC test seen below is: CIRCLE with cross hair in the middle a. #2: Standard deviation of CT# in Water b. #3: High contrast resolution c. #4: Low contrast resolution d. #14: CT number vs patient size

#2: Standard deviation of CT# in Water

The most commonly used radiopharmaceutical for positron emission tomographic imaging is:

18F-fluorodeoxyglucose

When positrons combine with electrons in the body, this produces an annihilation event, which creates 2 photons 180o apart. What is the energy of each of these photons?

511 keV

The artifact seen in the CT image below is an example of:

Beam Hardening

The procedure that describes a geometric simulation process that provides beam arrangements and treatment fields without any dosimetric information is:

CT simulation

imaged in SPECT

Gamma emissions

Check all that apply. Which of the following can routinely be done to reduce pediatric radiation exposure during a CT scan? [mark all correct answers] a. Increase the mA (or mAs) b. Increase the pitch c. Proper centering of the part in the gantry aperture d. Use automatic mA adjustment

Increase the pitch Proper centering of the part in the gantry aperture Use automatic mA adjustment

Which of the following is incorrect about the CT simulator used in radiation therapy treatment planning?

Larger bore dimension to accommodate multiple patient positions and to ensure the inclusion of the entire patient anatomy utilizing a small SFOV

Which of the following is an example of a Stochastic Effect?

Leukemia

line that connects two detectors where an annihilation event has occurred

Line of Response

The artifact seen in the PET/CT image below is an example of:

Misregistration

What is used to measure radiation exposure in CT?

Pencil ionization chamber

Which of the following is true concerning PET imaging?

Photons are detected coincidentally by a ring of scintillation detectors

The artifact seen in the CT image below is an example of:

Ring Artifact

Check all that apply. Which are the unit(s) of radiation exposure in air? [mark all correct answers] a. Roentgen (R) b. Sievert (Sv) c. Air Kerma (Gya)

Roentgen (R) Air Kerma (Gya)

CT simulation process in order

Scan the patient in the CT scanner pt is positioned, immobilized, scanned in exactly the same position as treatment machine Plan the treatment and CT simulation beam placement and treatment design are executed using the virtual simulation software Treatment setup CT sim results are used to set up pt in the treatment machine

first lymph node to receive lymph drainage from a tumor

Sentinel lymph node

What type of reconstruction filter will make noise less visible in the CT image?

Smoothing / Soft Tissue

Which of the following is false concerning the fusion of PET and CT imaging?

The radiation dose is halved when the modalities are fused

Check all that apply. In designing the scan for each patient, you should consider: [mark all correct answers] a. patient size b. patient age c. body habitus d. pathology/condition e. scanner ability f. time of day

a. patient size b. patient age c. body habitus d. pathology/condition e. scanner ability

Check all that apply. Which of the following are a part of the basic tenets of CT Quality Control? a. the same person performing the tests each time b. accurate record keeping c. accurate interpretation of results d. all tests performed by medical physicist e. QC testing on a set schedule/regular basis

accurate record keeping accurate interpretation of results QC testing on a set schedule/regular basis

What types of artifacts can arise from insufficient projection sampling or from insufficient view sampling? An example would be when the patient's arm is at their side during an Abdomen study.

aliasing artifacts

Which of the following are factors of dose that can be controlled by the technologist? a. technical factors b. patient centering c. x-ray beam collimation d. all of the above

all of the above

Which of the following factors affects in-plane spatial resolution? a. focal spot size b. detector cell size c. sampling frequency d. all of the above

all of the above

What provides the most comprehensive approach to computed tomography dose reduction?

angular-longitudinal tube current modulation

The process by which a positron and an electron combine and are converted to energy is referred to as ______.

annihilation

The beam-hardening artifact would be most visible after the x-ray beam passes through:

bone

Test #1: Average CT Number of Water should be done: a. daily b. weekly c. monthly d. annually

daily

If the pitch increases by 2, the dose will:

decrease by 1/2

The radiographic image constructed from CT data used in CT simulation is the:

digitally reconstructed radiograph (DRR)

What is used to quantify the risk from partial body exposure to that from an equivalent whole body dose?

effective dose

Decreasing slice thickness will result in increased spatial resolution, decreased contrast resolution and increased quantum noise.

false

True or False? Based on 2006 data, CT exams count for approximately 35% of the population's collective dose from medical procedures.

false

True or False? If the AAPM recommends against bismuth in-plane shielding, you don't have to use out-of-plane lead shielding.

false

True or False? If you are in a hurry to scan a patient, you do not have to perform a tube warm-up, even if the unit has not been operated for several hours.

false

True or False? It is best to pick a frequently used technique and keep the same physicist for each specific test.

false

True or False? It is not necessary to center the patient properly in the gantry aperture as the CT unit will automatically use the ATCM to reduce exposure, regardless of where the patient is centered.

false

True or False? Regulatory agencies do not require any standard of quality.

false

True or False? The ACR requires the CT technologist to be able to identify and correct image artifacts from a water phantom on a yearly basis.

false

What is the unit used in the computed tomography dose index (CTDI)?

gray (Gy)

A QC test tool seen below that consists of plastic drilled with holes of varying sizes (filled with water or air) is used to evaluate: STRAIGHT LINES OF CIRCLES a. average CT number of water b. standard deviation of the CT number of water c. high contrast resolution d. low contrast resolution

high contrast resolution

A small focal spot size selection will result in:

higher spatial resolution

software that can integrate image data from CT, MRI, PET, SPECT, and sonography to produce fused images that now contain highly informative data

image fusion

What is the most straightforward way to reduce or eliminate the motion of an object?

increase scan speed

What technical factor determines the penetrating power of the photons coming from the x-ray tube?

kVp

What dose-response model is a radiation risk model most favored by radiobiologists in estimating the risk of exposure in radiology?

linear non-threshold

Which of the following refers to the relationship of CT numbers to the linear attenuation coefficients of the object to be imaged?

linearity

A QC test tool seen below that consists of plastic drilled with holes of varying sizes (containing a liquid whose CT number is similar to plastic) is used to evaluate: CIRCLE WITH BLACK DOTS a. average CT number of water b. standard deviation of the CT number of water c. high contrast resolution d. low contrast resolution

low contrast solution

Which of the following operator-controlled factors affects image noise?

mA slice thickness scan time

Which technical factor determines the quantity of photons (dose) incident on the patient for the duration of the exposure?

mAs

The artifact seen in the CT image below is an example of:

metallic implants

Which of the following can be used to compare the performance of different CT units?

modulation transfer function (MTF)

The #1 limiting factor of CT image quality is:

noise

The averaging of all tissues in a voxel is:

partial volume averaging

The artifact seen in the CT image below is an example of:

patient motion

A positron-emitting, radioactive atom, upon transformation, may emit a _________.

positive beat particle

An advantage of the incorporation of CT into a hybrid imaging study is it can _

provide anatomic correlation for PET or SPECT

Check all that apply. The overall goals of automatic tube current modulation are to: [mark all correct answers] a. provide consistent image quality b. increase scan speed c. increase dose to the patient d. decrease dose to the patient

provide consistent image quality decrease dose to the patient

Which tests the performance of a computed tomography scanner on a number of parameters and entails fixing the problem if necessary?

quality control

An advantage of SPECT over PET is the ability to image ______________.

radiopharmaceuticals used in planar nuclear medicine.

The device most commonly used to acquire SPECT data is the _______.

rotating gamma camera

Metallic materials usually present as ____________ artifacts on the image.

streak

What is an indication of a CT system's ability to freeze motions of the scanned object?

temporal resolution

Partial volume artifacts can be reduced with _____________ slice acquisitions and computer algorithms.

thinner

Decreasing mA will result in increased spatial resolution, decreased contrast resolution and decreased quantum noise.

true

True or False? A dose notification value is triggered when a single planned, confirmed scan is likely to exceed a pre-programmed value (CTDIvol and/or DLP).

true

True or False? In a homogeneous water phantom, the CT number should measure zero at any location in the phantom.

true

True or False? Low mA will result in increased image graininess and noise.

true

True or False? The dose distribution in CT more uniform than in radiography.

true

True or False? The graph below is an example of Slice Sensitivity Profile.

true

True or False? When performing Test #6: Uniformity of CT number, you will use the same phantom as used in Test #1.

true

True or false? Artifacts can degrade image quality, affect the perceptibility of detail, and lead to misdiagnosis

true

The QC test seen below is: SQUARE with lines in it

#12: Pitch and slice width

The gantry aperture in CT simulation typically measures ____ cm.

85

How does the spatial and contrast resolution of CT compare to radiography?

CT has worse spatial resolution and better contrast resolution.

What dose descriptor is used to describe a the energy absorbed per unit of mass over a scanned length?

DLP

Which of the following is measured in line pairs per millimeter?

In-plane spatial resolution

imaged in PET

Positron emissions

_________ occurs as a result of a low number of photons detected.

Quantum noise

True or false? Total data acquisition time is determined by gantry speed, helical pitch, and detector coverage.

True

What is the amount of energy absorbed per unit mass of material?

absorbed dose

What term refers to the automatic control of the milliamperage in two directions during data acquisition by specific technical procedures in CT?

automatic tube current modulation

Check all that apply. What is the process by which additional rotations before and after the planned length are taken?

b. overranging c. z- overscanning

Attenuation correction __________.

can be performed using the CT portion of the hybrid scan

If the pitch increases, the dose:

decreases

Which of the following can be used for CT simulation? a. CT-on-rails b. fan beam MVCT c. kV- and MV cone beam CT d. diagnostic CT with simulation software e. all of the above

e. all of the above

Cross-plane spatial resolution is traditionally described by the:

slice-sensitivity profile