ASRT Exam 2 Flashcards by Mathew Boland

Kernels, also called convulsion algorithms, include all of the following, EXCEPT:
A. Smoothing filter.
B. Back projection.
C. Standard convolution algorithm.
D. Edge enhancement.

Answer: B - back projection.

Kernels are algorithms applied to the data to decrease noise or enhance certain aspects of the image. Back projection is an image process technique, NOT a convolution algorithm.

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What are kernels?

Kernels are algorithms applied to the data to decrease noise or enhance certain aspects of the image.

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Images are acquired along the _________ of the pt as they move through the scanner.

Z-axis (slice thickness).

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The x-axis runs from _____ to _____ of the pt.

Side to side.

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The y-axis runs what to the pt?

Anterior to posterior or posterior to anterior.

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The target anode of the CT X-ray tube is usually made of:

Tungsten.

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The basilar artery originates from what?

Originates when the vertebral arteries connect after entering the skull through the foremen magnum.

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What is the WW for an axial brain/head?

100.

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The disadvantage of using a power injection for IV contrast is:
A. It increases the chance of an allergic reaction.
B. It increases the chance of extravasating.
C. It increases the duration of the scan.
D. It provides a variable flow rate.

B - it increases the chance of extravasating.

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The purpose of the Picture Archival and Communicating System (PACS) is:
1. Archiving images.
2. Retrieving images.
3. Displaying images.

(Choose the correct #s)

1, 2, and 3.

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Which of the following is a clinical indication for CT colonography?
A. Adrenal mass.
B. Incomplete colonoscopy.
C. Crohn’s disease.
D. Abscess.

B - incomplete colonoscopy.

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To rule out a hip fracture, the coronal view of the hip should be aligned to the long axis of the :

Femoral neck.

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Where does the azygos vein reside?

Directly anterior to the thoracic spine & slightly to the right of the thoracic aorta.

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If a pt expresses concern about receiving IV contrast because she is currently breast feeding, the technologist should:

Reassure the pt that there is no risk from the small amount of contrast in breast milk (less than 1% of dose of contrast is excreted into breast milk).

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What is the scan delay for a CT brain exam to evaluate a lesion?

5 minutes.

In order for the contrast to pass the blood-brain barrier, a longer scan delay of 5 minutes is required.

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With overlapping slices of a MDCT scan, the multiple-scan average dose will:

Increase.

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All of the following are dose reduction techniques in CT, EXCEPT:
A. Automatic tube current modulation (ATCM).
B. Reducing scanner pitch.
C. Using scanner-specific protocols.
D. Limiting multiphase scans.

B - Reducing scanner pitch.

Reducing scanner pitch = increases the overlap of data = increases pt dose.

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Where does the transverse colon lie?

Runs horizontally in the upper abdomen directly inferior to the liver & the spleen and anterior to the kidneys.

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Which of the following anatomical structures should be included when imaging the Internal Auditory Canal?

Incus and stapes, the mastoid process through the petrous ridges, external auditory canal, and mastoid air cells.

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Multiplanar reformatting of CT data allows images to be reformatted into:
A. New orientations.
B. 3D renderings.
C. Color images.
D. New modalities.

A - New Orientations (sag, coronal, axial, or oblique planes).

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MPR is used to reformat the data into:

Sagittal, coronal, transverse (axial), or oblique planes.

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Gray (Gy) is the unit for measuring absorbed dose and:

Air kerma

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Define air kerma

Defined as the kinetic energy released in the air and is measured in Gy.

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A pt arrives to the department for a CT head without contrast following a head injury. Upon arrival, the pt provides a brief medical history. After a few minutes, the pt becomes unresponsive. The technologist should:
A. Complete the CT head exam as ordered.
B. Call for assistance, check the pts vital signs, and provide life support if necessary.
C. Transfer the pt back to the stretcher then return them to the emergency department.
D. Attach an AED to the pt to determine if they need CPR.

B - call for assistance, check the pts vital signs, and provide life support if necessary.

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Modern CT scanners use _________ detectors for better overall efficiency.

Scintillation. Also called solid state detectors are used in modern CT scanners b/c of their high absorption efficiency.

Which of the following contribute to noise on the CT image? 1. Pt size. 2. Tube current. 3. Post-patient collimation.

1 and 2 only.

Where does the bladder lie at?

Lies posteriorly to the pubic symphysis and anterior/inferiorly to the uterus.

Selecting thinner slices in ct will:

Increase dose. Selecting thinner slices for the same scan field results in 30-50% more radiation dose to the pt than thicker slices.

Isotropic imaging improves: A. Spatial resolution. B. Contrast resolution. C. Temporal resolution. D. Pt dose.

A - spatial resolution. When data is Isotropic, it means the dimensions of the voxel are equal on all sides. Equally-proportioned voxels improves spatial resolution in all planes.

Wide window width is useful for: A. Brain exams. B. Abdomen exams. C. Ankle scans. D. Bony pelvis exams.

B - abdomen exams. A narrow WW is beneficial for anatomy with similar tissue densities. A wide WW is needed for anatomy with varying tissue densities that benefit from more utilization of the Hounsfield scale.

With more detector rows, the amount of data collected per revolution of the X-ray tube will __________ and the scan time will __________.

Increase; decrease. More detector rows = increased area per revolution covered = decreased scan time.

Where is the spleen located?

Located in the LUQ of the abdomen and is lateral to the left kidney.

Dialysis pts receiving IV contrast must schedule their next dialysis treatment:

On their current dialysis schedule. Dialysis pts may maintain their current schedule of appointments without an additional treatment specifically as a result of contrast administration.

The CT technologist can control all of the following, EXCEPT: A. Pitch. B. Slice thickness. C. Scan time. D. Filtration.

D - Filtration. Filtration is built INTO THE CT SYSTEM.

The nasopharynx lies ________ to the sphenoid sinus.

Inferiorly.

A 125-slice helical scanner creates __________ images with each rotation of the X-ray tube.

125. A 64 slice scanner contains 64 detectors and a 125 slice scanner contains 125 detectors, and therefore generates 125 distinct images per rotation.

All of the following lead to reduce pt dose, EXCEPT: A. Increased filtration. B. Improved detector efficiency. C. Decreased pitch. D. Decreased mAs.

C - Decreased pitch

The appropriate WW for displaying the brain is: A. Wide. B. Narrow. C. A soft tissue window. D. A lung window.

B - narrow. A narrow WW is beneficial for exams in which the anatomical structures provide little variance in density. The density difference between the gray and white matter of the brain is minimal.

The _________ phase of tissue enhancement starts approximately ONE MINUTE after injection of IV contrast.

Nonequilibrium. (Starts right after the arterial phase).

Which WW and WL will demonstrate bony structure WITHOUT soft tissue details? A. WW2000; WL500. B. WW350; WL50. C. WW100; WL30. D. WW1500;WL(-)150

A - WW2000; WL500.

A CT calcium scoring exam assesses plaque deposits. What is the calcium score range for a moderate presence of plaque? A. 1 to 10. B. 11 to 100. C. 101 to 400. D. More than 400.

C - 101 to 400.

CT Calcium scoring for no evidence of plaque?

CT calcium scoring for minimal plaque?

1 to 10.

CT calcium scoring for mild plaque?

11-40.

CT calcium scoring for moderate plaque?

101-400.

CT calcium scoring for extensive plaque?

More than 400.

CT calcium scoring

No evidence = 0 Minimal plaque = 1 to 10. Mild plaque = 11 to 40. Moderate plaque = 101 to 400. Extensive plaque = more than 400.

The CT of the orbits to r/o a foreign body includes:

Axial, coronal and sagittal reformats. Axial coronal and sagittal reformats are included for any CT orbits exam (with or without contrast).

How much IV contrast is administered for a HRCT?

No IV contrast.

The scan delay for a CT abdomen pelvis exam is:

65 seconds.

If a brain hemorrhage is suspected, a __________ exam will likely be needed.

CT head without contrast.

The modulation transfer function (MTF) is calculated to determine the CT scanner’s: A. Spatial resolution. B. Ability to identify water. C. Contrast resolution. D. Dose accuracy.

A - spatial resolution. The MTF is used to determine spatial resolution of the scanner by assessing its ability to replicate a true object. The size of the structure on the CT scanner is compared to the known size of the structure in the phantom.

The matrix is:

A grid of pixels aligned in rows and columns.

If an unconscious pt arrives to the CT department following a traumatic injury, __________ consent is assumed b/c the pt cannot verbalize consent.

Implied.

An infant that will receive sedation for a CT scan should:

Receive no solid food for 4-6 hours prior.

The goal of premedication before IV contrast is to:

Reduce the risk of a contrast reaction.

Which linear interpolation setting reduces the distance between the reference points that eliminate misregistration? A. 360. B. 180. C. 90. D. 0.

B - 180. Linear interpolation can be set to either 180 or 360. A setting of 180 degrees results in less distance between reference points.

Axial imaging acquisition is best suited for all of the following, EXCEPT: A. CT head exams. B. CT brain perfusions. C. HRCT. D. Extremity CT.

D - Extremity CT. The step-and-shoot method allows for each axial slice to be acquired with the stationary pt couch to reduce movement.

Which acquisition method is used when administering contrast during a CT brain perfusion study? A. Axial. B. Helical. C. Fluoroscopy. D. Cine.

D - Cine. Cine acquisition is used when administering contrast for brain perfusion. The table does not move during the acquisition of data.

Interpolation is used during __________ image acquisition.

Spiral.

What glomerular filtration rate (GFR) indicates normal renal function?

>60 mL/min.

The Lambert-Beer equation compares the relationship between the intensity of the radiation and the:

Object’s density. The Lambert-Beer equation can be applied to a homogenous beam to compare the relationship between the intensity of the radiation and the object’s density.

All of the following are true regarding the topogram (scout) image, EXCEPT: A. The x-ray tube is stationary during exposure. B. The scout image is diagnostic. C. The topogram can be an AP or lateral view. D. The scout image is used to determine the SFOV.

B - The scout image is diagnostic.

The weighted average of data measurements divided by the pitch is the:

CTIVOL.

Effects of radiation exposure, such as cancers, which are not based on the amount of radiation received, are called:

Stochastic effects.

For a CTA scan to r/o thoracic aorta aneurysms, the Smart Prep monitors contrast enhancement at the ___________ and indicates the scan when it detects a HU of __________.

Ascending aorta; 150.

For bolus tracking during a CTA brain/neck the ROI is placed in the:

Carotid artery.

The right and left coronary arteries originate from the:

Ascending aorta.

The routine CT chest on a 64 slice MDCT scanner with IV contrast uses:

A scan delay of 35 seconds.

Filtration in CT affects pt dose by:

Removing the low quality X-rays from the X-ray beam.

A pt is receiving 100 mL of IV contrast at a flow rate of 4 ML per second. How long will it take for the contrast be injected?

25 seconds. 100 / 4 = 25 seconds. (ML TOTAL) / (FLOW RATE)

Prior to administering contrast, the CT technologist should verify all of the following, EXCEPT: A. The right patient. B. The right dose. C. The right route. D. The right physician.

D - the right physician.

Which of the following HU ranges is most likely for a maximum intensity projection (MIP)? A. -1000 to +500. B. -500 to 0. C. 0 to +500. D. +500 to +1000.

D +500 to +1000. Higher value = brightest voxels.

Due to pt size, the organ dose children receive from an identical CT scan is: A. Greater than for adults. B. Less than for adults. C. The same as for adults. D. Double what adults receive.

A - greater than for adults. They will receive more dose b/c of the lack of adipose tissue surrounding their body to reduce organ exposures.

How do bowtie filters reduce pt dose?

Bowtie filters reduce beam intensity peripherally, corresponding to the thinner area of the pts body.

The correct formula for calculating dose-length product (DLP) is:

DLP = CTDLvol x scan length.

The appropriate needle size to deliver IV contrast at rates of 3 mL/s or higher is:

20 gauge.

Beam hardening artifacts occur when __________ X-rays are ___________.

Low-energy; absorbed.

When a voxel contains more than one tissue type, the CT number for each tissue is averaged together creating a:

Partial volume artifact.

The scan field of view (SFOV) affects: A. Quantity of raw data. B. Pixel size. C. Matrix size. D. Spatial resolution.

A - Quantity of raw data.

For a CT biopsy, the CT technologist should do all of the following, EXCEPT: A, Wear a lead apron. B. Provide shielding to the pt. C. Hold the pt in position during the scan. D. Document the pts dose in their electronic medical record.

C - hold the pt in position during the scan.

For a routine CT chest, the pt should be positioned: (Choose the correct #s) 1. Arms above their head. 2. Headfirst into the gantry. 3. Prone.

1 and 2 only.

The data acquisition system measures the attenuated beam as it arrives at t he detectors, providing a measurement called the:

Ray sum.

Contrast resolution is improved by: A. Doubling mAs. B. Decreasing the signal-to-noise ratio. C. Larger pt size. D. Applying a bone algorithm.

A - doubling mAs.

In a gated CTA chest, images are acquired:

With the heart in DIASTOLE. Diastole = when the heart is at rest (least amount of motion!!).

A mild side effect of IV contrast administration is: A. Bronchospasm. B. Nausea and vomiting. C. Profound hypotension. D. Severe urticaria.

B - Nausea and vomiting.

What is the formula: # of detectors x Slice Thickness?

Beam width for MDCT

Back projection is an __________ technique not a convolution algorithm!

Imaging processing technique.

The passage of x-ray photons through tissues without interaction is described as:

Transmission.

ASRT Exam 2 Flashcards

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