A new computed tomography (CT) protocol requires scanning the liver at exactly 25 seconds after initiating intravenous (IV) contrast injection. This can be accomplished by which scan timing method? correct answers Scan time delay
There are several ways to time a contrast bolus. If the patient is...
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A new computed tomography (CT) protocol requires scanning the liver at exactly 25 seconds
after initiating intravenous (IV) contrast injection. This can be accomplished by which scan
timing method? correct answers Scan time delay
There are several ways to time a contrast bolus. If the patient is to be scanned at a specific
time after initiating contrast, the technologist will need to set the exact scan delay time. The
test bolus and bolus tracking methods cannot be used to set exact times.
Increasing the reconstruction slice thickness results in: correct answers Visualization of more
anatomy with decreased spatial resolution
Increasing the reconstruction slice thickness results in visualization of more anatomy with
decreased spatial resolution.
Increasing the reconstruction slice thickness adds more anatomic data to each image. As a
result, this allows visualization of more anatomy. The major disadvantage of thicker slices is
decreased spatial resolution. As slice thickness increases, spatial resolution decreases.
During the monitoring phase of bolus tracking you see several images showing no contrast at
all. Possible explanations include:
-The contrast injection was never initiated
-The contrast has infiltrated
-The saline and contrast syringes were loaded backwards
-All of the answer options listed are correct correct answers All of the answer options listed
are correct
This is a bad situation! Several things might have gone wrong, including all scenarios listed.
Hopefully, the technologist simply forgot to start the contrast infection. More likely, the
contrast has infiltrated and is filling the patient's arm. In some cases, the technologist may
load these syringes backwards, which results in saline flowing through the body during the
scan rather than contrast.
Which of the following is a potential reason to DECREASE the IV contrast volume used
during a CT scan?
The IV contrast volume is commonly decreased for smaller patients, especially pediatric
patients. The other options listed, late require an increase in contrast volume.
Which phase of contrast enhancement in the abdomen peaks at 50-60 seconds after initiating
intravenous (IV) injection? correct answers Portal venous phase
,Contrast enhancement through the abdomen occurs in this order: 1) arterial phase at about 30
seconds, 2) portal venous phase at about 60 seconds, and 3) delayed phase at about 5 minutes
(or more).
The acquisition slice thickness used during a scan is determined by the technologist.
Acquisition thickness refers to which of the following?
-Thickness of activated detector rows
-Thickness of anatomical data averaged into each image
-Total width of the x-ray beam
-Space between adjacent slices correct answers Thickness of activated detector rows
By definition, the acquisition thickness is the thickness of activated detector rows. The
thickness of these rows can be changed by combining rows together. Acquisition thickness is
NOT the same as reconstruction slice thickness (the thickness of anatomical data averaged
into each image).
Which of these venous access devices are sometimes labeled for CT power injection?
Some Central lines, called ports, are labeled to be used for CT power injection. Dialysis
catheters in jugular lines are almost never intended to be used for power injection.
Displayed CT images are processed to display a specific amount of anatomical data in each
image. This is the: correct answers Reconstruction slice thickness
The reconstruction slice thickness refers to the thickness of anatomical data averaged into
each image. Thinner slices have better spatial resolution, but thicker slices have less noise.
Which two contrast injection methods are useful for precisely timed angiographic
procedures?
Scan delay time
Test bolus
Bolus tracking
Fixed time delay correct answers Test bolus
Bolus tracking
The test bolus method and bolus tracking methods are both used to precisely time
angiographic scans with maximum contrast enhancement.
These methods are preferred over setting a simple scan delay time because each patient can
be slightly different.
Consider a patient admitted to the emergency department for flank pain, hematuria, and
suspected renal stone. CT imaging for the initial assessment of the collecting system should
be performed during which phase of contrast enhancement? correct answers Non-contrast
,Evaluation for renal stone should initially be performed without contrast. Renal stones appear
white, and contrast also appears as white. The use of contrast could disguise the presence of
renal stones, therefore, renal stones are best identified without the use of intravenous contrast.
What is the purpose of warming intravenous (IV) contrast prior to injection? correct answers
Decreased viscosity
Just like warming maple syrup, warming intravenous contrast decreases the viscosity. This
has no effect on radiopacity or toxicity. The purpose of warming contrast is to decrease
viscosity and therefore decrease the risk of extravasation.
One reason for decreasing the IV injection rate during CT scanning is
High-speed scanner (16 rows or more)
Poor IV catheter patency
Angiographic scanning
Geriatric imaging correct answers Poor IV catheter patency
There are several reasons we may decrease the injection rate for IV contrast. Of the options
listed, poor I patency is the only valid reason. High speed scanning sometimes requires a
higher injection rate. Angiographic
-scanning may also require a higher injection rate. Geriatric Imaging does not necessarily
require any change in injection rate.
The abrupt starting and stopping of the patient table during axial scanning can result in:
correct answers Motion artifact on the images
One downside to axial scanning is the abrupt starting and stopping of the table. This has the
potential to cause the patient to move and induce motion artifact in the images.
Which of the following is NOT a common reason to use contrast enhancement during CT
scanning?
-Differentiate between normal tissues
-Differentiate between normal tissues and abnormalities
-Add visual contrast to the images
-Reduce patient radiation exposure correct answers Reduce patient radiation exposure
Contrast has many uses, but it does NOT reduce the patient radiation exposure. The use of
contrast does allow the technology to reduce the technique or make any other change that
might reduce the patient dose.
The primary reason for monitoring intraluminal pressure during intravenous (IV) contrast
injection is to: correct answers Avoid contrast extravasation
Contrast extravasation is the result of excessive intraluminal pressure.
Extravasation can be controlled or prevented by monitoring the pressure.
This is why power injectors are usually set with a maximum pressure at which the contrast
rate is decreased to avoid extravasation.
, The average flow rate recommended for venous phase imaging of the abdomen is: correct
answers 3 ml per second
The typical flow rate for venous phase Imaging of the abdomen, and most other body parts, is
3 ml per second. This can vary some between institutions. This can also vary based on the
quality of IV access.
Which phase of I contrast enhancement is ideal for initial imaging of intracranial
hemorrhage? correct answers Non-contrast
Intracranial hemorrhage (bleeding) is an example of a pathology BEST viewed without IV
contrast. Both contrast and blood look white in the brain, so it's important to image brain
WITHOUT contrast when looking for blood.
Assume that all variables remain constant: Compared to a 1 mm reconstructed slice, a 5 mm
reconstructed slice will usually result in what changes? correct answers Decreased image
noise
Decreased spatial resolution
Thicker slices result in decreased spatial resolution (not good), but also in decreased image
noise (good!). Changes in the reconstruction slice thickness have no effect on the patient
dose. This makes sense since slice thickness can be changed after the scan is over.
The first phase of IV contrast enhancement for most organs is the: correct answers Arterial
phase
After IV contrast goes through the heart, contrast arrives in the body's organs through the
arteries. This is called the arterial phase of contrast enhancement.
Intravenously injected contrast can be viewed exiting organs during which phase of
enhancement? correct answers Venous phase
After IV contrast goes through the heart, contrast arrives in the body's organs through the
arteries. After circulating through the organ, the contrast leaves the organ through the veins.
This is called the venous phase of contrast enhancement.
Advantages of helical scanning over axial scanning include:
Decreased scan time
Decreased patient dose
Increased spatial resolution correct answers Decreased scan time
Decreased patient dose
Helical scanning comes with several advantages, especially decreased scan time and
decreased patient dose. However, helical scanning does NOT increase spatial resolution.
Spatial resolution is slightly decreased.
How should the gantry be oriented when scanning direct coronal CT sinuses with the patient
in the prone position? correct answers Perpendicular to the hard palate
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