CT REGISTRY COMPREHENSIVE EXAM UPDATED
QUESTIONS AND ANSWERS SURE A+
✔✔A CT scanner with a limiting resolution of 15 lp/cm can resolve an object as small as
- ✔✔The minimum object size that a CT scanner can resolve may be calculated by
taking the reciprocal value of the scanner's limiting resolution. The reciprocal of 15 lp/cm
is 1/15 lp/cm. This is equivalent to 10/15 lp/cm, which equals 0.6 mm/lp. Because a line
pair (lp) is equivalent to a line and space adjacent to it, this value may be divided in half
to provide the minimum object that this scanner can resolve: 0.3
✔✔By CT criteria, a solitary pulmonary nodule may be defined as a focal area of
increased density in the lung that is smaller than - ✔✔Solitary pulmonary nodules are
typically ovid focal areas of increased density that are less than 3 cm in diameter. Any
lesion larger than 3 cm is reffered to as a focal mass, with an increase propensity for
malignancy.
✔✔Evaluation of the venous vascular structures of the brain is known as - ✔✔CT
Venography (CTV) of the brain is a cariation of the CTA technique whereby the timing of
data acquisition is optimized for the period of peak venous opacification
✔✔sampling frequency? - ✔✔The sampling frequency, or views per rotaion (VPM),
controls the volume of transmission data acquired for each gantry rotation. Very small
objects exhibit high spatial frequencies that only systems with high sampling rates will
be capable of resolving.
✔✔After initiation of rapid bolus administration of an iodinated contrast agent, the
excretory phase of renal contrast enhancement occurs at approximately - ✔✔3-5
minutes..The excretory phase is a delayed-imaging phase that begins approximately 3
minutes after the initiation of contrast agent administration. During this phase, contrast
material has been excreted into the real calyces, opacifying the renal pelvis and the
remainder of the urinary collecting system (ureters, bladder). The excretory phase best
demonstrates the filling defects and potential lesions involving the urothelium, such as
those from transitional cell carcinoma (TCC)
✔✔The Propensity of a contrast agent to cause fluid to move from the extravascular
space to the intravascular space is called - ✔✔Osmolality
An important characteristic of iodinated radiopaque contrast media, osmolality describes
the propensity of the agent to cause fluid from outside the blood vessel (extravascular
space) to move into the bloodstream (intravascular space)
✔✔For Ct exams of the pelvis.. which types of contrast should be used? - ✔✔IV
contrast
low dense barium sulfate
,During CT examination of the pelvis, both intravenous and oral contrast agents are
commonly administered. An intravenous contrast agent is important in differentiating
pelvis blood vessels for lymph nodes. An oral contrast agent serves to opacify the small
and large colon and greatly improves their visualization. Oil-based contrast media are
not commonly used for CT procedures.
✔✔The water-soluble oral contrast agents used for CT scans of the abdomen and
pelvis should contain approximately__________ iodine - ✔✔A solution of 2%-5%
iodinated water-soluble contrast agent and water provides sufficient bowel opacification
for CT studies of the abdomen and pelvis. Some institutions may use a flavoring agent
to the solution or used a flavored contrast for ease of consumption. Common water-
soluble contrast media include gastrografin and hypaque.
✔✔The vertebral level at which the adult spinal cord ends is - ✔✔The adult spinal cord
ends between L1 and L2
✔✔An enema containing positive contrast material administered into the large bowel is
needed prior to the CT examination of the pelvis. Of the following, which is a sufficient
dose to opacify the rectosigmoid area of the colon? - ✔✔To opacify the rectosigmoid
region, a dose of 150-250 mL is sufficient. To opacify the complete large bowel a dose
of 300 - 500 mL is needed.
✔✔Prothrombin measures the amount of time necessary for a person's blood to
coagulate. - ✔✔10 to 14 seconds are within normal range
✔✔A CT scan of the pelvis resulted in a dose at the entrance to the patient's skin of 6
rads, the dose at the center of the patient will be _____ mGy, if it is two-thirds less than
the skin dose. - ✔✔The skin dose of 6 rads - 4 rads = 2 rads( 1 Gy = 100 rads)
✔✔A given CT exam yields a CTDI of 4.5 rads, with a slice thickness of 10mm, and a
2mm gap between slices, the MSAD for this exam is ________ rads. - ✔✔The MSAD is
equal to the CTDI X the ratio of the slice thickness to the table increment. With a 2mm
gap and a 10mm slice the table increment will be 12mm. The MSAD = (4.5 rads) X
(10mm/12mm)
✔✔What is the average range for activated partial thromboplastin time? - ✔✔The partial
thromboplastin time is a measure of blood-clotting ability. The range is given in an
average due to the variations in individual laboratory practices. The acceptable range is
between 28-34 seconds.
✔✔The job of the array processor is - ✔✔reconstruction of the projected attenuation raw
data into CT images
,✔✔To provide the largest image for the viewer on a 14 X 17 inch film, which of the
following CT film formats should be used? - ✔✔The arrangement of CT images on a
sheet of x-ray film will determine the size of the image for viewing. A 4:1 format stores
four large images on one single 14 X 17 sheet. The more images on one sheet the
smaller the image for viewing.
✔✔The major disadvantage of the early back-projection method of image reconstruction
is the appearance of the - ✔✔The star artifact resulted from the back-projection method
of image reconstruction used in older CT scanners. The artifact is removed by the use
of a convolution filter found in the filtered back-projection method used today.
✔✔When describing tube interscan delay time, which of the following are true?
1. The time required for the tube to rotate 360 degrees around the patient.
2. The time between the end of one scan and the start of the next scan, allowing the
tube to cool.
3. The time necessary for the production of photons to begin after applying the voltage
to the tube. - ✔✔1 only
✔✔Star-like artifacts on structrues at the edges of the CT images may be the result of a
cone beam artifact - ✔✔True
✔✔Where is the begining and endpoint of a CT routine chest? - ✔✔Lung Cancer
ussually metastisizes to the adrenal glands. Soft tissue windows should be through the
adrenal glands and lung windows can be only from above apices to the bottom of the
lungs.
✔✔The cause of the cupping artifact is? - ✔✔The low energy photons are attenuated
when they pass through the body resulting in the central tissues appearing darker in
signal intensity than the peripheral tissues. This phenomenon is sometimes called
cupping due to beam hardening on the image resulting in the contour of a cup
appearance.
✔✔Lung window? - ✔✔1400-1600 WW
-400-(-)600
✔✔Water soluble based oral contrast (gastroview) should not be used when? -
✔✔esophogeal perforation is suspected- This type of contrast should be used with this
diagnosis barium should not be used
✔✔As slice thickness is decreased, which of the following statements is true? - ✔✔A
decrease in both partial volume artifacts and edge gradient artifacts.
, ✔✔The edge gradiant effect is reduced by using a CT scanner with a small detector
aperture and thin slices - ✔✔True..Smaller apertures and thinner slices improve the
severity of edge gradiant effect. Greater data sampling rates would improve the edge
gradiant effect also.
✔✔Which of the following diabetic medications should be discontinued for 48 hrs after
the injection of IV contrast? - ✔✔Metformin is the generic of glucophage and damage
could be done to kidneys after the injection of IV iodinated contrast. There are many
combinations of drugs that have this medicine in them, they include avandamet
(avandia-metformin) metaglip (metformin-glipizide)
✔✔Which of the following will most likely remove a ring artifact? - ✔✔The ring artifact is
one of the more common equipment artifacts found in CT. This is a result of a faulty or
miscalibrated detector element.
✔✔The appearance of a cone beam artifact may look like stars - ✔✔Coming from
structures around the edge of the image---Cone beam artifacts result from multi-row
detector scanners when the x-ray beam is divided over multiple slices and is more than
20mm thick. Cone beam artifacts appear around the edges of the image like spokes or
stars emanating out. A special cone beam algorithm is used to eliminate this effect.
✔✔The appearance of a circle or ring on the CT image is usually caused by anatomy
extending outside the scan FOV - ✔✔Tube arcing manifests in several ways, adding
noise to the image, creating a bad streak artifact and can cause the scan to abort. A
circle or ring is caused by a faulty detector element. Shading and inaccurate CT
numbers is caused from anatomy extending outside the scan FOV. Star-like artifacts on
structures at the edges of the images may be a cone beam artifact.
✔✔Which of the following scan parameters will produce a CT image with the least
amount of edge gradient artifacts? - ✔✔Thin slices and the use of more projections will
result in a decrease in edge gradient artifacts.
✔✔A normal gfr value is greater than 60? - ✔✔True
✔✔If the filter at the aperture of the x-ray tube removed even more low energy x-ray
photons which of the following would result? - ✔✔Removing more of the low energy x-
ray photons results in a higher energy in the incident x-ray beam. This will decrease the
amount of beam hardening artifacts due to the removal of the low energy x-ray photons.
✔✔The greatest amount of partial volume artifact would be displayed in which of the
following?
A. 5mm slice width used in a 20 slice study
QUESTIONS AND ANSWERS SURE A+
✔✔A CT scanner with a limiting resolution of 15 lp/cm can resolve an object as small as
- ✔✔The minimum object size that a CT scanner can resolve may be calculated by
taking the reciprocal value of the scanner's limiting resolution. The reciprocal of 15 lp/cm
is 1/15 lp/cm. This is equivalent to 10/15 lp/cm, which equals 0.6 mm/lp. Because a line
pair (lp) is equivalent to a line and space adjacent to it, this value may be divided in half
to provide the minimum object that this scanner can resolve: 0.3
✔✔By CT criteria, a solitary pulmonary nodule may be defined as a focal area of
increased density in the lung that is smaller than - ✔✔Solitary pulmonary nodules are
typically ovid focal areas of increased density that are less than 3 cm in diameter. Any
lesion larger than 3 cm is reffered to as a focal mass, with an increase propensity for
malignancy.
✔✔Evaluation of the venous vascular structures of the brain is known as - ✔✔CT
Venography (CTV) of the brain is a cariation of the CTA technique whereby the timing of
data acquisition is optimized for the period of peak venous opacification
✔✔sampling frequency? - ✔✔The sampling frequency, or views per rotaion (VPM),
controls the volume of transmission data acquired for each gantry rotation. Very small
objects exhibit high spatial frequencies that only systems with high sampling rates will
be capable of resolving.
✔✔After initiation of rapid bolus administration of an iodinated contrast agent, the
excretory phase of renal contrast enhancement occurs at approximately - ✔✔3-5
minutes..The excretory phase is a delayed-imaging phase that begins approximately 3
minutes after the initiation of contrast agent administration. During this phase, contrast
material has been excreted into the real calyces, opacifying the renal pelvis and the
remainder of the urinary collecting system (ureters, bladder). The excretory phase best
demonstrates the filling defects and potential lesions involving the urothelium, such as
those from transitional cell carcinoma (TCC)
✔✔The Propensity of a contrast agent to cause fluid to move from the extravascular
space to the intravascular space is called - ✔✔Osmolality
An important characteristic of iodinated radiopaque contrast media, osmolality describes
the propensity of the agent to cause fluid from outside the blood vessel (extravascular
space) to move into the bloodstream (intravascular space)
✔✔For Ct exams of the pelvis.. which types of contrast should be used? - ✔✔IV
contrast
low dense barium sulfate
,During CT examination of the pelvis, both intravenous and oral contrast agents are
commonly administered. An intravenous contrast agent is important in differentiating
pelvis blood vessels for lymph nodes. An oral contrast agent serves to opacify the small
and large colon and greatly improves their visualization. Oil-based contrast media are
not commonly used for CT procedures.
✔✔The water-soluble oral contrast agents used for CT scans of the abdomen and
pelvis should contain approximately__________ iodine - ✔✔A solution of 2%-5%
iodinated water-soluble contrast agent and water provides sufficient bowel opacification
for CT studies of the abdomen and pelvis. Some institutions may use a flavoring agent
to the solution or used a flavored contrast for ease of consumption. Common water-
soluble contrast media include gastrografin and hypaque.
✔✔The vertebral level at which the adult spinal cord ends is - ✔✔The adult spinal cord
ends between L1 and L2
✔✔An enema containing positive contrast material administered into the large bowel is
needed prior to the CT examination of the pelvis. Of the following, which is a sufficient
dose to opacify the rectosigmoid area of the colon? - ✔✔To opacify the rectosigmoid
region, a dose of 150-250 mL is sufficient. To opacify the complete large bowel a dose
of 300 - 500 mL is needed.
✔✔Prothrombin measures the amount of time necessary for a person's blood to
coagulate. - ✔✔10 to 14 seconds are within normal range
✔✔A CT scan of the pelvis resulted in a dose at the entrance to the patient's skin of 6
rads, the dose at the center of the patient will be _____ mGy, if it is two-thirds less than
the skin dose. - ✔✔The skin dose of 6 rads - 4 rads = 2 rads( 1 Gy = 100 rads)
✔✔A given CT exam yields a CTDI of 4.5 rads, with a slice thickness of 10mm, and a
2mm gap between slices, the MSAD for this exam is ________ rads. - ✔✔The MSAD is
equal to the CTDI X the ratio of the slice thickness to the table increment. With a 2mm
gap and a 10mm slice the table increment will be 12mm. The MSAD = (4.5 rads) X
(10mm/12mm)
✔✔What is the average range for activated partial thromboplastin time? - ✔✔The partial
thromboplastin time is a measure of blood-clotting ability. The range is given in an
average due to the variations in individual laboratory practices. The acceptable range is
between 28-34 seconds.
✔✔The job of the array processor is - ✔✔reconstruction of the projected attenuation raw
data into CT images
,✔✔To provide the largest image for the viewer on a 14 X 17 inch film, which of the
following CT film formats should be used? - ✔✔The arrangement of CT images on a
sheet of x-ray film will determine the size of the image for viewing. A 4:1 format stores
four large images on one single 14 X 17 sheet. The more images on one sheet the
smaller the image for viewing.
✔✔The major disadvantage of the early back-projection method of image reconstruction
is the appearance of the - ✔✔The star artifact resulted from the back-projection method
of image reconstruction used in older CT scanners. The artifact is removed by the use
of a convolution filter found in the filtered back-projection method used today.
✔✔When describing tube interscan delay time, which of the following are true?
1. The time required for the tube to rotate 360 degrees around the patient.
2. The time between the end of one scan and the start of the next scan, allowing the
tube to cool.
3. The time necessary for the production of photons to begin after applying the voltage
to the tube. - ✔✔1 only
✔✔Star-like artifacts on structrues at the edges of the CT images may be the result of a
cone beam artifact - ✔✔True
✔✔Where is the begining and endpoint of a CT routine chest? - ✔✔Lung Cancer
ussually metastisizes to the adrenal glands. Soft tissue windows should be through the
adrenal glands and lung windows can be only from above apices to the bottom of the
lungs.
✔✔The cause of the cupping artifact is? - ✔✔The low energy photons are attenuated
when they pass through the body resulting in the central tissues appearing darker in
signal intensity than the peripheral tissues. This phenomenon is sometimes called
cupping due to beam hardening on the image resulting in the contour of a cup
appearance.
✔✔Lung window? - ✔✔1400-1600 WW
-400-(-)600
✔✔Water soluble based oral contrast (gastroview) should not be used when? -
✔✔esophogeal perforation is suspected- This type of contrast should be used with this
diagnosis barium should not be used
✔✔As slice thickness is decreased, which of the following statements is true? - ✔✔A
decrease in both partial volume artifacts and edge gradient artifacts.
, ✔✔The edge gradiant effect is reduced by using a CT scanner with a small detector
aperture and thin slices - ✔✔True..Smaller apertures and thinner slices improve the
severity of edge gradiant effect. Greater data sampling rates would improve the edge
gradiant effect also.
✔✔Which of the following diabetic medications should be discontinued for 48 hrs after
the injection of IV contrast? - ✔✔Metformin is the generic of glucophage and damage
could be done to kidneys after the injection of IV iodinated contrast. There are many
combinations of drugs that have this medicine in them, they include avandamet
(avandia-metformin) metaglip (metformin-glipizide)
✔✔Which of the following will most likely remove a ring artifact? - ✔✔The ring artifact is
one of the more common equipment artifacts found in CT. This is a result of a faulty or
miscalibrated detector element.
✔✔The appearance of a cone beam artifact may look like stars - ✔✔Coming from
structures around the edge of the image---Cone beam artifacts result from multi-row
detector scanners when the x-ray beam is divided over multiple slices and is more than
20mm thick. Cone beam artifacts appear around the edges of the image like spokes or
stars emanating out. A special cone beam algorithm is used to eliminate this effect.
✔✔The appearance of a circle or ring on the CT image is usually caused by anatomy
extending outside the scan FOV - ✔✔Tube arcing manifests in several ways, adding
noise to the image, creating a bad streak artifact and can cause the scan to abort. A
circle or ring is caused by a faulty detector element. Shading and inaccurate CT
numbers is caused from anatomy extending outside the scan FOV. Star-like artifacts on
structures at the edges of the images may be a cone beam artifact.
✔✔Which of the following scan parameters will produce a CT image with the least
amount of edge gradient artifacts? - ✔✔Thin slices and the use of more projections will
result in a decrease in edge gradient artifacts.
✔✔A normal gfr value is greater than 60? - ✔✔True
✔✔If the filter at the aperture of the x-ray tube removed even more low energy x-ray
photons which of the following would result? - ✔✔Removing more of the low energy x-
ray photons results in a higher energy in the incident x-ray beam. This will decrease the
amount of beam hardening artifacts due to the removal of the low energy x-ray photons.
✔✔The greatest amount of partial volume artifact would be displayed in which of the
following?
A. 5mm slice width used in a 20 slice study
