ASRT Exam 2 Flashcards
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.
What are kernels?
Kernels are algorithms applied to the data to decrease noise or enhance certain aspects of the image.
Images are acquired along the _________ of the pt as they move through the scanner.
Z-axis (slice thickness).
The x-axis runs from _____ to _____ of the pt.
Side to side.
The y-axis runs what to the pt?
Anterior to posterior or posterior to anterior.
The target anode of the CT X-ray tube is usually made of:
Tungsten.
The basilar artery originates from what?
Originates when the vertebral arteries connect after entering the skull through the foremen magnum.
What is the WW for an axial brain/head?
100.
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.
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.
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.
To rule out a hip fracture, the coronal view of the hip should be aligned to the long axis of the :
Femoral neck.
Where does the azygos vein reside?
Directly anterior to the thoracic spine & slightly to the right of the thoracic aorta.
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).
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.
With overlapping slices of a MDCT scan, the multiple-scan average dose will:
Increase.
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.
Where does the transverse colon lie?
Runs horizontally in the upper abdomen directly inferior to the liver & the spleen and anterior to the kidneys.
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.
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).
MPR is used to reformat the data into:
Sagittal, coronal, transverse (axial), or oblique planes.
Gray (Gy) is the unit for measuring absorbed dose and:
Air kerma
Define air kerma
Defined as the kinetic energy released in the air and is measured in Gy.
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.
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.