ASRT 10 (STUDY!) Flashcards
The amount of the x-ray beam that will be scattered or absorbed from a monoenergetic beam per unit of material thickness is called the:
Linear attenuation coefficient.
The obstruction of the bowels caused by failure of peristalsis is called:
A. Ileus.
B. Intussusception.
C. Volvulus.
D. Crohn’s disease.
A. Ileus.
The number of views obtained by the CT system during data acquisition is the:
Sampling frequency.
For an oblique-axial MPR of the shoulder, the scan plane should be perpendicular to the:
Glenoid fossa.
The ability of the CT system to detect small differences between linear attenuation coefficients is called its:
Contrast resolution.
When there is no overlap between slices, the _________ equals the CTDI.
MSAD.
The evaluation of the _________ involves the positioning of several ROI measurements at different locations along the center & periphery of an image to determine if there are any significant value differences.
Spatial uniformity.
Planes that are oriented at right angles to each other are called:
Orthogonal.
What is the best window level & width to visualize the gray and white matter of the brain?
WL 35; WW 100.
The typical scan delay for a CT scan of the soft tissue neck is:
25 seconds following the 2nd injection of a split bolus.
How much contrast is typically used for a CT brain perfusion/
50 mL.
The typical scan range for a CTA of the chest to rule out a pulmonary embolism is from:
just below the lowest hemidiaphragm to the lung apices.
The approximate HU of blood is:
20.
A __________ detector array uses detectors of various sizes, with the thinnest in the center & wider detectors toward the edges.
Adaptive.
Tactile communication cues involves the use of ________ to impart meaning.
Touch.
All of the following are clinical indications for CTA of the CoW and carotids, EXCEPT:
A. acute stroke.
B. dural sinus thrombosis.
C. carotid atherostenosis.
D. carotid injury.
B. dural sinus thrombosis.
Dose measurements are calculated & reported by a physicist for each CT scanner, using the:
CTDI measurement.
A 16-slice MDCT system has access to ________ data channels.
16.
- In this case, the slice number equals data channels!
Automatic tube current modulation automatically adjusts the _________ based on the estimated attenuation of the pt at a specific location.
mA.
For cardiac calcium scoring, the scan field should be set:
from 1 cm below the carina to just below the heart apex.
True/False: MPRs can be 2D or 3D.
False - they can only be 2D images!
Normal range for BUN level is:
7-25 mg/dL.
The __________ is used to determine the radiation dose for a specific CT exam.
DLP.
Which of the following factors controls the temporal resolution of a CT system?
A. gantry rotation time.
B. ECG wave form synchronization.
C. kVp.
D. mA.
A. Gantry rotation time.
All of the following CT exams often use split bolus injections, EXCEPT:
A. maxillofacial CT.
B. CT of the orbits.
C. CT of the cervical spine.
D. CT of the neck.
C. CT of the cervical spine.
Choledocholithiasis is commonly called:
Bile duct stones.
Which of the following scan types has the highest image quality?
A. localizer scans.
B. step-and-shoot scans.
C. helical scans.
D. single-detector row scans.
B. step-and-shoot scans.
Which phase of kidney contrast enhancement begins about 3 minutes after the contrast bolus injection?
Excretory phase.
Which technique takes a series of low-radiation scans to monitor the progress of the contrast bolus & begins scanning when the contrast has reached a particular location?
Bolus Triggering.
A pencil ionization chamber is used to measure the:
CTDI.
The component of the computer system responsible for performing all of the major processing of the CT image is the:
Array processor.
Intrathecal injection of contrast media is frequently used for CT of the:
Spine.
Helical scan modes are possible because of the development of:
Slip ring technology.
The CT scanner generation is determined by:
The configuration of the x-ray tube to the detector.
What is a optimal window setting for imaging of the liver?
WW 150; WL 70.
Display monitors used for CT image evaluation have a dynamic range of about 8 bits & can display _________ individual shades of gray.
256.
When performing a post-stent scan of the abdominal aorta, the scan should be performed:
using bolus tracking, set to monitor at the level of the celiac artery.
All of the following contribute to risk for contrast induced nephropathy, EXCEPT:
A. history of diabetes.
B. history of CHF.
C. recent administration of a iodinated contrast agent.
D. history of cancer.
D. history of cancer.
All of the following are clinical indications for a high-resolution chest CT, EXCEPT:
A. lung nodule.
B. bronchiectasis.
C. interstitial disease.
D. asbestos exposure.
A. lung nodule.
All of the following are benefits of helical scanning compared to axial scanning, EXCEPT:
A. increased scan speed.
B. decreased respiratory and cardiac motion.
C. superior reformation capabilities.
D. optimal resolution.
D. optimal resolution.
The median pixel value of the displayed range is determined by the selected:
Window level.
All of the following are clinical indications for a CT of the base of the skull, EXCEPT:
A. thrombosis.
B. AVM.
C. brainstem tumor.
D. dementia.
D. dementia.
What type of medication can be administered prior to a cardiac CT to reduce heart rate?
Beta blockers.
According to the CDC, patients with a history of smoking and age _____ should be screened for lung cancer with a low dose CT screening.
50 and over.
The use of two separate x-ray tubes & detector arrays to create images of varying attenuation is called:
Dual-source CT.
All of the following are true of xenon gas detectors compared to solid-state crystal detectors, EXCEPT:
A. they are less expensive.
B. they are easier to calibrate.
C. they have higher absorption efficiency.
D. they are more stable.
C. they have higher absorption efficiency.
The radiosensitivity of a developing fetus is of greatest concern in what peroid?
During the 1st trimester.
The measure of radiation received by an individual detector is the:
Ray sum.
The electronic combination of signal from adjacent detectors is called:
Binning.
Which CT exam is often split into two groups to avoid scanning through metal dental work?
A. maxillofacial CT.
B. CT of the mandible.
C. CT of the neck.
D. CT of the cervical spine.
C. CT of the neck.
The technique of performing 3D reconstructions using thresholding to limit the displayed volumetric data is called the:
surface rendering.
All of the following techniques are used to reduce dose to the lens of the eyes during CT of the head, EXCEPT:
A. positioning the pt using the supraorbital meatal line instead of the orbital meatal line.
B. tilting the gantry during imaging.
C. using the axial (step-and-shoot) scan mod during imaging.
D. scanning the pt in the coronal plane.
D. scanning the pt in the coronal plane.
Why are children more radiosensitive than adults?
Children have more dividing cells than adults.
The 3-dimensional elements that make up CT images are called:
Voxels.
Why is it recommended that Metformin be discontinued 48 hours before and 48 hours after the administration of iodinated contrast media?
Metformin can put the pt at risk for lactic acidosis if renal failure occurs as a result of the contrast.
The pancreas usually extends in an oblique transverse angle with the head of the pancreas within the duodenal loop and the tail near the:
Spleen.
The technique called __________ is used in helical scanning to remove the slant & blur of the image.
Interpolation.
The __________ demonstrates as an oval, homogeneous soft tissue mass positioned between the bladder & rectum.
Uterus.
Compared to standard filtered back-projection methods, adaptive statistical iterative reconstruction (ASIR) can reduce pt dose by as much as:
50%.
The introduction of room air or CO2 through a small catheter is called:
Insufflation.
What window presentation is optimal for viewing an intracranial hemmorrhage?
WW 80; WL 30.
Which of the following 3D rendering techniques would be best for visualizing a tumor?
A. MIP.
B. SSD.
C. VR.
D. MinIP.
C. VR (Volume rendering).
Which data acquisition method is the most efficient in regard to radiation dose optimization?
Volumetric.
The renal pyramids are located in which part of the kidney?
Medulla.
In the cross-sectional anatomy of the upper extremity, which muscle is primarily responsible for forearm pronation?
Pronator teres
Which scanning protocol should be followed for an initial CT for a trauma pt with a suspected pelvis injury?
CT with IV contrast.
In a CT-guided biopsy procedure, the purpose of using a coaxial needle technique is to:
Allow multiple samples to be taken through a single puncture.
Temporal resolution in CT imaging refers to the ability of the system to;
Display objects that move quickly.
Attenuation is the process through which x-ray interactions with matter result in a reduction in:
Beam quantity.
What is the primary photon interaction that occurs during routine computed tomography (CT) imaging?
Compton scatter.
What imaging plane is typically preferred when scanning the temporomandibular joints using CT?
Sagittal.
What characteristic of iodinated CM gives it the ability to increase tissue discrimination in CT imaging?
Iodinated contrast media is radiopaque.
A pt with a severe facial trauma reveals a suspected mandibular fracture. What signs on the CT scan would most likely support this diagnosis?
Discontinuity in the mandibular cortex.
How should a technologist correct a CT image degraded by tube arcing artifact?
Re-scan the affected images with the same scan settings.
