Download Computed Tomography Review Questions With Solved Solutions and more Exams Advanced Education in PDF only on Docsity!
Computed Tomography Review Questions
With Solved Solutions
Which of the following best represents typical bone window settings? - ANSWER>>WW 1800, WL 400
beam pitch - ANSWER>>table feed per rotation / the total collimation
In an MSCT system, the detector array is composed of multiple rows of individual detector elements along the: - ANSWER>>z-axis
Detector configuration refers to _____. - ANSWER>>the number, length, and organization of the individual detector elements in an MSCT system.
Noncontiguous images are images acquired - ANSWER>>with an interval greater than the section width.
Beam collimation - ANSWER>>(Detector size) x (Desired # of exposed detectors)
CT images that have been reconstructed from a portion of the data acquisition process in the hopes of reducing patient motion artifacts are called: - ANSWER>>segmented images
As a solid-state CT detector measures transmitted radiation, it emits a proportional response in the form of a(n): - ANSWER>>analog system
During a CT scan, each sample of ray sum measurements made by the data acquisition system (DAS) is called a: - ANSWER>>view
Which of the following is not an iterative method of CT image reconstruction? - ANSWER>>Fourier transform
The iterative methods of CT image reconstruction include simultaneous reconstruction, ray-by-ray correction, and point-by-point correction. The Fourier transform method is an analytic method of CT image reconstruction.
Contiguous images are acquired - ANSWER>>with an interval the same as section width.
Isotropic//Overlapping images are acquired - ANSWER>>with a higher interval than the section width.
The z-axis refers to the ______ plane. - ANSWER>>axial
Which of the following is not a function of the DAS? - ANSWER>>Controlling the mA along the Z axis of the scan.
Thresholding - ANSWER>>allows the user to select the range of pixel values used in a 3-D CT reformation
What is the dimension of each pixel in the matrix of an image with the following parameters? FOV = 25.6 cm
Matrix = 512 mm ✕ 512 mm - ANSWER>>.5 mm or .05 cm
fov/matrix = pixel size 256/ 1 cm = 10 mm
Generators located within the gantry are which generation? - ANSWER>>high frequency
Modern CT scanners rely on ____ to process acquired data. - ANSWER>>minicomputers
What decreases contrast resolution? - ANSWER>>smaller pixel size
increased pixel size increases contrast resolution b/c a photon is more likely to interact with the pixel
The following formula is used to calculate the linear attenuation coefficient:
I = I0e-μxThe symbol "x" identifies: - ANSWER>>absorber thickness
The portion of the primary beam interacting with a single detector is known as a: - ANSWER>>ray
The term __________ describes the ability of a CT scanner to differentiate objects with minimal differences in attenuation coefficients. - ANSWER>>contrast resolution
The term __________ describes the ability of a CT scanner to differentiate objects with minimal differences in attenuation coefficients. - ANSWER>>Sensitivity and contrast resolution
Which of the following factors has no measurable effect on spatial resolution? - ANSWER>>kVp
Which of the following types of image noise can be most easily reduced by the CT technologist? - ANSWER>>Quantum noise
The ability of a CT scanner to image a small high-density object is controlled by the __________ of the scanner. - ANSWER>>spatial resolution
Which of the following quality control tests should be performed daily on a CT scanner?
- Check CT number calibration.
- Examine noise levels (standard deviation) of a water phantom.
- Test accuracy of laser localization device. - ANSWER>>1. Check CT number calibration.
- Examine noise levels (standard deviation) of a water phantom.
Which of the following technical adjustments would decrease the quantum noise of a CT image?
- Increase mAs.
- Decrease section width.
- Increase section width. - ANSWER>>1. Increase mAs.
- Increase section width.
Which of the following adjustments in technical factors will result in an increase in spatial resolution? - ANSWER>>Increase in sampling frequency
Which of the following is an enteral route of medication administration? - ANSWER>>sublingual
Enteral administration involves the mouth and alimentary canal, which includes oral, sublingual, buccal, and rectal.
A normal adult prothrombin time (PT) value should be in the range of: - ANSWER>>12- 15 seconds.
Solu-Cortef - ANSWER>>hydrocortisone
Nonionic contrast media - ANSWER>>less likely to to produce adverse side effects nonsalt chemical compounds iohexol/omnipaque, iopamidol/isovue, ioversol/optiray
iso-osmolar contrast media - ANSWER>>same osmolality as blood iodixanol/visipaque
Ionic contrast media - ANSWER>>salts consisting of sodium and/or meglumine iothalamate/conray, diatrizoate sodium/hypaque
comatose - ANSWER>>completely unresponsive to stimuli
Obtuned - ANSWER>>depressed level of conciousness, may not be easily aroused from a state of confusion
Lethargic - ANSWER>>appears drowsy but can be aroused
semi-comatose (stupor) - ANSWER>>near unresponsiveness
Stochastic effects - ANSWER>>Probability or frequency of the biologic response to radiation as a function of radiation dose. Disease incidence increases proportionally with dose, and there is no dose threshold.
Kerma - ANSWER>>quantity of energy deposited into a unit of mass, describes absorbed dose
Effective Dose - ANSWER>>Sv relative risk of exposure to radiation assigns weighting factors to different tissues based on tissue sensitivity.
Pitch is calculated by - ANSWER>>table feed per rotation / section width
Beam pitch is calculated by - ANSWER>>table feed per rotation / total collimation
Pixel dimension is calculated by - ANSWER>>DFOV (mm) / matrix size
Filtered back-projection - ANSWER>>________________ reduces the amount of streak or star-like artifacts observed when using the back-projection method during CT image reconstruction.
Simple cysts of the kidney have an attenuation value of ___. - ANSWER>>0 - +20 HU
After contrast media bolus, the arterial phase of the the hepatic system occurs at ______. - ANSWER>>25-35 sec
The abdominal aorta bifurcates at the level of _____. - ANSWER>>L
vacuum phenomenon - ANSWER>>accumulation of gas in intervertebral discs
For the CT Abdomen Pelvis, what is an accurate slice thickness interval for acquisition for 64 slice MDCT? - ANSWER>>2.5 mm
Advantages of a dual source scanner include - ANSWER>>1. increased scan speed
- reduced dose
Which of the following slice thicknesses is correct for a 64-slice CT Chest without contrast for suspected lung mass? - ANSWER>>1.25 mm
After the patient receives contrast, the CT technologist must document the ____________ in the patient's electronic medical record. - ANSWER>>injection site
Spatial resolution is affected by _______. - ANSWER>>display field of view (DFOV), matrix size, pixel size
During daily calibration, the phantom is scanned to ensure the CT numbers of different areas correctly correlate with each material. This test confirms __________ of the equipment. - ANSWER>>Linearity
For a CT Soft Tissue Neck exam, what can the CT Technologist adjust to reduce the effect of dental artifacts? - ANSWER>>Tilt the gantry away from the teeth
Ask the patient to remove items from their mouth, such as dentures, prior to the scan
Indications for a high-resolution CT (HRCT) scan include all of the following, except: - ANSWER>>pulmonary embolus
Shaded surface display is used to create 3D reformats of the maxillofacial region, including the: - ANSWER>>external surface of facial region.
A water phantom is used in _____________ testing to check for noise during daily calibration. - ANSWER>>Standard Deviation
Which of the following are symptoms of a mild allergic reaction? - ANSWER>>1. Hives
- Coughing
- Localized swelling of the face
What is another name for the late or delayed phase of the abdomen, which occurs several minutes after contrast injection? - ANSWER>>Equilibrium phase
Most modern CT scanners use __________ linear interpolation. - ANSWER>> degree
The dose length product (DLP) is: - ANSWER>>the scan length multiplied by the CTDI volume.
A CTA Chest scan to rule out a pulmonary embolism terminates at the: - ANSWER>>lung apices
Compared to single-detector row image acquisition, multidetector CT image acquisition provides: - ANSWER>>increased z-axis coverage per rotation of the gantry.
What type of dosimeter is used to measure CTDI? - ANSWER>>Pencil-beam Ionization Chamber
Appropriate shielding of the patient during a CT scan includes all of the following, except: - ANSWER>>placing a lead apron over the patient's gown before the scan.
For a 64-slice MDCT scanner, if the pitch is 1.375 and the detector width is 0.625 mm, how far does the table travel per rotation of the x-ray tube? - ANSWER>>55 mm
Pre-patient collimation in CT: - ANSWER>>restricts the x-ray beam.
Following intrathecal injection of contrast for a CT myelogram, the patient should: - ANSWER>>remain supine and be instructed to roll 1 to 2 times prior to scanning.
CT colonography requires: - ANSWER>>CO2 insufflation
Which of the following HU ranges is most likely for a maximum intensity projection (MIP)? - ANSWER>>+500 to +
Contrast resolution is improved by: - ANSWER>>doubling mAs
The Lambert-Beer equation compares the relationship between the intensity of the radiation and the: - ANSWER>>object's density
Beam hardening artifacts occur when _____________ x-rays are ______. - ANSWER>>low energy, absorbed
The right and left coronary arteries originate from the: - ANSWER>>ascending aorta
The data acquisition system measures the attenuated beam as it arrives at the detectors, providing a measurement called the: - ANSWER>>ray sum
A routine CT Chest on a 64 slice MDCT scanner uses: - ANSWER>>a scan delay of 35 sec
Isotropic imaging improves: - ANSWER>>spatial resolution
Which acquisition method is used when administering contrast during a CT Brain Perfusion study? - ANSWER>>cine
Which of the following contribute to noise on the CT image? - ANSWER>>Patient size and tube current
Effects of radiation exposure, such as cancers, which are not based on the amount of radiation received, are called: - ANSWER>>stochastic effects
What glomerular filtration rate (GFR) indicates normal renal function? - ANSWER>>< 60 mL/min
An infant that will receive sedation for a CT scan should: - ANSWER>>receive no solid food for 4-6 hours prior.
The weighted average of data measurements divided by the pitch is the: - ANSWER>> min
Which method of CT Cardiac Gating dramatically reduces patient dose? - ANSWER>>Prospective method
Using raw scan data to create an image while scanning is called: - ANSWER>>prospective reconstruction method
- ANSWER>>Introspective method
- ANSWER>>Iteration method
The most common malignant primary tumor of the skeletal system is: - ANSWER>>mulitiple myeloma.
Which lab value most accurately measures renal function? - ANSWER>>GFR
In the digital acquisition system (DAS), the component that converts the electrical signals from the detectors into data is the: - ANSWER>>analog to digital converter (ADC).
CTDIvol is calculated as: - ANSWER>>CTDIvol = CTDIw / pitch.
In multislice CT, collimation is achieved using: - ANSWER>>beam collimation
A 25 cm Scan Field of View, (SFOV), is considered: - ANSWER>>small
Exposure - ANSWER>>a measure of effective dose in a specific mass of air by x-rays.
The portal venous phase of liver enhancement typically occurs ________ after IV contrast injection. - ANSWER>>60-70 seconds
Which window width will optimally display soft tissue structures with varying densities, such as fat and muscle of the pelvis? - ANSWER>>
The normal range for INR (international normalized ratio) is: - ANSWER>>0.8 - 1.
Which of the following is a parenteral route of medication administration? - ANSWER>>Subcutaneous
parenteral route - ANSWER>>dispensation of medications via a needle into the skin layers
During back projection, _________ is/are projected onto the matrix. - ANSWER>>ray sum data
The two coronary arteries that originate on the aoric root are the: - ANSWER>>right coronary artery and the left main coronary artery.
What is the normal lab value range for a platelet count? - ANSWER>>150,000 - 400,000 mm³
A coronary artery calcium (CAC) score of 300 would be considered _______ on the Agatston scoring system. - ANSWER>>moderate
In CT soft tissue examinations with iodinated contrast media, the scan should be timed with: - ANSWER>>opacification of the arterial and venous vessels, as well as mucosa and pathologic tissue.
Slice thickness corresponds to which element of a voxel? - ANSWER>>depth
The normal lab value range for BUN is: - ANSWER>>7 mg/dL - 25 mg/dL.
The term for fatty infiltration of the liver is: - ANSWER>>steatosis.
On the Hounsfield unit scale, pure water is assigned to: - ANSWER>>
Which postprocessing techniques are routinely used for CT examinations of the cervical spine? - ANSWER>>MPR, MIP, 3DR
The normal lab value range for creatinine is: - ANSWER>>0.5 mg/dL - 1.5 mg/dL.
Temporal resolution can be improved with: - ANSWER>>increased scan speed.
Following a CT myelogram, the patient's head should be elevated _________ to reduce the chance of developing a severe headache. - ANSWER>>30 degrees
When using prospective gating to acquire images with minimal cardiac motion, imaging is triggered by the _______ of the ECG. - ANSWER>>R wave
The ______ data acquisition mode moves the bed through the CT gantry while the x-ray tube and detector array remain stationary. - ANSWER>>scout
scout - ANSWER>>bone algorithm
What is the beam pitch for a CT exam using a 16-slice MDCT system with a table feed per rotation of 30 mm and total collimation of 20 mm? - ANSWER>>1.
On an MDCT scanner, the beam pitch is equal to the table feed per rotation divided by the total collimation (total number of sections x section width). In this example, beam pitch is equal to 30 mm divided by 20 mm, or 1.5.
With all other factors remaining constant, which of the following would decrease a patient's radiation dose during a helical CT examination? - ANSWER>>Increasing pitch
The _________ corresponds to the longitudinal plane and determines the thickness of a cross-sectional axial slice. - ANSWER>>z-axis
The display field of view (DFOV) for a CT series can be changed by using: - ANSWER>>image data
What is the typical scan range for a CT soft tissue neck with contrast to evaluate for swollen glands? - ANSWER>>From the superior orbital rim through the lung apices.
In a CT examination of the spinal cord with contrast enhancement, the contrast is introduced in the: - ANSWER>>subarachnoid space
Which of the following techniques could be used to decrease beam-hardening artifact when scanning the posterior fossa? - ANSWER>>decrease slice thickness
A ______ multiplanar reformation (MPR) is best suited for tubular structures and is generated using data points chosen by the technologist. - ANSWER>>curved
A typical scan delay for a routine CT of the chest after injection of intravenous contrast is: - ANSWER>>35 sec
The amount of blood (in mL) that moves through 100g of brain tissue each minute is the: - ANSWER>>cerebral blood flow
The portion of the uterus that enhances brightest with iodinated contast media is the: - ANSWER>>myometrium
The data acquisition system is located: - ANSWER>>between the detectors and the computer
Filament size is directly related to: - ANSWER>>Slice thickness, mA selected, & Spatial resolution
The left ventricle of the heart corresponds to which level of the thoracic spine? - ANSWER>>T
A standard WW for brain tissue is ____. - ANSWER>>80-
What is a filtering technique in which the reformatted raw data are copied to create what looks like the OG data set? - ANSWER>>Convolution
Which of the following would not normally be used to give contrast with a power injector? - ANSWER>>Perma-cath
What is not an example of a kernal? - ANSWER>>interative algorithm
Cone bean artifacts only appear in ___ scanners - ANSWER>>multislice
Recommended slice thickness for a routine ct scan of the neck is ___ mm. - ANSWER>>2.5-3 mm.
What 3 veins empty into the portal vein? - ANSWER>>splenic, inferior mesenteric, superior mesenteric
When image data is acquired by a ct scanner, it goes through a process called _____. - ANSWER>>quantization.
Which of the following types of contrast media would pose the greatest risk to patients during a CTA procedure? - ANSWER>>iodixanol (Visipaque)
In-plane contact shields that are designed to protect radiosensitive organs during CT scans are made of: - ANSWER>>bismuth
To reduce the risk of step artifacts on CT images: - ANSWER>>use overlapping, thin sections
What parameter primarily controls the depth of a voxel? - ANSWER>>section width
The most proximal main branch of the right coronary artery (RCA) is the: - ANSWER>>conus artery
Which of the following is a suitable method to reduce metallic artifacts on a CT image? - ANSWER>>increase window width
On a 64-slice MDCT system with beam pitch set to 1.75 and a total collimation of 20 mm, how far will the table move per gantry rotation? - ANSWER>>35 cm
When performing a CT scan of the orbits in the axial plane, images should be acquired parallel to the: - ANSWER>>IOML
When performing an axial scan, the multiple scan average dose (MSAD) calculation should incorporate: - ANSWER>>image spacing
During a contrast exam, which of the following anatomical structures would most benefit from MIP post-processing? - ANSWER>>aorta
What pathological condition involves the accumulation of excess fluid inside the lungs due to obstruction of the pulmonary circulation? - ANSWER>>pulmonary edema
When using a bowtie filter, which of the following is critical to avoid undesired irregularities in a patient's radiation dose? - ANSWER>>Centering the patient in the gantry.
Which of the following dose measurements requires no overlap or gaps between slices?
What phase of liver enhancement is optimal for the evaluation of hypervascular lesions or tumors such as hepatocellular carcinoma (HCC)? - ANSWER>>arterial phase
The imaging plane used parallel to the foot's metatarsals is the: - ANSWER>>oblique axial
All of the following are considered central venous catheters, except: - ANSWER>>levin
Which of the following SFOV sizes would be the most suitable for a CT of the pelvis on an adult patient with a hypersthenic body habitus? - ANSWER>>Large (42 - 50 cm)
When a voxel contains more than one tissue type, the CT number for each tissue is averaged together creating a: - ANSWER>>partial voluming artifact
Which linear interpolation setting reduces the distance between the reference points that eliminate misregistration? - ANSWER>>
For bolus tracking during a CTA Brain/Neck, the region of interest (ROI) is placed in the:
Axial image acquisition is best suited for all of the following, except: - ANSWER>>extremity
The window width displayed on the axial image of a brain noncon is - ANSWER>>
Which of the following is an advantage of automatic CO2 insufflation for CT colonography? - ANSWER>>lower risk of perforation
Which of the following is used as the IV-administered radiopharmaceutical during a PET-CT hybrid examination? - ANSWER>>Fludeoxyglucose F 18 (FDG)
Which of the following improvements in CT chest imaging is a direct result of the advent of multidetector CT (MDCT)? - ANSWER>>1. Reduction in misregistration artifacts2. Increased examination speed
Which of the following oral contrast agents offers the best visualization of the enhancing GI wall on post-IV contrast CT examination? - ANSWER>>water
The period of peak enhancement of the renal cortex following rapid bolus injection of an iodinated contrast agent is termed the: - ANSWER>>corticomedullary phase
A common formula used to calculate dosage of intravenous iodinated contrast material in the pediatric patient is: - ANSWER>>1-2 mL per lb body weight.
After initiation of rapid bolus administration of an iodinated contrast agent, the equilibrium phase of hepatic contrast enhancement occurs at approximately: - ANSWER>>120-180 sec
An Agatston score of 250 on an MDCT cardiac examination for coronary artery calcification is rated as: - ANSWER>>moderate
The purpose of intravenous contrast agent administration during a CT study is to: - ANSWER>>1. Increase the contrast between adjacent structures
- Increase beam attenuation of enhanced structures
The normal range of cerebral blood volume (CBV) contained within 100 g of brain tissue is: - ANSWER>>4 to 5 mL/100 g.
The portion of the male reproductive system responsible for storage of the majority of mature sperm is the: - ANSWER>>vas deferens
The Stanford type B dissecting aneurysm affects which portion of the aorta? - ANSWER>>descending thoracic
An Agatston score of 5 on an MDCT cardiac examination for coronary artery calcification is rated as: - ANSWER>>minimal
Which of the following phases of contrast enhancement optimally demonstrates the relationship between pancreatic neoplasm and the surrounding vasculature? A. Pre-contrast B. Arterial phase C. Pancreatic phase D. Portal venous phase - ANSWER>>arterial phase
The period of peak hepatic parenchymal enhancement following rapid bolus injection of iodinated contrast is termed the: - ANSWER>>portal venous phase
Portal venous phase imaging of the liver is used to optimally demonstrate which of the following? - ANSWER>>Portal venous phase imaging is the phase during which hypovascular lesions are most conspicuous because of their density difference in comparison with the enhancing hepatic parenchyma.
Hepatocellular carcinoma (HCC), hepatic artery aneurysm, and focal nodular hyperplasia are all hypervascular in nature and would be best demonstrated on arterial phase imaging.
non-ionic contrast media - ANSWER>>Isovue/iopamidol, omnipaque/iohexol, optiray/ioversol
iso-osmolar contrast media - ANSWER>>Visipaque/iodixanol
