CT Image Production

Calculate the pitch for a scan using the following variable. Acquisition thickness = 1 mm Beam Width = 10 mm Rotation time = .5 seconds Tube Current = 300 mA Table Movement = 8 mm

.8 (table movement / beam width)

Which of the following detector configurations has the most total beam coverage?

3mm x 7 rows

Which data acquisition technique produces a three dimensional volume of anatomical data?

ALl data acquisition techniques produce a volume of data

Ideally, the patient worklist on imaging equipment should be automatically populated from examination requests placed through the:

DICOM

The contrast resolution of a CT system is recorded with which units?

HU

Consider a PACS network running through a traditional internet network. What is the primary advantage of this network architecture?

If the internet is down, images can still be sent to PACS reading stations

A PACS network is used to connect which three?

Imaging equipment PACS equipment radiologist reading stations

information within the DFOV is used for what three functions?

MPR Long term storage in the archive servers radiologist interpretation

A radiography department uses a shared computer for EMR access that does not require a passcode for sign in. Is this a HIPAA violation?

THIS IS A HIPAA VIOLATION

When considering the following variables, which statement describes how the resulting views comprise the scan data? Pitch = 1 Acquisition thickness = 1.5 mm Rotation time = 1 second Maximum tube current = 300 mA

There will be no overlap or missing views in the scan data

A tech reviews a tech's EMR for evidence of gadolinium allergy prior to performing a scan with contrast. Is this a HIPAA violation?

This is NOT a HIPAA violation

An ortho surgeon needs to review 3Ds of a femur fracture. Which rendering technique will offer a 3D view of the bone without the need to process the entire data set?

Volume rendering

What QC test in CT creates a graph of attenuation coefficients with the CT number produced during scan?

accuracy

Some pathologies of the chest maybe visualized by rendering a multi planar reformation as minimum intensity projections. In a minimum intensity projection, what CT number will be displayed for a voxel that contains portions of lung air and a contrast filled artery?

air

Which part of the PACA system houses all the historic digital image data along with the current digital data generated by the modalities?

archive server

What error causes partial volume averaging?

averaging multiple tissue types into one voxel

Pitch is an acquisition variable defined for which acquisition mode?

axial

Which of the following CT scanning methods is also called sequential scanning?

axial

What data process is used to smooth or sharpen image data for a better visualization of the desired anatomy?

back projection

Which of the following CT artifacts is caused by a significant increase in average energy of the xray beam?

beam hardening

detector rows x acquisition thickness

beam width

Which two types of reconstruction algorithm should be used to view bony injuries to the thorax? standard smoothing bone edge-enhancing

bone edge enhancing

Assuming that all factors remain constant, which reconstruction algorithm expected to result in the most image noise?

bone algorithm

Adjusting the window level of a CT image will affect what two of the following? brightness of the displayed image contrast of the displayed image center point of hounsfield values in the displayed image total number of hounsfield values in the displayed image

brightness and contrast

Reconstruction of raw data into image data occurs within which component of the computer tomography system?

computer system

Compared to a soft tissue algorithm, a bone algorithm will have more

contrast sharpness

The purpose of the detector array in computed tomography is to:

convert electrical signals into raw data

Which of the following is a disadvantage of accessing the PACS server through the internet on on a basic desktop computer?

decreased image quality

What are three potential benefits of increasing the CT acquisition thickness from 1 mm to 2 mm?

decreased patient dose increased spatial resolution increased beam coverage

Compared to a pitch of 1, a pitch of 1.137 will have 1. decreased scan time 2. decreased rotation time 3. decreased spatial resolution 4. decreased noise 5. decreased patient dose

decreased scan time decreased pt dose decreased spatial resolution

What is the main disadvantage of using thick detector rows?

decreased spatial resolution

What is the function of output devices in a computed tomography imaging system?

display and store image data

contrast resolution is defined as the ability to

distinguish between parts with similar physical densities

which body section is best demonstratd with a window width of 2500 and a window level of 600

facial BONES

Which computed tomography scanning technique collects scan data while the patient table is in motion?

helical

Consider a CT image that was initially displayed with a 300 WW and a 30 WL. DECREASING the WL from 30 to 0 will have what effect on the image?

increased brightness

Compared to a pitch of 1.2, a pitch of 1 will result in 1. Increased dose 2. increased spatial resolution 3. increased total scan time 4. increased image noise

increased dose increased spatial resolution

Which two variable changes are expected to improve the contrast resolution of CT scan?

increased kVp increased mA

Which procedural change will increase the potential spatial resolution in a CT image? increased detector size increased pitch increased reconstruction thickness increased matrix size

increased matrix size

One advantage of using a small reconstruction slice thickness is:

increased spatial resolution

Compared to a 2mm reconstruction slice thickness a 1mm slice thickness will result in 1. decreased image noise 2. decreased spatial resolution 3. increased total image slices 4. increased spatial resolution

increased total image slices

During spiral scanning, attenuation data from the patient is first organized in a helical pattern. The process of converting this information into axial sections is accomplished through:

interpolation

What WC test in CT ensures that the numbers increase proportionally with increasing physical density?

linearity

A ROI indicating an average HU of - 697 most likely corresponds to which of the following? blood water lung bone

lung

What is the principle function of the data acquisition system (DAS) in computed tomography?

measure and convert transmitted radiation into an electrical signal

Ring artifact can be the result of

miscalibration of a detector element

aliasing artifact is caused by which three of the following:

missing projections fast pitch fast rotation time

If the pitch is greater than one, it results in:

missing views in the scan data

After completing a routine scan of the chest, the radiologist requests a sagittal image series with 5 mm slices. This request can be completed using which imaging technique?

multiplanar reformation

Increasing the rotation time may increase spatial resolution by increasing:

number of views used in each slice

table movement / beam width

pitch

what controls the physical size of the xray beam?

pre-patient collimators

after scanning a very large patient, the radiologist requests new images with decreased image noise.HOW?

reconstructing in thicker slices

When the display field of view is increased, the pixel size will

remain unaffected

Which of the following statements accurately describes the orientation of the y-axis in CT imaging?

represents data coordinates in terms of anterior and posterior extends longitudinally through the scanner

After performing a thoracic spine scan for trauma, the radiologist requests images to include the entire lumbar spine as well. The raw data is still saved on the CT scanner. This will require:

retrospectively reconstructing images with a different display field of view

measuring a pathology in the xaxis could be accomplished with which of these imaging planes?

sagital and axial

which of the following tow imaging planes would allow for measuring the dimensions of a pathology in the y axis

sagittal and axial

Raw data is also called

scan data

When creating a multiplanar reformation, which of the following parameters must be set by the tech:

slice interval slice thickness

CT imaging of the temporal bones often calls for a very low pitch (less than 1). One effect of using a pitch less than one is:

spatial resolution

a pt brought to the radiology department is experiencing kneww pain and is suspected of having a fracture of the tibial plateau. If the fracture line is very small, the visibility of the fracture might be limited by what characteristic of the CT scanner?

spatial resolution

half scan algorithms improve which image quality variable in CT?

temporal

Consider a voxel that includes these tissue types: lung, bone, fat and muscle. What CT number will be displayed by the pixel in the reconstructed image?

the average of all tissues will be displayed by the pixel

Matrix size in CT refers to:

the number of pixels in the matrix

Which two of the following statements correctly describe the process of data acquisition used in helical scanning?

the patient table is in constant motion the patient data is collected in one large spiral pattern

When reviewing a CT of the bony pelvis, the tech notices that the trabecular bone looks blurry. This is a quality control issue relating to:

uniformity

A new CT protocol calls of imaging the entire Circle of Willis in one X-ray exposure in one tube rotation. what scanning Mose would meet this requirement?

volume scanning

Which of the following increases cone beam artifact?

wide xray beam

The patient's anatomy that is saved as raw data in the computed tomography computed system includes any portion of the patient that is:

within the scan field of view

modifying the center of an axial image during Retro Recon requires changes to which two coordinates

x and y

changing the center of a coronal image requires changes to which two data coordinates

x and z

changing the slice thickness of a sagittal reformation changes the dimensions of the image data in what axis?

x axis

changing the slice thickness of a coronal reformation changes the dimenstions of the image data in what axis?

y axis