GE CT Features Flashcards
What is ASiR-V?
- Adaptive Statistical iterative Reconstruction
- A reconstruction technique that reduces image noise and streak artifact which thereby reduces the dose required for routine imaging.
- Prescribed in 10 percent increments for 10-100 percent.
What is MTF?
Modulation Transfer Function is a measure of how well an imaging system transfers an object’s contrast to an image and is made up of two components: resolution and contrast/modulation.
What is DLIR?
- Deep Learning Image Reconstruction
- Also referred to as True Fidelity
- Deep-learning based reconstruction method intended to produce cross-sectional images of the head and whole body by computer reconstruction of X-ray transmission data taken at different angles and planes.
- Intended for image reconstructions to remove noise from the image but with a desire for texture that is more consistent with Filter Back Projection image reconstruction.
- Can be set to low, medium or high
What is IQ Enhance?
- Reconstruction process that can be used to minimize helical artifacts
- Must be 0.625 or 1.25 slice thickness at an interval equal to or exactly one half slice thickness.
- Not compatible with Axial, Cine or cardiac scan types.
Why is properly centering the patient in the gantry important?
To allow the bowtie filters to deliver dose where it is needed and filter more where it is not. Improperly centered patients may be under or over exposed if table height is set too high or too low.
*Especially important when using SmartmA or the mA selected by the system may be inadequate or greater than required.
When is SmartmA not recommended?
When a larger patient must have the table position lower than desired to fit into gantry and patient is miscentered. Manual mA is recommended in these instances.
What is SmartmA?
- An automatic tube current modulation feature that makes the necessary mA adjustments much more accurately than those manually estimated for the patient, and can thereby achieve a more consistent image noise in spite of the wide range of patient size.
- Uses last scout performed and selected noise index setting to select mA ranges
- Adjusts exposure as tube rotates thus leading to mA modulation in the x, y and z-axes.
How does ASiR effect SmartmA?
Increasing the ASiR-V percentage in SmartmA lowers the mA value required to achieve the prescribed NI.
What are the three categories of inputs that SmartmA uses to select the mA values?
- Patient-dependent
- Scan technique
- Primary image reconstruction parameters
How does SmartmA receive the patient-dependent values to calculate the prescribed mA?
It receives the attenuation size and shape of the anatomy being scanned from the last scout performed.
List the Scan Techniques used by SmartmA to calculate prescribed mA.
- Scan type (axial, cine, helical, cardiac)
- kV
- SFOV
- Rotation time
- Detector Coverage (helical only)
- Standard or High-Definition mode
List the Primary image reconstruction parameters used by SmartmA to calculate the prescribed mA.
- Noise index
- Slice thickness
- ASiR-V percentage
- Reconstruction type (HD or non-HD kernel)
What is ODM?
A mode to reduce the tube current (mA) when the x-ray tube is in the anterior position relative to the patient.
*Apex head 100 degrees
*Apex body 150 degrees
*Ascend head 90 degrees
*Ascend body 180 degrees
What is the mA reduction rate for ODM in the Head, Small Head, Ped Head SFOV?
Up to 30% with a ??? degree mA reduction range.
What is the mA reduction rate for ODM in the Large Body, Medium Body, Small Body, Ped Body SFOV?
Up to 40% with a 150 degree mA reduction range.
What is Auto Prescription?
A profile-driven feature that automatically selects kV, pitch, rotation time and other scan settings based on patient size. Utilizes AP + Lateral calculated from scout images to select size based profile.
What are the two key areas that Auto Prescription enhances for the CT user and the patient experience?
- Balances dose and image quality across all patient sizes by selecting scan settings and optimizing noise index and dose based on patient size.
- Improves workflow by eliminating size-based protocolling and reducing scan time adjustments and variability.
Define Helical Full mode
- It is a recon mode that provides a thinner slice profile but requires 10-15% more mA than Plus mode with equal noise.
Define Helical Plus mode
- A recon mode with up to 20% wider slice profile than full, but requires 15-20% less mA with equal noise. Provides reduced image noise.
- Reduction of helical artifacts can be seen with Plus mode.
- Uses additional views of data to reconstruct an image.
-Exposure time increases slightly to ensure views are collected to reconstruct all image locations prescribed.
Auto Scan
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What is Noise Index?
The relative level of noise in the reconstructed image and is the primary SmartmA input parameter that controls the X-ray output and ultimately provides the tradeoff between the desired image quality and patient dose.
The Noise Index value will equal what?
Approximately the standard deviation in the central region of the image when a uniform phantom is scanned and reconstructed using the standard reconstruction algorithm.
What does a higher Noise Index mean?
The image will contain relatively more noise and will be obtained with lower mA, therefore lowering relative patient dose.
What does a lower Noise Index mean?
The images will contain relatively less noise and will be obtained with higher mA, leading to relatively higher patient dose.
