Acquisition and Post-Processing

Question 1

DQE

Answer 1

• stands for detective quantum efficiency
• high DQE produces images with little noise and good image quality

Question 2

Last Image Hold

Answer 2

• allows the last image taken to remain on the monitor for analysis without continuing to expose the patient to more radiation
• image remains on monitor until radiation activated again
• this reduces patient and operators dose

Question 3

Pulsed Fluoroscopy

Answer 3

• created to reduce patient dose while still maintaining high quality images by using higher mA
• dose is used so even though higher mA is used radiation is not being emitted constantly which reduces patient dose

Question 4

Frame Averaging

Answer 4

• sometimes called digital temporal filtering
• operation that reduces overall patient dose and image noise by averaging multiple image frames together
• reduces noise, les radiation needed to maintain image quality but objects must be slow moving or else lag will be noticeable

Question 5

Duty Cycle (Pulsed Fluoroscopy)

Answer 5

time in which the generator is energized (ex: tube is energized 100ms for every second = 10% duty cycle)

Question 5

Hybrid Subtraction

Answer 5

• combination of temporal and dual energy
• soft tissue subtracted by dual energy, bone subtracted by temporal

Question 6

Interrogation Time (Pulsed Fluoroscopy)

Answer 6

the amount of time required for the xray tube to be switched on and reach selected kV and mA

Question 6

Extinction Time (Pulsed Fluoroscopy)

Answer 6

time required for the xray tube to be switched off

Question 7

Digital Subtraction Angiography

Answer 7

feature that involves removing or subtracting background structures from an image so only contrast media filled structures remain

Question 8

Temporal Mask Subtraction

Answer 8

• an initial mask image of the still structures is taken, then contract is injected and another image is taken
• the computer combines the two images to make a subtracted image
• bone is fully subtracted so vessels are not super imposed by bone
• good contrast resolution
• misregistartion can occur if motion between the two image present, causes blurring

Question 8

Dual Energy Subtraction

Answer 8

• dual kVs are used and the difference in photoelectric and attenuation values from the different kVs are evaluated by the computer
• the bone or soft tissue is removed but the k-edge absorption of the contrast media remains
• motion artifacts reduced
• more flexible with image in post processing

Question 9

Roadmapping

Answer 9

• used to record an image with contrast tat can then be overlaid onto a live fluoro image so the vessel can be followed like a map
• guide wire or catheter will be black and the vessel with be white

Question 10

Image Restoration

Answer 10

• algorithm written for digital machines that corrects predictable image deviation issues like QM (in II fluoro it also will correct vignetting and distortion)
• enables dose reduction as it improves image acquisition ability and image quality

Question 11

Pixel Shifting

Answer 11

• DSA specific
• used when the patient moves slightly from the mask image to injection image
• allows user to move the mask image to correspond to patients movement
• corrects misregistartion artifacts

Question 11

Remasking

Answer 11

• DSA specific
• selecting another mask image in order to obtain there best subtracted image of the anatomy of interest
• helpful in removing any motion that may be present after the initial mask image

Question 12

View Tracing

Answer 12

• DSA specific
• combines the numerous frames into one image to demonstrate a completely filled contrast structure