Subtraction techniques

Question 1

Subtraction of 2 or more digitized x-ray images that were acquired at diff times

Answer 1

Temporal subtraction

Question 2

Eliminates information in the image that was static

Answer 2

Subtraction image

Question 3

CM is introduced via the — to prevent any complications that may occur due to human error

Answer 3

power injector

Question 4

CM injected via venous vs arterial entry

Answer 4

Venous entry: 30ml-50 ml at 15-20ml/s
Arterial entry: 10ml-25ml at 10-12 ml/s

Question 5

XRT current is 20-100x the fluoroscopic mode & activation of a program of a pulse image acquidition

Answer 5

Mask Mode, Temporal subtraction

Question 6

Exposure is made 4-10 sec after injector is fired

Answer 6

Mask Mode, Temporal subtraction

Question 7

If initial mask image is inadequate due to pt motion/ improper technique

Answer 7

Remasking

Question 8

Unacceptable mask images can be caused by:

Answer 8

Noise
Motion
Technical factors

NoMoTe

Question 8

Produces subtracted images from progressive masks and following frames

Answer 8

TID mode, Temporal subtraction

Question 9

Relatively free of motion artifacts but less contrast

Answer 9

TID mode, Temporal subtraction

Question 10

Principally applied in cardiac monitoring

Answer 10

TID mode, Temporal subtraction

Question 11

Advantages:
1. works in rapid motion
2. shows dynamic blood flow
3. fewer motion errors

Answer 11

TID mode, Temporal subtraction

Question 12

If pt motion occurs between the mask image and the subsequent image

Answer 12

Misregistration

Question 13

System only selects 1 part of frame to register instead of realigning the whole image

Answer 13

ROI Registration

Question 14

To shift the mask by 1 or more pixels so as to align it again with the contrast iamge

Answer 14

Reregistration

Question 15

Use of 2 different XRBs alternately to provide a subtraction image that results from differences in photoelectric interaction

Answer 15

Energy subtraction technique

Question 16

Superior subtraction images in the detection of nodules, nodule calcification, and rib lesions

Answer 16

Energy subtraction technique, Strengths

Question 17

Margins of lesions may appear more distinct

Answer 17

Energy subtraction technique, Strengths

Question 18

Differentiation of calcified nodules from non-calcified nodules

Answer 18

Energy subtraction technique, Strengths

Question 19

Costly additional hardware

Answer 19

Energy subtraction technique, Weakness

Question 20

High radiation dose and does not allow lateral imaging

Answer 20

Energy subtraction technique, Weakness

Question 21

Poor SNR, increased quantum mottle

Answer 21

Energy subtraction technique, Problems encountered

Question 22

Decreased residual tissue contrast

Answer 22

Energy subtraction technique, Problems encountered

Question 23

Reduces soft tissue artifacts

Answer 23

Hybrid subtraction technique, Strengths

Question 24

Produces more enhanced image contrast

Answer 24

Hybrid subtraction technique, Strengths

Question 25

Requisite increase in x-ray dose by 30-60%

Answer 25

Hybrid subtraction technique, Weakness

Question 26

Reduction of SNR about half of the temporal subtraction

Answer 26

Hybrid subtraction technique, Problems encountered

Question 27

Total subtraction of common structures

Answer 27

Temporal subtraction technique

Question 28

Some residual bone may survive

Answer 28

Energy subtraction technique

Question 29

Eliminates residual bone and motion artifacts

Answer 29

Hybrid subtraction technique