INTERVENTIONAL RADIOLOGY

Question 1

In DF, the spatial resolution is determined both

Answer 1

image matrix and by the size of the image intensifier

Question 2

Spatial resolution is limited by

Answer 2

pixel size

Question 3

A major change from conventional fluoroscopy to DF is the use of a ___ instead of a TV camera tube

Answer 3

charge-coupled device (CCD)

Question 4

Military applications ___

Answer 4

night vision scopes

Question 5

The sensitive component of a CCD is a layer of __.

Answer 5

Crystalline Silicon

Question 6

When this silicon is illuminated, ___ is generated, which is then sampled, pixel by pixel, and manipulated to produce a digital image.

Answer 6

electrical charge

Question 7

Spatial resolution of a CCD: determine by

Answer 7

its physical size and pixel count

Question 8

1024 matrix can produce images with __ spatial resolution.

Answer 8

10 lp/mm

Question 9

Television camera tubes: __

Answer 9

“pin cushion” or “barrel” artifact

Question 10

The CCD has greater sensitivity to

Answer 10

light

Question 11

Because of heated filaments and voltage differences, a very small electric current always is flowing in any circuit
This is called

Answer 11

background electronic noise

Question 12

The tube with a __ SNR provides five times the useful information and is more compatible with computer-assisted image enhancement

Answer 12

1000 : 1

Question 13

The __ from the image-intensified digital image receptor is transmitted to an analog-to digital converter (ADC)

Answer 13

output signal

Question 14

To be compatible with the computer, the __

Answer 14

ADC must have the same dynamic range as the DF system.

Question 15

An 8-bit ADC would convert the analog signal into values between __

Answer 15

0 and 255

Question 16

A 10-bit ADC would be more precise, with an ADC range from__

Answer 16

0 to 210 or 0 to 1023.

Question 17

The output of the ADC is then transferred to ___ and is manipulated so that a digital image in matrix form is stored.

Answer 17

main memory

Question 18

__ is amplified and is transmitted by cable to the television monitor, where it is transformed back into a visible image.

Answer 18

video signal

Question 19

television monitor forms

Answer 19

one end of a closed-circuit television system. The other end is the television camera tube or CCD.

Question 20

Two differences between closed-circuit television fluoroscopy and home television are

Answer 20

no audio and no channel selection

Question 21

Usually, the radiologic technologist manipulates only two controls:

Answer 21

contrast and brightness

Question 22

The principal advantages of DF examinations are the ___ that are possible and the enhanced visualization of vasculature that results from venous injection of contrast material

Answer 22

image subtraction techniques

Question 23

Refers to a number of computer-assisted techniques whereby an image obtained at one time is subtracted from an image obtained at a later time.

Answer 23

Temporal Subtraction

Question 24

Two methods are commonly used: the __ in temporal subtraction

Answer 24

a.) mask mode and the b.) time-interval difference (TID) mode

Question 25

results in successive subtraction images of contrast-filled vessels

Answer 25

Mask Mode

Question 26

Each image was obtained from a __ x-ray pulse. The time required for one video frame is __

Answer 26

33-ms; 33 ms

Question 27

Imaging sequence after acquisition of the mask can be ___

Answer 27

controlled manually or pre-programmed

Question 28

the use of later images as mask image.

Answer 28

Remasking

Question 29

Produces subtracted images from progressive masks and following frames

Answer 29

Time-Interval Difference Mode

Question 30

Occurs if patient motion occurs between the mask image and a subsequent image.

Answer 30

Misregistration artifact

Question 31

Same anatomy is not registered in the same pixel of the image matrix This type of artifact frequently can be eliminated by __ of the mask. Done by shifting the mask by one or more pixels so that __ of images is again obtained

Answer 31

re-registration; superimposition

Question 32

Uses two different x-ray beams alternately. Images are results of differences in __

Answer 32

Energy Subtraction; photoelectric interaction

Question 33

When the incident x-ray energy is sufficient to overcome the K-shell electron binding energy of iodine, an abrupt and large increase in absorption occurs Graphically, this increase is known as the

Answer 33

K absorption edge.

Question 34

Other methods: FOR ENERGY SUBTRACTION

Answer 34

(1) Alternately pulsing the x-ray beam at 70 kVp and then 90 kVp and (2) Introducing dissimilar metal filters into the x-ray beam alternately on a flywheel

Question 35

Combining temporal and energy subtraction techniques

Answer 35

hybrid subtraction

Question 36

the components used in conventional fluoroscopy

Answer 36

X-ray source, image intensifier, TV camera, TV monitor

Question 37

___ is a digital x-ray imaging system that produces dynamic images obtained with an area x-ray beam. The difference between conventional fluoroscopy and DF is the __

Answer 37

Digital fluoroscopy (DF); nature of the image and the manner in which it is digitized

Question 38

Images from DF are obtained by pulsing the x-ray beam in a manner called

Answer 38

pulse progressive fluoroscopy

Question 39

During DF, the x-ray tube operates in the __

Answer 39

radiographic mode

Question 40

__ is required to produce a single video frame, x-ray exposures longer than this can result in unnecessary patient radiation doses. This is a theoretical limit, however, and longer exposures may be necessary to ensure low noise and good image quality

Answer 40

33 ms

Question 41

The time required for the x-ray tube to be switched on and reach selected levels of kilovolt peak (kVp) and mA is called

Answer 41

interogation time

Question 42

The time required for the x-ray tube to be switched off is the

Answer 42

extinction time

Question 43

DF systems must incorporate high-frequency generators with interrogation and extinction times of less than __

Answer 43

1 ms

Question 44

The fraction of time that the x-ray tube is energized is called

Answer 44

duty cycle

Question 45

When this silicon is illuminated, electrical charge is generated, which is then sampled, pixel by pixel, and manipulated to produce a __.

Answer 45

digital image

Question 46

The CCD is mounted on the __ and is coupled through fiberoptics or a lens system

Answer 46

output phosphor of the image-intensifier tube

Question 47

Advantages of Charge-Coupled Devices for Medical Imaging

Answer 47

High spatial resolution * High SNR * High DQE * No warm-up required * No lag or blooming * No spatial distortion * No maintenance * Unlimited life * Unaffected by magnetic fields * Linear response * Lower patient radiation dose

Question 48

Advantages of Flat Panel Image Receptors Over Charge-Coupled Device Image Intensifiers in Digital Fluoroscopy

Answer 48

* Distortion-free images * Constant image quality over the entire image * Improved contrast resolution over the entire image * High DQE (see Chapter 16) at all radiation dose levels * Rectangular image area coupled to similar image monitor * Unaffected by external magnetic fields

Question 49

__ is particularly helpful for digital subtraction angiography (DSA) and results in improved dynamic range and better contrast resolution.

Answer 49

linear response feature

Question 50

flat panel image receptor (FPIR). Such an image receptor is composed of

Answer 50

cesium iodide (CsI)/amorphous silicon (a-Si) pixels

Question 51

The __ is much smaller and lighter and is manipulated more easily than an image intensifier. The __ imaging suite provides easier patient manipulation and radiologist or technologist movement, and there are no radiographic cassettes.

Answer 51

FPIR

Question 52

The image intensifier is limited by__ from the center to the periphery of the circular image

Answer 52

nonuniform spatial resolution and contrast resolution

Question 53

The video system used in conventional fluoroscopy is usually a ___ system. Such a system is inadequate for DF.

Answer 53

525-line system

Question 54

It is similar to the noise (fog) on a radiograph in that it conveys no information and serves only to obscure the electronic signal and reduce image contrast.

Answer 54

background electronic noise

Question 55

The tube with a 1000:1 SNR provides __ the useful information and is more compatible with computer-assisted image enhancement

Answer 55

five times

Question 56

Important characteristics of a DF system that are computer controlled include the

Answer 56

image matrix size, the system dynamic range, and the image acquisition rate.

Question 57

The output signal from the image-intensified digital image receptor is transmitted to an __

Answer 57

Analog-to-Digital converter

Question 58

The dynamic range of each pixel, the number of pixels, and the method of storage determine the __ with which the image can be acquired, processed, and transferred to an output device.

Answer 58

speed

Question 59

DF provides better contrast resolution through __ of image subtraction

Answer 59

postprocessing

Question 60

__ mode produces subtracted images from progressive masks and following frames.

Answer 60

TID

Question 61

The probability of photoelectric absorption in all three decreases with increasing x-ray energy. At an energy of __

Answer 61

33 keV

Question 62

___ is a special application of DSA. A mask image is acquired and stored

Answer 62

roadmapping