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Fluoroscopy Arun Ganguly PhD (Rebecca Fahrig). A good quick reference resource: J. Wang, T. J. Blackburn, “The AAPM/RSNA Physics Tutorial for Residents X-ray Image Intensifiers for Fluoroscopy”, September 2000 RadioGraphics , 20, 1471-1477. Image Intensifiers. Image Intensifier.

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slide2

A good quick reference resource:

  • J. Wang, T. J. Blackburn, “The AAPM/RSNA Physics Tutorial for Residents X-ray Image Intensifiers for Fluoroscopy”, September 2000 RadioGraphics, 20, 1471-1477.
image intensifier
Image Intensifier

Electrostatic

lenses

anode

    • Brightness gain = electronic gain (also called ‘flux’ gain)
    • X minification gain
  • For each e- ~1000 light photons are created
  • For each light photon at input phosphor, output 50 or 100 light photons generated (depending on mode chosen)

electrons

output

fluorescent

screen

(fluorescent CsI)

ii resolution
II resolution

Note: x-axis is in lp/cm so divide by 10 to get lp/mm

ii artefacts
II Artefacts
  • Veiling glare
  • Lag
  • Pin cushion
  • Vignetting
  • S-distortion
dose noise trade off
Dose/Noise Trade-off
  • Automatic Brightness Control (ABC):
    • Photocell located between image intensifier and camera sends signals to x-ray tube to change mA for constant brightness in image on monitor
  • Automatic Gain Control (AGC):
    • Amplifier gain in TV electronics maintains video signal during the time it takes ABC to change x-ray tube output. Does not affect input exposure.
dose noise trade off9
Dose/Noise Trade-off
  • Automatic Exposure Control (AEC):
    • Using photo-timers the actual amount of radiation reaching the image receptor (input phosphor) is measured to allow consistent amount of x-rays to be incident
image quality based automatic exposure control
Image quality based automatic exposure control

Today's exposure control

tube voltage

Exposure parameters are

today highly correlated

Dependencies are defined on fixed points, where the behaviour suddenly changes

tube current

exposure time

prefilter

patient thickness

ii vs fpd
II vs FPD

II

FPD

II

FPD

ii vs fpd14
II vs FPD
  • FPD can have many different zoom mode (upto 5 in some cases)
  • Higher zoom does not change spatial resolution for FPD. For II, resolution increases with higher zoom
  • If zoom involves binning pixels then there is loss of resolution
  • In IIs, the input dose increases as FOV-1
the main dose to a fluoroscopist during a procedure is
The main dose to a fluoroscopist during a procedure is
  • Leakage from x-ray tube
  • Scatter from the x-ray tube
  • Scatter from the table
  • Scatter from the patient
  • Scatter from the image intensifier
answer
ANSWER:

D : Scatter from the patient

X-ray tubes are shielded to limit leakage radiation to a level below 0.87 mGy/h(100 mR/h) at 1m at maximum rated kVp. Leakage at fluroroscopic kV is typically very much less. Most of the scatter from x-ray tube components is absorbed by the shielding used for leakage. The table is designed not to attenuate the x-ray beam. This minimizes its scatter. The image intensifier is only illuminated by incident x-rays. The full intensity of the beam irradiates the patient and most scatter originates where the beam enters the patient.

slide19
The stage of image intensified fluoroscopy which determines the noise content of the image is the number of ---------------.
  • Electron produced at the photocathode
  • Light produced at the exit phosphor
  • Light absorbed in the photocathode
  • X-ray photons absorbed in the input phosphor
answer20
ANSWER:

D : X-ray photons absorbed in the input phosphor

The number of x-ray photons absorbed in the input phosphor. Beyond that stage the number of quanta is always greater

slide21
In a 15/23/30-cm image intensifier with automatic brightness control, the greatest patient input exposure rate will be for the
  • 15-cm mode
  • 23-cm mode
  • 30-cm mode
  • Depends on whether kV or mA is varied
answer22
ANSWER:

A : 15 cm

The greatest patient input exposure rate will be for smallest input size, 15 cm, since it has the smallest minification gain

slide23
Using a 25cm field of view II fluro system with video monitor used for GI studies will typically resolved
  • 1-2
  • 3-4
  • 5-6
  • 7-8
answer24
ANSWER:

A: 1-2 lp/mm

The overall resolution is limited mainly by the video system. The intensifier itself may have 3-4lp/mm resolution

slide25
If a flat panel can resolve 2.4lp/mm in the 20-cm mode, it will be able to resolved ----lp/mm in 40cm mode
  • 0.6
  • 1.2
  • 2.4
  • 4.8
answer26
ANSWER:

C: 2.4 lp/mm

The resolution of a flat-panel image intensifier does not generally change with input field size.

according to federal regulations the largest total does that can be received by the patient
According to federal regulations, the largest total does that can be received by the patient.
  • 50mGy
  • 100mGy
  • 200mGy
  • Not defined
answer28
ANSWER:

D: Not defined

Federal regulations limit the dose rate but not the total dose. It is however expected that ALARA be observed by the system operators.

which is true of solid state fluoroscopic image detectors flat panels
Which is true of solid-state fluoroscopic image detectors (flat panels)
  • A vacuum envelope is used to maintain electron focus
  • Approximately 40V is applied between the anode and cathode
  • CsI is used as an x-ray detector in both II and FPD
  • Increasing magnification (small FOV) always results in better spatial resulting
  • Increasing magnification (small FOV)
answer30
ANSWER:

c: CsI is used as an x-ray detector in both II and FPD

slide31
In the diagram of the image intensifier shown below, all of the numbered arrows represent photons, except:
  • I.
  • II.
  • III.
  • IV.
  • V.
answer32
ANSWER:

D : IV the photocathode converts visible light photons to electrons, which are accelerated and hit the output phosphor

slide33

Using a fluoroscope with automatic dose-rate control: Which one of the following configurations will result in the greatest skin dose-rate to the patient?

answer34
ANSWER:

D. Position D.

This position will result in the greatest skin dose-rate to the patient because it involves a thick patient, it is close to the x-ray tube, and it has a long tissue path due to angulation.

slide35

A patient is examined with an x-ray fluoroscope using auto brightness control. The source to skin distance, SSD=65 cm. The source to image intensifier distance SID=90 cm. The patient’s entrance air kerma rate (EAKr) is 20 mGy/min when the 14 cm FOV image intensifier is used & the x-ray beam is collimated to the full FOV. If the SID is increased to 120 cm without changing SSD, the EAKr:

  • Increased by a factor of approximately 2.6.
  • Increased by a factor of approximately 1.8.
  • Increased by a factor of approximately 1.3.
  • Is unaffected.
  • Decreases by a factor of approximately 1.3.
answer36
ANSWER:

Increased by a factor of approximately 1.8.

A constant dose rate is needed at the image intensifier at any SID. Increasing the SID requires an increased output from the X-ray tube. Using the inverse square law, the ratio is (120/90)2 = about 1.8.

slide37

Consider a fluoroscopy system with ABC & a dual FOV images intensifier capable of a 9” mode & a 4.5” mode. Which image intensifier mode will provide (A = 9” mode, B = 4.5” mode, C = neither)

  • Better spatial resolution
  • Larger area of patient imaged
  • Greater minification gain
  • Greater electronic (flux) gain
  • Greater quantum mottle
answer38
ANSWER:
  • B, 4.5” mode presents a magnified image
  • A, 9” mode has larger FOV
  • A
  • C, flux gain independent of mode (depends on voltage across II)
  • C, In 4.5” mode area being imaged is down by a factor of 4, but ABC increases exposure by factor of 4, therefore # x-ray photons/picture element remains unchanged.
slide39

A patient is examined with an auto brightness triple mode FOV, image intensifier x-ray fluoroscope. The patient’s entrance air kerma rate (EAKr) is 20 mGy/min when the 14 cm FOV is used & the x-ray beam is collimated to the full FOV. The patient’s EAKr:

Increases more than 30% when the FOV is decreased to 10 cm (full field collimation).

Increases more than 30% when the FOV is unchanged & the beam is collimated to 10 cmx10cm.

Is unaffected by FOV & collimation changes.

Decreases more than 30% when the FOV is unchanged & the beam is collimated to 10 cmx10 cm.

Decreases more than 30% when the FOV is decreased to 10 cm (full field collimation).

answer40
ANSWER:

Increases more than 30% when the FOV is decreased to 10 cm (full field collimation).

Decreasing the FOV decrease the geometric light amplification factor of the image intensifier. More radiation is therefore needed to produce the required output light level. Also, less scatter is produced (and reaches the image intensifier) when the beam is collimated. A small increase in EAKr is needed to offset this effect.

slide41

Assuming constant film density with a 35 mm cine fluoro system using automatic brightness control, indicate whether each of the following will:

  • Increase image quality
  • Increase patient dose
  • Both
  • neither

Change frame rate from 30 frames/s to 60 frames/s

Increase mA on x-ray tube with constant kVp.

Increase kVp with a constant mA.

Change lens aperture from f5.6 to f2.8 (i.e. increase lens aperture)

answer42
ANSWER:
  • B, doubling frame rate, double patient exposure
  • C, increased mA implies increased patient exposure & reduced image noise
  • D, increase kVp decrease image contrast as well as patient dose
  • D, increased lens aperture implies more light to camera, thus ABC will decrease mA’s accordingly, therefore, image noise will increase & patient dose will go down.
when an image intensifier is zoomed from the 12 in mode
When an image intensifier is zoomed from the 12-in. mode:
  • The system spatial resolution increases.
  • The patient’s skin dose increases.
  • The patient’s effective dose increases.
  • A, B, and C are true.
  • A and B are true.
answer44
ANSWER:

E. A and B are true.

A is true because a smaller input screen is focused on te same size output screen.

B is true because there is less minification gain in the 5-inch mode.

C is false: the dose-rate in the beam increases as the field-of-view decreases. The two effects offset each other; the same total number of x-ray photons is delivered to the patient. Therefore the effective dose is constant.

slide45
Rank the resolution of the following viewing modes using the same image intensifier from highest to lowest:
  • 35 mm cine
  • 525 line TV
  • Video cassette recorder
  • 100 mm film
  • 1025 line TV

1,2,3,4,5

5,4,1,2,3

4,1,5,2,3

1,4,3,5,2

4,5,1,2,3

answer46
ANSWER:

C. 100 mm has almost same resolution as II output phosphor, 35 mm slightly less. All TV images are much lower in resolution with the high line TV being best, VCR always degrades TV image.

the reason for over framing in cine filming is to
The reason for over-framing in cine filming is to:
  • Improve spatial resolution
  • Increase the field of view
  • Reduce patient dose
  • Change the shape of the cine image
  • Increase the framing rate
answer48
ANSWER:
  • Improve spatial resolution.
slide49
Which recording method used in conjunction with fluoroscopy has the lowest patient exposure per image?
  • Digital photospot
  • Spot film/par screen
  • 35 mm cine
  • spot film/rare earth screen
  • 100 mm photospot
answer50
ANSWER:

C. The approximate exposure to the input surface of the II for a 9” field of coverage is 15 µR for a 35 mm cine, 100 µR for a 100 mm photospot, 50 to 100 µR for a digital photospot, 1000 µR for a par 4 screen conventional spot, and 250 µR for a 400 speed rare earth system. Of course, the cine image is too small for routine imaging and a single frame is never taken.

on a frame by frame basis digital subtraction systems deliver times the cine dose
On a frame-by-frame basis, digital subtraction systems deliver ____times the cine dose.
  • 1/50 (very much less)
  • 1/2
  • 1 (the same)
  • 2
  • 50 (very much more)
answer52
ANSWER:

E. Digital subtraction systems usually require an entrance exposure of 1.0 mR/ frame where as cine requires only 20 to 40 µR/frame. However, many more frames (30 to 60 per second) are used for cine compared to digital radiography (about 1 per second).

slide53

If a fluoroscopic procedure delivers a patient entrance exposure of about 5 R/min, the scatter radiation at the table side 1 m from a large patient could be around:

  • 5 mR/hr
  • 50 mR/hr
  • 300 mR/hr
  • 100 µR/hr
  • None of the above
answer54
ANSWER:

C. Scatter at 1 m is about 0.1% (note units)

true or false concerning cineradiography
TRUE or FALSE – Concerning cineradiography:
  • The camera shutter is closed while the film is being transported between frames.
  • An automatic brightness control is used.
  • Patient expose rates are lower than fluoroscopy.
  • Total overframing results in lost film utilization.
slide57

The “effective” aperture on a II/TV/digital imaging chain is moved from an f 2.8 to an f 5.6 setting & adjustments are made to provide similar image gray scales values.

  • The input exposure required to obtain a given gray level in the digital image is reduced.
  • Approximately four times more exposure is required to achieve the same peak digital number.
  • Resultant quantum noise is now higher in the acquired image.
  • 1/2 the exposure can be used to achieve the same peak digital number values in each image.
  • The aperture has no effect on image noise.
answer58
ANSWER:

B. f/numbers are calibrated as the ratio of the focal length to lens diameter. Therefore, by increasing the f/number, the lens “speed” (light collection efficiency) is reduced & an increased exposure is required to compensate for the lowered light levels.

match the following imaging systems with their limiting spatial resolution
Match the following imaging systems with their limiting spatial resolution:
  • 400 speed film/screen
  • 35 mm cine film
  • Conventional fluoroscopy
  • MRI

0.3 line pair per mm

1.0 line pair per mm

3.5 line pair per mm

7.0 line pair per mm

in cardiac cine filming
In cardiac cine filming:
  • Spatial resolution is > 8 line pairs per mm.
  • Very large II’s are used.
  • Patient entrance skin exposures may be 30 µR per frame.
  • Images from the II are captured on 35 mm film
  • Typical frame rates are 5/s.
answer62
ANSWER:

D. 35 mm film is used at about 30 frames/s using small II sizes to improve resolution to about 3 line pairs per mm. The typical II exposure rate is about 30 µR per frame, which corresponds to a patient dose over 100 time higher.

true or false
TRUE or FALSE:
  • Exact framing utilizes the entire intensifier image.
  • Exact framing provides a magnified image.
  • Overframing records the whole II image.
  • Overframing provides superior spatial resolution.
match the following image receptor exposure per frame imaging modality
Match the following image receptor exposure per frame & imaging modality:
  • 400 speed screen/film
  • Regular fluoroscopy
  • 35 mm cineradiography
  • Photospot film

2 µR

25 µR

150 µR

300 µR

to perform cine studies a fluoroscopic system would require addition of all of the following except
To perform cine studies, a fluoroscopic system would require addition of all of the following EXCEPT:
  • X-ray tube voltages of 150 kVp
  • Grid-controlled x-ray tube
  • Synchronization circuit
  • Cine camera
  • optical distributor
answer68
ANSWER:

A. kVp requirements in fluoroscopy & cine are very similar (70-90 kVp) & primarily determined by patient penetration.

for the following examinations select the most appropriate image receptor
For the following examinations, select the most appropriate image receptor:
  • Double screen, long latitude double –emulsion film.
  • Cesium iodide scintillator, photocathode
  • Single screen, single-emulsion film
  • High-speed, high-contrast double screen, double-emulsion film
  • Cesium iodide scintillator, thin film transistor.
  • Mammography
  • Chest radiography
  • Digital radiography
  • Fluoroscopy
answer70
ANSWER:
  • C. Single screen, single-emulsion film. Mammography requires very high resolution with acceptable dose, i.e., one screen, one emulsion.
  • A. Double screen, long latitude double –emulsion film. Chest radiography, the most frequently performed clinical exam, requires acceptable dose & long latitude to see the wide range of attenuating structures encompassed.
  • E. Cesium iodide scintillator, thin film transistor. Flat panel digital radiography employs thin film transistor (TFT) arrays that convert light energy to an electric signal. The TFT is not very sensitive to x-rays, there fore, a scintillator such as CsI is used to convert x-ray energy to visible light, which then strikes the TFT detector.
  • B. Cesium iodide scintillator, photocathode. In fluoroscopy virtually all modern image intensifiers use cesium iodide for the input phosphor. CsI has the unique property of forming long, needle-like crystals, which function as light pipes, channeling the visible light emitted within the crystals to the photocathode with minimal lateral spread. As a result, CsI can be quite thick, resulting in high absorption efficiency, while still maintaining high resolution.
slide71

In order to reduce the radiation dose to both patients & personnel, a radiologist chooses to use the C-arm fluoroscopy unit in the lowest dose mode. The most significant effect on image quality is:

  • High contrast resolution increases.
  • High contrast resolution decreases.
  • Low contrast resolution increases.
  • Low contrast resolution decreases.
  • None of the above.
answer72
ANSWER:

Low contrast resolution decreases.

For smaller number of detected photons/mm2 the contrast-diameter curve for detectable objects moves away from the origin. The most significant effect is the inability to detect small objects with low contrast.

two modes of a multi mode image intensifier system are described as follows
Two modes of a multi-mode image intensifier system are described as follows:

What is the most likely input diameter size (in inches) of each?

answer74
ANSWER:

The 6 in. mode must have the higher resolution. The ratio of brightness gains equals the ratio of the magnification gains, which is the ratio of the input areas; (6x6)/(9x9) = 1:2.25

the major differences between fluoroscopy standard radiography include all of the following except
The major differences between fluoroscopy & standard radiography include all of the following except:
  • Focal spot size.
  • Spatial resolution.
  • Tube current.
  • Tube potential.
  • Source-to-skin distance.
answer76
ANSWER:

Tube potential.

The focal spots for fluoroscopy are typically 0.3 or 0.6 mm; those for standard radiography are usually 1.0 to 1.2 mm. The spatial resolution for fluoroscopy is usually limited by the TV system to 1.8 to 2.5 lp/mm, while radiography has resolutions of 4 to 8 lp/mm. The tube current for fluoroscopy is usually 1 to 3 mA in order to limit anode heating for long exposure times of 3 to 10 minutes; because of the short exposure times (less than 1 second) of radiography, tube currents of 200 to 800 mA can be used. Tube potentials are the same for both procedures. SSDs in fluoroscopy are usually 18 to 20 inches, while the SSDs for radiographs are typically about 25 inches (except for chest radiographs).

slide78
Which one of the following provides the best estimate of the maximum skin dose delivered during an interventional procedure?
  • The displayed dose at the interventional reference point.
  • The displayed KERMA area product (KAP).
  • The total fluoroscopic time used for the case.
  • The total number of DSA frames used for the case.
  • All of the above provide equally good estimates of total skin dose.
answer79
ANSWER:

A. The displayed dose at the interventional reference point.

The displayed dose at the interventional reference point is specified to be at or near the patient’s skin. This metric will overestimate skin dose if there is gantry motion during the procedure. The same KAP can be delivered using a low dose and a large field-of-view or a high dose & a small field-of-view. Fluoroscopic time does not take DSA or patient size into account. DSA does not take fluoroscopic time or patient size into account.

regarding flat panel detectors fpd which of the following is true
Regarding flat-panel detectors (FPD), which of the following is True?
  • Digital storage requirements for individual images are always greater than those required for images from an image intensifier.
  • Images are designed to be displayed on a flat-panel monitor.
  • The intrinsic radiation sensitivity is similar to that of an image intensifier.
  • The limiting spatial resolution changes with zoom mode in a manner that is similar to that of an image intensifier.
answer81
ANSWER:

C. The intrinsic radiation sensitivity is similar to that of an image intensifier.

Both systems use essentially the same CsI input screen. Digital storage requirements are determined by the digital image processor, not the image receptor. The images can be displayed using any detector technology that provides appropriate image quality. The resolution of the II is determined by its electron optics. The resolution of the FPD is determined by the construction of its pixels and the degree of pixel binning.

slide82
The interventional reference point [defined by the international electro technical commission (IEC)] is located _____.
  • At the entrance to the image intensifier.
  • At 15 cm from the isocenter toward the image receptor.
  • At the isocenter.
  • At 15 cm from the isocenter toward the x-ray tube.
  • At the port of the x-ray tube.
answer83
ANSWER:

D. At 15 cm from the isocenter toward the x-ray tube.

This is the default location as defined by the IEC.

slide84

Using a fluoroscope with automatic dose-rate control: Which one of the following configurations will result in the greatest skin dose-rate to the patient?

answer85
ANSWER:

D. Position D.

This position will result in the greatest skin dose-rate to the patient because it involves a thick patient, it is close to the x-ray tube, and it has a long tissue path due to angulation.

slide86
The maximum vertical resolution in lp/mm for a 23-cm input diameter image intensifier coupled to a 1024 line TV system is _____.
  • 0.8
  • 1.5
  • 2.2
  • 3.1
  • 4.0
answer87
ANSWER:

B. 1.5

Of the 1024 lines in a standard TV, only about 980 lines are used to actually form the image. It takes two lines to make a line pair, so there are 980/2 = 490 line pairs. However, small objects are generally not perfectly aligned between the TV lines, so the effective resolution is obtained by multiplying the Kell factor, which takes into account the random positioning of small objects in the TV field. The Kell factor is generally about 0.7, so the effective resolution is about 490 x 0.7 = 343 line pairs. For a 23-cm (230-mm) input, the resolution would be 343/230 = 1.5 lp/mm.

for the following radiographic procedures select the most appropriate techniques
For the following radiographic procedures, select the most appropriate techniques.
  • 110 kVp, 600 mA, 0.1 s, 35” SID
  • 29 kVp, 100 mA, 0.7 s, 24” SID
  • 135 kVp, 200 mA, 0.015 s, 72” SID
  • 60 kVp, 400 mA, 0.0075 s, 40” SID
  • 75 kVp, 100 mA, 0.15 s, 50” SID

PA chest.

Screen-film mammography.

Neuro magnification angiography.

Barium GI cassette spot film.

answer89
ANSWER:
  • C, 135 kVp, 200 mA, 0.015 s, 72” SID.Chest films are done at long SID in order to minimize magnification. High kVp is used in order to get wide latitude.
  • B, 29 kVp, 100 mA, 0.7 s, 24” SID.Mammography is done at very low kVp to maximize contrast.
  • E, 75 kVp, 100 mA, 0.15 s, 50” SID.Magnification requires a small focal spot, hence low (100) mA. If magnification is obtained by moving the film changer further away, the SID is increased to something greater than 40 inches.
  • A, 110 kVp, 600 mA, 0.1 s, 35” SID.Spot films are taken with the cassette at the II face which has a relatively short SID. High kVp and mA are required to penetrate the abdomen.
slide91

Match the following maximum permissible fluoroscopic tabletop exposure rate with the type of II exposure control system (under-table x-ray tube):

  • 5 mR/min
  • 10 mR/min
  • 5 R/min
  • 10 R/min
  • No limit
  • Manual control
  • Automatic brightness control
answer92
ANSWER:

Maximum legal limit for entrance skin exposure : 10 R/min

Manual Mode : high dose option typically 5 R/min, but typically have no dose limit

the dose to personnel from scattered radiation during a fluoroscopic procedure depends on
The dose to personnel from scattered radiation during a fluoroscopic procedure depends on ____.
  • kVp
  • mAs
  • Distance
  • Field size & patient thickness
  • All of the above
answer94
ANSWER:

E . All of the above

slide95

A 9-in. multi-mode image intensifier (II) is switched to the 6-in. mode. As a result, the image will be ____, & the automatic brightness control system (ABC) will ___the exposure to the II & the patient.

  • Magnified, decrease
  • Magnified, increase
  • Minified, increase
  • Magnified, not change
  • Minified, decrease
answer96
ANSWER:

B : magnified, with ABC increasing dose to the patient to maintain brightness at the output phosphor

slide97
For fluoroscopy performed in the 6-in. II mode & displayed on a 525 line TV monitor, spatial resolution is most limited by the ____.
  • Scatter from the patient
  • Grid
  • II tube
  • Optical system
  • TV system
answer98
ANSWER:

E . The TV camera provides ~ 1.7 lp/mm in this mode, while the input phosphor of the XRII is ~ 3-5 lp/mm

slide99

In a digital subtraction angiography (DSA) a plumbicon tube is used to obtain the video image. If the tube is driven at standard broadcast TV rates, it takes ____ µsec to scan one line.

  • 5.3
  • 31.7
  • 63.5
  • 90.1
answer100
ANSWER:

C. 63.5 s Standard broadcast rates : 30 frames/s with 525 lines per frame (every second line read, refresh rate of 60 fields/s)

slide101

A DICOM standard for cine specifies that the image matrix is 512x512 with a depth of 8 bits per pixel. You have the need to store high-speed, high-resolution DSA raw data (1024x1024x16 bits). The relative disk storage space needed to store an individual image for the latter is ____ times as large as the original.

  • 32
  • 16
  • 8
  • 4
  • 2
answer102
ANSWER:

C. 8 times larger

slide103

An imaging system is equipped with variable frame rate pulsed fluoroscopy in place of continuous fluoroscopy. The mAs is programmed to yield equivalent noise perception to the old system (no other changes are made). This system is used to observe the swallowing reflex. Which of the following is true?

  • The sharpness of the clinical images is unchanged.
  • The contrast of the clinical images is unchanged.
  • Pulsed video at 30 frames/second always results in less dose than continuous video.
  • Pulsed video never results in less dose than continuous video.
answer104
ANSWER:

Sharpness increases due to decrease in motion blurring.

B. The contrast of the clinical images is unchanged.

What happens to dose is unclear…

slide105
_____ is the persistence of an image on the fluoroscopic TV monitor. With motion, the image becomes blurred because of this persistence.
  • Lag
  • Vignetting
  • Flare
  • Veiling glare
  • Blooming
in cardiac catheter procedures all of the following changes would reduce the patient s dose except
In cardiac catheter procedures, all of the following changes would reduce the patient’s dose except:
  • Reducing the frame rate.
  • Increasing the f number of the lens.
  • Increasing the aperture of the lens.
  • Increasing the conversion gain of the II.
  • Increasing the source-to-image receptor distance (SID).
answer108
ANSWER:

B. Increasing the f-number of the lens decreases the light reaching the camera, therefore ABC increases dose to the patient

Note : Increasing SID requires increase in x-ray output to maintain same brightness at input, but if the patient moves back with the detector, then entrance dose stays the same

slide109

A flat panel digital radiographic detector has a square 20x20 cm image receptor field. The full field of the detector is coupled to a nominal 2048x2048 CCD array. The relative spatial resolution (expressed as line pairs per mm) when going from a 20x20 to a 10x10 field of view is ____.

  • Four times better
  • Twice as good
  • The same
  • Half as good
  • One forth as good
answer110
ANSWER:

C. The same

answer113
ANSWER:
  • mm Al
for quality assurance in diagnostic radiology match each test tool with the appropriate test
For quality assurance in diagnostic radiology, match each test tool with the appropriate test:
  • Focal spot size
  • mR/mAs
  • HVL
  • Light/x-ray congruence
  • Fluoroscopic resolution
  • Aluminum filters
  • Line pair or mesh pattern
  • Lead markers or coins
  • Ion chamber dosimeter
  • Slit camera
answer115
ANSWER:

C. HVL

E. Fluoroscopic resoluton

D. Light/x-ray congruence

B. mR/mAs

A. Focal spot size

the typical lead equivalent in lead aprons used in fluoroscopy rooms is about
The typical lead equivalent in lead aprons used in fluoroscopy rooms is about ____.

0.1 mm

0.5 mm

0.5 cm

1.0 cm

answer117
ANSWER:

0.5 mm

0.5 mm Pb will reduce the x-ray intensity by 95% to 99%, depending on the kVp.

slide118
The fluoroscopic operating factors displayed on a monitor are 120 kVp and 10 mA. Which of the following is true?
  • The skin entrance dose is unusually low.
  • The five-minute timer is broken.
  • The skin entrance dose is extremely high.
  • The display must be wrong.
  • The anti-scatter grid is not in the beam.
answer119
ANSWER:

C. The skin entrance dose is extremely high.

As the fluoroscopic beam is position over thick or denser areas of a patient, the penetration of x-rays decreases. The factors of 120 kVp and 10 mA indicate that the image intensifier is not receiving enough transmitted radiation through the patient. At such high technique factors the patient’s skin entrance exposure is extremely high. A broken timer will not affect the technique and a missing grid would tend to decrease the factors.