2 xrays Flashcards by Coleen Jones

What is the main cause of attenuation in an x-ray beam?

A) Reflection
B) Refraction
C) Absorption and scattering
D) Diffraction

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Which of the following processes produces characteristic radiation in x-ray imaging?

A) Compton scatter
B) Photoelectric effect
C) Bremsstrahlung
D) Elastic scattering

none- characteristic is collisional interaction with innershell electron in the anode.
PE is in the patient

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What does the term “beam hardening” refer to in x-ray imaging?

A) Removal of high-energy photons from the beam
B) Removal of low-energy photons from the beam
C) Increasing the overall intensity of the beam
D) Increasing the number of photons in the beam

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Which of the following effects in x-ray production accounts for approximately 80% of the emitted radiation?

A) Photoelectric effect
B) Compton scatter
C) Bremsstrahlung
D) Fluorescence

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What happens to the energy of an electron as it undergoes bremsstrahlung radiation?

A) It gains energy
B) It loses energy
C) It remains unchanged
D) It is transformed into visible light

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What is the primary purpose of using an intensifying screen in x-ray imaging?

A) To increase patient exposure
B) To convert x-ray energy into visible light
C) To reduce film processing time
D) To focus the x-ray beam

Intensifying screens are used in the x-ray cassette to intensify the effect of each x-ray photon by producing a larger number of light photons. They decrease the mAs required to produce a particular density and hence decrease the patient dose significantly. They also reduce motion blur and x-ray tube loading by reducing exposure time.

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What is the primary effect of adding filtration to an x-ray beam?

A) Increases the number of photons
B) Decreases the effective energy of the beam
C) Removes low-energy photons and increases the beam’s effective energy
D) Reduces image contrast

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The linear attenuation coefficient (LAC) of a material is most dependent on which factor?

A) The wavelength of the radiation
B) The material’s density
C) The temperature of the material
D) The thickness of the material

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Which type of radiation occurs when an electron is deflected near the nucleus of an atom, losing kinetic energy in the form of a photon?

A) Compton scatter
B) Photoelectric effect
C) Bremsstrahlung
D) Rayleigh scattering

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Which of the following is a key characteristic of polychromatic radiation?

A) All photons have the same energy
B) It produces a spectrum of photon energies
C) It only consists of high-energy photons
D) It is monochromatic and highly filtered

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What is the role of the latent image in photographic film?

A) To convert photons into visible light
B) To represent the unprocessed image before development
C) To reduce the exposure time
D) To increase the number of silver halide grains

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Which of the following is wrong ?

A) The actual focal spot is determined by the anode angle

B) The effective focal length (spot size) increases with the anode angle.

C) The spatial resolution is improved when the effective focal spot is small

The actual focal spot is determined by the anode angle

FALSE. The actual focal spot is the physical area on the anode where the electron beam strikes. Its size is determined by factors such as the electron beam diameter and the design of the x‐ray tube—not by the anode angle.

B) The effective focal length (spot size) increases with the anode angle.

TRUE. Effective focal spot size=Actual focal spot size×sin(θ)This means that as the anode angle θ increases, sin(θ) increases, so the effective focal spot size increases

C) The spatial resolution is improved when the effective focal spot is small

TRUE. smaller effective focal spot produces less geometric unsharpness (penumbra) on the image, leading to better spatial resolution.

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What is the advantage of having a large focal spot on the anode ? (one wrong answer)

Allows greater tube output intensity

B) Allows short exposure times

C) There is no advantage.

Allows greater tube output intensity

A larger focal spot distributes the electron beam’s heat over a wider area on the anode. This helps to dissipate heat more effectively, allowing the tube to operate at higher currents (mA) and produce more X‐rays without overheating. Thus, greater tube output intensity is indeed an advantage.

B) Allows short exposure times

Short exposure times help reduce motion blur and improve image quality. This is also an advantage.

C) There is no advantage. FALSE. This statement is incorrect because, as explained, there are clear advantages to having a large focal spot in terms of heat management and enabling higher output and shorter exposure times.

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1) Which of the following statements correctly describes the anode heel effect?

A. X-ray intensity is greater on the cathode side of the tube due to absorption of some photons in the anode.
B. X-ray intensity is greater on the anode side due to the angle of the anode.
C. The anode heel effect causes more X-ray photons to be produced at the anode side of the tube.
D. The anode heel effect refers to uneven electron production at the filament.

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2) Reducing the anode angle…

A. Increases the effective focal spot
B. Reduces heat production in the anode
C. Increases the anode heel effect
D. Creates a larger x ray field

C. all others are opposite

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3) Added filtration to a polychromatic x ray beam (which is false)…

A. Reduce patient dose
B. Reduce the average energy
C. Shrinks the x ray spectrum
D. Reduces the overall output of x rays

B is false, it increases the average energy of the beam

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4) Which of the following is true regarding the effect of kVp and mAs modulation?

A. Increasing the mAs by 15% is the same as doubling the kVp
B. Increasing the mAs increases the number of electrons, as well as the average energy of the electrons
C. Increasing the kVp increases the average energy of the electrons, and therefore the energy of the x rays produced
D. Increasing the kVp improves image contrast in all scenarios, but has to be balanced with patient dose

C. (A is the opposite way round, B is true for kVp, mAs only increases quantity of electrons, D, increased kVp increases Compton scatter and reduces contrast)

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Q1: In an x-ray generator, the use of alternating current (AC) instead of direct current (DC) is essential because:
A) AC allows for continuous electron flow between cathode and anode
B) AC enables the use of transformers for voltage modulation
C) DC would produce higher energy x-ray beams
D) AC minimizes voltage ripple in high-frequency generators

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Q2: In an x-ray circuit, what determines the voltage transformation ratio in a step-up transformer?
A) The turns ratio between primary and secondary windings
B) The input power supplied to the circuit
C) The resistance of the transformer coil
D) The current flow in the secondary coil

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Q3: According to the transformer equation, if the primary coil has 200 turns and the secondary coil has 4000 turns, and the input voltage is 220V, what is the output voltage?
A) 2200V
B) 4400V
C) 5500V
D) 8800V

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Q4: What is the primary function of the filament circuit in an x-ray tube?
A) Control the energy of x-ray photons
B) Regulate the high-voltage supply to the anode
C) Generate and control the thermionic emission of electrons
D) Convert alternating current into direct current

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Q5: Which semiconductor material is most commonly used in solid-state rectifiers within x-ray generators?
A) Copper
B) Silicon
C) Tungsten
D) Molybdenum

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Q6: Compared to a single-phase generator, a three-phase generator improves x-ray production by:
A) Increasing the frequency of x-ray pulses per second
B) Reducing power consumption by the x-ray tube
C) Decreasing the efficiency of x-ray photon production
D) Increasing voltage ripple to enhance beam penetration

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Q7: In capacitor discharge x-ray generators, what limits their clinical application?
A) The continuous decay of voltage during exposure
B) Their inability to provide high-voltage output
C) Excessive heat production in the x-ray tube
D) The requirement of three-phase power input

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Q8: The falling load principle in x-ray generators is primarily used to: A) Maximize mA while maintaining the shortest exposure time possible B) Reduce the load on the anode by lowering the voltage output C) Increase the duration of x-ray exposure to optimize image contrast D) Maintain constant tube current throughout the exposure

Q9: In an automatic exposure control (AEC) system using an ionization chamber, what parameter is directly measured to terminate exposure? A) Voltage applied across the x-ray tube B) The electrical charge generated by ionized air molecules C) The number of x-ray photons emitted by the tube D) The density of the patient's anatomy

Q10: A single-phase x-ray generator with a 100% voltage ripple produces a beam with: A) The highest possible efficiency B) A continuous and uniform photon energy output C) Significant fluctuations in photon energy, reducing beam efficiency D) The same radiation output as a high-frequency generator

1. What causes the anode heel effect in X-ray tubes? A) Uneven electron distribution at the cathode B) Reflection of X-rays within the collimator C) Increased kVp during exposure D) X-ray beam attenuation by the target material

2. How does a decrease in the anode angle affect the anode heel effect? A) Reduces the anode heel effect by increasing focal spot size B) Increases the anode heel effect by decreasing the effective focal spot size C) Has no impact on the anode heel effect but increases heat dissipation D) Increases the intensity of the X-ray beam

3. An X-ray generator can produce 700 mA at 100 kVp for a 100 ms exposure. What is its power rating? A) 70 kW B) 7 kW C) 700 kW D) 7000 kW

4. According to regulatory requirements, the misalignment between the light field and X-ray field should not exceed which value? A) 1% of the Source-to-Image Distance (SID) B) 2% of the SID C) 5% of the SID D) 10% of the SID

5. Which of the following factors will decrease the maximum allowable exposure on a tube rating chart? A) Increasing the focal spot size B) Increasing the anode rotation speed C) Using a smaller anode disk diameter D) Using a larger anode angle

6. For an exposure of 120 kVp, 400 mA, and 0.2 seconds using a three-phase generator, what is the total heat unit (HU) deposition? A) 9,600 HU B) 12,960 HU C) 16,800 HU D) 24,000 HU

B | kvp x ma x s x correction factor for 3 phase gene (1.35)

7. During continuous fluoroscopy at 80 kVp and 3 mA, how much heat (HU) is generated per second? A) 80 HU B) 240 HU C) 800 HU D) 2400 HU

B | kvp x ma

8. Which type of X-ray accounts for the majority of radiation produced in an X-ray tube? A) Characteristic radiation B) Compton scattering C) Bremsstrahlung radiation D) Photoelectric effect

Which of the following materials is suitable for the interspace material in an X- ray grid? Lead Air Carbon fibre Caesium iodide

Which of the below is the main limiting factor of parallel grids as opposed to focussed grids? Grid cut-off Increased mAs required Increased patient dose Reduced contrast

A. B and C are true for both types of grids. Grids generally improve contrast by reducing scatter reaching the plate

3) The use of grids… Increases the probability of the photoelectric effect Reduces Compton scatter hitting the detector Increases bremsstrahlung interactions Reduces patient dose

B. It can’t alter the interactions that have already occurred, bremsstrahlung occurs in the anode, grids require an increased mAs so generally the dose to the patient is increased.

4) Without a grid a chest xray requires 85kVp and 0.8 mAs. You decide to use a focussed grid with a grid factor of 5. What settings will be required? 17kVp, 0.4mAs 425kVp, 4mAs 85kVp, 4mAs 17kVp, 0.8mAs

5) Which of the following anatomical areas would benefit from the air gap technique most? Canine carpus Feline carpus Canine skull Canine thorax

D, would it make the skull blurry?

6) Which of the following would you change to magnify an x ray image? Increase source to object distance Increase source to film distance Decrease source to object distance Decrease source to film distance

C, or b if the object stayed in the same place

7) What reaction happens at the fluorescent input screen and photocathode in an image intensifier as part of a fluoroscopy machine? Light photons> electrons Xrays>light photons>electrons Electrons>light photons Xrays>Electrons>light photons

Which factor most directly affects the spatial resolution of a digital image? a) Field of View (FOV) b) Number of pixels in the matrix c) Bits per pixel d) Image contrast

What is the recommended pixel matrix size for detecting objects smaller than 1 mm in fluoroscopic imaging with a 23 cm field of view? a) 256 x 256 b) 512 x 512 c) 1,024 x 1,024 d) 2,048 x 2,048

C nyquist limit, if you want to detect objects less than 1mm in size (say 0.5mm), then the pixel needs to be half that size to be sampled effectively

What happens if pixel size is larger than half the size of the smallest object to be detected? a) Image contrast improves b) Image resolution decreases c) File size decreases d) Image intensity increases

Which component is primarily responsible for image processing and 3D image calculations in modern computers? a) CPU b) RAM c) GPU d) LAN Adapter

5. What is the main advantage of increasing RAM in a computer system used for radiology imaging? a) Faster image rendering b) Improved network connectivity c) Reduced image contrast d) Increased storage capacity

Which of the following storage devices offers the fastest data access but lacks redundancy? a) RAID Level 0 b) RAID Level 1 c) Magnetic Tape d) DVD

7. Which image format is preferred for maintaining high-quality medical images without compression loss? a) JPEG b) TIFF c) PNG d) BMP

1. What is the key difference between indirect and direct digital radiography (DR) detectors? Indirect DR converts X-rays directly into an electrical charge, while direct DR converts them into light first. Indirect DR converts X-rays into light first, while direct DR converts them directly into an electrical charge. Indirect DR uses selenium, while direct DR uses caesium iodide. Indirect DR produces sharper images than direct DR.

2. What is the primary function of a Thin-Film-Transistor (TFT) array detector? a) Converts X-rays into visible light b) Stores and amplifies the signal as an electrical charge c) Directly converts X-rays into grayscale images d) Controls the intensity of the X-ray beam

3. What material is commonly used as the scintillator in indirect DR detectors? a) Amorphous selenium (a-Se) b) Silicon carbide c) Caesium iodide (CsI:TI) d) Lead oxide

4. Why does direct DR provide high spatial resolution? a) It eliminates light conversion, preventing lateral light spread. b) It uses a thicker CsI layer to improve detection efficiency. c) It scatters X-ray photons to sharpen the image. d) It allows for larger pixels to capture more detail.

5. Which of the following statements regarding Computed Radiography (CR) and X-ray luminescence is TRUE? a) The latent image in a CR plate is formed by the direct deposition of silver halide crystals. b) Europium (Eu²⁺) acts as a dopant in BaFBr phosphor and is oxidized to Eu³⁺ during X-ray exposure. c) During image readout, a blue laser beam stimulates trapped electrons to emit red light photons. d) The latent image in a CR plate is permanent and can be re-read multiple times without erasure

6. What does the Fill Factor represent in an indirect TFT detector? a) The total number of pixels in the detector b) The X-ray absorption efficiency of the scintillator c) The total area occupied by electronic components d) The ratio of the sensitive area to the total area of a pixel

7. What is a major drawback of CCD-based detectors compared to TFT detectors? a) They are less expensive to manufacture b) They have better radiation dose efficiency c) They do not require an optical system d) Optical minification causes light loss, increasing noise and reducing dose efficiency

D CCD-based detectors (Charge-Coupled Devices) require an optical coupling system (lenses or fiber optics) to transfer the light emitted from the scintillator to the CCD chip. During this optical minification, some of the light signal is lost. This light loss increases image noise and reduces dose efficiency (DQE — Detective Quantum Efficiency). In contrast, TFT (Thin Film Transistor) flat-panel detectors are directly coupled to the scintillator or photodiode layer, minimizing light loss and improving efficiency.

8. What is the main limitation of Digital Radiography (DR) when compared to film-screen radiography? a) Lower contrast resolution b) Lower spatial resolution c) Inability to digitally enhance images d) Inability to store images electronically

9. Which of the following statements about Detective Quantum Efficiency (DQE) is TRUE? a) A higher DQE means a higher radiation dose is required. b) DQE measures how efficiently a detector converts incident X-rays into an image signal. c) DQE is unrelated to image noise. d) A lower DQE leads to better image quality.

10. What type of noise occurs due to too few X-ray photons striking the detector? a) Quantum noise b) Electronic noise c) Structured noise d) Amplification noise

11. What does Modulation Transfer Function (MTF) measure? a) The system’s ability to convert X-rays into light b) The efficiency of X-ray absorption c) The ability to preserve contrast at different spatial frequencies d) The number of pixels in an image

12. Which statement about the H&D (Characteristic) curve is correct? a) It is a linear relationship between exposure and optical density b) It plots the log of relative exposure against optical density c) It shows that optical density remains constant regardless of exposure d) It is only relevant to digital radiography

13. What happens in the toe region of the H&D curve? a) High optical density, low transmittance b) Best contrast and anatomical detail c) Low optical density, high transmittance, minimal contrast d) Maximum image contrast is achieved

14. What does a steep characteristic curve indicate about the film's latitude? a) Wide latitude, suitable for thoracic radiographs b) Narrow latitude, high contrast, suitable for bone X-rays c) No effect on latitude, only exposure time d) Increased exposure requirements and poor contrast

what three things are needed for magnification radiography? a) large focal spot b) small focal spot c) increased subject to film distance d) decreased subject to film distance e) decreased source to receptor distance/ or source to object difference f) increased source to receptor distance/ or source to object difference

B C E

Which of the following is wrong ? A) The actual focal spot is determined by the anode angle B) The effective focal length (spot size) increases with the anode angle. C) The spatial resolution is improved when the effective focal spot is small

A The actual focal spot is the physical area on the anode where the electron beam strikes. Its size is determined by factors such as the electron beam diameter and the design of the x‐ray tube—not by the anode angle.

What is not an advantage of having a large focal spot on the anode ? A) Allows greater tube output intensity B) Allows short exposure times C) There is no advantage.

added filtration should be equivalent to what amount of aluminium?

2.5mm The choice of material needs to make the photoelectric absorption ppredominant. Often copper towards the tube and aluminium towards the patient. Copper absorbs the low energy x rays, aluminium absorbs the characteristic radiation from the copper. Changes the half value layer (hardens the beam). Maximal photon energy stays the same

which interaction is predominant in the formation of scatter? a) photoelectric effect b) Rayleigh c) Compton d) characteristic radiation

Compton scatter is largely effected by a) tissue density b) atomic number c) photon energy

A but higher energy photons- lower photoelectric effect, so a higher amount of compton proportionally

Compton scatter occurs by interactions with... a) the nucleus b) inner shell electrons c) valence electrons d) protons

Photoelectric effect occurs by interactions with... a) the nucleus b) inner shell electrons c) valence electrons d) protons

which interaction contributes to patient dose the most? a) photoelectric effect b) Rayleigh c) Compton d) characteristic radiation

what type of transformer is in the filament circuit?

step down

what type of transformers are in the high voltage circuit?

step up and autotransformers

why is rectification important

more stable voltage reduce harm to cathode by backward flow of electrons

why is a low voltage ripple rectification important?

more efficient xr production- less peaks and troughs lower dose to patient- reduced low energy xr that contribute to dose only shorter exposure times increased mean photon energy

what are the most common set ups for reduced voltage ripple

three phase power supply (ripple 3.5-13.5%) high frequency generators- the best

how is full wave rectification achieved?

diodes (semiconductors) 4 diodes arranged in a “bridge” circuit → Converts negative cycles into positive cycles

what is the disadvantage of capacitor discharge circuits

Voltage Drop: The capacitor's stored charge decreases with exposure, causing the kV to drop by 1 kV for every 1 mAs used. This limits their use for thicker body parts where higher and more stable kV is required. Limited mAs: The system is generally limited to 30-50 mAs, which restricts the total energy available for longer or more intensive exposures.

which is not an advantage of a falling load generator? a) low exposure time b) maximum mAs with prevention of overheating c) automatic adjustment d) small focal spot

D. Operating the tube at high mA may cause focal spot blooming. This occurs because high mA stresses the anode, leading to a larger focal spot, which can impact image sharpness.

automatic exposure control timers (phototimers) work by which mechanism?

Automatic Exposure Control (AEC) is a system that measures the actual radiation reaching the image receptor and automatically terminates the x-ray exposure once the correct amount of radiation is detected. Key Benefits: Reduces patient dose while maintaining optimal image quality. Minimizes human error in selecting exposure time. Adjusts for patient thickness and attenuation variations. types- photon multiplier detectors, ionisation chambers

what counts as orthovoltage? a) 20-150kV b) 200- 500kV c) >1000kV d) >3000kV

Q5: Which semiconductor material is most commonly used in solid-state rectifiers within x-ray generators? A) Copper B) Silicon C) Tungsten D) Molybdenum

Q6: Compared to a single-phase generator, a three-phase generator improves x-ray production by: A) Increasing the frequency of x-ray pulses per second B) Reducing power consumption by the x-ray tube C) Decreasing the efficiency of x-ray photon production D) Increasing voltage ripple to enhance beam penetration

name 5 ways to reduce scatter

grid, good collimation, compression of tissue, reducing kVp to increase photoelectric effect and air gap

the use of a grid means a (increase/decrease) in patient dose. a ___ in the mAs is needed to account for the absorption by the grid

increased dose increased mAs

what is the difference between phosphorescence and fluorescence?

fluorescence is an almost instantaneous emission of light while the light source is on, whereas phosphorescence is a delayed emission that causes a material to glow for a significant time after the light source is turned off

what is the input phosphor made from in an image intensifier? a) caesium iodide doped with sodium b) beryllium doped with alkali metals c) magnesium phosphor d) tungsten carbide

A The CsI crystals have a trace amount of sodium, causing it to emit blue light The fourth layer of the input screen is the photocathode, which is a thin layer of caesium antimony and alkali metals (which is blue light sensitive) that emits electrons when struck by visible light.

what is the output phosphor made from in an image intensifier? a) caesium iodide doped with sodium b) beryllium c) magnesium phosphor d) zinc cadmium sulphide doped with silver

D Zinc cadmium sulphide is doped with silver for this and has a green emission spectrum. An aluminium layer is used to prevent back scatter.

which colour of light is used to make a Photostimulable Phosphor Detector CR plate emit energy for the formation of an image? a) white b) green c) blue d) red

Which colour of light (x) is emitted from a Photostimulable Phosphor Detector CR plate after stimulation with a 'Y' coloured laser beam? (x, y) a) blue, red b) green, red c) red, blue d) white, blue

a red laser is used, causing energy to be released in the blue spectrum. this should eliminate the latent image so A

what colour light is used to release any residual doped europium in a CR plate after reading? a) white b) green c) blue d) red

which colour light is produced in the input screen of an image intensifier, before being converted to electrons by the photocathode? a) white b) green c) blue d) red

what effect does magnification have on fluoroscopic imaging? a) the image is brighter b) reduced dose as smaller area irradiated c) better resolution

C Magnification is achieved electronically with electronic focusing of the electron beam. If a smaller area of the input screen is sampled the image is still shown on the same area of output screen (the output image size remains constant). This results in a magnified image. Because less signal is used, the image is less bright and, therefore, a higher dose is needed. However, as the image is magnified, the resolution is better. Magnification causes: Less bright image and increased dose required Better resolution

which element is important for CR plates for the storage of the latent image? a) tungsten b) copper c) europium d) bromium

C Phosphor Composition – Typically made of europium-activated barium fluorohalide (BaFBr:Eu), a mix of barium fluoride bromide and other halides. Phosphor Structure – Crystals are embedded in an inert, optically transparent binder and coated on a screen resembling an intensifying screen. Doping Process – Europium activation creates defects (F-centres) in BaFBr crystals, enhancing electron trapping efficiency. CR Screen Material – Composed of amorphous silicon, which lacks a defined crystalline structure.

In indirect DR, xrays are first converted to light in the ___ spectrum

Green CsTI used- so different from instensifier

in indirect DR, how is the CsI arranged to reduce light spread and improve resolution?

structured in columnar crystals (spiky formation), which act as light channels to direct the emitted photons downward, reducing lateral light spread and improving spatial resolution.

which of these is not a component of an indirect DR plate? a) scintillator b) thin film transistor c) charge storage capacitor d) output phosphor e) photodiode

D- is part of image intensifier Scintillator- CsI photodiode- detects light charge storage capacitor- stores generated charge TFT- controls read out process

how are pixel size and fill factor important for image quality in an indirect DR system?

fill factor= sensitive area/ overall area smaller pixels- better resolution but reduced fill factor as the light detecting area is smaller compared to the other components. lower fill factor reduces efficiency

in direct DR what is the photoconductor layer? a) CsTI b) amorphous selenium c) europium d) zinc cadmium sulphide doped with silver

which has higher resolution? direct or indirect DR?

direct- Minimal lateral diffusion of charge ensures high spatial resolution. Direct conversion prevents blurring caused by light spread in indirect detectors.

which is not a way to improve spatial resolution in CR systems? a) smaller laser beam b) smaller pixels c) thicker phosphor layer d) smaller phosphor crystals

C- a thinner layer is required all at the expense of efficiency, higher dose needed

which is a way to improve spatial resolution in CR systems? a) no light reflecting backing layer b) thicker phosphor layer c) larger phosphor crystals d) stronger read out laser

which is better, an MTF of 0 or 1?

1. MTF quantifies how well an imaging system preserves signal contrast at different spatial frequencies (object sizes). Higher MTF at a given spatial frequency = better spatial resolution and imaging performance. 1 is the highest value

when looking at an MTF curve, as spatial frequency increases, contrast resolution ____

decreases. Unlike simple spatial resolution measurements, MTF provides a "true" or effective resolution that includes blur and contrast changes

what is the definition of DQE? a) quantifies how well an imaging system preserves signal contrast at different spatial frequencies b) tells you the smallest single object that can be seen on a radiographic system c) The range of x-ray exposure levels over which the detector can produce a linear response without saturation or signal loss d) measures how efficiently an imaging system records information from the received x-ray signal

D. Higher DQE results in better signal-to-noise ratio (SNR) and reduced radiation dose. the more efficient it is, the lower dose is required while maintaining good quality images

which system has the highest DQE at a spatial frequency of 3lp/mm

direct flat panel detector

which system has the highest dqe at 1.5lp/mm?

indirect FPD

Which of the following correctly lists the typical spatial resolution (in line pairs per millimeter) from highest to lowest for film–screen, computed radiography (CR), and digital radiography (DR) systems? A. DR (Direct)- CR - Film–Screen B. Film–Screen - DR - CR C. CR - Film–Screen - DR D. DR - Film–Screen - CR

B. film screen is High resolution but narrow exposure latitude and no digital post-processing. can get high res CR, which is better than DR in terms of resolution, but not efficient.

Which of the following statements regarding Computed Radiography (CR) and X-ray luminescence is TRUE? a) The latent image in a CR plate is formed by the direct deposition of silver halide crystals. b) Europium (Eu²⁺) acts as a dopant in BaFBr phosphor and is oxidized to Eu³⁺ during X-ray exposure. c) During image readout, a blue laser beam stimulates trapped electrons to emit red light photons. d) The latent image in a CR plate is permanent and can be re-read multiple times without erasure

10. What type of noise occurs due to too few X-ray photons striking the detector? a) Quantum noise b) Electronic noise c) Structured noise d) Amplification noise

15. What is the primary advantage of a fast screen in film radiography? a) Requires higher exposure levels b) Reduces the need for an intensifying screen c) Improves image sharpness by increasing film thickness d) Provides better contrast and detail with lower exposure

what is the full width half Max value

a measure of the contrast/unsharpness within the system. the width of a distribution or peak measured at the point where the intensity is half of its maximum value. It's calculated by finding the difference between the two points on the x-axis where the function's value is equal to half of its highest point. FWHM is a common measure of the width, resolution, or bandwidth of a feature or signal.

how does the detector aperture of a digital system affect sharpness?

The detector aperture is the size of the sensitive area of each detector element. The signal is averaged over this area. Therefore details that are much smaller than the detector aperture are not visible unless they have enough contrast to have a significant effect on the average signal. Sampling pitch Sampling pitch is the centre-to-centre distance between individual detector elements. It determines the highest spatial frequency that can be imaged. This is called the Nyquist frequency. In many digital detectors, the detector aperture and the sampling pitch are virtually identical

how are latitude and contrast related?

Latitude is the range of photons that delivers optical density within the useable range Latitude is inversely proportional to contrast I.e. Use a wide window/extended latitude for the thorax because you want LESS contrast and more shades of

you image an antebrachium and this is your OD graph. how would you improve the imaging contrast of the bone?

increase the kVp

what has happened in the image here, when assessing the mtf?

The pattern has about four black to white cycles in the space that the system requires to achieve one cycle. The consequence is that the system is only able to use part of its range of grey scale or optical density. Although the pattern is seen at the correct spatial frequency, the contrast is much reduced (bottom pattern). If the spatial frequency of the pattern were increased further, the contrast in the image would be reduced further, until it became a uniform grey. At some stage, the contrast would be too small for the pattern to be discernible. If there were only small subject contrast in the object, the pattern would become indiscernible much earlier. Resolution is ultimately limited by contrast. At low contrast, resolution is poorer. range of contrast is reduced at higher frequencies. Poor resolution is seen as a decrease in contrast at higher spatial frequency

if you increase the source to image distance in XR, what other factor do you need to increased to maintain image quality?

mAs mAs1/mAs2 = SID1/SID2

1. What is subject contrast in X-ray imaging, and what most directly influences it? A)The difference in brightness on the monitor, influenced by window/level settings. B) The difference in X-ray beam fluence emerging from the patient, influenced by atomic composition, density, thickness, and kVp. C) The difference in optical density (ODA−ODB ODA - ODB ODA−ODB) on the detector, influenced by scatter from overlying tissues. D) The difference in signal-to-noise ratio (SNR), influenced by the detector’s pixel size.

2. What is displayed contrast in digital radiographic systems, and how is it primarily adjusted? A)The difference in X-ray beam fluence, adjusted by changing kVp. B) The contrast on the viewer, adjusted using a window/level LUT to map high bit-depth data to the monitor’s grayscale range. C) The difference in optical density (ODA−ODB ODA - ODB ODA−ODB), adjusted by the detector’s bit depth. D) The signal-to-noise ratio (SNR) on the monitor, adjusted by the anode target material.

3. What determines the amount of detail visible in a radiographic image, and how do spatial resolution and sharpness differ? A)Detail depends on pixel size alone; spatial resolution defines edge clarity, while sharpness determines how small an object can be seen. B) Detail depends on spatial resolution and sharpness; spatial resolution relates to the smallest visible object, while sharpness defines edge clarity. C) Detail depends on detector bit depth; spatial resolution measures line pairs per mm, while sharpness is unaffected by contrast. D) Detail depends on kVp settings; spatial resolution is unaffected by pixel size, while sharpness measures the smallest detectable object.

4. What is magnification in radiography, and how does it affect image quality? A)Magnification = SOD/SID; increasing SID decreases magnification and increases geometric blurring. B) Magnification = Actual patient length/Length on image; increasing SOD increases magnification and scatter. C) Magnification = SID/SOD; increasing SID increases magnification, while a larger focal spot size increases geometric blurring. D) Magnification = SID/SOD; increasing object-to-receptor distance increases scatter and fog

what is the k edge of iodine? a) 53 b) 33 c) 80 d) 64

B 33.2keV

what is space charge limited operation?

For tube voltages 40kV and lower, a space charge cloud shields the electric field so that further increases in filament current do not increase the tube current. This is known as “space charge–limited” operation. Above 40 kV, the filament current limits the tube current; this is known as “emission-limited” operation

how does a biased focussing cup reduce the size of the electron cloud

biased- A voltage of about -100V is applied with respect to the filament voltage to further reduce the spread of electrons and produce a smaller focal spot width. unbiased- the focusing cup is maintained at the same potential difference as the filament (relative to the anode

2 xrays Flashcards

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