Dr. Choi Q7 - Final
*intensifying screens* do what?
*- convert X-rays to visible light - reduce patient dose - sensitive to visible light*
Effective Dose Equivalent Limit - fetus
*0.5 rem(5 mSv)/9 mo.*, not to exceed 0.05 rem/mo.
ALARA means
*A*s *L*ow *A*s *R*easonably *A*chievable The reasonableness of the dose must coincide with the diagnostic quality of the film.
Emulsion pick off artifacts
*Cause:* dirty rollers
Chemical fog artifacts
*Cause:* inadequate or improper chemistry.
Crescent moon [finger nail] artifacts*
*Cause:* kinking film with finger or nail
Light or radiation fog artifacts
*Cause:* light leaks, primary beam, safe light too close.
*high kVp*
*Compton Dominant* [low contrast]
what are the 2 most important *interactions of X-rays with matter*?
*Compton and photoelectric effect* [Pair Production]
Difference between X-Ray & Gamma ray
*Gamma rays* are produced as byproduct of radioactive decay in nature *X-rays* are man-made & produced by sudden stopping of high speed electrons in an x-ray tube (control)
Tungsten - W74 Electron Binding Energy
*K shell = 70 keV* - (this may be important later) L = 12 keV M = 2.8 keV N = 0.6 keV O = 0.08 keV
*low kVp*
*PE dominant [high contrast]*
kVp determines the
*Quality* of x-rays [penetrating power] Higher kVp = faster electrons = stronger interaction with tungsten = stronger x-rays [hard x-rays]
Film Badge
*Radiation [Xray/Gamma] sensitive film* in a small plastic holder clipped to clothing Pro: Inexpensive & reasonably accurate (80% - con) Con: 10mR-50mR range, sensitized by heat/pressure, can't be worn >month d/t temp/humidity
[kVp Control knob] kVp determines the
*Speed of electrons hitting the anode.* 1. Major selector= increments of 10 starting at 40- 125 kVp (common for chiropractors) 2. Minor selector= increments of 1 from 1 to 10 kVp
Define *Half Value Layer* (HVL)
*The absorber thickness required to reduce the intensity of radiation to ½ its original value* [used for leakage shielding & to determine need for lead lining]
What are the two areas of work that need to be kept separate regarding Darkroom design?
*Wet area* - handling chemicals processing film. *Dry area* - loading & unloading cassettes.
Does wider latitude with higher kVp or narrow latitude with low kVp gives more room for error?
*Wider latitude* with higher kVp.
*Faster film/screen speed* correlates with a
*decreased mAs*
Voltage
*force applied to electrons to move them* - electrical potential difference b/w two points in a circuit, one having more electrons than the other volt/kilovolt
*Lower contrast* (Longer gray scale) =
*higher kVp* - lower patient dose, but more Compton scatter [increase film fog]
grid ratios and effectiveness?
*higher the ratio the more effective at cleanup*
If you have an *underexposed film* what do you want do with mAs?
*increases mAs* = increases OD → darker film
Variable aperture collimator contain:
*lead shutters* or leafs that open & close to a desired field size. *Less Penumbra* b/c further away from tube port window then aperture diaphragm
Non-Stochastic Radiation Effect Aka. Deterministic effects
*occurs with certainty* following a measured radiation dose and severity increases with the dose. hours/days large dose; short time Threshold dose
Stochastic Radiation Effect:
*probability/best guess* probability of occurrence of the biologic effect to radiation increases as the dose increases *long term effects* i.e *Malignancies & Genetic mutations*
*Supercoat* on a composite film does what?
*protects emulsion layer* from scratching, pressure and contamination
What is the exposure latitude?
*range of mAs* at a given kVp → filament circuit → number of projectile electrons → number of xray photons → acceptable OD of the film.
Please explain the recommended wall color of a 'Darkroom' for X-ray film processing.
- *Light pastel colors* (allow for less intensity safelight) - yellow semi-gloss (reflects low levels of light) . Black walls require a higher intensity safelight.
*Contrast Improvement* Through Scatter Control
- *Optimum kVp* - *Field Size control* - Beam Limiters - Grids - Air-gap technique - *Recumbent Radiography* & tissue compression devices
What is an automatic exposure control or device?
- *compensates for patient density automatically.* - Photocell in the bucky measure radiation exposure to film. - You set the mA and kVp- the AED is preset for desired film density. - Automatically shuts off exposure at desired film density.
What occurs in a Fixed (Optimum) kVp Technique?
- *m/c used* - *Highest kVp* that results in *lowest patient dose* and *acceptable contrast.* - A single kVp is set to ensure adequate penetration of a wide range of patients thickness. - Controller is *mAs* - The kVP will be *higher than* used in *variable kVp techniques.*
Administering Dose: Protraction
- A continuous low dose rate for a long period of time. - Reduces biological effects of radiation Examples: radioactive pellets inserted in the thyroid or prostate, controls proliferation of cancer cells without destroying the tissues.
Radiation Characteristics: *Linear Energy Transfer (LET)*
- A measure of the rate at which energy is transferred from *ionizing radiation to soft tissue* - LET ↑ = ↑ ability to produce biological response - Particles with high LET → Transferring more energy to the tissue [more damage] Alpha Particles: high LET (superficial malignancies) X-Ray: low LET
Credentials for taking x-rays
- ARRT certification - Am. Registry of Rad Techs. - 2 yrs minimum - ACRRT - Limited radiographer - Chiropractic Tech's Accepted by many but not all states. (Minimum 48 hrs course.)
Alternating Current (AC) movement
- BIDIRECTIONAL - movement of electrons that constantly change speed & direction of flow - U.S. uses 60 Hz
What are the advantages of a fixed kVp technique?
- Consistent contrast. - Decreased patient dose. - Shorter exposure times= less motion [blur] - *wider latitude (mAs range)*
What are the disadvantages of variable kVp technique?
- Contrast may be too high. [less gray scale] - Increase pt. dose [low kVp] - Increase patient exposure times- more motion. - Narrow latitude. [mAs range] - Less consistency between exposures.
Describe High Frequency transformers:
- Decreases exposure time = decrease pt. dose. - larger pts - Voltage ripple < 1% - It produces high quality (high energy) X-ray beam
Explain Rotating Anode
- Developed in 1929 by Phillips Corp. - *Designed to increase the capacity of the anode to withstand heat* - It increased the heat capacity by a factor of 200 - It is disc-shaped and mounted on a spindle - Made of molybdenum & covered with tungsten
Tissues most sensitive to carcinogenic effects of ionizing radiation:
- Female Breast (minimize w/ P→A) - Active bone marrow [adolescent teen females need breast shield d/t higher risk of developing breast cancer]
Characteristics of Slow Film
- Less sensitive to light → Longer exposure time - clear [better image detail]
By minimizing voltage ripple, we can achieve...?
- More *constant kVp* (less fluctuation in voltage change). - Production of *high quality/quantity*. - Close to true DC vs. pulsating DC. - More efficient production of X-rays. - *Shorter exposure time* & less soft X-rays → *lowering patient dose*
What is variable kVp with an optimum range?
- More difficult because *two variables* may change. [mAs/kVp] - More accurate in customizing body part settings. - Short range of optimum kVp's. - Requires experience to master.
Characteristics of Fast Film
- More sensitive to light → Short exposure time - grainy & less detail
What are some Technique Conversion Factors?
- Pediatric - Elderly - Cast - Grid - Speed - Distance - Pathology
What is a technique chart?
- Predesigned technique information that includes anatomical region, body part, cm measurements through the central ray, mA, s, kVp, mAs, film size and bucky or no bucky. - Standardized to give machine considering the generator type, grid and film/screen speed.
Transformer [Generator] assembly
- Receives input from the control console - prepares exact *electrical output* to the x-ray tube via transformers
Radiation Effects on Fertility:
- Temporary sterility males & females - dose of 200 rads to gonads. - Permanent sterility - dose of 500 rad to gonads.
What is variable kVp technique?
- The *mAs is set* per body part and the *kVp is varied.* - kVp = 2X the cm thickness of part + 30 [lumbar] [+40 C/T; +50 EXT] - *lower* kVp compared to FIXED kVp technique - Best used in the *60-80 kVp* range for the spine.
Direct Current (DC) movement
- UNIDIRECTIONAL - Has 2 types: Uniform & Pulsating
Ways to keep dose reasonable:
- Use optimum kVp technique *High kVp - reduce dose* - *C*ollimate to film size or less - Reduce exposure to radiosensitive organs (*P-A position helps*) - Maintain *calibrated* equipment - Use rare earth screens/films. - Appropriately use *gonad shields & aprons* - Use *portal filters* - vs underpart filter - Minimize patient *position errors -less repeat films*
Types of Tube Failure
- Vaporization - Surface Melting, Pitting or Cracking (anode) - Failed Bearings - Rotor Assembly [M/C] - Cracked Glass - x-ray tube
Factors in determining shielding requirements:
- Workload = Amount of radiation produced - kVp and mAs used - Distance from source to protected areas - Existing walls construction material - Scatter & leakage radiation consideration - Operator location - Occupancy of surrounding areas
*Air gap technique*:
- a *physical gap* between the patient and the buckey instead of a grid. - the magnification and distortion outweigh the benefit - *REDUCES SCATTER*
Operating Booth
- able to see pt. for all performances - viewing window - leaded glass. 18" from the edge of the booth - exposure switch far from entrance booth - open booth - beam needs to be scattered twice before it reaches operator [RED line]
Prep Switch [rotor switch]
- activates electromagnetic induction *rotor*, turning the anode. - activating the *filament circuit* [mA] --> cloud of electrons [space charge] --> preparing for *thermionic emission* - prepares for exposure by producing cloud of electrons and bring rotor up to speed
Exposure switch
- activates the *high voltage circuit* moving the electrons from cathode to anode, creating x-rays and making the exposure
Control Console characteristics?
- can control x-ray tube current, voltage & exposure - houses the meters and controls for the line compensation, kVp, mA & exposure timer.
Linear Grids
- commonly used - parallel - allows for tube tilt w/o attenuation of beam
Distance: FFD or SID
- focal spot to film distance - source of image receptor to distance - this distance affects the *number of x-rays reaching the film*, and follows the inverse square law
Filament circuit mAs [low voltage]
- generates a space charge - uses a *step down transformer* - step down causes a proportional increase of current - provides current to the filament - *generate electrons in a controllable fashion at the filament*
Administering Dose: Fractionation
- high dose rate - Delivered in increments with healing time between - Reduces the biological effects of radiation - Kills all types of tissues - aggressive cancers Example: Bronchogenic Carcinoma Goal - kill cancer not patient
What are some advantages of the line-focus principle?
- improves spatial resolution - improves heat capacity
To decrease motion unsharpness:
- instruct pt. not to move - immobilization devices - lock equipment in place - short exposure time
Half-Wave Rectification Current
- inverse voltage is removed by rectification - x-ray is pulsed at 60 pulses/sec.
Explain Stationary Anode
- large mass of copper to dissipate heat & conduct electricity - is limited in its heat capacity from electrical load - used mostly in low output machines - has tungsten embedded in the copper as a target
Describe 3 phase:
- nearly constant voltage - > # of photons at all levels = high energy beam = decrease pt. exsposure
Full-wave Rectification
- negative impulses of an AC waveforms are reversed - x-ray is pulsed at 120 pulses/sec.
X-Ray Tube characteristics:
- protective metal housing - *Glass* Enveloped - Two electrodes: *Anode* & *Cathode* - electronically *vacuumed* leaving no gas to reduce X-Ray efficiency
Tube housing characteristics? (4)
- provides mechanical support for the glass x-ray tube - prevents electrical shock - provides thermal cushion - prevents leakage radiation
High voltage circuit [kVp]
- purpose: *drive the electrons from cathode to anode* - Kinetic energy of high-speed electron is *directly proportional* to the kVp - kVp is the only factor affecting x-ray energy - activated by exposure switch - standard: 220volts - requires: *step-up transformer*
High kVp=
- stronger cathode to anode attraction of electrons - more e- [more x-ray photons] - faster e- [stronger x-ray]
Central Ray (CR) is
- the central portion of the primary beam - directed at the center of the structure to be radiographed an to center of film
In a Filament Circuit, mA is inversely proportional to
- turns ratio [step-down transformer]
In a High Voltage Circuit, kVp is directly proportional to?
- turns ratio - kinetic energy of high- speed electron
What is the range of exposure latitude that is diagnostically useful?
0.25 - 2.5
Radiation Absorbed Dose (RAD) is?
1 Roentgen (R) = 1 RAD in soft tissue
Factors that affect penumbra are?
1) *Focal Spot Size* 2) Source to object distance (SOD) 3) Object to image distance (OID)
factors contributing to scatter?
1) *kVp* 2) *tissue type and thickness* 3) *Field size*
What are the 2 types of Dynamic Electricity?
1) Alternating Current (AC) 2) Direct Current (DC)
What are the 3 parameters to describe the waveform of a photon of Electromagnetic Radiation?
1) Frequency 2) Wavelength 3) Velocity V=F x wavelength
3 basic factors in all circuits are?
1) Voltage 2) Current 3) Resistance
What are the 3 parts of the Quantum Theory?
1) X-rays exist at the speed of light or not at all 2) Photon energy is *directly* proportional to the *photon frequency* (high frequency = higher energy) 3) Photon energy is *inversely* proportional to *photon wavelength* (longer wave = lower energy)
if we overexpose a film and want to lighten it, what are our two methods?
1) decrease mAs by 50% 2) decrease kVp by 15%
2 major factors of radiographic contrast are?
1) detector contrast (film) 2) subject contrast (absorption characteristics)
3 main components of x-ray system are?
1) x-ray tube 2) control console 3) transformer assembly
3 circuits inside the transformer
1. *High voltage circuit* [kVp]- connected to anode 2. *Filament circuit [mA]* - connected to cathode 3. *Timer circuit* - controls the cathode and anode
*Systems International Units* 1. Roentgen (R) [Ionization in Air] 2. Radiation Absorbed Dose (RAD) [Living/Non-Living] 3. Rad Equivalent Man (REM) [Biological Effects] 4. Curie (Ci) [Radioactivity]
1. *SI*: Coulombs/kg 2. *SI*: Gray (Gy) 3. *SI*: Seivert (Sv) 4. *SI*: Becquerel (Bq)
3 Cardinal Rules of Radiation Protection: (occupational workers)
1. *Time* - keep exposure time short 2. *Distance* - stay as far away from the radiation as possible 3. *Shielding* - shield radiosensitive organs
Conditions needed for x-ray production
1. A source of electrons 2. A means to accelerate electrons 3. A hard surface to decelerate electrons
Types of Beam Limiters
1. Aperture diaphragm 2. Cones & Cylinders 3. Collimators - Semi-automatic - Fully-automatic
What are the steps of automatic processing of X-ray films?
1. Developer 2. Fixer 3. Wash 4. Dry
Details on Inspection:
1. Distance accuracy 2. Collimation accuracy 3. Filtration 4. Beam alignment 5. Personal Shield
Measurement of radiation dose to occupational radiation workers?
1. Film badge 2. Thermoluminescent dosimeter (TLD) 3. Pocket dosimeter
Please list the nine 'Artifacts' seen on X-ray film, as given in the notes.
1. Guide shoe marks* 2. Pi lines* 3. Crescent moon [finger nail]* 4. Chemical fog 5. Curtain effect 6. Static artifacts* 7. Light or radiation fog 8. Emulsion pick off 9. Hypo/Hyporetention [artifacts with asterisk* very important]
Switches on the control console
1. Main on/off switch- has a separate breaker 2. Line- voltage compensator LVC 3. Milliampere Knob [mA] - higher mA for bigger/ thicker person 4. Timer control- presents the exposure time
Protective Barrier Design 4 Requirements?
1. Primary Protective Barrier (primary wall) 2. Secondary Protective Barrier (secondary wall) 3. Operating Booth 4. Inspection [includes replacing old tube]
Control console
1. Quantity- amount produced [mA] 2. Quality- their energy, activity [kVp] 3. Duration of x-rays [Sec]
2 types of generators
1. Single phase 2. Constant potential [three-phase, high frequency]
3 types of constant potential generators or transformers
1. Single phase 2. Three phase 3. *High frequency* [voltage ripple < 1%]
What are technique systems?
1. Technique charts: SuperTech. 2. Anatomical pre-programmed techniques. [APT] 3. Automatic exposure control or device. [AED]
Preventing tube failure
1. Warm up anode - prevents cracking 2. Determine heat unit limits by using the charts- decrease the mA and increase the time
4 primary factors of exposure
1. kVp 2. mA 3. time 4. Distance
Problems with Grids
1. upside down 2. off level 3. off focus 4. warped 5. lateral decentering
chest x-ray exposure ?
10 mrem per exposure
Human & animal studies suggest that teratogenic & developmental effects are minimal with exposures below?
10 rads = 10k mREM.
100 speed film with 20 mAs changing to 400 speed film What's the mAs
100 x 20mAs = 400 x mAs2 2000/400 = *5 mAs*
1 Amp = ? mA
1000 milliampere
How much radiation dose from the whole body scanner?
1000-2000 scans = 1 chest x-ray
First patent for a line focus tube was issued in ________
1916
Which trimester is more sensitive to radiation?
1st trimester [8.3 more] 3rd - 7th wk - higher risk of congenital malformations
human exposure to radiation per day ?
2 mrem/ day = about 620 mrem/ year
how do you warm up an X-ray tube?
2 successive exposures with collimator closed at 50 and 100 mA @ 50kVp and 1/30 sec
solar flares can increase radiation while flying by how much?
200 times
for every 5000ft of elevation we get how much more radiation?
2X (from cosmic radiation)
Anodes rotate at _____________ rpm and some at ________________ rpm
3,400 rpm 10,000 rpm The faster the rotation the greater the load capacity
radon gas accounts for how much of the 620 mrem of exposure per human per year?
37%
Dx X-ray is what range of Voltage?
40 to 150 kV
Focused grid range from
40 to 72 inches
human radiation is broken up into what percentages (natural/ human-made) of the 620 mrem?
50% man-made 50% natural
processed films should be stored how?
50-60% humidity 60-80 degrees F
optimal kVp for smaller extremities is
55-60 kVp
characteristic X-ray of tungsten is what?
58kVp [due to electron binding E difference b/t K & L shells]
Laws Governing Filtration
70 to 100 kVp = 2.5 mm equiv. Aluminum
optimal kVp for larger parts of the spine is ?
80-90 kVp
grids with "good cleanup" will reduce scatter by how much?
80-90%
Compton Effect produces what percentage of scatter at 70 kVp
95% -5% from classic scatter
Increasing the *SID* does what to sharpness & recorded detail?
= decrease in unsharpness (increase sharpness) = increase recorded detail. = less magnification
Decreasing the *OID* does what to sharpness & recorded detail?
= decrease in unsharpness (increase sharpness) = increase recorded detail (decreased magnification)
Decrease in the film-screen speed system does what to unsharpness and recoded detail?
= decrease in unsharpness (increased sharpness) = increase in recorded detail
Decreasing the *SID* does what to sharpness & recorded detail?
= increase in unsharpness (decrease sharpness) = decrease recorded detail. = more magnification
Increasing the *OID* does what to sharpness & recorded detail?
= increase in unsharpness (decrease sharpness) = decrease recorded detail (increased magnification)
Increase in the film-screen speed system does what to unsharpness and recoded detail?
= increase in unsharpness (decreased sharpness) = decrease in recorded detail.
Increasing a Focal Spot, does what to unsharpness & recorded detail?
= increase unsharpness = decrease in recorded detail
Processing & contrast with WEAK chemicals?
= underdeveloped film Overall film density reduced Decreases Contrast
Soft x-rays [lower voltage]
Absorbed in the body → don't reach the x-ray film,. Increase patient dose [Slower e- and lower frequency]
Most common material used in chiropractic for compensating filters?
Aluminum
Define Electricity
An effect produced with the movement of electrons OR the flow of electrons from one place to another
Umbra
Area of geometric Sharpness
Difference between Transmission & Backscatter X-Rays
Backscatter - bounces back Transmission - through body
Biological Factors: Oxygen Effect
Biologic tissue more sensitive when irradiated - In oxygenation state (aerobic) - High pressure oxygen used to increase sensitivity of nodular & avascular tumors in radiation therapy.
What are the three types of Screen Film?
Blue Sensitive Green Sensitive UV Sensitive
bone rad vs soft tissue rad
Bone has about 4X RAD as soft tissue, meaning it absorbs 4X as much (3.6:1 about a 4:1)
food with a lot of potassium? (1/ 8550 = radioactive)
Brazil nuts, lima beans, bananas
what kind of diagnostic imaging will give you the most ionizing radiation exposure?
CT scan
The only element in the body with a binding energy (4keV) at the k-shell to produce x-rays is?
Calcium
Which side of the X-ray beam between anode side and cathode side has greater penumbra effect?
Cathode
Electron Spin Velocity
Centrifugal force that pushes away due to inertia and stops the electrons from crashing into the nucleus = equilibrium
Function of Beam Limiters
Changes the size & shape of the primary beam. Decreases scatter = increase in contrast Increase collimation (tightening) = decrease field size = decrease pt. dose.
PE vs Compton in *soft* tissues is ?
Compton >> PE
increased X ray energy is going to do what to the ratio of photoelectric effect vs Compton scatter?
Compton >> PE
why does high kVp create less contrast?
Compton scatter
Natural Radiation Sources aka. Natural Background Radiation (NBR)
Cosmic Radiation Terrestrial Radiation Internal Radiation
Acute Radiation Syndrome: what is it & how does it manifest?
Death may ensue within days or weeks of certain whole body radiation. 1. Hematologic <1k] 2. GI [1k-5k] 3. CNS [>5k]
If you have an overexposed film what do you want do with mAs?
Decrease mAs = decrease optical density → Bright or white
Determining Heat Unit Limits: How to make an Unsafe technique Safe
Decrease the mA & increase the time, using the same kVp. [Changing the kVp will change the exposure of the film]
motion of the tube does what to recorded detail?
Decreases [creates a blur] - need shorter exposure time
*Low kVp & Contrast*
Decreasing kVp = less penetrating = decrease scatter = more PE effect (than Compton) = decrease fog = increase contrast.
Compensating Filters are for?
Density balance when there is 'over' & 'under' exposure on the same film (Make up for variation in patient thickness/over thinner body parts)
4 Important considerations in selecting proper screen-type film for your office
Detector Contrast Film Speed Latitude Spectral Response
X-rays that have energy of 40 - 150 keV and are used in medicine, Chiropractic, dentistry, etc
Diagnostic
X-rays that are used for research & analysis and have energy < 10 keV
Diffraction
Types of X-Rays
Diffraction Grenz Diagnostic Superficial Orthovoltage Supervoltage Megavoltage
mAs is _______ ____________ to the tube distance?
Directly Proportional
A 15% increase in kVp =
Doubling the OD
When the mA is doubled what happens?
Doubling the mA (100mA to 200mA) → 2 X the *number of electrons striking the anode* → *2 x* the number of *X-rays produced* Doubles the darkness of the film (exposure)
Cast Conversions
Dry cast- add 10 kVp from non-cast tech. or double mAs Wet cast - add 15 kVp from non-cast tech. or triple mAs Fiberglass cast add 5 kVp from non-cast tech.
Radiation Definition
Energy in motion through space and/or matter.
What is the technique chart best for?
Estimating for exposure.
Controlling the *exposure area* helps limit patient dose/improves quality and should never:
Exceed film size
Higher volatile to the anode will result in an increase number of electrons at the filament. T or F
F- no effect of the number of electrons at the filament → filament circuit
T/F - Genetic mutations from radiation exposure stay in the gene pool for many generations.
FALSE [women exposed to less than 50 rads had no children born with defects]
How does a filter work?
Filtration "hardens" the beam by increasing the average energy of the beam
What are the ways to apply technique?
Fixed kVp. Variable kVp. Variable kVp within an optimum range.
Information needed to give a medical radiation physicist?
Floor plan Location of x-ray machine Primary & secondary walls - What they are made of Occupancy of adjacent rooms
Underpart Filter - Boomerrang
For shoulder imaging Placed behind shoulder to filter soft tissue - over-exposure of AC joint is common without filtration.
ionization
Gaining or losing electrons to form ions
Ionizing Radiation examples
Gamma rays X-rays Protons Neutrons Electrons Beta particles (fast neutrons) Alpha Particles
Penumbra
Geometric unsharpness along the edges of the film/structure imaged - *greatest* on the *cathode side* of the tube -x-ray beam is *stronger* on *cathode* side
X-rays that have energy of approximately 10 keV and are used in dermatological therapy
Grenz (means boundary/borderline)
Two types of rectification?
Half-wave rectification - 2 diodes Full-wave rectification - 4 diodes
Can we minimize anode heel effect?
Heel effect is *less noticeable* with *smaller exposure areas* due to collimation.
lowest voltage ripple?
High Frequency Wave
How would kVp affect HVL?
Higher the kVp →more penetrating power→need thicker HVL
Voltage ripple
Highest volt to lowest volt [we want to minimize voltage ripple]
kVp determines:
How fast the electrons travel across the x-ray tube Quality of X-ray Beam = Penetrating power
Inverse Square Law formula
I = X-ray intensity in mR d = distance in inches I= 1/d^2
*High kVp & Contrast*
Increasing kVp = *Increase* the amount of *scatter* (Compton) = increase fog* = *decrease contrast*.
Total Filtration
Inherent - 0.5 mm Added - 1.0 mm Mirror - 1.0 mm Total = 2.5 mm equiv. Al.
Energy in motion
Kinetic Energy
Types of Grid Designs
LINEAR CROSS GRID (CROSS HATCHED) FOCUSED GRID
Non-ionizing Radiation
Lacks the energy to knock out an orbital electron from an atom. causes excitation w/in atom
What kind of focus is used for (greater heat dispersion) longer exposure times & thicker, denser body parts (large filament) (thorax, abdomen, lumbar spine)
Large Focus
Biological Factors Affecting Radiosensitivity
Law of Tribondeau & Bergonie: Oxygen Effect: Age: Gender: Chemical Agents:
Radiation that is emitted from any part of the housing other than the Port Window?
Leakage radiation
What are the advantages of variable kVp technique?
Less scatter - Lower kVp.
What results in effective focal spot size much less than the actual focal spot size?
Line-Focus Principle (LFP)
Lumbar X-ray, CXR & CT approximately how many mRem?
Lumbar - 50 mREM CXR - 6-10 mREM CT - 1000 mREM xray - no residual radiation
MRI is gold standard for what Dx?
MS, spinal cord lesion, joint disease, brain tumors
How does the Anode rotate in the tube?
Magnetically by electromagnets *[stator]*
X-rays that have energy >1000keV and are used to *eradicate deep-seated tumors*
Megavoltage
What is the anatomical preprogrammed technique?
Menu driven: - Select anatomical part, i.e.C spine.and the view, i.e. lateral C spine. - Punch in the patient's measurements. - kVp and mAs appear on menu. - You can increase or decrease any factor.
What are the disadvantages of fixed kVp technique?
More scatter (higher kVp) Lower contrast.
Biological Factors: Age
More sensitive *before birth* Decrease sensitivity until mature Become more sensitive in *old age*
radiation sources
Naturally occurring (environment) Artificial Sources (Human made devices)
radiation categories
Non-Ionizing Radiation Ionizing Radiation
Ten Day Rule
Non-emergency films done in the 10 day period from the onset of menses
OID Stands for?
Object to Image-receptor Distance
Pi Line Artifacts*
Occur every 3.14 inches. *Causes:* dirty rollers or flat edge on roller.
Portal Filter Characteristics?
On collimator or tube head Attenuate beam *before* reaching patient reduce direct patient dose PREFERRED
Diodes allow for
One direction of electron flow
X-rays that have energy of 200 - 300 keV and are used in radiation therapy for carcinomas
Orthovoltage
Electromagnetic Radiation
Oscillating electormagnetic fields that travel in a vacuum with the velocity of light
What pathologies are EASY to penetrate?
Osteoporosis, multiple myeloma, metastatic bone disease, carcinoma Disuse atrophy, various bone tumors and emphysema. *50% reduction in mAs*
What type of overhead light is recommended for the darkroom?
Overhead white light [incandescent > fluorescent]
How should the chest be positioned when taking chest X-rays to minimize the magnification of the heart?
P → A because it has less magnification
PE vs Compton in *hard* tissues is?
PE >> compton
What are other factors to consider in a technique chart?
Patient age. Tissue density. Pathologies. [constantly update]
Minimize health risks to:
Patients Staff General public
Elderly Conversions
Patients over age 55 ↓ mAs by 30-50% - On average - ↓ 30% - males - ↓ 50% - females Bedridden over 6 months ↓ mAs by 50%
Hard x-rays [higher voltage]
Penetrate the body → reaching the x-ray film [faster e- and higher frequency]
Is an area of geometric unsharpness along the border of a structure, which causes the border to appear fuzzy?
Penumbra
Types of factors of Radiosensitivity
Physical & Biologic factors
Underpart Filter Characteristics?
Placed behind the patient Beam is attenuated *after* it exposes the patient Patient dose is NOT reduced
Compensation Filters Identified by Location of Application
Portal Filter Underpart Filter
When considering Safelight sources in your Darkroom, how is the film sensitivity to light changed after exposure to X-ray?
Post exposure Fog [PEF] -exposed film is 10X more sensitive to light than unexposed films.
time control know [sec]
Presets the exposure time - automatically stops
mA Control Knob
Presets the filament voltage & current for a tube current (50 mA, 100 mA, 200 mA, 300 mA, etc.) - Lower current (50 mA & 100 mA) → small filament 50S, 100S - Higher current (200 mA & 300 mA) → large filament 200L, 300L
Primary Protective Barrier
Primary Wall - A - Primary beam point at - lead sheeting
*Rectification* of current
Process of converting AC current to DC current. - accomplished by *diodes* or *rectifiers* that allow flow in one direction only and saves the tube
The relationship of energy of an x ray photon to its wavelength is known as the?
Quantum Theory
REM equation
REM = Wr x RAD (Wr= weighting factor, or type of the ray) 1 rad X-Ray = 1 rem 1 rad alpha particles = 20rem
what is the order of waves of non-ionizing radiation on the spectrum
RMIVU [Radio (weakest), Micro, Infrared, Visible light, UV light (strongest)]
Physical Factors Affecting Radiosensitivity:
Radiation Characteristics: LET Administering Dose: Protraction, Fractionation
Examples of Non-Stochastic Radiation Effect
Radiation burns Cataracts in lens of eye Loss of fertility Damage to blood or blood forming tissues Other acute effects
Non-Ionizing Radiation examples
Radio waves Microwaves Infrared Visible Light Ultraviolet
EM Spectrum from lowest to highest?
Radio waves (lowest) Microwaves Infrared Visible light Ultraviolet (UV) X-rays Gamma rays (highest)
Biological Factors: Chemical Agents
Radiosensitizers: Enhance effects [Methotrexate, actinomycin D, vit K.] Radioprotectors: decrease effects [superoxide dysmutase]
National Council on Radiation Protection & Measurements [NCRP] does what?
Recommends & communicates radiation protection policy in U.S. (Limitations on Dosage - but no dose limits set)
REM is?
Roentgen Equivalent Man
Please give the two 'Golden Rules of X-ray film processing.
Rule #1: *Standardize procedures* - lack of following a procedure increases the risk of poor quality film. Rule #2: *Keep darkroom & equipment clean* - ignored routine maintenance leads to poor quality film.
Guide shoe marks artifacts*
Run the length of the travel direction of the film, usually 1 inch apart. *Causes:* rough handling of rollers during cleaning, warped plastic rollers Lines are black = developer section Lines are white = fixer or wash
What pathologies are HARD to penetrate?
Sclerosis, DJD, paget's disease, metastatic bone disease, arthritis, bronchogenic carcinoma, pneumonia, edema, various bone and chest tumors. *Increase 4-6 kVp*
What are the three types of Film?
Screen Direct Exposure Duplicating Film
Secondary Protective Barrier
Secondary Wall - B, C, D Any wall in the exposure room NOT exposed to the primary beam Not all need to be leaded
Law of Tribondeau & Bergonie:
Sensitivity related to metabolic activity of tissue irradiated. younger tissue = greater sensitivity - higher metabolic rate - greater proliferation rate of cells - greater growth rate of tissues Differentiation level - how different the cell is from original shape - effect radiation sensitivity
Of the available darkroom doors which type is noted as the most feasible & cost effective?
Single Door.
What kind of focus is used for smaller, thinner, less dense body parts (small filament) (cerv. spine & extremities)
Small focus
Which type of X-ray is more apt to be absorbed in body tissue rather than penetrate through it?
Soft X-ray
SID stands for?
Source to Image-receptor Distance [FFD = Focal-spot to Film Distance (SID)]
SOD stands for?
Source to Object Distance
What are the 2 types of electricity?
Static Dynamic
X-rays that have energy of 50 - 110 keV and are used to treat superficial skin injuries and some types of CA and ringworm
Superficial
X-rays that have energy from 300 - 1000 keV and are used in radiation therapy to treat *carcinomas*
Supervoltage
Space charge is
The cloud of electrons at the filament circuit
What is radiographic technique?
The combination of *mA, time,* and *kVp* for a given FFD [SID] used to produce a diagnostic quality film.
The positive hump on the AC graph is created by
The electrons flying to the anode
Frequency
The number of cycles/second [cps or hertz (Hz)]
Inverse square law
The number of x-rays reaching the film is *inversely proportional* to the square of the distance from the source I= 1/d^2
Current is
The rate of flow of electrons; measured in Amp
Geometric Properties
The sharpness of detail in the image which is achieved by obtaining the maximum amount of "recorded detail" and minimizing the amount of "image distortion."
mAs is a combination of
Time in sec X mA (Ex. Exposure time = 0.5 sec, and 200 mA for lumbar spine --> 200mA x 0.5 sec= 100 mAs)
Static artifacts*
Tree like black jagged lines or smudges *Cause:* static in the dark room- NO CARPET!
High ratio grid is more effective in absorbing scattered radiation than the low ration one. However it requires higher mAs resulting in more patient dose. *T/F*
True
The first completely safe x-ray system was designed by Coolidge for use in dental machines in 1921...T/F?
True
An area of geometric sharpness?
Umbra
What causes electroplating of the internal components of the x-ray tube upsetting the electrical characteristics & leads to tube failure?
Vaporization
What is the formula for Voltage?
Voltage (v) = Current (I) x Resistance (R) - known as Ohm's Law
Energy of EM Radiation is characterized by?
Wavelength
LD 50/30: (Lethal Dose)
Whole body dose resulting in death of 50% of those irradiated within 30 days
EDL for Occupational Exposure
Whole body including radiosensitive organs [eyes, thyroid, breast, gonads, active bone marrow] = *50 mSv (5 rem) (annually)* - Skin, hands, and feet= *500 mSv (50 rem) (annually)*
Biological Factors: Gender
Women survive 5% - 10% *more* radiation than men
The faster the film/screen speed system, the more sensitive it is to
X-Ray density (Extremities - slow Spine - fast)
Radiation Cataracts:
X-rays & Gamma Rays minimum cataractogenic dose: - 200 - 500 rads single exposure. - > 1000 rads delivered over time (probably means intermittently). - Optic Lens - sensitive
1% of kinetic E of projectile electron is converted to?
X-rays (Not all of the X-rays are usable)
Curtain effect artifacts
Yellow, green, blue, purple runs. *Cause:* chemistry not being squeezed from film due to warped rollers or processor is running to slow.
Hypo/Hyporetention artifacts
Yellow/brown stains appear over time. *Cause:* not all of the (fixer) thiosulfate is removed in the wash. Wash water contaminated-not clean.
Exposure
a measure of the *strength* of a *radiation* field at some point *in air*
Roentgen (unit)
a measurement of X-ray or gamma ray exposure (intensity in air) (coulombs/ Kg)
REM was created because?
a universal absorption factor across all absorptions [used exclusively for radiation protection reporting of occupational exposures]
10-15% of beam consists of characteristic x-rays, 80-85% are Bremsstrahlung
above 70 kVp
Grid Conversions
actually a division factor then multiply by old mAs
negative of a really effective grid ?
actually absorbs "good" x-rays, creating a need for more/ higher energy X-rays - *increase pt radiation dose*
remnant radiation is what?
all radiation exiting the patient and heading towards the film - unabsorbed primary X-rays/ secondary rays/ scatter
air infused tissues allow the X-rays to do what?
almost complete penetration
what gives off a higher REM? X-ray of alpha particle?
alpha particle (20X that of x-ray)
radon radiation is in what form?
alpha particles - 2nd leading cause of lung cancer
Quantum detection Efficiency (QDE) of intensifying screens is what
amount of X-ray that can be absorbed and the amount of photons that can be emitted
electron binding energy is?
amount of energy required to overcome the electron binding force
Ci (Curie) unit quantifies?
amount of radioactivity given a certain sample
What attracts electrons from the cathode filament when the high voltage circuit is activated?
anode -positive electrode Two designs: -Stationary -Rotating
A manifestation seen on a film due to uneven exposure across the film is the _________________
anode heel effect - the lesser the anode angle the greater the heel effect
optimal kVp for cervical spine is?
around 70 kVp
where at sea level is cosmic radiation the most prevalent?
at the extreme poles of the earth (magnetic draw of the electromagnetic radiation) [Intensity increases 15% for every 50º increase in Latitude from the equator]
Bremsstrahlung interactions
b/t projectile *e- and nucleus* (+) - breaking/*slowing* down - *closer to nucleus* - loss of E is converted to X-Rays [stronger] - *farther*: less E loss [softer]
no characteristic x-rays are present in the beam, they are all [100%] Bemsstrahlung
below 70 kVp
The smaller the *effective* focal spot size, the _________________ ________________ of the radiograph
better quality
where are grids placed?
between the patient in the film
when an electron moves from an outer shell to an inner shell what happened to the energies?
binding energy: increases potential energy: decreases
what tissue has the most photoelectric effect in the body?
bone
negative of crossed pattern grids (perpendicular)?
cannot use tube tilt - cleans more scatter than linear
The intensity of the beam is greatest toward the?
cathode side.
what is the secondary radiation caused by photoelectric effect?
characteristic radiation
SuperTech is a type of?
chart with a slide rule device
explain Manifest Image in regard to X-ray Film Processing
chemical processing of the film - the build up of silver atoms is further developed into a silver grain that now becomes visible in the film as a tiny black grain of silver
kVp relative to Compton scatter?
controls balance b/t "Scatter & Absorption' - high kVp = less absorption [less PE] - more scatter [Compton effect]
what does a lot of scatter(Compton) do to a film?
creates fog and decreases contrast
Thick body part does what to density?
decrease film density = increase mAs.
attenuation is?
decrease in energy of the primary ray as it passes through the body
What should you do to mAs when using a new x-ray film and it is too dark [OD too high] on the same settings of the old film?
decrease mAs maintain kVp
Increase in SID does what to magnification?
decrease magnification
Overall, as kVp increases, Compton and PE do what?
decrease overall (less pt. dose)→ but relative portion of Compton scatter ↑ → decrease in contrast
To maintain density, Decreased distance (SID) requires?
decreased mAs
Absorption by heel of target results in?
decreased x-ray intensity on anode side of beam
As the target angle decreases, the effective focal spot size?
decreases
Decreased kVp does what to optical density?
decreases
Increased development time does what to contrast?
decreases contrast [BLUE]
increasing the focal film distance [SID] does what to the optical density?
decreases it (white)
Decrease in OID does what to magnification?
decreases magnification
A 15% decrease in kVp =
decreasing the OD by ½.
The *faster* the FILM/SCREEN speed system, the more sensitive it is to?
density
direct exposure films are used when?
dentistry, mammography, high detailed needs as in fascial bones
If there are more electrons attracted to the anode what is the speed?
e- move faster to anode
x-rays and gamma rays are what kind of radiation?
electromagnetic and ionizing
Static electricity:
electrons at rest building up on one object and transferring to another by *static discharge*
Dynamic electricity:
electrons in continuous motion in a circuit.
The cathode part of the X-ray Tube is the source of?
electrons to produce x-rays - has a filament and focusing cup
Projectile electrons are
electrons traveling from cathode to anode
photographically sensitive part of the composite film is?
emulsion (may be double sided or single sided)
single emulsion film and a single cassette are used for?
extremity films - gives high detail
what kind of tissues cause more scatter?
fat and water-based tissue
The __________________ in the Tube is a coil of thoriated tungsten wire 1.5-2 mm in diameter
filament [dual filaments: Large/Small]
mA Controlled by
filament circuit and controls how much current will flow into the filament, which is directly related to # of electrons at the filament
backscatter causes what?
film fog
film speed is aka?
film sensitivity
Lower energy x-rays are determined by
filtration used
Anode rotation allows for a continual cooler surface and a broader distribution ring of the focus beam called a?
focal track
most important device to reduce scatter?
grid: chiros usually use 10:1/ 12:1
narrow (short) latitude film is for what?
high contrast
Benefits of Tungsten Filaments (Cathode)
high melting point Atomic #74 does not vaporize easily
Film that is *too dark* has a
high optical density = over exposed = over penetrated.
In EM radiation, if you have shorter wavelength then you have _________________ energy
higher (higher frequency)
*mAs 50% rule*
if you need to seriously *darken or lighten a film* we need to either double mAs or reduce it by half
the greatest binding energy is found where?
in the K ring of the atom (closest)
Distortion in Shape is due to?
inaccurate alignment of the central ray with the part being imaged on the film. - elongation/foreshortening
*Compton scatter* is?
incident of X-ray interacting with the OUTER shell electrons THEN - *ends up deflecting* → lower energy [decreases image contrast]
Decreased development time does what to contrast?
increase contrast [RED]
Thinner body part does what to film density?
increase film density = decrease mAs.
Decrease in SID does what to magnification?
increase magnification
When you decrease the focal spot size you?***
increase sharpness & increase recorded detail
When you increase the focal spot size you?***
increase unsharpness & decrease in recorded detail
Slower film/screen speed correlates with a
increased mAs
To maintain density, Increased distance (SID) requires?
increased mAs
Increased kVp does what to optical density?
increases
decreasing the focal film distance [SID] does what to the optical density?
increases in density (black)
Increase in OID does what to magnification?
increases magnification
increased tissue thickness does what to the contrast?
increases scatter, decreases contrast
the reflective layer in intensifying screen does what?
increases speed
increasing the air gap does what to contrast?
increases, but causes magnification too
what radiation is more dangerous?
ionizing
particulate radiation and electromagneticradiation can be what 2 kinds?
ionizing and non-ionizing
Pulsating Direct Current
is not maintained consistently as voltage rises and falls - xray tube uses direct current
characteristic radiation is?
is the radiation released when an *outer shell electron falls into an inner shell* spot after that one has been *ejected* - the amount is the difference between the two energies
main controller of radiographic contrast?
kVp
The only factor that controls quality of beam =
kVp We want to keep kVp constant and play with mVp
Line-voltage Compensator LVC deals with?
keeps voltage consistent - Adjust voltage to precisely to 220V - Incoming voltage varies by as much as 5% up to 10% by law - Automatic in newer machines
ionizing radiation has the ability to do what?
knock out an orbiting electron Causing an imbalance in the atoms number of electrons or ionizing it.
The larger the *actual* focal spot size, the _______________ the effective focal spot size
larger
Aperture Diaphragm is a?
lead Collar placed over the Port area directly on the housing. Disadvantages: limited sizes; large penumbra effect
Soft X-rays are
less penetrating - longer wavelength & lower energy - less frequency & low energy
Small focus results in?
less penumbra and better detail
The tighter the collimation (smaller field of exposure) →
less scatter → better (increased) image contrast
All forms of Electromagnetic Radiation travel at the speed of?
light (C)
Thermoluminescent dosimeter (TLD)
lithium/calcium in plastic holder crystals heated - visible light indicates incident dose Pro: sensitive, low as 5mR, worn up 3mths, *Reusable* Con: Cost, once read info lost [no record], recalibrated each use
film that is *too light* has a
low optical density = under exposed = under penetrated. [increases mAs]
In EM radiation, if you have longer wavelength then you have __________________ energy
lower (less frequency)
Higher contrast (short gray scale) =
lower kVp - higher patient dose, but less Compton scatter
mA x time (second) = ?
mAs
Main controlling factor for the optic density of a film?
mAs (milliamperes and time)
With Grid & Density; Adding, removing or changing grids requires an adjustment in the
mAs to maintain density. if grid removed = decrease mAs
leading dose of X-rays to the bone marrow in people per year?
medical x-rays
all influencing factors on contrast are attempting to do what?
minimize scatter
The focusing cup around the filament in the x-ray tube is made of?
molybdenum - is negatively charged to condense the electron stream before it travels across the tube to the target
higher speed film allows for?
more absorption/ contrast and less time
Hard X-rays are
more penetrating - short wavelength & high energy - more frequency & high energy
Large focus results in?
more penumbra and less detail
*Screen film*
most common film in *medical imaging*, minimal pt exposure - usually double emulsion
do grids decrease patient radiation dose?
no
classic scatter on image quality is what?
no significant impact
Electromagnetic Radiation (EM) characteristics
not particles - bundles (photons) speed of light electrical/magnetic properties ionizing/non-ionizing no weight/charge
Law of Electrostatics
opposite charges attract & like charges repel - causes a centripetal force or (pulling) binding together = binding force
Resistance is the?
opposition to electron flow and is measured by Ohm - Insulators resist the flow - Conductors allow for easy flow
With Optical Density, kVp changes both?
optical density and quality (contrast) of the image
mAs with OD refers to the?
overall blackening (darkness) of the finished radiograph.
Particulate Radiation characteristics
particles all less than light speed arise from decay of radioactive atom ionizing/non-ionizing mass possibly charge
difference between particulate and electromagnetic radiation?
particulate has mass and may have charge
recumbent radiography and tissue compression devices reduce scatter how?
patient is either lying [flatten] or they are strapped to the buckey as to prevent motion and therefore scatter -compression bands
photoelectric effect contributes to what?
patient's total x-ray dose
Differential Absorption occurs because of the?
photoelectric effect [determines subject contrast on film]
electromagnetic radiation releases what?
photons of light
X-rays produced by an X-ray machine are
polychromatic
internal radiation sources?
potassium-40, carbon-14 from birth
Energy at rest
potential energy
mAs determines
quantity of x-rays [exposure Intensity] More mAs = more projectile electrons = more x-ray beams
greatest radiation source in the world?
radon gas
Current is the
rate of flow of electrons and is measured as Ampere (Amp) - 1 Amp = 1000 mA (milliampere)
Uniform Direct Current
remains continuous at peak voltage Batteries
scatter radiation is aka ?
secondary radiation
photoactive ingredient in the *emulsion layer* is ?
silver halides Silver Halides composition of X-ray Film: - *Silver bromide (AgBr)* - 90 to 99% - Silver iodide (Agl) - 1 to10% - Crystal form
In reality, the actual focal spot size is determined by the?
size of the filament [w/ angle of the target remains constant]
differential absorption
some x-ray *absorbed* in tissue and some will *pass thru* the body
cosmic radiation comes from?
space
*focused grids* must be used how?
specific focal film *distances*
spectral response to a film is referring to?
spectrum of light that is able to be absorbed
Wavelength
straight line distance of travel of one cycle
explain Latent Image in regard to X-ray Film Processing
the *undetectable change induced in the silver halide crystals* [metallic silver] - chemically processed -> Manifest Image
detector contrast is ?
the amount of contrast absorbed by the film
Intensifying screen speed is?
the amount of light photons emitted per time of exposure
Absorbed Dose
the amount of radiation absorbed by and object.
subject contrast is?
the amount of radiation absorbed by the pt
film speed is determined by ?
the amount of silver halide in the emulsion
photoelectric effect is what?
the complete absorption of an X-ray by the body (pt. dose), causing a free electron because it knocks one out of another atom
Higher energy x-rays are determined by
the kVp (kilovolt peak) as set on the Control Console.
[Terrestrial] Radon comes from?
the natural decay of uranium ordorless/tasteless
Manual Collimator beam limitation is done by?
the operator with knobs with no automatic "exposure hold" in case you forget to collimate
film latitude is?
the spectrum of rays a film can absorb
99% of kinetic E of projectile electrons is converted to?
thermal E (called Anode Heel)
Sufficient heat causes the outer shell of electrons of the tungsten to release or boil off in the filament...this is called?
thermionic emission
what are grids used for?
they are used to *decrease scatter* - made up of lead foil strips
lead vinyl blockers reduce scatter how?
they cover the part of the film that isn't in the image, it is used in extremity films
When X-raying a body part that varies in thickness, we want the anode side of the tube toward the?
thinner body area (anode = thinner body area)
Total electrical load applied to an anode is limited based on the?
tube's heat rating
Pocket dosimeter (hospital setting)
used in higher radiation area for immediate feedback, pencil shaped Pro: monitor shorter exposure periods, immediate readout, reusable, accurate Con: expensive, records need to be maintained daily, no permanent record, units can discharge - give false readings
Radiographic Contrast is the
variation in densities on the radiograph
Filters are used to remove the
very low energy, long wavelength, soft x-rays [These x-rays are too low energy to penetrate the patient and expose the film]
how do we increase Bremsstrahlung interactions?
we increase the kVp - higher avg. E - more x-ray photons (attracting more e-)
scatter radiation is?
when primary radiation is deflected and changes course
grid cut off is?
when the primary ray gets absorbed - decreases contrast of image
secondary radiation is?
when the primary ray interacts with matter creating a new electromagnetic ray
will a wide or a small field give more scatter?
wider field = more scatter
Anode Heel Effect
x-rays produced from the *anode side* of the target must go through a greater thickness of target material = decrease in the intensity of the x-ray beam on the anode side of the tube
Primary Radiation are
x-rays produced in & emitted from x-ray tube
If you increase the filament current [mA] what does ot do to the space charge?
↑ space charge →↑ in # of electrons to the anode. - Size of space charge ↑ in larger filament → can produce larger space charge → More X-rays
too high of a kVp will do what to the contrast of the film?
→ low PE → Low patient dose → low image contrast
too low of a kVp will do what to the contrast of the film?
→ more PE → High patient dose , but improves subject contrast due to less scatter & more differential absorption.
