Physics questions 4 answer the questions from the PowerPoint slides. if you answer the question from any Website just make a sign next to it so I can

Physics questions 4
answer the questions from the PowerPoint slides. if you answer the question from any Website just make a sign next to it so I can know.

Homework
MPHY 502 Diagnostic Imaging Physics Part I
Lecture 4
X-Ray Production, X-Ray Tubes and X-Ray Generators
1. Name 4 basic components of X-Ray Production
2. Name 3 stages of X-Ray Production
3. What is the function of the Cathode
4. Electrons fly from where to where in an x-ray tube?
5. What is the inherent filtration of an x-ray tube?
6. Name 5 levels of electron interaction energies
7. Describe Characteristic X-Ray generation
8. What does W stand for?
9. What are the K-Shell binding energies of:
a. Tungsten
b. Molybdenum
c. Rhodium

10. What are the K-Shell characteristic energies of common tube targets
a. Tungsten
b. Molybdenum
c. Rhodium
11. What are is differences between the K-Shell binding energy of Tungsten and the K-Shell Characteristic of Tungsten. Explain.
12. What are three components of and x-ray generator?
13. What charge is on the anode?
14. What is Thermionic Emission?
15. What is a focusing cup used for?
16. How can Grid Bias Voltage Stop electron flow?
17. What is space charge limited tube current and how is it different from emission limited?
18. Why is heat bad for an anode?
19. Name two types of Anode Configurations
20. What are the functions of the Rotor and the Stator in a rotating anode?
21. What is the anode target range in diagnostic imaging? How does this effect the spot size? Show your mathematical calculations to support your claims.
22. Define SID
23. What is Heal Effect and how can it be used to an advantage?
24. Describe how the focal spot size changes within the imaging Field.
25. Focal spot nominal size of 0.8mm, is it okay if measured it is 0.7mm (better resolution)?
26. What are the technique factors to be used when measuring the fs?
27. How many line pair/mm is a spot size of 0.6mm?
28. What is off focal radiation and what is one way to abate this?
29. What is special about a mammography x-ray tube insert?
30. What is the maximum allowed X-ray housing leakage rate?
31. What is the technique that is used when testing for housing leakage?
32. What are collimator used for?
33. What is the tolerance of collimator blades in terms of SID?
34. What is a collimator light used for and how does it work?
35. How does pulsed Fluoroscopy use grid bias?
36. What are deflections coils used for in CT?
37. What is a flying focus?
38. Name 6 ways to prolong x-ray tube life.
39. Why would one intentionally insert added aluminum to an x-ray beam?
40. If a transformer has a primary voltage of 20 and the number of primary turns is 10, secondary turns are 100 what is the secondary voltage?
41. Name three types of transformers
42. What is an isolation transformer used for?
43. What can be done to a full wave rectifier circuit to smooth out the ripples?
44. What is the benefit of a high frequency rectification?
45. How can one achieve less than 2% ripple?
46. What side of a step-up transformer does one place the switch?
47. What is a timer used for in and x-ray machine?
48. What is ABC?
49. What is AEC?
50. What is a Photo Timer
51. What is a Count Down timer used for?
52. How does one arrive at the Power Rating of an x-ray tube?
53. What considerations are used when deterring what type of x-ray tube to use?
54. How many MHU are 5.7MJ (Show your math)?
55. Explain how Quality, Quantity and Exposure are influenced by Anode tube material, Tube Voltage, Tube Current, Generator wave form and beam filtration.
56. What is the difference between Skin Exposure and Transmitted exposure when increasing the tube voltage by 20%?
57. Is beam exposure proportional to tube current? When does your answer apply?
58. Per 21 CFR 1020.30, How much beam filtration is required at 150kV?
59. Traversing 10cm of tissue 60 kV, tube current of 3.8 mAs and no filtration skin entrance dose is 264 microGy, with 0.2mm Cu + 1mm Pb tube current of 8.8mAs Skin entrance dose is 123 microGy. Output image equivalent signal remains the same. Why?
60. What is the main reason to use a cleaner (less percent ripple) generator wave form?
61. Extra Credit: label the un-labeled peak in slide number 9 of Lecture 4 Diagnostic Imaging Physics
MPHY-501

Bushberg Chapter 6
X-Ray Production, X-Ray Tubes and X-Ray Generators

During the next two years you will learn the basics of Diagnostic Imaging. Ultimately after this period you will enroll in a Medical Physics Residency Program and finally take the Board examination that, once you pass, will certify you as a medical physicist.
1

Basic Components
X-Ray Tube Insert
Electron Source
Medium for Acceleration (vacuum)
Electron Rich Target
X-ray Generator
Voltage Source to Create Potential Difference
Current
Exposure Timer
Tube Housing
Protective Shielding
Cooling
Tube Port
Filters (Beam Quality)
Collimators

X-Ray Production Process
Stage 1: Heat
Heat is required to boil electrons off of the Cathode
Stage 2: Acceleration
A potential difference (voltage) is placed across the Cathode and Anode
Stage 3: X-Ray production
Accelerated electron collides with the Anode (the Target)
Various atomic and nuclear interactions occur causing:
The initial accelerated electron to decelerate and give off x-rays
Electrons from target to be:
Ejected from targets atoms giving off x-rays
Change energy levels (orbits) on the targets atoms, giving off x-rays
Nuclear Collision
Electron capture (or similar event) causing total loss of electrons kinetic energy, giving off a g-Ray

e-
e-
e-
e-
e-
e-
e-
e-
e-
e-
e-
e-
e-
e-

e-
e-
e-

ANODE
+
Focusing Cup
Bias Voltage
Heater
+ High Voltage –
e-
e-
e-
e-
e-
e-
e-
e-
e-
e-
e-
e-
e-
X-Ray
X-Ray
X-Ray
120,000 Volts

CATHODE
*Focusing Cup is Shaped like the letter C and Cathode starts with the Letter C

Concept
Kinetic Energy of Electrons are Transferred to X-Rays
Several types of electron interaction x-ray spectrum is continuous

0
20
40
60
30
50
70
80
90
10
Relative Output
Energy (keV)

Average Energy is 1/3 to 1/2 Maximum Energy
Filtered Bremsstrahlung Spectrum
Unfiltered Bremsstrahlung Spectrum
Filtration:
Objects like glass x-ray tube
Other objects purposely placed in beam like aluminum
Ratio of Radiative (Bremsstrahlung) energy loss to collisional energy loss
=
From 0 to 150keV

Several Levels of
Energy Interactions 0 – >.5MeV
Bremsstrahlung radiation happens when electro changes direction this in order to balance the energy equation
Conduction band and Fluorescence band electrons
Inner shell electron interactions
Nuclear Attraction
Nuclear Absorption

Energetic Interactions
+
n
+
n
+
n

E0

l2

l1

Esc
q
Compton Electron
(Ee-)
Compton

e-

e-
e- + p = n + g
Non Schell Electrons

Bremsstrahlung
Increasing Energy
Decreasing Energy

e-

7

Characteristic X-ray generation
+
n
+
n
+
n

X-Ray emitted
Due to electrons
energy shell change

Ejected K-Shell elecrton
Incoming Electron
Rebound Electron
Adjacent shell electron filling in

8

W, 90keV, Characteristic Spectrum

0
20
40
60
30
50
70
80
90
10
Relative Output
Energy (keV)

Filtered Bremsstrahlung Spectrum
Ka1
Ka2
Kb1
Extra Credit:
Name this peak

Shells and Subshells Filling

Shell name Subshell name Subshell max electrons Shell max electrons

K 1s 2 2

L 2s 2 2 + 6 =8

2p
2p1/2
2p3/2 6

M 3s 2 2 + 6 + 10 =18

3p
3p1/2
3p3/2 6

3d
3d1/2
3d3/2 10

N 4s 2 2 + 6 +10 + 14 =32

4p
4p1/2
4p3/2 6

74 W
69.525
12.100
11.544
10.207
2.820
2.575
2.281
1.872
1.809
594.1
490.4
423.6
Element
K 1s
L1 2s
L2 2p1/2
L3 2p3/2
M1 3s
M2 3p1/2
M3 3p3/2
M4 3d3/2
M5 3d5/2
N1 4s
N2 4p1/2
N3 4p3/2

10

Binding Energies and Characteristic Shell Edges
Electron Binding Energies keV of Common X-Ray Tube Targets

Electron Shell Tungsten Molybdenum Rhodium

K 69.5 20.0 23.2

L 12.1
11.5
10.2 2.8
2.6
2.5 3.4
3.1
3.0

M 2.8
1.9 0.5
0.4 0.6
0.2

K-Shell Characteristic X-Ray Energies (keV) of Common X-Ray Tube Targets

Shell
Transition Tungsten Molybdenum Rhodium

Ka1 59.32 17.48 20.22

Ka2 57.98 17.37 20.07

Kb1 67.24 19.61 22.72

Basic Components
X-Ray Tube Insert
Electron Source (Cathode)
Medium for Acceleration (vacuum)
Electron Rich Target (Anode, can be a rotor/stator or fixed)s
X-ray Generator
Voltage Source
Potential Difference,
Mammography 25-40keV,
Other imaging 40-150keV
Current
Fluoroscopy 1-5 mA in continuous mode, 10-50mA in pulsed mode
Projection Radiography 50-1,2000 mA,
1mA = 6.25 X1015 electrons/sec
Exposure Timer
In projection Radiography typically < 10ms Tube Housing Protective Shielding Cooling Tube Port Filters (Beam Quality) Collimators Many times the product of Tube current and exposure time are combined into one unit: milliampere Seconds (mAs) Cathode The Cathode is the negatively charged electrode in the x-ray tube Combination of: filament focusing cup Filament receives ~10-Volts and up 7 ampere Most x-ray tubes have two filaments, one small, one large Each filament is placed into its own machined focusing cup One end of filament may be connected to or insulated from the focusing cup The other end of the filament is definitely insulated from the focusing cup Only one of the two filaments is energized at any given time Current from the filament circuit heats a filament, which releases electrons by thermionic emission Focusing Cups At the top are typical electron distributions incident on the target anode (the focal spot) for the unbiased and biased focusing cups. Application of 4,000 V on an isolated focusing cup completely stops electron flow, even with high voltage applied on the tube; this is known as a grid biased or grid pulsed tube The focusing cup shapes the electron distribution when it is at the same voltage as the filament Isolation of the focusing cup from the filament and application of a negative bias voltage ( .100 V) reduces electron distribution further by increasing the repelling electric fields surrounding the filament and modifying the electron trajectories Tube Current Vs. Filament Current Dependence of approximately kV1.5 For tube voltages 40 kV 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. Anodes Heat destroys anodes Damaged Anode produce fewer x-rays This requires more current that then causes more heat https://www.spellmanhv.com/en/Technical-Resources/Application-Notes-X-Ray-Generators/AN-02 Anodes Tungsten 90%/Rhenium10% alloy is good choice due to heat profile W Melting Point = 3,422C = 3,695K = 6,192F = (darn hot) To prevent heat damage the duration of x-ray production is limited Other Anodes are used to take advantage of characteristic x-rays Molybdenum Rhodium See Chapter 8 Essentials of Medical Physics (Third Edition), Bushberg, et.al. Anode Configurations Fixed Dental Mobile devices Some Portable Fluoroscopy Rotating Comprises most devices for heat management reasons Can withstand higher intensity production Rotation speeds 3,000 3,600 RPM low speed 9,000 10,000 RPM High Speed System is designed to not allow electron flow until anode is at full speed This is why these systems require one or more seconds before exposure button is pushed For an excellent description of rotating-anode failure modes see: https://www.spellmanhv.com/en/Technical-Resources/Application-Notes-X-Ray-Generators/AN-02 Simple Fixed Anode The anode of a fixed anode x-ray tube consists of a tungsten insert mounted in a copper block. Heat is removed from the tungsten target by conduction into the copper block. Rotating Anode The anode of a rotating anode x-ray tube is a tungsten disk mounted on a bearing-supported rotor assembly. The rotor consists of a copper and iron laminated core and forms part of an induction motor. Stator, which exists outside of the insert. A molybdenum (poor heat conductor metal) stem connects the rotor to the anode to reduce heat transfer to the rotor bearings (bottom) Focal Spot The anode (target) angle, , is angle of the target surface wrt the central ray. The focal spot length, as projected down the central axis, is foreshortened, according to the line focus principle (lower right). Effective Focal length = Actual Focal Length X sin q Diagnostic Imaging: 7o < q < 20o Commonly 12o < q < 15o Focal Length Examples EXAMPLE 1: Actual anode focal area is 4 mm (length) by 1.2 mm (width). Anode angle is 20-degrees, What is projected focal spot size at central axis position? Answer: Effective length = actual length sin = 4 mm sin 20 degrees = 4 mm 0.34 = 1.36 mm; therefore, the projected focal spot size is 1.36 mm (length) by 1.2 mm (width). EXAMPLE 2: If Example 1s anode angle is reduced to 10 degrees and actual focal spot size remains same, what is projected focal spot size at central axis position? Answer: Effective length = 4 mm sin 10 degrees = 4 mm 0.174 = 0.69 mm; thus, the smaller anode angle results in a projected size of 0.69 mm (length) by 1.2 mm (width) for the same actual target area. CATHODE e- e- e- e- e- e- e- e- e- e- e- e- Heal Effect Effective Focal Spot: Terminology Anode Side Cathode Side Heal Effect Anode Anode Side of the Anode Cathode Side of the Anode Cathode Side of Imaging Plane Anode Side of Imaging Plane More Photons Fewer Photons Heal Effect is Less Prominent at large Source Image Distance (SID) Source distance is measured from focal spot center of anode Image distance measured from center of imaging plane SID Differences in Projected Focal Spot Size Within the Imaging Field Anode Side Cathode Side NEMA Standards for Focal Spot Sizes There are three limits, small, medium and large focal spots Focal spots can be larger than nominal size but NOT SMALLER. For focal spots Must be done at 74keV and 50% of max mA for each spot size (remember that many cathodes have two elements) fs < 0.8 mm + 50% 1.5mm fs 0.8mm +40% fs > 1.5mm +30%

Start your Spread Sheets!!!!!!

Focal Spot Size Focal Spot Size

Nominal Size Tested Size PASS/FAIL Passing Criteria

fs < 0.8 mm + 50% 1.5mm fs 0.8mm +40% fs > 1.5mm +30%

4 Ways to test focal spot size
Pin hole
Typically 10micrometer to 30micrometer diameter hole (highly attenuating)
Slit
Must be placed in two different directions
Along the anode cathode direction
Perpendicular to the anode cathode direction
Star
Bar

How many lines/mm is a resolution of 0.6mm?

A line pair consists of a dark line and a bright line.

So if one line is 5 microns wide, then a line pair will be 10 microns wide and there would be 1 mm/10 microns = 100 line pairs per millimeter.
Line pairs per millimeter =

Therefore:
Spot Size (in millimeters) = 1mm/(2* lp/mm)

Off-Focal Radiation
Electrons scatter off or anode are re-accelerated to anode but not to the focal spot
Give low intensity x-rays about the face of the anode
Many off-focal radiation are caught by the collimator
Grounded metal X-ray tube enclosures attract many of the scattered electrons thus keeping them from returning to anode
Off-Focal Radiation Distribution
Hot Spots

Description: X-Ray Tube Insert
Contains
Cathode
Anode
rotor assembly
sealed support structures
glass or
metal
enclosure under a high vacuum
Gas molecules leach from internal structures
Getter eliminates those molecules
Note1: Getter is a deposit of reactive material placed inside a vacuum system, for completing and maintaining the vacuum. When gas molecules strike the getter material, they combine with it chemically or by absorption. Thus the getter removes small amounts of gas from the evacuated space.

https://en.wikipedia.org/wiki/Getter#:~:text=A%20getter%20is%20a%20deposit,gas%20from%20the%20evacuated%20space.

Note 2:
Mammography Inserts include a beryllium (z=4) window in the port specifically to minimize the the absorption of low energy x-rays.

Other ports (non mammography) use the same material as the tube itself.

Description: X-Ray Tube Housing
Between Insert an Housing is Oil, provides:
Electrical insulation
Heat conduction (cooling)
Expansion bellows (for the expansion of oil as it heats up)
Overtemperature (senses oil temperature) switch stops x-ray production
CT and Interventional Fluoroscopy (high duty cycle) Housings
may have built-in heat exchangers (for cooling)
Shielding for scattered leakage (x-rays not in direction of imaging)
21 CFR (code of federal regulations) 1020.30 requires
leakage less than 100 mR/hr (0.88 mGy/hr) @ one meter from focal spot
Leakage must be tested at maximum rated kV (typically 125kV – 150kV) and highest possible current typically 3mA to 5mA
Equipment software/hardware should not allow operation at above max rated kV
Testing with
Area survey dose rate meter

Collimators
Adjust size and shape of x-ray field from tube port
Parallel opposed shutters
rectangular FOV for plain film
other shapes available (Fluoroscopy, hexagonal Iris)

Collimator
Assembly
Lead insert Shield
Collimator
Assembly
Collimation must be within 2% of SID
Example: SID = 100cm
Collimation must be:
100cm 2cm, 40 0.8
20CFR1020.31
Positive Beam Limitation (PBL)
Automatically senses film cassette size and adjusts so that beam cannot exceed cassette size

Changeable Filter
Al, Cu, Moly, Rho,

Special Tube Designs
Pulsed Fluoroscopy
Pro: 4kV grid bias keeps electrons in cloud by cathode when off electrons rapidly fly toward anode allowing rapid pulse times.
Con: Costs much more $$$$$
Mammography
Special tube output port (Beryllium instead of glass or other metal)
Potentially Different Targets (molybdenum, rhodium, tungsten)
Smaller Focal Spot (0.3mm, 0.1mm)
Grounded Anodes
CT
High instantaneous output, high heat load, Rapid Cooling
Rapid Tube Rotation about Gantry. More than 200RPM!!! https://www.youtube.com/watch?v=aBlJebipLgM

CT Advanced X-Ray Tube Features:

Anode & planar cathode within rotating vacuum enclosure.

Bearings mounted outside vacuum enclosure.

Deflection coils magnetically direct electron beam to specific areas on the target.

Circulating oil rapidly removes excess heat from the anode.

Flying Focal Spot: Electron beam rapidly deflects between two focal spots

How to Maximize X-Ray tube life
Hold ready state only as long as needed (dead man 2-stage switch)
Holding on keeps current in filament damages filament
Evaporated tungsten deposits on inside of x-ray tube (not good)
Use lower tube current and longer exposure times (when reasonable)
Avoid extended repeat operation at high technique
Can etch anode and cause several problems lower photon output etc.
Do not make high mA exposure on cold anode
follow manufactures recommendations
Limit Rotor start & Stop operations
Allow 30 to 40 seconds between exposures

Filtration
Inherent Filtration
X-ray Tube
Glass (SiO2) and Aluminum have similar attenuations, ZSiO2=14, Zal = 13
Glass and Aluminum attenuate all x-rays below 15 keV
Port
Housing Oil
Collimator Assembly
Mirror
Added (beam quality filters)
Intended to eliminate low energy x-rays that add to dose but not image
Metal
Plastic

X-Ray Generators Voltage Needs
Medical Facility Voltage runs in multiples of 120V up to 480V
X-ray Voltages are between 10 kV and 175 kV
Transformer is required to step-up the voltage
Transformers work on the principal of electromagnetic induction
Briefly an changing magnetic field in the presence of a conductor induces flow of current in that inductor. And flowing current in an inductor produces a magnetic field about the conductor (right hand rule)
Therefore a time varying voltage current in one conductor generates a time varying magnetic field about the conductor, when that conductor is placed adjacent another conductor current is induced in the second from the first hence current is transformed from one to the other.
The Law of transformation is:

Where:
Vp is voltage in primary coil, Vs is voltage in secondary coil
Np is number of turns in primary coil, Ns is number of turns in secondary coil
Np = 5
Ns = 10
Vs = 2Vp

Transformer Nomenclature| Ideal Transformer

Ideal Transformer: Power Input = Power Output

Power is measured in watts
1watt = 1ampre * 1volt
P = I * V
Where:
P = power
I = current
V = Volts
Remember:
Pin = Pout
Therefore:
Vin * Iin = Vout * Iout

In Reality:
Pin = efficiency constant * Pout
Some number between zero and one
Loss due to heat?

Rectifiers

https://www.electronics-tutorials.ws/diode/diode_6.html

Full Wave Rectifier Circuit
Full-wave Rectifier with Smoothing Capacitor

5uF Smoothing Capacitor

50uF Smoothing Capacitor

Note Capacitor values impact on Smoothing
V=Q*C

Volts = charge (coulombs) * capacitance (Farads)

High Frequency Production and Rectification

5uF Smoothing Capacitor

50uF Smoothing Capacitor

Step 5
Step 1
Step 6
Step 2
Step 7
Step 4
Step 3
Step 8

Low Frequency
Rectification
Hi Frequency
Rectification
Production of
Hi Frequency

Voltage Ripple

% voltage Ripple = X 100

Switches
High-Frequency Inverter on primary side of HV transformer because of low Voltage

Alternately Grid Control can stop x-ray production through biasing the grid (-4,000 V) to stop electron acceleration to target anode.
Grid Control is the fastest switching method

Timer(s)
Old equipment used mechanical timers
New equipment uses:
digital timers
Automatic Brightness Control (ABC, used in spot film devices)
Automatic Exposure Control (AEC, Fluoroscopy devices) also called Photo timer
Back-up Count Down Timer
Used in the case that the ABC or digital timer fail so exposure is terminated
Fluoroscopy Systems have another timer to warn user that the tube on time has increased (more on this in Fluoroscopy section)

ABC and AEC automatically adjust kV and mAs to achieve correct exposure to detector for optimal image

Phototimer/Automatic Exposure Control (AEC)
AEC detectors measure the radiation incident on the detector and terminate the exposure according to a preset optical density or signal-to-noise ratio achieved in the analog or digital image.

Chest cassette stand and the locations of ionization chamber detectors are shown. The desired signal to the image receptor and thus the signal-to-noise ratio may be selected at the operator’s console with respect to a normalized reference voltage.

Anti-Scatter Grid

Power Ratings, Heat Loading & Cooling
Power = Volts times Amperes (P= VI)
The Power rating (two ways to achieve)
= maximum power an x-ray generator can deliver
or
= maximum power a focal spot can accept
Testing is done for 0.1 seconds @ 100 kV
Example: a generator that can deliver 800 mA of current @ 100kV in 0.1 seconds has a power rating of:
0.8 Amperes X 100000 volts = 80,000 Watts or 80kW

When recommending an x-ray generator type the intended use should be taken into consideration. Power ratings can help. Duty cycle is many times required before recommendation can be made.

Heat Loading
The Heat Unit
The Heat Unit is labeled HU this is an unfortunate label because the CT x-ray linear attenuation units are translated into Hounsfield Units also labeled HU
Energy is in Joules where 1 Joule = 1 Watt * 1 Second

HU (Single Phase) = Voltspeak * Amperes * Seconds
HU (Single Phase) = kVpeak * mA * Seconds
HU (Three Phase) = 1.35 * (kVpeak * mA * Seconds)
HU (High Frequency) = 1.4 * (kVpeak * mA * Seconds)
Energy (Joules) = VoltsRMS * Amperes * Seconds
Energy (HU) = 1.4 * Energy (Joules)

Danger Ambiguation Situation
Danger Notice Vpeak & VRMS are used here

Anode Heating and Cooling Chart
Energy (Watts), HU (Joules), Joules = Watt Seconds
Therefore: Energy = HU/s = Volt Amps = Watts

CT scanner anode heating and cooling curves. Power input curves (2 kW 28kW) determined by kV and mA settings during continuous x-ray tube operation over time. Cool down curve shows the rate of cooling and indicates faster cooling at higher anode heat loads (temperature). In this example the maximum capacity is 5.7 MJ. For low power inputs, heating and cooling rates eventually equilibrate and reach a steady state, as shown for the 2, 4, and 8 kW curves.
4kW
Quesiton:
5.7 MJ = how many MHU?

Factors Effecting X-Ray Emissions
Quality
Quality = penetrability of x-ray Beam
Higher HVL (see Ch 3)

Quantity
# of photons comprising the beam

Exposure
Exposure Energy Fluence of Beam
Anode Target Material
Tube Voltage
Tube Current
Beam Filtration
Generator Waveform

Anode Target Material
Higher Z = more bremsstrahlung radiation
Characteristic x-rays depend on target material

Tube Voltage
Skin Exposure kV2
* mAs1 = * mAs2

Higher kV increases efficiency of x-ray production (more possible photon producing events)
Higher kV penetrates tissue better (higher beam quality)

Transmitted Exposure kV5 (what a detector may see through 20cm tissue):

Tube Current
Beam Exposure is to Tube Current at a given kV and Filtration

Beam Filtration: 21 CFR 1020.30

Designed Operating Range Measured x-ray tube voltage Minimum HVL (mm of Aluminum)

<51kV 30 0.3 40 0.4 50 0.5 51-70 kV 51 1.3 60 1.5 70 1.8 >70 kV 71 2.5

80 2.9

90 3.2

100 3.6

110 3.9

120 4.3

130 4.7

140 5.0

150 5.4

Spread Sheet Lookup table

Tube Filtration
and
Skin Entrance Dose

10cm PMMA (60kV) 20cm PMMA (80k) 30cm PMMA (100kV)

TUBE
Current DOSE
(mGy) TUBE
Current DOSE
(mGy) TUBE
Current DOSE
(mGy)

mAs %D Dose %D mAs %D Dose %D mAs %D Dose %D

3.8 0 264 0 6.8 0 1,153 0 14.5 0 4,827 0

5.0 32 188 -29 8.2 21 839 -27 16.5 14 3,613 -25

6.2 63 150 -44 9.3 37 680 -41 17.6 21 2,960 -39

8.8 132 123 -53 11.2 65 557 -52 19.8 37 2,459 -49

Filtration

0 mm Al

2 mm Al

0.1 mm Cu + 1 mm Al

0.2 mm Cu + 1 mm Al

OUTPUT DIGITAL IMAGE EQUIVALENT SIGNAL . TUBE FILTRATION, MEASURED CHANGES IN mAs, AND SURFACE DOSE (Gy)
Filtration Causes:
1) acquisition technique much higher,
2) entrance dose much lower
3) no loss of image quality for digital imaging
Used Photo Timed Mode

Generator Wave Form
Affects the quality of the emitted x-ray spectrum. For the same kV, a single-phase generator provides a lower average potential difference than does a three-phase or high-frequency generator. Both the quality and quantity of the x-ray spectrum are affected

Output intensity (bremsstrahlung) spectra for the same tube voltage (kV) and the same tube current and exposure time (mAs) demonstrate the higher effective energy and greater output of a three-phase or high-frequency generator voltage waveform (5% voltage ripple), compared with a single-phase generator waveform (100% voltage ripple)