1. The Relationship Between Non-Removable and
User-Selectable Filtration on Dose at Different Depths
Michelle Ferderbar, Hamid Khosravi, M.Sc., Ph.D, MCCPM
Department of Medical Physics and Radiation Sciences | 1280 Main Street West | Hamilton, Ontario | L8S 4L8
Acknowledgements
Many thanks are extended to Mrs. L. Koziol, Mrs. S.
Charbonneau, Mrs. J. Pacheco, and Mrs. J. Keczan for
their continued time and support.
References
1. Brosi P, Stuessei A, Verdun FR, Vock P, Wolf R. Copper filtration in pediatric digital X-ray
imaging: its impact on image quality and dose. Radiol Phys Technol (2011) 4, 148-155. DOI:
10.1007/s12194-011-0115-4
2. Hamer OW, Sirlin CB, Strotzer M, Borlsch I, Zorger N, Feuerbach S, Volk M. Chest
radiography with a flat-panel detector: image quality with dose reduction after copper
filtration. Radiol (2005) 237, 691-700. DOI: 10.1148/radiol.2372041738
3. Hansson B, Finnbogason T, Schuwert P, Persliden J. Added copper filtration in digital
paediatric double-contrast colon examinations: effects on radiation dose and image quality.
Eur Radiol (1997) 7, 1117-1122.
4. Hess R & Neitzel U. Optimizing image quality and dose in digital radiography of pediatric
extremities. 2011.
5. Shrimpton PC, Jones DG, Wall BF. The influence of tube filtration and potential on patient
dose during x-ray examinations. Phys Med Biol (1988) 33, 10:1205-1212.
6. ICRP Publication 73, Radiological protection and safety in medicine. Ann. ICRP (1996) 26
(2)
7. DISC. (2014) DR RadChex Plus. Retrieved from http://www.disc-imaging.com/dr-radchex-
plus.html. Accessed 18 July 2015.
8. Willis, CE. Strategies for dose reductions in ordinary radiographic examinations using CR
and DR. Pediatr Radiol (2004) 34(Suppl 3): S196-S200. DOI: 10.1007/s00247-004-1269-6
Introduction
In diagnostic radiography, the ALARA (As Low As
Reasonably Achievable) principle is always being
considered.[6] There are many methods to reduce the
amount of dose received in a radiographic examination in
addition to a machine’s non-removable filtration, and one of
those methods is via user-selected filtration. [3, 4, 5]
Filtration works by hardening the x-ray beam so that only
the x-rays with the greatest amount of penetrating power
will be used to form the image, thereby leaving no weak
radiation to be absorbed by the patient thus reducing the
amount of dose to the patient. [5]
This study aims to demonstrate how much user-selected
copper filtration (Cu) reduces the dose at different depths of
a simulated patient with PMMA while using low-energy
radiation. Through use of the Cu of Siemens and GE
general radiography machines, the doses will be compared
with added filtration to inherent, or non-removable, filtration.
This project will aim to explore the relationship between the
dose to the different depths of a patient’s body and while
comparing user-selectable and non-removable filtration.
Abstract
Introduction: This study aims to determine the relationship
between non-removable filtration and user-selectable
copper filtration (Cu) on dose at various depths of skin.
Background: Current research demonstrates Cu can
reduce dose by 45-55% with polymethyl methacrylate
(PMMA) at 750 mm thickness or greater only. [1, 2, 3, 4, 5]
Materials/Methods: This study used the GE XR/d 2X
Radiography machine, the Siemens Multix Fusion
Radiography Machine, PMMA depths of 0, 1, 3, 6, 11, 17,
26, 37, 50, 70, 90, 130, 180, and 200 mm, and the DISC
RadChex Plus dosimeter in µGy. Exposures were taken at
50, 70, 90, and 121 kV at 10 mAs with total filtration, 0.1
mm Cu, 0.2 mm Cu, and 0.3 mm Cu for all depths.
Results: The findings demonstrated that the greatest dose
reduction occurred with 0.3 mm Cu, with reductions of up to
91%, 77%, 65%, and 54% at 50, 70, 90, and 121 kV,
respectively. GE had lower initial dose reductions in
comparison to Siemens due to greater inherent filtration.
Conclusion: Therefore, to abide by the ALARA principle,
radiographers should utilize user-selectable Cu to provide
significant dose reduction. Further research should be
conducted to view the effect of Cu on image quality.
Materials and Methods
The first x-ray machine used was a GE XR/d 2X
Revolution Radiography Suite installed in 2010 with user-
selectable Cu of 0.1, 0.2, and 0.3 mm Cu, inherent
filtration of 1.9 mm Al at 70 kV, and total filtration of 3.1
mm Al at 80 kV. The second x-ray machine used was a
Siemens Multix Fusion Radiography Suite installed in
2014 with user-selectable Cu of 0.1, 0.2, and 0.3 mm Cu,
inherent Filtration of 1.0 mm Al at 70 kV, and total filtration
of 2.9 mm Al at 80 kV. These were used with various
slabs of PMMA to provide depths of 0, 1, 3, 6, 11, 17, 26,
37, 50, 70, 90, 130, 180, and 200 mm. The dose was
calculated with a DISC RadChex Plus meter with
dosimeter which featured a 6 cc Radcal air chamber to
+/- 2% to calculated measured entrance dose in µGy. [7]
Results and Discussion
Overall, the greatest dose reductions were observed
between the depth of 0-26 mm using 0.3 mm Cu. It
appears that at all of the depths at all of the techniques,
the dose reduction is initially drastic and tapers off as the
depth increases. This is due to the fact only the hard
beam remains remains by that point and is able to nearly
fully penetrate to that depth. There appears to be an
inverse relationship between the depth of PMMA and
dose reduction; as the depth increases, the dose
reduction is not as drastic between each graduation.
Brosi et al. and Willis described a proportional decrease
in dose to the kV value, where as the kV increased,
there was a greater increase in dose reduction. [1, 8]
There is a generally linear trend that appears when
observing the dose reduction through the greater
depths.
Therefore, it was found that the use of Cu is an effective
way of reducing dose at various depths of the body,
especially at the depths of 0-26 mm with 0.3 mm Cu
providing the greatest dose reduction. Solely using inherent
filtration did not provide significant dose reduction. These
results fit into the literature as there exists no study that
observes the differences in dose in such minute
graduations and tissue depth while using Cu. The findings
suggest that technologists should utilize Cu when
completing examinations to follow ALARA. Further research
should consider the effect of SSD and filters on dose
reduction, the effect of filtration on image contrast, the
effect of different filters on dose reduction, and the
combined use of grids and filters on dose reduction.
Figure 1. This figure demonstrates
the set-up used for the experiment,
including the x-ray tube, Cu, beam,
PMMA, and the RadChex Plus meter.
0
0.05
0.1
0.15
0.2
0.25
0 1 3 6 11 17 26 37 50 70 90 130180200
Dose(µGy)
PMMA Depth (mm)
50 kV at 10 mAs
0.0 mm Cu
0.1 mm Cu
0.2 mm Cu
0.3 mm Cu
0
0.1
0.2
0.3
0.4
0.5
0.6
0 1 3 6 11 17 26 37 50 70 90 130180200
Dose(µGy)
PMMA Depth (mm)
70 kV at 10 mAs
0.0 mm Cu
0.1 mm Cu
0.2 mm Cu
0.3 mm Cu
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 1 3 6 11 17 26 37 50 70 90 130180200
Dose(µGy)
PMMA Depth (mm)
90 kV at 10 mAs
0.0 mm Cu
0.1 mm Cu
0.2 mm Cu
0.3 mm Cu
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
0 1 3 6 11 17 26 37 50 70 90 130180200
Dose(µGy)
PMMA Depth (mm)
121 kV at 10 mAs
0.0 mm Cu
0.1 mm Cu
0.2 mm Cu
0.3 mm Cu
Figures 3-6. These are the results from the Siemens Suite. What is plotted is the dose
determined in µGy compared to the depth of PMMA for each amount of filtration, including
0.0 mm Cu to 0.3 mm Cu. It is clear here that there is an inverse relationship between the
depth of PMMA and dose reduction, as well as a proportional decrease in dose to kV.
0
0.05
0.1
0.15
0.2
0.25
0 1 3 6 11 17 26 37 50 70 90 130180200
Dose(µGy)
PMMA Depth (mm)
50 kV at 10 mAs
0.0 mm Cu
0.1 mm Cu
0.2 mm Cu
0.3 mm Cu
0
0.1
0.2
0.3
0.4
0.5
0.6
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Dose(µGy)
PMMA Depth (mm)
70 kV at 10 mAs
0.0 mm Cu
0.1 mm Cu
0.2 mm Cu
0.3 mm Cu
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Dose(µGy)
PMMA Depth (mm)
90 kV at 10 mAs
0.0 mm Cu
0.1 mm Cu
0.2 mm Cu
0.3 mm Cu
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Dose(µGy)
PMMA Depth (mm)
121 kV at 10 mAs
0.0 mm Cu
0.1 mm Cu
0.2 mm Cu
0.3 mm Cu
Figures 7-10. These are the results from the GE Suite. What is plotted is the dose
determined in µGy compared to the depth of PMMA for each amount of filtration, including
0.0 mm Cu to 0.3 mm Cu. It is clear here that there is an inverse relationship between the
depth of PMMA and dose reduction, as well as a proportional decrease in dose to kV.
59%
81%
91%
43%
64%
77%
40%
55% 54%
27%
44%
54%
58%
80%
90%
45%
64%
75%
34%
53%
65%
28%
45%
54%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
50 kV 0.1 mm
Cu
50 kV 0.2 mm
Cu
50 kV 0.3 mm
Cu
70 kV 0.1 mm
Cu
70 kV 0.2 mm
Cu
70 kV 0.3 mm
Cu
90 kV 0.1 mm
Cu
90 kV 0.2 mm
Cu
90 kV 0.3 mm
Cu
121 kV 0.1
mm Cu
121 kV 0.2
mm Cu
121 kV 0.3
mm Cu
PercentageReduction
kV and Filtration
Percentage Dose Reduction Comparison Between GE and Siemens
GE Siemens
Figure 3. This is a comparison between the two imaging suites and the percentage dose
reduction at the different kVs and amount of Cu. Greater percentage reductions are seen at the
lower kVs due to the ease of penetrating the lower beam.
Figure 1 demonstrates the
set-up of the experiment.
The RadChex Plus meter
was placed on the surface
of the table at a source-to-
sensor (SSD) of 100 cm.
An exposure was taken at
50, 70, 90, and 121 kV at
10 mAs, with no added
filtration or thickness of
PMMA. Slabs of PMMA
were added in succession
with exposures at 0.1 mm
Cu, 0.2 mm Cu, and 0.3
mm Cu in both the GE and
Siemens Suites.
X-ray Tube
100 cm
PMMA
Cu Filter
X-ray beam
RadChex Plus
Siemens
GE
Figure 2. This graph
demonstrates the difference
in the inherent filtration
(filtration without any
added Al or any user-
selectable Cu) between the
two radiography systems. It
is clear that Siemens
consistently has a greater
dose to the skin at the lower
depths of up to roughly 50
mm, but at greater depths
the doses are fairly similar
or exact in some cases. For
example, without any
PMMA at 50 kV, the dose
calculated for Siemens was
1.553 µGy in comparison to
GE’s reading of 1.510 µGy
but at 50 mm the doses
were both 0.332 µGy.0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
0 1 3 6 11 17 26 37 50 70 90 130 180 200
Dose(µGy)
PMMA Depth (mm)
Comparison of Siemens and GE Systems'
Inherent Filtration
GE
Siemens
50 kV
121 kV
90 kV
70 kV