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Workshop on dental Cone Beam CTSEDENTEXCT
Dosimetry
of dental CBCT
![Page 2: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/2.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
deterministic
Why dosimetry?
X-rays ionizing radiation
deterministic and stochastic effects
stochastic
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Workshop on dental Cone Beam CTSEDENTEXCT
French Academies Report, 20052
2French Academies Report, 2005. La relation dose-effet et l’estimation des effets cancérogènes des
faibles doses de rayonnements ionisants.
Why dosimetry?
Cancer risk?International Commission on Radiological Protection1
1ICRP103: The 2007 Recommendations of the International Commission on Radiological Protection .
Annals of the ICRP Vol 37 (2007)
Can
cer
risk
Radiation dose
100mSv
“linear no-threshold” modelhormesis
dose
incid
en
ce
![Page 4: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/4.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
Why dosimetry?
Risk of cancer and age
![Page 5: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/5.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
Effective dose ranges and dental investigationsWhy dosimetry?
0 10000 20000 30000 40000 50000 60000 70000 80000 90000
0 0.01 0.02 0.03 0.04 0.05 0.0 6 0.0 7 0.08 0.0 9 0.1
radiotherapy
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000
0 100 200 300 400 500 600 700 800 900 1000
0 10 20 30 40 50 60 70 80 90 100
0 1 2 3 4 5 6 7 8 9 10
0 0.1 0. 2 0.3 0. 4 0. 5 0.6 0.7 0.8 0. 9 1 mSv
experimental radiobiology
cancer epidemiology
study programs low dose
medical diagnostics
A-bomb survivors
significant risk to cancer: > 200 mSv
(UNSCEAR)
LD50 humans
typical dose of
stay at space
station
typical yearly dose for commercial aircrewthyroid investigation
(I-123)
RX thorax
intraoral radiographICRP negligible dose
dose limit public
dose limit oew
bone (Tc-99m)
Total Body therapie
natural background radiation
panoramic radiograph
CT maxilla
dental CBCT
dental CBCT
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Workshop on dental Cone Beam CTSEDENTEXCT
The ICRP basis for radiation protection: patient and personnel protection policy
Basic principles: „individual related‟ ICRP 60
ALARA
Why dosimetry?The ICRP basis for radiation protection: patient and personnel protection policy
European Directive 97/43 Euratom
Hospital
radon
dose limit
Hospital
dose restriction
vs „source related‟ ICRP 103
![Page 7: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/7.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
Patient dose and technical dose characterization
Why dosimetry?
- effective dose
- skin dose
![Page 8: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/8.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
TLDs exposed in
the phantom. X-ray
energy stored
Individually
loaded into TLD
reader
Energy
released as
light when
heated
Photomultiplier
tube detects light
Patient dose and technical dose characterization
Why dosimetry?
![Page 9: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/9.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
Patient dose and technical dose characterization
Why dosimetry?
- definition of standard dose index that can be measured in a physical
phantom during a routine medical physics quality control check
- candidates:
- cfr. medical CT: Computed Tomography Dose Index,
CTDIwDLP (Dose Length Product)
DAP
- effective dose is influenced by technical parameters as mAs and FOV
CTDI
![Page 10: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/10.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
CTDIw
DLP
DAP (Dose Area Product)
Why dosimetry?
![Page 11: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/11.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
- determine conversion factors between technical quantities and effective dose:
the more dose determining factors that are included in the dose index, the more
uniform the conversion factors will be:
dose conversion factors from mAs to effective dose will be different for different
CBCTs and imaging protocols
dose conversion factors from a dose index including the influence of both mAs
and FOV can possibly be the same for different CBCTs and imaging protocols
Why dosimetry?
![Page 12: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/12.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
Why dosimetry?
Available knowledge at the start of SEDENTEXCT
• Few dosimetric studies
≠ anthropomorphic phantoms
≠ TLDs
Limited number of TLDs & CBCT devices
• No reports on scattered dose in dental CBCT
• Few studies investigating CTDI and alternative indices for
modern MSCT scanners
• No dose simulation studies for dental CBCT
![Page 13: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/13.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
• Dental CBCT dose index
• Assessment of dental CBCT dose
(adult & paediatric phantom, patients)
• Monte Carlo simulation framework for optimisation
• Personnel dose
SEDENTEXCT dosimetry
KUL Leuven, UNIMAN Manchester, NKUA Athens,
VU Vilnius, MAHOD Malmö, LTO Leeds
![Page 14: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/14.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
Measurement of the dose distribution in
anatomical phantoms and subsequent
calculation of effective dose
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Workshop on dental Cone Beam CTSEDENTEXCT
Phantom dose
Adult (Alderson) and paediatric (ATOM) phantoms
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Workshop on dental Cone Beam CTSEDENTEXCT
Phantom dose: adult
0
50
100
150
200
250
300
350
400
Effe
ctiv
e d
ose
(µ
Sv)
Effective dose for large field CBCTs
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Workshop on dental Cone Beam CTSEDENTEXCT
0
50
100
150
200
250
300
350
400
Effe
ctiv
e d
ose
(µ
Sv)
Effective dose for medium field CBCTs
Phantom dose: adult
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Workshop on dental Cone Beam CTSEDENTEXCT
0
50
100
150
200
250
300
350
400
Effe
ctiv
e d
ose
(µ
Sv)
Effective dose for small field CBCTs
Phantom dose: adult
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Workshop on dental Cone Beam CTSEDENTEXCT
Phantom dose: adult
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Workshop on dental Cone Beam CTSEDENTEXCT
Phantom dose: paediatric
0
20
40
60
80
100
120
Effective dose (µSv) for paediatric phantoms
child
adolescent
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Workshop on dental Cone Beam CTSEDENTEXCT
Conclusions• Wide dose range (~20 Sv to 400 Sv: 20-fold)
• Main contributors: thyroid gland, salivary glands, „remainder‟ (oral mucosa, extrathoracic airways)
• Clear effect of FOV size & position on effective dose
• Other differences between doses: interplay with image quality!
• Optimised (“customised”) patient dose: FOV selection based on region of interest + exposure selection based on image quality requirement
Phantom dose
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Workshop on dental Cone Beam CTSEDENTEXCT
In vivo dose measurements
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Workshop on dental Cone Beam CTSEDENTEXCT
KUL
Scanora 3D
VU
NewTom 9000
NKUA
NewTom 9000
Clinical indication # Patients Age # Patients Age # Patients Age
Implant placement 43 13-61 30 20-68 15 28-62
Orthodontic planning 4 10-13 0 / 1 13
Impacted teeth 8 10-20 43 10-83 10 18-33
Maxillofacial trauma/
tumors/ development
abnormalities
1 20 29 11-49 0 /
Sinus visualisation 4 35-60 42 22-76 0 /
Others 10 10-54 0 / 8 24-62
In vivo dose
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Workshop on dental Cone Beam CTSEDENTEXCT
In vivo dose
0
0.5
1
1.5
2
2.5
Scanora NewTom 9000 (A) NewTom 9000 (V)
Skin dose (mGy)
MIN
AVERAGE
MAX
![Page 25: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/25.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
Conclusions
• Wide range of in vivo doses due to difference in exposure and patient size
• Manual adjustment of exposure parameters ↔ Pre-set exposure protocols based on patient size ↔ Automatic exposure control
In vivo dose
![Page 26: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/26.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
Development of a standardised dose index
to characterise dose distribution in dental
CBCTs
![Page 27: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/27.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
Assessment of dose distribution
H2O PMMA
KUL
TLD
Ion chamber
UNIMAN & LTO
TLD
Film
Dental CBCT dose index
![Page 28: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/28.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
Assessment of dose distribution
Dental CBCT dose index
![Page 29: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/29.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
Scanora 3D, TLDs in „coronal‟ plane
Dental CBCT dose index
![Page 30: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/30.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
Scanora 3D, ion chamber, along z-axis
Dental CBCT dose index
![Page 31: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/31.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
TLDs, along z-axis
Dental CBCT dose index
![Page 32: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/32.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
TLDs, „axial‟ plane
Dental CBCT dose index
![Page 33: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/33.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
Dental CBCT dose index
![Page 34: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/34.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
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Workshop on dental Cone Beam CTSEDENTEXCT
Film measurements, „axial‟ plane
Dental CBCT dose index
![Page 36: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/36.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
Dose distribution → dose index definition
FOV at the
central axis
PhantomFOV off
central axis
Measuring
points
1
2 Measuring
points
FOV axis
Phantom
Dental CBCT dose index
![Page 37: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/37.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
Dose Area Product (DAP)?
Dental CBCT dose index
![Page 38: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/38.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
→ Validation of indices
Leeds Test Objects Ltd
Dental CBCT dose index
![Page 39: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/39.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
→ Validation of indices
1) Measurement of indices in practice
2) Definition of correlation factors through
Monte Carlo simulation
Dental CBCT dose index
![Page 40: Dosimetry of dental CBCT - SEDENTEXCTsedentexct.eu/system/files/Prof. Bogaerts.pdf · Dosimetry of dental CBCT. SEDENTEXCT Workshop on dental Cone Beam CT deterministic Why dosimetry?](https://reader030.vdocument.in/reader030/viewer/2022040418/5d67246b88c9931d358bbb53/html5/thumbnails/40.jpg)
Workshop on dental Cone Beam CTSEDENTEXCT
Index1
(mGy)
Index 2
(mGy)
Protocol AVG STDEV AVG
17x12 90 kV, 5 mA, 17s, 360 8.8 0.4 8.8
80 kV, 5 mA, 17s, 360 6.4 0.2 6.4
70 kV, 5 mA, 17s, 360 4.3 0.2 4.3
80 kV, 5 mA, 9s, 180 4.5 2.3 4.5
17x5 90 kV, 5 mA, 17s, 360 7.5 0.4 7.4
14x10 90 kV, 5 mA, 17s, 360 8.6 0.3 8.6
10x10 90 kV, 5 mA, 17s, 360 7.9 0.7 7.9
90 kV, 5 mA, 17s, 360 7.4 2.4 7.3
8x8 90 kV, 5 mA, 17s, 360 6.4 2.3 6.5
80 kV, 5 mA, 17s, 360 4.8 1.8 4.9
70 kV, 5 mA, 17s, 360 3.3 1.3 3.4
90 kV, 5 mA, 9s, 180 2.9 0.6 3.3
80 kV, 5 mA, 9s, 180 2.2 0.5 2.5
70 kV, 5 mA, 9s, 180 1.5 0.4 1.8
6x6 90 kV, 5 mA, 17s, 360 5.2 3.1 5.2
80 kV, 5 mA, 17s, 360 4.0 2.4 3.9
70 kV, 5 mA, 17s, 360 2.8 1.8 2.7
90 kV, 5 mA, 9s, 180 2.1 0.2 2.7
80 kV, 5 mA, 9s, 180 1.6 0.2 2.0
70 kV, 5 mA, 9s, 180 1.1 0.1 1.4
4x4 90 kV, 5 mA, 17s, 360 3.4 3.0 3.7
80 kV, 5 mA, 17s, 360 2.6 2.3 2.7
70 kV, 5 mA, 17s, 360 1.9 1.7 1.9
90 kV, 5 mA, 9s, 180 1.2 0.3 1.9
80 kV, 5 mA, 9s, 180 0.9 0.2 1.4
70 kV, 5 mA, 9s, 180 0.6 0.2 1.0
Dose index measurements for the 3D Accuitomo 170
Index1
(mGy)
Index 2
(mGy)
Protocol AVG STDEV AVG
14.5x7.524 mAs,
central2.1 0.1 2.2
10x7.530 mAs,
central2.2 0.1 2.3
30 mAs,
off-axis2.1 0.6 1.7
6x636 mAs,
central1.8 0.4 2.0
36 mAs,
off-axis1.7 1.0 1.5
Dose index measurements for the Scanora 3D
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Workshop on dental Cone Beam CTSEDENTEXCT
Conclusions• dose distributions in homogenous phantoms
have been measured for different CBCTs and settings
• 2 CBCT dose indices have been proposed in addition to DAP
• validation measurements have been performed
Dental CBCT dose index
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Workshop on dental Cone Beam CTSEDENTEXCT
Development of mathematical models for
dental CBCT dosimetry
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Workshop on dental Cone Beam CTSEDENTEXCT
• Development of computational models for dental CBCT
dosimetry
• Calculation of conversion factors to effective dose using
Monte Carlo (MC) simulations
• MC simulations are a class of computational algorithms that
are based on repeated random sampling to compute the
results
• MCNP5: a general purpose Monte Carlo N-Particle code
Monte Carlo simulations
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Workshop on dental Cone Beam CTSEDENTEXCT
• Point sources with biased direction
• Arranged on a circle positioned at 10 degrees intervals
• A set of collimators to shape the beam
• ATOM 10 year old phantom
• ICRP male reference computational phantom
• ICRP female reference computational phantom (in progress)
Monte Carlo simulations
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Workshop on dental Cone Beam CTSEDENTEXCT
→ Validation of the simulated CB geometry-Stage 1• Simulated doses were compared against measured doses
• PMMA cylinder on a 3D Accuitomo 170 CBCT scanner
• Thermoluminescent dosimeters (<10% error)
• Full and half rotation CB geometry
• Range of tube voltages
• Range of FOVs
• Axis and off-axis
• % difference between simulated and measured normalised
doses ranged between 7% to 19%
Monte Carlo simulations
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Workshop on dental Cone Beam CTSEDENTEXCT
→ Validation of the simulated CB geometry-Stage 2• Simulated doses were compared against measured doses
• ATOM 10 year old anthropomorphic phantom
• Thermoluminescent dosimeters (<10% error)
• Range of CBCT machines
• Range of FOVs
• Range of clinical examinations
• % difference between simulated and measured effective
doses ranged between 3% to 17%
Monte Carlo simulations
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Workshop on dental Cone Beam CTSEDENTEXCT
Monte Carlo simulations
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Workshop on dental Cone Beam CTSEDENTEXCT
Monte Carlo simulations
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Workshop on dental Cone Beam CTSEDENTEXCT
→ Calculation of conversion factors (mSv/mAs)
• Three computational phantoms
• Range of FOVs, tube voltages, imaging protocols
• Range of machines• i-CAT NG
• Kodak 9000 3D
• Kodak 9500 3D
• NewTom VG
• NewTom VGi
• NewTom 5G
• NewTom QR DVT 9000
• Galileos Comfort
• Galileos Compact
• 3D Accuitomo XYZ
• 3D Accuitomo 170
• Planmeca Promax 3D (in progress)
• Planmeca Promax 3D Max (in progress)
Monte Carlo simulations
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Workshop on dental Cone Beam CTSEDENTEXCT
3D Accuitomo 170- 10 year old phantom
Imaging protocol Tube voltage Rotation Conversion factor
4Øcm x 4cm
Maxillary Canine
70/80/90 360 0.00028/0.00030/0.0.00031
10Øcm x 10cm 70/80/90 360 0.00248/0.00255/0.00261
17Øcm x 5cm
Mandible
70/80/90 180 0.00252/0.00254/0.00256
i-CAT NG - ICRP male reference computation phantom
Imaging protocol Tube voltage Rotation Conversion factor
16Øcm x 6cm
Maxilla
120 360 0.00130
16Øcm x 6cm
Mandible
120 360 0.00189
16Øcm x 13cm
Maxilla
120 360 0.00299
Monte Carlo simulations
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Workshop on dental Cone Beam CTSEDENTEXCT
Conclusions• a CBCT simulation model was set up and
validated
• conversion factors from mAs to effective dose were calculated for a broad range of CBCTs
• relation between dose indices 1 and 2 and effective dose has been established but needs further elaboration
• the relationship with DAP needs to be stablished
Monte Carlo simulations
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Workshop on dental Cone Beam CTSEDENTEXCT
Measurements of scatter dose and radiation
protection of personnel and helpers
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Workshop on dental Cone Beam CTSEDENTEXCT
Personnel dose
Protocol
• Active measurements
– Using ionisation chamber or
dose rate meter
– On standard measurement grid
• Passive dosimetry
– High sensitivity TLD badges
– In rooms where CBCT is sole
Xray source
Room plan
Positions of TLD badges on walls
50 cm
50 cm
a b c d e
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ag
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w
ai
an am al ak aj
ac ad
r u v
1
2
3
4
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Workshop on dental Cone Beam CTSEDENTEXCT
ModelManufacturer
Active
measurements
Passive
measurements
Kodak 9000 3D Kodak
Accuitomo 80 J. Morita
ProMax 3D Planmeca
NewTom 9000 QR
GX CB-500 Gendex
Scanora 3D XL Soredex
i-CAT NGImaging Sciences
International
Galileos Comfort Sirona
Accuitomo 170 J. Morita
NewTom VG QR*
Personnel dose
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Workshop on dental Cone Beam CTSEDENTEXCT
4.16.3
12.2 11.3
8.36.8 6.8
8.0
46.8
4.2
0
5
10
15
20
25
30
35
40
45
50
Kodak
9000 3D
Accuitomo
80
ProMax
3D
NewTom
9000
GX CB-500 Scanora
3D XL
i-CAT NG Galileos
Comfort
Accuitomo
170
NewTom
VG
Scat
ter
per
sca
n, µ
Sv
Active
Personnel dose
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Workshop on dental Cone Beam CTSEDENTEXCT
• For small FOVs, low workload and low occupancy of
adjacent areas, additional shielding may not be required
• In most circumstances, 0.5-1.5mm Pb equivalence is
required dependent on:
• Average scatter per scan
• Distance
• Workload
• Dose constraint
Shielding requirements
Personnel dose
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Workshop on dental Cone Beam CTSEDENTEXCT
• Max scatter varies 4.1 to 46.8 Sv per scan
• Distance unlikely to be sufficient protection, shielding required up to about 1.5mm lead
• Advice of a qualified expert required
• Base calculations on maximum scatter and double expected workload
• Manufacturers should provide scatter data
• Keep scatter and workload under review
• Further work needed on workload and to assess new units
Conclusions
Personnel dose
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Workshop on dental Cone Beam CTSEDENTEXCT
Work beyond SEDENTEXCT?
Further focus on paediatric dose
„Mathematical‟ dose optimisation (simulations,
reconstruction algorithms)
Long-term quality control of CBCT devices
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Workshop on dental Cone Beam CTSEDENTEXCT
Acknowledgement: The research leading to these
results has received funding from the European
Atomic Energy Community’s Seventh Framework
programme FP7/ 2007-2011 under grant agreement
no. 212246 (SEDENTEXCT: Safety and Efficacy of a
New and Emerging Dental X-ray Modality).