Transcript Image quality and quality assurance in (digital) dental

DAP as a tool for analysis of
effective dose and maximum skin dose:
finalised and current projects
Klaus Bacher
Ghent University
Department of Basic Medical Sciences
Patient Dosimetry in Radiology, Management Center Europe, June 26 2010
Dose area product (DAP)
• Easy online measurement of patient radiation exposure
• Quantity is directly used for:
 Definition of diagnostic reference levels (DRLs)
 Optimization
• Possible use of DAP for further (risk) analysis:
 Stochastic effects: correlation with effective dose
 Deterministic effects: correlation with maximum skin dose
 not straightforward!
DAP and effective dose
Effective dose
• Weighted sum of equivalent organ doses HT
E   wT .HT
T
• Risk-related quantity (not for individual risk assessment!)
• Comparison of risks of different imaging modalities is possible
• No in vivo measurement possible
• To be calculated/simulated according to ICRP 103 publication (2007)
DAP and effective dose
Effective dose for optimization?
• Intercomparisons of different procedures:
same DAP in different X-ray procedures
same effective dose
• Intercomparisons within a specific procedure:
lower DAP in specific X-ray procedure
18
160
16
140
14
120
12
E (mSv)
DAP (Gy.cm²)
180
lower effective dose
100
80
10
8
60
6
40
4
20
2
0
0
A
B
C
D
E
F1
F2
G
H
I
A
B
C
D
E
F1
F2
G
H
From: L. Struelens, Optimisation of Patient Doses linked to Image Quality in Vascular Radiology, 2005
DAP and effective dose
Project supported by FANC
• Use of effective dose for further optimization, especially for
interventional procedures
→ need for accurate conversion coefficients based on DAP
• Project: DAP to effective dose conversion in cardiology and
vascular/interventional radiology
DAP and effective dose
Effective dose simulation
• ICRP 103 publication (2007)
 Taking into account the extended organ list (<-> ICRP 60)
 New organ weighting factors
 Use of reference voxelized computer model (<-> mathematical models)
From: M. Zankl et al., Organ dose conversion coefficients for external photon irradiation of male and female voxel models, 2002
DAP and effective dose
Effective dose simulation
• Male and female reference voxel phantoms (Zankl et al.)
X-ray Characteristics for Imaging and Radioprotection
Klaus Bacher
DAP and effective dose
Effective dose simulation
• ICRP 103 publication (2007)
 Sex averaging of organ doses
From: ICRP Publication 103: The 2007 recommendations of the International Commission on Radiological Protection, 2007
DAP and effective dose
Effective dose simulation
• Simulations taking into account
 12 projections for interventional cardiology procedures
 20 projections for vascular/interventional radiology procedures
 Different X-ray spectra (mm Al HVL)
→ 256 DAP to effective dose conversion coefficients
X-ray Characteristics for Imaging and Radioprotection
Klaus Bacher
DAP and effective dose
Results
X-ray Characteristics for Imaging and Radioprotection
Klaus Bacher
DAP and effective dose
Results
X-ray Characteristics for Imaging and Radioprotection
Klaus Bacher
DAP and effective dose
Results
• Final report available on: www.fanc.fgov.be (section medische
stralingsfysica/radiophysique médicale)
DAP and maximum skin dose
Belgian multi-centre study (2005)
• Multicenter study on skin doses of patients, treated with prolonged
cardiological interventions (supported by FANC):
 Skin dose measurements in 318 adult patients in 8 Belgian
hospitals
 Investigation of correlation of maximum skin dose with DAP
From: E. Bogaert et al., Multicenter study on skin doses of patients, treated with prolonged cardiological interventions, 2005
X-ray Characteristics for Imaging and Radioprotection
Klaus Bacher
DAP and maximum skin dose
Belgian multi-centre study (2005)
• Multicenter study on skin doses of patients, treated with prolonged
cardiological interventions:
 Identification maximum skin doses
From: E. Bogaert et al., Multicenter study on skin doses of patients, treated with prolonged cardiological interventions, 2005
X-ray Characteristics for Imaging and Radioprotection
Klaus Bacher
DAP and maximum skin dose
Belgian multi-centre study (2005)
• Multicenter study on skin doses of patients, treated with prolonged
cardiological interventions:
 Investigation of correlation of maximum skin dose with DAP
→ establishing “trigger levels”
From: E. Bogaert et al., A large-scale multicentre study of patient skin doses in interventional cardiology: dose-area product action levels and dose reference levels, 2009
X-ray Characteristics for Imaging and Radioprotection
Klaus Bacher
DAP and maximum skin dose
Project supported by FANC
• 2005 project: DAP trigger levels for cardiological interventions
→ need for DAP trigger levels in other interventional procedures
• Current project: Determination of trigger levels for patient doses
for interventional procedures (TRIR)
DAP as a tool for risk analysis
Klaus Bacher
DAP and maximum skin dose
Project supported by FANC
• Measurements of skin dose distribution and maximum skin dose in
12 hosptitals and for different procedures:
 Radiofrequency (RF) ablations
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Transjugular Intrahepatic Portosystemic Shunt (TIPS)
Chemo embolizations of the liver
Cerebral embolizations
Embolizations of vena spermatica
Creation or treatment of AV fistula for hemodialysis
Endoscopic retrograde cholangiopancreaticography (ERCP)
Biliary drainages
• End of measurements: june 2010
• Final report by july 2010
X-ray Characteristics for Imaging and Radioprotection
Klaus Bacher