research support (siemens) consultant (hologics) speaker fees … · 2011. 8. 12. · 2011 aapm...
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2011 AAPM (Vancouver, BC) 1
Estimating Patient Specific
Doses/ Risks in Fluoroscopy
Walter Huda
Radiology and Radiological Science
MUSC Charleston, SC
Financial Disclosures
Research Support (Siemens)
Consultant (Hologics)
Speaker Fees (Carestream)
Book Royalties (LWW, MPP)
President (Huda Physics in
Medicine)
PURPOSE Patient Doses (Risks) of Interest
Skin Doses
Embryo Doses
Organ Doses
(?Effective Dose?)
2011 AAPM (Vancouver, BC) 2
Are exams indicated? Benefits > radiation risks
Barium Enema
Effective Dose ~ 5 to 15 mSv
Age (Years)
20 30 40 50 60 70 80
% p
er
10
0 m
Sv
0.0
0.5
1.0
1.5
2.0
M ales C ancer Incidence
Fem ale C ancer Incidence
BEIR VII Data
Risk varies by ~ x7 with age
2011 AAPM (Vancouver, BC) 3
Within each type of CT study, effective dose
varied significantly within and across
institutions, with a mean 13-fold variation
between the highest and lowest dose for each
study type
Arch. Intern Med. 169 (2009) 2078
(Any) Patient Risk Uncertain
x 10? x 100?
FLUOROSCOPY DOSES & RISKS PCXMC
2011 AAPM (Vancouver, BC) 4
FID
Focal Spot
Image Size:
25 x 25 cm
FID:
100 cm
KAP:
10 Gy-cm2
PA Projection
PCXMC Phantom
PCXMC “Output”
Organ Dose (mGy)
Effective Dose E (mSv)
PCXMC “Input”
Kerma Area Product (Gy-cm2)
(+ Beam Quality)
Organ Dose Cancer Incidence Risk
2011 AAPM (Vancouver, BC) 5
Vary patient “size” (PCXMC) RESULTS
Cancer RiskDifferent Beam Qualities
(kV/filtration)
2011 AAPM (Vancouver, BC) 6
Variable Beam Quality Variable Beam Quality
Cancer RiskPatient Size
2011 AAPM (Vancouver, BC) 7
70 kg
Patient Size
Nominal E
~
E70 x (70 / W)
70 kg W kg
70 kg
E = organs Di x wi
2011 AAPM (Vancouver, BC) 8
Patient Radiation (E)
vs
Natural Background Regulatory Limits
Other Procedures
Patient Specific Risks OBTAINABLE
USEFUL in Clinical Practice?
Educational Tool
2011 AAPM (Vancouver, BC) 9
Radiation-Related Cancer Risks
in a Clinical Patient Population
Undergoing Cardiac CT
Huda et al;
AJR 196 (2011) W159-65
x 10 Range in Patient Risk
2011 AAPM (Vancouver, BC) 10
Benefit versus Risk Justification + Optimization
Tube current modulation
(AP projection zero)
2011 AAPM (Vancouver, BC) 11
CONCLUSION Estimate Effective Dose (E)
Adjust E for patient size Patient Specific Radiation Risk
Remember “risk caveats”
2011 AAPM (Vancouver, BC) 12
1 in 10,000 risk for 40 y.o. ♂
1 year 0.5 mSv
Differences in life expectancy
of “patients” and normal population
Risk Uncertainties
The author acknowledges
Dennise Magill for her
assistance
