vol Measurements and Diagnostic Reference Levels in Michigan Radiation Safety Section of the State of Michigan Patient dose from CT was 3 of all medical exposure in 1980s It increased to 49 in 2006 ID: 760799
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Slide1
Computed Tomography CTDIvol Measurements and Diagnostic Reference Levels in Michigan
Radiation Safety Section of the State of Michigan
Slide2Patient dose from CT was 3 % of all medical exposure in 1980s
Slide3It increased to 49% in 2006
Slide4II. Recent Medical Errors
Slide5Radiation Safety Section
Part 15. Computed Tomography Installations
Effective June 8, 2011
Rules, Guidance Document, and FAQs available at:
www.michigan.gov/rss
Slide6Rule 713 – Conditions of Operation
(1) Six months after the effective date of these rules, the CT facility shall establish scanning protocols in consultation with a medical physicist.
Slide7CT Inspection Schedule
1
st
year – Inspect all CT machines, education over enforcement
2
nd
year – Inspect all CT machines, begin issuing citations continue education
3
rd
year – Begin inspecting some machines every other year
4
th
year- Continue every other year inspections schedule
5
th
year – Transition back to inspecting CT machines every 4-5 years
Slide8CT Dosimetry Phantoms
Each inspection included measurement of CTDIvol for an adult head scan and a pediatric body
Slide9Slide10Slide11Summary of Data – Head CTDIvol
Year
2011
2012
2013
2014
2015
2016
Count
122
320
334
278
104
33
75
th
(
mGy
)
67.3
67.3
66.9
64.4
63.5
60.7
Minimum (
mGy
)
13.1
20.7
23.0
15.6
24.3
26.7
Maximum (
mGy
)
116.1
92.0
100.2
81.8
79.9
78.1
Standard Deviation
14.5
12.1
12.7
12.1
11.3
11.6
Ave CTDIvol (
mGy
)
59.4
57.9
57.2
55.6
56.1
52.3
Slide12Summary of Data – Ped Body CTDIvol
Year
2011
2012
2013
2014
2015
2016
Count
74
217
210
175
64
15
75
th
(
mGy
)
13.9
13.7
12.5
12.4
11.1
8.9
Minimum (
mGy
)
2.0
1.6
0.8
0.9
1.5
3.0
Maximum (
mGy
)
44.2
29.3
26.4
24.8
23.3
15.9
Standard Deviation
6.2
5.5
5.0
4.7
4.9
3.7
Ave CTDIvol (
mGy
)
11.0
10.4
9.5
9.2
9.2
7.5
Slide13CTDI reduced by about 15 % From 2011 – 2016
Slide14Adult Head Scan
Pediatric Body
CTDI Dose Distributions by Year
2011
Count 122
Ave CTDIvol - 59.4 mGy75th Percentile - 67.3 mGy
Count 74
Ave CTDIvol - 11.0
mGy
75
th
Percentile – 13.9
mGy
Slide15Adult Head Scan
Pediatric Body
CTDI Dose Distributions by Year
2012
Count 320
Ave CTDIvol - 57.9 mGy75th Percentile - 67.3 mGy
Count 217
Ave CTDIvol - 10.4
mGy
75
th
Percentile – 13.7
mGy
Slide16Adult Head Scan
Pediatric Body
CTDI Dose Distributions by Year
2013
Count 334
Ave CTDIvol - 57.2 mGy75th Percentile – 66.9 mGy
Count 210
Ave CTDIvol - 9.5
mGy
75
th
Percentile – 12.5
mGy
Slide17Adult Head Scan
Pediatric Body
CTDI Dose Distributions by Year
2014
Count 278
Ave CTDIvol - 55.6 mGy75th Percentile – 64.4 mGy
Count 175
Ave CTDIvol - 9.2
mGy
75
th
Percentile – 12.4
mGy
Slide18Adult Head Scan
Pediatric Body
CTDI Dose Distributions by Year
2015
Count 104
Ave CTDIvol - 56.1 mGy75th Percentile – 63.5 mGy
Count 64
Ave CTDIvol - 9.2
mGy
75
th
Percentile – 11.1
mGy
Slide19Adult Head Scan
Pediatric Body
CTDI Dose Distributions by Year
2016
Count 33
Ave CTDIvol - 52.3 mGy75th Percentile – 60.7
Count 15
Ave CTDIvol - 7.5
mGy
75
th
Percentile – 8.9
mGy
Slide20State of Michigan CTDIvol 75th Percentile and Median
CTDI
Adult Head
CTDI Pediatric Body
Count 2011-2016
445
339
Median
57.1
mGy
8.4
mGy
75
th
percentile
64.1
mGy
12.3
mGy
Slide21CTDIVOL Dose Distributions2012 - 2016
Slide22Possible reasons for CTDI reduction
New rules required review of protocols by a Medical Physicist (MP)
Annual inspections highlighted facilities with a CTDI
vol
outside of the ACR reference values and encourage reduction with MP input
More education by professional societies and equipment manufacturer’s with lowering CT doses.
Rules required QC program approved by Medical Physicist.
Slide23State of Michigan – Medical ESE75th Percentile and Median
75
th
percentile
Median
(N = Machines Tested)
(mR)
(
mGy
)
(mR)
(
mGy
)
CTDI Adult Head (N=445)
64.1
57.1
CTDI Pediatric Body (N=339)
12.3
8.4
AP Lumbar Spine (N = 2694)
365
3.20
265
2.32
AP Cervical Spine (N = 1548)
78
0.68
55
0.48
PA Chest - With Grid (N = 1817)
23
0.20
16
0.14
PA Chest - No Grid ( N = 328)
15
0.13
10
0.09
DP Foot (N=877)
12
0.11
8
0.07
Cephalometric (N=599)
12
0.11
8
0.07
Hand (N=2537)
7
0.06
5
0.04
Slide24Slide25State of Michigan – Dental ESE75th Percentile and Median
DRL
Achievable Dose
(N = Machines Tested)
(mR)
(
mGy
)
(mR)
(
mGy
)
Cephalometric (N=599)
12
0.11
8
0.07
Dental Bitewing
- D Speed Film (N=2895)
305
2.67
249
2.18
- E Speed Film (N=1325)
175
1.55
135
1.20
- CR (N=2474)
155
1.35
109
0.95
- DR (N=7711)
115
1.00
83
0.73
Slide26Slide27For more information on patient radiation exposures and DRLs in Michigan visit
www.michigan.gov/rss
Click on the link called
Patient Radiation Exposure Information for
tables and graphs showing our patient radiation exposure and dose measurements and the established diagnostic reference levels for various exams.
Contact Information
Don Parry, CHP
parryd@michigan.gov
517-284-7818