1. Exhibit Number: C19 Evaluation and Reduction of Head Computed Tomography Dose
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2. Presentation Outline Introduction Research Objectives Background
Measuring the Dose
Methods
Results
Conclusions

3. Introduction Computed Tomography is a high dose modality
Radiation optimization
The process of making the most effective use of ionizing radiation during a head CT exam
All radiographers should apply the principle to keep radiation exposures As Low As Reasonably Achievable (ALARA)

4. Research Objectives
The objective of this effort is to reduce head CT dose by:
Validating and comparing patient head CT doses to external benchmarks
Analyzing dosimetry data to evaluate the effectiveness of the dose reduction
Assessing technique modifications using a standard CT phantom and test procedures
Evaluating the patient dosimetry prior to and after modification of CT protocols

5. Background
Two perspectives: Desirable use of 1 – 2 Million equipment; undesirable increase in CT when not clinically appropriate
F. Mettler ICRP 2011
The amount of CT examinations performed in the last 13 years has increased dramatically

6. Background CT uses a rotating x-ray tube as the patient table moves
A fan-shaped x-ray beam rotates 360 degrees and is paired with multiple sets of image detectors
Conventional X-ray beam
CT beam geometry

7. Patient Position In the Scanner
Patient head phantom in head holder

8. Measuring the Dose
CT has it’s own way of measuring patient dose, the two measurements employed
Volume CT Dose Index, CTDIvol
CT protocol specific dose
Dose-Length Product, DLP
Patient specific dose
Value derived from CTDIvol

9. Measuring the Dose Measuring CTDIvol
Using an ionization chamber and meter
Chamber placed in an acrylic head phantom

10. Methods CT dose was tracked at nine sites
Sites 3 and 7 are hospitals with a dedicated ED CT
The optimization effort used data from Site 7

11. Methods
CT patient dose monitoring and data collection system includes:
Data collected in Radimetrics (Bayer HealthCare LLC)
External benchmark values determined with data from the American College of Radiology (ACR) National Radiology Data Registry (NRDR) Dose Index Registry (DIR)

12. Methods Site 7 compared to ACR DIR values
Top 10 adult and pediatric exams
Identifies outliers
Adjust font. First start with clean template

13. Head protocol selected because it was the highest outlier
Methods
Adjust font. First start with clean template
Head protocol selected because it was the highest outlier

14. Methods CT head technical exam parameters include:
mAs (milliamperes per second)
kVp (kilovoltage peak)
Rotation time (in milliseconds)
Pitch
The only parameter modified in the dose optimization effort was mAs
Adult mAs reduced by approximately 13%
Pediatric mAs reduced by approximately 10%
Adjust font. First start with clean template

15. Adult (above 12 Years Old)
Results
3-5 Years Old
Pre-Reduction
Post-Reduction
mAs
125
115
CTDIvol (mGy)
48.3
44.4
DLP (mGy-cm)
847.2
752.8
6-12 Years Old
Pre-Reduction
Post-Reduction
mAs
150
135
CTDIvol(mGy)
57.9
52.1
DLP (mGy-cm)
1,003.1
898.5
Adult (above 12 Years Old)
Pre-Reduction
Post-Reduction
mAs
180
157.5
CTDIvol(mGy)
69.5
60.8
DLP (mGy-cm)
1270.8
1113.3

17. Results
The reduced adult head dose is approximately the same as the pediatric head dose before reduction

18. 955.6 mGy-cm
821.4 mGy-cm

19. Conclusions
The dose reduction effort began with adult heads followed by pediatric head CTs
As exam parameters were reduced, the head CT dose was reduced
Our objective to reduce CT head dose was achieved
The adult head dose optimization effort resulted in an 12.4% reduction
The pediatric head dose optimization resulted in an overall reduction in dose by 7.1%

20. References
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