Exhibit Number: C19 Evaluation and Reduction of Head Computed Tomography Dose Because of full frame graphic use title slide sparingly because too many of them will increase PP file size.

Presentation Outline Introduction Research Objectives Background Measuring the Dose Methods Results Conclusions

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)

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

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

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 http://www.ajnr.org/content/30/6/1088

Patient Position In the Scanner Patient head phantom in head holder

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

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

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

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)

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

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

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

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

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

955.6 mGy-cm 821.4 mGy-cm

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%

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