Presentation Title

Presentation Title

Exhibit Number: C19 Evaluation and Reduction of Head Computed Tomography Dose 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 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 Patient Position In the Scanner Patient head phantom in head holder Measuring the Dose CT has its 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

CT HEAD Distribution per CT scanner, total = 1,139 exams CT Head Exams 450 400 350 300 250 200 150 100 50 0 Site 1

Site 2 Site 3 Site 4 Site 5 Site 6 Site 7 Site 8 Site 9 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 Methods 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% 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% References Callahan, MJ. CT dose reduction in practice. Pediatr Radiol. 2011 Sep;41 Suppl 2:488-92. Doi: 10.1007/s00247-0112099-y. Epub 2011 Aug 17. Review. PubMed PMID: 21847727. Graves JM, Kanal KM, Vavilala MS, Applegate KE, Jarvik JG, Rivara FP. Hospital-level factors associated with use of pediatric radiation dose-reduction protocols for head CT: results from a national survey. J Am Coll Radiol. 2014 Jul;11(7):717-724.e1. Doi: 10.1016/j.jacr.2013.12.002. PubMed PMID: 24993537; PubMed Central PMCID: PMC4082793. Martin, C. J., & Sutton, D. G. (2015). Practical radiation protection in healthcare(2nd ed.). New York: Oxford University Press. Miglioretti DL, Johnson E, Williams A et al (2013) The use of computed tomography in pediatrics and the associated radiation exposure and estimated cancer risk. JAMA Pediatr 167:700-707 Pediatric Radiology & Imaging | Radiation Safety Image Gently. (n.d.). Retrieved May 22, 2017, from Seeram, E. (2016). Computed tomography: physical principles, clinical applications, and quality control (3rd ed.).

St. Louis, MO: Elsevier. The Alliance. (n.d.). Retrieved November 19, 2017, from (U.S.), N. R. (1990). Health Effects of Exposure to Low Levels of Ionizing Radiation: BEIR V (BEIR ; 5). National Academies Press.

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