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Survey of Radiation Beam Width in CT According to ACR 2012 CT QC Manual


C Tsai

Y Lin1, y hwang2, H Liu3, Y Wang4, C Tsai5*, (1) Chang Gung University, Tao-yuan County, Taiwan, (2) Department of Diagnostic Radiology and Intervention, Chang Gung Memorial Hospital at Linkou(3) Chang Gung University, Kweishan Taoyuan, ,(4) Atomic Energy Council, Yunghe District, New Taipei City, (5) Chang Gung University, Tao-yuan,

SU-E-I-40 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose:
To survey CT radiation beam width using in clinical protocols according to America College of Radiology (ACR) 2012 CT Quality Control Manual. We assessed the relationship between nominal collimated and radiation beam width.

Methods:
Radiation beam width was measured using a self-developed film (GAFCHROMIC XR CT2) for 346 CT scanners. The film was placed at the isocenter of CT scanner. Nominal collimated beam widths (NxT) using for clinical examinations of routine adult head, adult abdomen, and 5-years pediatric abdomen were measured.

Results:
The performance criteria set by ACR 2012 CT Quality Control Manual are that the measured radiation beam width should be accurate to within 3 mm or 30% of the nominal collimated beam width (NxT), whichever is less. According to our survey, the fail rates were 18.8% for adult head examinations, 15.0% for adult abdomen examinations 20.1% for 5-years pediatric abdomen examinations. If the criteria were set to within 3 mm or 30% whichever is greater, the fail rates dropped to 8.2%, 0.6%, and 2.0%, respectively. Toshiba CT scanners have to pay more attention to meet ACR criteria because the fail rate was from 39% to 75%.

Conclusion:
This survey gave a view of relationship of nominal and radiation beam width in different protocols and manufacturers. About twenty percent of CT scanners cannot pass the ACR criteria of radiation beam width.

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