Kathryn Louise Everton MD, Presenter: Nothing to Disclose

Donald P. Frush MD, Abstract Co-Author: Research Consultant, General Electric Company Research Consultant, Siemens AG

Terry T. Yoshizumi PhD, Abstract Co-Author: Research support, General Electric Company

Samuel Brady, Abstract Co-Author: Nothing to Disclose

Greta Toncheva MS, Abstract Co-Author: Nothing to Disclose

Xiaodong Zhou PhD, Abstract Co-Author: Employee, Siemens AG

Lynne Michelle Hurwitz MD, Abstract Co-Author: Research grant, Siemens AG

Ehsan Samei PhD, Abstract Co-Author: Advisory Board, Ion Beam Applications, SA Consultant, Siemens AG

To assess the dose distribution implications of new partial rotation-based angular modulation (X-care) for pediatric chest CT using a radiochromic, radiation sensitive film (RCF).

16-cm CTDI phantom and a 5 yr-old anthropomorphic phantom (CIRS) underwent 64-slice MDCT evaluation (Siemens, Definition) with and without angular modulation (X-care). XRQA radiochromic film (International Safety Products) was placed circumferentially (orthogonal to beam) and axially (parallel to beam) within CTDI phantoms, and axially at slices near breast tissue in the 5-yr old phantom. Specific protocols were applied for the CTDI phantom (120 kVp, 226 eff mAs, 1.0 s rot time, 24 x 1.2 configuration, 0.6 pitch) and the anthropomorphic phantom (120 kVp, 200 eff mAs, 0.33 rot time, 24 x 1.2 configuration, 0.6 pitch). Films were digitized at 0.4 mm pixels, no color corrections, using 48-bit color depth (RGB format).The red channel was extracted for analysis in Matlab since RCF readout sensitivity is optimized using red light. Calibrated optical density (OD) was used as dose surrogate.

In CTDI phantoms with X-care, OD was reduced anteriorly over a 122 degree arc (eg breast region) and increased posteriorly. The decrease comparing anterior to posterior OD mid slice profile was 29% in the 16-cm phantom. With X-care off in the 16-cm phantom, there was a 15% increase in OD anterior compared with posterior, probably from table attenuation. For anthropomorphic phantom at the slice level above and below breast tissue, there was an average 10% decrease OD subjacent to breast tissue with X-care on, and a 5% increase in OD at the spine with X-care on(Figure).

Radiochromic film provides unique opportunities for multi dimensional dose distribution not possible with traditional point source dosimetry (e.g. MOSFET, TLD). This is helpful in assessing new technology in pediatric CT. Use of new angular dose modulation for MDCT X-care software reduces dose over a 122 degree arc with compensatory dose increase over the opposite location in the phantom. Dose savings (and risk) from breast tissue dose reduction must be balanced with potential increased dose to posterior organs (e.g. lung, esophagus, bone marrow).

Radiochromic film provides novel radiation dose distribution information, difficult with conventional point source dosimetry, which is useful in assessing new CT technology in children.

Everton, K, Frush, D, Yoshizumi, T, Brady, S, Toncheva, G, Zhou, X, Hurwitz, L, Samei, E, Investigation of Angular Dose Modulation during Pediatric Chest MDCT Using Novel Multidimensional Radiochromic Film Dosimetry.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9009695.html