ORIGINAL PAPER Polymer gel dosimetry on a multislice computed tomography scanner: Effect of changing parameters on CTDI B. Hill a,b, *, A.J. Venning c , C. Baldock b a Medical Physics, The Canberra Hospital, ACT Health, P.O. Box 11, Woden, Canberra, ACT 2606, Australia b Institute of Medical Physics, School of Physics, University of Sydney, NSW 2006, Australia c Wellington Blood and Cancer Centre, Wellington Hospital, Private Bag 7902, Wellington South, New Zealand Received 23 July 2007; received in revised form 20 November 2007; accepted 22 November 2007 Available online 4 March 2008 KEYWORDS Computed tomography; Normoxic polymer gel dosimetry; Radiation; Dosimeter; CT; MRI; Dose profile Abstract Polymer gel dosimetry undertaken on a multislice CT scanner provides an alterna- tive method to conventional dosimetry measurements. Polymer gel dosimeters were used to measure CT radiation doses and compared to TLD and ionization chamber measurements in dif- ferent diameter phantoms. CTDI was investigated for each of these phantoms for a range of mAs (100e400 mAs), tube voltage (100e135 kV) and nominal slice width (2e32 mm). Linear fits of the CTDI values for mAs show for the smallest phantom diameter an increase in CTDI of 60% for both TLD and polymer gel dosimeters. A similar increase in CTDI of 50% at 100 kVp and 100% for 135 kVp was also noted. It was also shown that slice width variation measured with either polymer gel or TLD was greatest with the smallest slice widths. In summary, it was found that polymer gels can be used as an alternative dosimeter to TLD for the determination of SWDP and subsequent CTDI calculations. ª 2007 Published by Elsevier Ltd on behalf of Associazione Italiana di Fisica Medica. Introduction Polymer systems for the use of radiation dosimetry were first proposed as early as 1954, where Alexander et al. discussed the effects of ionising radiation on polymethylmethacrylate [1]. Following this, Hoecker and Watkins [2] in 1958 investi- gated the dosimetry of radiation-induced polymerization in liquids, and in 1961, Boni [3] used polyacrylamide as a gamma dosimeter. In 1992, a polymer formulation was sug- gested that consisted of acrylamide (AA) and N,N 0 -methy- lene-bis-acrylamide (bis) monomers infused in an aqueous agarose matrix. This polymer gel formulation did not have the diffusion limitations of Fricke gels [4]. In 1994, Maryanski et al. modified the formulation by replacing agarose with gelatine and named the, now commercial, product BANG â * Corresponding author. Medical Physics, The Canberra Hospital, ACT Health, P.O. Box 11, Woden, Canberra, ACT 2606, Australia. Tel.: þ61 2 62442256. E-mail address: brendan.hill@act.gov.au (B. Hill). 1120-1797/$ - see front matter ª 2007 Published by Elsevier Ltd on behalf of Associazione Italiana di Fisica Medica. doi:10.1016/j.ejmp.2007.11.005 available at www.sciencedirect.com journal homepage: http://intl.elsevierhealth.com/journals/ejmp Physica Medica (2008) 24, 149e158