<p>The purpose of this thesis is to explore the angular response to dose of the MatriXX Evolution, manufactured by IBA Dosimetry, a 2-dimensional ion chamber array used for patient specific quality assurance of advanced radiotherapy techniques such as IMRT and VMAT. Investigations were made to characterize the angular response of the MatriXX and describe any differences from the Philips Pinnacle³ Treatment Planning System (TPS) used at the Juravinski Cancer Centre.</p> <p>A comparison was made between the gantry angle dependent correction factors supplied by the manufacturer and those derived by measurement. Gantry angle dependent correction factors were derived, with the MatriXX under 5cm polystyrene build-up and without any build-up, for the 5 x 5 cm², 10 x 10 cm² and 20 x 20 cm² field sizes.</p> <p>For gantry angles ranging from 320^o to 40^o the maximum difference between the derived gantry angle dependent correction factors and those provided by the manufacturer is 1.5%, at a gantry angle of 320^o, a 5 x 5 cm² field and without build-up. The differences for the 10 x 10 cm² and 20 x 20 cm² fields within this gantry angle range are less than 1%. Between gantry angles of 50^o and 130^o the largest difference is 4.9% at 100^o, for the 5 x 5 cm²field without build-up. The other field sizes show similar differences; 4.7% at gantry angle of 120^o for 10 x 10 cm² with build-up and 4.0% at a gantry angle of 80^o without build-up. Between gantry angles of 140^o to 220^o the greatest discrepancy is for the 5 x 5 cm² field with build-up, a difference of 3.0%. The 10 x 10 cm² has a maximum difference of 2.4% at gantry angles of 180^o and 200^o, both when the MatriXX has build-up. The maximum discrepancy for gantry angle dependent correction factors for the 20 x 20 cm² fields is at a gantry angle of 140^o, when the MatriXX has build-up. Between the gantry angles of 230^o to 310^o the largest discrepancy occurs between the derived gantry angle dependent correction factors and those supplied by the manufacturer. For the 5 x 5 cm², 10 x 10 cm² and 20 x 20 cm² fields respectively the largest differences are 5.9%, 4.5% and 4.9%. All three occur when there is no build-up.</p> / Master of Science (MSc)