Determination of the effective SSD as the function of various energy and field size for siemens digital mevatron linear accelerator model type MXE 2 in HUSM

• Main Author: Zakaria, Noor Ainzza
• Format: Article
• Language: English
• Published: Pusat Pengajian Sains Kesihatan, Universiti Sains Malaysia 2004
• Subjects: R Medicine
• Online Access: http://eprints.usm.my/45965/1/LI...Noor%20Ainzza%20Binti%20Zakaria...2004...24%20pages.pdf; http://eprints.usm.my/45965/

(SSDetr) as the function of various energies and field sizes for the SIEMENS DIGITAL MEV ATRON (model MXE 2) linear acceleralor in HUSM. The experiment involv~ electrons energies which deputized the lowest energy, the middle energy and the highest functional energy provided by this machine .The energies were 5 MeV, 7 MeV, and 9 MeV electron beams. The measurement for the energies level were done together with the application of the available applicators which carried the field size Scm x Scm, 1 Ocm x 1 Ocm, 1 Scm x I Scm, 20cm x 20cm ,and 25cmx25cm. Several materials and devices were used for the experiment which included the parallel plate chamber, solid water phantom and an electrometer. The method of measurement to determine the effective SSD was such that the parallel plate ionization chamber was located at the depth of dose maximum for the specific energies and fields sizes applied and after that a series of output measurements were made at that depth. The measurements started with zero air gap between an applicator surface and the phantom surface for a selected energy .Every single shoot, the gap between applicator surface and phantom surface was increased about 1 em until reach 15 em. The same procedures were repeated for all defined energies and applicators. A few calculations involved in the process of determining effective SSD. For all of the energies used, the deviations of the measurement reading from the inverse square law estimation were found larger up to more than SO% for the smaller field size applied. An effective SSD, SSDetr had been determined at dmax for each energy as a function of field size. For 5 MeV electron energy with 5x5 field size, 10 x10 field size,15x 15 field size,20 x 20 and 25 x 25, the values are 37.07 em, 79.65 cm,95.15cm,l00cm and 105.26.For 7 MeV energy with the same field size as mentioned above, the values are 46.47cm, 91.18cm, 96.83cm,107.3lcm, and 105.18cm.While for 9 MeV with all the field size as mentioned before, the values are 57.78cm,96.26cm,104.60cm,104.56cm and 104.77cm. The effective SSD values determined for the energies and fields sizes are fixed for a specific condition