STUDY THE EFFECT OF PELVIC HETEROGENEITIES ON RECTUM DOSE MEASUREMENTS INSIDE AN INDIGENOUSLY MAKE FEMALE PELVIC PHANTOM AND RANDO FEMALE PELVIC PHANTOM USING MOSFET DOSIMETERS

Deepak shrotriya; R.S.Yadav

Volume : VII, Issue : IX, September - 2017

STUDY THE EFFECT OF PELVIC HETEROGENEITIES ON RECTUM DOSE MEASUREMENTS INSIDE AN INDIGENOUSLY MAKE FEMALE PELVIC PHANTOM AND RANDO FEMALE PELVIC PHANTOM USING MOSFET DOSIMETERS

Deepak Shrotriya, R. S. Yadav

Abstract :

Background: Human body consists of variety of heterogeneous tissues. Pelvis is the most heterogeneous regions viz. bones, soft tissues, fat, air cavities, faecal matter, urine etc. These heterogeneities lead to different attenuation for defined source energy. For the success of radiotherapy treatment in female pelvic cancers, there is a need to study the effect of tissue heterogeneities on dose distribution inside the tumor and adjacent normal tissues.

Objective: The aim of this study is to compare the direct measure rectal doses at various points inside an indigenously make inhomogeneous female pelvic phantom and Rando female pelvic phantom using in–vivo dosimeters and authenticate the heterogeneity correction algorithm by direct measurements.

Materials and Methods: MOSFET dosimetric system is used for dose measurements at different rectal points in female pelvic phantoms. Both phantoms are scanned on CT–Simulator (Siemens make) in 5 mm thick slices which are exported to treatment planning system (TPS). Intra–cavitary achytherapy plans are generated as per ICRU 38 and export to HDR achytherapy machine and then planned doses are measured directly at various rectal points.

Results: The rectum is a hollow pipe filled with air and faecal matter and surrounded by various heterogeneous tissues. The results indicate that the dose measured in the both female pelvic phantoms are in the range of 15–21% lower than the dose calculated by the TPS at the same rectal points.

Conclusion: The treatment planning system is overestimated the rectum dose. Therefore, the direct dose measurements in phantoms are useful for understanding the actual treatment conditions and post radiotherapy treatment complications.