Organ Doses From Mammosite And Multicatheter Hdr Ir-192 Interstitial Brachytherapy In Woman Left Breast Heterogeneous Rando® Phantom
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Date
2015-10
Authors
AHMED DAHOUD, MAHMOUD SULEIMAN
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Abstract
The purpose of this research is to compare the value of doses delivered to organs at risk (OARs) that adjacent to the woman left breast inside RANDO® heterogeneous phantom by MammoSite and multicatheter interstitial brachytherapy using high dose-rate (HDR) Ir-192. This research involves dose measurements using different methods which are: radiation dosimetry using thermoluminescent dosimeters (TLD-100H) measures doses to organs at defined locations inside the heterogeneous phantom for each breast brachytherapy technique. Monte Carlo N-Particle simulation methods were also used beside the treatment planning to predict doses for each organ and at each TLD position inside the simulated phantom. Monte Carlo N-Particle simulation method is able to deal with the heterogeneity and simulates the distribution of radiation inside human phantom. The study performed using MammoSite single lumen brachytherapy system (MBS) was proven as an effective breast brachytherapy technique after breast conserving surgery. The radioactive material (192Ir) within the afterloader machine facilities moved inside the breast phantom through the catheter and delivered radiation at defined position (dwell positions) for a period of time (dwell time). The organs at risk which are adjacent to left breast absorbed unwanted radiation that can affect its cells. The multicatheter interstitial brachytherapy (MIB) technique had also studied in this research by inserting nine catheters inside breast phantom and deliver prescribed doses. The radioactive source enters the centre of 9 catheters by the use of afterloader to deliver precise amount of dose to surrounding tissues at dwell positions for dwell times. It
confirmed the good dose distribution inside planning target volume (PTV), but with high accuracy positioning surrounding the lumpectomy cavity. The research examines the values of dose reaches adjacent organs to the left breast (OARs) by MBS or MIB using TLD-100H and MCNP5. It uses real radiation dosimetry to measure doses at different locations inside phantom with the use of MCNP5 simulation methods to search for best brachytherapy technique between MammoSite balloon brachytherapy and multicatheter interstitial brachytherapy. The findings appeared that the heart, left lung, right lung, left ribs, spine, sternum, and right ribs received more doses in MBS compared to MIB with 2.1, 2.1, 0.1, 2.1, 1.8, 0.2, and 0.1 of prescribed dose respectively. The MIB covered the planning target volume and delivered higher dose value to 90% of the volume of planning target volume (PTV) than MBS and both satisfied the recommendations of brachytherapy protocols. Low dose values to organs at risk were delivered by both MIB and MBS but lower by MIB. The MIB and MBS appeared a novel breast brachytherapy technique which can spare OARs and deliver high dose values to PTV.
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Keywords
Organ Doses From Mammosite And Multicatheter Hdr Ir-192 Interstitial Brachytherapy , In Woman Left Breast Heterogeneous Rando® Phantom