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Evaluation of Image-Guided LDR Syed Implant and Differential Loading in the Treatment of Uterine Cervix


N Bhandare

N Bhandare*, Univ Florida, Gainesville, FL

SU-E-T-457 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose:
To evaluate the efficacy of image guided LDR Syed implant with differential loading for the treatment of cervical cancer.

Methods:
CT image sets of 20 patients with Syed applicator were used to generate 2 sets of treatment plans(40 Plans). Target volume (PTV) were delineated using CT/MR fusion. In 1st set of plans, uniform needle length and uniform loading was used as conventional method. In the 2nd set, the locations, lengths of the needles as well as the number, location and source activity were optimized using iterative variation of these parameters in context of anatomical information to obtain a coverage of PTV with a reference dose rate of 50 cGy/hr of 85% while limiting the dose to bladder, urethra and rectum. For both sets of the plans Conformity index (COIN), Homogenity index (HI), Overdose volume index (OVI) and doses to 2 cc of bladder, urethra and rectum, sigmoid were estimated.

Results:
For 1st set of plans COIN, varied between 0.47 to 0.60, for the 2nd, it varied between 0.60 to 0.72.
For 1st set of plans HI varied between 0.4 to 0.52, for the 2nd, it varied between 0.3 to 0.0.4.
For 1st set of plans OVI varied between 0.33 to 0.45, for the 2nd, it varied between 0.20 to 0.30.
A 15-45 % reduction of dose to 2 cc of bladder and urethra, 20-40% reduction in dose to 2 cc of rectum and sigmoid were obtained in 2nd set of plans.


Conclusion:
Image guided brachytherapy with optimization of needle location, length and activity of Ir-192 ribbons yields higher conformity of prescribed dose to target volume while reducing the doses to OARs.

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