PO-0961: Evolution of mr image based brachytherapy in cervical cancers at Tata Memorial Hospital

U. Mahantshetty, R. Krishnatry, S. Jamema, Y. Ghadi, R. Engineer, S. Chopra, D. Deshpande, S. Shrivastava
2013 Radiotherapy and Oncology  
2nd ESTRO Forum 2013 S367 calculated deformation fields that can be applied to dose matrices. This allows us to accumulate the dose from one brachytherapy fraction to the next and will provide an improved estimate of the total dose delivered to the OAR. It should however be kept in mind that without a robust validation procedure,results could be very wrong in view of the very high dose gradients involved.The development of such a procedure should consequently be a prerequisite to any use of the
more » ... e to any use of the deformation for brachytherapy in the clinic. PO-0959 Towards a modified MR compatible Rotterdam applicator for combined intracavitary/interstitial HDR Brachytherapy Purpose/Objective: The MR compatible Vienna (tandem-ring) and Utrecht applicator (tandem-ovoids) can be used for combined intracavitary (IC) and interstitial (IS) brachytherapy (BT) of locally advanced cervical cancer, with needles inserted through holes in the ring or ovoids. Recently a novel titanium Rotterdam applicator (tandem-ovoids) (Nucletron, Elekta) has been introduced which is well suited for MR guided IC BT of cervical cancer. This applicator has a fixed geometry and therefore enables fast and accurate applicator reconstruction. Currently the Rotterdam applicator does not include holes in the ovoids for needle positioning. The configuration of the holes restricts the possible locations and directions of needles. Therefore, the holes in the ovoids should be positioned such to allow optimal needle positioning for every patient. The purpose of this study is to determine the optimal configuration of the holes for needle positioning in the ovoids of the Rotterdam applicator making it suitable for combined IC/IS BT. Materials and Methods: A planning study was performed using MR datasets of 4 randomly chosen patients receiving IC BT for cervical cancer using the Rotterdam applicator. HR-CTV (range 1.2 -57.5 cc), IR-CTV, rectum, sigmoid and bladder were delineated. The applicator was reconstructed with the aid of the applicator library file, a digital model of the applicator, present in the treatment planning system. For the IC treatment, without interstitial needles, modification of the standard treatment plan, that prescribes 7 Gy in points A, was necessary for all cases in order to restrict the dose to the OARs. The optimal position and direction of the ovoid holes for needle positioning was studied by adding virtual holes to the applicator library file at different locations and directions. This way treatment plans could be optimized for different needle (hole) configurations aiming at an increase of the dose to the HR-CTV while limiting the dose to the OARs. The configuration that yielded the best results among the 4 patients will be used as a blueprint for the holes in a prototype of the new applicator. Results: When using the IC applicator alone without needles, the dose in points A needed to be reduced from 7 Gy to 4.9 -6.7 Gy. This resulted in a coverage of the delineated HR-CTV of (only) 66.5, 60.0, 82.3 and 100.0 %, respectively, with a D90 HR-CTV of 4.9, 7.0, 5.9 and 9.8 Gy. It turned out that a geometry allowing for insertion of maximally 3 needles per ovoid, each having an angle of 15º with the tandem in ventral-dorsal direction, resulted in a considerable increase of the D90 HR-CTV. For this geometry the coverage of the HR-CTV was 88.1, 99.7, 98.6 and 100.0 %, respectively. The D90 HR-CTV was 6.7, 9.5, 9.4 and 10.2 Gy. Conclusions: We have studied the optimal configuration of holes in the ovoids of the Rotterdam applicator for needle positioning for combined IC/IS treatment of locally advanced cervical cancer. A prototype of this new applicator is being build. PO-0960 Effect of bladder fullness in brachytherapy procedure for EBRT complete response treated cervical cancer patients
doi:10.1016/s0167-8140(15)33267-9 fatcat:ndfry6kyynax3ciuqmhrdi342y