Antiquing process

S600 for the Cyberknife Treatment Planning System. parameters of these two techniques were compare radiosurgery plans for a prescription dose of 38.75Gy which is biologically equivalent to the clinical HD fractionation using α/β ratio of 3.0Gy. Cumulativ histograms were used to the evaluate dosimetric follows: CTV volume covering the prescription isodo covered by 100% (Vp,100%), 150% (Vp,150%) and isodose, dose received by 100% and 90% of the PTV vol Dp,90%), volume of rectum receiving 12.5Gy and 7.8G Vr,7.8Gy), dose received by 2cc volume of rectum received by the 30% and 10% of the urethra volu Du,10%), volume of urethra receiving 15.0Gy conformality index. Paired Student’s‘t’ test was us results. Results: There was no significant difference in the vol covered by the prescription isodose [99.6% ± 0.4 (SB 0.9 (HDRBT)], Dp,90% [13.6Gy ± 0.1 (SBRT)vs. 13.0Gy and in the conformality index [0.78 ± 0.04 (SBRT)v (HDRBT)]. The Cyberknife technique gave statistica better PTV coverage (Vp,100%), than HDRBT [98.5% ± 1.8; P<0.0005]. The mean Vp,150% was 0 (SBRT 2.6(HDRBT); (P<0.0005) and Vp,200% was 0 (SBRT) v (P<0.0005). The Dr,2cc was always higher in Cy [10.5Gy± 0.8 vs. 8.7Gy ± 1.1; P<0.0005). The Vr,1 Vu,15Gy were both 0cc with either technique. The substantially higher in the Cyberknife plans [10.4Gy ± 2.1; P<0.0005] than with HDRBT. The urethral Du,30% comparable between these techniques. Conclusions: Both HDRBT and Cyberknife SBRT ca produce acceptable dose distributions for localised p but with different dosimetric characteristics. It woul to speculate on whether these differences will t significant clinical effect; further work in this area w EP-1564 EXTENDING TREATMENT FIELD SIZE USING VMAT ISOCENTERS A. Perez-Rozos 1 , S. Vilar-González 2 , C. Herrero Capellá Sanz 1 1 IMOMA - Centro Medico de Asturias, Medical Physics, 2 IMOMA - Centro Medico de Asturias, Radiotherapy, Ov Purpose/Objective: To study the possibilities of VM optimization algorithms to extend the effective treatm multiple isocenters and overlaping VMAT beams. Th traditionally resorted to different techniques of ov using more than one isocenter. In this paper we w feasibility of using the possibilities of inverse optimiz using multiple isocenters VMAT. Materials and Methods: We will use Philips Pinna planning system with SmartArc module, usin BeamModulator (16x21 cm maximum field) and Varian cases are considered with both MLC models: theore head and neck and prostate patients. The treatment cover the treatment volume with multiple isocen beams, allowing overlap between consecutive arcs. A clinically acceptable dosimetry we will do an analysis treatment setup, displacing isocenters 5mm and study of the overlap region. Results: The VMAT beams muste arranged overlaping order to allow the optimization algorithm to pro transition without steep gradients. Minor overlap pr gradients and are more sensitive to setup errors, and increases the number of isocenters, beams and optim the three cases we obtain a clinically acceptable so also less sensitive to setup errors of the different conventional bonding fields. The length of the volume limited by the memory and the planning system to m necessary for calculation and optimization. Conclusions: The use of inverse planning and VMAT SmartArc module allows the planning of volumes larg limitations of our collimator field, keeping the tre similar values, and less sensitivity to patient setu compared to conventional techniques. The dosimetric ed by producing y in 5 fractions, DRBT dose and ve dose volume parameters as se, PTV volume 200% (Vp,200%) ume (Dp,100% & Gy (Vr,12.5Gy & m (Dr,2cc), dose ume (Du,30% & (Vu,15Gy) and sed to compare lume of the CTV BRT) vs. 99.0% ± y ± 0.3 (HDRBT)] vs. 0.81 ± 0.05 ally significantly 0.6 vs. 94.8% ± T) vs. 30.8% ± vs. 10.1% ± 1.6; yberknife plans 12.5Gy and the e Vr,7.8Gy was 4.4 vs. 3.9Gy ± and Du,10% are an be used to prostate cancer, d be premature ranslate into a will be required. AND MULTIPLE án 1 , A. Serrano Oviedo, Spain viedo, Spain MAT and inverse ment field using his situation has verlapping fields will analyze the zation technique acle3 treatment ng an Elekta n HDMLC. Three etical phantom, technique is to ters and VMAT After obtaining a of sensitivity of ing the behavior g about 4 cm in duce a smooth roduces steeper greater overlap mization time. In olution, which is isocenters than to be treated is manage the data T with Pinnacle er than the size atment time in up uncertainties EP-1565 DOSE DISTRIBUTION OF CONFORMAL RADIOT FIELD TECHNIQUE IN RECTAL CANCER M. Chung 1 , J. Lee 1 , J. Kim 1 , S.U.M.I. Chung 1 1 College of Medicine The Catholic University Radiation Oncology, Seoul, Korea Republic of Purpose/Objective:The traditional standard rectal cancer to irradiate gross tumor and r fails to cover the centrally positioned recta dose without hot spots in the small bow comparative treatment planning study to three-dimensional conformal radiotherapy technique improves target dose distribut avoidance for rectal cancer. Materials and Methods: Thirty consecutive were included. Twenty two patients were pr patients were salvage aim for recurrence in target volume (GTV), rectum, bladder, small outlined on the radiation therapy planning co prone position. Clinical target volume to i pelvic nodal chain and planning target volum set up errors were created on radiation tre We made two plans – standard four field ra and field-in-field technique (FIFT) – for coverage of the PTV with the 95% isodose li bowel not exceeding 107% of the prescriptio of standard four fields included PTV by landmarks on digitally reconstructed radiogr of original set of fields is reduced and the reduced field size was designed in the same of the prescribed dose in 4FRT. The cGy/fraction. Dose-volume histogram of the bowel was compared between two technique Results: Mean dose of GTV, CTV, PTV were significan cGy, 181.2 cGy, 181.3 cGy) than 4FRT (180 cGy) (p < 0.001, p = 0.001 and p = 0.002, receiving more than 100% of prescribed dose were significantly increased from 70.1%, 7 90.8%, 84.3%, 83.8% in FIFT (p < 0.001, p respectively). On the other hand, FIFT signi of small bowel (4FRT=22.4%, FIFT=21.7%; p= bowel (4FRT= 189.9 cGy, FIFT= 188.8 cGy; p= median 2 additional in field portals (range, 6.5x13.2cm in field portals (range, 4x4-12 unit of additional in field portals was 5 (range Conclusions: A significant dosimetric advanta 4FRT in whole pelvic irradiation for rectal ca of target covering and small bowel sparing. using FIFT could be an alternative choice IMRT. ESTRO 31 THERAPY USING FIELD-IN- of Korea, Department of f d four-field technique in regional lymphatics often al cancer with prescribed wel. We carried out a determine whether the with a field-in field tion and normal tissue e rectal cancer patients reoperative aim and eight n anastomosis site. Gross bowel, femur head were omputed tomography with include mesorectum and me to account for patient eatment planning system. adiation technique (4FRT) each patient to ensure ne and to limit the small on dose. The field border the guidance of bony aphs. In FIFT, the weight second set of fields with e angle to avoid the 103% prescribed dose is 180 GTV, CTV, PTV and small s. ntly higher in FIFT (182.9 .8 cGy, 180.1 cGy, 180.4 respectively).The volume (V100) of GTV, CTV, PTV 73.2%, 74.4% in 4FRT to < 0.001 and p = 0.001, ificantly reduced the V95 =0.005)and Dmax of small =0.011). In FIFT, we used , 1-4), median field size x18cm). Median monitor e, 2-14). age of FIFT over standard ancer was shown in terms . Conformal radiotherapy for novel technique like

Antiquing process

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