107Dose specification evaluation in temporary and permanent prostate implants

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107Dose specification evaluation in temporary and permanent prostate implants
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  105 RADIATION THERAPY OF LOCALLY ADVANCED ESOPHAGEAL CANCER BoA'~dar~ O.S., Shishkina V.V., Ivankova V.S., Gavrilenko M.F., Pidloubna T.G., Tchornay A.Y. Ukrainian Institute of Ontology & Radiology, Kiev, Ukraine. Ninety four cases of squamous cell carcinoma arising from the thoracic esophagus (stage III-IV) were treated by radiation therapy from 1991 to 1996 at the institute. First group of 32 patients was treated by external beam radiotherapy (EBRTI to a dose 30 Gy/15 fractions/3 weeks. After 2 weeks rest they continued to receive treatment with 6°Co--HDR intracavitary braehytherapy (IBT) to a dose 20 Gy delivered in 4 sessions of 5 Gy each week apart. Simultaneously these patients got external beam irradiation to a dose 20 Gy/10 fractions/2,5 weeks. Second group of 26 patients ,'.,as treated by EBRT to a dose 30 Gy/5 Gy per fraction/6 fractions per week. IBT was provided in 2-3 days after EBRT. The average dose delivered by IBT (Seleetron, source ~37Cs, pellets LDR-MDR) was 15 Gy, the dose per fraction was 5 Gy twice per week. The dose was calculated at 0,5 cm below esophageal mueosa at both groups. For 36 patients of 3rd group EBRT was done to a dose of 51-54 Gy/17-18 fractions/3,5 weeks. All patients were assessed symptomatically, endoscopically and roentgenologically every 3 month. There was marked difference at the end of 1 year in relief of dysphagia and local control. Median survival time was 21,1; 18,9 and 12,1 month at 1st, 2nd and 3rd groups accordingly. The level of benign radiation- induced esophageal uleeration's and strictures in IBT- groups did not exceed such in EBRT-groups. The HDR-IBT is a high effective and safe treatment method, such as LDR-IBT for non-operable esophageal carcinoma 107 DOSE SPECIFICATIm.~I EVALUATION IN TEMPORARY AND PERMANENT PROSTATE IMPLANTS Sharad K Saraf Ashraf Youssef Daniela Gidea- Addeo Sameer Rafla; Mew York Methodist Hospital Department of Radiation Oncology Brooklyn New York USA Temporary implants using It-192 radioactive sources and permanent implants using 1-125 or Pd-103 radioactive sources have been performed to treat intermediate stage prostate cancer. The selected dose rate and total dose should result in the delivery of adequate target coverage, homogeneous dose distribution within target and minimum irradiation of surrounding normal tissues. We have analyzed temporary and permanent implants using three volumetric indices namely, CI for target coverage defined as representing the °A of target volume receiving dose rates equal to or greater than the reference dose rate, HI for dose homogeneity defined as % of the target volume receiving dose rates between 100 and 150% of the reference dose rates and El for normal tissue sparing which is defined as the volume outside the target volume receiving dose rates equal to or greater than the reference dose rate. For temporary implants it has been found that by optimizing the target coverage (el), homogeneity of dose inside the target volume (HI) and reducing the surrounding normal tissue volume (El), a dose rate can be chosen to deliver the total dose. For permanent implants, minimum peripheral dose (mPD) has been obtained which covers the target volume and, CI, HI and El are calculated. By varying the mPD it is possible once again to obtain the optimized implant. Detailed dosimetric evaluation has been performed to guide the dose evaluation with respect to the target coverage with CI, HI and EI volumetric irradiation indices. 27 106 PHYSICAL AND TECHNICAL ASPECTS OF A TECHNIQUE FOR TREATING CA PROSTATE USING HDR BRACHY THERAPY. GiSran Sernbo, Lena Marie Lundberg, Anders Kristensson and Kerstin Mdntzing, Sahlgrenska University Hospital G~teborg, Sweden At Sahlgrenska University Hospital patients with ca prostate are treated with external conformal radiotherapy combined with brachy therapy (BT) using a GammaMed HDR 192 Ir-afierloading device. ApproxHrJalely one week before BT a Iransreelal ohra sound (TRUS) cxamlnanon is carned out. huages of tile prostate gland are taken with a spacing of 5ram. These form the basis for the preplan. A modified video camera head Is used as probeholder for the TRUS. This holder allows us to obtain ultrasound images in various directions. To be able to use the preplan it is of great importance that we are able to reproduce the TRUS on the treatment day. The geometry of the prostate gland and of the inserted needles must be well known. During treatment it is extremely important that the needles are located according to the treatment plan. Even very small deviations in any direction will have a large influence on the absorbed dose distrubution. We therefore have developed a rigid matrix fixation with a 5mm spacing m the horisomal and the vertical direction, and a fixatton in the needle direction. The needles are positioned in the matrix The matrix is mounted with the needles parallel to the ultra sound probe. An image of the matrix is superimposed on all ultra sound slices. The matrix will serve as a guide during the insertion of the needles. Thts poster will describe physical and technical aspects of this techmque 108 INTRACAVITARY BLADDER HIGH DOSE RATE B RACHYTHERAPY: A FEASIBILITY STUDY Momca B.(1), Bonetta A.(2), Zingoni A (3). Capelli G.(3), Magri S.(3) t l l Divmione di Radiolerapia and (31 Servizio d1 Fislca Sanitaria. A=. Istituti Ospedalieri. Cremona; 12i Sem izio di Radioterapia. A .:. ASMN, Reggio Emilia; Italia. Alms and background. This study reports a preliminary experience on high dose rate brachytherapy (HDR-BR'I') in bladder cancer using a non inva.sive technique with a new specific transuretheral catheter The Authors (AA) have developed a prototype of intracavitary catheler- applicator to perform the bladder irradiation, sparing pelvic tissues and organs at nsk. Material and methods. The procedures of this kind of treatment are: 1) ttausurethral placement of the catheter; 2) simulation with orthogonal radiograms; 3) TC to define the treatment volume (dose points): 4) treatment planning study with opttmisation on point, to obtain a dose distribution as homogeneous as possible The dose is prescribed in these points chosen around the tumor (or in other points at 1 cm from the mucosa if the tumor is not well definable). Dose pre.%'ribed is 10 Gy. 13 patients wese treated. 9 were irradiated (15-21 days before cystectomy) to evaluate the BRT effects on tumor and normal tissues (anatomo- pathoh~gleal analy.'sis). I received a Ixxt, t after EBRT. 3 had a palliative trcaUlleUt Ior hematuria, Results. All die patients were easily irradiated. Tile cysteclon'ties were performed without complications; the bladder (mueosa and muscular wall) had nail radiotnduced IOXICily; IIl|t' paticnl had a tomplclc hl:~tologlc re~,pClll~.e. Tile hilellt~tUrl;i wilh well colur~lled (;l'¢erage ~. 11 months). Dlsctt,~,ilan, The AA believe that HDR-BRT can have a role in bladder cancer care. In fact, this treatment is easy to perfomt with our specific catheter, obtaining an acceptable dose distribution and a low incidence of acute side effect. At the data, our experience is in progress, evaluating the effects of different doses per fraction and total doses. In our opini,,m. the role of HDR-BRT in bladder cancer has to be defined, especially in following lields: 1) pre-operative treatment in infiltrating tumors; 21 palliative treatment m advanced studies; 3) boost after EBRT in radical irradiation lid reduce pelvic late side effects); 4) pallianve irrathation in hx:alised tumor not responding to topic treatment (the goal is to delay the cystectomy).
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