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The use of compensators in order to achieve desired dose distribution had a long history and is well-established technique in radiation therapy planning. Although the use of linear accelerators with multileaf collimators diminished need for compensators it is reported [1] that the use of compensators still offers some advantages, especially regarding spatial distribution. The production of compensators, either for simply tissue compensation or as an alternative way to accomplish intensity-modulated radiotherapy (IMRT), remains common practice [2-5]. There are several different methods of calculation for compensator’ s shape. An alternative method is suggested. The method is based on Cunningham's modification of Clarkson's method [6] to calculate scattered radiation in beams with inhomogeneous cross-sectional dose distribution. It is well known that the total dose distribution of radiotherapy beams is consisted of the contributions of the primary beam attenuated by the tissue layer and the scattered radiation which is generated by the primary radiation in single and multiple photon scatter events. Since the scattered component could be represented as a function of primary, the central point of the method is numerical estimation of the primary distribution required achieving desired total distribution. Now using calculated primary distribution the shape of the modulator could be determined. In this way the contribution of the scattered component is validate in more accurate way than using effective attenuation coefficients which was common practice. The method is verified in various clinical situations and compared with standard method. The accuracy was better at least 2%, depending on geometry. Namely, more complex geometry results in higher gain in accuracy of our method comparing to the standard method. References [1] S.X.Chang, T.J.Cullip, K.M.Deschesne, E.P.Miller and J.G.Rosenman, Compensators: An alternative IMRT delivery technique J.Appl.Clin.Med.Phys. 2004, 5, 15-36. [2] J. Meyer, J.A. Mills, O.C.L.Haas, K.J. Parvin and K.J.Burnham, Some limitations in the practical delivery of intensity modulated radiation therapy, Br.J.Radiol. 2000, 73, 854-863. [3] S.X.Chang, T.J.Cullip, K.M.Deschesne, Intensity modulation delivery techniques: ‘ Step&shot’ MLC autosequence versus the use of a modulator Med.Phys. 2000, 27, 948-959. [4] V.N.Hansen, P.M.Evans, G.S.Shentall, S.J.Helyer, J.R.Yarnold and W. Swindel W, Dosimetric evaluation of compensation in radiotherapy of the breast: MLC intensity modulation and physical compensators Radiother.Oncol. 1997, 42, 249-256. [5] D.M.Dimitriadis and B.G.Fallone, Compensators for intensity-modulated beams, Med.Dosim. 2002, 27, 215-220. [6] J.R. Cunningham, Scatter-Air Ratios, Phys.Med.Biol. 1971, 17, 42-51.

U liječenju limfoma, kao osnovni terapijski modaliteti, upotrebljavaju se radioterapija i/ili kemoterapija. Liječenje ovisi o vrsti limfoma, stupnju proširenosti bolesti i općem stanju bolesnika. Radioterapija se primjenjuje s kurativnom ili palijativnom namjerom i to kao jedini način liječenja ili u kombinaciji s drugim metodama liječenja. U bolesnika oboljelih od Hodgkinova limfoma (HL) zračenje se provodi kao jedina terapija u stadijima bolesti I i IIA bez nepovoljnih činitelja rizika. Takodjer, u fazi kliničkog testiranja je liječenje ranih stadija HL (I i IIA) i samo s kemoterapijom ili združeno s radioterapijom. Kada se zračenje primjenjuje kao primarna radikalna metoda liječenja (stadiji I i IIA), ciljni volumen zračenja, osim regije/a s klinički zahvaćenim limfnim čvorovima, obuhvaća i klinički nezahvaćene limfne čvorove susjednih regije, a sa ciljem njihovog profilaktičkog ozračenja. Primjeri takvih proširenih polja zračenja su npr. “plašt polje” i polje “obrnuti ipsilon”. Kod primjena radioterapije u kombinaciji s kemoterapijom, ciljni volumen ovisi kako o stadiju bolesti tako i o broju kemoterapijskih ciklusa, odnosno o tome da li je uloga radioterapije samo kontrola klinički zahvaćenih regija ili i regija s mogućom subkliničkom bolešću. U liječenju bolesnika oboljelih od ne-Hodgkinovih limfoma (NHL) najčešća je kemoterapija. Radioterapija se s kurativnom namjerom kao jedini modalitet liječenja primjenjuje u bolesnika koji po histopatološkom razvrstavanju imaju NHL indolentnog tipa i stadija bolesti su I ili II u kontinuitetu. Ciljni volumen zračenja obuhvaća klinički zahvaćenu regiju tijela; u ciljni volumen mogu se još pridati i susjedne klinički nezahvaćene regije. U viših stadija bolesti ili kod drugih, agresivnijih NHL primjenjuje se kemoterapija sama ili nadopunjena sa zračenjem.

Radioterapijsko planiranje računalom

Primjena stereo-radiografije u radioterapiji