137

SOLID-STATEDETECTOR DOSIMETRYFOR MALEGONADS RADIOPROTECTION IN RADIOTHERAPY

M. Bignardi', G Catalano', F. Corrado-, P Feroldi2,F. Luraschi-,M. Prina', S. Tonoli''Radioth , 2Med. Phys. Dep., SpedaliCivilidi BRESCIA - ITALY

Basic clinical interest and, in some cases, regulatoryrecommendations request measurement or, at least,estimation of the dose to the male gonads in radiotherapictreaments.Subdiaphragmatic, rectal and post-surgical seminomatargettreatments in adults have been taken into account. Theproximity of target volume or the particular request forfertility evaluationmake the problem more relevant.Solid-state detectors give interesting opportunities for invivo dosimetryout of the therapeutic beams.In vivo and in phantom dosimetry have been performed, inorder to set direct data and indirect estimates Ionizationchamber measurements have been collected and used asreference values for semiconductors calibration Alsothermoluminescent dosimetry has been used for acomparison.Feasibility, accuracy and reproducibility results show thatthe use of solid state dosimetry for radioprotection inradiotherapy is very stimulating A procedure for theevaluationof male gonads dose in radiotherapy is proposedSolid-state and thermoluminescent dosimetry in someclinical cases have been compared with our protocolevaluations, showingencouragingresults

139

r.t, KJcperIIIIllI oIla1ui,iiitba J\IIIoIIIn DJ-k bdIothenp,

DYN.QAD JmaaiDI <Jroap: Jl~,M. MooDeyl, P,VIDdcDHeawIl3,Z.IqoIl1III, J. VID Dtjt', T.KdI. O.slplll',A. 'nlIIddII', Cde Wap'. O.PuIyiocUIa', B.M1hllqlonlau'. B.PraImoI'

lMelcl1P!l)'IIcI DIpc., t.1UYInIly~ laldaa. LcmdcD. llK. 2AZ-VUB.DliplRadIodInpy,BnIIIeIs. B!LOItlM. 'INBrr. PIInt, GRIlIa!.4Al:1de11i1c1l MdIc:IICeleum,RIlIIalI-.:.pe. A-.IImLe..NImIBRLANDS. 'HIIIIaId UlIYcI*yoI'I'el:11alio1Y. HIIIiI*I, FINLAND.-. tl8lllpllll Jl!lyIIcI. KIroIbIID IIaIpiIII. S1ldIIaIm, SWBDBN, 'Dc:pc. 01~ Ii:NIIl:Ir:Ir Mdc:me. UIM*y 8llIpIlal CJla, GIll, BI!LCJIUM.~~ Dlipl,UWlnkyolPlall, PIInt, CllUlIlCB.

DYNARAD IsaJ!urclIaD C'.alIcer1ed AaIaa.~wI1IIlIlI CIIn'lIIt 1IIll

Illd~oI~~wIdIIDdieI!lIropoID t1DIoa.DYNARADCIIIIaII)' l1li26~ pIIdclpIItIIa1'IIpI'ClIOIIiI13CIllIIlIriIIl'ClIllllarop& 1'IIIl1llllliDlGroap Isa 1Ub-pJup 01DYNAllADClClIlllnId wIIIIlD lIII*lI ollllllmlllal c:IIIIIl illvCllved ill DyIIIIIlIc1lIdkldaenpy. 1'IIIlGroap _1dliadIId__~ IpICIac to imaIIAIIIId dIiI aIlIlnclllmlllO*-dII prollIa oIp1Ol11Jc1Da~y1."U"'1oa oIda'Ipy raIIMd IltormIdoa 011110 a..1JDIIe. 1'IIIl-uy01ClIIlIbiIIIIII idlnaIlIClII, IIIllaIparatlq pllIIIIIIric, t'uIIcdClIIallild IIplIIIaldlra,iulo ClIIIimIpb' pIIIIIllaa II~ 1'IIIl1llOdllldcl faroIlraiDIIIi1bII_1I'll~ U beiDa CclmpIl8cI 'I'aaqnipIIy(CT) orl1tenlaIIvdyDIpalT~ (DTS), PoOClII·JlIDc:lrClII 'I'aaIoIfIplIy (PET) orS_PIxxClII JlmIIIIoa CcIIIIpuIId1'clIIIDppIIy (SPIlC'I)IIld MtpeticReIaaaace IIIIIIIDI (MIU). Oae oldie IYIIIIIIlIimI oltlalmlliDlll'OUP Is110 full tboiDfcnIIaIiClIIl'ClIll tMlillC1llllCJ* II c:r.- aliDllo data..1IIOIt__II d)'llllllle radIadBapy1I'IaIIIIL 'l1III1pIlI'ClICII1bouId Joad tollllcnadClII oIllla11l11t1P1* viIlWIudClII oIl1n1Cl111'1, CllDIllanIlld pIIyIIaIotk:al1lIrldIo:a wbldl CXlIIId euI17 beraIIMd 10I!IlIaIaIar"-' l'IdIolblnpytI'eIIlI*I~. 1111 fIlI1bwIDI~.....1IlI eadyIillpWDce oItbeI!IIIIIDI <JnlIIp i1111l1 palWIIIIlI oIlIIII ailII.

138

THE TARGETED STEREOTACTIC RADIOSURGERY: AN OPTIMIZEDTREATMENT TECHNIQUE FOR PATIENTS WITH INTRACRANIA.VASCULAR MALFORMATIONS.

Prof. Dr. R. DATTA and Prof. Dr. S. DATTADepartment of Radiology, LSU School of Medicine,P.O. Box 33932, Shreveport, Louisiana-71130-3932, USA.

Stereotactic radiosurgery (SRS), a relatively new special treat­ment technique, has already occupied a prominent place in theexpanding armamentarium of therapeutic interventions of vas­cular abnormality associated with intracranial malformations.Usually, a massivedose of ionizing radiation, with single fractionis given by this procedure. Unlike multifractionated therapy. avery large single dose of radiation reduces the therapeutic ratio(i.e. radiobiologicallycontraindicated).Various different phys­ical methods and treatment devices have been developed to deliv­er highly localized dose distributions requiring targeting accuracyon the order of a millimeter. The physical accuracy of treatmentoutcome is comparable between methods. The physical aspects oftreatment techniquesof various methods and their impact on thetreatment and radiobiological considerations will be discussed.The technique appears to be applicable to patients with intracrani­al neoplasms in whom tumor volume is small and surgically inac­cessible, and in whom limited or no prior chemotheraphy hasbeen administered. What is stereotactic radiosurgery, how itworks, how it differs from stereotactic radiotherapy (SRT), whoare the potential candidates for treatment, and few other excitingquestions will be addressed to help physicians and physicists theappropriate use of this new emerging sophisticated technology.

140

TWO·DiMEfrnO~L VERSUS THREE·DIMENSIONAL TREATMENTPLANNING OF TANGENTIAL BREAST IRRADIATION.

E.M.F. DAMEN, I.A.D. BRUINVlS, B.J. MIJNHEERThe Netherlands Cancer Institute / Antoni van Leeuwenhoek Huis,Amsterdam, The Netherlands

Purpose: Full three-dimensional (3-D) treatment planning requires 3-Dpatientcontoursand densityinlormabon, derived e~her from CTscanningor from other 3-Dcontouring methods. These contouring techniquesaretime consuming, and are olten not available or cannot be used. Two­dimensional (2-D) treatmentplanning can be performed usingonlya fewpatientcontours,made with muchsimplertechniques,incombination withsimulator images for estimating the lung position. In order to investigatethe need lorlull 3-Dplanning, we compared the performance 01botha 2­D and a 3-D planning system in calculating absolute dose values andrelative dose distributions in tangential breast irradiation.Methods: Two breast-shaped phantomswere used in thisstUdy. Thefirstphantomconsists 01 a polyethylene mould, filled with waterand cork tomimic the lung.An ionization chamber can be inserted in the phantom etfixed positions, The second phantom is made 01 25 transverse slices 01polystyrene and cork,made with a computerized milling machine from CTinlormation. Inthis phantom, films can be Inserted inthree sagittal planes.Both phantoms have been irradiated with two tangential 8 MV photonbeams. Themeasured dose distribution has been comparedwith the dosedistribution predicted by the two planning systems.Results: In the central plane, the 3-D planning system predicts theabsolute dose with an accuracy 010.5 - 4%. The dose at the isocentre 01the beams agrees within 0.5%with the measured dose. The 2-D systempredictsthe dose with an accuracy010.9 - 3%.Thedose calculated at theisocentreis2.6%higherthan the measured dose, because missing lateralscatter is not taken intoaccount inthisplanning system. Inoil-axis planes.the calculated absolutedose agrees with the measured dose within 4%lorthe 2-D system and within 6% lor the 3-Dsystem. However, the relativedose distribution is predicted better by the 3·D planning system.Conclusions: This study shows that an algorithm lor the correction 01missing lateral scatter is an essential part 01 the treatment planning 01tangential fields, Furthermore, ~ is shownthat a multi-plane 2-D calculationmight be su1licienUy accurate in most cases.

837