An anthropomorphic Phantom, a female trunk, was built with a natural bone structure and experimental material coated, glycerin and waterbased material called JJT to build soft tissue equivalent to the muscle of human tissue, and a polymer (styrofoam) to build the lung as critical organ to simulate the treatment of breast cancer, with high dose rate brachytherapy (HDR) and sources of Ir-192. The treatments were planned and calculated for the critical organ: Lung, and injury of 2 cm in diameter in breast with MicroSelectron HDR system and the software Plato Brachytherapy V 14.1 of the Nucletron (Netherlands) which uses the standard protocol of radiotherapy for brachytherapy treatments. The dose experimentally measured with dosimeters TLD-100 LIF: Mg; Ti, which were previously calibrated, were placed in the same positions and bodies mentioned above, with less than 5% uncertainty. The reading dosimeters was carried out in a Harshaw TLD 4500.The results obtained for calculated treatments, using the standard simulator, and the experimental with TLD-100, show a high concordance, as they are on average a § 1.1% making process becomes in a quality control of this type of treatments

De La Espriella Vélez, N.

Sánchez Caraballo, A.

Torres Hoyos, F.

English

Repositorio de la Universidad de Córdoba

   Revista Mexicana de FísicaISSN: 0035-001Xrmf@ciencias.unam.mxSociedad Mexicana de Física A.C.MéxicoTorres Hoyos, F.; De La Espriella Vélez, N.; Sánchez Caraballo, A.Quality control of the breast ca treatments on HDR brachytherapy with TLD-100Revista Mexicana de Física, vol. 60, núm. 6, noviembre-diciembre, 2014, pp. 409-413Sociedad Mexicana de Física A.C.Distrito Federal, MéxicoAvailable in: http://www.redalyc.org/articulo.oa?id=57032591001   How to cite   Complete issue   More information about this article   Journal's homepage in redalyc.orgScientific Information SystemNetwork of Scientific Journals from Latin America, the Caribbean, Spain and PortugalNon-profit academic project, developed under the open access initiativeRESEARCH Revista Mexicana de Fı´sica 60 (2014) 409–413 NOVEMBER-DECEMBER 2014Quality control of the breast ca treatments onHDR brachytherapy with TLD-100F. Torres HoyosMaterials and Applied Physics Group, Universidad de Co´rdoba,Co´rdoba 230002, Colombia Universidad Cooperativa de Colombia, Monterı´a, Colombia.e-mail: franciscotorreshoyos@yahoo.comN. De La Espriella Ve´lezGrupo GAMASCO,Universidad de Co´rdoba, Monterı´a, Colombia.A. Sa´nchez CaraballoDepartamento de enfermerı´a,Universidad de Co´rdoba, Monterı´a, Colombia.Received 6 January 2014; accepted 25 August 2014An anthropomorphic Phantom, a female trunk, was built with a natural bone structure and experimental material coated, glycerin and water-based material called JJT to build soft tissue equivalent to the muscle of human tissue, and a polymer (styrofoam) to build the lung as criticalorgan to simulate the treatment of breast cancer, with high dose rate brachytherapy (HDR) and sources of Ir-192. The treatments were plannedand calculated for the critical organ: Lung, and injury of 2 cm in diameter in breast with MicroSelectron HDR system and the software PlatoBrachytherapy V 14.1 of the Nucletron (Netherlands) which uses the standard protocol of radiotherapy for brachytherapy treatments. Thedose experimentally measured with dosimeters TLD-100 LIF: Mg; Ti, which were previously calibrated, were placed in the same positionsand bodies mentioned above, with less than 5% uncertainty. The reading dosimeters was carried out in a Harshaw TLD 4500.The resultsobtained for calculated treatments, using the standard simulator, and the experimental with TLD-100, show a high concordance, as they areon average a ± 1.1% making process becomes in a quality control of this type of treatments.Keywords: TLD-100; anthropomorphic phantom; brachytherapy HDR; breast.PACS: 87.53. Jw; 87.66.Xa; 87.66.Sq1. IntroductionIn the use of ionizing radiation in medicine, (radiother-apy, diagnostic radiology, nuclear medicine), is indispens-able knowledge of the absorbed dose given to the patient andtheir determination should be very rigorous, so the Interna-tional Commission of Radiological Units (ICRU) in its report59 [2,5] recommends an accuracy of ±5% in the administra-tion of the absorbed dose in the target volume if the main ob-jective is the elimination of the primary tumor with the leastpossible damage to nearby healthy tissue, as is the radiationtherapy. It is necessary to know the physical characteristicsof the sources of ionizing radiation used in certain treatments,with which defines the conditions for using certain dosimetrysystem [3]. In this work, of interstitial brachytherapy, ther-moluminescent dosimeters TLD-100 were used for present-ing the following features: rods shape, size of 1.1 mm diam-eter and 6 mm in length, high precision, good environmen-tal stability and human tissue equivalence, a wide sensitivityrange good spatial resolution [1], which is vital for this typeof dosimetry given the appearance of high-dose gradients inthe implementation of treatments of high-dose brachytherapyin breast tumors. The objective of this work is to build an an-thropomorphic phantom that allows ensuring the quality ofthe interstitial breast treatments, i.e., control and estimationof the dose prescribed, using high dose rate and detectorsTLD-100. The paper is organized as follows. In Sec. 2 andin the subsections therein, the general methodology is pre-sented. The construction of the anthropomorphic phantom,based on the natural bone structure and material JJT, alsopresent the planning of the treatments. The calibrations ofthe dosimeters (TLD-100) are presented in Sec. 3, with em-phasis on the Co- 60. Results and discussion are presented inSec. 4. The conclusions are presented in section Sec. 5.2. MethodologyBuild an anthropomorphic phantom, requires that the mate-rial used is equivalent, biologically, to human muscle tissue,in our case the Simulator was built using a natural bone struc-ture corresponding to the chest of a 42-year-old woman, av-erage age of patients treated at the Instituto Nacional de Can-cerologı´a (INC), Colombia. The phantom is shown in Figs. 1and 2.2.1. Construction of the anthropomorphic phantomThe experimental material, used in construction breast andlining of the chest is according to the specifications of theICRU 44. [5], constituent elements of our anthropological410 F. TORRES HOYOS, NICOL ´AS DE LA ESPRIELLA V ´ELEZ AND ALVARO S ´ANCHEZ CARABALLOFIGURE 1. Natural bony structure of the torax used in the construc-tion of the antropomorphic phantom.FIGURE 2. Antropological phantom with the respective breast im-plant for the treatment of high dose rate.phantom as shown in Fig. 2 , was subjected to a physical,chemical, and radiological analysis by J. Va´squez et al. [4],whose results show that JJT material is suited to be used asreplacement tissue and the construction of anthropologicalphantom.2.2. Calibration of TLD- 100 Crystals with the energyof Co-60With the energy of Co 60, the crystals were irradiated with adose of 50 cGy in a Theratron 780, using a field of referenceof size 10 × 10 cm2, and sensitizing with five irradiations,without performing readings interspersed with an annelingfrom 1 hour to 400◦C followed by two hours at 100◦C, atintervals of 12 hours irradiation [6]. To carry out this heattreatment was used oven Lindberg/Blue UP150. In order tocalculate the dose is proceeded according to:D =MNcalKchipKlinKSSDKfield (1)where D is the dose read on the crystals, M is the reading incoulomb (C) of the crystals. This process was held with theFIGURE 3. Calibration of TLD-100 with Co 60(average energy1.25 MeV).reader Harshaw TLD 4500, manufactured by Bicron usingfor this purpose the planchet heating equipment. During theprocess a preheat temperature of 50◦C was used, from whichthe data acquisition is performed, at a rate of 10◦Cs untilreaching a maximum temperature of 300◦C, followed by an-nealing at 300◦C . To eliminate the contribution due to in-frared heating and reducing the effects of moisture during theprocess, all readings were carried out on a atmosphere of highpurity N2. Ncal is the conversion factor for units of Coulomb(C) in dose units (Gy); Kchip is the ratio between the aver-age reading of crystals and individual reading of each crystal,Klin is the correction factor for the nonlinear response of theCrystal with the dose, KSSD is the correction factor due to thedistance source -surface; Kfield is the correction factor due tothe size of the field. Calculated performance shows a highcorrelation with that used in the calculation Prowess of theInstituto Nacional de Cancerologı´a (INC) program and thecalculated time to deposit the dose of 50 cGy was 0.59 min-utes the date of calibration. The next process was radiate,with specific dosage, groups of 4 crystals, obtaining an aver-age reading for each group of crystals. The Fig. 3 shows thecurve obtained according to the readings of the TL signals ofthe crystals, with a squared correlation coefficient r2 = 0.999and given by the equation:DL = 34 cGy + 3.7cGyµCL(µC). (2)Where DL is the calculated dose and L is the reading of theCrystal.2.3. Calibration of the TLD with the energy of Ir - 192(0.38 MeV)Connected a 6F endobronchial catheter to the HDR unit sothat through it the source Ir-192 will be moved and thus todetermine their point of positioning which was verified withan X-ray image. The crystals were placed in groups of fourwith a buildup of 2 mm material thickness JJT, on the trans-verse axis of the source at a distance of 10 cm [7]. SuppliedRev. Mex. Fis. 60 (2014) 409–413QUALITY CONTROL OF THE BREAST CA TREATMENTS ON HDR BRACHYTHERAPY WITH TLD - 100 411FIGURE 4. Calibration of TLD-100 with Ir 192 (average energy0.38 MeV).doses varied in the range of 300 to 750 cGy, obtaining thecurve shown in Fig. 4, with a quadratic correlation coeffi-cient r2 = 0.998 and equation given by:DL = 44.2 cGy + 14.4cGyµCL(µC). (3)Where DL is the calculated dose and L is the reading of thecrystal.2.4. Treatments PlanningIt was implanted in the anthropomorphic phantom the systemconsisting of two external fixing strips of 80 mm in lengthand 3.5 mm thick, each one, and twelve needles vector ofstainless steel 120 mm in length, as shown in Fig. 2. Is ver-ified the correct location of the implant using fluoroscopy.Catheters were introduced with fictitious sources in the pre-scription points, located between the two central needles and5 mm deep level below it in order to determine the placementFIGURE 5. Computed axial tomography used for the location ofthe crystals in the anthropomorphic phantom.FIGURE 6. Isodose curves for interstitial breast treatments withnine needles for vector doses between 400 to 700 cGypoints of the crystals where the dose is measured, as shownof red color in Fig. 5.Treatments made planning for a range of doses between400-700 cGy, for a tumor volume 5.56 cm3 and taking intoaccount the spatial coordinates of each of the needles, so cal-culate with the planning system, Plato Brachytherapy [8], theisodose curves which are shown in Fig 6.3. Results and discussionsFigure 4 which represents the calibration of the TL crystalswith source Ir - 192 shows that the crystals have a linear be-havior in the dose range of 300-750 cGy, Which is in goodagreement with the works done by S.W.S McKeever et al andJ.L Mun˜iz [12, 13], the background radiation present may berelated to factors such as high relative humidity (70%) androom temperature (30◦C), where the calibration was done.The validation of the method used in the earlier results wasmade with a group of dosimeters whose values are shown inTable I, whereDsystem is the calculated dose with the planningsystem Plato Brachytherapy. According to Table I the max-imum difference between the measured dose with the TLD-100 and the calculated dose with the planning system isTABLE I. Validation of the method of calibration of dosimetersTLD-100 with Ir-192.Dsystem(cGy) DL(cGy) DLDsystem300 296.9 0.986350 345.5 0.987400 396.6 0.991450 444.5 0.987500 491.4 0.987550 542.9 0.992600 595.8 0.993650 645.5 0.99700 692.0 0.988750 745.1 0.993Rev. Mex. Fis. 60 (2014) 409–413412 F. TORRES HOYOS, NICOL ´AS DE LA ESPRIELLA V ´ELEZ AND ALVARO S ´ANCHEZ CARABALLOTABLE II. Comparison of the calculated dose with the planningsystem and measures with TLD - 100 in the treatment of breast.Dsystem(cGy) DTLD(cGy) DTLDDsystem700 673 0.961650 637 0.980600 584 0.973500 487 0.974400 393 0.982FIGURE 7. Glow Curve of TLD - 100 at a heating rate of 1◦C/sbetween 50 and 300◦C1.4 %, results that are within the range of validity for this typeof procedure [9].The Table II compares the calculated doses with the plan-ning system and the measures with the TLD -100 in the treat-ments prescribed breast between the center two needles ofthe deep level and 5 mm below the same. Table II shows thatthe maximum difference between the dose measurement withthe TLD - 100 and calculated by the planning system differsby 4%, which is consistent with the expressed in the ARCALXXX for this type of treatment [9].As the dosimeters were reused, it was observed that itssensitivity varied, this is due to surface effects, since it can begiven several mechanisms affecting TL sensitivity. The mostimportant are the changes in light transmission due to con-tamination, scratches and gaseous absorption can also alterthe intrinsic efficiency or lead to no radiation-induced signals.Another possible cause may be largely the spatial distributionof the concentration of traps. As defects are dependent on thelevel of impurities in parts per million and, to a lesser extent,on their heating and thermal history, it is very difficult to setthe properties of a TL material. This leads to batch effects.For optimum precision calibrations must be performed foreach individual dosimeter. [1,10]. Dosimeters irradiated per-manently keep all information provided, resulting in a grad-ual loss of dormant thermoluminescence signal. This shouldbe corrected prior to the assessment being adopted heat treat-ments.Figure 7 shows the glow curve of one of TLD - 100 (LiF:Mg, Ti) used, the reading was made at a heating rate of 1◦C/s,in the temperature interval [50-300]◦C. To observe a betterdefinition of the peaks of the crystal was done a simplifiedanalysis with the WinREMS program which is able to solvea complex curve of thermoluminescence and adjust the ex-perimental points using the kinetic theory of first order [13]the result of this analysis is the clearly defined the peaks 2, 3,4 and 5.The use of pre- irradiation annealing to eliminate al-most completely the picks 2 and 3, significantly increasesthe peaks 4 and 5, therefore, to eliminates post- irradiationfading in TLD -100. The correlation between peaks 2, 3 andpeak 5 led Cameron et al [1]to suggest that peaks 2 and 3 areassociated with (Mg2+) dipoles while suggesting that peak5 is a higher order cluster of three dipoles (trimer). Morerecently, it has been suggested that the trimer is spatiallycorrelated with (Ti+3) ions to form an even larger trapping-recombination complex [14].4. ConclusionsIn this work of quality control of the treatments of breastCa with HDR dosimetry using TLD - 100 were simulatedten cases for prescribed dose. The results of the dose mea-sures show great similarity with to those calculated with theplanning system Plato BRACHYTHERAPY V. 14.1 becausethey present a maximum difference of 4% , which makes ita good quality control system for treatments of HDR inter-stitial brachytherapy which allows us to affirm that the pre-scribed doses are given correctly to the patients and do notexceed the dose of tolerance for breast [9, 11]. The calibra-tion curve of crystals in material JJT, with the average energyof the Ir - 192, with a buildup of 2 mm and distance sourcecrystal 10 cm, show good results to determine the dose inthe range of 0 to 1000 cGy, implying that the dosimetry tech-nique is effective provided that thermal processes for this typeof dosimetry are followed [9].AcknowledgmentsWe express our gratitude to all medical and technical staff ofthe Instituto Nacional de Cancerologı´a (INC) for their collab-oration in the system installation guide needles and locationof the points of dose prescriptions and access to their treat-ment equipment.Rev. Mex. Fis. 60 (2014) 409–413QUALITY CONTROL OF THE BREAST CA TREATMENTS ON HDR BRACHYTHERAPY WITH TLD - 100 4131. J.R. Cameron, N. Suntharalingam, and G. Kenney, Ther-moluminiscent Dosimetry, the university of Wisconsin Press,(Madinson Mirwaukee, and London, 1968).2. ICRU Report 59. Dose and Volumen Specification for Report-ing Interstial Therapy, International commission on Radiationand Measurements (ICRU Publications, Bethesda. USA. 1997).3. TG 43; American Association of Physicist in Medicine(AAPM). Dosimetry of brachyterapy Sources. Med. Phys. 22(1995) 209-239.4. J. Va´squez, G. Murcia, and M.C. Plazas, Caracterizacio´nDosime´trica del material JJT para uso en radioterapia. Trabajode grado, (Universidad Pedago´gica y Tecnolo´gica de Colombia.Tunja 2000).5. ICRU Report 44. Tissue Substitute in Radiation Dosimetry andMeasurement (ICRU Publication, Bethesda. USA, 1989).6. Technical Reports Series 277. Absorbed Dose determination inphoton and electron beams. An International Code of PracticeSecond Edition. International Atomic Energy Agency, (1987).7. Goetsch; Attix; Pearson, Thomadsen.Calibration of Ir 192 HighDose Rate Afterloading Systems. Medical Physics 18 (1991)462-467.8. Plato Brachytherapy Afterloading V 14.1. User Manual, Nucle-tron. Netherlands, (1999).9. ARCAL XXX. Aspectos Fı´sicos de la Garantı´a de Calidaden Radioterapia: Protocolo de Control de Calidad. ProyectoRLA/6/032 (1999). Mejoramiento de la Calidad en Radioter-apia. Ape´ndice J. Tabla J1.10. F. Attix, Introduction to Radiological Physics and RadiationDosimetry, (WILEY-VCH Verlag GmbH & Co. KGaA, Wein-heim, 2004).11. R. Nath, L. Anderson, G. Luxton, Medical Physics 22 (1995)209-234 .12. S.W.S. McKeever, M. Moscovitch, and P.D. Townsend, Nu-clear Technology Publisching (1995) 204-222.13. J.L. Mun˜iz, Me´todos experimentales de dosimetrı´a postal parael control de calidad en radioterapia basados en LiF:Mg,Ti(TLD-100) y LiF:Mg,Cu,P (GR-200): Aplicacio´n de me´todosnume´ricos al ana´lisis de las curvas de termoluminiscencia.Madrid, (1999), 203 h. Tesis Doctoral (Doctor en CienciasFı´sica). Universidad Complutense de Madrid. Facultad de Cien-cias Fı´sicas. Departamento de Fı´sica de Materiales.14. S.W.S. McKeever and Y.S. Horowit, Radiat. Phys. Chem 36(1990) 35.Rev. Mex. Fis. 60 (2014) 409–413

Quality control of the breast ca treatments on HDR brachytherapy with TLD-100

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Quality control of the breast ca treatments on HDR brachytherapy with TLD-100

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