Purpose: Aim of this study is to determine the dosimetric influence of Filtered and Flatting Filt... more Purpose: Aim of this study is to determine the dosimetric influence of Filtered and Flatting Filter Free Photon Beam of 10 MV energy on RA planning for Ca. Cervix. Methods: CT data sets of eleven patients reported with carcinoma cervix were used for RA planning for 10MV _FFB and 10MV_FFFB. RA plans were generated using two full arcs.All RA plans were generated to deliver a dose of 50.4Gy in 28 fractions for PTV and ALARA for OAR’s. All plans were analysed for PTV Coverage, conformity Index, homogeneity index, dose to OAR’s, integral dose to normal tissue and total monitor units were studied. Results: DVH was used to evaluate RA plans for both 10MV_FFB and 10MV_FFFB photon beam. Planning results show a comparable PTV coverage for both energies. Results shows volume of PTV receiving prescription dose were 95.10+ 0.09% and 95.09 +0.11%, and volume of PTV receiving a dose of 107% is 0.45+0.96% and 5.25+8.9%, homogeneity index (HI) were 1.051+0.007 and 1.066+0.008, Conformity Index(CI) were 1.003+0.019 and 1.012+0.013, Mean Integral dose were 2.65+0.34 and 2.60+0.33(*10−5Gy.cm3) for 10MV_FFB and 10MV_FFFB respectively. 10MV_FB shows statistically significant (p<0.05) improvement in mean doses to bladder, rectum, bowel and mean total number of MU’s and also shows remarkable decrease in mean total no. of MU’s by 43.7% in comparison to 10MV_FFFB. There is statistically significant (p<0.05) difference found in CI and HI for 10MV_FB in comparison to 10MV _FFF beam. 10MV_FFFB shows statistically significant (p<0.05) for mean NTID and delivers 1.65 % less NTID in comparison to 10 MV_ FB. Conclusion: 10MV_FB is superior to 10MV_FFFB for rapid arc planning in case of Cervix carcinomas, it offers better target coverage and OAR’s sparing, comparable mean Integral dose to normal tissues and 10 MV_ FB also produced highly conformal and homogeneous dose distribution in comparison to 10MV_FFFB.
To compare the Collimator scatter factor (Sc), Phantom scatter factor (Sp) and Total scatter fact... more To compare the Collimator scatter factor (Sc), Phantom scatter factor (Sp) and Total scatter factors (Sc,p) of 6MV FFF and energy matched 6MV FFF (6MV eqFFF) METHODS: The flattening filter and primary collimator are the major sources of producing the scattered radiation. In this study, the field sizes from 5 × 5 cm2 to 40 × 40 cm2 compared for 6MV FFF and 6MV eqFFF. We measured Sc,p with CC 13 chamber at the depth of 10 g/cm2 using IBA blue water phantom and Sc measured with CC 13 chamber at the depth of 10 g /cm2 using columnar phantom (TG 74) for 6MV FFF and 6MV eqFFF x-ray beams from a Siemens - ARTISTE(6MV eqFFF ) and Varian True beam (6MV FFF) linear accelerator. The Sp values derived from the Sc,p and Sc Values. All the values of Sc,p, Sc and Sp are normalized to 10 × 10 cm2 field size. The measured values of Sc,p for 6MV FFF and 6MV eqFFF varies from 0.9404 to 1.0760 and 0.9690 to 1.0283 respectively. The Sc values for 6MV FFF and 6MV eqFFF varies from 0.9880 to 1.133 and 0.9882 to 1.0075 respectively. The Sp values for 6MV FFF and 6MV eqFFF varies from 0.9518 to 1.0619 and 0.9806 to 1.0206 respectively. From the measured values, we found that Sc, Sc,p and Sp factors of 6MV FFF less than 10 × 10cm2 field is similar to the 6MV eqFFF. For greater than 10 × 10 cm2 field size Sc, Sc,p and Sp factors higher for 6MV FFF than 6MV eqFFF. The energy matched 6MV FFF (6MV eqFFF) photon beam producing lesser Scatter radiation compare to the conventional 6MV FFF photon beams for field size more than 10 × 10 cm2.
To quantify the dosimetric accuracy of respiratory gated stereotactic body radiation therapy deli... more To quantify the dosimetric accuracy of respiratory gated stereotactic body radiation therapy delivery using dynamic thorax phantom. Three patients with mobile target (2 lung, 1liver) were chosen. Retrospective 4DCT image sets were acquired for using Varian RPM system. An in-house MATLAB program was designed for MIP, MinIP and AvgIP generation. ITV was contoured on MIP image set for lung patients and on MinIP for liver patient. Dynamic IMRT plans were generated on selected phase bin image set in Eclipse (v10.0) planning system. CIRS dynamic thorax phantom was used to perform the dosimetric quality assurance. Patient breathing pattern file from RPM system was converted to phantom compatible file by an in-house MATLAB program. This respiratory pattern fed to the CIRS dynamic thorax phantom. 4DCT image set was acquired for this phantom using patient breathing pattern. Verification plans were generated using patient gating window and delivered on the phantom. Measurements were carried out using with ion chamber and EBT2 film. Exposed films were analyzed and evaluated in FilmQA software. The stability of gated output in comparison with un-gated output was within 0.5%. The Ion chamber measured and TPS calculated dose compared for all the patients. The difference observed was 0.45%, -0.52% and -0.54 for Patient 1, Patient2 and Patient 3 respectively.Gamma value evaluated from EBT film shows pass rates from 92.41% to 99.93% for 3% dose difference and 3mm distance to agreement criteria. Dosimetric accuracy of respiratory gated SBRT delivery for lung and liver was dosimetrically acceptable. The Ion chamber measured dose was within 0.203±0.5659% of the expected dose. Gamma pass rates were within 96.63±3.84% of the expected dose.
ABSTRACT Purpose: A Comparison of out‐of‐field dose and its constituent components for 6MV Flatte... more ABSTRACT Purpose: A Comparison of out‐of‐field dose and its constituent components for 6MV Flattened and 7MV unflattened Photon BeamsMethods: The flattening filter and primary collimator are the major sources of producing the scattered radiation. The out‐of‐field photon dose, Sc,p, Sc and Sp were measured with CC 13 chamber for square open fields from 5 × 5 cm2 to 30 × 30 cm2 using IBA blue phantom and solid phantom as a function of distance from central axis and field size at depth of maximum for respective photon energies. Scatter radiation, which predominantly contributes to peripheral dose at larger distance from the field edge, was measured using a CC 13 ionization chamber. Results: All the values of Sc,p and Sc are normalized to 10 × 10 cm2 field size. The measured values of Sc,p for 6MV‐FB and 7MV‐UFB varies from 0.9437 to 1.0651 and 0.9690 to 1.0283 respectively. The Sc values for 6MV‐FB maximum (max.) 2.1 percent lesser than 7MV‐UFB for up to 10 ×10 cm2 field size and 6MV‐FB max.1.7 percent higher than the 7MV‐UFB for above 10 × 10cm2 field size. Out of field dose is max.42.0 percent higher for 6MV‐FB compare to 7MV‐UFB at 25 cm from the field edge for up to 10 × 10 cm2 field size and max.50.39 percent reduced dose for 7MV‐UFB for above 10 × 10 cm2. Out of field dose is max.70.0 percent reduced for 7MV‐UFB compare to 6MV‐FB above 50 cm away from the field edge for up to 10 × 10 cm2 field size and max.68 percent reduced dose for 7MV‐UFB for above 10 × 10 cm2. Conclusion: 7MV‐UFB may be advantageous by reduced out‐of‐field dose compare to 6MV‐FB, but differences are small in absolute terms.
ABSTRACT Purpose: Comparison of the depth dose in the build‐up region and Surface dose for 6MV fl... more ABSTRACT Purpose: Comparison of the depth dose in the build‐up region and Surface dose for 6MV flattened and 7MV unflattened photon beams with different detectorsMethods: The percentage depth dose in the build‐up region and the surface dose for the 6MV‐FB and 7MV‐UFB photon beams from a Siemens Artiste medical linear accelerator were measured for square field sizes of 5×5, 10×10 and 15×15 cm 2 using Scanditronix NACP ion chamber, CC 13, and Stereotactic field Detectors (SFD) along the central axis of the beam at 100 cm source to surface distance with IBA blue phantom 2 and solid phantom. Results: The consistency between the measured percentage depth dose data from all four detector types were observed for depths beyond the depth of the maximum dose, but were all clearly different from each other data in the build‐up region this is observed for both 6MV‐FB and 7MV‐UFB beams. The measured surface dose (16.2 Percent) applied with improved Velkley correction factors used for 10X10 cm2 of 6MV‐FB using NACP parallel plate chamber values were all in good agreement with previously published data. The measured percentage surface doses obtained using the NACP parallel plate chamber, CC 13 and SFD without any correction factor values are 0.3885,0.4330 and 0.4751, 0.4485,0.4922 and 0.5323,0.3652,0.4076 and 0.4580 respectively for field sizes of 5X5,10X10 and 15×15 cm2 for the 6MV‐FB photon beams and 0.3800,0.4117 and 0.4398, 0.4364, 0.4655 and 0.4965, 0.3611,0.4100 and 0.4349 for the 7MV‐UFB photon beams. Conclusion: The measured surface dose clearly increases with increasing field size, regardless of the detector used in the measurement for both 6MV‐FB and 7MV‐UFB photon beams. Compare to NACP parallel plate chamber CC 13 chamber is showing over response and SFD is showing lesser surface dose.
To evaluate impact on surface dose, Depth of dose maximum (dmax) and depth dose distribution due ... more To evaluate impact on surface dose, Depth of dose maximum (dmax) and depth dose distribution due to physical wedge filters for different wedge angle were studied for 6MV flattened (6MV FB) and 7MV unflattened (7MV UFB) photon beams. The flattening filter and primary collimator are the major sources of producing the scattered radiation and these parameters affect the surface dose, dmax and dose distribution. In this study, open fields surface dose, dmax and depth dose distribution values were compared with physical wedge filter for 6MV FB and 7MV UFB .The measurement carried out in Siemens - ARTISTE linear accelerator with diode detector along the central axis of the beam at 100 cm source to surface distance using IBA blue water phantom for 6MV FB and 7MV UFB x-ray beams. The surface dose increased as the field size increased for open and physical wedge fields for 6MV FB and 7MV UFB beams. For open fields, Surface doses relative to the dose at dmax ranged from 0.443 to 0.569 and 0.463 to 0.668 for field sizes of 5 × 5 to 20×20 cm2 for the 7MV UFB and 6MV FB beam respectively. The measured surface dose for 150, 300,450 and 600 wedge field values are 0.396 to 0.504, 0.366 to 0.484, 0.342 to 0.464 and 0.347 to 0.47 respectively for 7MV UFB and 0.424 to 0.566, 0.398 to 0.555, 0.3860 to 0.5430 and 0.389 to 0.55 respectively for 6MV FB. We found that dmax of wedged beams were higher than those open beams for field size up to 10 × 10 cm2 , Surface doses of wedged beams were lower than those of open beams for 7MV UFB and 6MV FB. Surface dose of the 7MV UFB were lower than the 6MV FB for open and wedged beams.
To compare the Collimator scatter factor (Sc), Phantom scatter factor (Sp) and Total scatter fact... more To compare the Collimator scatter factor (Sc), Phantom scatter factor (Sp) and Total scatter factors (Sc,p) of 6MV flattened Beam (6MV FB) and 7MV Unflattened beams (7MV UFB). The flattening filter and primary collimator are the major sources of producing the scattered radiation. In this study, the field sizes from 5×5 cm2 to 40 × 40 cm2 compared for 6MV FB and 7MV UFB. We measured Sc,p with CC 13 chamber at the depth of 10 g/cm2 using IBA blue phantom and Sc measured with CC 13 chamber at the depth of 10 g /cm2 using columnar phantom (TG 74) for 6MV FB and 7MV UFB x-ray beams from a Siemens - ARTISTE linear accelerator. The Sp values derived from the Sc,p and Sc Values. All the values of Sc,p, Sc and Sp are normalized to 10 × 10 cm2 field size the measured values of Sc,p for 6MV FB and 7MV UFB varies from 0.9437 to 1.0651 and 0.9690 to 1.0283 respectively. The Sc values for 6MV FB and 7MV UFB varies from 0.9676 to 1.0212 and 0.9882 to 1.0075 respectively. The Sp values for 6MV FB and 7MV UFB varies from 0.9752 to 1.0429 and 0.9806 to 1.0206 respectively. Our study results shows that Sc, Sp &amp; Sc,p for 7MV UFB for smaller fields up to 10 × 10 cm2 were higher than 6MV FB and for larger fields greater than 10 ×10 cm2 it is vice versa. A scatter factors are measured and compared for 6MV FB and 7MV UFB. A significant variation observed for Sc, Sp and Sc,p values of 6MV FB and 7MV UFB .This is may be due to flattening filter and beam quality.
To study the effect of the virtual wedge and physical wedge filters on the surface and build-up r... more To study the effect of the virtual wedge and physical wedge filters on the surface and build-up region doses for 6 and 15MV high-energy photon beams for different field sizes and various source to surface distance(SSD). The measurements were made in water equivalent (PMMA) solid phantom in the build-up region at various SSD for various field sizes using virtual and physical wedge filters having different angles. A parallel-plate ion chamber (Markus) was used to measure the percent depth doses at surface and buildup region. Plane parallel ion chamber with fixed plate separation on the surface and buildup region would perturbate the dose measured, to get the proper dose over response correction factor was used. The percentage depth dose at surface (PDD0) increased as the field size increased for open, virtual, and physical wedged beams. For open, 30 degree physical, and virtual wedged beams, the surface doses were found to be 15.4%, 11.2%, and 15.2% with 6-MV photons and 11.2%, 9.4%, 11.2% with 15-MV photons, respectively, at 10 × 10 cm2 field size at 100cm SSD.As SSD increases percentage depth dose at surface (PDD0) decreases for open,physical and virtual wedge field. Percentage depth dose at surface (PDD0) of virtual wedged beams were similar to those of open beams. PDD0 of physical wedged beams were lower than those of open and virtual wedged beams. Surface doses for both PW and VW increases with field size and small increase in surface dose for both PW and VW fields as wedge angle increases especially for large fields.
Purpose: Aim of this study is to determine the dosimetric influence of Filtered and Flatting Filt... more Purpose: Aim of this study is to determine the dosimetric influence of Filtered and Flatting Filter Free Photon Beam of 10 MV energy on RA planning for Ca. Cervix. Methods: CT data sets of eleven patients reported with carcinoma cervix were used for RA planning for 10MV _FFB and 10MV_FFFB. RA plans were generated using two full arcs.All RA plans were generated to deliver a dose of 50.4Gy in 28 fractions for PTV and ALARA for OAR’s. All plans were analysed for PTV Coverage, conformity Index, homogeneity index, dose to OAR’s, integral dose to normal tissue and total monitor units were studied. Results: DVH was used to evaluate RA plans for both 10MV_FFB and 10MV_FFFB photon beam. Planning results show a comparable PTV coverage for both energies. Results shows volume of PTV receiving prescription dose were 95.10+ 0.09% and 95.09 +0.11%, and volume of PTV receiving a dose of 107% is 0.45+0.96% and 5.25+8.9%, homogeneity index (HI) were 1.051+0.007 and 1.066+0.008, Conformity Index(CI) were 1.003+0.019 and 1.012+0.013, Mean Integral dose were 2.65+0.34 and 2.60+0.33(*10−5Gy.cm3) for 10MV_FFB and 10MV_FFFB respectively. 10MV_FB shows statistically significant (p<0.05) improvement in mean doses to bladder, rectum, bowel and mean total number of MU’s and also shows remarkable decrease in mean total no. of MU’s by 43.7% in comparison to 10MV_FFFB. There is statistically significant (p<0.05) difference found in CI and HI for 10MV_FB in comparison to 10MV _FFF beam. 10MV_FFFB shows statistically significant (p<0.05) for mean NTID and delivers 1.65 % less NTID in comparison to 10 MV_ FB. Conclusion: 10MV_FB is superior to 10MV_FFFB for rapid arc planning in case of Cervix carcinomas, it offers better target coverage and OAR’s sparing, comparable mean Integral dose to normal tissues and 10 MV_ FB also produced highly conformal and homogeneous dose distribution in comparison to 10MV_FFFB.
To compare the Collimator scatter factor (Sc), Phantom scatter factor (Sp) and Total scatter fact... more To compare the Collimator scatter factor (Sc), Phantom scatter factor (Sp) and Total scatter factors (Sc,p) of 6MV FFF and energy matched 6MV FFF (6MV eqFFF) METHODS: The flattening filter and primary collimator are the major sources of producing the scattered radiation. In this study, the field sizes from 5 × 5 cm2 to 40 × 40 cm2 compared for 6MV FFF and 6MV eqFFF. We measured Sc,p with CC 13 chamber at the depth of 10 g/cm2 using IBA blue water phantom and Sc measured with CC 13 chamber at the depth of 10 g /cm2 using columnar phantom (TG 74) for 6MV FFF and 6MV eqFFF x-ray beams from a Siemens - ARTISTE(6MV eqFFF ) and Varian True beam (6MV FFF) linear accelerator. The Sp values derived from the Sc,p and Sc Values. All the values of Sc,p, Sc and Sp are normalized to 10 × 10 cm2 field size. The measured values of Sc,p for 6MV FFF and 6MV eqFFF varies from 0.9404 to 1.0760 and 0.9690 to 1.0283 respectively. The Sc values for 6MV FFF and 6MV eqFFF varies from 0.9880 to 1.133 and 0.9882 to 1.0075 respectively. The Sp values for 6MV FFF and 6MV eqFFF varies from 0.9518 to 1.0619 and 0.9806 to 1.0206 respectively. From the measured values, we found that Sc, Sc,p and Sp factors of 6MV FFF less than 10 × 10cm2 field is similar to the 6MV eqFFF. For greater than 10 × 10 cm2 field size Sc, Sc,p and Sp factors higher for 6MV FFF than 6MV eqFFF. The energy matched 6MV FFF (6MV eqFFF) photon beam producing lesser Scatter radiation compare to the conventional 6MV FFF photon beams for field size more than 10 × 10 cm2.
To quantify the dosimetric accuracy of respiratory gated stereotactic body radiation therapy deli... more To quantify the dosimetric accuracy of respiratory gated stereotactic body radiation therapy delivery using dynamic thorax phantom. Three patients with mobile target (2 lung, 1liver) were chosen. Retrospective 4DCT image sets were acquired for using Varian RPM system. An in-house MATLAB program was designed for MIP, MinIP and AvgIP generation. ITV was contoured on MIP image set for lung patients and on MinIP for liver patient. Dynamic IMRT plans were generated on selected phase bin image set in Eclipse (v10.0) planning system. CIRS dynamic thorax phantom was used to perform the dosimetric quality assurance. Patient breathing pattern file from RPM system was converted to phantom compatible file by an in-house MATLAB program. This respiratory pattern fed to the CIRS dynamic thorax phantom. 4DCT image set was acquired for this phantom using patient breathing pattern. Verification plans were generated using patient gating window and delivered on the phantom. Measurements were carried out using with ion chamber and EBT2 film. Exposed films were analyzed and evaluated in FilmQA software. The stability of gated output in comparison with un-gated output was within 0.5%. The Ion chamber measured and TPS calculated dose compared for all the patients. The difference observed was 0.45%, -0.52% and -0.54 for Patient 1, Patient2 and Patient 3 respectively.Gamma value evaluated from EBT film shows pass rates from 92.41% to 99.93% for 3% dose difference and 3mm distance to agreement criteria. Dosimetric accuracy of respiratory gated SBRT delivery for lung and liver was dosimetrically acceptable. The Ion chamber measured dose was within 0.203±0.5659% of the expected dose. Gamma pass rates were within 96.63±3.84% of the expected dose.
ABSTRACT Purpose: A Comparison of out‐of‐field dose and its constituent components for 6MV Flatte... more ABSTRACT Purpose: A Comparison of out‐of‐field dose and its constituent components for 6MV Flattened and 7MV unflattened Photon BeamsMethods: The flattening filter and primary collimator are the major sources of producing the scattered radiation. The out‐of‐field photon dose, Sc,p, Sc and Sp were measured with CC 13 chamber for square open fields from 5 × 5 cm2 to 30 × 30 cm2 using IBA blue phantom and solid phantom as a function of distance from central axis and field size at depth of maximum for respective photon energies. Scatter radiation, which predominantly contributes to peripheral dose at larger distance from the field edge, was measured using a CC 13 ionization chamber. Results: All the values of Sc,p and Sc are normalized to 10 × 10 cm2 field size. The measured values of Sc,p for 6MV‐FB and 7MV‐UFB varies from 0.9437 to 1.0651 and 0.9690 to 1.0283 respectively. The Sc values for 6MV‐FB maximum (max.) 2.1 percent lesser than 7MV‐UFB for up to 10 ×10 cm2 field size and 6MV‐FB max.1.7 percent higher than the 7MV‐UFB for above 10 × 10cm2 field size. Out of field dose is max.42.0 percent higher for 6MV‐FB compare to 7MV‐UFB at 25 cm from the field edge for up to 10 × 10 cm2 field size and max.50.39 percent reduced dose for 7MV‐UFB for above 10 × 10 cm2. Out of field dose is max.70.0 percent reduced for 7MV‐UFB compare to 6MV‐FB above 50 cm away from the field edge for up to 10 × 10 cm2 field size and max.68 percent reduced dose for 7MV‐UFB for above 10 × 10 cm2. Conclusion: 7MV‐UFB may be advantageous by reduced out‐of‐field dose compare to 6MV‐FB, but differences are small in absolute terms.
ABSTRACT Purpose: Comparison of the depth dose in the build‐up region and Surface dose for 6MV fl... more ABSTRACT Purpose: Comparison of the depth dose in the build‐up region and Surface dose for 6MV flattened and 7MV unflattened photon beams with different detectorsMethods: The percentage depth dose in the build‐up region and the surface dose for the 6MV‐FB and 7MV‐UFB photon beams from a Siemens Artiste medical linear accelerator were measured for square field sizes of 5×5, 10×10 and 15×15 cm 2 using Scanditronix NACP ion chamber, CC 13, and Stereotactic field Detectors (SFD) along the central axis of the beam at 100 cm source to surface distance with IBA blue phantom 2 and solid phantom. Results: The consistency between the measured percentage depth dose data from all four detector types were observed for depths beyond the depth of the maximum dose, but were all clearly different from each other data in the build‐up region this is observed for both 6MV‐FB and 7MV‐UFB beams. The measured surface dose (16.2 Percent) applied with improved Velkley correction factors used for 10X10 cm2 of 6MV‐FB using NACP parallel plate chamber values were all in good agreement with previously published data. The measured percentage surface doses obtained using the NACP parallel plate chamber, CC 13 and SFD without any correction factor values are 0.3885,0.4330 and 0.4751, 0.4485,0.4922 and 0.5323,0.3652,0.4076 and 0.4580 respectively for field sizes of 5X5,10X10 and 15×15 cm2 for the 6MV‐FB photon beams and 0.3800,0.4117 and 0.4398, 0.4364, 0.4655 and 0.4965, 0.3611,0.4100 and 0.4349 for the 7MV‐UFB photon beams. Conclusion: The measured surface dose clearly increases with increasing field size, regardless of the detector used in the measurement for both 6MV‐FB and 7MV‐UFB photon beams. Compare to NACP parallel plate chamber CC 13 chamber is showing over response and SFD is showing lesser surface dose.
To evaluate impact on surface dose, Depth of dose maximum (dmax) and depth dose distribution due ... more To evaluate impact on surface dose, Depth of dose maximum (dmax) and depth dose distribution due to physical wedge filters for different wedge angle were studied for 6MV flattened (6MV FB) and 7MV unflattened (7MV UFB) photon beams. The flattening filter and primary collimator are the major sources of producing the scattered radiation and these parameters affect the surface dose, dmax and dose distribution. In this study, open fields surface dose, dmax and depth dose distribution values were compared with physical wedge filter for 6MV FB and 7MV UFB .The measurement carried out in Siemens - ARTISTE linear accelerator with diode detector along the central axis of the beam at 100 cm source to surface distance using IBA blue water phantom for 6MV FB and 7MV UFB x-ray beams. The surface dose increased as the field size increased for open and physical wedge fields for 6MV FB and 7MV UFB beams. For open fields, Surface doses relative to the dose at dmax ranged from 0.443 to 0.569 and 0.463 to 0.668 for field sizes of 5 × 5 to 20×20 cm2 for the 7MV UFB and 6MV FB beam respectively. The measured surface dose for 150, 300,450 and 600 wedge field values are 0.396 to 0.504, 0.366 to 0.484, 0.342 to 0.464 and 0.347 to 0.47 respectively for 7MV UFB and 0.424 to 0.566, 0.398 to 0.555, 0.3860 to 0.5430 and 0.389 to 0.55 respectively for 6MV FB. We found that dmax of wedged beams were higher than those open beams for field size up to 10 × 10 cm2 , Surface doses of wedged beams were lower than those of open beams for 7MV UFB and 6MV FB. Surface dose of the 7MV UFB were lower than the 6MV FB for open and wedged beams.
To compare the Collimator scatter factor (Sc), Phantom scatter factor (Sp) and Total scatter fact... more To compare the Collimator scatter factor (Sc), Phantom scatter factor (Sp) and Total scatter factors (Sc,p) of 6MV flattened Beam (6MV FB) and 7MV Unflattened beams (7MV UFB). The flattening filter and primary collimator are the major sources of producing the scattered radiation. In this study, the field sizes from 5×5 cm2 to 40 × 40 cm2 compared for 6MV FB and 7MV UFB. We measured Sc,p with CC 13 chamber at the depth of 10 g/cm2 using IBA blue phantom and Sc measured with CC 13 chamber at the depth of 10 g /cm2 using columnar phantom (TG 74) for 6MV FB and 7MV UFB x-ray beams from a Siemens - ARTISTE linear accelerator. The Sp values derived from the Sc,p and Sc Values. All the values of Sc,p, Sc and Sp are normalized to 10 × 10 cm2 field size the measured values of Sc,p for 6MV FB and 7MV UFB varies from 0.9437 to 1.0651 and 0.9690 to 1.0283 respectively. The Sc values for 6MV FB and 7MV UFB varies from 0.9676 to 1.0212 and 0.9882 to 1.0075 respectively. The Sp values for 6MV FB and 7MV UFB varies from 0.9752 to 1.0429 and 0.9806 to 1.0206 respectively. Our study results shows that Sc, Sp &amp; Sc,p for 7MV UFB for smaller fields up to 10 × 10 cm2 were higher than 6MV FB and for larger fields greater than 10 ×10 cm2 it is vice versa. A scatter factors are measured and compared for 6MV FB and 7MV UFB. A significant variation observed for Sc, Sp and Sc,p values of 6MV FB and 7MV UFB .This is may be due to flattening filter and beam quality.
To study the effect of the virtual wedge and physical wedge filters on the surface and build-up r... more To study the effect of the virtual wedge and physical wedge filters on the surface and build-up region doses for 6 and 15MV high-energy photon beams for different field sizes and various source to surface distance(SSD). The measurements were made in water equivalent (PMMA) solid phantom in the build-up region at various SSD for various field sizes using virtual and physical wedge filters having different angles. A parallel-plate ion chamber (Markus) was used to measure the percent depth doses at surface and buildup region. Plane parallel ion chamber with fixed plate separation on the surface and buildup region would perturbate the dose measured, to get the proper dose over response correction factor was used. The percentage depth dose at surface (PDD0) increased as the field size increased for open, virtual, and physical wedged beams. For open, 30 degree physical, and virtual wedged beams, the surface doses were found to be 15.4%, 11.2%, and 15.2% with 6-MV photons and 11.2%, 9.4%, 11.2% with 15-MV photons, respectively, at 10 × 10 cm2 field size at 100cm SSD.As SSD increases percentage depth dose at surface (PDD0) decreases for open,physical and virtual wedge field. Percentage depth dose at surface (PDD0) of virtual wedged beams were similar to those of open beams. PDD0 of physical wedged beams were lower than those of open and virtual wedged beams. Surface doses for both PW and VW increases with field size and small increase in surface dose for both PW and VW fields as wedge angle increases especially for large fields.
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