Purpose Apex TM is detachable, add-on micro multileaf collimator mounted on Elekta Synergy triple Energy linear accelerator. Apex TM has 56 leaf pairs with leaf thickness of 2.46mm at isocenter and maximum field size of 12x14 cm 2 . Apex TM has been commissioned for stereotactic radiosurgery and stereotactic radiotherapy for conformal RT and dynamic conformal arc therapy mode. Measurements were made to characterize the basic dosimetric properties of Apex TM such as leaf transmission, MLC leakage, beam penumbra and Total scatter factor. In addition geometric and dosimetric accuracy of Apex TM was verified. Leaf transmission, leakage and beam penumbra were measured using calibrated films in acrylic slab phantom. Total Scatter factor (TSF) was measured in water phantom by PTW dosimetry diode SRS & pinpoint chamber and in acrylic slab phantom by Gafchromic EBT3 films. Total scatter factor (TSF) for 6MV and 4MV compared with Monte Carlo Beam model of Apex TM for 6MV and 4MV. Purpose Dosimetric Characteristics Of Dynamic Micro Multileaf Collimator P. Shinde, L.N. Chaudhari, M. Meshram,V. Shankar, P. Deshmukh M S Patel Cancer Centre, Karamsad, Gujarat, India. Result Fig-1. Elekta Synergy with Apex micro multileaf collimator, Leaf Bank top view(right corner top), Leaf Bank Bottom View (right corner botttom) Materials/Methods Between opposing leaves abutting along central beam axis, transmission was 0.813±0.02%, 0.583±0.01% and 0.500±0.01% for 15MV, 6MV and 4MV respectively. Mean 80% to 20% penumbra width Parallel (Perpendicular) to leaf motion was 2.79 ±0.11 (2.55±0.12) mm and 3.01±0.112 (2.74±0.113) mm for 6MV and 4MV respectively over a range of field size of 0.5 cm 2 to 12 cm 2 Total scatter factor (TSF) measured with diode detector was well within ±2% of Monte Carlo calculated Total Scatter Factor for 6MV and 4MV Energies. Leaf position reproducibility and geometric accuracy was within 1mm. Apex TM micro multi leaf collimator is stable, high precision field shaping device, suitable for stereotactic radio surgery application with minimal intra leaf transmission, inter leaf leakage and small beam penumbra across the field. Fig-2. Transmission Profile of 15 MV. Result Conclusion 1.Boyer AL, Ochran TG, Nyerick CE, Waldron TJ, Huntzinger CJ. Clinical dosimetry for implementation of a multileaf collimator. Med Phys. 1992;19(5):1255–61. 2. Xia P, Geis P, Xing L, et al. Physical characteristics of a miniature multileaf collimator. Med Phys. 1999;26(1):65–70. 3. Yin FF, Zhu J, Yan H, et al. Dosimetric characteristics of Novalis shaped beam surgery unit. Med Phys. 2002;29(8):1729–38. 4. Galal MM, Keogh S, Khalil S., Dosimetric and mechanical characteristics of a commercial dynamic microMLC used in SRS. Med Phys. 2011 Jul;38(7):4225-31. 5. D.S. Sharma et al, Physical and dosimetric characteristic of high-definition multileaf collimator (HDMLC) for SRS and IMRT, Journal of Applied Clinical Medical Physics, Vol. 12, No. 3, Summer 2011 6. Borges et al.: MC modeling, simulations and validation of the HD120MLC, Med. Phys. 39 (1), January 2012 7. Bayouth JE, Morrill SM, MLC dosimetric characteristics for small field and IMRT applications. Med Phys. 2003 Sep;30(9):2545-52. 8. Basran et al.: Dosimetric verification of MMLC IMRT Journal of Applied Clinical Medical Physics, Vol. 9, No. 3, Summer 2008 9. Arthur Boyer et al.: BASIC APPLICATIONS OF MULTILEAF COLLIMATORS, AAPM REPORT NO. 72 Med Phys. 2001 Jul 10. Apex TM Customer Acceptance Test ELEKTA LIMITED Linac House Fleming Way, Crawley References Mean Intra Leaf Transmission Energy 4MV 6MV 15MV % Transmission 0.23±0.015 % 0.33±0.01 % 0.47±0.02 % Mean Inter Leaf Leakage Energy 4MV 6MV 15MV % Leakage 0.232±0.003 % 0.337±0.001 % 0.476±0.01 %

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Page 1: Dosimetric Characteristics Of Dynamic Micro Multileaf ...astro2013.abstractsnet.com/handouts/pdfs/011503.pdfDosimetric Characteristics Of Dynamic Micro Multileaf Collimator P. Shinde,

Purpose ApexTM is detachable add-on micro multileaf collimator mounted on Elekta Synergy triple Energy linear accelerator ApexTM has 56 leaf pairs with leaf thickness of 246mm at isocenter and maximum field size of 12x14 cm2 ApexTM has been commissioned for stereotactic radiosurgery and stereotactic radiotherapy for conformal RT and dynamic conformal arc therapy mode Measurements were made to characterize the basic dosimetric properties of ApexTM such as leaf transmission MLC leakage beam penumbra and Total scatter factor In addition geometric and dosimetric accuracy of ApexTM was verified

Leaf transmission leakage and beam penumbra were measured using calibrated films in acrylic slab phantom Total Scatter factor (TSF) was measured in water phantom by PTW dosimetry diode SRS amp pinpoint chamber and in acrylic slab phantom by Gafchromic EBT3 films Total scatter factor (TSF) for 6MV and 4MV compared with Monte Carlo Beam model of ApexTM for 6MV and 4MV

Purpose

Dosimetric Characteristics Of Dynamic Micro Multileaf Collimator P Shinde LN Chaudhari M MeshramV Shankar P Deshmukh

M S Patel Cancer Centre Karamsad Gujarat India

Result

Fig-1 Elekta Synergy with Apex micro multileaf collimator Leaf Bank top view(right corner top) Leaf Bank Bottom View (right corner botttom)

MaterialsMethods

Between opposing leaves abutting along central beam axis transmission was 0813plusmn002 0583plusmn001 and 0500plusmn001 for 15MV 6MV and 4MV respectively

Mean 80 to 20 penumbra width Parallel (Perpendicular) to leaf motion was 279 plusmn011 (255plusmn012) mm and 301plusmn0112 (274plusmn0113) mm for 6MV and 4MV respectively over a range of field size of 05 cm2 to 12 cm2

Total scatter factor (TSF) measured with diode detector was well within plusmn2 of Monte Carlo calculated Total Scatter Factor for 6MV and 4MV Energies Leaf position reproducibility and geometric accuracy was within 1mm

ApexTM micro multi leaf collimator is stable high precision field shaping device suitable for stereotactic radio surgery application with minimal intra leaf transmission inter leaf leakage and small beam penumbra across the field

Fig-2 Transmission Profile of 15 MV

Result

Conclusion

1Boyer AL Ochran TG Nyerick CE Waldron TJ Huntzinger CJ Clinical dosimetry for implementation of a multileaf collimator Med Phys 199219(5)1255ndash61 2 Xia P Geis P Xing L et al Physical characteristics of a miniature multileaf collimator Med Phys 199926(1)65ndash70 3 Yin FF Zhu J Yan H et al Dosimetric characteristics of Novalis shaped beam surgery unit Med Phys 200229(8)1729ndash38 4 Galal MM Keogh S Khalil S Dosimetric and mechanical characteristics of a commercial dynamic microMLC used in SRS Med Phys 2011 Jul38(7)4225-31 5 DS Sharma et al Physical and dosimetric characteristic of high-definition multileaf collimator (HDMLC) for SRS and IMRT Journal of Applied Clinical Medical Physics Vol 12 No 3 Summer 2011 6 Borges et al MC modeling simulations and validation of the HD120MLC Med Phys 39 (1) January 2012 7 Bayouth JE Morrill SM MLC dosimetric characteristics for small field and IMRT applications Med Phys 2003 Sep30(9)2545-52 8 Basran et al Dosimetric verification of MMLC IMRT Journal of Applied Clinical Medical Physics Vol 9 No 3 Summer 2008 9 Arthur Boyer et al BASIC APPLICATIONS OF MULTILEAF COLLIMATORS AAPM REPORT NO 72 Med Phys 2001 Jul 10 ApexTM Customer Acceptance Test ELEKTA LIMITED Linac House Fleming Way Crawley

References Mean Intra Leaf Transmission

Energy 4MV 6MV 15MV

Transmission 023plusmn0015 033plusmn001 047plusmn002

Mean Inter Leaf Leakage

Energy 4MV 6MV 15MV

Leakage 0232plusmn0003 0337plusmn0001 0476plusmn001