A dosimetric analysis of the Aeroform(tm) tissue expander in radiation therapy Poster No.: R-0008 Congress: 2014 CSM Type: Scientific Exhibit Authors: T. Tran, W. Ding, L. Melvern, M. Chao, B. Subramanian; EPPING/ AU Keywords: Breast, Oncology, CT, Radiation therapy / Oncology, Equipment, Experimental investigations, Radiotherapy techniques, Artifacts DOI: 10.1594/ranzcr2014/R-0008 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply RANZCR/AIR/ACPSEM's endorsement, sponsorship or recommendation of the third party, information, product or service. RANZCR/AIR/ ACPSEM is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold RANZCR/AIR/ACPSEM harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies,.ppt slideshows,.doc documents and any other multimedia files are not available in the pdf version of presentations. Page 1 of 16
Aim To evaluate the effects of the metallic reservoir and the use of gas within the Aeroform tissue expander with respect to the radiation dose distribution. Images for this section: Fig. 1: An illustration of the AirXpander system. Page 2 of 16
Methods and materials Dosimetric effects of using a metallic reservoir within a breast tissue expander during external beam radiotherapy were investigated. To view the internal components of the reservoir, it was removed from the tissue expander and imaged on a Varian AS500 electronic portal imager. To calculate the relative density of each component within the reservoir, an ionization chamber within solid water was used to measure the dose and compared to a simulation within the Pinnacle treatment planning system (TPS). To examine the relative dose profile along the length of the reservoir, the reservoir was exposed on EBT3 film and analysed using SNC Patient. In-vivo Dosimetry was performed using a RANDO Woman phantom. Thermo-luminescent dosimeters were placed within the wax bolus enveloping the tissue expander. Images for this section: Fig. 2: The metallic reservoir and the signal receiver removed from within the AirXpander breast tissue expander system. Page 3 of 16
Fig. 3: The metallic reservoir and the signal receiver on an AS500 EPID. Page 4 of 16
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Fig. 4: The Aeroform breast tissue expander system on RW3 solid water with the metallic reservoir at the beam centre. Fig. 5: An ion chamber placed in RW3 directly under the gas chamber of the metallic reservoir. Page 6 of 16
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Fig. 6: The Aeroform breast tissue expander system with wax bolus on a RANDO woman. Fig. 7: A CT image slice of the Aeroform breast tissue expander system. The treatment comprises of a pair of parallel-opposed beams. For each beam, the entrance dose at two positions and exit dose at two positions are measured. Page 8 of 16
Fig. 8: An illustration of the mean PTV defined in this experiment. Page 9 of 16
Results Imaging the reservoir on the electronic portal imager revealed it consists of 3 distinct components. The densities assigned in the TPS, which resulted in calculated doses which 3 3 matched the measured doses were; Section 1 = 0 g/cm, Section 2 = 2.8 g/cm and 3 Section 3 = 0.7 g/cm. Relative dose reductions were observed due to the metallic case; Section 1 = 20%, Section 2 = 40% and Section 3 = 30%. Entrance doses ranged from 2.39-2.53 Gy for both the medial and lateral beams. Exit doses ranging from 1.10-1.71 Gy were observed in both beams. There was a significant difference in measured and calculated doses at exit locations in the beam. Images for this section: Fig. 9: A film scan imported into SNC Patient software. Page 10 of 16
Fig. 10: A line dose profile of the metallic reservoir using Relative Dose mode. Table 1: The density assigned to the internal components of each section of the reservoir. Page 11 of 16
Table 2: Measured TLD doses compared to Pinnacle3 v9.2 dose calculations. Page 12 of 16
Conclusion Dosimetric effects due to the metallic reservoir within the Aeroform breast tissue expander have been demonstrated and have been observed to be significant. To increase the dosimetric accuracy when contouring, individual components of the reservoir should be distinguished. Our in-vivo dosimetry experiment with the RANDO demonstrated that dose homogeneity may be difficult to achieve in the surrounding tissue. In addition it may be difficult to verify the planned dose due to the scattering effects of the reservoir. The Aeroform is a novel expander that may be increasingly utilised due to its inherent simplicity and ease of use. As such we welcome its introduction but recommend stringent patient dose monitoring when utilised in patients undergoing radiotherapy. The authors would like to specially acknowledge AirXpanders for their generous donation of the Aeroform unit for this study. Images for this section: Page 13 of 16
Fig. 11: A dose distribution of the Aeroform breast tissue expander unit in this experiment. Page 14 of 16
Personal information Tai Tran Radiation Oncology Physics Registrar Radiation Oncology Victoria Epping, VIC 3076 Australia ttran@radoncvic.com.au References 1. Dean, C., U. Chetty, and A. Forrest, Effects of immediate breast reconstruction on psychosocial morbidity after mastectomy. The Lancet, 1983. 321(8322): p. 459-462. 2. Wilkins, E.G., et al., Prospective analysis of psychosocial outcomes in breast reconstruction: one-year postoperative results from the Michigan Breast Reconstruction Outcome Study. Plastic and reconstructive surgery, 2000. 106(5): p. 1014-1025. 3. Motwani, S.B., et al., The impact of immediate breast reconstruction on the technical delivery of postmastectomy radiotherapy. International Journal of Radiation Oncology* Biology* Physics, 2006. 66(1): p. 76-82. 4. Ascherman, J.A., et al., Implant reconstruction in breast cancer patients treated with radiation therapy. Plastic and reconstructive surgery, 2006. 117(2): p. 359-365. 5. Krueger, E.A., et al., Complications and patient satisfaction following expander/implant breast reconstruction with and without radiotherapy. International Journal of Radiation Oncology* Biology* Physics, 2001. 49(3): p. 713-721. 6. Ebctcg, E.B.C.T.C., Effect of radiotherapy after mastectomy and axillary surgery on 10year recurrence and 20-year breast cancer mortality: meta-analysis of individual patient data for 8135 women in 22 randomised trials. Lancet, 2014. Page 15 of 16
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