{"id":{"repo_id":"buffalo","oai_identifier":"oai:ubir.buffalo.edu:10477/86754"},"canonical_url":"https://search.dev.ndltd.org/etd/buffalo/oai:ubir.buffalo.edu:10477/86754","repository":{"repo_id":"buffalo","name":"Buffalo","base_url":"https://ubir.buffalo.edu/oai/request"},"display":{"title":"Investigation of the Dosimetric Impact of Patient Immobilization Device and Treatment Couch Structures in Prone Breast Radiation Therapy","abstract":"Ph.D.","abstract_html":"Ph.D.","abstract_has_math":false,"creators":["Lau, Amy"],"institution":"State University of New York at Buffalo","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Wang, Zhou (Iris)","Radiology"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2025,"date_issued":"2025-02-21T21:44:45Z","date_published":"2025-02-21T21:44:45Z","updated_at":"2026-07-27T19:05:37Z","subjects":["nuclear physics and radiation"],"languages":["eng"],"rights":["Users of works found in University at Buffalo Institutional Repository (UBIR) are responsible for identifying and contacting the copyright owner for permission to reuse. University at Buffalo Libraries do not manage rights for copyright-protected works and cannot assist with permissions.","Copyright retained by author."],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/10477/86754","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Wang, Zhou (Iris)","Radiology"]},{"key":"dc:creator","label":"Author","values":["Lau, Amy"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2025-02-21T21:44:45Z","2020"]},{"key":"dc:publisher","label":"Institution","values":["State University of New York at Buffalo"]},{"key":"dc:type","label":"Dc Type","values":["Text","Dissertation"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["nuclear physics and radiation"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Users of works found in University at Buffalo Institutional Repository (UBIR) are responsible for identifying and contacting the copyright owner for permission to reuse. University at Buffalo Libraries do not manage rights for copyright-protected works and cannot assist with permissions.","Copyright retained by author."]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/10477/86754"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Ph.D.","Purpose: In prone breast radiation, as the medial tangential beam usually passes through the immobilization board and couch, it is necessary to quantify the attenuation effect and the potential skin dose enhancement from these external structures when not included during the treatment planning process. Methods: The prone breast board studied consists of an insert on which the contralateral breast rests and a board base indexed to the couch. Two different Varian couch systems were also studied. The three effects being quantified were attenuation, scatter and bolus effect. Transmission factors (TF) of the board were measured using a Farmer chamber at 4 cm depth. Couch TFs were measured using a thimble chamber centered in a cylindrical phantom. TFs were then computed in the treatment planning system (TPS) for comparison. Selected clinical plans were recomputed in the TPS incorporating external structures for target coverage evaluation. Skin dose effects were measured using a Markus parallel plate chamber with a 1 mm buildup cap. A custom support model was created in the TPS for clinical implementation. The correction for the attenuation effect incorporating the custom support and couch structures in the treatment plans was also demonstrated. Monte Carlo (MC) simulations were carried out on phantom studies to further investigate the scatter and bolus effects from the breast board. Finally, the work flow of incorporating external structures in MC simulation for clinical prone breast cases were presented where an example of a patient case utilizing this workflow was carried out for a TPS-MC comparison. Results: Measured board insert / base TFs ranged 0.976-0.983 / 0.979-0.985 for 6MV and ranged 0.990-0.999 / 0.989-0.998 for 23MV x-rays, respectively, where TPS values agreed within 0.6%. Varian Exact Couch and Exact IGRT Couch TFs ranged 0.836-1 and 0.956-0.996, respectively, for 6 MV. The clinical treatment volume and whole breast receiving 95% of the prescription dose (CTV-V95 and WB-V95) of selected patients demonstrated reduced coverage due to attenuation of external structures. Close proximity to the base increased skin dose by up to 25-30%. Contacting the insert increased skin dose by 65-93% for 6MV and 117-157% for 23MV, respectively. For the custom support model of the breast board, assigned Hounsfield units (HUs) providing the best agreement was 200 and -100/-900 for the insert and board base respectively. Measured and MC values were compared for scatter effect with varying assigned densities (i.e. 0.25 g/cm3, 0.3 g/cm3, \"sandwich structure\") where the \"sandwich structure\" showed the best agreement. A dose enhancement was also seen in the MC simulation of the bolus effect from the insert. The MC dose calculation of an example clinical case showed a hot spot in an area near the board insert. Conclusion: Results have shown reduced coverage by attenuating external structures. Proper modeling of immobilization devices and couch structures in the TPS should be implemented for accurate dose calculation. Modelling a custom support structure in the TPS to match the measured attenuation results within a minimal margin of error is feasible. Increased surface doses were observed caused by direct contact to the insert or close proximity to the base. Further MC investigation with a sample of prone breast patients can potentially provide additional skin dose information for clinical decision.","**To request an accessible version of the file(s) associated with this item, contact library@buffalo.edu. Please include the item's persistent URL [http://hdl.handle.net/. . .] in your request.**"]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Investigation of the Dosimetric Impact of Patient Immobilization Device and Treatment Couch Structures in Prone Breast Radiation Therapy"]}]}],"canonical_facts":{"dc:contributor":["Wang, Zhou (Iris)","Radiology"],"dc:creator":["Lau, Amy"],"dc:date":["2025-02-21T21:44:45Z","2020"],"dc:description":["Ph.D.","Purpose: In prone breast radiation, as the medial tangential beam usually passes through the immobilization board and couch, it is necessary to quantify the attenuation effect and the potential skin dose enhancement from these external structures when not included during the treatment planning process. Methods: The prone breast board studied consists of an insert on which the contralateral breast rests and a board base indexed to the couch. Two different Varian couch systems were also studied. The three effects being quantified were attenuation, scatter and bolus effect. Transmission factors (TF) of the board were measured using a Farmer chamber at 4 cm depth. Couch TFs were measured using a thimble chamber centered in a cylindrical phantom. TFs were then computed in the treatment planning system (TPS) for comparison. Selected clinical plans were recomputed in the TPS incorporating external structures for target coverage evaluation. Skin dose effects were measured using a Markus parallel plate chamber with a 1 mm buildup cap. A custom support model was created in the TPS for clinical implementation. The correction for the attenuation effect incorporating the custom support and couch structures in the treatment plans was also demonstrated. Monte Carlo (MC) simulations were carried out on phantom studies to further investigate the scatter and bolus effects from the breast board. Finally, the work flow of incorporating external structures in MC simulation for clinical prone breast cases were presented where an example of a patient case utilizing this workflow was carried out for a TPS-MC comparison. Results: Measured board insert / base TFs ranged 0.976-0.983 / 0.979-0.985 for 6MV and ranged 0.990-0.999 / 0.989-0.998 for 23MV x-rays, respectively, where TPS values agreed within 0.6%. Varian Exact Couch and Exact IGRT Couch TFs ranged 0.836-1 and 0.956-0.996, respectively, for 6 MV. The clinical treatment volume and whole breast receiving 95% of the prescription dose (CTV-V95 and WB-V95) of selected patients demonstrated reduced coverage due to attenuation of external structures. Close proximity to the base increased skin dose by up to 25-30%. Contacting the insert increased skin dose by 65-93% for 6MV and 117-157% for 23MV, respectively. For the custom support model of the breast board, assigned Hounsfield units (HUs) providing the best agreement was 200 and -100/-900 for the insert and board base respectively. Measured and MC values were compared for scatter effect with varying assigned densities (i.e. 0.25 g/cm3, 0.3 g/cm3, \"sandwich structure\") where the \"sandwich structure\" showed the best agreement. A dose enhancement was also seen in the MC simulation of the bolus effect from the insert. The MC dose calculation of an example clinical case showed a hot spot in an area near the board insert. Conclusion: Results have shown reduced coverage by attenuating external structures. Proper modeling of immobilization devices and couch structures in the TPS should be implemented for accurate dose calculation. Modelling a custom support structure in the TPS to match the measured attenuation results within a minimal margin of error is feasible. Increased surface doses were observed caused by direct contact to the insert or close proximity to the base. Further MC investigation with a sample of prone breast patients can potentially provide additional skin dose information for clinical decision.","**To request an accessible version of the file(s) associated with this item, contact library@buffalo.edu. Please include the item's persistent URL [http://hdl.handle.net/. . .] in your request.**"],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/10477/86754"],"dc:language":["eng"],"dc:publisher":["State University of New York at Buffalo"],"dc:rights":["Users of works found in University at Buffalo Institutional Repository (UBIR) are responsible for identifying and contacting the copyright owner for permission to reuse. University at Buffalo Libraries do not manage rights for copyright-protected works and cannot assist with permissions.","Copyright retained by author."],"dc:subject":["nuclear physics and radiation"],"dc:title":["Investigation of the Dosimetric Impact of Patient Immobilization Device and Treatment Couch Structures in Prone Breast Radiation Therapy"],"dc:type":["Text","Dissertation"]},"updated_at":"2026-07-27T19:05:37Z"}