Show simple item record

dc.contributor.authorMcWilliam, Alan
dc.contributor.authorGraham, L
dc.contributor.authorDootson, C
dc.contributor.authorAbravan, Azadeh
dc.contributor.authorVan Herk, Marcel
dc.date.accessioned2021-07-28T12:41:37Z
dc.date.available2021-07-28T12:41:37Z
dc.date.issued2020en
dc.identifier.citationMcWilliam A, Graham L, Dootson C, Abravan A, Van Herk M. OC-0197: Dose surface maps of the heart identify dose sensitive regions. Radiotherapy and Oncology . 2020 Nov;152:S98. en
dc.identifier.urihttp://hdl.handle.net/10541/624148
dc.description.abstractPurpose or Objective It has become accepted that for lung cancer patients the radiation dose to the heart is an independent predictor of survival. Analysis of dosimetric effects on the heart have investigated volumetric dose statistics, however potential critical cardiac structures are present on the heart surface. Volumetric parameters may not be optimal due to the required inter-patient registration accuracy. In this work we present a methodology for creating cardiac surface dose maps and use these to identify cardiac surface regions where excess dose results in worse patient survival. Material and Methods 648 cardiac surface maps were successfully created with a polar coordinate system with the centre positioned at the centre of mass for the heart contour of each slice in turn. This accounted for the asymmetric nature of the heart and can be considered a modified cylindrical coordinate system. The radiotherapy dose for each patient was sampled on this surface with the described coordinate system. All hearts were normalised to the same superior-inferior dimensions for analysis. For validation of the mapping, and localisation of dosimetric effects, the cardiac chambers were manually delineated and mapped onto the surface maps for 20 patients. A point spread function (PSF) was fitted to the blurred edge of the mapped chambers to quantify uncertainty in the mapping process. To account for this uncertainty, dose maps were blurred by a 2D-Guassian function with width described by the PSF. Permutation testing was used to identify regions where excess dose resulted in worse patient survival with the Tmap calculated. A threshold was set at the 99th percentile of the T-map and the dose from the cardiac surface each patient received extracted for analysis in a multi-variable cox-proportional hazards survival model. Results All surface maps were blurred with 2D-Guassian filter of size σφ=4.3° and σy = 1.3 units. Permutation testing for patients dead and alive at 6,12,18 and 24 months showed significant differences, p<0.001. The T-map for 18 months is included as figure 1 highlighting the highest significance region at the base of the heart and extending into the right and left atria. The mean dose to the region defined by the 99th percentile across all patients was 21.6Gy compared to the mean dose to the heart of 12.7Gy. Table 1 shows the multi-variable analysis where the dose to this region on the heart surface is significantly associated with survival, hazard ratio 1.014 per Grey, p=0.03, controlling for covariates including tumour volume. Conclusion We successfully created a modified cylindrical polar coordinate system for mapping radiotherapy dose to the heart. Surface maps identified a region near the base of the heart where excess dose results in worse patient survival. This region extends over the left and right atria close to the path of the coronary arteries suggesting these sub-structures are driving this effect.en
dc.language.isoenen
dc.titleDose surface maps of the heart identify dose sensitive regionsen
dc.typeMeetings and Proceedingsen
dc.contributor.departmentUniversity of Manchester, Division of Cancer Science, Manchester,en
dc.identifier.journalRadiotherapy and Oncologyen
dc.description.noteen]


This item appears in the following Collection(s)

Show simple item record