Blacktown Cancer and Haematology Center

Blacktown, Australia

Blacktown Cancer and Haematology Center

Blacktown, Australia
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Flower E.,Crown Princess Mary Cancer Center | Flower E.,University of Sydney | Do V.,Crown Princess Mary Cancer Center | Do V.,University of Sydney | And 8 more authors.
Brachytherapy | Year: 2017

Purpose: The purpose of this study was to determine the effect of deformable image registration (DIR) on cumulative organ at risk dose-volume histogram (DVH) parameter summation for more than three brachytherapy fractions. The reproducibility of different methods of DIR was tested. DIR was then used to assess the stability of the anatomic position of the DVH parameters within the bladder and rectum. Methods and Materials: DIR was completed for 39 consecutive cervical cancer brachytherapy patients' planning CTs. Accumulated DVH parameters (D 2cc and D 0.1cc) for bladder and rectum were compared with dose summation without DIR. Reproducibility of DIR results was assessed for different methods of implementation based on adding contour biases added to the DIR algorithm. Vol D2cc and Vol D0.1cc structures were created from the overlap of the D 2cc and D 0.1cc isodose and the bladder or rectum, respectively. The overlap of Vol D2cc and Vol D0.1cc structures was calculated using the Dice similarity coefficient. Results: DIR accumulated D 2cc and D 0.1cc decreased by an average of 2.9% and 4.2% for bladder and 5.08% and 2.8% for rectum compared with no DIR. DIR was most reproducible when the bladder or rectum contour was masked. The average Dice similarity coefficient was 0.78 and 0.61 for the bladder D 2cc and D 0.1cc as well as 0.83 and 0.62 for rectal D 2cc and D 0.1cc, respectively. Conclusions: Dose decreases were observed for accumulated DVH parameters using DIR. Adding contour-based biases to the algorithm increases the reproducibility of D 2cc and D 0.1cc accumulation. The anatomic position of Vol D2cc was more stable than Vol D0.1cc. © 2017.


Barber J.,Nepean Cancer Care Center | Barber J.,Blacktown Cancer and Haematology Center | Barber J.,University of Sydney | Sykes J.R.,Blacktown Cancer and Haematology Center | And 5 more authors.
Journal of Applied Clinical Medical Physics | Year: 2016

A series of phantom images using the CIRS Virtual Human Male Pelvis was acquired across available dose ranges for three image-guided radiotherapy (IGRT) imaging systems: Elekta XVI CBCT, Varian TrueBeam CBCT, and TomoTherapy MV CT. Each image was registered to a fan-beam CT within the XVI software 100 times with random initial offsets. The residual registration error was analyzed to assess the role of imaging hardware and reconstruction in the uncertainty of the IGRT process. Residual translation errors were similar for all systems and < 0.5 mm. Over the clinical dose range for prostate IGRT images (10-25 mGy), all imaging systems provided acceptable matches in > 90% of registrations when incorporating residual rotational error using a dual quaternion derived distance metric. Outside normal dose settings, large uncertainties were observed at very low and very high dose levels. No trend between initial offset and residual registration error was observed. Patient images may incur higher uncertainties than this phantom study; however, these results encourage automatic matching for standard dose settings with review by treatment staff. © Creative Commons Attribution 3.0 Unported License.

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