Tara Rosewall1,2,3, Andrew Bayley1,2, Charles Catton1,2, Peter Chung1,2, Geoffrey Currie3,4, Robert Heaton1,2, Janelle Wheat3,4, Michael Milosevic1,2. 1. 1 Radiation Medicine Program, Princess Margaret Cancer Centre, Toronto, ON, Canada. 2. 2 Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada. 3. 3 Faculty of Science, Charles Sturt University, NSW, Australia. 4. 4 Australian School of Advanced Medicine, Macquarie University, NSW, Australia.
Abstract
OBJECTIVE: To evaluate the methods to delineate the inner bladder (IB) surface using a uniform contraction from the outer bladder (OB) surface, assuming the bladder wall (BW) is either of constant thickness, constant volume or variable volume. METHODS: 14 prostate intensity-modulated radiotherapy patients with 2 planning CTs were identified. For both CTs, OB was delineated using model-based segmentation. IB was delineated manually. Then, using uniform contractions from OB, the position of IB was approximated using a: 2.5-mm contraction, patient-specific contraction, patient-specific constant wall volume method and variable wall volume method. The structures created using those strategies were compared against the manual IB contours using geometric and dosimetric indices. RESULTS: In the presence of variable bladder filling, use of a generic or patient-specific constant contraction resulted in a significant overestimation of IB volume (+12 and +13 cm(3), respectively; p < 0.001) that was inversely correlated with the difference in urine volume between the scans (R(2) > 0.86). Mean differences across 95% of IB surfaces were ≤2 mm for methods using either constant or variable wall volume. Mean dose-volume histogram (DVH) differences were <1 cm(3) across the whole BW DVH when using the method that assumed a variable wall volume. CONCLUSION: The variable volume BW model provided the best approximation of the IB surface position under varying filling conditions, based on geometric and dosimetric indices. ADVANCES IN KNOWLEDGE: Use of the equation derived in this research provides a quick and accurate method to delineate the hollow BW on serial imaging for the purposes of dose reconstruction.
OBJECTIVE: To evaluate the methods to delineate the inner bladder (IB) surface using a uniform contraction from the outer bladder (OB) surface, assuming the bladder wall (BW) is either of constant thickness, constant volume or variable volume. METHODS: 14 prostate intensity-modulated radiotherapy patients with 2 planning CTs were identified. For both CTs, OB was delineated using model-based segmentation. IB was delineated manually. Then, using uniform contractions from OB, the position of IB was approximated using a: 2.5-mm contraction, patient-specific contraction, patient-specific constant wall volume method and variable wall volume method. The structures created using those strategies were compared against the manual IB contours using geometric and dosimetric indices. RESULTS: In the presence of variable bladder filling, use of a generic or patient-specific constant contraction resulted in a significant overestimation of IB volume (+12 and +13 cm(3), respectively; p < 0.001) that was inversely correlated with the difference in urine volume between the scans (R(2) > 0.86). Mean differences across 95% of IB surfaces were ≤2 mm for methods using either constant or variable wall volume. Mean dose-volume histogram (DVH) differences were <1 cm(3) across the whole BW DVH when using the method that assumed a variable wall volume. CONCLUSION: The variable volume BW model provided the best approximation of the IB surface position under varying filling conditions, based on geometric and dosimetric indices. ADVANCES IN KNOWLEDGE: Use of the equation derived in this research provides a quick and accurate method to delineate the hollow BW on serial imaging for the purposes of dose reconstruction.
Authors: G J Meijer; M van den Brink; M S Hoogeman; J Meinders; J V Lebesque Journal: Int J Radiat Oncol Biol Phys Date: 1999-11-01 Impact factor: 7.038
Authors: Tara Rosewall; Andrew J Bayley; Peter Chung; Lisa W Le; Jason Xie; Siddhartha Baxi; Charles N Catton; Geoffrey Currie; Janelle Wheat; Michael Milosevic Journal: Radiother Oncol Date: 2011-08-22 Impact factor: 6.280
Authors: M Rex Cheung; Susan L Tucker; Lei Dong; Renaud de Crevoisier; Andrew K Lee; Steven Frank; Rajat J Kudchadker; Howard Thames; Radhe Mohan; Deborah Kuban Journal: Int J Radiat Oncol Biol Phys Date: 2007-01-22 Impact factor: 7.038
Authors: J M Michalski; J A Purdy; K Winter; M Roach; S Vijayakumar; H M Sandler; A M Markoe; M A Ritter; K J Russell; S Sailer; W B Harms; C A Perez; R B Wilder; G E Hanks; J D Cox Journal: Int J Radiat Oncol Biol Phys Date: 2000-01-15 Impact factor: 7.038
Authors: Awad A Ahmed; Brian Egleston; Pino Alcantara; Linna Li; Alan Pollack; Eric M Horwitz; Mark K Buyyounouski Journal: Int J Radiat Oncol Biol Phys Date: 2013-05-09 Impact factor: 7.038