Limitations of a convolution method for modeling geometric uncertainties in radiation therapy. I. The effect of shift invariance

被引:75
作者
Craig, T
Battista, J
Van Dyk, J
机构
[1] Univ Western Ontario, London Reg Canc Ctr, London, ON N6A 4L6, Canada
[2] Univ Western Ontario, Dept Med Biophys, London, ON N6A 4L6, Canada
[3] Univ Western Ontario, Dept Oncol, London, ON N6A 4L6, Canada
关键词
convolution; geometric uncertainty; patient repositioning; shift invariance; radiation therapy planning;
D O I
10.1118/1.1589492
中图分类号
R8 [特种医学]; R445 [影像诊断学];
学科分类号
1002 ; 100207 ; 1009 ;
摘要
Convolution methods have been used to model the effect of geometric uncertainties on dose delivery in radiation therapy. Convolution assumes shift invariance of the dose distribution. Internal inhomogeneities and surface curvature lead to violations of this assumption. The magnitude of the error resulting from violation of shift invariance is not well documented. This issue is addressed by comparing dose distributions calculated using the Convolution method with dose distributions obtained by Direct Simulation. A comparison of conventional Static dose distributions was also made with Direct Simulation. This analysis was performed for phantom geometries and several clinical tumor sites. A modification to the Convolution method to correct for some of the inherent errors is proposed and tested using example phantoms and patients. We refer to this modified method as the Corrected Convolution. The average maximum dose error in the calculated volume (averaged over different beam arrangements in the various phantom examples) was 21% with the Static dose calculation, 9% with Convolution, and reduced to 5% with the Corrected Convolution. The average maximum dose error in the calculated volume (averaged over four clinical examples) was 9% for the Static method, 13% for Convolution, and 3% for Corrected Convolution. While Convolution can provide a superior estimate of the dose delivered when geometric uncertainties are present, the violation of shift invariance can result in substantial errors near the surface of the patient. The proposed Corrected Convolution modification reduces errors near the surface to 3% or less. (C) 2003 American Association of Physicists in Medicine.
引用
收藏
页码:2001 / 2011
页数:11
相关论文
共 36 条
[1]   Specification of dose delivery in radiation therapy - Recommendations by the Nordic Association of Clinical Physics (NACP) [J].
Aaltonen, P ;
Brahme, A ;
Lax, I ;
Levernes, S ;
Naslund, I ;
Reitan, JB ;
Turesson, I .
ACTA ONCOLOGICA, 1997, 36 :1-32
[2]  
[Anonymous], 1993, 50 ICRU
[3]  
[Anonymous], 1999, 62 ICRU
[4]   Target margins for random geometrical treatment uncertainties in conformal radiotherapy [J].
Bel, A ;
vanHerk, M ;
Lebesque, JV .
MEDICAL PHYSICS, 1996, 23 (09) :1537-1545
[5]   Modelling the dosimetric consequences of organ motion at CT imaging on radiotherapy treatment planning [J].
Booth, JT ;
Zavgorodni, SF .
PHYSICS IN MEDICINE AND BIOLOGY, 2001, 46 (05) :1369-1377
[6]   The effect of set-up uncertainties, contour changes, and tissue inhomogeneities on target dose-volume histograms [J].
Cho, BCJ ;
van Herk, M ;
Mijnheer, BJ ;
Bartelink, H .
MEDICAL PHYSICS, 2002, 29 (10) :2305-2318
[7]   Using serial imaging data to model variabilities in organ position and shape during radiotherapy [J].
Fontenla, E ;
Pelizzari, CA ;
Roeske, JC ;
Chen, GTY .
PHYSICS IN MEDICINE AND BIOLOGY, 2001, 46 (09) :2317-2336
[8]   Numerical analysis of a model of organ motion using serial imaging measurements from prostate radiotherapy [J].
Fontenla, E ;
Pelizzari, CA ;
Roeske, JC ;
Chen, GTY .
PHYSICS IN MEDICINE AND BIOLOGY, 2001, 46 (09) :2337-2358
[9]   CALCULATION OF THE UNCERTAINTY IN THE DOSE DELIVERED DURING RADIATION-THERAPY [J].
GOITEIN, M .
MEDICAL PHYSICS, 1985, 12 (05) :608-612
[10]   Setup reproducibility in radiation therapy for lung cancer: A comparison between T-bar and expanded foam immobilization devices [J].
Halperin, R ;
Roa, W ;
Field, M ;
Hanson, J ;
Murray, B .
INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS, 1999, 43 (01) :211-216