document: Tools for the analysis of dose optimization . I. Effect-volume histogram With the advent of dose optimization algorithms , predominantly for intensity-modulated radiotherapy -LRB- IMRT -RRB- , computer software has progressed beyond the point of being merely a tool at the hands of an expert and has become an active , independent mediator of the dosimetric conflicts between treatment goals and risks . To understand and control the internal decision finding as well as to provide means to influence it , a tool for the analysis of the dose distribution is presented which reveals the decision-making process performed by the algorithm . The internal trade-offs between partial volumes receiving high or low doses are driven by functions which attribute a weight to each volume element . The statistics of the distribution of these weights is cast into an effect-volume histogram -LRB- EVH -RRB- in analogy to dose-volume histograms . The analysis of the EVH reveals which traits of the optimum dose distribution result from the defined objectives , and which are a random consequence of under - or misspecification of treatment goals . The EVH can further assist in the process of finding suitable objectives and balancing conflicting objectives . If biologically inspired objectives are used , the EVH shows the distribution of local dose effect relative to the prescribed level
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extractive_keyphrases: dose optimization algorithms dosimetric conflicts treatment goals computer software partial volumes low doses
abstractive_keyphrases: effect-volume histogram intensity-modulated radiotherapy treatment risks decision-making process high doses volume element weights treatment planning objective function insufficient target coverage exponential law cell survival one-sided quadratic penalties quadratic overdose penalty