Incorporation of functional status into dose-volume analysis

The dose-volume histogram (DVH) has gained wide acceptance as a mechanism f or reducing the voluminous data of a three-dimensional dose distribution in to a two-dimensional graph. These graphs are often converted to a single fi gure of merit. This data reduction technique is used both for clinical trea tment plan evaluation and as part of proposed systems for estimating contro l and complication probabilities. It has long been recognized that a major shortcoming of the DVH as an analysis tool is that all spatial information is discarded. A subtler problem, which is addressed in this work, is that t he DVH also implies homogeneity of biological consequence of irradiation in what may be a functionally heterogeneous volume of tissue. An extension to the DVH, the functional dose-volume histogram, or dose-function histogram (DFH), is proposed, that explicitly includes quantitative three-dimensional functional information. The concept is illustrated by the use of SPECT ima ging to assess the functional status of irradiated lung. (C) 1999 American Association of Physicists in Medicine. [S0094-2405(99)00702-6].