Retrospective reconstructions of active bone marrow dose-volume histograms.

PURPOSE

To present a method for calculating dose-volume histograms (DVH's) to the active bone marrow (ABM) of patients who had undergone radiation therapy (RT) and subsequently developed leukemia.

METHODS AND MATERIALS

The study focuses on 15 patients treated between 1961 and 1996. Whole-body RT planning computed tomographic (CT) data were not available. We therefore generated representative whole-body CTs similar to patient anatomy. In addition, we developed a method enabling us to obtain information on the density distribution of ABM all over the skeleton. Dose could then be calculated in a series of points distributed all over the skeleton in such a way that their local density reflected age-specific data for ABM distribution. Dose to particular regions and dose-volume histograms of the entire ABM were estimated for all patients.

RESULTS

Depending on patient age, the total number of dose calculation points generated ranged from 1,190,970 to 4,108,524. The average dose to ABM ranged from 0.3 to 16.4 Gy. Dose-volume histograms analysis showed that the median doses (D50%) ranged from 0.06 to 12.8 Gy. We also evaluated the inhomogeneity of individual patient ABM dose distribution according to clinical situation. It was evident that the coefficient of variation of the dose for the whole ABM ranged from 1.0 to 5.7, which means that the standard deviation could be more than 5 times higher than the mean.

CONCLUSIONS

For patients with available long-term follow-up data, our method provides reconstruction of dose-volume data comparable to detailed dose calculations, which have become standard in modern CT-based 3-dimensional RT planning. Our strategy of using dose-volume histograms offers new perspectives to retrospective epidemiological studies.