EXTENSION OF THE NET FRACTIONAL DEPTH DOSE FOR INHOMOGENEITY CORRECTION

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The correction for the effect of inhomogeneity in body tissues is of considerable importance in the treatment optimization especially, of lesions in the thoracal region, such as the tumors of the breast, the esophagus, or the lung. The advent of CT has made this meaningful. The recently described NFD has been extended by the incorporation of the density scaling concept in the field size as well as the depth parameter, in the analytical for malism, thus including correction for inhomogeneities. This method now includes correction for the effect of secondary electron transport for a significant set of conditions. Further work needs to be done to incorporate the electron transport correction near the beam edges and for small inhomogeneities in larger fields. The method appears to be accurate, versatile and easy to implement.