[Conventional roentgenologic methods and computerized tomography in the preirradiation planning for patients with...

During the planning of irradiation of patients with esophageal cancer significant divergence is frequently noted between topometric maps obtained by conventional x-ray methods including axial tomography, and computerized tomography. Topometric maps based on these two methods were compared. Using a typical example of a series of 12 patients, divergences in expected dose loads on critical points were analysed on the basis of 3 variants of superposed topometric maps. Divergences in topometric maps result from errors in topometric methods and from an impossibility to reproduce precisely the level of a section and physiological conditions during repeated layings of a patient. Divergences in a focal dose (on the esophagus) can reach 8% in rotation radiotherapy, 20% in static irradiation, and on the vertebral canal 28 and 13% respectively. Factors that influence such divergences are discussed.