Manual reconstruction of tumor volumes from CT scans for radiotherapy planning

Using a computed tomographic scan to construct a tumor volume on a simulation film has become an important part of radiation therapy treatment planning. Techniques for reconstruction of brain tumor volumes from computed tomographic scans onto simulation films are discussed. A technique for reconstructing by hand the tumor volume projection at a different angle from the plane of the computed tomographic scan is outlined. Ignoring beam divergence simplifies reconstruction, allowing it to be done by hand but introduces an additional error of at most 0.06, 0.15, 0.26 and 0.42 cm for tumors with maximum diameters of 5, 7.5, 10 and 12.5 cm, respectively. This technique provides the capability for limited 3-dimensional volume reconstruction of small tumors without the use of the computer.