[Topographic and dosimetric considerations in different methods of proton irradiation]

Two techniques are employed for proton irradiation: one--to pass a proton beam through a target, the other one--to stop in it. The advantage of the first technique is a very small angular divergence of the beam penetrating tissues or, consequently, a very high lateral edge field gradient. The second technique has two additional advantages: the absence of radiation lesions behind the target and an increase in the stopping power (dose) at the end of the beam range localized in the target. The authors present their considerations concerning the applicability of each technique and certain characteristic problems of the second technique. Dose field deformations as a result of topometric uncertainties are also estimated. A method of dose design aimed at minimizing the above mentioned effect is proposed.