M A N - M A C H I N E S Y S T E M F O R E F F E C T I V E R A D I A T I O N T H E R A P Y

P L A N N I N G

L. Ya. Klepper and A. P. Dolgikh UDC 615.471.03:615.849.1.015.3.07

Both manual and computerized planning and optimization of effective radiation therapy of malignant tumors are iterative procedures consisting of the following stages.

Stage 1. Determination of basic characteristics of the dose field which, according to the radiologist's opinion, should be

created to attain maximum therapeutic effect (dose distribution at the target, limitations imposed on the doses absorbed by

normal tissues and organs, relative importance of organs and tissues in terms of their possible irreversible radiation damage).

Stage 2, Setting various conditions of irradiation, including types of radiation sources, directions of irradiation, radiation

field size, etc.

Stage 3. Arranging a system of control points in tumor and in normal tissues and organs, imposing limitations on the

allowable doses at these points, and specifying relative ranking coefficients for organs, tissues, and isolated control points.

Stage 4. Solving the problem of selection of optimal conditions of irradiation and plotting respective isodose distribu-

tions.

Stage 5. Comparison of the obtained dose distribution with the dose field settings. If the dose distribution satisfies the

requirement, then the problem is solved. Otherwise, the next stage should be fulfilled.

Stage 6. Modification of the conditions of irradiation, dose limitations in control points, and relative ranking coefficients

for organs, tissues, and isolated control points. Return to stage 4. It should be emphasized that modification of the parameters

controlling the formation of the dose field is performed by a computer operator on the basis of his personal experience and

intuition.

This scheme of planning for effective radiation is typical. The present failures in formulating and solving the rigorous

problem of effective planning justifies the use of such schemes. Therefore, evaluation of the quality of dose fields should by

performed by a specialist, while the computer system for determining irradiation plans is an instrument for changing dose

distribution in the desired direction. To change the dose field, an operator should simultaneously solve two problems: to plot the

dose field using the computer system and specifying control parameters and to study functional dependence of the dose distribu-

tion on control parameters.

We have developed a computer system for radiation therapy planning. The system proved to be highly efficient for

optimal planning of radiation therapy of localized prostate cancer. Our experience shows that when developing similar systems

a friendly and advanced dialogue user interface should be installed which addresses the peculiarities of the problem. The

opportunity for routine evaluation of dose field quality should also be provided, and an information archiving system should be

created and used for selection of control parameters.

Central Institute of Mathematical Economics, Russian Academy of Sciences, Moscow. Institute of Biophysics, Russian

Ministry of Health, Moscow. Translated from Meditsinskaya Tekhnika, No. 6, p. 22, November-December, 1992.

308 0006-3398/92/2606-0308512.50 ©1993 Plenum Publishing Corporation