ICRU Report 42, Use of Computers in External Beam Radiotherapy Procedures with High Energy Photons and Electrons


This Report continues the series of reports issued by the Commission dealing with dosimetric problems in external beam therapy with high energy photons. The previous reports covered such matters as the measurement of absorbed dose in a water phantom, determination of absorbed dose in the patient and specification of target absorbed dose for reporting purposes. Since the publication of those ICRU reports, computers have assumed an increasingly important role in dosimetric and treatment planning procedures in many radiation therapy centers.

The new Report covers treatment planning and recording and documentation procedures using computers in external beam therapy. Because of the rapid evolution of computer technology, only the main concepts and basic methods are presented with some specific examples included for illustrative purposes. To produce the dose distribution throughout the target volume and relevant normal tissues that is needed for treatment planning purposes, it is necessary to combine beam data and patient data. As a result, the Report treats the acquisition of beam data for both photons and electrons. In each case, the Report also provides, in the appendices, some of the mathematical expressions that have been used with computers to provide numerical values for such data. The Report then treats patient data, including information on the external surface of the patient, the target volume, the organs at risk and relevant tissue inhomogeneity. Methods for acquisition and presentation of this material are considered. The report next treats computation of the absorbed dose distribution in the patient, covering modification of photon and electron beams by the patient and beam combination. Practical aspects of treatment planning by computer are also covered, including such topics as the building of a beam library, the input of patient data and treatment parameters, visualization of a treatment plan and optimization. Since the use of computers can lead to situations where more information may be gathered than can be conveniently used, the report also provides guidelines on choosing relevant information and discusses the appropriate presentation. The recording, monitoring, automatic set up, and documentation of treatment are also covered in the report. Recommendations are provided on quality assurance of the computer system.