Quality assurance in total body irradiation

Abstract

The central aspect of all quality assurance programs in radiotherapy is to guarantee the prescribed dose and dose distribution in every treated patient. This should assure as much as possible benefit from the intended treatment and should also facilitate the comparison of treatment results of multicentrical studies. It is the topic of this paper to summarize the special aspects of quality assurance in total body irradiation prior to bone marrow transplantation.

In general radiotherapy is an interdisciplinary task and especially this is true for total body irradiation. Many factors influence the clinical outcome of this combined treatment modality and their interaction is by far not well understood.

Quality assurance in total body irradiation covers all steps of this complex treatment regiment including clinical diagnosis, formulation of the therapeutical concept, clinical and physical treatment planning, desimetry, and treatment verification. A clear dose prescription is a prerequisite for all tollowing steps in total body irradiation. This is not selt-evident and contrasts with more conventional radiation therapy treatment situations because of the complex target volume.

Localization/simulation as the essential part of clinical treatment planning consists mainly in delineating the lung areas to be shielded in order to protect the most critical organ at risk. The requirements on dosimetry and physical treatment planning are outlined including the possibilities and limitations of commercially available therapy planning systems for total body irradiation. Treatment veritication procedures comprise the control of the different treatment parameters like patient position, alignment of shielding blocks and compensators or boli and machine settings. This is similiar to the situation in conventional radiotherapy. Besides this the distinctive importance of in vivo dosimetry for quality assurance in total body irradiation will be outlined.