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Treatment preparation QA

Introduction

Patient data acquisition is an important part of the RT process, since reliable data are required for treatment planning purposes and allow for a treatment plan to be properly carried out. Patient data acquisition includes identification of the target volumes and OARs, determination of patient treatment position, determination and verification of treatment field geometry, and the generation of radiographs or DRRs for each treatment beam for comparison with portal images. For this purpose dedicated equipment for radiotherapy simulation has been developed. Conventional simulation systems are based on treatment unit geometry in conjunction with diagnostic radiography and fluoroscopy systems. Modern CT simulation systems are based on CT images using special software, often available in a 3D treatment planning system.

Important Principles

Patient data requirements for treatment planning include outlining the external shape of the patient for all areas where the beams enter and exit, and in adjacent areas. Targets and internal structures must be outlined in order to determine their shape and volume for dose calculation. Electron densities for each volume element in the dose calculation matrix must be determined if a correction for heterogeneities is to be applied. Transverse CT scans contain all information required for complex treatment planning and form the basis of CT-simulation in modern radiotherapy treatment. Immobilization devices serve not only to immobilize the patient during treatment, but also provide a reliable means of reproducing the patient position from treatment planning and simulation to treatment, and from one treatment to another.

Introduction to References

A general discussion of the various aspects of treatment preparation including patient data acquisition, simulation and immobilization is presented in Chapter 7 of the IAEA Radiation Oncology Physics Handbook.