BACKGROUND AND PURPOSE: The methodology developed by IAEA for dosimetric quality control of treatment planning systems has been tested in different hospitals through a pilot study. The aim was to verify the methodology and observe the range of deviations between planned and delivered doses in 3D conformal radiotherapy in situations close to a clinical setting. MATERIAL AND METHODS: The methodology was based on an anthropomorphic phantom representing the human thorax, and simulates the whole chain of external beam radiotherapy treatment planning activities. The phantom was scanned using computed tomography and eight test cases were planned on treatment planning systems which imitate different irradiation geometries found in conformal radiotherapy. The doses were measured with ion chambers, and the deviation between measured and treatment planning system calculated doses was reported. This methodology, which employs the same phantom and the same set of test cases, was tested in 17 different hospitals which were using 14 different algorithms/inhomogeneity correction methods implemented in different treatment planning systems. RESULTS: A total of 53 clinical test case datasets for different energies and calculation algorithms were produced. Most of the systems with advanced algorithms complied with predefined agreement criteria. Dose differences more than 20% were discovered for some of the simple algorithms and high energy X-ray beams. The number of deviations outside agreement criteria increases with the beam energy and decreases with advancement of the treatment planning system calculation algorithm. CONCLUSIONS: Large deviations exist in some simple dose calculation algorithms, therefore more advanced algorithms would be preferable and therefore should be implemented in clinical practice. The test cases that could be performed in reasonable time would help the users to appreciate the possibilities of their system and understand its limitations.
