Work

Comparison of different solutions for applying patient-specific beam quality in treatment planning CT imaging

Year: 2026

Type: article

Abstract: Background: For radiotherapy treatment planning, it is necessary to convert Hounsfield units from CT images to electron density. This conversion can be performed using separate calibration curves for each beam quality. Another available solution is to use an Artificial 120 kVp reconstruction, allowing the use of a single calibration curve. The Direct Density kernel is a more modern approach that directly reconstructs electron density and requires no calibration measurements. Materials and methods: The Gammex RMI 467 phantom was measured at different positions: the central axis and an anterior offset from it. The patient-size dependence was tested by measuring the Gammex inserts in two in-house-made phantoms with variable water-equivalent diameters. Results: It was found that the standard reconstruction with separate calibration curves is the most accurate solution. The Artificial 120 kVp reconstruction introduces slightly greater uncertainty in the reconstructed electron density (ED), increasing the tube potential dependence of the reconstructed ED. The Direct Density reconstruction is less accurate; however, its performance can be improved by calibration. Conclusions: A traditional kernel with calibration curves for different energies results in more accurate electron density determination than the Artificial 120 kVp or the Direct Density reconstruction. One of the most widely used treatment planning systems has recently introduced the option to add multiple calibration curves for the same CT model.

Source: Reports of Practical Oncology & Radiotherapy

DOI: 10.5603/rpor.113351