The influence of different kVs and phantoms on computed tomography number to relative electron density calibration curve for radiotherapy dose calculation

Abstract

Abstract Objective This study was carried out to analyze the effect of varying kilovoltage peak (kVp) on Hounsfield unit (HU) for various tissue substitutes in two different phantoms and their dosimetric impact on dose calculation in Monaco treatment planning system version 5.11.02. Methods HU for different density materials was obtained from computed tomography images of the phantoms acquired at various kVps (80, 100, and 120). Two different phantoms (CatPhan 503 and CIRS 062 M) were used to construct their suitability for computed tomography. Both scan phantoms were used to perform 30 volumetric modulated arc therapy plans. Results No significant variation in the CatPhan phantom was observed for HU of different density materials with various kVp. In contrast, a direct relationship between kVp and HU was observed in the case of CIRS phantom, as increases in the kVp resulted in a corresponding decrease in HU. The maximum HU deviation was found in breast tissue. HU is inversely proportional to the kVp for tissues. There was a difference of ≥22% in HU values between the highest densities in CatPhan and CIRS phantoms. Conclusion CIRS 062 M was found more convenient for calibration than CatPhan 503, especially for high‐density material.

Keywords

• computed tomography
• electron density calibration curve
• Hounsfield unit
• phantoms
• volumetric modulated arc therapy