The effect of electron density instabilities on dose calculation

Treatment plans are based on an anatomical dataset of the tumor acquired during the preparation stage using a kVCT (kilovolt computed tomography) scanner. Anatomical reference changes will occur during the treatment course, in some cases requiring a new treatment plan to deliver the prescribed dose. With the introduction of 3D volumetric on-board imaging devices, it became feasible to use the produced images for dose recalculation. However, the use of these on-board imaging devices in clinical routine for the calculation of dose depends on the stability of the images. In this study the validation of tomotherapy MVCT (megavolt computed tomography) produced images, for the purpose of dose recalculation by the Planned Adaptive software, has been performed. To determine the validity of MVCT images for dose calculation, a treatment plan was created based on kVCT-acquired images of a solid water phantom. During a period of 5 months, MVCT images of the phantom have been acquired and were used by the planned adaptive software to recalculate the initial kVCT-based dose on the MVCT images. The impact of the adjusted IVDTs (image value to density table) has been explored just as the impact of picture procurement with or without going before airscan. Yield changes or potentially insecurities of the imaging bar result in MV images of various quality yielding diverse outcomes when utilized for portion estimation. It was demonstrated that the yield of the imaging bar isn't steady, prompting contrasts of almost 3% between the first kV-based portion and the recalculated MV-based portion, for strong water as it were. MVCT images can be utilized for portion estimation purposes remembering that the outcome is at risk to variances. The procurement of an IVDT together with the MVCT image set, that will be utilized for portion is suggested.