Porównanie dwóch metod weryfikacji geometrycznej podczas radioterapii raka prostaty

Abstract

Aim

Analysis of the daily correction shifts obtained from the cone beam computed tomography (CBCT) and from the two orthogonal X-ray images (2D-kV).

Materials and methods

15 patients with prostate cancer treated by radiotherapy were taken for the study. The analysis was based on the image data obtained from two different methods of the image guidance (CBCT and 2D-kV). In particular, analysis included the comparison of the: (i) correction shifts, (ii) systematic and random errors and (iii) margins derived from the CBCT and 2D-kV.

Results

The analysis showed that the widest spreads (standard deviation) of the shifts were recorded along the sagittal and vertical axis, and were respectively 0.5 cm CBCT and 0.3 cm 2D-kV for sagittal and 0.4 cm CBCT and 0.3 cm 2D-kV for vertical axis. The systematic errors resulting from the use of both image guidance methods are comparable. The biggest discrepancy between the random errors was observed for the sagittal and vertical axis, and were respectively 0.46 cm CBCT and 0.29 cm 2D-KV for sagittal and 0.36 cm CBCT and 0.25 cm 2D-kV for vertical axis. The margins calculated for each of the imaging methods were respectively: (i) 1 cm for the sagittal axis and 0.9 cm for the transverse and vertical axes based on the CBCT imaging; and (ii) 0.9 cm for the transverse axis and 0.8 cm for the sagittal and the vertical axes based on the 2D-kV imaging.

Conclusion

CBCT allows the correction of displacement of the prostate based on the soft tissues and the bone anatomy. 2D-kV allows correction of prostate shifts only on the basis of the bones. The results obtained by the method of 2D-kV are flawed by 20% (along the sagittal axis) and by 9% (along the vertical axis) error with respect to the CBCT method.