Comparative study of the displacement of the selected clips in the cavity measured by orthogonal kilovoltage X-ray film in conditions of free breath and active breathing control for patients treated by external-beam partial breast irradiation / 中华放射肿瘤学杂志

ABSTRACT

Objective To compare the displacements of the clips in the cavity measured with orthagonal kilovoltage (KV) X-my plain film in conditions of moderate deep inspiration breathing hold(mDIBH) and free breath (FB), and compare the margins from clinical target volume (CTV) to planning target volume (PTV) based on the displacements. Methods Before radiotherapy, 2 and 5 sets of orthogonal KV plain film were respectively collected in mDIBH and FB group, then the automatic registration of the reconstructed KV plain film and DRR derived from the planning OF images was finished. In conditions of mDIBH and FB, the displacements of the selected clip at the same location in the different directions and of the different selected clips in the same direction were compared. The margins in three dimensional directions were calculated and compared in conditions of mDIBH and FB . Results In FB hold group, the difference of displacement in left-right (LR), cranial-caudal (CC) and anterior-posterior (AP) directions were statistically significant between the clips at the cranial and caudal border of the cavity (9. 7 mm and 10. 6 nun (Z = -2. 12,P =0. 037) ,7. 3 mm and 8. 3 mm (Z = -2. 31 ,P=0. 041) ,15.5 mm and 16. 1 nun (Z = -2. 32,P = 0. 041)), but not statistically significant for the clips at the bottom and lateral P=0.814),15.7 mm and 16.5 mm (Z=-0.26,P=0.856)). The corresponding differences in the different directions were statistically significant (5.0 mm and 7. 8 mm(Z = -2. 31, P =0. 036), 5.0 mm and 9. 3 nun (Z= -2. 21,P=0. 021),7. 8 mm and9.3 mm (Z= -2. 11,P=0.041)). In FB group, the differences of the displacements of the four selected clips were statistically significant in CC and AP directions (7.3 mm and 8.4 mm (Z= -2.45,P=0.021), 15.5 mm and 16.5 mm (Z= -2.41,P= 0.043)), but not in LF direction (10.6 nun and 10.6 mm (Z= -0.24,P=0. 815)). In mDIBH group, the displacements in LF direction were statistically significant (4. 4 mm and 5.4 mm (Z = -2. 31, P = O. 031)), but not in CC and AP directions (8. 6 mm and 8.6 mm (Z =-0. 21, P = 0. 815), 10. 5 mm and 10. 8 mm (Z = -0. 27 ,P =0. 754)). There were statistically significant difference of the margins in LF and AP directions (9.7 mm and 5.0 mm (Z= -2.34,P=0.029),15.5 mm and 9.3 mm (Z= -2. 31,P= 0.021)), but not in CC direction (7.3 mm and 7. 8 mm (Z= -0.29,P =0.770)) between mDIBH and FB conditions. Conclusions The margins extended from CTV to PTV for EBPBI should be determined based on the respiratory status, border location and border direction.