142 E. Sadiki et al.: Radioprotection 2026, 61( 2), 140 – 145 Fig. 1. Example of rigid registration between two CT acquisitions showing angular deviation of the intracavitary applicator between fractions.
Fig. 2. Illustration of applicator rotations along the three principal axes:( a) Lateral( X-axis),( b) Vertical( Y-axis), and( c) Axial rotation( Z-axis).
Fig. 3. Relative dose variation histogram for the bladder, rectum and CTV high-risk during simulated rotational displacements along the lateral( X-axis).
These variations are particularly concerning because they suggest that vertical displacements( e. g., patient movements or transportation between imaging and treatment rooms) can significantly affect the radiation distribution. Previous studies, including Pötter et al.( 2009) and Hoskin et al.( 1996), have shown that such displacements can lead to underdosing of the
CTV and overdosing of OARs, thereby increasing the likelihood of local recurrence and toxicity. Real-time imaging, such as MRI, can help detect and correct these displacements before dose delivery. Additionally, adaptive planning strategies could be implemented to adjust the treatment plan according to the variations in applicator positioning. Figure 4