Bilateral metallic hip implants: Are avoidance sectors necessary for pelvic VMAT treatments?

• Main Authors: Dipasquale, G. (Author), Dubouloz, A. (Author), Jaccard, M. (Author), Koutsouvelis, N. (Author), Miralbell, R. (Author), Nouet, P. (Author), Rouzaud, M. (Author), Tsoutsou, P. (Author), Zilli, T. (Author)
• Format: Article
• Language: English
• Published: Elsevier GmbH 2021
• Subjects: adult; aged; Aged; Article; artifact reduction; Avoidance-sector; clinical article; comparative study; dosimetry; Hip-prosthesis; human; Humans; image guided radiotherapy; intensity modulated radiation therapy; male; Metallic Implants; patient positioning; Pelvic Tumors; pelvis; Pelvis; planning target volume; Radiotherapy; radiotherapy dosage; Radiotherapy Dosage; radiotherapy planning system; Radiotherapy Planning, Computer-Assisted; Radiotherapy, Image-Guided; Radiotherapy, Intensity-Modulated; VMAT; volumetric modulated arc therapy
• Online Access: View Fulltext in Publisher

 Purpose: Metallic hip implants (MHI) are common in elderly patients. For pelvic cancers radiotherapy, conventional approaches consist of MHI avoidance during treatment planning, which leads, especially in case of bilateral MHI, to a decreased quality or increased complexity of the treatment plan. The aim of this study is to investigate the necessity of using avoidance sectors (AvSe) using a 2-arcs coplanar pelvic volumetric modulated arc-therapy (VMAT) planning. Methods: We evaluated: (1) The dose calculation error of a static 6 MV open beam traversing a MHI; (2) The magnitude of an error's decrease within the planning target volume (PTV) for a 360° VMAT treatment without AvSe as compared to the static open beam; (3) The dosimetric influence of MHI misalignment generated by patient's repositioning rolls during image-guided radiotherapy (IGRT). Results: (1) In the static 6 MV beam configuration, for distances between 0.5 cm and 6 cm from the MHI, the median (maximum, number of points) dose calculation error was −1.55% (−2.5%, 11); (2) Compared to the static open beam, in the 360° VMAT treatment without AvSe a simulated error was decreased by a factor of 4.4/2.4 (median/minimum); (3) MHI anterior-posterior misalignment exceeding 0.6 cm, resulted in error at PTV surface of >2%. Conclusions: A standard 2 coplanar arcs 360° VMAT treatment, with dedicated artifact reduction algorithms applied, decreased the error of static beam traversing MHI, in patients presenting a bilateral MHI and might be used to treat the pelvic region without MHI avoidance. © 2021