A novel tool for assessing the correlation of internal/external markers during SGRT guided stereotactic ablative radiotherapy treatments

Giulia Paolani; Silvia Strolin; Miriam Santoro; Giuseppe Della Gala; Giorgio Tolento; Alessandra Guido; Giambattista Siepe; Alessio G Morganti; Lidia Strigari

doi:10.1016/j.ejmp.2021.10.021

A novel tool for assessing the correlation of internal/external markers during SGRT guided stereotactic ablative radiotherapy treatments

Phys Med. 2021 Nov 30:92:40-51. doi: 10.1016/j.ejmp.2021.10.021. Online ahead of print.

Authors

Giulia Paolani¹, Silvia Strolin¹, Miriam Santoro¹, Giuseppe Della Gala¹, Giorgio Tolento², Alessandra Guido², Giambattista Siepe², Alessio G Morganti³, Lidia Strigari⁴

Affiliations

¹ Department of Medical Physics, IRCCS Azienda Ospedaliero-Universitaria di Bologna, 40138 Bologna, Italy.
² Department of Radiation Oncology, IRCCS Azienda Ospedaliero-Universitaria di Bologna, 40138 Bologna, Italy.
³ Department of Radiation Oncology, IRCCS Azienda Ospedaliero-Universitaria di Bologna, 40138 Bologna, Italy; Department of Experimental, Diagnostic and Specialty Medicine-DIMES, Alma Mater Studiorum, Bologna University, 40138 Bologna, Italy.
⁴ Department of Medical Physics, IRCCS Azienda Ospedaliero-Universitaria di Bologna, 40138 Bologna, Italy. Electronic address: lidia.strigari@aosp.bo.it.

PMID: 34856464
DOI: 10.1016/j.ejmp.2021.10.021

Abstract

Introduction: An in-house developed tool was implemented and validated to investigate the skin surface, hepatic dome, and target displacement for stereotactic ablative radiotherapy (SABR) of thoracic/abdominal lesions using a Surface Guided Radiation Therapy (SGRT) system combined with 4D- images.

Materials and methods: Fourteen consecutive patients with tumors near the hepatic dome undergoing SABR treatments were analyzed. For each patient, a planning 4D-CT and five 4D-CBCT images were acquired. The C-RAD technology was also used to register/monitor the position of the skin reference point (SRP) as an external marker representative of patient breathing. The 4D images were imported in the developed tool, and the absolute maximum height (P_max,dome) of the hepatic dome on the ten respiratory phases was semi-automatically detected. Similarly, the contour of the skin surface was extracted in correspondence with the SRP position. The tool has been validated using an ad hoc modified moving phantom with pre-selected amplitudes and numbers of cycles. The Pearson correlation coefficients and Bland-Altman plots were calculated.

Results: There was a strong correlation between the skin motion amplitude based on 4D-CBCT and the C-RAD in all the patients (0.90 ± 0.08). Similarly, the mean ± SD of Pearson correlation coefficients of skin and P_max,dome movements registered by 4D-CT and 4D-CBCT were 0.90 ± 0.05 and 0.94 ± 0.05, respectively. The mean ± SD of Pearson correlation coefficients comparing the skin and P_max,dome displacements within each imaging modality were 0.88 ± 0.05 and 0.90 ± 0.05 for 4D-CT and 4D-CBCT, respectively. The SRP displacement during the set-up imaging and the treatment delivery were similar in all the investigated patients. Similar results were obtained for the ad hoc modified phantom in the preliminary validation phase.

Conclusion: The strong correlation between the tumor/ hepatic dome and skin displacements confirms that the SGRT approach can be considered appropriate for intra- and inter-fraction motion management in SABR therapy.

Keywords: Abdominal target; Inter-fraction displacements; Intra-fraction displacements; Moving target; SABR; SGRT.