Use of AlignRT System During Stereotactic Radiosurgery

This was a prospective, single-group clinical study conducted at the Institute of Oncology Ljubljana. The study included adult patients with brain metastases who were scheduled to receive single-fraction stereotactic radiosurgery using the TrueBeam STx linear accelerator.

Each participant underwent two positioning procedures before treatment. Standard manual positioning was performed using the delta couch shift function, followed by partial CBCT verification. The participant was then positioned automatically using the AlignRT surface-guided radiotherapy system, followed by a second partial CBCT verification.

Residual positioning deviations were recorded in three translational directions (vertical, longitudinal, and lateral) and three rotational directions (rotation, pitch, and roll). The average deviations obtained after manual positioning were compared with those obtained after AlignRT-guided positioning. Additional analyses considered participant age and sex. Positioning data were obtained from the ARIA information system and analyzed using Microsoft Excel and IBM SPSS.

A total of 20 participants completed the study. No additional follow-up was required after completion of the positioning measurements.

• Manual Patient Positioning (Other): Participants were manually positioned from the initial setup position to the treatment isocenter using the delta couch shift function. A partial cone-beam computed tomography scan was then performed to measure residual setup deviations in three translational and three rotational directions.
• AlignRT-Guided Patient Positioning (Other): Participants were automatically positioned at the treatment isocenter using the AlignRT surface-guided radiotherapy system. A partial cone-beam computed tomography scan was then performed to measure residual setup deviations in three translational and three rotational directions.

Primary outcomes

• Residual Translational Setup Deviations After Manual and AlignRT-Guided Positioning [Immediately after each positioning procedure and before stereotactic radiosurgery, during the same treatment visit.]: Residual setup deviations measured by partial cone-beam computed tomography in the vertical, longitudinal, and lateral directions, expressed in centimeters. Mean deviations were compared between manual positioning and AlignRT-guided positioning within the same participants.
• Residual Rotational Setup Deviations After Manual and AlignRT-Guided Positioning [Immediately after each positioning procedure and before stereotactic radiosurgery, during the same treatment visit.]: Residual setup deviations measured by partial cone-beam computed tomography for rotation, pitch, and roll, expressed in degrees. Mean deviations were compared between manual positioning and AlignRT-guided positioning within the same participants.

Secondary outcomes

• Difference in Absolute Translational Setup Deviations Between AlignRT-Guided and Manual Positioning [Immediately after each positioning procedure and before stereotactic radiosurgery, during the same treatment visit.]: Within-participant comparison of the absolute residual setup deviations measured in the vertical, longitudinal, and lateral directions after AlignRT-guided positioning and manual positioning. Deviations were expressed in centimeters. Smaller absolute deviations indicate greater positioning accuracy.
• Difference in Absolute Rotational Setup Deviations Between AlignRT-Guided and Manual Positioning [Immediately after each positioning procedure and before stereotactic radiosurgery, during the same treatment visit.]: Within-participant comparison of the absolute residual setup deviations measured for rotation, pitch, and roll after AlignRT-guided positioning and manual positioning. Deviations were expressed in degrees. Smaller absolute deviations indicate greater positioning accuracy.

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Adults aged 18 years or older
* Patients with brain metastases eligible for single-fraction stereotactic radiosurgery
* Treatment performed using the TrueBeam STx linear accelerator
* Able and willing to provide written informed consent.

Exclusion Criteria:

* Patients younger than 18 years
* Patients receiving fractionated stereotactic radiotherapy
* Treatment performed using a linear accelerator other than TrueBeam STx.

• Klemen Salmič, MSc, Principal investigator, Institute of Oncology Ljubljana