Intrafraction Imaging Can Replace the Midtreatment Cone Beam Tomography for Lung Stereotactic Ablative Radiation Therapy Patients for Increased Treatment Efficiency.

Purpose: To determine the feasibility of replacing the mid treatment cone beam computed tomography (MT CBCT) image with Intrafraction Imaging (IFI) acquired concurrently during dose delivery in lung Stereotactic Ablative Body Radiation therapy (SABR) patients, and thus improve treatment efficiency.

Methods And Materials: A review of departmental imaging data was performed on ten lung SABR patients treated with dual arc volumetric modulated arc therapy (VMAT) on an Elekta Versa HD linear accelerator with XVI imaging software.IFI data was extracted and a database of the translational (T T T) and the rotational (R R R) position errors was created for retrospective comparison, with the values of the MT CBCT for the same patients, treated between March 2021 and March 2022 at our center. The data was evaluated for correlation between the values in all 6° of freedom.

Results: The inter-class correlation (ICC) coefficient for T was 0.89 (95% CI, 0.80-0.94), T was 0.69 (95% CI, 0.49-0.82), T was 0.89 (95% CI, 0.82-0.95) in the translational planes, and R was 0.79 (95% CI, 0.65-0.88), R was 0.79 (95% CI, 0.65-0.88), and R was 0.91 (95% CI, 0.84-0.95) in rotational planes.The Bland-Altman (BA) statistics for T had a bias of -1.22 × 10, with an upper limit of agreement (UOA) of 0.07, and a lower limit of agreement (LOA) of -0.07, for T the bias was 0.01 (UOA: 0.18; LOA: -0.16), T bias was 2.6 × 10(UOA: 0.10; LOA: -0.09), R bias was 0.09 (UOA: 0.82; LOA: -0.64), R bias was -0.04 (UOA: 1.08; LOA: -1.16) and R was -0.03 (UOA: 0.44; LOA: -0.51).

Conclusions: The ICC was excellent for T, T R, and good for T. The data demonstrated promising correlation between IFI and MT CBCT values, and therefore supports the use of IFI for clinical decision making and improving treatment efficiency.