Evaluation of Residual Liver Motion Using Multiphase Computed Tomography in Stereotactic Body Radiotherapy: A...

The liver is highly susceptible to internal motion during stereotactic body radiotherapy, requiring effective motion management. This study used multiphase computed tomography (MPCT) to assess residual liver movement under deep inspiration breath hold (DIBH), abdominal compression (AC) and free breathing (FB), comparing patient-specific internal target volume (PSITV) and generalized internal target volume (GITV).

A retrospective analysis of 57 patients with multiple hepatic targets was conducted, where motion management techniques included DIBH (n = 18), AC (n = 24), and FB (n = 15), with each patient undergoing five CT phases (noncontrast, arterial, portal, venous, and delayed). Maximum liver displacements for each patient in the craniocaudal (CC), mediolateral (ML), and anteroposterior (AP) directions were measured to generate PSITVs. The mean displacement across all patients for each technique was taken as the GITV.

Maximum motion occurred in the CC direction, highest in FB (6.73 ± 0.83 mm), followed by AC (5.91 ± 0.50 mm) and DIBH (5.36 ± 0.46 mm). ML and AP motions were similar across techniques: DIBH (2.92 ± 0.33 mm, 3.08 ± 0.38 mm), AC (3.02 ± 0.26 mm, 3.66 ± 0.51 mm), and FB (3.00 ± 0.31 mm, 3.37 ± 0.53 mm). Differences were not statistically significant (P > 0.3). PSITV was 3.3% larger than GITV in AC, while GITV exceeded PSITV by 2.5% in DIBH.

MPCT identified residual hepatic motion across motion management techniques, highlighting PSITV's role in improving dosimetric precision and reducing radiation exposure to adjacent organs and normal liver.