Abstract
Background. Respiratory motion may compromise the dose delivery accuracy in liver stereotactic body radiation therapy (SBRT). Motion management can improve treatment delivery. However, external surrogate signal may be unstable and inaccurate. This study reports the first case of liver SBRT based on internal electromagnetic motion monitoring in China.Materials and Methods. The patient with a primary liver cancer was treated with respiratory-gated SBRT guided by three implanted electromagnetic transponders. The treatment was carried out in breath-hold end-exhale with beam-on when the centroid of the three transponders drifted within 5 mm (left-right (LR), anterior-posterior (AP) and cranio-caudal (CC) directions) from the planned position. The motion monitoring treatments were delivered in breath-hold end-exhale mode with the energy of 6 MV in FFF mode with 1200 monitor units (MU) per minute. For each fraction, QA results, intertransponder distances, geometric checks as well as tumor motion logs were explicitly recorded.Results. Comparing with the plan data, distance variances between each two transponders were -0.056±0.032 cm, 0.017±0.033 cm and -0.082±0.068 cm. Geometric residual, the pitch, roll and yaw angles were 0.048±0.021 cm (threshold 0.2 cm), 2.17°±1.85°(threshold 10°), -2.42°±1.51° (threshold 10°) and 1.67°±1.07° (threshold 10°), respectively. The delivery time of the five fields were 13.8 s, 13.1 s, 11.18 s, 11.57 s, 11.62 s with the average value of 12.254±1.13 s. Treatment duration of each fraction ranged from 6.22 minutes to 21.43 minutes, with the average value of 11.25±5.03 minutes.Conclusions. The first case of liver SBRT patient of China based on internal electromagnetic motion monitoring was performed. The system had a high tracking accuracy, and it did not delay the treatment time. In addition, the patient did not show any severe side effects except for I°myelotoxicity. The internal electromagnetic motion monitoring system provides a real-time and direct way to track liver tumor targets.
Advantage of using deep inspiration breath hold with active breathing control and image-guided radiation therapy for patients treated with lung cancers