Frameless stereotactic radiosurgery of a solitary liver metastasis using active breathing control and stereotactic ultrasound.

Background And Purpose: Radiosurgery of liver metastases is effective but a technical challenge due to respiration-induced movement. The authors report on the initial experience of the combination of active breathing control (ABC) with stereotactic ultrasound (B-mode acquisition and targeting [BAT]) for frameless radiosurgery.

Patients And Methods: A patient with a solitary, inoperable liver metastasis from cholangiocellular carcinoma is presented (Figure 4). ABC (Figure 3) was used for tumor/liver immobilization. Tumor/liver position was controlled and corrected using ultrasound (BAT; Figure 1). The tumor was irradiated with a single dose of 24 Gy.

Results: Using ABC, the motion of the tumor was significantly reduced and the overall positioning error was < 5 mm (Figure 2). BAT allowed a rapid localization of the lesion during breath hold which could be performed without difficulties for 20 s. Overall treatment time was acceptable (30 min).

Conclusion: Frameless stereotactic radiotherapy with the combination of ABC and BAT allows the delivery of high single doses to targets accessible to ultrasound with high precision comparable to a frame-based approach.