Application of Intraoperative Conventional and Contrast-Enhanced Ultrasound in Brain Metastases: A Preliminary Study.

Objectives: To investigate the value of intraoperative conventional and contrast-enhanced ultrasound in the surgical resection of brain metastases (BMs).

Methods: A total of 46 patients with solitary tumors were enrolled. Intraoperative conventional ultrasound was performed to locate the tumors and observe the size, echo characteristics, position, depth, and degree of peritumoral edema of BMs and compare them with the findings from preoperative magnetic resonance imaging (MRI). Contrast-enhanced ultrasound was performed on 7 BMs with unclear borders to observe the borders and perfusion pattern. Completeness of tumor resection was assessed by ultrasound and compared with the assessment from postoperative MRI.

Results: All BMs were detected by intraoperative conventional ultrasound. Although BMs had various ultrasonic manifestations, most of them had clear boundaries (32/46, 69.6%), severe peritumoral edema (33/46, 71.7%), and a rich blood supply (35/46, 76.1%). There was no significant difference in assessing tumor size and peritumoral edema between intraoperative conventional ultrasound and preoperative MRI (P = .121 and 1.000, respectively). BMs exhibited a rapidly inhomogeneous high enhancement and a delayed wash-out in enhancement compared with surrounding tissues on contrast-enhanced ultrasound. All the BMs had complete resection as assessed by intraoperative conventional ultrasound, which was confirmed by the postoperative MRI.

Conclusions: BMs have some certain characteristics on both conventional and contrast-enhanced ultrasound. Intraoperative conventional ultrasound plays a useful role in real-time navigation and assessing the completeness of tumor resection for neurosurgeons. In addition, contrast-enhanced ultrasound is helpful in recognizing the tumor borders when the distinction between BMs and surrounding tissues is unclear.