Using Contrast-Enhanced Ultrasound for Brain Tumor Surgery

To the Editor: Recently, Prada et al1 reported an article assessing the use of intraoperative contrast-enhanced ultrasound (iCEUS) for brain tumor resection and demonstrated that this technique can improve the definition of brain tumor borders. Intraoperative noncontrast ultrasound (IOUS) is a useful tool that can track brain tumors during a surgical approach.1,2 Various authors have reported that brain metastasis is easily observed by IOUS with clear tumor border delimitation.3 Authors have asserted that brain metastases are tumors with good delimitation when disclosed by B-mode ultrasound; Prada et al confirmed these findings.1,4 In our series of cerebral metastases resection guided by IOUS (40 lesions in 33 patients), 22.5% (n = 9) of lesions lacked well-defined borders (3 breast, 3 melanoma, 2 lung, 1 bladder tumor metastasis) (Figure 1). Before surgical resection, only 1 patient underwent radiosurgery, which decreases tumor border definition.2 Two of the 9 lesions (22.2%) exhibited residual tumors in the surgical bed after “total” macroscopic resection. In 1 patient, the alleged area containing residual tumor was tracked by IOUS after tumor resection and confirmed by postoperative gadolinium magnetic resonance (Figure 2). In another patient, IOUS could not detect the residual tumor disclosed by postoperative gadolinium magnetic resonance. In the 2 cases, the IOUS B-mode image alone did not define tumor borders before resection or precisely detect residual tumors after macroscopic tumor resection (data not yet published).FIGURE 1: A, intraoperative brain ultrasound image of metastasis from a breast tumor showing defined border. B, ultrasound ill-defined border brain metastasis from a lung tumor.FIGURE 2: A, intraoperative ultrasound image discloses ill-defined border of a brain metastasis from breast tumor. B, post-resection control ultrasound shows possible site of residual tumor. This suspected site was confirmed by contrast-enhanced magnetic resonance performed 3 days (C) and 2 months (D) after resection.Hammoud et al4 demonstrated total resection in all cerebral metastases with clearly demarcated border on US. Of tumors with moderate border delimitation, 40% exhibited local recurrence in this series, possibly associated with residual tumors after resection. Prada et al1 reported that the improvement in cerebral tumor border resolution was achieved after iCEUS use in ill-defined borders tumors as well as metastases lesions. iCEUS can differentiate between brain parenchyma edema and tumor. Thus, iCEUS may maximize tumor resection by avoiding healthy brain tissue damage. Total macroscopic resection of cerebral metastasis is associated with a decrease in tumor local recurrence and may improve patient quality of life, which is the main goal in brain metastases surgery.5 We believe that iCEUS could potentially enhance border definition in our series, improving macroscopic resection in the 2 cases with residual tumors. iCEUS can add important information to the standard B-mode image, providing enhanced metastases border definition and increasing the accuracy of pinpointing remaining lesions.1 Disclosure The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.