Abstract
IntroductionNeuronavigation greatly improves the surgeons ability to approach, assess and operate on brain tumors, but tends to lose its accuracy as the surgery progresses and substantial brain shift and deformation occurs. Intraoperative MRI (iMRI) can partially address this problem but is resource intensive and workflow disruptive. Intraoperative ultrasound (iUS) provides real-time information that can be used to update neuronavigation and provide real-time information regarding the resection progress. We describe the intraoperative use of 3D iUS in relation to iMRI, and discuss the challenges and opportunities in its use in neurosurgical practice.MethodsWe performed a retrospective evaluation of patients who underwent image-guided brain tumor resection in which both 3D iUS and iMRI were used. The study was conducted between June 2020 and December 2020 when an extension of a commercially available navigation software was introduced in our practice enabling 3D iUS volumes to be reconstructed from tracked 2D iUS images. For each patient, three or more 3D iUS images were acquired during the procedure, and one iMRI was acquired towards the end. The iUS images included an extradural ultrasound sweep acquired before dural incision (iUS-1), a post-dural opening iUS (iUS-2), and a third iUS acquired immediately before the iMRI acquisition (iUS-3). iUS-1 and preoperative MRI were compared to evaluate the ability of iUS to visualize tumor boundaries and critical anatomic landmarks; iUS-3 and iMRI were compared to evaluate the ability of iUS for predicting residual tumor.ResultsTwenty-three patients were included in this study. Fifteen patients had tumors located in eloquent or near eloquent brain regions, the majority of patients had low grade gliomas (11), gross total resection was achieved in 12 patients, postoperative temporary deficits were observed in five patients. In twenty-two iUS was able to define tumor location, tumor margins, and was able to indicate relevant landmarks for orientation and guidance. In sixteen cases, white matter fiber tracts computed from preoperative dMRI were overlaid on the iUS images. In nineteen patients, the EOR (GTR or STR) was predicted by iUS and confirmed by iMRI. The remaining four patients where iUS was not able to evaluate the presence or absence of residual tumor were recurrent cases with a previous surgical cavity that hindered good contact between the US probe and the brainsurface.ConclusionThis recent experience at our institution illustrates the practical benefits, challenges, and opportunities of 3D iUS in relation to iMRI.
Highlights
Neuronavigation greatly improves the surgeon’s ability to approach, assess and operate on brain tumors, but tends to lose its accuracy as the surgery progresses and substantial brain shift and deformation occurs
We retrospectively evaluated patients who underwent imageguided brain tumor resection in the Advanced Multi-modal Image-Guided Operating (AMIGO) Suite [19, 20] at Brigham and Women’s Hospital in Boston, USA, between June 2020 and November 2020, where both Intraoperative ultrasound (iUS) and Intraoperative MRI (iMRI) were employed to guide the resection
We compared the clinical utility of iUS with preoperative MRI and iMRI in twenty-three patients (15 men, 8 women; age range 28-83 years) who underwent image-guided brain tumor resection in the AMIGO suite (Table 1)
Summary
Neuronavigation greatly improves the surgeon’s ability to approach, assess and operate on brain tumors, but tends to lose its accuracy as the surgery progresses and substantial brain shift and deformation occurs. Neuronavigation greatly improves the surgeon’s ability to approach, assess and operate on brain tumors, navigation based on preoperative MRI loses its accuracy as the surgery progresses, owing to substantial brain shift and deformation [5,6,7,8]. To improve image quality and resolution, higher field, closed configuration magnets are necessary, requiring either moving the patient deep into the bore of the magnet or moving the magnet to the patient on the operating room table This requirement makes it impractical to acquire multiple images to update neuronavigation as tumor resection progresses and tissue deformation ensues, due to the time cost associated with each iMRI imaging session. The common practice in iMRI guided brain tumor surgery is to perform a single iMRI imaging session near the end of intended resection for identifying any residual tumor
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