Intraoperative Ultrasound Applications in Intracranial Surgery

The methods and use of intraoperative ultrasound in 33 canine and five feline patients and its ability to localize and identify anatomical structures and pathological lesions in canines and felines undergoing intracranial surgery are described from a case series. All were client-owned referral patients admitted for neurologic evaluation, with an advanced imaging diagnosis of an intracranial lesion, and underwent surgical biopsy or surgical removal of the lesion. Medical records, retrieval and review of imaging reports, and characterization of findings for all canine and feline patients show that intraoperative ultrasound guidance was used in intracranial procedures during the period of 2012 and 2019. Twenty-nine of the canine patients had intracranial tumors. The remainder had various other conditions requiring intracranial intervention. Three of the feline patients had meningiomas, one had a depressed skull fracture, and one had an epidural hematoma. The tumors appeared hyperechoic on intraoperative ultrasound with the exception of cystic portions of the masses and correlated with the size and location seen on advanced imaging. Statistical comparison of the size of images seen on ultrasound and on MRI for 20 of the canine tumors revealed no statistical differences. Neuroanatomical structures, including vascular components, were easily identified, and tumor images correlated well with preoperative advanced imaging. The authors conclude that intraoperative ultrasound is a valuable asset in intracranial mass removals and can augment surgical guidance in a variety of intracranial disorders that require surgery. This is the first known publication in veterinary surgery of using intraoperative ultrasound as a tool in the operating theater to identify, localize, and monitor the removal/biopsy of intracranial lesions in small animals undergoing craniotomy/craniectomy.

ITVT-05. Intraoperative Ultrasound Guidance Improves Resection In Gliomas – Results From A Single Centre Propensity Matched Comparative Cohort Analysis Of 2D Vs Navigated 3D Ultrasound In 500 Gliomas

INTRODUCTION Intraoperative ultrasound (iUS) is a promising tool for glioma surgery. Navigated 3-D (n3D) iUS has many benefits over standard 2-D iUS. METHODS This was a retrospective comparative cohort study using propensity score matching (PSM). 500 consecutive histologically confirmed gliomas were divided into 2 cohorts – 2DiUS - Cohort A; and n3DiUS -Cohort B. PSM was used to account for known confounders (250 in each group; 1:1 matching). Gross total resection rates (based on iUS findings as well as postoperative MR) and perioperative morbidity were analyzed across the groups as were factors influencing these outcomes (using univariate as well as multivariate regression models). RESULTS Overall, the majority of the patients were adults (94%), males (71%) with hemispheric tumors (96%). 35% had tumors close to eloquent regions and 23% had received some prior treatment. The majority were high-grade gliomas (85%). 2D iUS was employed mainly for localization (80%) whereas n3D was used predominantly for resection control (84%) [p < 0.001]. GTR rate was higher in the n3D cohort (55.2% vs 38.4% in 2D; p = 0.001). The odds of having a complete resection in the n3D cohort was twice that of the 2D. Prior treatment, hemispheric location, and use of fluorescence were also significantly associated with higher GTR rates on univariate analysis. On multivariate analysis, all of these remained significant. There was no difference in the morbidity rates in the two cohorts. N3D iUS had a higher specificity and positive likelihood ratio in detecting tumor residue. CONCLUSION For hemispheric gliomas undergoing resective surgery, the use of navigated 3D ultrasound improves GTR rates, with no added morbidity. It is more likely to be used for resection control mode than is 2DUS and this is probably because n3DUS is more specific and likely to pick up tumor residues contributing to its better accuracy.

ITVT-06. Application of artificial intelligence and radiomics for the analysis of intraoperative ultrasound images of brain tumors

BACKGROUND Intraoperative ultrasound (ioUS) images of brain tumors contain information that has not yet been exploited. The present work aims to analyze images in both B-mode and strain-elastography using techniques based on artificial intelligence and radiomics. We pretend to assess the capacity for differentiating glioblastomas (GBM) from solitary brain metastases (SBM) and also to assess the ability to predict the overall survival (OS) in GBM. METHODS We performed a retrospective analysis of patients who underwent craniotomy between March 2018 to June 2020 with GBM and SBM diagnoses. Cases with an ioUS study were included. In the first group of patients, an analysis based on deep learning was performed. An existing neural network (Inception V3) was used to classify tumors into GBM and SBM. The models were evaluated using the area under the curve (AUC), classification accuracy, and precision. In the second group, radiomic features from the tumor region were extracted. Radiomic features associated with OS were selected employing univariate correlations. Then, a survival analysis was conducted using Cox regression. RESULTS For the classification task, a total of 36 patients were included. 26 GBM and 10 SBM. Models were built using a total of 812 ultrasound images. For B-mode, AUC and accuracy values ranged from 0.790 to 0.943 and from 72 to 89 % respectively. For elastography, AUC and accuracy values ranged from 0.847 to 0.985 and from 79 to 95 % respectively. Sixteen patients were available for the survival analysis. A total of 52 radiomic features were extracted. Two texture features from B-mode (Conventional mean and GLZLM_SZLGE) and one texture feature from strain-elastography (GLZLM_LZHGE) were significantly associated with OS. CONCLUSIONS Automated processing of ioUS images through deep learning can generate high-precision classification algorithms. Radiomic tumor region features in B-mode and elastography appear to be significantly associated with OS in GBM.

INNV-09. SURGICAL STRATEGIES FOR OLDER PATIENTS WITH GLIOBLASTOMA

OBJECTIVE Though image-guided surgery with intraoperative magnetic resonance imaging (IoMRI) is associated with higher extent of resection, we aimed to determine the clinical outcome of its use, compared to other less time-consuming intraoperative ultrasound (IoUS), in this patient population. METHODS Clinical data of 221 consecutive patients aged 70 years or older, who underwent surgical resection for GBM with intraoperative ultrasonography (IoUS) alone or combination of IoMRI + IoUS at Yale New Haven Hospital and Memorial Sloan Kettering Cancer Center were retrospectively reviewed. Variables were analyzed, and comparative analyses were performed, including predictors of overall survival. RESULTS The addition of IoMRI was not superior to IoUS alone in terms of overall survival (OS) (HR=0.85, 95% CI 0.49-1.47; P= 0.56) or Karnofsky Performance Score (KPS) at 6 weeks postoperatively (OR=0.51, 95% CI 0.22-1.15; P= 0.102). On the contrary, the length of surgery (LOSx) was significantly longer (P< 0.0001) in the IoMRI group. Postoperative complications were significantly less in the IoUS-only group (OR=0.17, 95% CI 0.3-0.46; P=0.002) and in patients who had a preoperative KPS score of 70 or higher (OR=0.092, 95% CI 0.018-0.47; P=0.004). Patients with relatively lower preoperative KPS scores (< 70) showed significant clinical improvement at 6 weeks postoperatively (P=0.0002). Patients with postoperative complications were more likely to have lower KPS scores at 6 weeks postoperatively (OR=0.30, 95% CI 0.10-0.89; P= 0.031), while increased extent of resection was associated with improved KPS scores at 6 weeks postoperatively (OR=2.171, 95% CI 1.22-3.87; P= 0.009). CONCLUSION Aggressive management with surgical resection should be considered in older patients with GBM, even those with relatively poor KPS scores. The use of IoMRI in this patient population does not appear to yield any survival benefit over IoUS but instead significantly prolongs the length of surgery, increasing the risk for potential postoperative complications.

Ultrasonic spine surgery for every thoracic disc herniation: a 43-patient case series and technical note demonstrating safety and efficacy using a partial transpedicular thoracic discectomy with ultrasonic aspiration and ultrasound guidance

OBJECTIVE Thoracic disc herniations (TDHs) are a challenging pathology. A variety of surgical techniques have been used to achieve spinal cord decompression. This series elucidates the versatility, efficacy, and safety of the partial transpedicular approach with the use of intraoperative ultrasound and ultrasonic aspiration for resection of TDHs of various sizes, locations, and consistencies. This technique can be deployed to safely remove all TDHs. METHODS A retrospective review was performed of patients who underwent a thoracic discectomy via the partial transpedicular approach between January 2014 and December 2020 by a single surgeon. Variables reviewed included demographics, perioperative imaging, and functional outcome scores. RESULTS A total of 43 patients (53.5% female) underwent 54 discectomies. The most common presenting symptoms were myelopathy (86%), motor weakness (72%), and sensory deficit (65%) with a symptom duration of 10.4 ± 11.6 months. A total of 21 (38.9%) discs were fully calcified on imaging and 15 (27.8%) were partially calcified. A total of 36 (66.7%) were giant TDHs (> 40% canal compromise). The average operative time was 197.2 ± 77.1 minutes with an average blood loss of 238.8 ± 250 ml. Six patients required ICU stays. Hospital length of stay was 4.40 ± 3.4 days. Of patients with follow-up MRI, 38 of 40 (95%) disc levels demonstrated < 20% residual disc. Postoperative Frankel scores (> 3 months) were maintained or improved for all patients, with 28 (65.1%) patients having an increase of 1 grade or more on their Frankel score. Six (14%) patients required repeat surgery, 2 of which were due to reherniation, 2 were from adjacent-level herniation, and 2 others were from wound problems. Patients with calcified TDHs had similar improvement in Frankel grade compared to patients without calcified TDH. Additionally, improvement in intraoperative neuromonitoring was associated with a greater improvement in Frankel grade. CONCLUSIONS The authors demonstrate a minimally disruptive, posterior approach that uses intraoperative ultrasound and ultrasonic aspiration with excellent outcomes and a complication profile similar to or better than other reported case series. This posterior approach is a valuable complement to the spine surgeon’s arsenal for the confident tackling of all TDHs.

Surgical advances in the management of brain metastases

As the epidemiological and clinical burden of brain metastases continues to grow, advances in neurosurgical care are imperative. From standard magnetic resonance imaging (MRI) sequences to functional neuroimaging, preoperative workups for metastatic disease allow high-resolution detection of lesions and at-risk structures, facilitating safe and effective surgical planning. Minimally invasive neurosurgical approaches, including keyhole craniotomies and tubular retractors, optimize the preservation of normal parenchyma without compromising extent of resection. Supramarginal surgery has pushed the boundaries of achieving complete removal of metastases without recurrence, especially in eloquent regions when paired with intraoperative neuromonitoring. Brachytherapy has highlighted the potential of locally delivering therapeutic agents to the resection cavity with high rates of local control. Neuronavigation has become a cornerstone of operative workflow, while intraoperative ultrasound (iUS) and intraoperative brain mapping generate real-time renderings of the brain unaffected by brain shift. Endoscopes, exoscopes, and fluorescent-guided surgery enable increasingly high-definition visualizations of metastatic lesions that were previously difficult to achieve. Pushed forward by these multidisciplinary innovations, neurosurgery has never been a safer, more effective treatment for patients with brain metastases.

Intraoperative Ultrasound in Colorectal Surgery

Intraoperative ultrasound (IOUS) in colorectal surgery can be used both in benign and in malignant lesions. In benign cases, such as Crohn’s disease and diverticulitis, it can orient toward the extension of the surgical intervention. In malignant cases, such as colorectal cancer with liver metastases, IOUS/CE-IOUS (contrast-enhanced) improved the intraoperative management of liver metastases by dictating the resection margins in relation to the tumor extension. The IOUS method allows for exact tumor location, intestinal wall visualization, and malignant tumor penetration. The IOUS revealed the tumor and its margin in rectal lesions, making the sphincter-sparing operation easier to perform. In patients with small polyps and early colon and rectum cancers, IOUS works well as a one-of-a-kind intraoperative localization technique. In comparison with IOUS, CE-IOUS offered better detection and resection guidance. Intraoperative ultrasound enables surgeons to easily localize small, non-palpable lesions of the large bowel. Furthermore, it can determine even the aggressive potential of these lesions with high precision.

Versatile Use of Intraoperative Ultrasound Guidance for Brain Puncture

BACKGROUND Intraoperative ultrasound (iUS) is an effective guidance and imaging system commonly used in neuro-oncological surgery. Despite the versatility of iUS, its utility for single burr hole puncture guidance remains fairly underappreciated. OBJECTIVE To highlight the simplicity, versatility, and effectiveness of iUS guidance in brain puncture by presenting the current case series and technical note collection. METHODS We present 4 novel uses of iUS guidance for single burr hole brain puncture: cannulation of normal-sized ventricles, endoscopic third ventriculostomy (ETV) guidance, evacuation of interhemispheric empyema, and stereotactic biopsy assistance. RESULTS All techniques were performed successfully in a total of 16 patients. Normal-sized ventricles were cannulated in 7 patients, among whom 5 underwent Ommaya reservoir placement and 2 underwent ventriculoperitoneal shunt placement for idiopathic intracranial hypertension. No more than 1 attempt was needed for cannulation. All ventricular tip positions were optimal as shown by postoperative imaging. iUS guidance was used in 5 ETV procedures. The working cannula was successfully introduced to the lateral ventricle, providing the optimal trajectory to the third ventricular floor in these cases. Interhemispheric subdural empyema was aspirated with iUS guidance in 1 patient. Volume reduction was clearly visible, allowing near-total evacuation of the empyema. iUS guidance was used for assistive purposes during stereotactic biopsy in 3 patients. No major perioperative complications were observed throughout this series. CONCLUSION iUS is an effective and versatile guidance system that allows for real-time imaging and can be easily and safely employed for various brain puncture procedures.