Published Work

Towards a Distributed, Chronically-Implantable Neural Interface

We present a family of innovations that together aim to address key challenges with current implantable technology. The ENGINI (Empowering Next Generation Implantable Neural Interfaces) platform utilises a 3-tier network (external processor, cranial transponder, subdural probes) to inductively couple power to, and communicate data from, a distributed array of freely-floating mm-scale probes. Unique features integrated into each probe include: 1) Niobium microwires for observing low frequency local field potentials (lf-LFPs) across  the cortical column; 2) Autonomous, self-calibrating instrumentation and power management; and 3) A hermetically-sealed micropackage. We are additionally engineering a surgical tool, to facilitate manual and robot-assisted insertion, within a streamlined neurosurgical workflow. Ongoing work is focused on system integration and preclinical testing.

The conversational position in endoscopic pituitary surgery

We describe a novel patient position for endoscopic transphenoidal surgery - the 'conversational position'. This position is a safe and effective alternative to the standard supine position, incorporating a semi-sitting position with the additional innovation of achieving a 'conversational position' by flexing the neck and turning the patient's head turned to face the surgeon. The 'conversational' position offers improvements in the surgical approach to sellar region, addressing specific intraoperative challenges such as maintaining a bloodless operative field, and enabling more intuitive and ergonomic surgical workflow.r for your readers to identify and find your piece.

Scalable multimodal convolutional networks for brain tumour segmentation

Brain tumour segmentation plays a key role in computer-assisted surgery. Deep neural networks have increased the accuracy of automatic segmentation significantly, however these models tend to generalise poorly to different imaging modalities than those for which they have been designed, thereby limiting their applications. For example, a network architecture initially designed for brain parcellation of monomodal T1 MRI can not be easily translated into an efficient tumour segmentation network that jointly utilises T1, T1c, Flair and T2 MRI. To tackle this, we propose a novel scalable multimodal deep learning architecture using new nested structures that explicitly leverage deep features within or across modalities. This aims at making the early layers of the architecture structured and sparse so that the final architecture becomes scalable to the number of modalities. We evaluate the scalable architecture for brain tumour segmentation and give evidence of its regularisation effect compared to the conventional concatenation approach.on certain pages, include those details and the date of publication to make it easier for your readers to identify and find your piece.

Generalised wasserstein dice score for imbalanced multi-class segmentation using holistic convolutional networks

The Dice score is widely used for binary segmentation due to its robustness to class imbalance. Soft generalisations of the Dice score allow it to be used as a loss function for training convolutional neural networks (CNN). Although CNNs trained using mean-class Dice score achieve state-of-the-art results on multi-class segmentation, this loss function does neither take advantage of inter-class relationships nor multi-scale information. We argue that an improved loss function should balance misclassifications to favour predictions that are semantically meaningful. This paper investigates these issues in the context of multi-class brain tumour segmentation. Our contribution is threefold. (1) We propose a semantically-informed generalisation of the Dice score for multi-class segmentation based on the Wasserstein distance on the probabilistic label space. (2) We propose a holistic CNN that embeds spatial information at multiple scales with deep supervision. (3) We show that the joint use of holistic CNNs and generalised Wasserstein Dice score achieves segmentations that are more semantically meaningful for brain tumour segmentation.r piece.

Preoperative Particle and Glue Embolisation of Meningiomas: Indications, results and lessons learnt from 117 consecutive patients.

BACKGROUND: Preoperative embolization of meningiomas remains contentious, with persisting uncertainty over the safety and efficacy of this adjunctive technique. OBJECTIVE: To evaluate the safety of presurgical embolization of meningiomas and its impact on subsequent transfusion requirement with respect to the extent of embolization and technique used.

METHODS: One hundred seventeen consecutive patients between 2001 and 2010 were referred for embolization of presumed intracranial meningioma before surgical resection. Glue and/or particles were used to devascularize the tumor in 107 patients, all of whom went on to operative resection. The extent and nature of embolization-related complications, degree of angiographic devascularization, and the intraoperative blood transfusion requirements were analyzed. RESULTS: Mean blood transfusion requirement during surgery was 0.8 units per case (range, 1-14 units). Blood transfusion was significantly lower in patients whose meningiomas were completely, angiographically devascularized (P = .035). Four patients had complications as a direct result of the embolization procedure. These included intratumoral hemorrhage in 2, sixth cranial nerve palsy in 1, and scalp necrosis requiring reconstructive surgery in 1 patient. CONCLUSION: The complication rate was 3.7%. No relationship between the embolic agent and the degree of devascularization was observed. Achieving a complete devascularization resulted in a lower blood transfusion requirement, considered an indirect measure of operative blood loss. This series demonstrates that preoperative meningioma embolization is safe and may reduce operative blood loss. We present distal intratumoral injection of liquid embolic as a safe and effective alternative to more established particle embolization techniques.

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Use of novel ANSPACH bone collector for bone autograft in anterior cervical discectomy and cage .

BACKGROUND: The use of interbody cages with bone autograft following anterior cervical discectomy is well documented. The use of high-speed drills in the drilling of the posterior osteophyte results in the production of bone dust with viable osteophytes. We report the use of the ANSPACH bone collector device, which can be connected to standard suction circuitry and used to collect this bone dust. METHOD/RESULTS: A group of six patients undergoing anterior cervical discectomies at one (4) or two levels (2). The bone collector was attached to the suction system. Following collection of the desired bone dust from the devices' collection chambers, it was fitted into the previously sized interbody cages and impacted into the disc spaces. The bone collector is a single-use, disposable device, delivered sterile, designed to connect to standard 6-mm suction tubing. The use of the bone collector provided sufficient bone material for complete filling of the interbody cages in all of the patients. DISCUSSION: The use of autogenous cancellous bone material is the gold standard with regards to bone graft. The collection of bone dust during the use of high-speed drills has a number of applications and could provide a useful source of viable osteogenic material in spinal, cranial and craniofacial procedures. CONCLUSION: The use of the ANSPACH bone collector incorporated into a standard suction system provides an efficient method of autograft collection, removing the need for an adjunctive procedure with associated donor-site morbidity.

Lateralizing and localizing values of ictal onset recorded on the scalp: evidence from simultaneous recordings with intracranial foramen ovale electrodes.

PURPOSE: The value of scalp recordings to localize and lateralize seizure onset in temporal lobe epilepsy has been assessed by comparing simultaneous scalp and intracranial foramen ovale (FO) recordings during presurgical assessment. The sensitivity of scalp recordings for detecting mesial temporal ictal onset has been compared with a "gold standard" provided by simultaneous deep intracranial FO recordings from the mesial aspect of the temporal lobe. As FO electrodes are introduced via anatomic holes, they provide a unique opportunity to record simultaneously from scalp and mesial temporal structures without disrupting the conducting properties of the brain coverings by burr holes and wounds, which can otherwise make simultaneous scalp and intracranial recordings unrepresentative of the habitual EEG. METHODS: Simultaneous FO and scalp recordings from 314 seizures have been studied in 110 patients under telemetric presurgical assessment for temporal lobe epilepsy. Seizure onset was identified on scalp records while blind to recordings from FO electrodes and vice versa. RESULTS: Bilateral onset (symmetric or asymmetric) was more commonly found in scalp than in FO recordings. The contrary was true for unilateral seizure onset. In seizures with bilateral asymmetric onset on the scalp, the topography of largest-amplitude scalp changes at onset does not have localizing or lateralizing value. However, 75-76% of seizures showing unilateral scalp onset with largest amplitude at T1/T2 or T3/T4 had mesial temporal onset. This proportion dropped to 42% among all seizures with a unilateral scalp onset at other locations. Of those seizures with unilateral onset on the scalp at T1/T2, 65.2% showed an ipsilateral mesial temporal onset, and 10.9% had scalp onset incorrectly lateralized with respect to the mesial temporal onset seen on FO recordings. In seizures with a unilateral onset on the scalp at electrodes other than T1/T2, the proportions of seizures with correctly and incorrectly lateralized mesial temporal onset were 37.5 and 4.2%, respectively. Thus the ratio between incorrectly and correctly lateralized mesial temporal onsets is largely similar for seizures with unilateral scalp onset at T1/T2 (16.7%) and for seizures with unilateral scalp onset at electrodes other than T1/T2 (11.2%). The onset of scalp changes before the onset of clinical manifestations is not associated with a lower proportion of seizures with bilateral onset on the scalp, or with a higher percentage of mesial temporal seizures or of mesial temporal seizures starting ipsilateral to the side of scalp onset. In contrast, the majority (78.4%) of mesial temporal seizures showed clinical manifestations starting after ictal onset on FO recordings. CONCLUSIONS: A bilateral scalp onset (symmetric or asymmetric) is compatible with a mesial temporal onset, and should not deter further surgical assessment. Although a unilateral scalp onset at T1/T2 or T3/T4 is associated with a higher probability of mesial temporal onset, a unilateral onset at other scalp electrodes does not exclude mesial temporal onset. A unilateral scalp onset at electrodes other than T1/T2 is less likely to be associated with mesial temporal onset, but its lateralizing value is similar to that of unilateral scalp onset at T1/T2. The presence of clinical manifestations preceding scalp onset does not reduce the localizing or lateralizing values of scalp recordings.