A highly compact packaging concept for ultrasound transducer arrays embedded in neurosurgical needles

State-of-the-art neurosurgery intervention relies heavily on information from tissue imaging taken at a pre-operative stage. However, the data retrieved prior to performing an opening in the patient’s skull may present inconsistencies with respect to the tissue position observed by the surgeon during intervention, due to both the pulsing vasculature and possible displacements of the brain. The consequent uncertainty of the actual tissue position during the insertion of surgical tools has resulted in great interest in real-time guidance techniques. Ultrasound guidance during neurosurgery is a promising method for imaging the tissue while inserting surgical tools, as it may provide high resolution images. Microfabrication techniques have enabled the miniaturisation of ultrasound arrays to fit needle gauges below 2 mm inner diameter. However, the integration of array transducers in surgical needles requires the development of advanced interconnection techniques that can provide an interface between the microscale array elements and the macroscale connectors to the driving electronics. This paper presents progress towards a novel packaging scheme that uses a thin flexible printed circuit board (PCB) wound inside a surgical needle. The flexible PCB is connected to a probe at the tip of the needle by means of magnetically aligned anisotropic conductive paste. This bonding technology offers higher compactness compared to conventional wire bonding, as the individual electrical connections are isolated from one another within the volume of the paste line, and applies a reduced thermal load compared to thermo-compression or eutectic packaging techniques. The reduction in the volume required for the interconnection allows for denser wiring of ultrasound probes within interventional tools. This allows the integration of arrays with higher element counts in confined packages, potentially enabling multi-modality imaging with Raman, OCT, and impediography. Promising experimental results and a prototype needle assembly are presented to demonstrate the viability of the proposed packaging scheme. The progress reported in this work are steps towards the production of fully-functional imaging-enabled needles that can be used as surgical guidance tools

Should Initial Surveillance of Vestibular Schwannoma Be Abandoned?

Early diagnosis of vestibular schwannoma (VS) has increased in recent years because of increased longevity and availability of magnetic resonance imaging (MRI). Initial conservative radiological surveillance is often requested by patients and physicians to establish whether these tumors are growing before embarking on intervention. Initial observation of at least 1 year in all small VS was therefore recommended by some authors. We evaluated our prospective skull base database of VSs that were managed with initial radiological surveillance to establish when this policy should be abandoned and what predicts future growth. Fifty-four consecutive patients with VS in our institution who were managed by initial yearly MRI scanning were studied. The MRI data were collected prospectively and analyzed by Kodak CareStream viewing software where VS maximum diameters in three perpendicular planes and volume were calculated. One patient was excluded from the analysis as he had only one MRI follow-up. The median age of the 53 patients was 59 years (range, 26 to 86 years), 25 were males and 28 were females, and 33 were under 65 years of age; 18 VSs were extracanalicular, 18 were intracanalicular, and 17 extended both inside and outside the canal; 21 VSs were 1.2 cm3 or less, 22 were 1.2 to 4 cm3, and the rest were >4 cm3. Using volumetric analysis, 29.72% of conservatively managed VS grew by at least 2 mm per year, and 70.82% did not grow in 5 years. Age, gender, symptoms, and side did not predict future growth. However, growth in the first year was a strong predictor of future growth (p < 0.001) and initial volume was also a strong predictor of future growth (p < 0.05). Twenty-nine percent of observed VSs grew by at least 2 mm per year in the first 5 years of surveillance. As the growth rate is slow, initial radiological surveillance is justified in elderly patients and patients with small VSs and nonserviceable hearing. Growth in the first year was a strong predictor of future growth. The reported treatment effect should be interpreted in the light of 70.24% of VSs that either shrink or do not change in the first 5 years