Introduction: Image guidance had been the backbone of neurosurgery for over two decades particularly during biopsy, implantation, lesion generation or surgical resection. The mainstay in recent years had been MRI or CT, neither of which in real time even when the procedures are carried out within the MRI or CT suite. Ultrasound had been used in neurosurgery for generations because of its perceived safety (lack of radiation), portability (does not require any special shielding) and its true real time imaging. However, the main limiting factor of the current devices is the size of ultrasound probe and quality of the images generated. This paper discusses a feasibility study to develop a working ultrasound probe in a conventional brain needle for neuronavigation (USINN) and its potential applications in neurosurgery.
Methods: A single element ultrasound transducer integrated into a conventional brain needle. This USINN needle was then tested on fresh frozen sheep brain, fresh pig brain and human Thiel brain. MRI scan of the all subjects were performed to assess the quality of the brain. A burr hole was made and the ultrasound needle probe was used to obtain ultrasound signals. A second burr hole was then created and various foreign body targets inserted to mimic tumors, cyst and bullet. Ultrasound scan was repeated to locate the targets and MRI scan was performed to confirm the location of the target that generated the ultrasound signal.
Results: The prototype USINN needle with a single element transducer incorporated at the tip was able to generate ultrasound signals that made it possible to locate/differentiate the ventricles, tumor, cyst and bullet from brain parenchyma.
Conclusions: We believe that USINN needle can play a crucial role in needle based procedures in neurosurgery, for instance, VP shunt insertion in slit ventricles, extra ventricular drain insertion, Intracranial pressure monitor insertion, stereotactic biopsy, DBS electrode insertion, possible identification of Fascial nerve during Acoustic neuroma surgery, Lumbar puncture and lumbar drain insertion etc.
Patient Care: The USINN needle will provide a real time feedback and it will improve the success rate in various needle based procedures in neurosurgery. It will improve the time taken by clinicians to gain access ventricles in emergency scenarios. For instance, EVD/VP shunt insertion in cases of benign intracranial hypertension, EVD placements in cases of acute rise in ICP such as blockade of foramen of Monroe by a colloid cyst and SAH extending in the ventricles. Similarly, the USINN needle will aid various other needle based procedures in emergency and elective settings.
Learning Objectives: We established that it is feasible to incorporate a single element array transducer at the tip of conventional brain needle, its potential applications in neurosurgery and the commercial viability. At present, 32 element array is being designed and we hope that we will be able to incorporate a 64 element array as a final product.