Dextroscope

The Dextroscope is a Virtual Reality (VR) environment designed to provide medical professionals with deeper understanding of a patient's complex 3D anatomical relationships and pathology. Although its main intended purpose is to enable surgeons to plan a surgical procedure (in particular, neurosurgery^[1]), it has also proven useful in research in cardiology^[2] ,^[3] radiology and medical education.^[4]

The Dextroscope allows its user to interact intuitively with a Virtual Patient. The Virtual Patient is composed of computer-generated 3D multi-modal images obtained from any DICOM tomographic data including CT, MRI, MRA, MRV, functional MRI and CTA, PET, SPECT and DTI. It can work with any multi-modality combination, supporting polygonal meshes as well.

The user sits at the Dextroscope 3D interaction console and manipulates the Virtual Patient using both hands in a similar manner to how one would manipulate a real object. Using stereoscopic visualisations displayed via a mirror, the Dextroscope user sees the Virtual Patient floating behind the mirror but within easy reach of the hands and uses flexible 3D hand movements to rotate and manipulate the object of interest. The Dextroscope allows virtual segmentation of organs and structures, making accurate 3D measurements, etc.

In one hand the user holds an ergonomically shaped handle with a switch that, when pressed, allows the 3D image to be moved freely as if it were an object held in real space. The other hand holds a pencil shaped stylus that is used to select tools from a virtual control panel and perform detailed manipulations and operations on the 3D image. The user does not see the stylus, handle or his/her hands directly, as they are hidden behind the surface of the mirror. Instead he/she sees a virtual handle and stylus calibrated to appear in exactly the same position as the real handle and stylus. The business end of the virtual handle can be selected to be anything that the software can create - drill tool, measurement tool, cutter, etc. Experience has shown that it is unnecessary to model the user's hands, provided that he/she can see and feel the real tools and that these perceptions match the virtual scene. This is highly advantageous since the hands would otherwise clutter the workspace and obscure the view of the object of interest.^[5]

One of the uses of the Dextroscope is to allow surgeons to interact with and manipulate the Virtual Patient and plan the ideal surgical trajectory - for example, by simulating inter-operative viewpoints or the removal of bone and soft tissue. Apart from being much faster to work this way than using a mouse and keyboard, this approach also provides the medical professional, typically a surgeon, with a greater degree of control over the 3D image - with the hands literally being able to reach inside to manipulate the image interior.

Manipulating the Virtual Patient – Virtual Reality Toolsets

The Dextroscope provides an extensive set of virtual tools that can be used to manipulate the 3D image. For example, there are dedicated tools to perform data segmentation to extract surgically relevant structures like the cortex or a tumor ,^[6] extract blood vessels,^[7] adjust the color and transparency of displayed structures to see deep inside the patient and even simulate some surgical procedures – such as the removal of bone using a simulated skull drilling tool.

Typical structures that can be segmented are tumors, blood vessels, aneurysms, parts of the skull base, and organs. Segmentation is done either automatically (when the structures are demarcated clearly by their outstanding image intensity - such as the cortex) or through user interaction (using for example an outlining tool to define the extent of the structure manually). A virtual ‘pick’ tool allows the user to pick a segmented object and uncouple it from its surroundings for closer inspection. A measurement tool provides accurate measurement of straight and curving 3D structures such as the scalp, and measure angles, such as those between vessels or bony structures (for example, when planning the insertion of a screw into the spine).

Neurosurgery Planning - Case Studies and Evaluations

The use of the Dextroscope has been reported for several neurosurgical clinical scenarios;^{[1] [8] [9]}

Screen Capture from the Dextroscope. This image shows a moment during the planning of a typical neurosurgical procedure involving an MRI, DTI, TMS data modalities.

- cerebral arteriovenous malformations^{[10] [11]}

- aneurysms^{[12] [13] [14]}

- cranial nerve decompression (in cases of trigeminal neuralgia and hemifacial spasm)^{[15] [16] [17]}

- meningiomas (convexity, falcine or parasagittal)^{[18] [19] [20]}

- ependymomas or subependymomas ^{[12] [21]}

- craniopagus twin separation^{[22] [23]}

- transnasal approaches^{[24] [25] [26]}

- key-hole approaches^{[27] [28] [29]}

- epilepsy^[30]

- and a great variety of deep-brain and skull base tumors^[31][32] (pituitary adenomas, craniopharyngiomas, arachnoid cysts, colloid cysts, cavernomas^[33] ,^[34] hemangioblastomas, chordomas, epidermoids, gliomas,^[35] jugular schwannomas, aqueductal stenosis, stenosis of Monro foramen, hippocampal sclerosis).^{[12] [36] [37] [38]}

Not only brain, but also spine pathology such as cervical spine fractures, syringomyelia, and sacral nerve root neurinomas have been evaluated.^[39]

For other uses of the Dextroscope in neurosurgery refer to ^{[40] [41] [42] [43] [44] [45] [46] [47] [48] [49] [50] [51]} .^[52]

Other surgical specialties

The Dextroscope has been applied also outside of neurosurgery to benefit any patient presenting a surgical challenge: an anatomical or structural complexity that requires planning of the surgical (or interventional) approach, for example, ENT^[53] orthopedic, trauma and cranio-facial ^{[54] [55] [56] [57]} ,^[58] cardiology^[59] and liver surgery. ^{[60] [61]}

Dextroscope and Diagnostic Imaging

Dextroscope is not just for surgeons - radiologists can benefit from it too. The rapid growth in multi-modal diagnostic imaging data routinely available has increased their workload tremendously. Using the Dextroscope, radiologists can reconstruct multimodal models from high volumes of 2D slices – hence facilitating a better understanding of the 3D anatomical structures and helping with the diagnosis.

Furthermore, the Dextroscope virtual reality environment helps bridge the gap between radiology and surgery - by allowing the radiologist to easily demonstrate to surgeons important 3D structures in a way that surgeons are familiar with.
This demonstration capabilities makes it also useful as a base for medical educators where to convey 3D information to students.^[62] In order to reach larger group of people in a classroom or auditorium, a version was manufactured called Dextrobeam.^[63]

The Dextroscope (and/or the Dextrobeam) was installed, (among other medical and research institutions) at:

The Dextroscope and Dextrobeam were a product of Volume Interactions Pte Ltd (a member of the Bracco Group), a company spun-off from the Kent Ridge Digital Labs research institute in Singapore. They received FDA 510(k) clearance and CE Marking.

References