An MRS and PET guided biopsy tool for ultrasound-based intra-operative neuro-navigational systems.
Matthew Grech-Sollars1,2, Babar Vaqas3, Gerard Thompson4, Tara Barwick2,5, Lesley Honeyfield2, Kevin S O'Neill3, and Adam D Waldman1,2

1Division of Brain Sciences, Imperial College London, London, United Kingdom, 2Department of Imaging, Imperial College NHS Healthcare Trust, London, United Kingdom, 3Department of Neurosurgery, Imperial College NHS Healthcare Trust, London, United Kingdom, 4Department of Neuroradiology, Salford Royal NHS Foundation Trust, Salford, United Kingdom, 5Department of Surgery and Cancer, Imperial College London, London, United Kingdom

Synopsis

Glioma heterogeneity and the limitations of conventional structural MRI to identify agrressive tumour components limits targeting of stereotactic biopsy, and hence tumour characterisation. In vivo MR spectroscopy and PET allow for physiological characterisation of tumour and we here present a method for representing MRS and PET defined regions to biopsy using an ultrasound based neuronavigational system. Our method involves using colour-coded hollow spheres to represent the target biopsy regions, which can be easily identified during the surgery. This approach can be applied to target the most aggressive regions of a tumour and as a tool for imaging biomarker validation.

Background:

Heterogeneity in glioma limits tumour characterisation using stereotactic biopsy; it is frequently not possible to accurately target the most aggressive tumour components reliably from conventional structural imaging. In vivo MR spectroscopy (MRS) and PET allow cellular metabolism relevant to proliferation to be imaged non-invasively. Intra-operative ultrasound provides near real-time structural imaging for surgical guidance. Here we combine PET and MRS with ultrasound neuro-navigation to guide surgical biopsy for gliomas.

Methods:

An intra-operative neuro-navigation tool was developed as part of a study to sample high choline tumour components identified by MRS and 18F-methylcholine PET. 12 patients (7 male, 5 female; aged 23-73 years, mean 41 years) were recruited to the study. Spatially co-registered PET and MRS data were integrated into structural datasets and loaded onto a Neuronavigational 3D Ultrasound image guidance system. High and low choline uptake/metabolite regions were represented as colour coded hollow spheres for targeted biopsy (Figure 1).

Results:

The operating surgeons found the 3D spherical targets readily identifiable on the interactive navigation system and were able to register the images to the pre-surgery images and overlay the ultrasound imaging to take into account brain shift during surgery (Figures 2 and 3). In one case, areas of high mitotic activity were identified on the basis of high 18F-methylcholine uptake and elevated MRS choline ratios in an otherwise low-grade tumour.

Conclusions:

We have developed a PET and MRS targeted stereotactic biopsy tool using intraoperative ultrasound neuronavigation; this involves a combination of proprietary and bespoke software to analyse and integrate physiological imaging data, and novel presentation of biopsy targets as hollow spheres, which can readily be identified in the operating environment. Our preliminary experiences indicate that this method can be used to improve diagnostic accuracy of stereotactic biopsy. It also provides proof of principle for spatially-correlated validation of a variety of imaging biomarkers against tissue features.

Acknowledgements

This work was part funded by the NIHR Imperial Comprehensive Biomedical Research Centre. MGS is partly funded by The Brain Tumour Charity and Brain Tumour Research Campaign. We would also like to thank Ms Sophie Camp, Dr Katherine Ordidge and Mr Daniel Darian for their help in this study. MRI and PET imaging was carried out at the Imperial College Clinical Imaging Facility.

References

No reference found.

Figures

Fugre 1: Integration of PET and MRS onto a surgical plan. MRS data (top row) is analysed and the voxel to be sampled is selected (shown in red). A hollow sphere is then placed around this voxel (shown in yellow) to indicate the target area within the centre of the sphere to biopsy. PET data (middle row) is also analysed and the area to be sampled is indicated using a hollow sphere (shown in red) which is also added to the surgery planning image (top right).

Figure 2: The system in use in the operating theatre. The SonoWand system can be set to show the pre-surgery MRI images (left) together with the surgery plan (centre) and the the ultrasound overlaid image (right). The ultrasound images provide near real time surgery guidance. The 3D colour-coded hollow spheres allow for easy identification of targets at any angle. The green marker indicated where the sample was taken from during surgery.

Figure 3: The SonoWand system in use during craniotomy and resection of a glioma. The surgical plan was loaded onto the neuro-navigational system and used to identify the important target areas to biopsy. A neuronavigational recording of each sample was taken so that histology results from each sample could be compared to the MRS and PET results in the biopsied area.



Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)
1352