The real-time molecular characterisation of human brain tumours during surgery using Rapid Evaporative Ionization Mass Spectrometry [REIMS] and Raman spectroscopy: a platform for precision medicine in neurosurgery

Aim: To investigate new methods for the chemical detection of tumour tissue during neurosurgery. Rationale: Surgeons operating on brain tumours currently lack the ability to directly and immediately assess the presence of tumour tissue to help guide resection. Through developing a first in human application of new technology we hope to demonstrate the proof of concept that chemical detection of tumour tissue is possible. It will be further demonstrated that information can be obtained to potentially aid treatment decisions. This new technology could, therefore, become a platform for more effective surgery and introducing precision medicine to Neurosurgery. Methods: Molecular analysis was performed using Raman spectroscopy and Rapid Evaporative Ionization Mass Spectrometry (REIMS). These systems were first developed for use in brain surgery. A single centre prospective observational study of both modalities was designed involving a total of 75 patients undergoing craniotomy and resection of a range of brain tumours. A neuronavigation system was used to register spectral readings in 3D space. Precise intraoperative readings from different tumour zones were taken and compared to matched core biopsy samples verified by routine histopathology. Results: Multivariate statistics including PCA/LDA analysis was used to analyse the spectra obtained and compare these to the histological data. The systems identified normal versus tumour tissue, tumour grade, tumour type, tumour density and tissue status of key markers of gliomagenesis. Conclusions: The work in this thesis provides proof of concept that useful real time intraoperative spectroscopy is possible. It can integrate well with the current operating room setup to provide key information which could potentially enhance surgical safety and effectiveness in increasing extent of resection. The ability to group tissue samples with respect to genomic data opens up the possibility of using this information during surgery to speed up treatment, escalate/deescalate surgery in specific phenotypic groups to introduce precision medicine to Neurosurgery.Open Acces

Imaging and Tissue Biomarkers of Choline Metabolism in Diffuse Adult Glioma: 18F-Fluoromethylcholine PET/CT, Magnetic Resonance Spectroscopy, and Choline Kinase α

The cellular and molecular basis of choline uptake on PET imaging and MRS-visible choline containing compounds is not well understood. Choline kinase alpha (ChoKa) is an enzyme that phosphorylates choline, an essential step in membrane synthesis. We investigate choline metabolism through 18F-fluoromethylcholine (18F-FMC) PET, MRS and tissue ChoKa in human glioma. 14 patients with suspected diffuse glioma underwent multimodal 3T MRI and dynamic 18F FMC PET/CT prior to surgery. Co-registered PET and MRI data were used to target biopsies to regions of high and low choline signal, and immunohistochemistry for ChoKa expression was performed. 18F-FMC/PET differentiated WHO grade IV from grade II and III tumours, whereas MRS differentiated grade III/IV from grade II tumours. Tumoural 18F-FMC/PET uptake was higher than in normal-appearing white matter across all grades and markedly elevated within regions of contrast enhancement. 18F-FMC/PET correlated weakly with MRS Cho ratios. ChoKa expression on IHC was negative or weak in all but one GBM sample, and did not correlate with tumour grade or imaging choline markers. MRS and 18F-FMC/PET provide complimentary information on glioma choline metabolism. Tracer uptake is, however, potentially confounded by blood-brain barrier permeability. ChoKa overexpression does not appear to be a common feature in diffuse glioma

The Karachi intracranial stenosis study (KISS) Protocol: an urban multicenter case-control investigation reporting the clinical, radiologic and biochemical associations of intracranial stenosis in Pakistan.

Background: Intracranial stenosis is the most common cause of stroke among Asians. It has a poor prognosis with a high rate of recurrence. No effective medical or surgical treatment modality has been developed for the treatment of stroke due to intracranial stenosis. We aim to identify risk factors and biomarkers for intracranial stenosis and to develop techniques such as use of transcranial doppler to help diagnose intracranial stenosis in a cost-effective manner. Methods/Design: The Karachi Intracranial Stenosis Study (KISS) is a prospective, observational, case-control study to describe the clinical features and determine the risk factors of patients with stroke due to intracranial stenosis and compare them to those with stroke due to other etiologies as well as to unaffected individuals. We plan to recruit 200 patients with stroke due to intracranial stenosis and two control groups each of 150 matched individuals. The first set of controls will include patients with ischemic stroke that is due to other atherosclerotic mechanisms specifically lacunar and cardioembolic strokes. The second group will consist of stroke free individuals. Standardized interviews will be conducted to determine demographic, medical, social, and behavioral variables along with baseline medications. Mandatory procedures for inclusion in the study are clinical confirmation of stroke by a healthcare professional within 72 hours of onset, 12 lead electrocardiogram, and neuroimaging. In addition, lipid profile, serum glucose, creatinine and HbA1C will be measured in all participants. Ancillary tests will include carotid ultrasound, transcranial doppler and magnetic resonance or computed tomography angiogram to rule out concurrent carotid disease. Echocardiogram and other additional investigations will be performed at these centers at the discretion of the regional physicians. Discussion: The results of this study will help inform locally relevant clinical guidelines and effective public health and individual interventions

Association between metabolic parameters from dynamic 18f-fluoromethylcholine pet, pharmacokinetic parameters from dce-mri, choline to creatine ratios from mrs and tissue immunohistochemistry for choline kinase alpha expression in human brain glioma

INTRODUCTION: Proton MR spectroscopy and Choline-PET probe different aspects of choline metabolism, and quantitative dynamic MRI yields information on vascular permeability and perfusion. The relationship between these features in different grades of glioma is, however, unclear. METHOD: 14 patients with suspected primary supratentorial glioma were recruited to this study. The mean values over the whole tumour (T2-FLAIR hyperintense regions) of DCE-derived pharmacokinetic parameters were correlated with tumour to background ratio (TBR: ratio of SUVmax in tumour to SUVmean in contralateral white matter for the 7-17-minute static PET images). Dynamic PET macroparameters were quantified with spectral analysis (SA) in six patients for whom metabolite data were available. Choline to creatine ratios (Cho/Cr) were extracted from 2D-CSI data over 257 MRS voxels and correlated with TBR. Tissue immunohistochemistry for choline kinase alpha expression in targeted biopsies was carried out in regions of tumour with high and low uptake on PET and Cho/Cr on MRS. RESULTS: We observed a positive significant correlation between DCE-MRI derived parameters and parameters obtained through SA of the dynamic choline-PET data as well as TBR. We also observed a positive significant correlation between MRS Cho/Cr and TBR, although this was weak when excluding WHO Grade IV tumours. We did not observe a strong correlation between choline markers on imaging and choline kinase alpha expression. CONCLUSION: The correlation between both DCE and MRS parameters with TBR indicates that a number of biological features affect the uptake of the PET tracer. DCE-MRI provides complimentary information to blood volume and permeability that may augment interpretation of PET data; and help address questions such as the degree to which tracer uptake is dominated by blood brain barrier permeability rather than metabolic activity. Choline imaging with PET and MRS may reflect metabolic processes that are not simply related to choline kinase alpha expression