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Team
Team
Michael Chappell (Oxford University)
Michael Chappell (Oxford University)
Foo Lee Sze (UTAR)
Foo Lee Sze (UTAR)
This image is taken from the Internet and the copyright belongs to the Heart and Stroke Foundation of Canada.
Stroke is a pathology associated with rapid loss of brain function due to a sudden disruption of blood supply to the brain, resulting from ischemia or haemorrhage. An ischemic stroke is caused by a blocked blood vessel and a haemorrhagic stroke is triggered by internal bleeding, for example the rupture of a cerebral aneurysm. According to the Stroke Association, 85% of strokes are caused by ischemia and the remainder are due to haemorrhage.
Stroke is a pathology associated with rapid loss of brain function due to a sudden disruption of blood supply to the brain, resulting from ischemia or haemorrhage. An ischemic stroke is caused by a blocked blood vessel and a haemorrhagic stroke is triggered by internal bleeding, for example the rupture of a cerebral aneurysm. According to the Stroke Association, 85% of strokes are caused by ischemia and the remainder are due to haemorrhage.
Recent progress in acute stroke treatment has shown that thrombolysis - the treatment of breaking up and dissolving the blood clots - increases the survival rate and reduces the disability of ischemic stroke patients. Currently, the recombinant tissue plasminogen activator (rtPA) is the only Food and Drug Administration (FDA) approved thrombolytic treatment. The rtPA has a therapeutic window of ~6 hours after the onset of ischemia.
Recent progress in acute stroke treatment has shown that thrombolysis - the treatment of breaking up and dissolving the blood clots - increases the survival rate and reduces the disability of ischemic stroke patients. Currently, the recombinant tissue plasminogen activator (rtPA) is the only Food and Drug Administration (FDA) approved thrombolytic treatment. The rtPA has a therapeutic window of ~6 hours after the onset of ischemia.
However, the drug has some deadly side-effect such as intracranial haemorrhage. The incident rate of intracranial haemorrhage caused by the treatment ranges from 5 to 10% and the mortality rates as a result of the complication vary from 50 to 83%, about a 10-fold increase compared to the untreated group in some studies. Due to the restrictive therapeutic window and complication of rtPA administration, only approximately 5% of stroke patients are estimated to receive this therapy, though it could have potentially benefited 14 % of them.
However, the drug has some deadly side-effect such as intracranial haemorrhage. The incident rate of intracranial haemorrhage caused by the treatment ranges from 5 to 10% and the mortality rates as a result of the complication vary from 50 to 83%, about a 10-fold increase compared to the untreated group in some studies. Due to the restrictive therapeutic window and complication of rtPA administration, only approximately 5% of stroke patients are estimated to receive this therapy, though it could have potentially benefited 14 % of them.
The right movie shows the complication during a rtPA treatment: a secondary hematoma can be seen shrinking as blood disgorges into the ventricles [2]; with permission from S. Karger AG, Basel.
Amide proton transfer (APT) imaging
Amide proton transfer (APT) imaging
APT imaging is a form of chemical exchange saturation transfer (CEST) that allows the detection of previously undetectable amide protons due to its low concentration, through a chemical exchange reaction with the water protons. This new and novel imaging technique has the ability to measure cellular information such as pH. Since pH drop happens prior to cerebal infarction (cell death), APT imaging has the potential to better stratify patients for rtPA to increase the benefit and to outweigh the risk of the thrombolytic treatment.
APT imaging is a form of chemical exchange saturation transfer (CEST) that allows the detection of previously undetectable amide protons due to its low concentration, through a chemical exchange reaction with the water protons. This new and novel imaging technique has the ability to measure cellular information such as pH. Since pH drop happens prior to cerebal infarction (cell death), APT imaging has the potential to better stratify patients for rtPA to increase the benefit and to outweigh the risk of the thrombolytic treatment.
I am working closely with clinical and non-clinical collaborators at Oxford Acute Vascular Imaging Centre (AVIC), John Radcliffe (JR) Hospital, UK and Functional MRI of the Brain (FMRIB), Oxford University, UK. Developing the best quantification method of APT effect and facilitating APT imaging for clinical stroke imaging are some of the key components of my work.
I am working closely with clinical and non-clinical collaborators at Oxford Acute Vascular Imaging Centre (AVIC), John Radcliffe (JR) Hospital, UK and Functional MRI of the Brain (FMRIB), Oxford University, UK. Developing the best quantification method of APT effect and facilitating APT imaging for clinical stroke imaging are some of the key components of my work.
If you like the left video, please cite the following paper:
Foo, LS, Larkin, JR, Sutherland, BA, et al. Study of common quantification methods of amide proton transfer magnetic resonance imaging for ischemic stroke detection. Magn Reson Med. 2021; 85: 2188– 2200. https://doi.org/10.1002/mrm.28565
Selected publications:
L.S. Foo, J.R. Larkin, B.A. Sutherland, ..., N.R. Sibson, Y.K. Tee, "Study of Common Quantification Methods of Amide Proton Transfer Magnetic Resonance Imaging for Ischemic Stroke Detection", Magnetic Resonance in Medicine, 85: 2188-2200, 2021 (I.F 2019 = 3.635; Q1) . [Link]
L.S. Foo, W.S. Yap, Y.C. Hum, H.A. Manan, Y.K. Tee, "Analysis of Model-Based and Model-Free CEST Effect Quantification Methods for Different Medical Applications", Journal of Magnetic Resonance, Volume 310, January 2020, 106648 (I.F 2019 = 2.624; Q2) [Link]
Y. Msayib, G.W.J. Harston, Y.K. Tee et al., "Quantitative CEST Imaging of Amide Proton Transfer in Acute Ischaemic Stroke", Neuroimage: Clinical, 23:101833, 2019. (I.F 2018 = 3.943 ; Q1) [Link]
G.W.J., Harston, Y.K. Tee, N.P. Blockley et al., "Identifying the ischaemic penumbra using pH-weighted magnetic resonance imaging", Brain, 138: 36–42, 2015. [Link].
Y.K. Tee, G.WJ. Harston, N.P. Blockley et al., “Comparing Different Analysis Methods for Quantifying the MRI Amide Proton Transfer (APT) Effect in Hyperacute Stroke Patients”, NMR in Biomedicine, 27: 1019–1029, 2014. [Link]
G.W.J. Harston, Y.K. Tee et al, “Ventricular extension of intracerebral hemorrhage during intravenous thrombolysis”, Cerebrovascular Diseases, 36:324-325, 2013. [Link]
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