NIRS to measure microvascular haemodynamics in bone tissue Rob Meertens MScHSR BAppSci MRT May 2019 Overview What is NIRS Rationale for the project Work so far Systematic Review ID: 931242
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Slide1
The use of near infrared spectroscopy
(NIRS) to measure microvascular haemodynamics in bone tissue.
Rob Meertens
MSc(HSR
)
BAppSci
(MRT
)
May 2019
Slide2Overview
What is NIRS?Rationale for the project
Work so far
Systematic Review
Feasibility Work
ReliabilityValidationFuture Work
Slide3What is NIRS?
Slide4Current Clinical Applications
Mainly based around measuring blood oxygenation, perfusion and/or blood volume to tissue.
Assumes tissue remains constant except for
haemodynamic
changes in oxygenated and deoxygenated blood flow.Results are based on relative changes in oxygenated and deoxygenated haemoglobin
levels.
Slide5Pros and Cons of NIRS
Advantages
Fast
Relatively cheap
Non destructive
Non ionisingDisadvantagesLack of penetrative depth
Predominately only measures relative changes, not absolute values
Slide6Project Rationale
Bone is a dynamic and highly vascular tissue
Microvascular blood supply is a key factor in metabolic regulation of bone
Haemodynamics
in bone are notoriously difficult to measure with existing modalities.
Hence the vascular component of many bone pathologies remains
undetermined
(7)
Slide7Systematic Review
79 included studies:
15 NIRS
10 Photoplethysmography (PPG)
56 Laser Doppler Flowmetry (55 intra operative)
Varied anatomical sites:Calcaneus, Tibia, Patella,
NoF
, Sternum, Mandible
Various
Applications
Varied Study Design
(9)
(10)
(8)
Slide8Feasibility Work
Optimising a NIRS
protocol on
healthy
volunteers
Ruling out influence of:Overlying tissue
External
light sources
Probe
movement
Choice of Anatomical site
Participant tolerance
Slide9What can we measure
?
Relative changes in oxygenated (O2Hb) and deoxygenated (
HHb
) haemoglobin concentration:
Tissue Oxygenation Index (TOI; %)
Blood volume
Oxygen extraction
Reoxygenation
rates/Recovery time
Slide10Slide11Reliability: Existing Literature
Marker/Clinical Test
Within Subject Coefficient
of Variation
CTX
7.9% within two weeks; 13.4% over one year
P1NP
8.4% over one year
DXA of Lumbar Spine
2.02%
(
5.60
%
LSC)
DCE-MRI of Bone
23.1% (Ischium); 14.4% (bone
mets
)
LDF
20-25
% for comparable skin measurements
NIRS Muscle Deoxygenation
14-30% deoxygenation rate
NIRS muscle Reoxygenation
14% reoxygenation rate
Slide12Validation Study
Looking for associations of NIRS results with other markers of bone health such as:
Bone Mineral Density measured by Dual X-ray Absorptiometry (DXA)
A Dynamic
Contrast Enhanced MRI (
DCE-MRI) protocol
Trabecular Bone Scoring results from DXA
Blood markers of bone metabolism (CTX & P1NP)
Slide13DXA vs NIRS
r
=-0.63 (p=<0.001)
r=0.57 (p=<0.001)
Slide14NIRS vs DCE-MRI
r
=-0.58 (p=0.001)
r
=-0.35 (p=0.08)
MUSCLE
BONE
Slide15Recommendations
More on normal physiology required including repeat measurements addressing normal variabilityFocussing on wider generalisability and
participant tolerability
Promising technological advances
Consensus on systems and approaches
Slide16Thanks
Prof Karen Knapp: Associate Professor of Musculoskeletal ImagingDr David Strain: Senior Clinical Lecturer
Dr Francesco Casanova: Associate Research Fellow
Ms Sue Ball: Statistician
Society and College of Radiographers CoRIPS Scheme
Slide17DXA vs DCE-MRI
r=-0.41 (p=0.03)
r=-0.39 (p=0.04)