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Single-fiber reflectance spectroscopy: Is it more accurate than radiography and computed tomography in identifying degenerated canine intervertebral discs?. Nigar Sultana 1 , Kelci McKeirnan 2 , Melanie A. Breshears 3 , Anqi Zhang 4 , Daqing Piao 1 and Kenneth E. Bartels 2 - PowerPoint PPT PresentationTRANSCRIPT
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Single-fiber reflectance spectroscopy: Is it more
accurate than radiography and computed tomography in
identifying degenerated canine intervertebral discs?
Nigar Sultana1, Kelci McKeirnan2, Melanie A. Breshears3, Anqi Zhang4, Daqing Piao1 and Kenneth E. Bartels2
1School of Electrical and Computer Engineering, Oklahoma State University, Stillwater, OK 74078, USA2Depertment of Veterinary Clinical Science, Oklahoma State University, Stillwater, OK 74078, USA3Depertment of Veterinary Pathobiology, Oklahoma State University, Stillwater, OK 74078, USA4Depertment of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21205, USA
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OVERVIEW Background
Motivation and Objective
System configuration
Imaging protocols
Results
Summery
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Background Intervertebral discs (IVD), located
between the vertebrae in the spine and act as “shock absorbing cushions” which allows slight movement of vertebrae
Intervertebral discs are comprised of two layers
o Annulus fibrosus ---Tough outer fibrous lamellar layer
o Nucleus pulposus --- Gelatinous inner core
Source: http://www.spineuniverse.com/conditions/herniated-disc
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Background Intervertebral disc herniation is a common disease that
affects the vertebra
The chondrodystrophoic dogs (dachshund, Pekingese, etc.) mainly seem to have disc degeneration along the entire vertebral column while it is even common in humans also
Loss of nucleus fluid and deposition of a calcified mineral component within the nucleus makes the disc degenerated
Degenerated disc is less resilient to normal wear and tear
Degeneration can cause severe pain, nerve compression and paralysis
Extrusion of degenerated disc material through the dorsal annulus
Source: http://www.mayfieldclinic.com/PEHLDisc.htm#.Ujy34sakquM
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BackgroundTreatment Surgical disc fenestration--- most widely
used treatment for intervertebral disc disease
It’s a highly invasive procedure
Very complex
Recurrence rate as high as 19.2 % as reported by several large scale studies of a mixed population of dogs
Source: http://cal.vet.upenn.edu/projects/saortho/chapter_62/62mast.htm
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Background Percutaneous Laser disc Ablation (PLDA)--- minimal
invasive procedure for intervention of intervertebral disc disease
This laser surgical treatment photothermally ablates the disc material and fibrotic scar tissue forms which presumably prevents the disc from herniating in the future
PLDA is performed by passing an optical fiber through a needle placed percutaneously in the center of a disc to introduce laser energy, most frequently from a 2100 nm holmium:YAG (Ho:YAG) laser
PLDA shown to have minimum recurrence rate as low as 3.4 %
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Motivation In current practice, PLDA is performed in thoracolumbar IVD with
same laser fluence applied to each disc, regardless of its mineral
content
Knowledge of individual disc mineral composition would allow
treatment of degenerated discs that otherwise may have been
missed
Mineralized volume quantization of individual disc would permit
laser energy dosage adjustments for specific degenerated disc
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Motivation (Imaging) Current standard for diagnostic imaging for canine
IVD degeneration is X-ray radiography, which usually
shows as opacification of the disc space
Radiography is also used to guide the needle
positioning into the center of each treated disc for
PLDA
However, radiography is not adequately sensitive in
identifying the degenerated discs, nor is it reliable
for characterizing the degree of disc degeneration
When compared with histopathology, radiography
has a sensitivity of 30 % and specificity of 100 % in
diagnosing disc degeneration
Source: http://www.vetsurgerycentral.com/myelogram.htm
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Motivation (imaging) X-ray computed tomography (CT) and magnetic
resonance imaging (MRI) usually able to pinpoint the precise location of degenerated disc
However, it is not also highly sensitive in characterizing
the degree of disc degeneration and sometimes provide misleading results in identifying the degenerated discs
When compared with histopathology, computed tomography (CT) has a sensitivity of 75% and specificity of 60 % in diagnosing disc degeneration
Moreover, due to the cost and inconvenience it is challenging to standardize PLDA surgery under CT or MRI image guidance
Source: http://www.mayfieldclinic.com/PE-HLDisc.htm#.Ujy7jsakquMhttp://canadawestvets.com/disc-disease
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Motivation (Optical) An imaging/sensing technology that provides a more accurate pre-
operative in-situ assessment of the disc mineralization,
and potentially rapid post-operative feedback, could optimize the outcome of the PLDA procedure
Single-fiber reflectance spectroscopy----
o Sense the changes of tissue compositions in the disc
o A diagnosis modality that could be integrated to PLDA procedure
http://www.dfwvetsurgeons.com/downloads/Newsflash_rdvm.pdf
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Hypothesis (scattering) The hypotheses
o The mineral deposit within degenerated IVD increases scattering
o IVD that contains mineral works as an avascular medium
o The more degenerated disc is, the more scattering the medium should become
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Objective The objective of this study is to revaluate whether the needle-
based single-fiber reflectance spectroscopy could have higher accuracy in identifying degenerated intervertebral discs compared to X-ray radiography and computed tomography (CT)
If needle-based single-fiber reflectance spectroscopy could provide a positive correlation with histopathology results
If SfRS could have a higher sensitivity in grading degree of disc degeneration
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System configuration Computer
Light Source Spectrometer
The experimental setup includes:
Halogen -Deuterium Source
Spectrometer
Bifurcated fiber bundle
320μm single fiber with 15°
angle polished tip
Computer
20 gauge needle150 angle polished fiber in needle
Schematic of Single fiber reflectance spectroscopy setup
single fiber
Bifurcated fiber bundle
15°
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Analytical Representation
)
Incident light intensity photon path length
absorption coefficientNormalized intensity
550 600 650 700 750 800 850 900 950 10000
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5x 10
4
wavelength (nm)
Inte
nsity
(a.u
.)
550 600 650 700 750 800 850 900 9503
3.5
4
4.5
5
5.5
6
6.5
7
7.5
8
wavelength (nm)
Nor
mal
ized
Inte
nsity
Raw Spectrum
Normalized Spectrum
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Imaging protocol
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Imaging protocol
extending~1mm
Reflectance spectroscop
y system
Acquisition time: 2 second/measurement-Step1: Measurements-Step2: PLDA procedure-Step3: Measurements
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No mineral present on radiographs
L2-3, slight nuclear mineralization
L4-5, no nuclear mineralization
Results (Dog#1 Radiography and CT)
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Results (Dog#2 Radiography and CT)
T10-11mineralized
T11-12mineralized
L2-3mineralized
L3-4mineralized
T12-13mineralized
L1-2mineralized
L4-5mineralized
L5-6mineralized
T8-9 T12-12 L2-3 L3-4 L4-5 L7-S1 are mineralized in radiograph
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19T10-11 mineralized
Results (Dog#3 Radiography and CT)
T10-11mineralized
T11-12mineralized
T12-13mineralized
T13-L1mineralized
L1-2mineralized
L2-3mineralized
L3-4mineralized
L4-5mineralized
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Results (Radiography and CT) Radiographic and CT imaging were performed on all thoracic and
lumbar intervertebral discs of the two cadaveric dogs
The needles for Single fiber reflectance spectroscopy sensing and
subsequently for PLDA were placed successfully in “ Dog 1” from T8– 9
to L5– 6 and in “ Dog 2 and Dog 3” from T9– 10 to L5– 6. Therefore only
the radiography and CT images of those discs being evaluated by Single
fiber reflectance spectroscopy measurement are displayed
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disc No
Radiograph
CT Pathology
T8-9 No mineralization No mineralization2 small foci of light mineralization within nucleus (<10%) with equivocal mineralization at periphery of presumptive char tract
T10-11 No mineralization Slight focal mineral in nucleus
No mineralization
T11-12 No mineralization No mineralization Large central focus of dense mineralization (60%) in nucleus
T12-13 No mineralization None No mineralization
T13-L1 No mineralization No mineralization 2 distinct foci of mineralization/bone within nucleus that composed approx. 35% of visible nucleus
L1-2 No mineralization No mineralization No mineralization
L2-3 No mineralization very focal mineral (nucleus)
Focus of dense mineralization near center of nucleus (in chondroid tissue) (30%)
L3-4 No mineralization No mineralization No mineralization
L4-5 No mineralization No mineralization No mineralization
L5-6 No mineralization No mineralization equivocal mineralization at edge of nuclear material surroundingdescribed focus of cavitation (10%)
Results (Dog1)
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Results (Dog2)disc No
Radiograph
CT Pathology
T10-11 No mineralization
rim mineralization of nucleus no mineralization on H&E
T11-12 No mineralization
rim mineralization of nucleus
2 small foci of mineralization in nucleus material (~5% of nucleus)
T12-13 small amount of mineral heavily mineralized
many foci of distinct mineralization (approximately 60% of nucleus material) admixed with granular debris interpreted to represent mineralized tissue
T13-L1 No mineralization
No mineralization no distinct mineralization in visible nucleus
L1-2 No mineralization
small amount of mineral no distinct mineralization in nucleus
L2-3 small amount of mineral
small amount of mineral
2 small and equivocal foci of mineralization in nucleus (approximately 10% of nucleus)
L3-4 small amount of mineral
small amount of mineral
multiple mineralized foci comprise approximately 40% of the nucleus
L4-5 small amount of mineral
small amount of mineral
basophilic coagulum interpreted to be charred mineralized material composes approximately 70% of nucleus
L5-6 No mineralization
small amount of mineral
mineralized tissue composes approximately 50% of nucleus tissue present in section
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Results (Dog3)disc No
Radiograph
CT Pathology
T10-11 mineralized large amount of mineral nearly all of the nucleus material on slide is VK+ (mineralized)
T11-12 no mineralization moderate mineral central nucleus
4 fairly large foci of mineralization in nucleus (approximately 40% of nucleus)
T12-13 no mineralization mineralized ventral aspect of nucleus
large foci of mineralization in nucleus comprise about 50% of nucleus
T13-L1 no mineralization mineralized and ruptured nucleus
large foci of mineralization in nucleus (40%) and annulus
L1-2 no mineralization small amount of focal mineral
central focus of mineralization comprises approx. 20% of the nucleus
L2-3 no mineralization small amount of focal mineral
central focus of mineralization comprises approx. 20% of the nucleus
L3-4 no mineralization small amount of focal mineral
central focus of mineralization comprises approx. 18% of the nucleus
L4-5 no mineralization very slight focal mineral <5% of nucleus is equivocally mineralized
L5-6 no mineralization No mineralizationcentral focus of mineralization comprises approx. 10% of the nucleus
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Results In histopathology result, 20 out of 28 discs
were determined to have different level of
mineral deposition (5/10 form dog1, 4/9
from dog2 and 9/9 from dog3)
Out of 20 degenerated discs
o Radiography identified 6 degenerated
discs
o CT was successfully identified 15
degenerated discs and
o SFRS identified 19 degenerated discs
correctly
1 2 3
5
10
15
20
25
No
of d
isc
Radiography CT Histopathology
15
20
6
R19 identified by SfRS
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Results Normalization is applied to all 28 discs
with respect to air and water from
entire optical range of 530-1000nm
Blue dashed line represents normalized
spectra of normal disc (T12-13-Dog1,
L3-4-Dog1 and L1-2 Dog1)
Red dotted line represents normalized
spectra of degenerated disc (T12-13-
Dog3, T13-L1-Dog3, L1-2-Dog-1, T11-
12-Dog1) identified by CT and
histopathology
550 600 650 700 750 800 850 900 950 10002
3
4
5
6
7
8
Wavelength (nm)
Nor
mal
ized
Inte
nsity
Degenerated
Normal
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T8-9 T10-11 T11-12 T12-13 T13-L1 L1-2 L2-3 L3-4 L4-5 L5-6
Pathology (% of mineral volume)
SfRS (avg normalized intensity of 530-1000nm)
Computed Tomography
(CT)
Radiography
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Mineralized Normal
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Results The comparison of SfRS normalized intensity with radiography and CT
based on histopathology result for discs T8-9, T10-11, T11-12, T12-13, T13-L1, L1-2, L2-3, L3-4, L4-5 and L5-6 are shown here for three cadaveric dogs
The red triangle represents degenerated disc and blue circle is the representation of normal disc (not having any mineral)
For SfRS, the normalized intensity with respect to air and water is presented on an average of optical range of 530-1000nm
SfRS result showed a good correlation with histopathology result of different percentage of mineral content by different normalized intensity level
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0 1 2 3 4 5 6 7 8 9 102
3
4
5
6
7
8
Receiver operating characteristic (ROC) curve for average normalized spectral intensity of SfRS from 530-1000nm is generated by varying threshold level to determine SfRS classification in identifying degenerated disc
Threshold is placed where SfRS could identified 19 out of 20 degenerated discs
T8-9 T10-11 T11-12 T12-13 T13-L1 L1-2 L2-3 L3-4 L4-5 L5-6
Results
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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1-Specificity
Sen
sitiv
ity
random guessSingle fiber Rs
AUC=0.841
ROC curve is the graphical presentation of sensitivity and specificity to determine system classification where,
The dotted line represents a random guess
of 50% accuracy
The solid line shows the sensitivity and
specificity when SfRS identified 19 out of 20
degenerated disc by threshold placement
Area under ROC curve of SfRS determined to
be 0.841
Results
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0 10 20 30 40 50 60 70 80 90 1000
1
2
3
4
5
6
7
8
9
10
Mineralized volume (%) in histopathology
Normalized
SfR
S In
tesity
R2=0.7625
SfRS normalized intesity averaged
from 530 to 1000 nm for all 28 discs
are plotted against the percentage
amout of mineralized volume
determined by histopathology
Up to 50% of mineralized volume,
the correlation coefficient, R
obtained as 0.8732 and coefficient
of determination, determined to be
0.7625
Results
AvascularHomogenous
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Summery In identifying and grading canine intervertebral disc degeneration,
Single fiber Reflectance Spectroscopy is performed
A needle-based single-fiber reflectance spectroscopy system that is compatible with PLDA procedure is constructed
SfRS measurements indicate increase of light scattering intensity across the entire 530 –100 nm spectral range in discs with mineralization
In grading disc mineral composition, SfRS showed a higher sensitivity and specificity than both X-ray radiography and computed tomography (CT)
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In identifying degenerated disc by varying threshold level, SfRS
showed a good classification with having area under ROC curve of
0.841
At high percentage of mineral volume (above 50%) confirmed by
histopatology imaages, due to higher number of scattering particle,
deposited mineral acts as a homogeneous medium and only accounts
for fresnel reflection while applying SfRS, thus SfRS could not provide
as good correlation as for less than 50% of mineral volume
Summery
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Acknowledgement Endowment to Bartels KE, Kerr Foundation, Oklahoma
city, OK
Oklahoma Center for the Advancement of Science and Technology (OCAST) HR 11-043