Download - OVERVIEW

1

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

2

OVERVIEW Background

Motivation and Objective

System configuration

Imaging protocols

Results

Summery

3

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

4

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

5

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

6

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 %

7

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

8

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

9

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

10

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

11

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

12

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

13

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°

14

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

15

Imaging protocol

16

Imaging protocol

extending~1mm

Reflectance spectroscop

y system

Acquisition time: 2 second/measurement-Step1: Measurements-Step2: PLDA procedure-Step3: Measurements

17

No mineral present on radiographs

L2-3, slight nuclear mineralization

L4-5, no nuclear mineralization

Results (Dog#1 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

19T10-11 mineralized


T10-11mineralized

T11-12mineralized

T12-13mineralized

T13-L1mineralized

L1-2mineralized

L2-3mineralized

L3-4mineralized

L4-5mineralized

20

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

21

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%)



L5-6 No mineralization No mineralization equivocal mineralization at edge of nuclear material surroundingdescribed focus of cavitation (10%)

Results (Dog1)

22

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)



multiple mineralized foci comprise approximately 40% of the nucleus



basophilic coagulum interpreted to be charred mineralized material composes approximately 70% of nucleus

L5-6 No mineralization


mineralized tissue composes approximately 50% of nucleus tissue present in section

23

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





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

24

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

25

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

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

26

Mineralized Normal

27

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

28

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

29

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

30

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

31

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)

32

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

33

Acknowledgement Endowment to Bartels KE, Kerr Foundation, Oklahoma

city, OK

Oklahoma Center for the Advancement of Science and Technology (OCAST) HR 11-043

Download - OVERVIEW

Top Related