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Single-fiber reflectance spectroscopy: Is it more accurate than radiography and computed tomography in identifying degenerated canine intervertebral discs?

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Presentation on theme: "Single-fiber reflectance spectroscopy: Is it more accurate than radiography and computed tomography in identifying degenerated canine intervertebral discs?"— Presentation transcript:

1 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 1 School of Electrical and Computer Engineering, Oklahoma State University, Stillwater, OK 74078, USA 2 Depertment of Veterinary Clinical Science, Oklahoma State University, Stillwater, OK 74078, USA 3 Depertment of Veterinary Pathobiology, Oklahoma State University, Stillwater, OK 74078, USA 4 Depertment of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21205, USA 1

2 OVERVIEW  Background  Motivation and Objective  System configuration  Imaging protocols  Results  Summery 2

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 3 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 4 Source: http://www.mayfieldclinic.com/PEHLDisc.htm#.Ujy34sakquM

5 Background Treatment  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 5 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 % 6

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 7

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 8 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 9 Source: http://www.mayfieldclinic.com/PE-HLDisc.htm#.Ujy7jsakquM http://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 10

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 11

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 12

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 needle 15 0 angle polished fiber in needle Schematic of Single fiber reflectance spectroscopy setup single fiber Bifurcated fiber bundle 13 15°

14 Analytical Representation 14 Raw Spectrum Normalized Spectrum

15 Imaging protocol 15

16 Imaging protocol 16 extending ~1mm Reflectance spectroscopy system Acquisition time: 2 second/measurement -Step1: Measurements -Step2: PLDA procedure -Step3: Measurements

17 17 No mineral present on radiographs L2-3, slight nuclear mineralization L4-5, no nuclear mineralization Results (Dog#1 Radiography and CT)

18 Results (Dog#2 Radiography and CT) T10-11 mineralized T11-12 mineralized L2-3 mineralized L3-4 mineralized T12-13 mineralized L1-2 mineralized L4-5 mineralized L5-6 mineralized T8-9 T12-12 L2-3 L3-4 L4-5 L7-S1 are mineralized in radiograph

19 19 T10-11 mineralized Results (Dog#3 Radiography and CT) T10-11 mineralized T11-12 mineralized T12-13 mineralized T13-L1 mineralized L1-2 mineralized L2-3 mineralized L3-4 mineralized L4-5 mineralized

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 20

21 disc No RadiographCTPathology T8-9No mineralization 2 small foci of light mineralization within nucleus (<10%) with equivocal mineralization at periphery of presumptive char tract T10-11No mineralization Slight focal mineral in nucleus No mineralization T11-12No mineralization Large central focus of dense mineralization (60%) in nucleus T12-13No mineralizationNone No mineralization T13-L1No mineralization 2 distinct foci of mineralization/bone within nucleus that composed approx. 35% of visible nucleus L1-2No mineralization L2-3No mineralization very focal mineral (nucleus) Focus of dense mineralization near center of nucleus (in chondroid tissue) (30%) L3-4No mineralization L4-5No mineralization L5-6No mineralization equivocal mineralization at edge of nuclear material surrounding described focus of cavitation (10%) Results (Dog1) 21

22 Results (Dog2) disc No RadiographCTPathology T10-11No mineralization rim mineralization of nucleus no mineralization on H&E T11-12No 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-L1No mineralization no distinct mineralization in visible nucleus L1-2No mineralization small amount of mineral no distinct mineralization in nucleus L2-3 small amount of mineral 2 small and equivocal foci of mineralization in nucleus (approximately 10% of nucleus) L3-4 small amount of mineral multiple mineralized foci comprise approximately 40% of the nucleus L4-5 small amount of mineral basophilic coagulum interpreted to be charred mineralized material composes approximately 70% of nucleus L5-6No mineralization small amount of mineral mineralized tissue composes approximately 50% of nucleus tissue present in section 22

23 Results (Dog3) disc No RadiographCTPathology T10-11mineralized large amount of mineral nearly all of the nucleus material on slide is VK+ (mineralized) T11-12no mineralization moderate mineral central nucleus 4 fairly large foci of mineralization in nucleus (approximately 40% of nucleus) T12-13no mineralization mineralized ventral aspect of nucleus large foci of mineralization in nucleus comprise about 50% of nucleus T13-L1no mineralization mineralized and ruptured nucleus large foci of mineralization in nucleus (40%) and annulus L1-2no mineralization small amount of focal mineral central focus of mineralization comprises approx. 20% of the nucleus L2-3no mineralization small amount of focal mineral central focus of mineralization comprises approx. 20% of the nucleus L3-4no mineralization small amount of focal mineral central focus of mineralization comprises approx. 18% of the nucleus L4-5no mineralizationvery slight focal mineral <5% of nucleus is equivocally mineralized L5-6no mineralizationNo mineralization central focus of mineralization comprises approx. 10% of the nucleus 23

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 24 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 25

26 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 27

28 28  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 Results 29

30 Results 30 Avascular Homogenous

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) 31

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 32 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 33


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