Abstract

Epidural catheters are used to deliver anesthetics and opioids for managing pain in many clinical scenarios. Currently, epidural catheter insertion is performed without information about the tissues that are directly ahead of the catheter. As a result, the catheter can be incorrectly positioned within a blood vessel, which can cause toxicity. Recent studies have shown that optical reflectance spectroscopy could be beneficial for guiding needles that are used to insert catheters. In this study, we investigate the whether this technique could benefit the placement of catheters within the epidural space. We present a novel optical epidural catheter with integrated polymer light guides that allows for optical spectra to be acquired from tissues at the distal tip. To obtain an initial indication of the information that could be obtained, reflectance values and photon penetration depth were estimated using Monte Carlo simulations, and optical reflectance spectra were acquired during a laminectomy of a swine ex vivo. Large differences between the spectra acquired from epidural adipose tissue and from venous blood were observed. The optical catheter has the potential to provide real-time detection of intravascular catheter placement that could reduce the risk of complications.

© 2013 Optical Society of America

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    [CrossRef] [PubMed]
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2012 (3)

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. van Kleef, M. Sommer, “Optical detection of peripheral nerves: An in vivo human study,” Reg. Anesth. Pain Med. 37(3), 277–282 (2012).
[CrossRef] [PubMed]

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. Sommer, M. van Kleef, “Optical Detection of Vascular Penetration During Nerve Blocks: An In Vivo Human Study,” Reg. Anesth. Pain Med. 37(1), 3–7 (2012).
[CrossRef] [PubMed]

S. P. Lin, M. S. Mandell, Y. Chang, P. T. Chen, M. Y. Tsou, K. H. Chan, C. K. Ting, “Discriminant analysis for anaesthetic decision-making: An intelligent recognition system for epidural needle insertion,” Br. J. Anaesth. 108(2), 302–307 (2012).
[CrossRef] [PubMed]

2011 (2)

M. Brynolf, M. Sommer, A. E. Desjardins, M. van der Voort, S. Roggeveen, W. Bierhoff, B. H. W. Hendriks, J. P. Rathmell, A. G. H. Kessels, M. Söderman, B. Holmström, “Optical detection of the brachial plexus for peripheral nerve blocks: An in vivo swine study,” Reg. Anesth. Pain Med. 36(4), 350–357 (2011).
[CrossRef] [PubMed]

A. E. Desjardins, B. H. W. Hendriks, M. van der Voort, R. Nachabé, W. Bierhoff, G. Braun, D. Babic, J. P. Rathmell, S. Holmin, M. Söderman, B. Holmström, “Epidural needle with embedded optical fibers for spectroscopic differentiation of tissue: Ex vivo feasibility study,” Biomed. Opt. Express 2(6), 1452–1461 (2011).
[CrossRef] [PubMed]

2010 (4)

J. Abbas, K. Hamoud, Y. M. Masharawi, H. May, O. Hay, B. Medlej, N. Peled, I. Hershkovitz, “Ligamentum flavum thickness in normal and stenotic lumbar spines,” Spine 35(12), 1225–1230 (2010).
[PubMed]

T. Fivez, S. Deblonde, M. Van de Velde, “Late intravascular migration of a previously well functioning labour epidural catheter,” Eur. J. Anaesthesiol. 27(7), 634–636 (2010).
[CrossRef] [PubMed]

C. K. Ting, M. Y. Tsou, P. T. Chen, K. Y. Chang, M. S. Mandell, K. H. Chan, Y. Chang, “A new technique to assist epidural needle placement: Fiberoptic-guided insertion using two wavelengths,” Anesthesiology 112(5), 1128–1135 (2010).
[CrossRef] [PubMed]

J. P. Rathmell, A. E. Desjardins, M. van der Voort, B. H. W. Hendriks, R. Nachabe, S. Roggeveen, D. Babic, M. Söderman, M. Brynolf, B. Holmström, “Identification of the epidural space with optical spectroscopy: An in vivo swine study,” Anesthesiology 113(6), 1406–1418 (2010).
[CrossRef] [PubMed]

2007 (1)

M. Meinke, G. Müller, J. Helfmann, M. Friebel, “Optical properties of platelets and blood plasma and their influence on the optical behavior of whole blood in the visible to near infrared wavelength range,” J. Biomed. Opt. 12(1), 014024 (2007).
[CrossRef] [PubMed]

2006 (4)

D. Arifler, C. MacAulay, M. Follen, R. Richards-Kortum, “Spatially resolved reflectance spectroscopy for diagnosis of cervical precancer: Monte Carlo modeling and comparison to clinical measurements,” J. Biomed. Opt. 11(6), 064027 (2006).
[CrossRef] [PubMed]

J. Guay, “The epidural test dose: A review,” Anesth. Analg. 102(3), 921–929 (2006).
[CrossRef] [PubMed]

M. A. Reina, P. Pulido, J. Castedo, M. C. Villanueva, A. López, R. G. Sola, “Characteristics and distribution of normal human epidural fat,” Rev. Esp. Anestesiol. Reanim. 53(6), 363–372 (2006).
[PubMed]

M. Friebel, A. Roggan, G. Müller, M. Meinke, “Determination of optical properties of human blood in the spectral range 250 to 1100 nm using Monte Carlo simulations with hematocrit-dependent effective scattering phase functions,” J. Biomed. Opt. 11(3), 034021 (2006).
[CrossRef] [PubMed]

2005 (1)

A. N. Bashkatov, E. A. Genina, V. I. Kochubey, V. V. Tuchin, “Optical properties of human skin, subcutaneous and mucous tissues in the wavelength range from 400 to 2000 nm,” J. Phys. D Appl. Phys. 38(15), 2543–2555 (2005).
[CrossRef]

2003 (1)

U. Utzinger, R. R. Richards-Kortum, “Fiber optic probes for biomedical optical spectroscopy,” J. Biomed. Opt. 8(1), 121–147 (2003).
[CrossRef] [PubMed]

2001 (2)

J. Zubia, J. Arrue, “Plastic optical fibers: An introduction to their technological processes and applications,” Opt. Fiber Technol. 7(2), 101–140 (2001).
[CrossRef]

S. M. Burns, C. M. Cowa, P. M. Barclay, R. G. Wilkes, “Intrapartum epidural catheter migration: A comparative study of three dressing applications,” Br. J. Anaesth. 86(4), 565–567 (2001).
[CrossRef] [PubMed]

1999 (1)

M. A. Reina, A. López García, J. A. de Andrés, F. Sellers, M. Arrizabalaga, M. J. Mora, “Variation in the thickness of the dural sac,” Rev. Esp. Anestesiol. Reanim. 46(8), 344–349 (1999).
[PubMed]

1989 (1)

S. A. Prahl, M. Keijzer, S. L. Jacques, A. J. Welch, “A Monte Carlo model of light propagation in tissue,” SPIE Institute Series. IS5, 102–111 (1989).

Abbas, J.

J. Abbas, K. Hamoud, Y. M. Masharawi, H. May, O. Hay, B. Medlej, N. Peled, I. Hershkovitz, “Ligamentum flavum thickness in normal and stenotic lumbar spines,” Spine 35(12), 1225–1230 (2010).
[PubMed]

Arifler, D.

D. Arifler, C. MacAulay, M. Follen, R. Richards-Kortum, “Spatially resolved reflectance spectroscopy for diagnosis of cervical precancer: Monte Carlo modeling and comparison to clinical measurements,” J. Biomed. Opt. 11(6), 064027 (2006).
[CrossRef] [PubMed]

Arrizabalaga, M.

M. A. Reina, A. López García, J. A. de Andrés, F. Sellers, M. Arrizabalaga, M. J. Mora, “Variation in the thickness of the dural sac,” Rev. Esp. Anestesiol. Reanim. 46(8), 344–349 (1999).
[PubMed]

Arrue, J.

J. Zubia, J. Arrue, “Plastic optical fibers: An introduction to their technological processes and applications,” Opt. Fiber Technol. 7(2), 101–140 (2001).
[CrossRef]

Babic, D.

A. E. Desjardins, B. H. W. Hendriks, M. van der Voort, R. Nachabé, W. Bierhoff, G. Braun, D. Babic, J. P. Rathmell, S. Holmin, M. Söderman, B. Holmström, “Epidural needle with embedded optical fibers for spectroscopic differentiation of tissue: Ex vivo feasibility study,” Biomed. Opt. Express 2(6), 1452–1461 (2011).
[CrossRef] [PubMed]

J. P. Rathmell, A. E. Desjardins, M. van der Voort, B. H. W. Hendriks, R. Nachabe, S. Roggeveen, D. Babic, M. Söderman, M. Brynolf, B. Holmström, “Identification of the epidural space with optical spectroscopy: An in vivo swine study,” Anesthesiology 113(6), 1406–1418 (2010).
[CrossRef] [PubMed]

Balthasar, A.

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. van Kleef, M. Sommer, “Optical detection of peripheral nerves: An in vivo human study,” Reg. Anesth. Pain Med. 37(3), 277–282 (2012).
[CrossRef] [PubMed]

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. Sommer, M. van Kleef, “Optical Detection of Vascular Penetration During Nerve Blocks: An In Vivo Human Study,” Reg. Anesth. Pain Med. 37(1), 3–7 (2012).
[CrossRef] [PubMed]

Barclay, P. M.

S. M. Burns, C. M. Cowa, P. M. Barclay, R. G. Wilkes, “Intrapartum epidural catheter migration: A comparative study of three dressing applications,” Br. J. Anaesth. 86(4), 565–567 (2001).
[CrossRef] [PubMed]

Bashkatov, A. N.

A. N. Bashkatov, E. A. Genina, V. I. Kochubey, V. V. Tuchin, “Optical properties of human skin, subcutaneous and mucous tissues in the wavelength range from 400 to 2000 nm,” J. Phys. D Appl. Phys. 38(15), 2543–2555 (2005).
[CrossRef]

Bierhoff, W.

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. Sommer, M. van Kleef, “Optical Detection of Vascular Penetration During Nerve Blocks: An In Vivo Human Study,” Reg. Anesth. Pain Med. 37(1), 3–7 (2012).
[CrossRef] [PubMed]

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. van Kleef, M. Sommer, “Optical detection of peripheral nerves: An in vivo human study,” Reg. Anesth. Pain Med. 37(3), 277–282 (2012).
[CrossRef] [PubMed]

A. E. Desjardins, B. H. W. Hendriks, M. van der Voort, R. Nachabé, W. Bierhoff, G. Braun, D. Babic, J. P. Rathmell, S. Holmin, M. Söderman, B. Holmström, “Epidural needle with embedded optical fibers for spectroscopic differentiation of tissue: Ex vivo feasibility study,” Biomed. Opt. Express 2(6), 1452–1461 (2011).
[CrossRef] [PubMed]

M. Brynolf, M. Sommer, A. E. Desjardins, M. van der Voort, S. Roggeveen, W. Bierhoff, B. H. W. Hendriks, J. P. Rathmell, A. G. H. Kessels, M. Söderman, B. Holmström, “Optical detection of the brachial plexus for peripheral nerve blocks: An in vivo swine study,” Reg. Anesth. Pain Med. 36(4), 350–357 (2011).
[CrossRef] [PubMed]

Braun, G.

Brynolf, M.

M. Brynolf, M. Sommer, A. E. Desjardins, M. van der Voort, S. Roggeveen, W. Bierhoff, B. H. W. Hendriks, J. P. Rathmell, A. G. H. Kessels, M. Söderman, B. Holmström, “Optical detection of the brachial plexus for peripheral nerve blocks: An in vivo swine study,” Reg. Anesth. Pain Med. 36(4), 350–357 (2011).
[CrossRef] [PubMed]

J. P. Rathmell, A. E. Desjardins, M. van der Voort, B. H. W. Hendriks, R. Nachabe, S. Roggeveen, D. Babic, M. Söderman, M. Brynolf, B. Holmström, “Identification of the epidural space with optical spectroscopy: An in vivo swine study,” Anesthesiology 113(6), 1406–1418 (2010).
[CrossRef] [PubMed]

Burns, S. M.

S. M. Burns, C. M. Cowa, P. M. Barclay, R. G. Wilkes, “Intrapartum epidural catheter migration: A comparative study of three dressing applications,” Br. J. Anaesth. 86(4), 565–567 (2001).
[CrossRef] [PubMed]

Castedo, J.

M. A. Reina, P. Pulido, J. Castedo, M. C. Villanueva, A. López, R. G. Sola, “Characteristics and distribution of normal human epidural fat,” Rev. Esp. Anestesiol. Reanim. 53(6), 363–372 (2006).
[PubMed]

Chan, K. H.

S. P. Lin, M. S. Mandell, Y. Chang, P. T. Chen, M. Y. Tsou, K. H. Chan, C. K. Ting, “Discriminant analysis for anaesthetic decision-making: An intelligent recognition system for epidural needle insertion,” Br. J. Anaesth. 108(2), 302–307 (2012).
[CrossRef] [PubMed]

C. K. Ting, M. Y. Tsou, P. T. Chen, K. Y. Chang, M. S. Mandell, K. H. Chan, Y. Chang, “A new technique to assist epidural needle placement: Fiberoptic-guided insertion using two wavelengths,” Anesthesiology 112(5), 1128–1135 (2010).
[CrossRef] [PubMed]

Chang, K. Y.

C. K. Ting, M. Y. Tsou, P. T. Chen, K. Y. Chang, M. S. Mandell, K. H. Chan, Y. Chang, “A new technique to assist epidural needle placement: Fiberoptic-guided insertion using two wavelengths,” Anesthesiology 112(5), 1128–1135 (2010).
[CrossRef] [PubMed]

Chang, Y.

S. P. Lin, M. S. Mandell, Y. Chang, P. T. Chen, M. Y. Tsou, K. H. Chan, C. K. Ting, “Discriminant analysis for anaesthetic decision-making: An intelligent recognition system for epidural needle insertion,” Br. J. Anaesth. 108(2), 302–307 (2012).
[CrossRef] [PubMed]

C. K. Ting, M. Y. Tsou, P. T. Chen, K. Y. Chang, M. S. Mandell, K. H. Chan, Y. Chang, “A new technique to assist epidural needle placement: Fiberoptic-guided insertion using two wavelengths,” Anesthesiology 112(5), 1128–1135 (2010).
[CrossRef] [PubMed]

Chen, P. T.

S. P. Lin, M. S. Mandell, Y. Chang, P. T. Chen, M. Y. Tsou, K. H. Chan, C. K. Ting, “Discriminant analysis for anaesthetic decision-making: An intelligent recognition system for epidural needle insertion,” Br. J. Anaesth. 108(2), 302–307 (2012).
[CrossRef] [PubMed]

C. K. Ting, M. Y. Tsou, P. T. Chen, K. Y. Chang, M. S. Mandell, K. H. Chan, Y. Chang, “A new technique to assist epidural needle placement: Fiberoptic-guided insertion using two wavelengths,” Anesthesiology 112(5), 1128–1135 (2010).
[CrossRef] [PubMed]

Cowa, C. M.

S. M. Burns, C. M. Cowa, P. M. Barclay, R. G. Wilkes, “Intrapartum epidural catheter migration: A comparative study of three dressing applications,” Br. J. Anaesth. 86(4), 565–567 (2001).
[CrossRef] [PubMed]

de Andrés, J. A.

M. A. Reina, A. López García, J. A. de Andrés, F. Sellers, M. Arrizabalaga, M. J. Mora, “Variation in the thickness of the dural sac,” Rev. Esp. Anestesiol. Reanim. 46(8), 344–349 (1999).
[PubMed]

Deblonde, S.

T. Fivez, S. Deblonde, M. Van de Velde, “Late intravascular migration of a previously well functioning labour epidural catheter,” Eur. J. Anaesthesiol. 27(7), 634–636 (2010).
[CrossRef] [PubMed]

Desjardins, A. E.

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. van Kleef, M. Sommer, “Optical detection of peripheral nerves: An in vivo human study,” Reg. Anesth. Pain Med. 37(3), 277–282 (2012).
[CrossRef] [PubMed]

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. Sommer, M. van Kleef, “Optical Detection of Vascular Penetration During Nerve Blocks: An In Vivo Human Study,” Reg. Anesth. Pain Med. 37(1), 3–7 (2012).
[CrossRef] [PubMed]

A. E. Desjardins, B. H. W. Hendriks, M. van der Voort, R. Nachabé, W. Bierhoff, G. Braun, D. Babic, J. P. Rathmell, S. Holmin, M. Söderman, B. Holmström, “Epidural needle with embedded optical fibers for spectroscopic differentiation of tissue: Ex vivo feasibility study,” Biomed. Opt. Express 2(6), 1452–1461 (2011).
[CrossRef] [PubMed]

M. Brynolf, M. Sommer, A. E. Desjardins, M. van der Voort, S. Roggeveen, W. Bierhoff, B. H. W. Hendriks, J. P. Rathmell, A. G. H. Kessels, M. Söderman, B. Holmström, “Optical detection of the brachial plexus for peripheral nerve blocks: An in vivo swine study,” Reg. Anesth. Pain Med. 36(4), 350–357 (2011).
[CrossRef] [PubMed]

J. P. Rathmell, A. E. Desjardins, M. van der Voort, B. H. W. Hendriks, R. Nachabe, S. Roggeveen, D. Babic, M. Söderman, M. Brynolf, B. Holmström, “Identification of the epidural space with optical spectroscopy: An in vivo swine study,” Anesthesiology 113(6), 1406–1418 (2010).
[CrossRef] [PubMed]

Fivez, T.

T. Fivez, S. Deblonde, M. Van de Velde, “Late intravascular migration of a previously well functioning labour epidural catheter,” Eur. J. Anaesthesiol. 27(7), 634–636 (2010).
[CrossRef] [PubMed]

Follen, M.

D. Arifler, C. MacAulay, M. Follen, R. Richards-Kortum, “Spatially resolved reflectance spectroscopy for diagnosis of cervical precancer: Monte Carlo modeling and comparison to clinical measurements,” J. Biomed. Opt. 11(6), 064027 (2006).
[CrossRef] [PubMed]

Friebel, M.

M. Meinke, G. Müller, J. Helfmann, M. Friebel, “Optical properties of platelets and blood plasma and their influence on the optical behavior of whole blood in the visible to near infrared wavelength range,” J. Biomed. Opt. 12(1), 014024 (2007).
[CrossRef] [PubMed]

M. Friebel, A. Roggan, G. Müller, M. Meinke, “Determination of optical properties of human blood in the spectral range 250 to 1100 nm using Monte Carlo simulations with hematocrit-dependent effective scattering phase functions,” J. Biomed. Opt. 11(3), 034021 (2006).
[CrossRef] [PubMed]

Genina, E. A.

A. N. Bashkatov, E. A. Genina, V. I. Kochubey, V. V. Tuchin, “Optical properties of human skin, subcutaneous and mucous tissues in the wavelength range from 400 to 2000 nm,” J. Phys. D Appl. Phys. 38(15), 2543–2555 (2005).
[CrossRef]

Guay, J.

J. Guay, “The epidural test dose: A review,” Anesth. Analg. 102(3), 921–929 (2006).
[CrossRef] [PubMed]

Hamoud, K.

J. Abbas, K. Hamoud, Y. M. Masharawi, H. May, O. Hay, B. Medlej, N. Peled, I. Hershkovitz, “Ligamentum flavum thickness in normal and stenotic lumbar spines,” Spine 35(12), 1225–1230 (2010).
[PubMed]

Hay, O.

J. Abbas, K. Hamoud, Y. M. Masharawi, H. May, O. Hay, B. Medlej, N. Peled, I. Hershkovitz, “Ligamentum flavum thickness in normal and stenotic lumbar spines,” Spine 35(12), 1225–1230 (2010).
[PubMed]

Helfmann, J.

M. Meinke, G. Müller, J. Helfmann, M. Friebel, “Optical properties of platelets and blood plasma and their influence on the optical behavior of whole blood in the visible to near infrared wavelength range,” J. Biomed. Opt. 12(1), 014024 (2007).
[CrossRef] [PubMed]

Hendriks, B. H. W.

A. E. Desjardins, B. H. W. Hendriks, M. van der Voort, R. Nachabé, W. Bierhoff, G. Braun, D. Babic, J. P. Rathmell, S. Holmin, M. Söderman, B. Holmström, “Epidural needle with embedded optical fibers for spectroscopic differentiation of tissue: Ex vivo feasibility study,” Biomed. Opt. Express 2(6), 1452–1461 (2011).
[CrossRef] [PubMed]

M. Brynolf, M. Sommer, A. E. Desjardins, M. van der Voort, S. Roggeveen, W. Bierhoff, B. H. W. Hendriks, J. P. Rathmell, A. G. H. Kessels, M. Söderman, B. Holmström, “Optical detection of the brachial plexus for peripheral nerve blocks: An in vivo swine study,” Reg. Anesth. Pain Med. 36(4), 350–357 (2011).
[CrossRef] [PubMed]

J. P. Rathmell, A. E. Desjardins, M. van der Voort, B. H. W. Hendriks, R. Nachabe, S. Roggeveen, D. Babic, M. Söderman, M. Brynolf, B. Holmström, “Identification of the epidural space with optical spectroscopy: An in vivo swine study,” Anesthesiology 113(6), 1406–1418 (2010).
[CrossRef] [PubMed]

Hershkovitz, I.

J. Abbas, K. Hamoud, Y. M. Masharawi, H. May, O. Hay, B. Medlej, N. Peled, I. Hershkovitz, “Ligamentum flavum thickness in normal and stenotic lumbar spines,” Spine 35(12), 1225–1230 (2010).
[PubMed]

Holmin, S.

Holmström, B.

A. E. Desjardins, B. H. W. Hendriks, M. van der Voort, R. Nachabé, W. Bierhoff, G. Braun, D. Babic, J. P. Rathmell, S. Holmin, M. Söderman, B. Holmström, “Epidural needle with embedded optical fibers for spectroscopic differentiation of tissue: Ex vivo feasibility study,” Biomed. Opt. Express 2(6), 1452–1461 (2011).
[CrossRef] [PubMed]

M. Brynolf, M. Sommer, A. E. Desjardins, M. van der Voort, S. Roggeveen, W. Bierhoff, B. H. W. Hendriks, J. P. Rathmell, A. G. H. Kessels, M. Söderman, B. Holmström, “Optical detection of the brachial plexus for peripheral nerve blocks: An in vivo swine study,” Reg. Anesth. Pain Med. 36(4), 350–357 (2011).
[CrossRef] [PubMed]

J. P. Rathmell, A. E. Desjardins, M. van der Voort, B. H. W. Hendriks, R. Nachabe, S. Roggeveen, D. Babic, M. Söderman, M. Brynolf, B. Holmström, “Identification of the epidural space with optical spectroscopy: An in vivo swine study,” Anesthesiology 113(6), 1406–1418 (2010).
[CrossRef] [PubMed]

Jacques, S. L.

S. A. Prahl, M. Keijzer, S. L. Jacques, A. J. Welch, “A Monte Carlo model of light propagation in tissue,” SPIE Institute Series. IS5, 102–111 (1989).

Keijzer, M.

S. A. Prahl, M. Keijzer, S. L. Jacques, A. J. Welch, “A Monte Carlo model of light propagation in tissue,” SPIE Institute Series. IS5, 102–111 (1989).

Kessels, A. G. H.

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. van Kleef, M. Sommer, “Optical detection of peripheral nerves: An in vivo human study,” Reg. Anesth. Pain Med. 37(3), 277–282 (2012).
[CrossRef] [PubMed]

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. Sommer, M. van Kleef, “Optical Detection of Vascular Penetration During Nerve Blocks: An In Vivo Human Study,” Reg. Anesth. Pain Med. 37(1), 3–7 (2012).
[CrossRef] [PubMed]

M. Brynolf, M. Sommer, A. E. Desjardins, M. van der Voort, S. Roggeveen, W. Bierhoff, B. H. W. Hendriks, J. P. Rathmell, A. G. H. Kessels, M. Söderman, B. Holmström, “Optical detection of the brachial plexus for peripheral nerve blocks: An in vivo swine study,” Reg. Anesth. Pain Med. 36(4), 350–357 (2011).
[CrossRef] [PubMed]

Kochubey, V. I.

A. N. Bashkatov, E. A. Genina, V. I. Kochubey, V. V. Tuchin, “Optical properties of human skin, subcutaneous and mucous tissues in the wavelength range from 400 to 2000 nm,” J. Phys. D Appl. Phys. 38(15), 2543–2555 (2005).
[CrossRef]

Lin, S. P.

S. P. Lin, M. S. Mandell, Y. Chang, P. T. Chen, M. Y. Tsou, K. H. Chan, C. K. Ting, “Discriminant analysis for anaesthetic decision-making: An intelligent recognition system for epidural needle insertion,” Br. J. Anaesth. 108(2), 302–307 (2012).
[CrossRef] [PubMed]

López, A.

M. A. Reina, P. Pulido, J. Castedo, M. C. Villanueva, A. López, R. G. Sola, “Characteristics and distribution of normal human epidural fat,” Rev. Esp. Anestesiol. Reanim. 53(6), 363–372 (2006).
[PubMed]

López García, A.

M. A. Reina, A. López García, J. A. de Andrés, F. Sellers, M. Arrizabalaga, M. J. Mora, “Variation in the thickness of the dural sac,” Rev. Esp. Anestesiol. Reanim. 46(8), 344–349 (1999).
[PubMed]

Lucassen, G. W.

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. Sommer, M. van Kleef, “Optical Detection of Vascular Penetration During Nerve Blocks: An In Vivo Human Study,” Reg. Anesth. Pain Med. 37(1), 3–7 (2012).
[CrossRef] [PubMed]

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. van Kleef, M. Sommer, “Optical detection of peripheral nerves: An in vivo human study,” Reg. Anesth. Pain Med. 37(3), 277–282 (2012).
[CrossRef] [PubMed]

MacAulay, C.

D. Arifler, C. MacAulay, M. Follen, R. Richards-Kortum, “Spatially resolved reflectance spectroscopy for diagnosis of cervical precancer: Monte Carlo modeling and comparison to clinical measurements,” J. Biomed. Opt. 11(6), 064027 (2006).
[CrossRef] [PubMed]

Mandell, M. S.

S. P. Lin, M. S. Mandell, Y. Chang, P. T. Chen, M. Y. Tsou, K. H. Chan, C. K. Ting, “Discriminant analysis for anaesthetic decision-making: An intelligent recognition system for epidural needle insertion,” Br. J. Anaesth. 108(2), 302–307 (2012).
[CrossRef] [PubMed]

C. K. Ting, M. Y. Tsou, P. T. Chen, K. Y. Chang, M. S. Mandell, K. H. Chan, Y. Chang, “A new technique to assist epidural needle placement: Fiberoptic-guided insertion using two wavelengths,” Anesthesiology 112(5), 1128–1135 (2010).
[CrossRef] [PubMed]

Masharawi, Y. M.

J. Abbas, K. Hamoud, Y. M. Masharawi, H. May, O. Hay, B. Medlej, N. Peled, I. Hershkovitz, “Ligamentum flavum thickness in normal and stenotic lumbar spines,” Spine 35(12), 1225–1230 (2010).
[PubMed]

May, H.

J. Abbas, K. Hamoud, Y. M. Masharawi, H. May, O. Hay, B. Medlej, N. Peled, I. Hershkovitz, “Ligamentum flavum thickness in normal and stenotic lumbar spines,” Spine 35(12), 1225–1230 (2010).
[PubMed]

Medlej, B.

J. Abbas, K. Hamoud, Y. M. Masharawi, H. May, O. Hay, B. Medlej, N. Peled, I. Hershkovitz, “Ligamentum flavum thickness in normal and stenotic lumbar spines,” Spine 35(12), 1225–1230 (2010).
[PubMed]

Meinke, M.

M. Meinke, G. Müller, J. Helfmann, M. Friebel, “Optical properties of platelets and blood plasma and their influence on the optical behavior of whole blood in the visible to near infrared wavelength range,” J. Biomed. Opt. 12(1), 014024 (2007).
[CrossRef] [PubMed]

M. Friebel, A. Roggan, G. Müller, M. Meinke, “Determination of optical properties of human blood in the spectral range 250 to 1100 nm using Monte Carlo simulations with hematocrit-dependent effective scattering phase functions,” J. Biomed. Opt. 11(3), 034021 (2006).
[CrossRef] [PubMed]

Mora, M. J.

M. A. Reina, A. López García, J. A. de Andrés, F. Sellers, M. Arrizabalaga, M. J. Mora, “Variation in the thickness of the dural sac,” Rev. Esp. Anestesiol. Reanim. 46(8), 344–349 (1999).
[PubMed]

Müller, G.

M. Meinke, G. Müller, J. Helfmann, M. Friebel, “Optical properties of platelets and blood plasma and their influence on the optical behavior of whole blood in the visible to near infrared wavelength range,” J. Biomed. Opt. 12(1), 014024 (2007).
[CrossRef] [PubMed]

M. Friebel, A. Roggan, G. Müller, M. Meinke, “Determination of optical properties of human blood in the spectral range 250 to 1100 nm using Monte Carlo simulations with hematocrit-dependent effective scattering phase functions,” J. Biomed. Opt. 11(3), 034021 (2006).
[CrossRef] [PubMed]

Nachabe, R.

J. P. Rathmell, A. E. Desjardins, M. van der Voort, B. H. W. Hendriks, R. Nachabe, S. Roggeveen, D. Babic, M. Söderman, M. Brynolf, B. Holmström, “Identification of the epidural space with optical spectroscopy: An in vivo swine study,” Anesthesiology 113(6), 1406–1418 (2010).
[CrossRef] [PubMed]

Nachabé, R.

Peled, N.

J. Abbas, K. Hamoud, Y. M. Masharawi, H. May, O. Hay, B. Medlej, N. Peled, I. Hershkovitz, “Ligamentum flavum thickness in normal and stenotic lumbar spines,” Spine 35(12), 1225–1230 (2010).
[PubMed]

Prahl, S. A.

S. A. Prahl, M. Keijzer, S. L. Jacques, A. J. Welch, “A Monte Carlo model of light propagation in tissue,” SPIE Institute Series. IS5, 102–111 (1989).

Pulido, P.

M. A. Reina, P. Pulido, J. Castedo, M. C. Villanueva, A. López, R. G. Sola, “Characteristics and distribution of normal human epidural fat,” Rev. Esp. Anestesiol. Reanim. 53(6), 363–372 (2006).
[PubMed]

Rathmell, J. P.

A. E. Desjardins, B. H. W. Hendriks, M. van der Voort, R. Nachabé, W. Bierhoff, G. Braun, D. Babic, J. P. Rathmell, S. Holmin, M. Söderman, B. Holmström, “Epidural needle with embedded optical fibers for spectroscopic differentiation of tissue: Ex vivo feasibility study,” Biomed. Opt. Express 2(6), 1452–1461 (2011).
[CrossRef] [PubMed]

M. Brynolf, M. Sommer, A. E. Desjardins, M. van der Voort, S. Roggeveen, W. Bierhoff, B. H. W. Hendriks, J. P. Rathmell, A. G. H. Kessels, M. Söderman, B. Holmström, “Optical detection of the brachial plexus for peripheral nerve blocks: An in vivo swine study,” Reg. Anesth. Pain Med. 36(4), 350–357 (2011).
[CrossRef] [PubMed]

J. P. Rathmell, A. E. Desjardins, M. van der Voort, B. H. W. Hendriks, R. Nachabe, S. Roggeveen, D. Babic, M. Söderman, M. Brynolf, B. Holmström, “Identification of the epidural space with optical spectroscopy: An in vivo swine study,” Anesthesiology 113(6), 1406–1418 (2010).
[CrossRef] [PubMed]

Reina, M. A.

M. A. Reina, P. Pulido, J. Castedo, M. C. Villanueva, A. López, R. G. Sola, “Characteristics and distribution of normal human epidural fat,” Rev. Esp. Anestesiol. Reanim. 53(6), 363–372 (2006).
[PubMed]

M. A. Reina, A. López García, J. A. de Andrés, F. Sellers, M. Arrizabalaga, M. J. Mora, “Variation in the thickness of the dural sac,” Rev. Esp. Anestesiol. Reanim. 46(8), 344–349 (1999).
[PubMed]

Richards-Kortum, R.

D. Arifler, C. MacAulay, M. Follen, R. Richards-Kortum, “Spatially resolved reflectance spectroscopy for diagnosis of cervical precancer: Monte Carlo modeling and comparison to clinical measurements,” J. Biomed. Opt. 11(6), 064027 (2006).
[CrossRef] [PubMed]

Richards-Kortum, R. R.

U. Utzinger, R. R. Richards-Kortum, “Fiber optic probes for biomedical optical spectroscopy,” J. Biomed. Opt. 8(1), 121–147 (2003).
[CrossRef] [PubMed]

Roggan, A.

M. Friebel, A. Roggan, G. Müller, M. Meinke, “Determination of optical properties of human blood in the spectral range 250 to 1100 nm using Monte Carlo simulations with hematocrit-dependent effective scattering phase functions,” J. Biomed. Opt. 11(3), 034021 (2006).
[CrossRef] [PubMed]

Roggeveen, S.

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. van Kleef, M. Sommer, “Optical detection of peripheral nerves: An in vivo human study,” Reg. Anesth. Pain Med. 37(3), 277–282 (2012).
[CrossRef] [PubMed]

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. Sommer, M. van Kleef, “Optical Detection of Vascular Penetration During Nerve Blocks: An In Vivo Human Study,” Reg. Anesth. Pain Med. 37(1), 3–7 (2012).
[CrossRef] [PubMed]

M. Brynolf, M. Sommer, A. E. Desjardins, M. van der Voort, S. Roggeveen, W. Bierhoff, B. H. W. Hendriks, J. P. Rathmell, A. G. H. Kessels, M. Söderman, B. Holmström, “Optical detection of the brachial plexus for peripheral nerve blocks: An in vivo swine study,” Reg. Anesth. Pain Med. 36(4), 350–357 (2011).
[CrossRef] [PubMed]

J. P. Rathmell, A. E. Desjardins, M. van der Voort, B. H. W. Hendriks, R. Nachabe, S. Roggeveen, D. Babic, M. Söderman, M. Brynolf, B. Holmström, “Identification of the epidural space with optical spectroscopy: An in vivo swine study,” Anesthesiology 113(6), 1406–1418 (2010).
[CrossRef] [PubMed]

Sellers, F.

M. A. Reina, A. López García, J. A. de Andrés, F. Sellers, M. Arrizabalaga, M. J. Mora, “Variation in the thickness of the dural sac,” Rev. Esp. Anestesiol. Reanim. 46(8), 344–349 (1999).
[PubMed]

Söderman, M.

M. Brynolf, M. Sommer, A. E. Desjardins, M. van der Voort, S. Roggeveen, W. Bierhoff, B. H. W. Hendriks, J. P. Rathmell, A. G. H. Kessels, M. Söderman, B. Holmström, “Optical detection of the brachial plexus for peripheral nerve blocks: An in vivo swine study,” Reg. Anesth. Pain Med. 36(4), 350–357 (2011).
[CrossRef] [PubMed]

A. E. Desjardins, B. H. W. Hendriks, M. van der Voort, R. Nachabé, W. Bierhoff, G. Braun, D. Babic, J. P. Rathmell, S. Holmin, M. Söderman, B. Holmström, “Epidural needle with embedded optical fibers for spectroscopic differentiation of tissue: Ex vivo feasibility study,” Biomed. Opt. Express 2(6), 1452–1461 (2011).
[CrossRef] [PubMed]

J. P. Rathmell, A. E. Desjardins, M. van der Voort, B. H. W. Hendriks, R. Nachabe, S. Roggeveen, D. Babic, M. Söderman, M. Brynolf, B. Holmström, “Identification of the epidural space with optical spectroscopy: An in vivo swine study,” Anesthesiology 113(6), 1406–1418 (2010).
[CrossRef] [PubMed]

Sola, R. G.

M. A. Reina, P. Pulido, J. Castedo, M. C. Villanueva, A. López, R. G. Sola, “Characteristics and distribution of normal human epidural fat,” Rev. Esp. Anestesiol. Reanim. 53(6), 363–372 (2006).
[PubMed]

Sommer, M.

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. Sommer, M. van Kleef, “Optical Detection of Vascular Penetration During Nerve Blocks: An In Vivo Human Study,” Reg. Anesth. Pain Med. 37(1), 3–7 (2012).
[CrossRef] [PubMed]

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. van Kleef, M. Sommer, “Optical detection of peripheral nerves: An in vivo human study,” Reg. Anesth. Pain Med. 37(3), 277–282 (2012).
[CrossRef] [PubMed]

M. Brynolf, M. Sommer, A. E. Desjardins, M. van der Voort, S. Roggeveen, W. Bierhoff, B. H. W. Hendriks, J. P. Rathmell, A. G. H. Kessels, M. Söderman, B. Holmström, “Optical detection of the brachial plexus for peripheral nerve blocks: An in vivo swine study,” Reg. Anesth. Pain Med. 36(4), 350–357 (2011).
[CrossRef] [PubMed]

Ting, C. K.

S. P. Lin, M. S. Mandell, Y. Chang, P. T. Chen, M. Y. Tsou, K. H. Chan, C. K. Ting, “Discriminant analysis for anaesthetic decision-making: An intelligent recognition system for epidural needle insertion,” Br. J. Anaesth. 108(2), 302–307 (2012).
[CrossRef] [PubMed]

C. K. Ting, M. Y. Tsou, P. T. Chen, K. Y. Chang, M. S. Mandell, K. H. Chan, Y. Chang, “A new technique to assist epidural needle placement: Fiberoptic-guided insertion using two wavelengths,” Anesthesiology 112(5), 1128–1135 (2010).
[CrossRef] [PubMed]

Tsou, M. Y.

S. P. Lin, M. S. Mandell, Y. Chang, P. T. Chen, M. Y. Tsou, K. H. Chan, C. K. Ting, “Discriminant analysis for anaesthetic decision-making: An intelligent recognition system for epidural needle insertion,” Br. J. Anaesth. 108(2), 302–307 (2012).
[CrossRef] [PubMed]

C. K. Ting, M. Y. Tsou, P. T. Chen, K. Y. Chang, M. S. Mandell, K. H. Chan, Y. Chang, “A new technique to assist epidural needle placement: Fiberoptic-guided insertion using two wavelengths,” Anesthesiology 112(5), 1128–1135 (2010).
[CrossRef] [PubMed]

Tuchin, V. V.

A. N. Bashkatov, E. A. Genina, V. I. Kochubey, V. V. Tuchin, “Optical properties of human skin, subcutaneous and mucous tissues in the wavelength range from 400 to 2000 nm,” J. Phys. D Appl. Phys. 38(15), 2543–2555 (2005).
[CrossRef]

Utzinger, U.

U. Utzinger, R. R. Richards-Kortum, “Fiber optic probes for biomedical optical spectroscopy,” J. Biomed. Opt. 8(1), 121–147 (2003).
[CrossRef] [PubMed]

Van de Velde, M.

T. Fivez, S. Deblonde, M. Van de Velde, “Late intravascular migration of a previously well functioning labour epidural catheter,” Eur. J. Anaesthesiol. 27(7), 634–636 (2010).
[CrossRef] [PubMed]

van der Voort, M.

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. Sommer, M. van Kleef, “Optical Detection of Vascular Penetration During Nerve Blocks: An In Vivo Human Study,” Reg. Anesth. Pain Med. 37(1), 3–7 (2012).
[CrossRef] [PubMed]

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. van Kleef, M. Sommer, “Optical detection of peripheral nerves: An in vivo human study,” Reg. Anesth. Pain Med. 37(3), 277–282 (2012).
[CrossRef] [PubMed]

M. Brynolf, M. Sommer, A. E. Desjardins, M. van der Voort, S. Roggeveen, W. Bierhoff, B. H. W. Hendriks, J. P. Rathmell, A. G. H. Kessels, M. Söderman, B. Holmström, “Optical detection of the brachial plexus for peripheral nerve blocks: An in vivo swine study,” Reg. Anesth. Pain Med. 36(4), 350–357 (2011).
[CrossRef] [PubMed]

A. E. Desjardins, B. H. W. Hendriks, M. van der Voort, R. Nachabé, W. Bierhoff, G. Braun, D. Babic, J. P. Rathmell, S. Holmin, M. Söderman, B. Holmström, “Epidural needle with embedded optical fibers for spectroscopic differentiation of tissue: Ex vivo feasibility study,” Biomed. Opt. Express 2(6), 1452–1461 (2011).
[CrossRef] [PubMed]

J. P. Rathmell, A. E. Desjardins, M. van der Voort, B. H. W. Hendriks, R. Nachabe, S. Roggeveen, D. Babic, M. Söderman, M. Brynolf, B. Holmström, “Identification of the epidural space with optical spectroscopy: An in vivo swine study,” Anesthesiology 113(6), 1406–1418 (2010).
[CrossRef] [PubMed]

van Kleef, M.

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. van Kleef, M. Sommer, “Optical detection of peripheral nerves: An in vivo human study,” Reg. Anesth. Pain Med. 37(3), 277–282 (2012).
[CrossRef] [PubMed]

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. Sommer, M. van Kleef, “Optical Detection of Vascular Penetration During Nerve Blocks: An In Vivo Human Study,” Reg. Anesth. Pain Med. 37(1), 3–7 (2012).
[CrossRef] [PubMed]

Villanueva, M. C.

M. A. Reina, P. Pulido, J. Castedo, M. C. Villanueva, A. López, R. G. Sola, “Characteristics and distribution of normal human epidural fat,” Rev. Esp. Anestesiol. Reanim. 53(6), 363–372 (2006).
[PubMed]

Wang, K.

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. Sommer, M. van Kleef, “Optical Detection of Vascular Penetration During Nerve Blocks: An In Vivo Human Study,” Reg. Anesth. Pain Med. 37(1), 3–7 (2012).
[CrossRef] [PubMed]

A. Balthasar, A. E. Desjardins, M. van der Voort, G. W. Lucassen, S. Roggeveen, K. Wang, W. Bierhoff, A. G. H. Kessels, M. van Kleef, M. Sommer, “Optical detection of peripheral nerves: An in vivo human study,” Reg. Anesth. Pain Med. 37(3), 277–282 (2012).
[CrossRef] [PubMed]

Welch, A. J.

S. A. Prahl, M. Keijzer, S. L. Jacques, A. J. Welch, “A Monte Carlo model of light propagation in tissue,” SPIE Institute Series. IS5, 102–111 (1989).

Wilkes, R. G.

S. M. Burns, C. M. Cowa, P. M. Barclay, R. G. Wilkes, “Intrapartum epidural catheter migration: A comparative study of three dressing applications,” Br. J. Anaesth. 86(4), 565–567 (2001).
[CrossRef] [PubMed]

Zubia, J.

J. Zubia, J. Arrue, “Plastic optical fibers: An introduction to their technological processes and applications,” Opt. Fiber Technol. 7(2), 101–140 (2001).
[CrossRef]

Anesth. Analg. (1)

J. Guay, “The epidural test dose: A review,” Anesth. Analg. 102(3), 921–929 (2006).
[CrossRef] [PubMed]

Anesthesiology (2)

C. K. Ting, M. Y. Tsou, P. T. Chen, K. Y. Chang, M. S. Mandell, K. H. Chan, Y. Chang, “A new technique to assist epidural needle placement: Fiberoptic-guided insertion using two wavelengths,” Anesthesiology 112(5), 1128–1135 (2010).
[CrossRef] [PubMed]

J. P. Rathmell, A. E. Desjardins, M. van der Voort, B. H. W. Hendriks, R. Nachabe, S. Roggeveen, D. Babic, M. Söderman, M. Brynolf, B. Holmström, “Identification of the epidural space with optical spectroscopy: An in vivo swine study,” Anesthesiology 113(6), 1406–1418 (2010).
[CrossRef] [PubMed]

Biomed. Opt. Express (1)

Br. J. Anaesth. (2)

S. P. Lin, M. S. Mandell, Y. Chang, P. T. Chen, M. Y. Tsou, K. H. Chan, C. K. Ting, “Discriminant analysis for anaesthetic decision-making: An intelligent recognition system for epidural needle insertion,” Br. J. Anaesth. 108(2), 302–307 (2012).
[CrossRef] [PubMed]

S. M. Burns, C. M. Cowa, P. M. Barclay, R. G. Wilkes, “Intrapartum epidural catheter migration: A comparative study of three dressing applications,” Br. J. Anaesth. 86(4), 565–567 (2001).
[CrossRef] [PubMed]

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Figures (6)

Fig. 1
Fig. 1

Simplified schematic of tissue structures in the vicinity of a needle/catheter insertion into the epidural space. SF: subcutaneous fat; SL: supraspinous ligament; IL: interspinous ligament; SP: spinous process; LF: ligamentum flavum; ES: epidural space; DM: dura mater CSF: cerebrospinal fluid; SC: spinal cord. Typical thicknesses of the dura mater, the epidural fat, and the ligamentum flavum are 0.3 mm, 6-13 mm, and 1.4 - 4.7 mm, respectively [13].

Fig. 2
Fig. 2

Distal end of the optical catheter. D: delivery light guide; R: receive light guide; U: unused light guide.

Fig. 3
Fig. 3

Transmission of the polymer guides embedded in the catheter. Prominent absorption peaks can be seen at wavelengths of 730, 900 and 1000 nm.

Fig. 4
Fig. 4

System schematic. The two connectorized light guides are connected to the source and detector, respectively. At the proximal end, the optical catheter is coupled to a commercial epidural catheter with metallic tubing to allow for fluid to be injected into the lumen.

Fig. 5
Fig. 5

The region around the spinal cord showing the tip of the optical catheter (arrow) on the surface of the dura mater (DM). Adjacent to the DM were the epidural fat (EF) and the ligamentum flavum (LF).

Fig. 6
Fig. 6

Mean spectra acquired during the laminectomy from ligamentum flavum (A); epidural fat (B); dura mater (C); blood (D). Dashed vertical lines correspond to hemoglobin absorption peaks (red: oxy-hemoglobin; blue: deoxy-hemoglobin). Solid vertical lines correspond to the isobestic points of the hemoglobin absorption spectrum that were used to calculate the hemoglobin parameter. To the right of each spectrum: the corresponding mean intensity (I) and hemoglobin (H) parameters and their standard deviations.

Tables (1)

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Table 1 Tissue Reflectivity and Average Maximum Depth for Adipose Tissue and Venous Blood Calculated with Monte Carlo Simulations

Equations (2)

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S ( λ ) = S tissue ( λ ) S dark ( λ ) S ref ( λ ) S dark ( λ )
H = S ( λ 1 ) S ( λ 2 ) S ( λ 1 )

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