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R119: Noninvasive Measurement of In Vivo Pinna and Ear Canal
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Otolaryngology-Head and Neck Surgery, Vol 137, No 2S, August 2007
tween the SSC and other surgical landmarks in the transmastoid approach to see if it is a feasible alternative to craniotomy. METHODS: Thirty cadaveric temporal bones were dissected to expose the sigmoid sinus, middle fossa dura and semicircular canals by the TMA. Distances between the SSC and various structures within the temporal bone were measured with a fine caliper. The sino-dural angle, top of the horizontal SC, and subacurate artery were chosen as landmarks for identification of the SSC. RESULTS: The average distances from these respective landmarks to the top of the SSC were 31.3, 7.91, and 3.99 mm, within a small range. The distance between top of the SSC and middle fossa tegmen ranged from 0 mm to 2.2 mm with the average being 0.54 mm. No supralabyrinthine cells were seen in 16 (53.3%) out of 30 bones examined, while a low tegmen lateral to the SSC was identified in 10 (33.3%) temporal bones. It was difficult to conduct a TMA in 3 bones (10%) with no supralabyrinthine cells and a low tegmen. CONCLUSION: The cadaver results suggest that a transmastoid approach is a possible alternative for treatment of SSCD. These measurements may facilitate identification on the SCC during this approach. SIGNIFICANCE: A transmastoid approach is a possible alternative for surgical treatment of SSCD.
R119 Noninvasive Measurement of In Vivo Pinna and Ear Canal Jen-Fang Yu, PhD, FE (presenter); Chung-Chieh Fan, MD; Chung-Yi Lee, MD PROBLEM: To noninvasively measure the spatial characteristics of the in vivo human pinna and ear canal to further explain some of the variability in long-term improvement after the surgery for otoplasty. METHODS: All CT images of 10 volunteers’ outer ears have been acquired by a 16-slice CT system; the volunteers were aged 20 to 65 years. The pixel resolution of the acquired image for the volunteers’ right ears was 0.352mm⫻0.352mm. The configuration of the pinna, cymba and cavum of concha, ear canal could be detected by the threshold image reconstruction. The geometry of pinna, concha, and ear canal were then obtained. RESULTS: The volume of pinna was 12312 cubic mm. The volume of cymba and cavum of concha were 1112.2 and 2007.6 cubic mm. The ear canal volume was 864.3 cubic mm for the volunteers. The variability of dimensional characteristics of the other volunteers’ pinnas and ear canals were further analyzed. The number of volunteers did not reach a statistically significant level. CONCLUSION: The geometry and dimensional characteristics of pinna, concha and ear canal were all qualified by the CT image. Using the proposed measurement method, the spatial
configuration of the in vivo human pinna, concha and ear canal can be tracked in pre- and postoperation for otoplasty noninvasively. SIGNIFICANCE: Knowledge of the structure of the pinna and concha may help determine the cause of the continued problems such as microtia and anotia. Age-related changes in the mechanics of the ear canal can explain part of the age-related hearing sensitivity observed.
R120 A Benchtop Fluid Dynamic Model of the Inner Ear Vivian M Yu, MD (presenter); Rick Odland, MD, PhD; Paul Strykowski, MD PROBLEM: Perilymph and endolymph are two parallel fluidic systems nominally in hydrodynamic equilibrium. With a change in head position, hydrostatic pressure changes and a new equilibrium must be attained quickly. The resistance-compliance product is proportional to time to equilibrium. A bench-top model was developed to test the hypothesis that increasing resistance within the endolymph will increase the time to hydrodynamic equilibrium after a change in position. METHODS: The model consisted of rigid plastic representing the bony semicircular canal and compliant latex representing the membranous portion. The model was rotated in a standardized manner. A valve in open, intermediate, and closed positions was used to vary resistance in one limb of the parallel system. A video recorded the distortion of the compliant membrane. RESULTS: The areas under the three curves were significantly different by ANOVA (p ⫽ 5.9 x 10-8). With the valve open, the membranous portion of the model exhibited minimal distortion. With the value closed, the membranous portion reached a maximal compression of 24% at 7 seconds and remained compressed. In the intermediate position, the maximal compression of 17% was also attained at 7 seconds, and then slow decompression to prerotation size occurred by 45 seconds. CONCLUSION: In this model, the time to equilibrium increased as resistance to fluid flow in one limb of the system increased. These data support the hypothesis that a change in resistance or compliance of one system causes transient dysequilibrium and distortion of the membranous labyrinth. SIGNIFICANCE: Fluid dynamics may play a role in diseases such as benign positional vertigo. Studying this complicated physiology may lead to a better understanding of inner ear function and thereby improve therapy. SUPPORT: University of Minnesota Biomedical Engineering Institute Otolaryngology Interest Group Fund.
Otolaryngology-Head and Neck Surgery, Vol 137, No 2S, August 2007
tween the SSC and other surgical landmarks in the transmastoid approach to see if it is a feasible alternative to craniotomy. METHODS: Thirty cadaveric temporal bones were dissected to expose the sigmoid sinus, middle fossa dura and semicircular canals by the TMA. Distances between the SSC and various structures within the temporal bone were measured with a fine caliper. The sino-dural angle, top of the horizontal SC, and subacurate artery were chosen as landmarks for identification of the SSC. RESULTS: The average distances from these respective landmarks to the top of the SSC were 31.3, 7.91, and 3.99 mm, within a small range. The distance between top of the SSC and middle fossa tegmen ranged from 0 mm to 2.2 mm with the average being 0.54 mm. No supralabyrinthine cells were seen in 16 (53.3%) out of 30 bones examined, while a low tegmen lateral to the SSC was identified in 10 (33.3%) temporal bones. It was difficult to conduct a TMA in 3 bones (10%) with no supralabyrinthine cells and a low tegmen. CONCLUSION: The cadaver results suggest that a transmastoid approach is a possible alternative for treatment of SSCD. These measurements may facilitate identification on the SCC during this approach. SIGNIFICANCE: A transmastoid approach is a possible alternative for surgical treatment of SSCD.
R119 Noninvasive Measurement of In Vivo Pinna and Ear Canal Jen-Fang Yu, PhD, FE (presenter); Chung-Chieh Fan, MD; Chung-Yi Lee, MD PROBLEM: To noninvasively measure the spatial characteristics of the in vivo human pinna and ear canal to further explain some of the variability in long-term improvement after the surgery for otoplasty. METHODS: All CT images of 10 volunteers’ outer ears have been acquired by a 16-slice CT system; the volunteers were aged 20 to 65 years. The pixel resolution of the acquired image for the volunteers’ right ears was 0.352mm⫻0.352mm. The configuration of the pinna, cymba and cavum of concha, ear canal could be detected by the threshold image reconstruction. The geometry of pinna, concha, and ear canal were then obtained. RESULTS: The volume of pinna was 12312 cubic mm. The volume of cymba and cavum of concha were 1112.2 and 2007.6 cubic mm. The ear canal volume was 864.3 cubic mm for the volunteers. The variability of dimensional characteristics of the other volunteers’ pinnas and ear canals were further analyzed. The number of volunteers did not reach a statistically significant level. CONCLUSION: The geometry and dimensional characteristics of pinna, concha and ear canal were all qualified by the CT image. Using the proposed measurement method, the spatial
configuration of the in vivo human pinna, concha and ear canal can be tracked in pre- and postoperation for otoplasty noninvasively. SIGNIFICANCE: Knowledge of the structure of the pinna and concha may help determine the cause of the continued problems such as microtia and anotia. Age-related changes in the mechanics of the ear canal can explain part of the age-related hearing sensitivity observed.
R120 A Benchtop Fluid Dynamic Model of the Inner Ear Vivian M Yu, MD (presenter); Rick Odland, MD, PhD; Paul Strykowski, MD PROBLEM: Perilymph and endolymph are two parallel fluidic systems nominally in hydrodynamic equilibrium. With a change in head position, hydrostatic pressure changes and a new equilibrium must be attained quickly. The resistance-compliance product is proportional to time to equilibrium. A bench-top model was developed to test the hypothesis that increasing resistance within the endolymph will increase the time to hydrodynamic equilibrium after a change in position. METHODS: The model consisted of rigid plastic representing the bony semicircular canal and compliant latex representing the membranous portion. The model was rotated in a standardized manner. A valve in open, intermediate, and closed positions was used to vary resistance in one limb of the parallel system. A video recorded the distortion of the compliant membrane. RESULTS: The areas under the three curves were significantly different by ANOVA (p ⫽ 5.9 x 10-8). With the valve open, the membranous portion of the model exhibited minimal distortion. With the value closed, the membranous portion reached a maximal compression of 24% at 7 seconds and remained compressed. In the intermediate position, the maximal compression of 17% was also attained at 7 seconds, and then slow decompression to prerotation size occurred by 45 seconds. CONCLUSION: In this model, the time to equilibrium increased as resistance to fluid flow in one limb of the system increased. These data support the hypothesis that a change in resistance or compliance of one system causes transient dysequilibrium and distortion of the membranous labyrinth. SIGNIFICANCE: Fluid dynamics may play a role in diseases such as benign positional vertigo. Studying this complicated physiology may lead to a better understanding of inner ear function and thereby improve therapy. SUPPORT: University of Minnesota Biomedical Engineering Institute Otolaryngology Interest Group Fund.