Otitis Media Middle Ear Effusion Identification and Characterization Using an Optical Coherence Tomography Otoscope

OBJECTIVE

To determine the feasibility of detecting and differentiating middle ear effusions (MEEs) using an optical coherence tomography (OCT) otoscope.

STUDY DESIGN

Cross-sectional study.

SETTING

US tertiary care children's hospital.

SUBJECTS AND METHODS

Seventy pediatric patients undergoing tympanostomy tube placement were preoperatively imaged using an OCT otoscope. A blinded reader quiz was conducted using 24 readers from 4 groups of tiered medical expertise. The primary outcome assessed was reader ability to detect presence/absence of MEE. A secondary outcome assessed was reader ability to differentiate serous vs nonserous MEE.

RESULTS

OCT image data sets were analyzed from 45 of 70 total subjects. Blinded reader analysis of an OCT data subset for detection of MEE resulted in 90.6% accuracy, 90.9% sensitivity, 90.2% specificity, and intra/interreader agreement of 92.9% and 87.1%, respectively. Differentiating MEE type, reader identification of nonserous MEE had 70.8% accuracy, 53.6% sensitivity, 80.1% specificity, and intra/interreader agreement of 82.9% and 75.1%, respectively. Multivariate analysis revealed that age was the strongest predictor of OCT quality. The mean age of subjects with quality OCT was 5.01 years (n = 45), compared to 2.54 years (n = 25) in the remaining subjects imaged (P = .0028). The ability to capture quality images improved over time, from 50% to 69.4% over the study period.

CONCLUSION

OCT otoscopy shows promise for facilitating accurate MEE detection. The imageability with the prototype device was affected by age, with older children being easier to image, similar to current ear diagnostic technologies.

Magnetomotive Displacement of the Tympanic Membrane Using Magnetic Nanoparticles: Toward Enhancement of Sound Perception

OBJECTIVE

A novel hearing-aid scheme using magnetomotive nanoparticles (MNPs) as transducers in the tympanic membrane (TM) is proposed, aiming to noninvasively and directly induce a modulated vibration on the TM.

METHODS

In this feasibility study, iron oxide (Fe₃O₄) nanoparticles were applied on ex vivo rat TM tissues and allowed to diffuse over ∼2 h. Subsequently, magnetic force was exerted on the MNP-laden TM via a programmable electromagnetic solenoid to induce the magnetomotion. Optical coherence tomography (OCT), along with its phase-sensitive measurement capabilities, was utilized to visualize and quantify the nanometer-scale vibrations generated on the TM tissues.

RESULTS

The magnetomotive displacements induced on the TM were significantly greater than the baseline vibration of the TM without MNPs. In addition to a pure frequency tone, a chirped excitation and the corresponding spectroscopic response were also successfully generated and obtained. Finally, visualization of volumetric TM dynamics was achieved.

CONCLUSION

This study demonstrates the effectiveness of magnetically inducing vibrations on TMs containing iron oxide nanoparticles, manipulating the amplitude and the frequency of the induced TM motions, and the capability of assessing the magnetomotive dynamics via OCT.

SIGNIFICANCE

The results demonstrated here suggest the potential use of this noninvasive magnetomotive approach in future hearing aid applications. OCT can be utilized to investigate the magnetomotive dynamics of the TM, which may either enhance sound perception or magnetically induce the perception of sound without the need for acoustic speech signals.

Noninvasive in vivo optical coherence tomography tracking of chronic otitis media in pediatric subjects after surgical intervention

In an institutional review board-approved study, 25 pediatric subjects diagnosed with chronic or recurrent otitis media were observed over a period of six months with optical coherence tomography (OCT). Subjects were followed throughout their treatment at the initial patient evaluation and preoperative consultation, surgery (intraoperative imaging), and postoperative follow-up, followed by an additional six months of records-based observation. At each time point, the tympanic membrane (at the light reflex region) and directly adjacent middle-ear cavity were observed in vivo with a handheld OCT probe and portable system. Imaging results were compared with clinical outcomes to correlate the clearance of symptoms in relation to changes in the image-based features of infection. OCT images of most all participants showed the presence of additional infection-related biofilm structures during their initial consultation visit and similarly for subjects imaged intraoperatively before myringotomy. Subjects with successful treatment (no recurrence of infectious symptoms) had no additional structures visible in OCT images during the postoperative visit. OCT image findings suggest surgical intervention consisting of myringotomy and tympanostomy tube placement provides a means to clear the middle ear of infection-related components, including middle-ear fluid and biofilms. Furthermore, OCT was demonstrated as a rapid diagnostic tool to prospectively monitor patients in both outpatient and surgical settings.

Quantitative Pneumatic Otoscopy Using a Light-Based Ranging Technique

Otitis media is the leading cause of hearing loss in children. It is commonly associated with fluid in the ear, which can result in up to 45 dB of hearing loss for extended periods of time during a child's most important developmental years. Accurate assessment of middle ear effusions is an important part of understanding otitis media. Current technologies used to diagnose otitis media with effusion are pneumatic otoscopy, tympanometry, and acoustic reflectometry. While all of these techniques can reasonably diagnose the presence of an effusion, they provide limited information about the infection present behind the tympanic membrane.We have developed a technique based on low-coherence interferometry-a non-invasive optical ranging technique capable of sensing depth-resolved microscopic scattering features through the eardrum-to quantify eardrum thickness and integrity, as well as detect any effusion, purulence, or biofilm behind the tympanic membrane. In this manuscript, the technique is coupled with a pneumatic otoscope to measure minute deflections of the tympanic membrane from insufflation pressure stimuli. This results in quantitative measurements of tympanic membrane mobility, which may be used to gain a better understanding of the impact of infection on the membrane dynamics. A small pilot study of 15 subjects demonstrates the ability of pneumatic low-coherence interferometry to quantitatively differentiate normal ears from ears with effusions present. Analysis of the strengths and weaknesses of the technique, as well as focus areas of future research, is also discussed.

Non-invasive optical assessment of viscosity of middle ear effusions in otitis media

Eustachian tube dysfunction can cause fluid to collect within the middle ear cavity and form a middle ear effusion (MEE). MEEs can persist for weeks or months and cause hearing loss as well as speech and learning delays in young children. The ability of a physician to accurately identify and characterize the middle ear for signs of fluid and/or infection is crucial to provide the most appropriate treatment for the patient. Currently, middle ear infections are assessed with otoscopy, which provides limited and only qualitative diagnostic information. In this study, we propose a method utilizing cross-sectional depth-resolved optical coherence tomography to noninvasively measure the diffusion coefficient and viscosity of colloid suspensions, such as a MEE. Experimental validation of the proposed technique on simulated MEE phantoms with varying viscosity and particulate characteristics is presented, along with some preliminary results from in vivo and ex vivo samples of human MEEs. In vivo Optical Coherence Tomography (OCT) image of a human tympanic membrane and Middle Ear Effusion (MEE) (top), with a CCD image of the tympanic membrane surface (inset). Below is the corresponding time-lapse M-mode OCT data acquired along the white dotted line over time, which can be analyzed to determine the Stokes-Einstein diffusion coefficient of the effusion.

Quantitative characterization of mechanically indented in vivo human skin in adults and infants using optical coherence tomography

Influenced by both the intrinsic viscoelasticity of the tissue constituents and the time-evolved redistribution of fluid within the tissue, the biomechanical response of skin can reflect not only localized pathology but also systemic physiology of an individual. While clinical diagnosis of skin pathologies typically relies on visual inspection and manual palpation, a more objective and quantitative approach for tissue characterization is highly desirable. Optical coherence tomography (OCT) is an interferometry-based imaging modality that enables in vivo assessment of cross-sectional tissue morphology with micron-scale resolution, which surpasses those of most standard clinical imaging tools, such as ultrasound imaging and magnetic resonance imaging. This pilot study investigates the feasibility of characterizing the biomechanical response of in vivo human skin using OCT. OCT-based quantitative metrics were developed and demonstrated on the human subject data, where a significant difference between deformed and nondeformed skin was revealed. Additionally, the quantified postindentation recovery results revealed differences between aged (adult) and young (infant) skin. These suggest that OCT has the potential to quantitatively assess the mechanically perturbed skin as well as distinguish different physiological conditions of the skin, such as changes with age or disease.

Low-cost hand-held probe for depth-resolved low-coherence interferometry

We report on the development of a low-cost hand-held low-coherence interferometric imaging system based on the principle of linear optical coherence tomography (Linear OCT), a technique which was first proposed in the early 2000s as a simpler alternative to the conventional time-domain and Fourier-domain OCT. A bench-top implementation of the proposed technique is first presented and validated. The axial resolution, SNR, and sensitivity roll-of of the system was estimated to be 5.2 μm and 80 dB, and 3.7 dB over a depth of 0.15 mm, respectively. After validating the bench-top system, two hand-held probe implementations for contact-based imaging and in vivo human tympanic membrane imaging are presented. The performance of the proposed system was compared with a research-grade state-of-the-art Fourier-domain low coherence interferometry (LCI) system by imaging several biological and non-biological samples. The results of this study suggest that the proposed system might be a suitable choice for applications where imaging depth and SNR can be traded for lower cost and simpler optical design.

Rapid diagnosis and differentiation of microbial pathogens in otitis media with a combined Raman spectroscopy and low-coherence interferometry probe: toward in vivo implementation

We investigate and demonstrate the feasibility of using a combined Raman scattering (RS) spectroscopy and low-coherence interferometry (LCI) probe to differentiate microbial pathogens and improve our diagnostic ability of ear infections [otitis media (OM)]. While the RS probe provides noninvasive molecular information to identify and differentiate infectious microorganisms, the LCI probe helps to identify depth-resolved structural information as well as to guide and monitor positioning of the Raman spectroscopy beam for relatively longer signal acquisition times. A series of phantom studies, including the use of human middle ear effusion samples, were performed to mimic the conditions of in vivo investigations. These were also conducted to validate the feasibility of using this combined RS/LCI probe for point-of-care diagnosis of the infectious pathogen(s) in OM patients. This work establishes important parameters for future in vivo investigations of fast and accurate determination and diagnosis of infectious microorganisms in OM patients, potentially improving the efficacy and outcome of OM treatments, and importantly reducing the misuse of antibiotics in the presence of viral infections.

Ratiometric analysis of in vivo retinal layer thicknesses in multiple sclerosis

We performed ratiometric analysis of retinal optical coherence tomography images for the first time in multiple sclerosis (MS) patients. The ratiometric analysis identified differences in several retinal layer thickness ratios in the cohort of MS subjects without a history of optic neuritis (ON) compared to healthy control (HC) subjects, and there was no difference in standard retinal nerve fiber layer thickness (RNFLT). The difference in such ratios between HC subjects and those with mild MS-disability, without a difference in RNFLT, further suggests the possibility of using layer ratiometric analysis for detecting early retinal changes in MS. Ratiometric analysis may be useful and potentially more sensitive for detecting disease changes in MS.

A Mosaicking Approach for In Vivo Thickness Mapping of the Human Tympanic Membrane Using Low Coherence Interferometry

The thickness of the human tympanic membrane (TM) is known to vary considerably across different regions of the TM. Quantitative determination of the thickness distribution and mapping of the TM is of significant importance in hearing research, particularly in mathematical modeling of middle-ear dynamics. Change in TM thickness is also associated with several middle-ear pathologies. Determination of the TM thickness distribution could therefore also enable a more comprehensive diagnosis of various otologic diseases. Despite its importance, very limited data on human TM thickness distribution, obtained almost exclusively from ex vivo samples, are available in the literature. In this study, the thickness distribution for the in vivo human TM is reported for the first time. A hand-held imaging system, which combines a low coherence interferometry (LCI) technique for single-point thickness measurement, with video-otoscopy for recording the image of the TM, was used to collect the data used in this study. Data were acquired by pointing the imaging probe over different regions of the TM, while simultaneously recording the LCI and concomitant TM surface video image data from an average of 500 locations on the TM. TM thickness distribution maps were obtained by mapping the LCI imaging sites onto an anatomically accurate wide-field image of the TM, which was generated by mosaicking the sequence of multiple small field-of-view video-otoscopy images. Descriptive statistics of the thickness measurements obtained from the different regions of the TM are presented, and the general thickness distribution trends are discussed.

Detection of retinal blood vessel changes in multiple sclerosis with optical coherence tomography

Although retinal vasculitis is common in multiple sclerosis (MS), it is not known if MS is associated with quantitative abnormalities in retinal blood vessels (BVs). Optical coherence tomography (OCT) is suitable for examining the integrity of the anterior visual pathways in MS. In this paper we have compared the size and number of retinal blood vessels in patients with MS, with and without a history of optic neuritis (ON), and control subjects from the cross-sectional retinal images from OCT. Blood vessel diameter (BVD), blood vessel number (BVN), and retinal nerve fiber layer thickness (RNFLT) were extracted from OCT images collected from around the optic nerves of 129 eyes (24 control, 24 MS + ON, 81 MS-ON) of 71 subjects. Associations between blood vessel metrics, MS diagnosis, MS disability, ON, and RNFLT were evaluated using generalized estimating equation (GEE) models. MS eyes had a lower total BVD and BVN than control eyes. The effect was more pronounced with increased MS disability, and persisted in multivariate models adjusting for RNFLT and ON history. Twenty-nine percent (29%) of MS subjects had fewer retinal blood vessels than all control subjects. MS diagnosis, disability, and ON history were not associated with average blood vessel size. The relationship between MS and lower total BVD/BVN is not accounted for by RNFLT or ON. Further study is needed to determine the relationship between OCT blood vessel metrics and qualitative retinal blood vessel abnormalities in MS.

Intraoperative optical coherence tomography for assessing human lymph nodes for metastatic cancer

Background

Evaluation of lymph node (LN) status is an important factor for detecting metastasis and thereby staging breast cancer. Currently utilized clinical techniques involve the surgical disruption and resection of lymphatic structure, whether nodes or axillary contents, for histological examination. While reasonably effective at detection of macrometastasis, the majority of the resected lymph nodes are histologically negative. Improvements need to be made to better detect micrometastasis, minimize or eliminate lymphatic disruption complications, and provide immediate and accurate intraoperative feedback for in vivo cancer staging to better guide surgery.

Methods

We evaluated the use of optical coherence tomography (OCT), a high-resolution, real-time, label-free imaging modality for the intraoperative assessment of human LNs for metastatic disease in patients with breast cancer. We assessed the sensitivity and specificity of double-blinded trained readers who analyzed intraoperative OCT LN images for presence of metastatic disease, using co-registered post-operative histopathology as the gold standard.

Results

Our results suggest that intraoperative OCT examination of LNs is an appropriate real-time, label-free, non-destructive alternative to frozen-section analysis, potentially offering faster interpretation and results to empower superior intraoperative decision-making.

Conclusions

Intraoperative OCT has strong potential to supplement current post-operative histopathology with real-time in situ assessment of LNs to preserve both non-cancerous nodes and their lymphatic vessels, and thus reduce the associated risks and complications from surgical disruption of lymphoid structures following biopsy.

Sensor-Based Technique for Manually Scanned Hand-Held Optical Coherence Tomography Imaging

Hand-held optical coherence tomography (OCT) imaging probes offer flexibility to image sites that are otherwise challenging to access. While the majority of hand-held imaging probes utilize galvanometer- or MEMS-scanning mirrors to transversely scan the imaging beam, these probes are commonly limited to lateral fields-of-view (FOV) of only a few millimeters. The use of a freehand manually scanned probe can significantly increase the lateral FOV. However, using the traditional fixed-rate triggering scheme for data acquisition in a manually scanned probe results in imaging artifacts due to variations in the scan velocity of the imaging probe. These artifacts result in a structurally inaccurate image of the sample. In this paper, we present a sensor-based manual scanning technique for OCT imaging, where real-time feedback from an optical motion sensor is used to trigger data acquisition. This technique is able to circumvent the problem of motion artifacts during manual scanning by adaptively altering the trigger rate based on the instantaneous scan velocity, enabling OCT imaging over a large lateral FOV. The feasibility of the proposed technique is demonstrated by imaging several biological and nonbiological samples.

Real-time automated thickness measurement of the in vivo human tympanic membrane using optical coherence tomography

BACKGROUND

Otitis media (OM), an infection in the middle ear, is extremely common in the pediatric population. Current gold-standard methods for diagnosis include otoscopy for visualizing the surface features of the tympanic membrane (TM) and making qualitative assessments to determine middle ear content. OM typically presents as an acute infection, but can progress to chronic OM, and after numerous infections and antibiotic treatments over the course of many months, this disease is often treated by surgically inserting small tubes in the TM to relieve pressure, enable drainage, and provide aeration to the middle ear. Diagnosis and monitoring of OM is critical for successful management, but remains largely qualitative.

METHODS

We have developed an optical coherence tomography (OCT) system for high-resolution, depth-resolved, cross-sectional imaging of the TM and middle ear content, and for the quantitative assessment of in vivo TM thickness including the presence or absence of a middle ear biofilm. A novel algorithm was developed and demonstrated for automatic, real-time, and accurate measurement of TM thickness to aid in the diagnosis and monitoring of OM and other middle ear conditions. The segmentation algorithm applies a Hough transform to the OCT image data to determine the boundaries of the TM to calculate thickness.

RESULTS

The use of OCT and this segmentation algorithm is demonstrated first on layered phantoms and then during real-time acquisition of in vivo OCT from humans. For the layered phantoms, measured thicknesses varied by approximately 5 µm over time in the presence of large axial and rotational motion. In vivo data also demonstrated differences in thicknesses both spatially on a single TM, and across normal, acute, and chronic OM cases.

CONCLUSIONS

Real-time segmentation and thickness measurements of image data from both healthy subjects and those with acute and chronic OM demonstrate the use of OCT and this algorithm as a robust, quantitative, and accurate method for use during real-time in vivo human imaging.

Noninvasive depth-resolved optical measurements of the tympanic membrane and middle ear for differentiating otitis media

OBJECTIVE/HYPOTHESIS

In this study, optical coherence tomography (OCT) is used to noninvasively and quantitatively determine tympanic membrane (TM) thickness and the presence and thickness of any middle-ear biofilm located behind the TM. These new metrics offer the potential to differentiate normal, acute, and chronic otitis media (OM) infections in pediatric subjects.

STUDY DESIGN

Case series with comparison group.

METHODS

The TM thickness of 34 pediatric subjects was acquired using a custom-built, handheld OCT system following a traditional otoscopic ear exam.

RESULTS

Overall thickness (TM and any associated biofilm) was shown to be statistically different for normal, acute, and chronic infection groups (normal-acute and normal-chronic: P value < 0.001; acute-chronic: P value = 0.0016). Almost all observed scans from the chronic group had an accompanying biofilm structure. When the thickness of the TM and biofilm were considered separately in chronic OM, the chronic TM thickness correlated with the normal group (P value = 0.68) yet was still distinct from the acute OM group (P value < 0.001), indicating that the TM in chronic OM returns to relatively normal thickness levels.

CONCLUSION

Identifying these physical changes in vivo provides new metrics for noninvasively and quantitatively differentiating normal, acute, and chronic OM. This new diagnostic information has the potential to assist physicians to more effectively and efficiently screen, manage, and refer patients based on quantitative data.

LEVEL OF EVIDENCE

4.

In vivo pump-probe optical coherence tomography imaging in Xenopus laevis

Currently, optical coherence tomography (OCT), is not capable of obtaining molecular information often crucial for identification of disease. To enable molecular imaging with OCT, we have further developed a technique that harnesses transient changes in light absorption in the sample to garner molecular information. A Fourier-domain Pump-Probe OCT (PPOCT) system utilizing a 532 nm pump and 830 nm probe has been developed for imaging hemoglobin. Methylene blue, a biological dye with well-know photophysics, was used to characterize the system before investigating the origin of the hemoglobin PPOCT signal. The first in vivo PPOCT images were recorded of the vasculature in Xenopus laevis. The technique was shown to work equally well in flowing and nonflowing vessels. Furthermore, PPOCT was compared with other OCT extensions which require flow, such as Doppler OCT and phase-variance OCT. PPOCT was shown to better delineate tortuous vessels, where nodes often restrict Doppler and phase-variance reconstruction.

Volumetric imaging of erythrocytes using label-free multiphoton photoacoustic microscopy

Photoacoustic microscopy (PAM) is an imaging modality well suited to mapping vasculature and other strong absorbers in tissue. However, one of the primary drawbacks to PAM when used for high-resolution imaging is the relatively poor axial resolution due to the inverse dependence on the transducer bandwidth. While submicron lateral resolution PAM can be achieved by tightly focusing the excitation light, the axial resolution is fundamentally limited to 10s of microns for typical transducer frequencies. Here we present a multiphoton PAM technique called transient absorption ultrasonic microscopy (TAUM), which results in a completely optically resolved voxel with an experimentally measured axial resolution of 1.5 microns. This technique is demonstrated by imaging individual red blood cells in three dimensions in blood smear and ex vivo tissues. To the best of our knowledge, this is the first demonstration of fully resolved, volumetric photoacoustic imaging of erythrocytes.

Optical coherence tomography for advanced screening in the primary care office

Optical coherence tomography (OCT) has long been used as a diagnostic tool in the field of ophthalmology. The ability to observe microstructural changes in the tissues of the eye has proved very effective in diagnosing ocular disease. However, this technology has yet to be introduced into the primary care office, where indications of disease are first encountered. We have developed a portable, handheld imaging probe for use in the primary care setting and evaluated its tissue site accessibility, ability to observe diseased tissue, and screening capabilities in in vivo human patients, particularly for pathologies related to the eye, ear and skin. Various stages of diabetic retinopathy were investigated using the handheld probe and early-stage diabetic retinopathy was flagged as abnormal from the OCT images. At such early stages of disease, it is difficult to observe abnormalities with the limited tools that are currently available to primary care physicians. These results indicate that OCT shows promise to transform from being a diagnostic technology in the medical and surgical specialities to a screening technology in the primary care office and at the front-line of healthcare.

Molecular specificity in photoacoustic microscopy by time-resolved transient absorption

We have recently harnessed transient absorption, a resonant two-photon process, for ultrahigh resolution photoacoustic microscopy, achieving nearly an order of magnitude improvement in axial resolution. The axial resolution is optically constrained due to the two-photon process unlike traditional photoacoustic microscopy where the axial resolution is inversely proportional to the frequency bandwidth of the detector. As a resonant process, the arrival time of the two photons need not be instantaneous. Systematically recording the signal as a function of the delay between two pulses will result in the measurement of an exponential decay whose time constant is related to the molecular dynamics. This time constant, analogous to the fluorescence lifetime, but encompassing nonradiative decay as well, can be used to differentiate between molecular systems with overlapping absorption spectra. This is frequently the situation for closely related yet distinct molecules such as redox pairs. In order to enable the measure of the exponential decay, we have reconfigured our transient absorption ultrasonic microscopy (TAUM) system to incorporate two laser sources with precisely controlled pulse trains. The system was tested by measuring Rhodamine 6G, an efficient laser dye where the molecular dynamics are dominated by the fluorescence pathway. As expected, the measured exponential time constant or ground state recovery time, 3.3±0.7  ns, was similar to the well-known fluorescence lifetime, 4.11±0.05  ns. Oxy- and deoxy-hemoglobin are the quintessential pair whose relative concentration is related to the local blood oxygen saturation. We have measured the ground state recovery times of these two species in fully oxygenated and deoxygenated bovine whole blood to be 3.7±0.8  ns and 7.9±1.0  ns, respectively. Hence, even very closely related pairs of molecules may be differentiated with this technique.

Abstract P1-01-23: Intraoperative optical coherence tomography for the assessment of metastatic disease in human lymph nodes

The status of lymph nodes is an important factor in staging cancer since the transport of primary cancer cells via the lymphatic system is one of the main pathways of metastasis to distant organs. During cancer surgery, lymph node status is evaluated via sentinel lymph node biopsy (SLNB), which involves the removal and analysis of the first (or sentinel) nodes along the lymphatic chain of nodes draining the primary tumor. The sentinel nodes are identified through the accumulation of a radioactive agent (technetium-99) and/or isosulfan blue dye within the nodes, frequently resulting in the resection of multiple nodes for subsequent, often time-consuming, histopathological analysis. The majority of these resected nodes are found by histological analysis to be normal, leading to unnecessary complications, including increased risk of lymphedema. Thus, a method for the in situ assessment of node status could reduce the number of normal lymph nodes that are resected. In this study we evaluated the sensitivity and specificity of three-dimensional optical coherence tomography (OCT) for the intraoperative assessment of metastatic disease in lymph nodes.

OCT is the optical analogue to ultrasound imaging, except images are based on the optical scattering properties of near-infrared light. Real-time OCT with micron-scale resolution affords optical biopsies of tissue for immediate feedback. Intraoperative OCT imaging was conducted on human lymph nodes resected from 49 subjects during breast and, head and neck cancer surgeries. Three-dimensional OCT datasets were recorded ex vivo from one or more locations per node, and marked with surgical ink for subsequent correlation to histology. These lymph nodes then underwent the standard histological processing.

A double-blinded study was performed comparing the assessment of OCT datasets to the co-registered histological findings. Three-dimensional -OCT datasets from 206 sites were independently analyzed by six observers and classified as cancerous or non-cancerous. Seventy-nine sets were identified as unsuitable for OCT analysis due to insufficient nodal tissue within the imaged field-of-view. Early training classification results from three of the six observers resulted in a sensitivity of 64.8% and a specificity of 73.3% for identifying metastatic lymph nodes intraoperatively, in real-time, compared to the gold standard of post-operative histopathology. Final study results are expected to improve with observer training and a decision tree for interpreting OCT images.

Our initial imaging studies of resected lymph nodes in human cancer subjects demonstrate the potential of OCT as a technique for real-time optical biopsy of lymph nodes for the intraoperative staging of cancer.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P1-01-23.

Continuous real-time photoacoustic demodulation via field programmable gate array for dynamic imaging of zebrafish cardiac cycle

A four dimensional data set of the cardiac cycle of a zebrafish embryo was acquired using postacquisition synchronization of real time photoacoustic b-scans. Utilizing an off-axis photoacoustic microscopy (OA-PAM) setup, we have expanded upon our previous work with OA-PAM to develop a system that can sustain 100 kHz line rates while demodulating the bipolar photoacoustic signal in real-time. Real-time processing was accomplished by quadrature demodulation on a Field Programmable Gate Array (FPGA) in line with the signal digitizer. Simulated data acquisition verified the system is capable of real-time processing up to a line rate of 1 MHz. Galvanometer-scanning of the excitation laser inside the focus of the ultrasonic transducer enables real data acquisition of a 200 by 200 by 200 pixel, volumetric data set across a 2 millimeter field of view at a rate of 2.5 Hz.

Imaging high-frequency periodic motion in the mouse ear with coherently interleaved optical coherence tomography

Vibratory measurements of the structures of the ear are key to understanding much of the pathology in mouse models of hearing loss. Unfortunately the high-speed sampling required to interrogate the high end of the mouse hearing spectrum is beyond the reach of most optical coherence tomography (OCT) systems. To address this issue, we have developed an algorithm that enables phase-sensitive OCT measurements over the full range of the mouse hearing spectrum (4-90 kHz). The algorithm phase-locks the line-trigger to the acoustic stimulation and then uses interleaved sampling to reconstruct the signal with higher temporal sampling. The algorithm was evaluated by measuring the vibratory response of mouse tympanic membrane to a pure tone stimulus.

Quantitative imaging of cochlear soft tissues in wild-type and hearing-impaired transgenic mice by spectral domain optical coherence tomography

Human hearing loss often occurs as a result of damage or malformations to the functional soft tissues within the cochlea, but these changes are not appreciable with current medical imaging modalities. We sought to determine whether optical coherence tomography (OCT) could assess the soft tissue structures relevant to hearing using mouse models. We imaged excised cochleae with an altered tectorial membrane and during normal development. The soft tissue structures and expected anatomical variations were visible using OCT, and quantitative measurements confirmed the ability to detect critical changes relevant to hearing.

Ultrahigh resolution photoacoustic microscopy via transient absorption

We have developed a novel, hybrid imaging modality, Transient Absorption Ultrasonic Microscopy (TAUM), which takes advantage of the optical nonlinearities afforded by transient absorption to achieve ultrahigh-resolution photoacoustic microscopy. The theoretical point spread function for TAUM is functionally equivalent to confocal and two-photon fluorescence microscopy, potentially enabling cellular/subcellular photoacoustic imaging. A prototype TAUM system was designed, built, and used to image a cross-section through several capillaries in the excised cheek pouch of a Syrian Hamster. The well-resolved capillaries in the TAUM image provided experimental evidence of the spatial resolution. These results suggest that TAUM has excellent potential for producing volumetric images with cellular/subcellular resolution in three dimensions deep inside living tissue.

Fourier domain Pump-Probe Optical Coherence Tomography imaging of melanin

We report the development of a two-color Fourier domain Pump-Probe Optical Coherence Tomography (PPOCT) system. Tissue phantom experiments to characterize the system performance demonstrated imaging depths in excess of 725 microm, nearly comparable to the base Optical Coherence Tomography system. PPOCT A-line rates were also demonstrated in excess of 1 kHz. The physical origin of the PPOCT signal was investigated with a series of experiments which revealed that the signal is a mixture of short and long lifetime component signals. The short lifetime component was attributed to transient absorption while the long lifetime component may be due to a mixture of transient absorption and thermal effects. Ex vivo images of porcine iris demonstrated the potential for imaging melanin in the eye, where cancer of the melanocytes is the most common form of eye cancer in adults.

Off-axis photoacoustic microscopy

Photoacoustic microscopy (PAM) is a high-contrast, high-resolution imaging modality, used primarily for imaging hemoglobin and melanin. Important applications include mapping of the microvasculature and melanoma tumor margins. We demonstrate a novel PAM design that markedly simplifies the implementation by separating the optical illumination from the acoustic detection path. This modification enables the use of high-quality commercial optics and transducers, and may be readily adapted to commercial light microscopes. The designed PAM system is only sensitive to signals generated in the overlap of the illumination and detection solid angles, providing the additional benefit of quasi-dark-field detection. An off-axis PAM system with a lateral resolution of 26 microm and a modest axial resolution of 410 microm has been assembled and characterized using tissue samples. The axial resolution is readily scaled down to tens of micrometers within the same design, by utilizing commercially available high-frequency acoustic transducers.

Use of a hinge-type speech prosthesis

This report describes a hinge-type speech prosthesis and its owner's use of the two halves of her cleft velum to elevate the velar section of the prosthesis. With the prosthesis, her speech is free from articulation errors, audible nasal emission, and hypernasality. Acquisition of the ability to move the velar section is discussed.

Custom-fabricated masks for aeromechanical measures

A technique is described for the construction of custom fabricated face masks designed for use in aeromechanical studies of individuals with speech disorders, such as those associated with craniofacial defects. The wax-elimination method of mask fabrication described herein is similar to routine dental laboratory procedures. Materials employed are heat-cured acrylic resin for the body of the mask and heat-cured resilient liner for the tissue contacting surface of the mask.

Location of the maltosyl isothiocyanate binding site on the human erythrocyte glucose transporter

The covalent affinity probe maltosyl isothiocyanate (MITC) has been used previously to identify the glucose transporter of human erythrocytes as a component of band 3. By use of limited proteolysis, the site on the Mr 100 000 protein to which MITC attaches has been localized to a 17 000-dalton region near the center of the polypeptide chain which is intimately associated with the membrane. The erythrocyte anion transporter, which is probably homologous to the glucose carrier, has a corresponding segment which is known to bind the covalent affinity label 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid [Ramjeesingh, M., Gaarn, A., & Rothstein, A. (1980) Biochim. Biophys. Acta 559, 127-139]. These results suggest that, in addition to having structural features in common, the two carrier proteins may be quite similar with regard to functional organization.

Quantitation of the major proteins of the human erythrocyte membrane by amino acid analysis

The proteins of the human erythrocyte membrane have been separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the resulting gel cut into 2-mm sections, and the amino acid content and composition of each slice measured using a sensitive method of amino acid analysis. The distribution of proteins among bands coincides closely with that estimated using staining intensity. Composition data for the major bands agree well with those reported for the purified proteins in all cases except that of band 4.5. Using quantitative amino acid analysis and resistive particle counting the total protein content of purified membranes was found to be 3.75 X 10(-13) g/cell, which is substantially less than previous estimates based on indirect methods. These data are used to calculate the number of copies of each major protein in a single erythrocyte.

Oronasal fistulas, intraoral air pressure, and nasal air flow during speech

Aeromechanical data are presented for six patients with oronasal fistulas and one with a maxillary cleft. Patients were studied with the defects open and again with them closed with either acrylic dental appliances, dental wax, or denture adhesive. Only the largest openings appeared to allow sufficient loss of intraoral air pressure to weaken obstruent consonants. All but the smallest of the defects were associated with nasal air flow during syllable strings. Thus the data are compatible with a hypothesis that in the presence of small air leaks patients maintain sufficient intraoral air pressure for accurate consonant production. Presumably this is achieved by increase in respiratory effort. The relationship between fistula size and speech or speech related variables appears to be similar to that between area of the velopharyngeal opening and speech. However, the fistula is more constant in area across utterances than is the pathological velopharyngeal mechanism.

Reconstitution of glucose transport using human erythrocyte band 3

Band 3 and the diffuse component of zone 4.5, designated band 4.5.B, have been separately prepared from human erythrocyte membranes and incorporated into the membranes of 150 nm 1-palmitoyl-2-oleoyl phosphatidylcholine vesicles. The rates of glucose influx into these vesicles were measured under zero-trans conditions. Both sets of vesicles exhibited substrate-saturable transport which was inhibited by phloretin. However, the specific activity of the band 3 vesicles, 292 mumol X min-1 X (mg protein)-1, was more than twice that of the band 4.5.B vesicles, and the turnover number of transporters in the band 3 vesicles was at least 4-fold greater than those in the 4.5.B vesicles. Very little background density was visible in the band 4.5 region of erythrocyte membranes protected from degradation. In unprotected membranes, band 4.5.B was abundantly present, could be purified, and had glucose transport activity. Previously we have shown (Biochemistry 19, 1205 (1980] that maltosyl isothiocyanate, an affinity label for the glucose transporter, labelled a single 100 000 Mr protein of the intact erythrocyte membrane. Based upon the results of both affinity labelling and reconstitution we suggest that the native glucose transporter is a component of band 3, and that band 4.5.B contains a partially active fragment of the native transporter.

A technique for identifying the subgroup membership of certain misarticulating children

Cluster analysis was used to identify two homogeneous clusters of 8-9 1/2-year-old children who misarticulated /s/, /r/, or both. The analysis was based on the children's scores on 40 measures of language, reading, auditory processing, and other variables. Discriminant function analysis was then used to identify a subset of five measures and a means of computing classification scores. These measures and the classification scores can be used to identify the cluster membership of new subjects. The use of classification scores for identifying cluster membership was cross-validated against cluster analysis of a second group of children. The two clusters are described in terms of their performance on language and reading measures.

Influence of the emetic reflex on vasopressin release in man

The mechanisms underlying the frequent association of nausea and vomiting with elevations of plasma vasopressin(PAVP) were studied in man and rat. After oral water loads (N = 16), plasma osmolality fell in all human subjects and was associated with a decline in PAVP in 14 asymptomatic human subjects. In 2 human subjects, nausea occurred and was associated with increases in PAVP, without changes in blood pressure. During ethanol infusion (N = 28), PAVP was suppressed unless nausea supervened. In 4 nauseated human subjects, PAVP escaped from ethanol inhibition and rose to levels 10 times basal, despite the absence of hemodynamic changes. Apomorphine, a potent dopamine agonist and emetic agent, was administered to human volunteers in doses of 7 to 24 microgram/kg. There was no increase in PAVP in 3 human subjects who remained asymptomatic (7 to 16 microgram/kg). Ten human subjects experienced nausea after 16 microgram/kg, which was followed shortly by marked increases in PAVP. Emesis occurred in 5 human subjects given 16 to 24 microgram/kg, and was followed by PAVP levels similar to those seen with nausea alone. In 7 human subjects from the nausea group, the repeat study (16 microgram/kg) after pretreatment with dopamine antagonist (haloperidol, N = 4; fluphenazine, N = 3) resulted in complete blockage of apomorphine-induced AVP release. In rats, which lack an emetic reflex, apomorphine doses of 200 microgram/kg induced only slight increases in PAVP when compared to the response to 16 microgram/kg in man. These studies indicate that stimulation of the emetic reflex results in AVP-release in man. Nausea-mediated AVP release supervenes over concomitant osmolar or pharmacologic (ethanol) inhibition.

Planning and self-assessment in articulatory training

Children misarticulating the /r/ or /s/ speech sounds or both were identified, and assigned randomly to one of two groups. Each group received speech lessons that were similar. However, during response acquisition training, Group 1 was requested to plan articulatory movements mentally, produce the target sound, and assess the production. Group 2 practiced the training units without using the planning and assessment procedures. Group 1 exceeded Group 2 on generalization measures when the planning and assessment training was in effect.

Assessment of parent-administered listening training for preschool children with articulation deficits

Two studies concerning preschool misarticulating children are reported. The first study was concerned with direct effects of two varieties of parent-administered listening training. The second study focused on the influence of that same training on children's responses to sound-production training. Subjects were assigned to one of three conditions: listening, reading-talking, and control. Children in the first group were provided training by their parents that was intended to focus the child's attention on consonants in syllables or words and to teach discrimination between correctly and incorrectly articulated consonants. Parents of children in the second group read to and talked with them about the material. Neither treatment group surpassed the control group in gains made on any auditory processing or articulatory measure employed, and some parents found the listening training frustrating. In the second study, a subset of the children in each of the three groups was given sound-production training. The data obtained did not show any effect from earlier listening experiences on sound-production performance.

Videoendoscopic feedback in training velopharyngeal closure

Each of two adolescents with velopharyngeal closure deficits was taught to position him or herself on an endoscope attached to a television camera and to observe the velopharyngeal port during the production of syllables and other units. The videoendoscope was then used as a training apparatus, and each subject was given practice attempting to increase velopharyngeal closure while producing vowels and syllables. Videorecordings of each subject made without feedback before, during, and after the training period were played to panels of observers who were to rate closure during each utterance, and the data obtained indicated that the subjects more frequently approximated complete closure as the study progressed but improved performance was not established on an automatic level. Suggestions are made for the refinement and further investigation of videoendoscopic closure training.

Delayed judgment speech-sound discrimination and /r/ or /s/ articulation status and improvement

A delayed judgment test of speech-sound discrimination was correlated with measures of articulation status and articulation improvement with training in two groups of subjects, an /r/ group and an /s/ group. While the discrimination measures were reliable and internally consistent, discrimination-articulation correlations were low. Several possible psychometric explanations for the nonsignificant results are ruled out, and subject and task variables that might interfere with children's performance on discrimination measures are discussed.

Factor analysis of measures of articulation, language, auditory processing, reading-spelling, and maxillofacial structure

This study was concerned with the correspondence between the classification of measures by clinical judgement and by factor analysis. Forty-six measures were selected to assess language, auditory processing, reading-spelling, maxillofacial structure, articulation, and other processes. These were applied to 98 misarticulating eight- and nine-year-old children. Factors derived from the analysis corresponded well with categories the measures were selected to represent.

Identification and description of homogeneous subgroups within a sample of misarticulating children

A multivariate, hierarchical clustering procedure was used to identify homogeneous subgroups among 98 misarticulating children age eight years through nine years, six months. Clustering was based on 40 tests or measures of language, auditory processing, school achievement, oral structure, oral form recognition, and other phenomena. Clusters were described and then compared for performance on measures of articulation status and articulation improvement with training. Clusters were also derived from subsets of children who misarticulated only one sound, either /s/or/r/. Also, the subset of children who misarticulated /s/ was compared with children who misarticulated /r/ for performance on the measures classified above. Few of the clusters identified differed in articulation status or improvement with training.

Issues involved in the evaluation of velopharyngeal closure

The development and use of frontal and base-view fluorography have increased the value of cinefluorography in the evaluation of velopharyngeal closure. This paper discusses problems in the fluorographic examination of the closure mechanism, the need for other measures of velopharyngeal closure, and the validation of closure measures. Reliability data are needed for measurements made from frontal and base-view films and tapes. Measures in addition to those of a fluorographic nature are needed for the identification of persons with questionable velopharyngeal closure and for use in the evaluation of training procedures that may contribute to improved use of the velopharyngeal closure mechanism. A pattern of relationships among fluorographic and nonfluorograph measures of velopharyngeal closure can be studied in the validation of both classes of measures.

Panendoscopic feedback in the study of voluntary velopharyngeal movements

A videopanendoscope system was used to record velopharyngeal movements and to display those movements to subjects who produced them. Three normal adults were studied as they attempted to produce nonspeech velopharyngeal closure by use of two maneuvers: (1) laryngeal fixation and (2) modification of an elicited gag reflex. A rating system was devised to extract data from the videotapes. The findings indicated that subjects were able to utilize the videopanendoscopic feedback to guide voluntary velopharyngeal movements. The velopharyngeal movements were accompanied by larynx displacement and other neck muscle contraction. The uvula was observed to contract during some motor acts.

Variability in judgments of articulation when observer listens repeatedly to the same phone

This study pertains to variability in articulation judgments made by Os who listened to repetitions of the same stimulus. In the first portion of the study, four Os were asked to listen to six tapes, each of which was prepared to present 90 repetitions of a syllable. The syllables were /sa/ and /rk/.2 The /s/ and /r/2 in two of the syllables were correctly articulated, in two they were moderately distorted, and in two they were severely distorted. Correctness of articulation of the target phones had been established previously by a panel of judges using a scaling procedure. The speakers were children with articulation problems. A total of 24 sets of judgments were obtained. For three of those sets, O frequently shifted between assessment of the phone as correct and incorrect. In the second portion, each of three tapes was evaluated by five of 15 judges. Two tapes were reused from the first part of the study, and a new tape presenting the same production of /is/ 90 times was also used. No judge listened to more than one tape. Again, a record was made of the frequency with which judges shifted in their assessment of a given articulation as correct or incorrect. More judges reported 12 or more shifts in the second portion of the study than in the first. O's consistency should be investigated in the situation where O evaluates a series of similar misarticulations of phones from the same phoneme.

Oral form recognition training and articulation change

10 children with articulation disorders were given training in recognition of forms through oral exploration of those forms. Training materials were divided into sets. Fewer trials were required to reach performance criteria from one set to another, and fewer errors were made as Ss progressed from set to set. The control procedure used indicated that information gained through oral study of the forms contributed to performance but was not necessary to performance improvement. No gains were observed in any of four articulation measures.