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Objective: To investigate the current practice of intratympanic steroid (ITS) injection for sudden sensorineural hearing loss (SSNHL) in the United Kingdom and link the data with data from the United States and continental Europe. Methods: A survey of 21 questions was distributed to members of the British Society of Otology using an online survey platform via ENT UK. Data obtained from UK otolaryngologists (n = 171) were integrated with previously published data from other countries, including the United States (n = 63) and continental Europe (n = 908). Results: In the United Kingdom, 62% of responding otolaryngologists use ITS injection for SSNHL, while 38% do not. Of those using ITS, 59% use it as first-line treatment, either using it in conjunction with oral steroids (51%) or using it as monotherapy (8%). Of those that use ITS, a majority (83%) use it as salvage therapy when primary treatment with systemic steroids has failed, and similar results are found in the continental Europe and US surveys. The most commonly used preparation is dexamethasone. Responses to questions regarding treatment regimes used are enlightening and show considerable variation in the treatment regimes used within and between countries. Conclusions: There is a wide variation in practice with regards to ITS for SSNHL hearing loss in the United Kingdom, United States, and continental Europe. In the absence of protocols or definitive guidance from published literature, knowledge of contemporary practice may help guide or encourage reevaluation of clinical practice and will help guide the design of future clinical trials.

The frequency of the use of intratympanic steroids (ITS) as a treatment for idiopathic sudden sensorineural hearing loss (ISSNHL) in Europe is still unknown and remains a contentious issue amongst otolaryngologists. We undertook a survey of otolaryngologists in Germany and Austria to establish if there is any professional consensus with which to form a protocol for its use. A survey of 21 questions was distributed electronically to otolaryngologists in Germany and Austria and data on demographics, indications for intratympanic treatment, procedure, follow-up, and outcomes were analysed. We received 908 responses. 49.1% of otolaryngologists used ITS for ISSNHL. Of those otolaryngologists who use ITS, 73.7% do not use it as primary treatment. 20.6% use ITS in conjunction with oral steroids for primary treatment and only 5.8% use ITS as monotherapy for primary treatment. 90.5% use ITS as salvage therapy. 81.1% do not consider the use of ITS after 2 weeks from the onset of symptoms. 8.3% used a tympanostomy tube and while the most commonly used steroid was dexamethasone at a concentration of 4 mg/ml (61%), a wide variety or other steroids and concentrations were used. This survey illustrates wide variation of current practice of intratympanic corticosteroid injection for ISSHL in Germany and Austria. In the absence of high-level evidence, knowing what current practice is allows clinicians to assess what they do against what their colleagues are doing, and if they do something very different, make them question their practice. Moreover, the obtained data will help to direct future clinical trials with the aim to compare the outcomes of more commonly used protocols.

Objective To determine whether theta burst repetitive transcranial magnetic stimulation is an effective treatment for chronic tinnitus compared with a control stimulus. Study design A two-arm, single-blind, randomized controlled trial comparing an active treatment group to a placebo control group. Setting Neurotology department of a tertiary referral center. Patients Forty new and existing patients with chronic unilateral or bilateral tinnitus were recruited from specialist hearing and balance clinics. Interventions The subjects were randomized into two groups representing the treatment and sham subcategories. Two 40 second trains, 15 minutes apart of transcranial stimulation was provided using a super rapid stimulator (2.2. Tesla, Magstim Inc., Wales, UK) using a circular delivery coil. Treatment was provided over 5 consecutive days. Main outcome measure Tinnitus functional index (TFI) scores were recorded before treatment, immediately after treatment, 2 weeks, and at 4 weeks following treatment and compared. Results TFI scores were analyzed using the Shapiro-Wilk test and found to be normally distributed. A paired Student t test was then performed. Both the active treatment group and control group had a significant improvement in their TFI scores following treatment; however, there was no significant difference between active treatment and sham treatment groups. Conclusion This study demonstrated a significant placebo effect following treatment with sham therapy and may suggest that repetitive transcranial magnetic stimulation does not have a therapeutic use in treating chronic tinnitus.

This paper presents the use of a novel through-transmission ultrasonic (TTU) Acoustography non-destructive evaluation (NDE) method to detect foreign object inclusion (FOI) defects in graphite epoxy composite laminates. The study employed three different composite test standards with varied size FOI defects embedded at varying depth within the composite laminates. For validation, Acoustography results were directly compared with conventional immersion TTU testing and infrared thermography (IRT) methods. From results obtained, it was demonstrated that the Signal-to-Noise Ratio (SNR) measurements for Acoustography were more than 6:1 and were in good correlation with immersion TTU and IRT results. The defect sizing ability of TTU Acoustography for FOI defects in graphite epoxy composite laminates were also in strong correlation with immersion TTU and IRT techniques. Finally, for the three laboratory systems employed in this study, typical panel TTU Acoustography inspection time was just about three minutes to scan a 300 mm × 300 mm (11.8″ × 11.8″) area, which was more than three times faster compared to IRT and sixty times faster to conventional immersion TTU C-Scan techniques. This is a very significant finding for the reason that Acoustography is being developed as a faster, more efficient, and affordable alternative to traditional ultrasonic inspection systems for composite manufacturing quality control and quality assurance (QC/QA) and field maintenance of composite structure applications.

Dizziness is the commonest reason for a GP appointment over the age of 75 years and many dizzy patients will end up in hospital. This article introduces the range of vestibular disorders commonly seen in hospital practice with a symptom-based approach and discusses the range of treatments that might be considered.

In this Letter the authors introduce a wide-field transmission ultrasound approach to breast imaging based on the use of a large area acousto-optic (AO) sensor. Accompanied by a suitable acoustic source, such a detector could be mounted on a traditional mammography system and provide a mammographylike ultrasound projection image of the compressed breast in registration with the x-ray mammogram. The authors call the approach acoustography. The hope is that this additional information could improve the sensitivity and specificity of screening mammography. The AO sensor converts ultrasound directly into a visual image by virtue of the acousto-optic effect of the liquid crystal layer contained in the AO sensor. The image is captured with a digital video camera for processing, analysis, and storage. In this Letter, the authors perform a geometrical resolution analysis and also present images of a multimodality breast phantom imaged with both mammography and acoustography to demonstrate the feasibility of the approach. The geometric resolution analysis suggests that the technique could readily detect tumors of diameter of 3 mm using 8.5 MHz ultrasound, with smaller tumors detectable with higher frequency ultrasound, though depth penetration might then become a limiting factor. The preliminary phantom images show high contrast and compare favorably to digital mammograms of the same phantom. The authors have introduced and established, through phantom imaging, the feasibility of a full-field transmission ultrasound detector for breast imaging based on the use of a large area AO sensor. Of course variations in attenuation of connective, glandular, and fatty tissues will lead to images with more cluttered anatomical background than those of the phantom imaged here. Acoustic coupling to the mammographically compressed breast, particularly at the margins, will also have to be addressed.

Purpose: To investigate the feasibility of malignant lesion detection during routine breast cancer screening using an acousto-optic (AO) transmission ultrasound imaging system, particularly in premenopausal women with high breast density. Methods: A full-field, single-projection ultrasound imaging system was developed that uses a high-resolution AO detector to convert the acoustic intensity transmitted through the compressed breast into a visual image by virtue of the AO effect in nematic liquid crystals. In this work, a comprehensive system model was proposed to describe the AO imaging process, including the generation of the incident acoustic field by the transducer, the propagation of the field through the breast tissue, and the conversion of the transmitted acoustic field intensity into a visual image. Validation of the imaging model was achieved through comparison of actual AO breast phantom images with simulated images based on the proposed model. Malignant lesion detectability studies were subsequently performed in simulation using homogeneous and heterogeneous numerical breast phantoms. Results: Comparison of actual AO breast phantom images with simulated images based on the proposed system model showed strong agreement, with an RMSE less than 4%. Lesion detectability studies using homogeneous numerical breast phantoms demonstrated excellent visibility for breast lesions as small as 0.5 cm and source frequencies on the order of 4 MHz. Though lesion detectability proved immune to spatial variations in mass density (2%) and attenuation (15%) in the breast parenchyma, minor variations in parenchymal sound speed (1.3%) resulted in substantial refraction artifacts that compromised the diagnostic utility of the prototype system. Conclusions: Differences in acoustic absorption may overcome refraction and enhance lesion visibility at conventional breast ultrasound frequencies (10 to 15 MHz). However, provided the FDA limit on the incident acoustic intensity (1 W/cm2) is employed, such high-frequency imaging will require improvements in the current AO detector sensitivity (10−6 W/cm2). Department of Defense (DOD) Breast Cancer Research Program IDEA Award W81XWH-11-1-0332; National Institutes of Health (NIH) Grant T32 EB002103-24 from the National Institute of Biomedical Imaging and Bioengineering (NIBIB)

To assess the effect of electrode position on the amplitude and latency of ocular vestibular evoked myogenic potentials (oVEMPs) produced by air-conducted (AC) sound with a view to optimisation of the recording paradigm.Eight otologically normal subjects (16 ears) were stimulated by 500 Hz AC tone bursts at 95 dBnHL; oVEMP traces were recorded below the eye contralateral to the acoustic stimulation. Five independent oVEMP measurements were recorded with the active electrode in equally spaced positions in the infra-orbital plane relative to a reference electrode positioned 2 cm below the lower lid in the orbital midline. These measurements included the accepted standard-montage in which the electrodes were positioned vertically above and below each other in the orbital midline. A further recording was made using a belly-tendon montage with reference to the inferior oblique muscle.Of the six recording paradigms tested the largest amplitude oVEMP response was found using the belly-tendon montage with an n10 average of 5.67 ± 3.42 μV (sd). This was significantly larger than the amplitude recorded using the standard-montage (p0.01). With the reference electrode in the orbital midline, the position of the active electrode in the infra-orbital plane was found to significantly alter the response magnitude. As the active electrode was moved laterally the response reduced in amplitude, however when moved medially the response polarity reversed indicating the existence of a null-point at which no response was present.The location of oVEMP recording electrodes significantly alters the response amplitude. Whilst the standard-montage provides a reasonable method for recording oVEMPs, the belly-tendon montage results in a significantly larger amplitude response. Furthermore medial and lateral variations in the position of the active electrode using the standard-montage significantly affect the magnitude and polarity of the response.The standard-montage used for recording oVEMPs is sensitive to the placement of the active electrode. Small variations in position result in significant changes in the n(10) amplitude and this may account for the variability reported in the literature. Using the belly-tendon montage, larger amplitude responses can be elicited which may improve the robustness with which oVEMPs can be collected. However this enhancement in response amplitude must be balanced against the increased possibility of signal contamination from neighbouring extraocular muscles.

Objective To measure the frequency dynamics of cervical and ocular vestibular evoked myogenic potentials in healthy subjects and patients with Meniere's disease. Study design A prospective cohort study. Setting A university teaching hospital. Subjects Eight healthy volunteers (16 ears) and 12 adult patients with unilateral Meniere's disease (8 with definite disease and 4 with probable disease) by American Academy of Otolaryngology - Head and Neck Surgery diagnostic criteria. Interventions Cervical and ocular vestibular evoked myogenic potentials generated by tone bursts at 250, 500, 750, 1,000, 1,500, 2,000, 3,000, and 4,000 Hz were measured in both groups. Main outcome measures The frequency sensitivity of both the cervical and ocular vestibular evoked myogenic potentials, as evaluated by p13-n23 and n10 amplitudes in healthy ears and in ears affected and not affected by Meniere's disease. Results Cervical and ocular vestibular evoked myogenic potentials were present in all ears tested. In the healthy volunteers, the acoustic stimulus frequency at which the response amplitudes were largest was 500 Hz. This shifted to higher frequencies in patients with definite Meniere's disease for both measurements, with the effect being more pronounced for ocular vestibular evoked myogenic potentials. The shift was less marked in the probable Meniere's group and was absent in the unaffected ears of the Meniere's patients. Conclusion Meniere's ears display alterations in cervical and ocular vestibular evoked myogenic potentials tuning responses with changes in the latter being more prominent. These findings indicate that the disease process affects both the otolith organs but may have an enhanced effect on the utricle. We propose that this more dominant affect may relate to the anatomical configuration of the utricle.

The US Army is investigating the use of composite materials to deliver lightweight and more effective armor protection systems to soldiers and other army assets. However, widespread use of such hybrid armor will require a reliable but fast NDE methodology to ensure integrity of these components during manufacturing and while in service. Traditional ultrasonic inspection of such hybrid armor structures may prove to be very effective, but point‐by‐point ultrasonic scanning is inherently time‐consuming and manufacturing slowdowns could develop in high‐volume production of such armor systems. In this paper, we report on the application of acoustography for the NDE of hybrid armor structures. Acoustography differs from conventional ultrasonic testing in that test objects are inspected in full field, analogously to real time x‐ray imaging. The approach uses a novel, super high resolution large area acousto‐optic (AO) sensor, which allows image formation through simple ultrasound shadow casting, analogous to x‐ray image formation. This NDE approach offers significant inspection speed advantage over conventional point‐by‐point ultrasonic scanning procedures and is well‐suited for high volume production. We will report initial results on a number of hybrid armor plate specimens employing composite materials that are being investigated by the US Army. Acoustography NDE results will also be verified using other complimentary NDE methods.

Acoustography is a full-field ultrasonic imaging process where a high resolution 2D acousto-optic sensor based on liquid crystal technology is employed to directly convert the ultrasound into a visual image in near real time. Unprocessed acoustography images typically suffer from non-uniformity due to spatial variations in the optical brightness response of the acousto-optic sensor field to ultrasonic intensity. Additionally, dynamic range of the acousto-optic sensor is limited to approximately 20 to 30 db. The nonuniformity and dynamic range limitation can result in difficulty in acoustography image interpretation, impracticality for large field application, and difficulty for use on samples having a wide range of attenuation. The approach of this ongoing study is to apply various methodologies that address these limitations in hopes of extending the usefulness and applications of acoustoography for nondestructive testing. This article shows initial results of methodologies developed to correct for image non-uniformity and explains the proposed approach to extend the dynamic range of acoustography images.

This paper presents the results of a comparison study of three ultrasonic nondestructive evaluation (NDE) methods applied to polymer matrix composite (PMC) specimens subjected to impact damage. Samples mainly consisted of various thicknesses of graphite/epoxy coupon panels impacted with various energy levels. Traditional pulse-echo and through transmission ultrasonic c-scan techniques were applied to impacted samples and served as the basis for comparison. Specimens were then inspected using acoustography, a large field ultrasonic inspection technique that is analogous to real-time X-ray imaging. Acoustography utilizes a unique, wide area two-dimensional (2-D) detector, called an acousto-optic (AO) sensor, to directly convert ultrasound into visual images; much like an image intensifier in real-time radiography. Finally, a newly developed guided wave scanning system was utilized to inspect the same set of samples. This system uses two transducers in a pitch catch configuration to examine the total (multi-mode) ultrasonic response in its inspection analysis. Several time- and frequency-domain parameters are calculated from the ultrasonic guided wave signal at each scan location to form images. Results are presented for all of the methods demonstrating each technique's detection capabilities and highlighting their advantages and disadvantages.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The replacement of chemical batteries with composite flywheels offers many potential advantages in space applications. Before such flywheels can be successfully employed, it is imperative to ensure their integrity using NDE techniques. Previously, the use of traditional C-scan for the NDE of flywheels was compared to Scanning Ultrasonic Spectroscopy. However, both C-scan and scanning ultrasonic spectroscopy are point-by-point inspection techniques, and are thus inherently limited in inspection speed. In this paper, the application of Acoustography for the NDE of flywheels is reported. Acoustography provides an efficient and economical alternative to point-by-point ultrasonic scanning; in this approach a novel, wide area (AO) sensor is employed to provide full-field, real time ultrasonic images similar to x-ray imaging, significantly decreasing the required inspection time. Side by side images generated using Acoustography and traditional C-scan techniques for Plexiglas cylinder and a composite ring standard (both with known defects) are presented.

Many small composite parts undergo manual pulse-echo scan because 1) the set-up time for and automated scan is unjustifiably long and 2) the automated scan does not provide the flexibility to cope with frequent angle changes in a complex geometry part. Manual scans can be time consuming, laborious, and are prone to errors due to operator fatigue and subjectivity. What is required is a full-field ultrasonic inspection system analogous to real time radiography that allows the operator to perform ultrasonic inspection by manipulating the part under a systems field of view. In this paper, we will present an acoustography-based ultrasonic inspection system developed under a SBIR (Small Business Innovation Research) award that is bringing this vision to into reality. Acoustography is the ultrasonic analog of radiography and photography. A unique, wide area 2D detector, called acousto-optic (AO) sensor, is used to directly convert ultrasound into visual images; much like a fluorescent screen is able to convert x-rays into visual images. It offers the potential for providing the NDT engineer with a large field of view (e.g. 6”x 6” or larger) and a capability to inspect complex shaped parts in real time.

Acoustography is the ultrasonic analog of radiography and photography. A unique 2D detector, called acousto-optic (AO) sensor, is used that is capable of directly converting ultrasound into visual images; much like a fluorescent screen is able to convert x-rays into a visual image. The AO sensor offers exceptionally high resolution and can be fabricated to have a large area. This allows image formation through simple shadow casting (analogous to x-ray image formation) or with acoustic lense (analogous to a photographic or video camera). This paper will report on several new developments, which could allow acoustography to provide a simpler more cost-effective alternative to conventional ultrasonic testing.

Purpose: To characterize the dynamic response of a novel acousto-optic (AO) liquid crystal detector for high-resolution transmission ultrasound breast imaging. Transient and steady-state lesion contrast were investigated to identify optimal transducer settings for our prototype imaging system consistent with the FDA limits of 1 W/cm2 and 50 J/cm2 on the incident acoustic intensity and the transmitted acoustic energy flux density. Methods: We have developed a full-field transmission ultrasound breast imaging system that uses monochromatic plane-wave illumination to acquire projection images of the compressed breast. The acoustic intensity transmitted through the breast is converted into a visual image by a proprietary liquid crystal detector operating on the basis of the AO effect. The dynamic response of the AO detector in the absence of an imaged breast was recorded by a CCD camera as a function of the acoustic field intensity and the detector exposure time. Additionally, a stereotactic needle biopsy breast phantom was used to investigate the change in opaque lesion contrast with increasing exposure time for a range of incident acoustic field intensities. Results: Using transducer voltages between 0.3 V and 0.8 V and exposure times of 3 minutes, a unique one-to-one mapping of incident acoustic intensity to steady-state optical brightness in the AO detector was observed. A transfer curve mapping acoustic intensity to steady-state optical brightness shows a high-contrast region analogous to the linear portion of the Hurter-Driffield curves of radiography. Using transducer voltages between 1 V and 1.75 V and exposure times of 90 s, the lesion contrast study demonstrated increasing lesion contrast with increasing breast exposure time and acoustic field intensity. Lesion-to-background contrast on the order of 0.80 was observed. Conclusion: Maximal lesion contrast in our prototype system can be obtained using the highest acoustic field intensity and the longest breast exposure time allowable under FDA standards. Department of Defense (DOD) Breast Cancer Research Program IDEA Award W81XWH-11-1-0332; National Institutes of Health (NIH) Grant T32 EB002103-21 from the National Institute of Biomedical Imaging and Bioengineering (NIBIB)

Acoustography is a full field, large area ultrasonic imaging method where a novel, wide area acousto-optic (AO) sensor is employed to form ultrasonic images similarly to real-time x-ray imaging. The AO sensor converts ultrasound directly into a visual image due to the inherent acousto-optic property of a proprietary mesophase material contained in the AO sensor. The AO sensor also offers exceptionally high pixel resolution, as a continuous layer of the mesophase material, with sensing molecules on the order of 20 Angstroms in size, senses the ultrasound. This paper will report on progress being made under a SBIR project to develop acoustography as an efficient and economical alternative to conventional point-by-point ultrasonic scanning (e.g. A-scan, C-scan).

Military and commercial aircraft structures are being fielded well beyond their designed life cycle, resulting in escalating maintenance costs. The principle driver behind these costs is the need to nondestructively interrogate large areas to detect and quantify anomalies such as corrosion, cracks, and delaminations. Manual ultrasonic techniques are routinely applied to inspect aircraft structures, but these techniques are time consuming, laborious, and are prone to errors such as operator fatigue and subjectivity. Automated ultrasonic systems require costly, complex scanning systems that are often difficult to adapt to complex shaped structures. Acoustography can provide full-field ultrasonic images in near real-time, making it a suitable method for high-speed, wide area inspection applications. This paper will report on progress being made toward developing acoustography for NDE of aging aircraft structures.

The objective of this paper is to provide details on the development of a novel acousto-optic sensor that can be utilized to nondestructively evaluate materials and components in near real-time. The acousto-optic sensor, which is the basis for Acoustography, provides wide-area, near real-time ultrasonic attenuation maps that can be analyzed to detect anomalies such as cracks, delaminations, and porosity. Details on applying Acoustography to inspect complex shaped parts will be provided. Future work in the area of Acoustography will also be presented.

A series of epoxy carbon fiber development panels manufactured as part of a BAE SYSTEMS, Airbus, Composite Wing Development program were evaluated using Acoustography, a new ultrasonic Non Destructive Evaluation (NDE) method being developed by Santec Systems Inc, as an alternative to the conventional point-by-point ultrasonic C-scan. This study provides details on a novel wide area Acousto-optic (AO) sensor that can be used to nondestructively evaluate materials and components in near real-time. A description of the technology and how it compares to conventional ultrasonic methods is provided. The results of 4 experiments are also provided. The first experiment involves performing ultrasonic and Acoustography tests on thick graphite/epoxy composite panels that have embedded inclusions of known sizes. The objective of this experiment is to determine if the capabilities (i.e. resolution) of Acoustography are comparable to those of conventional ultrasonic techniques. The second experiment involves applying ultrasonics and Acoustography to evaluate a 10 mm thick graphite/epoxy composite panel containing defects associated with the manufacturing process. The third and fourth experiments detail the inspection of complex shaped composite parts representative of aerospace applications. Effort has been conducted towards demonstrating the effectiveness of the technology and establishing a baseline for projected inspection times.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The objective of this study is to provide details on a novel wide area acousto-optic (AO) sensor that can be used to nondestructively evaluate materials and components in near real-time. A description of the technology and how it compares to conventional ultrasonic methods is provided. The results from three experiments provide details on how acoustography compares to conventional ultrasonics when applied to the inspection of composite parts. The first experiment involves performing ultrasonic and acoustography tests on a standard graphite/epoxy composite panel that has embedded inclusions of known sizes. The objective of this experiment is to determine if the capabilities (i.e. resolution) of acoustography are comparable to those of conventional ultrasonic techniques. The second experiment applied acoustography and ultrasonic techniques to evaluate the effects of low impact damage in composite materials. The third experiment involves applying ultrasonics and acoustography to evaluate a complex shaped composite part. The purpose of this experiment is to show the strengths and weaknesses of both techniques as applied to real world problems.

Liquid crystals have been investigated for acoustic imaging purposes for more than 20 years, however, their practicality has become apparent only recently through a number of technological developments. This has led to the development of the world's first liquid crystal based acoustic imaging system, which is finding commercial applications. This paper will discuss some of the fundamental technical progress that was needed to make liquid crystal based acoustic imaging a reality. Numerous current and potential uses of the liquid crystal based acoustic imaging approach will be discussed, including nondestructive testing, underwater mine detection, medical imaging, etc.

Acoustography is being developed as an alternative to conventional point-by-point ultrasonic scanning commonly employed for composite inspection. In acoustography, an area detector is used to produce full-field images of the test component in near real time, which makes the method suitable for providing rapid ultrasonic inspection of composites. Although the possibility of using acoustography to inspect composites has recently been demonstrated, a side-by-side comparison of acoustography with conventional ultrasonic scanning has not been made. In this work we will report on studies conducted toward establishing a direct comparison between acoustography and conventional ultrasonic scanning.

Acoustography provides an alternative to the conventional point-by-point ultrasonic scanning approach commonly used for composite inspection. In acoustography, an area detector (sonoplate) is employed for near real-time imaging of composites. In this paper, we report on the application of acoustography for ultrasonic inspection of tight-radii in composite components/specimens, where conventional point-by- point ultrasonic scanning may not be practical and/or cost- effective.

Purpose: To investigate the feasibility of using a limited number of multispectral transmission ultrasound images acquired with a novel full‐field liquid crystal ultrasonic detector to estimate the sizes of cystic and malignant breast lesions. Methods: In our prototype ultrasound imaging system, a high‐resolution liquid crystal detector measures the intensity of the acoustic field transmitted through the compressed breast. Projection images can be acquired at multiple transducer frequencies with several monochromatic sources. Assuming normal breast parenchyma containing either a simple breast cyst or infiltrating duct carcinoma, image data acquired at two or more transducer frequencies can potentially be used to estimate the size of the lesion present. The presence of electronic Gaussian noise precludes an exact lesion thickness determination; the lesion thickness can only be estimated with some uncertainty. We have used estimation theory to derive the Cramer‐Rao lower bound on the uncertainty of the thickness estimate for cystic and malignant lesions of variable sizes. Results: For a 1‐cm simple breast cyst and SNR of 50, an uncertainty in the estimated cyst thickness of 0.095 cm can be obtained using two transmission ultrasound breast images acquired with transducer frequencies of 5 and 5.508 MHz. For a malignant breast lesion of the same size and SNR of 50, an uncertainty in the lesion thickness estimate of 0.197 cm can be obtained using two breast images acquired with frequencies of 5 MHz and 5.462 MHz. In general, the lower bound on the precision of the thickness estimate is found to improve with increasing SNR and lesion size. Conclusion: For the cases considered, the Cramer‐Rao lower bound on the uncertainty of the thickness estimate is significantly less than the actual lesion size. Furthermore, the precision of the thickness estimate can be improved by using lower transducer frequencies, although diffraction artifacts might then become prohibitive. Department of Defense (DOD) Breast Cancer Research Program IDEA Award W81XWH‐11‐1‐0332

Acoustography provides an alternative to the conventional point-by-point scanning approach employed for ultrasonic inspection of composites. In acoustography, an acousto-optic area detector is employed for direct ultrasonic imaging of composites in near real time. In this work, we will report on the application of this approach for inspecting composites where the point-by-point approach may not be practical and/or cost-effective.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Benign paroxysmal positional vertigo (BPPV) is a common disorder caused by the dislocation of otoconia most commonly into the posterior canal. The primary symptoms are brief episodes of head-position related vertigo which may be accompanied by nausea and disequilibrium. BPPV is usually managed conservatively with excellent results, however in a small number of cases the symptoms can become persistent and incapacitating. The most common treatment in such cases involves the surgical occlusion of the canal. This procedure carries a small risk of post operative perilymph leakage via an iatrogenic fistula. In this paper we outline a case of a patient who developed a perilymph leak following occlusion surgery for intractable BPPV. We describe a novel surgical method that was used to close the fistula using a synthetic polymer based patch (TissuePatchDural90™), which has not been applied in the field of otology previously.

In this paper we will report on the use of a novel two‐dimensional acousto‐optic (2D AO) sensor as a simple, fast and cost‐effective method of mapping transducer fields, which could be useful for quality control and quality assurance (QC/QA) of diagnostic and therapeutic transducers. This capability could be particularly useful for monitoring power output of therapeutic transducers prior to administering ultrasound based thermo‐therapy treatment. It may also provide a quick tool for determining beam position and other transducer field characteristics such as propagation angle, beam diameter, divergence, and cross‐sectional uniformity. Current standard transducer field mapping practices requires point‐by‐point scanning over a ball reflector or a hydrophone to map the transducer field. This approach is tedious, requiring hours of scanning time to generate the full cross‐sectional and axial field distributions. The 2D AO system could overcome some of the drawbacks of current conventional scanning methodologies.

A product and method uses acousto-optic reflection-active media having an optical reflectivity which changes with changes in acoustic energy intensity interacting with the media to form images of defects in samples when the defects reflect acoustic energy differently from known acoustically reflecting parts of the samples.

There is disclosed herein an acoustic or ultrasonic power meter which includes a liquid crystal cell for detecting acoustic energy and a control circuit for applying an electric field to said cell. The liquid crystal cell includes a liquid crystal material having elongated molecules. The preferred liquid crystal is in the form of a layer of the nematic type which is homeotropically aligned. The elongated liquid crystal molecules exhibit positive dielectric anisotropy wherein the dielectric constant parallel to the molecule's axis is greater than the dielectric constant perpendicular to the molecule's axis. In the unexcited condition, the nematic layer is dark. In the ultrasonically excited condition, the nematic layer exhibits birefringence. A restoring electric force can be applied to the liquid crystal material to suppress the acoustically-induced birefringence condition of the cell to the dark appearance associated with the unexcited condition. The strength of the electric field required to suppress the birefringence is proportional to the acoustic intensity of the ultrasonic beam or acoustic field applied to the cell.

An acoustic imaging system which employs a liquid crystal cell for detecting acoustic energy and displaying an image. The cell includes a layer of liquid crystal material which is disposed between and encapsulated by a pair of cover members. At least one of the cover members is a laminated structure having at least two plies. The plies are of different materials and the thickness of each ply is governed by the expression n λ/2, where n is an integer, and λ is the wavelength of the acoustic energy in the cover materials. This structure enhances cell rigidity and the uniform of thickness of the liquid crystal layer in larger sized cells, while maintaining good transmission for energy angularly incident on the cell.

Kinetic studies confirm that the silver(I) ion-promoted reaction of disulphides with sulphinate ions proceeds via formation of a disulphide–Ag+ complex. Nucleophilic attack by sulphinate sulphur at the sulphenyl centre of the complex leads to silver alkyl sulphide and thiosulphonate. Under favourable conditions the 1 : 1 disulphide–silver complex can be isolated.

@ A movable, ultrasonic transducer array for use in an ultrasonic inspection system that employs a signal detector and display of the liquid crystal cell (18) type. The movable array uniformly insonifies the object (16) to be inspected and is particularly for inspecting large objects or large areas of an object. The array includes a plurality of sending or emitting transducers (14) which are held in substantially parallel alignment so that their transmission or radiation axes are parallel. The array is part of an assembly which includes a support (24, 26) for holding the transducers and a drive system (28 to 38) for moving the array and support along a predetermined path.

There is disclosed herein a method for producing a liquid crystal display or cell which has a liquid crystal film positioned between a pair of substrate members whose surfaces have been ultrasonically surface treated so as to cause the liquid crystal molecules to be aligned in a predetermined manner. The method includes ultrasonically treating the surface of the substrate which contacts the liquid crystal film so as to form microgrooves or striations. The surface is treated by immersing the substrate in a liquid bath, ultrasonically forming a column of cavitation bubbles which is directed to the substrate where the cavitation bubbles collapse on the substrate, and moving the substrate through the liquid at a predetermined speed so as to form microgrooves or striate the surface of the substrate. Using two such treated substrates, a liquid crystal cell is prepared in the form of a sandwich of substrate/liquid crystal/substrate.