Comparison of capabilities and limitations of endoscopes in endoscopic ear surgeries using 3D printed models.

PURPOSE: Endoscopic ear surgery has become a popular operative approach to treat middle ear diseases. Surgeons use either 0° or 30° endoscopes worldwide. The main aim of the work was to compare the properties of these two types of endoscopes. MATERIAL AND METHODS: Since this type of evaluation is hard to perform in vivo during the actual surgery, we designed 3D printed temporal bone models with different levels of complexity. The evaluation of endoscopes was based on image analysis or visibility of anatomical structures. RESULTS: The results show that a 30° endoscope offers a view of lateral walls from 4 mm distance, contrary to a 0° endoscope which cannot see lateral walls from this distance at all. On the other hand, visible area of the anterior wall is up to 40 % larger using 0° endoscope, compared to 30° endoscope. Angled endoscope distorts the picture and leads to the deterioration of the image. At commonly used distances above 5 mm from middle ear structures, resolution and image distortion is comparable between both endoscopes. CONCLUSIONS: Our results do not offer a definitive opinion on which endoscope is better for ear surgery. Both types of endoscopes have advantages and disadvantages, and the choice depends on the surgeon's personal preference and on the type of planned procedure.

Pupillography in contemporary sleep medicine - A narrative review.

Excessive daytime sleepiness (EDS) is a common symptom of sleep disorders such as narcolepsy, obstructive sleep apnea, and hypersomnia. The most common tools for assessing EDS are various specialized questionnaires such as Epworth Sleepiness Scale (ESS) and Stanford Sleepiness Scale (SSS). However, the scores obtained from self-rating questionnaires do not seem to measure physiological sleepiness but rather a more complex phenomenon of subjective sleepiness modulated by other factors such as motivation, expectation, and capability of self-perception. The golden standard for measuring physiological sleepiness and assessing EDS is the Multiple Sleep Latency Test (MSLT). However, MSLT is very time consuming and requires trained personnel and expensive equipment. Different method modifications are employed in various medical and industrial fields for different purposes. The infrared pupillography in darkness has the potential to measure objective physiological sleepiness, especially the Pupillographic Sleepiness Test (PST), which is the method of choice for pupillographic measurement of daytime sleepiness. The method has also been employed in several specific sleep disorders, outlining possible future usage. This narrative review summarizes the current state of knowledge on the relevance and usefulness of pupillography in sleep medicine.

Newly Designed 3D-Printed Sonication Test Cell Optimized for In Vitro Sonication Experiments.

OBJECTIVE: Precise control over the ultrasound field parameters experienced by biological samples during sonication experiments in vitro may be quite challenging. The main goal of this work was to outline an approach to construction of sonication test cells that would minimize the interaction between the test cells and ultrasound. METHODS: Optimal dimensions of the test cell were determined through measurements conducted in a water sonication tank using 3D-printed test objects. The offset of local acoustic intensity variability inside the sonication test cell was set to value of ±50% of the reference value (i.e., local acoustic intensity measured at last axial maximum in the free-field condition). The cytotoxicity of several materials used for 3D printing was determined using the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay. RESULTS: The sonication test cells were 3D printed from polylactic acid material, which was not toxic to the cells. Silicone membrane HT-6240, which was used to construct the bottom of the test cell, was found to reduce ultrasound energy minimally. Final ultrasound profiles inside the sonication test cells indicated the desired variability of local acoustic intensity. The cell viability in our sonication test cell was comparable to that of commercial culture plates with bottoms constructed with silicone membrane. CONCLUSION: An approach to construction of sonication test cells minimizing the interaction of the test cell and ultrasound has been outlined.

Optimal Light Source Intensity Setting in Endoscopic Ear Surgery.

HYPOTHESIS: Higher light intensity settings do not yield improved image quality in endoscopic ear surgery. BACKGROUND: Light intensity is a parameter with major impact on the quality of digital images. For ear surgery, light produces heat associated with a thermal risk to ear structures and the light source setting should be accordingly optimized. METHODS: Several series of still images were acquired during live middle ear surgery, using cadaveric and plastic temporal bone models and with three-dimensional printed models. Images obtained under varying light intensities were compared with the image acquired at maximum intensity of a light emitting diode light source. We analyzed digital image brightness and noise using quantitative methods. RESULTS: Our measurements revealed significantly decreased image brightness with light intensities set below 20% with an increase in noise at light intensities lower than 30%. CONCLUSION: The optimal light source setting corresponded to 30% intensity in our experimental set-up. Special attention should be given to those cases where faster image quality degradation is expected (dark or bloody scenes or larger cavities). The results were strongly dependent on the equipment used. The methods described in this study can serve as a general guide for determining the optimal light source setting in any specific set-up.

Far field during sonication experiments in vitro - Is it really far enough?

In many in vitro experiments studying ultrasound bioeffects the sonicated samples are placed to far field with intention of exposing them to as uniform ultrasound field as possible. The main aim of this work is to assess whether the sonicated samples really experience what they are believed to. Also we would like to suggest basic rules for construction of sonication vessels. We used 3.5 MHz and 7 MHz ultrasound transducers for measurements. We measured ultrasound field inside and behind common culture plates and special 3D printed plates placed to last axial maximum in water sonication tank with use of a needle hydrophone. Our results show that even though the sonication vessels with sonicated samples are placed into far field, the sonicated samples are actually exposed to some kind of a near field pattern which develops due to the interaction between ultrasound and well of culture plate. The variability of local acoustic intensity can reach up to several hundreds of percent. Our results are also supported by theoretical calculation and software for simulation of ultrasound fields. Even though the sonicated samples may have actually been exposed to some kind of near field pattern in many past studies, the whole phenomenon of creation of near field pattern can be controlled to some extent for future studies. Thus, we suggest that the sonication vessel should always be designed for particular ultrasound transducer.

Shear wave elastography in diffuse thyroid disease.

AIM: Our aim was to examine the contribution of shear wave elastography to ultrasonographic assessment in diffuse thyroid disease, specifically to evaluate the stiffness of the thyroid gland in diffuse thyroid disease and compare it with healthy controls. METHODS: A total of 46 patients with diffuse thyroid disease were examined clinically, by conventional ultrasound, and shear wave elastography. The conventional ultrasound parameters followed were: volume, margin quality, presence of nodules, and vascularisation. We measured the mean, minimum, and maximum stiffnesses by shear wave elastography. Results were correlated with values in 128 healthy subjects. RESULTS: Patients with diffuse thyroid disease had significantly higher mean and maximal stiffnesses of the thyroid gland: 12.5 ± 5 kPa and 35.3 ± 12.8 kPa, respectively, and lower minimal stiffness: 0.5 ± 0.6 kPa than the healthy control group with mean, maximal, and minimal values of 9.5 ± 3.6 kPa, 22.5 ± 7.3 kPa, and 2.2 ± 2.1 kPa (P<0.001). Stiffness values were positively correlated with BMI and volume of the thyroid; they did not correlate with margin quality, presence of nodules nor vascularisation. Compared with healthy volunteers, thyroid glands of patients with diffuse thyroid disease had a blurred margin more frequently and the amount of nodules and vascularisation were higher. Patients with Graves-Basedow disease did not have significantly different mean, maximal, nor minimal stiffnesses than those with thyroiditis. CONCLUSION: Both mean and maximal stiffness of the thyroid gland are significantly higher in diffuse thyroid disease than in the healthy population, while minimal stiffness is lower.

Therapeutic ultrasound experiments in vitro: Review of factors influencing outcomes and reproducibility.

Current in vitro sonication experiments show immense variability in experimental set-ups and methods used. As a result, there is uncertainty in the ultrasound field parameters experienced by sonicated samples, poor reproducibility of these experiments and thus reduced scientific value of the results obtained. The scope of this narrative review is to briefly describe mechanisms of action of ultrasound, list the most frequently used experimental set-ups and focus on a description of factors influencing the outcomes and reproducibility of these experiments. The factors assessed include: proper reporting of ultrasound exposure parameters, experimental geometry, coupling medium quality, influence of culture vessels, formation of standing waves, motion/rotation of the sonicated sample and the characteristics of the sample itself. In the discussion we describe pros and cons of particular exposure geometries and factors, and make a few recommendations as to how to increase the reproducibility and validity of the experiments performed.

The Role of Ultrasound and Shear-Wave Elastography in Evaluation of Cervical Lymph Nodes.

AIM: To evaluate the prognostic value of ultrasound and shear-wave elastography (SWE) in diagnosing malignant cervical lymph nodes. METHODS: A total of 99 patients with enlarged lymph nodes (99 lymph nodes presenting as a neck mass) were examined clinically with conventional ultrasound including Doppler examination and shear-wave elastography. The results of the examinations were compared with the final diagnosis. RESULTS: There were 43 benign and 56 malignant lymph nodes in our cohort. Age and sex were significant predictors of malignancy. The standard ultrasound parameters-node size, long/short axis ratio, hilum, vascularization, and the presence of microcalcifications-were also statistically significant. Lymph node volume combined with age showed the best predictive power. The maximum stiffness found on SWE was also a significant predictor of malignancy. The combination of epidemiologic, classic ultrasound, and elastographic parameters yielded the highest sensitivity and specificity in the prediction of malignancy; however, the additional impact of elastographic parameters was low. CONCLUSION: A combination of epidemiologic and classic ultrasound parameters can discriminate between malignant and benign lymph nodes with satisfactory sensitivity and specificity. Examining the stiffness of lymph nodes by means of SWE does not add much new predictive power.

Evaluation of the Effect of Tissue Compression on the Results of Shear Wave Elastography Measurements.

Shear wave imaging is considered to be more precise and less operator dependent when compared with strain imaging. It enables quantitative and reproducible data (Young's modulus of the imaged tissue). However, results of shear wave imaging can be affected by a variety of different factors. The aim of this study is to evaluate the effect of the pressure applied by the ultrasound probe during examination on the measured values of Young's modulus. The effect of the tissue compression on the results of the real-time shear wave elastography was evaluated via the gelatine phantom measurements, via the ex vivo experiments with pig liver, and via the in vivo measurements of the thyroid gland stiffness on healthy volunteers. The results of our measurements confirmed that the measured value of Young's modulus increases with the increasing pressure applied on the imaged object. The highest increase was observed during the ex vivo experiments (400%), and the lowest increase was detected in the case of the phantom measurements (8%). A two- to threefold increase in Young's modulus was observed between the minimum and maximum pressure in the case of the in vivo elastography measurements of thyroid gland. The Veronda-Westman theoretical model was used for the description of the tissue nonlinearity. We conclude that tissue compression by the force exerted on the probe can significantly affect the results of the real-time shear wave elastography measurements. Minimum pressure should be used when measuring the absolute value of Young's modulus of superficial organs.

Differential Diagnosis of Parotid Gland Tumors: Role of Shear Wave Elastography.

AIM: To create a predictive score for the discrimination between benign and malignant parotid tumors using elastographic parameters and to compare its sensitivity and specificity with standard ultrasound. METHODS: A total of 124 patients with parotid gland lesions for whom surgery was planned were examined using conventional ultrasound, Doppler examination, and shear wave elastography. Results of the examinations were compared with those ones of histology. RESULTS: There were 96 benign and 28 malignant lesions in our cohort. Blurred tumor margin alone proved to be an excellent predictor of malignancy with the sensitivity of 79% and specificity of 97%. Enlarged cervical lymph nodes, tumor vascularisation, microcalcifications presence, homogeneous echogenicity, and bilateral occurrence also discriminated between benign and malignant tumors. However, their inclusion in a predictive model did not improve its performance. Elastographic parameters (the stiffness maxima and minima ratio being the best) also exhibited significant differences between benign and malignant tumors, but again, their inclusion did not significantly improve the predictive power of the blurred margin classifier. CONCLUSION: Even though elastography satisfactorily distinguishes benign from malignant lesions on its own, it hardly provides any additional value in evaluation of biological character of parotid gland tumors when used as an adjunct to regular ultrasound examination.

Shear wave elastography parameters of normal soft tissues of the neck.

BACKGROUND: Shear wave elastography is a relatively new method of quantitative measurement of tissue elasticity. Assuming that malignant lesions are stiffer than benign ones, elastography may provide supplementary information for their discrimination. However, potential confounding factors impacting tissue stiffness should be investigated first. AIMS: The objective of this study was to measure the stiffness of selected tissues of the head and neck in a normal population and to evaluate its relationship to age, sex, and body mass index. METHODS: Stiffness of the thyroid, submandibular and parotid glands, masseter and sternocleidomastoid muscles, and cervical lymph nodes was measured bilaterally in 128 healthy volunteers (83 female and 45 male). At least 20 subjects in each decade of life (20-29, 30-39‥, 70+) were enrolled. Shear wave elastography was performed by a single radiologist in all the subjects. The stiffnesses obtained were correlated with age, sex, and body mass index. RESULTS: The mean stiffness was 9.5 ± 3.6 kPa for the thyroid, 9.5 ± 4.6 kPa for the lymph node, 11.0 ± 3.4 kPa for the submandibular gland, 9.0 ± 3.5 kPa for the parotid gland, 9.9 ± 4.1 kPa for the sternocleidomastoid, and 10.0 ± 4.3 kPa for the masseter muscle. A slight general decrease in stiffness with increasing age was found. BMI and weight had a small impact on the minimum and maximum stiffness values. The sex of the subject did not affect elasticity. CONCLUSION: The mean stiffness of healthy head and neck organs has a relatively narrow distribution around 11 kPa. The changes of stiffness with age, BMI, and weight that were identified are too small to have clinical impact.

Study of photodynamic, sonodynamic and antioxidative influence on HeLa cell line.

Photodynamic treatment (PDT) in combination with sonodynamic treatment (SDT) can be used as suitable methods to treat malignant and benign diseases or combat resistant bacteria. Both methods affect the production of reactive oxygen species (ROS). On the other hand, antioxidants are useful for cell protection against ROS. This work was aimed to study the effect of PDT and SDT treatments on the HeLa cell line using antioxidant Pronalen Sensitive Skin as a protection from free radicals in the cells. We evaluated the effect of sensitizer ClAlPcS2 using battery of in vitro methods, including MTT assay, kinetic production of ROS, mitochondrial membrane potential change, type of cell death and microscopic analysis. Ultrasound treatment was observed to increase the production of ROS, only in combination with PDT, particularly at higher concentrations of ClAlPcS2. The added antioxidant acts as protection against free radicals and has potential as a dietary supplement against aging or free radicals. The results of study suggested that ClAlPcS2 could be used as a potential photosensitizer for treatment of a specific type of cancers.

The effect of dead elements on the accuracy of Doppler ultrasound measurements.

The objective of this study is to investigate the effect of multiple dead elements in an ultrasound probe on the accuracy of Doppler ultrasound measurements. For this work, we used a specially designed ultrasound imaging system, the Ultrasonix Sonix RP, that provides the user with the ability to disable selected elements in the probe. Using fully functional convex, linear, and phased array probes, we established a performance baseline by measuring the parameters of a laminar parabolic flow profile. These same parameters were then measured using probes with 1 to 10 disabled elements. The acquired velocity spectra from the functional probes and the probes with disabled elements were then analyzed to determine the overall Doppler power, maximum flow velocity, and average flow velocity. Color Flow Doppler images were also evaluated in a similar manner. The analysis of the Doppler spectra indicates that the overall Doppler power as well as the detected maximum and average velocities decrease with the increasing number of disabled elements. With multiple disabled elements, decreases in the detected maximum and average velocities greater than 20% were recorded. Similar results were also observed with Color Flow Doppler measurements. Our results confirmed that the degradation of the ultrasound probe through the loss of viable elements will negatively affect the quality of the Doppler-derived diagnostic information. We conclude that the results of Doppler measurements cannot be considered accurate or reliable if there are four or more contiguous dead elements in any given probe.