15 research outputs found
SkullGAN: Synthetic Skull CT Generation with Generative Adversarial Networks
Deep learning offers potential for various healthcare applications involving
the human skull but requires extensive datasets of curated medical images. To
overcome this challenge, we propose SkullGAN, a generative adversarial network
(GAN), to create large datasets of synthetic skull CT slices, reducing reliance
on real images and accelerating the integration of machine learning into
healthcare. In our method, CT slices of 38 subjects were fed to SkullGAN, a
neural network comprising over 200 million parameters. The synthetic skull
images generated were evaluated based on three quantitative radiological
features: skull density ratio (SDR), mean thickness, and mean intensity. They
were further analyzed using t-distributed stochastic neighbor embedding (t-SNE)
and by applying the SkullGAN discriminator as a classifier. The results showed
that SkullGAN-generated images demonstrated similar key quantitative
radiological features to real skulls. Further definitive analysis was
undertaken by applying the discriminator of SkullGAN, where the SkullGAN
discriminator classified 56.5% of a test set of real skull images and 55.9% of
the SkullGAN-generated images as reals (the theoretical optimum being 50%),
demonstrating that the SkullGAN-generated skull set is indistinguishable from
the real skull set - within the limits of our nonlinear classifier. Therefore,
SkullGAN makes it possible to generate large numbers of synthetic skull CT
segments, necessary for training neural networks for medical applications
involving the human skull. This mitigates challenges associated with preparing
large, high-quality training datasets, such as access, capital, time, and the
need for domain expertise.Comment: The first two authors contributed equall
Distribution characteristics of air-bone gaps : evidence of bias in manual audiometry
OBJECTIVES : Five databases were mined to examine distributions of airbone
gaps obtained by automated and manual audiometry. Differences
in distribution characteristics were examined for evidence of influences
unrelated to the audibility of test signals.
DESIGN : The databases provided air- and bone-conduction thresholds
that permitted examination of air-bone gap distributions that were free
of ceiling and floor effects. Cases with conductive hearing loss were
eliminated based on air-bone gaps, tympanometry, and otoscopy, when
available. The analysis is based on 2,378,921 threshold determinations
from 721,831 subjects from five databases.
RESULTS : Automated audiometry produced air-bone gaps that were normally
distributed suggesting that air- and bone-conduction thresholds
are normally distributed. Manual audiometry produced air-bone gaps
that were not normally distributed and show evidence of biasing effects
of assumptions of expected results. In one database, the form of the
distributions showed evidence of inclusion of conductive hearing losses.
CONCLUSIONS : Thresholds obtained by manual audiometry show tester
bias effects from assumptions of the patient’s hearing loss characteristics.
Tester bias artificially reduces the variance of bone-conduction
thresholds and the resulting air-bone gaps. Because the automated
method is free of bias from assumptions of expected results, these distributions
are hypothesized to reflect the true variability of air- and boneconduction
thresholds and the resulting air-bone gaps.Portions of this work were supported by Grant RC3DC010986 from the
National Institute of Deafness and Other Communication Disorders and
by contract No. VA118-12-C-0029 from the US Department of Veterans
Affairs. The Rehabilitation Research and Development Service of the US
Department of Veterans Affairs supported this work through the Auditory
and Vestibular Dysfunction Research Enhancement Award Program
(REAP) and a Senior Research Career Scientist award to the second author.http://journals.lww.com/ear-hearing2017-03-31hb2016Speech-Language Pathology and Audiolog
Distribution characteristics of normal pure-tone thresholds
OBJECTIVE : This study examined the statistical properties of normal air-conduction thresholds obtained with automated and manual audiometry
to test the hypothesis that thresholds are normally distributed and to examine the distributions for evidence of bias in manual
testing. DESIGN : Four databases were mined for normal thresholds. One contained audiograms obtained with an automated method. The
other three were obtained with manual audiometry. Frequency distributions were examined for four test frequencies (250, 500, 1000,
and 2000 Hz). STUDY SAMPLE : The analysis is based on 317 569 threshold determinations of 80 547 subjects from four clinical databases.
RESULTS : Frequency distributions of thresholds obtained with automated audiometry are normal in form. Corrected for age, the mean
thresholds are within 1.5 dB of reference equivalent threshold sound pressure levels. Frequency distributions of thresholds obtained by
manual audiometry are shifted toward higher thresholds. Two of the three datasets obtained by manual audiometry are positively skewed.
CONCLUSIONS : The positive shift and skew of the manual audiometry data may result from tester bias. The striking scarcity of thresholds
below 0 dB HL suggests that audiologists place less importance on identifying low thresholds than they do for higher-level thresholds.
We refer to this as the Good enough bias and suggest that it may be responsible for differences in distributions of thresholds obtained by
automated and manual audiometry.By grant RC3DC010986 from the National Institutes of Deafness and Other Communication Disorders. The Rehabilitation Research and Development Service of the U.S. Department of Veterans Affairs supported this work through the
Auditory and Vestibular Dysfunction Research Enhancement Award Program (REAP) and a Senior Research Career Scientist.http://www.tandfonline.com/loi/iija202016-05-31hb2016Speech-Language Pathology and Audiolog
Comprehensive measures of sound exposures in cinemas using smart phones
OBJECTIVES
Sensorineural hearing loss from sound overexposure has a considerable prevalence. Identification of sound hazards is crucial, as prevention, due to a lack of definitive therapies, is the sole alternative to hearing aids. One subjectively loud, yet little studied, potential sound hazard is movie theaters. This study uses smart phones to evaluate their applicability as a widely available, validated sound pressure level (SPL) meter. Therefore, this study measures sound levels in movie theaters to determine whether sound levels exceed safe occupational noise exposure limits and whether sound levels in movie theaters differ as a function of movie, movie theater, presentation time, and seat location within the theater.
DESIGN
Six smart phones with an SPL meter software application were calibrated with a precision SPL meter and validated as an SPL meter. Additionally, three different smart phone generations were measured in comparison to an integrating SPL meter. Two different movies, an action movie and a children's movie, were measured six times each in 10 different venues (n = 117). To maximize representativeness, movies were selected focusing on large release productions with probable high attendance. Movie theaters were selected in the San Francisco, CA, area based on whether they screened both chosen movies and to represent the largest variety of theater proprietors. Measurements were analyzed in regard to differences between theaters, location within the theater, movie, as well as presentation time and day as indirect indicator of film attendance.
RESULTS
The smart phone measurements demonstrated high accuracy and reliability. Overall, sound levels in movie theaters do not exceed safe exposure limits by occupational standards. Sound levels vary significantly across theaters and demonstrated statistically significant higher sound levels and exposures in the action movie compared to the children's movie. Sound levels decrease with distance from the screen. However, no influence on time of day or day of the week as indirect indicator of film attendance could be found.
CONCLUSIONS
Calibrated smart phones with an appropriate software application as used in this study can be utilized as a validated SPL meter. Because of the wide availability, smart phones in combination with the software application can provide high quantity recreational sound exposure measurements, which can facilitate the identification of potential noise hazards. Sound levels in movie theaters decrease with distance to the screen, but do not exceed safe occupational noise exposure limits. Additionally, there are significant differences in sound levels across movie theaters and movies, but not in presentation time
Anatomic measures of upper airway structures in obstructive sleep apnea
Objective: Determine if anatomic dimensions of airway structures are associated with airway obstruction in obstructive sleep apnea (OSA) patients. Methods: Twenty-eight subjects with (n = 14) and without (n = 14) OSA as determined by clinical symptoms and sleep studies; volunteer sample. Skeletal and soft tissue dimensions were measured from radiocephalometry and magnetic resonance imaging. The soft palate thickness, mandibular plane-hyoid (MP-H) distance, posterior airway space (PAS) diameters and area, and tongue volume were calculated. Results: Compared to controls, the OSA group demonstrated a significantly longer MP-H distance (P = 0.009) and shorter nasal PAS diameter (P = 0.02). The PAS area was smaller (P = 0.002) and tongue volume larger in the OSA group (P = 0.004). The MP-H distance, PAS measurements, and tongue volume are of clinical relevance in OSA patients. Conclusions: A long MP-H distance, and small PAS diameters and area are significant anatomic measures in OSA; however the most substantial parameter found was a large tongue volume. Keywords: Obstructive sleep apnea, Anatomy, Anatomic measurement, Posterior airway space, Tongue volume, Hyoid positio
Distribution characteristics of normal pure-tone thresholds
OBJECTIVE : This study examined the statistical properties of normal air-conduction thresholds obtained with automated and manual audiometry
to test the hypothesis that thresholds are normally distributed and to examine the distributions for evidence of bias in manual
testing. DESIGN : Four databases were mined for normal thresholds. One contained audiograms obtained with an automated method. The
other three were obtained with manual audiometry. Frequency distributions were examined for four test frequencies (250, 500, 1000,
and 2000 Hz). STUDY SAMPLE : The analysis is based on 317 569 threshold determinations of 80 547 subjects from four clinical databases.
RESULTS : Frequency distributions of thresholds obtained with automated audiometry are normal in form. Corrected for age, the mean
thresholds are within 1.5 dB of reference equivalent threshold sound pressure levels. Frequency distributions of thresholds obtained by
manual audiometry are shifted toward higher thresholds. Two of the three datasets obtained by manual audiometry are positively skewed.
CONCLUSIONS : The positive shift and skew of the manual audiometry data may result from tester bias. The striking scarcity of thresholds
below 0 dB HL suggests that audiologists place less importance on identifying low thresholds than they do for higher-level thresholds.
We refer to this as the Good enough bias and suggest that it may be responsible for differences in distributions of thresholds obtained by
automated and manual audiometry.By grant RC3DC010986 from the National Institutes of Deafness and Other Communication Disorders. The Rehabilitation Research and Development Service of the U.S. Department of Veterans Affairs supported this work through the
Auditory and Vestibular Dysfunction Research Enhancement Award Program (REAP) and a Senior Research Career Scientist.http://www.tandfonline.com/loi/iija202016-05-31hb2016Speech-Language Pathology and Audiolog