Kathleen A. Morrish

Durational aspects of the oral-pharyngeal phase of swallow in normal adults

We present durational data on normal oral-pharyngeal swallows in adults obtained using ultrasound imaging. The effects of normal aging on the oral-pharyngeal phase of swallowing were studied in 47 healthy adults. Timing of the oralpharyngeal phase of swallow was determined from frame-by-frame analysis of ultrasound videos of the motion of the tongue and hyoid bone from initial rest to final resting position. Duration of unstimulated (dry) swallows was compared to stimulated (wet) swallows across four age groups and by sex and age. For most subjects, dry swallows were longer than wet swallows; moreover, swallow duration was longest for older women than any other group. As age increased (55+), oral swallows were accompanied by extralingual gestures. Ability to produce a timed series of continuously dry swallows was somewhat influenced by age. Findings are suggestive of an age change more typical in women, with a pattern of multiple lingual gestures commonly seen after age 55 in both sexes. We suggest that subtle, subclinical, oral neuromotor changes occur with normal aging to cause these findings.

A Biophysical Model of Cochlear Processing: Intensity Dependence of Pure Tone Responses.

A mathematical model of cochlear processing is developed to account for the nonlinear dependence of frequency selectivity on intensity in inner hair cell and auditory nerve fiber responses. The model describes the transformation from acoustic stimulus to intracellular hair cell potentials in the cochlea. It incorporates a linear formulation of basilar membrane mechanics and subtectorial fluid-cilia displacement coupling, and a simplified description of the inner hair cell nonlinear transduction process. The analysis at this stage is restricted to low-frequency single tones. The computed responses to single tone inputs exhibit the experimentally observed nonlinear effects of increasing intensity such as the increase in the bandwidth of frequency selectivity and the downward shift of the best frequency. In the model, the first effect is primarily due to the saturating effect of the hair cell nonlinearity. The second results from the combined effects of both the nonlinearity and of the inner hair cell low-pass transfer function. In contrast to these shifts along the frequency axis, the model does not exhibit intensity dependent shifts of the spatial location along the cochlea of the peak response for a given single tone. The observed shifts therefore do not contradict an intensity invariant tonotopic code.

Vertebral bone mineral content in osteogenesis imperfecta

SummaryQuantitative computed tomography of the lumbar spine was carried out in 28 patients with osteogenesis imperfecta (OI) in order to measure vertebral trabecular bone mineral concentration (BMC). The patients ranged in age from 6–73 years, and included 3 of the 4 major clinical subtypes of the disease. The findings underscore the heterogeneity of osteogenesis imperfecta even among family members with the same disease type. In addition, cross-sectional analysis of Type I OI patients suggests that BMC during young adulthood averages about 70% of normal, and subsequently falls more rapidly than in normal patients. BMC tends to be lower in the more severe forms of OI. Decreased BMC was not found in a few otherwise normal relatives with scoliosis or joint laxity.

Characterization of tongue shape.

Mathematical techniques are described for analyzing tongue shapes obtained with ultrasound images. The surface of the mid-sagittal section of the tongue was approximated by discrete points. In turn, these points were used to approximate position, slope and curvature of the tongue surface at a fixed time during speech. Two approaches were employed. The first method involved the use of finite difference approximations to derivatives of the function of tongue position. The second utilized a curve fit. Both methods were examined for reliability. Results of these analyses on a simple, single speech sound are discussed.

Lipid emulsions as contrast agents for hepatic sonography: An experimental study in rabbits

An ultrasound contrast agent capable of increasing hepatic echogenicity would be useful for the detection of hepatic tumors and metastases. Fatty liver is known to produce increased liver echogenicity. Intravenously administered lipid emulsions are phagocytosed by cells of the reticuloendothelial system the liver with transient hepatic lipid accumulation. We examined the effectiveness of three lipid emulsions of differing particle size as potential ultrasound contrast agents using a rabbit liver model. None of the tested emulsions showed any consistent ability to alter liver echogenicity at maximum tolerable doses. Lipid emulsions do not appear to have potential as contrast agents for ultrasound examination of the liver.

A microcomputer approach to storage of qualitative patient data using key words

A microcomputer program is presented which stores and retrieves qualitative patient information, such as diagnosis and physical findings. Users can design and enter a key word list and modify it as needed. Using those key words, up to 5000 patient entries can be made on a single floppy disk. Application of the program to CT scan study results is discussed.

Performance of one- and two-dimensional models for a slow flow system in a long, permeable tubule

A radially symmetric slow flow system in a long cylinder with moderate wall leakage is considered, with physical parameters taken from the renal proximal tubule. Dimensional analysis yields a simplified system which, under certain assumptions, is well-posed, and possesses a unique solution if a solution exists. A lumped parameter analysis generates a one-dimensional model identical to a typical one-dimensional model in a special case. The one- and two-dimensional models agree well in the situations examined. When the wall fluxes are of a certain class, the concentration to which the solution tends as the fluid proceeds down the tubule can be computed algebraically.

Use of a microcomputer to store information on radiology cases

A microcomputer program for storage of qualitative patient data has been applied to CT and special procedures case data. Different vocabularies have been established and utilised for these two case categories. Experience over two years involving more than 10,000 cases is discussed. Utility for statistical, research, and patient care purposes is demonstrated.

Parameter sensitivity in a mathematical model of basilar membrane mechanics

A mathematical model of cochlear processing is developed to describe the transformation from acoustic stimulus to intracellular hair cell potential. It incorporates a linear formulation of three-dimensional basilar membrane mechanics, subtectorial fluid-cilia displacement coupling, and a simplified description of the inner hair cell nonlinear transduction process. When the model parameters of the basilar membrane stage are set to values characteristic of the guinea pig, good agreement with experiment is obtained for single tone responses. When the parameters are varied, the basilar membrane tuning can change dramatically.

Characterization of tongue shape during normal speech

Averaged tongue shapes and polynomial equations were computed for five phonemes in order to determine aspects of tongue curve which distinguish between phonemes. Five repetitions of each of the phonemes /i/, /u/, /o/, /ae/, and /ɑ/ were produced by a normal volunteer using the carrier phrase “I can say /dVd/ again.” An ultrasound sector scanner was used to obtain midsagittal pictures of the posterior section of the tongue from vertical to 85° back into the throat. The pictures were digitized, and the resulting points were used to generate average tongue shapes and average quadratic and cubic fits for each phoneme. While both techniques provide information which allows the researcher to distinguish between the five phonemes used, only the averaged tongue shapes adequately reflect certain details of tongue shape.