Prediction of ultrasonic field propagation through layered media using the extended angular spectrum method.

The angular spectrum method is a powerful technique for modeling the propagation of acoustic fields. The technique can predict an acoustic pressure field distribution over a plane, based upon knowledge of the pressure field distribution at a parallel plane. Predictions in both the forward and backward propagation directions are possible. In addition to predicting the effects of diffraction, the model also includes the effects of attenuation, refraction, dispersion, phase distortion, and the effects of finite amplitude acoustic propagation. No other model currently exists which can predict the propagation of wideband acoustic fields produced by sources of arbitrary geometry including all of the above propagation effects. Prior investigations have focused on using backward propagation predictions to analyze the surface vibration patterns of acoustic radiators. In contrast, the current effort has placed particular emphasis on verifying the model in the forward propagation case. In this paper, both forward and backward predictions are presented which demonstrate the ability of the model to characterize a three-dimensional acoustic field based upon measurements at a single plane. Results are also presented which examine the ability of the extended model to predict acoustic propagation through media composed of stacked homogeneous layers. The model has immediate applications in the study of acoustic phenomena and in the field of acoustic transducer design. Additionally, significant progress has been made toward the ultimate goal of predicting the degradation of acoustic transducer performance due to propagation through inhomogeneous, nonlinear, tissue-like media.

Children with special health care needs program: urban/rural comparisons.

The purposes of this study were to: (1) describe both the urban and rural clients who received services from the Indiana Children with Special Health Care Needs program (CSHCN) including both demographic and clinical characteristics; (2) conduct a health care needs assessment of the CSHCN program clients in both urban and rural areas; and (3) measure the perceived quality and adequacy of the CSHCN program services. A survey instrument was developed and mailed to all 6,459 families who participated in the Indiana CSHCN program from July 1, 1990 to June 30, 1991. Of the 2,722 questionnaires used in the analysis, 1,624 clients (59.7%) resided in urban counties and 1,098 (40.3%) resided in rural counties. The most frequently noted conditions for program eligibility were asthma, ear infections, hearing impairments, heart defects, and convulsions and seizures. Asthma had greater prevalence among the urban clients while cleft lip/palate, epilepsy, and heart defects were more common among the rural clients. The majority of program clients perceived their medical needs as being met. However, significant numbers of clients perceived unmet needs for mental health services, support groups, information about community services, resources to pay for uncovered medical expenses, and respite care. Of the 23 listed services, five were reported at significantly lower rates by rural clients as not being met: regular medical care, recreation, child care/day care, parent support group services, and speech therapy. Quality of medical services was generally perceived as being "excellent or good," while services related to information about community programs, child's rights in school, resources available to pay for uncovered medical expenses, as well as communication between the treatment center and the child's school were more often rated as "fair or poor." A smaller proportion of rural clients rated physician care and availability of staff nurses as fair or poor. A larger percentage of the rural group reported that access to treatment center location was fair or poor, compared to the urban group. Overall, the evaluation of the Indiana CSHCN program has shown that the non-medical care component seems to be in need of change, especially in the area of information and communication. Attention needs to be focused on providing more family support such as respite or child care and support groups, better information and communications, and improved availability of mental health services to better enable the CSHCN program to meet its objectives.

Cost-effective shock wave hydrophones.

This article presents the design of a newly developed wideband, quantitative shock wave sensor (hydrophone) made of piezoelectric material polyvinylidene difluoride (PVDF). The novel aspects of this device include a disposable sensor element to reduce the per shot costs, and a self-monitoring feature that informs the user that the sensor needs to be replaced. The development, design, and use of the sensors are presented. Results indicate that these sensors can fulfill the requirements for accurate, wideband measurement of lithotripter fields, suitable for quantitative biophysical research or Food and Drug Administration submissions. The disposable feature of the hydrophone system makes the system cost effective for research, quality assurance, and regulatory submissions.

Immediate unrestricted feeding of infants following cleft lip and palate repair.

Postoperative feeding regimens after cleft lip and palate repair continue to be a controversial issue. This study was designed to test the feasibility of immediate unrestricted feeding after lip and palate closure with attention to operative outcome or complications. A retrospective analysis of two feeding protocols involved 80 infants with both unilateral and bilateral defects. Protocol A utilized tube and syringe feedings, and protocol B utilized unrestricted bottle or breast feedings. There were no instances of lip or palate wound complications in the unrestricted group. We conclude that immediate unrestricted feeding may be instituted safely, thus improving and simplifying postoperative management after cleft lip and/or palate repair.

Iliac versus cranial bone for secondary grafting of residual alveolar clefts.

Secondary bone grafting of the maxilla in the mixed transitional dentition stage has become a well-accepted procedure in the surgical protocol for rehabilitation of patients with residual alveolar clefts. This retrospective study was undertaken to evaluate and compare the long-term results obtained with iliac or cranial cancellous bone graft material in the area of alveolar clefts and was based on the independent experience of two plastic surgeons from the same center using exclusively cranial or iliac cancellous bone, respectively. The criteria for surgery were similar. The surgical technique, with the exception of the bone-grafting material, also was similar, and all patients were treated by the same group of orthodontists. Fifteen patients from each group, from a total of over 100 patients, were randomly selected and included in the study. All patients were followed up from 18 to 60 months. Operative and perioperative parameters, donor-site morbidity, and long-term results were evaluated, compared, and analyzed. There were no significant differences between the two groups, and equally good results in terms of bone incorporation, tooth eruption, and appearance were obtained with both iliac and cranial bone grafts. We conclude from our study that successful bone grafting is primarily achieved by adherence to meticulous surgical technique, simultaneous closure of coexisting oronasal or palatal fistulae, use of cancellous bone particles only, and coverage of the grafts with well-vascularized flaps. The source of bone graft does not seem to primarily influence the success of the outcome.

Shock wave sensors: I. Requirements and design.

In the last 9 years, extracorporeal shock wave lithotripsy has become one of the preferred procedures for the treatment of urinary and gallbladder calculi. While there is still uncertainty as to the mechanisms of stone fragmentation, current hypotheses suggest that acoustical shock wave parameters such as rise time, peak compressional and rarefactional pressure, and frequency content may all influence the treatment's efficiency. Thus, optimization of lithotripsy treatment needs pressure sensors that can adequately characterize the shock wave field. This article presents and discusses the design of reliable, wideband, quantitative shock wave sensors made of piezoelectric material. The development, design, and performance characteristics of the sensors are presented. Sensor construction details are described, as are the methods used to characterize the sensor's acoustical performance. The key acoustical parameters of the sensor, its frequency response, and directivity pattern are presented; theory indicates that the probes feature uniform sensitivity over the frequency range up to 100 MHz. Preliminary experimental results indicate that piezoelectric polymer sensors made of polyvinylidene fluoride (PVDF) with a low acoustical impedance backing are suitable for lithotripter field measurements. The applicability of sensors based on fiber optics to shock wave measurements is also briefly discussed. In a companion article, shock wave measurement techniques are outlined and selected lithotripter test data are presented.

Brain malformations in linear nevus sebaceous syndrome: an MR study.

A case is presented of a 16-year-old girl who had unilateral linear nevus sebaceous syndrome and ipsilateral brain malformations. These consisted of unilateral megalencephaly, white matter hypoplasia and excessive gray matter, deficient sulcation, and focal areas of pachygyria of the frontal lobe best seen on magnetic resonance imaging.

Tissue expansion for the reconstruction of burn defects.

Tissue expansion has emerged recently as an alternative reconstructive procedure and has been used for the treatment of a variety of defects. This paper presents our experience with the use of tissue expansion exclusively for the treatment of secondary burn defects. The technique was used in 22 consecutive patients. The technical aspects of the procedure are described. The advantages of tissue expansion, including the superior quality of reconstruction, cost effectiveness, and absence of donor site scar are presented. The disadvantages, including the need for two stages, multiple office visits, its application for relatively small defects, and the objectionable temporary appearance, are discussed. Finally, patient selection, and refinements of the technique and tailoring of the expanded flaps to achieve the best possible reconstructive and esthetic results and limit the possibility of complications are discussed.

A computerized system for measuring the acoustic output from diagnostic ultrasound equipment.

The measurement arrangement, which complies with the requirements of the US Food and Drug Administration, consists of a positioning system with a full range of degrees-of-freedom and a digital oscilloscope, both under complete computer control. The acoustic pressure-time waveform is recorded using membrane-type and needle-type polyvinylidene fluoride (PVDF) hydrophone probes. The overall bandwidth of the system depends on the hydrophone probe used and can range up to 100 MHz. A complete description of the system and the measurement procedures is given, along with a brief discussion of the various factors which affect measurement uncertainty. The largest overall uncertainty of the same associated with acoustic intensity measurements was determined to be no greater than 20% for I(sppa) and 25% for I(spta) (spatial peak pulse average intensity and spatial-peak temporal-average intensity, respectively). Other applications of the system include transducer characterization and research work in ultrasound dosimetry and bioeffects.

Wide-band piezoelectric polymer acoustic sources.

The design of a wideband acoustic source made of the piezoelectric polymer polyvinylidine fluoride (PVDF) is described. The source was developed for the characterization and absolute calibration of ultrasonic hydrophone probes. Construction details are described and performance characteristics of the wideband PVDF transmitter, including its transmitting voltage response and directivity patterns, are compared with theoretical predictions in the frequency range up to 40 MHz. The Krimholtz-Leedom-Mattaei (KLM) model was used to examine the influence of the PVDF polymer film thickness, the backing acoustic impedance, the cable length, and the electrical source resistance on overall transmit transfer characteristics. A comparison is made with traditional piezoelectric ceramic acoustic sources, and it is shown that piezopolymer transmitters exhibit some improved properties and are well suited for certain ultrasound dosimetry applications. In particular, the polymer sources have been found useful in measurements based on swept-frequency excitation. Those measurements allow characterization of transmitters and receivers to be performed as a virtually continuous function of frequency.

Congenital embryonal rhabdomyosarcoma of the hand and Apert's syndrome.

A unique case of congenital embryonal rhabdomyosarcoma of the hand in a patient with Apert's syndrome is presented. Immediately after birth a 1 cm soft, bluish mass of the right thenar eminence was clinically diagnosed as a hemangioma. Several months later when the lesion started rapidly enlarging the nature of the tumor was identified, and it was treated with a multidisciplinary approach that included surgical resection, chemotherapy, and radiation.

Factors affecting the choice of preamplification for ultrasonic hydrophone probes.

This paper gives a systematic analysis of the effects of including an integrated (built-in) preamplifier into the ultrasonic piezoelectric probes (hydrophones) that are finding increasing use in biomedical applications. The design parameters considered include the end-of-cable sensitivity, gain, dynamic range, power supply requirements, construction intricacy, and cost. The rationale behind the inclusion of a preamplifier is given, and it is shown that the additional complexity introduced with the preamplifier into the measurement chain may not be warranted in all applications. Both the drawbacks and advantages of hydrophone preamplification are demonstrated, especially for the case of high pressure amplitude ultrasonic field measurements. Guidelines are developed for the potential user to identify the need for preamplification and the factors that influence the selection of the appropriate circuitry.

Craniofacial surgery. Its evolution and application.

Craniofacial surgery is a relatively new subspecialty that offers correction for many complex congenital, traumatic, and tumor-related deformities of the head and face. An experienced and extensive craniofacial team is imperative to the long-term success of a craniofacial surgery program. A greater awareness of the syndromes and deformities involved, and of the corrections possible, leads to earlier diagnosis, appropriate early care (sometimes life-sustaining), and the establishment of proper long-term treatment plans.

On the importance of muscle repair in secondary cleft lip deformity.

Generally the evolution of cleft lip repair has included a transition from those methods with primary emphasis on the skin design with intricate flaps, going to further elaborations of carefully designed skin and muscle units but with minimal muscle dissection or intentional reorientation, on to those with greater emphasis on extensive muscle dissection with specific realignment of the orbicularis oris muscle. These latter methods assign to the skin a more complementary role in the plan of correction. This article joins others in which it is now felt that extended dissection and surgical reorientation should be done to include associated involved muscles of the lip, nose, and medial face. In particular, attention to the details of muscle repair as completely as possible, extending to the entire oro-naso-facial complex, seems pertinent in the matter of secondary correction of cleft lip deformities. A review of the anatomy involved, certain surgical philosophy, and examples of illustrated cases are included in this article.

Two useful small flaps for reconstruction of lip and nose.

This article presents an extension of known and tried surgical techniques involving muscle flaps with epithelial covering. These extensions of principles represent useful applications either as definitive corrective techniques or as stepping stones to further surgical corrections. It is hoped that the successful use of these techniques in the examples given might prompt further investigation and discussion in areas related to their use.

The spread of sensibility into previously anesthetic skin following intercostal flap transfer in a paraplegic.

Sensibility extending into previously anesthetic sacral skin is reported two years following the transfer of a neurovascular intercostal flap in a 13-year-old paraplegic.