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Previous work to detect defects in food packaging seals using pulse-echo ultrasound inspired the backscattered amplitude integral (BAI) imaging technique, which could reliably identify channels with diameters 38 microm or larger at a center frequency of 17.3 MHz (lambda=86 microm). The current study presents two new processing techniques that more reliably reveal smaller channels ( approximately 6 microm in diameter). The RF sampling technique (RFS) displays a single, time-gated, pressure value from the received (not envelope-detected) RF waveform at each transducer position. The RF correlation technique (RFC) calculates the correlation coefficients of the RF signals with a reference signal that does not pass through a channel. The correlation coefficient can be calculated for the entire RF signal (RFCE) or over a short segment of the RF signal (RFCS). The performance of these imaging methods for detecting channel defects is investigated for plastic and aluminum foil trilaminate films with 6, 10, 15, 38, and 50 microm channels filled with water or air. Data are collected with a focused ultrasound transducer (17.3 MHz, 6.35 mm in diameter, f/2, 173 microm -6 dB pulse-echo lateral beamwidth at the focus) scanned over a rectangular grid, keeping the package in the focus. Performance is measured using detection rates, image contrast, and contrast-to-noise ratio (CNR). Both RFS and RFCS have improved detection rates relative to BAI for channels 15 microm or smaller. The RFCS technique is the most effective at smoothing the background, leading to the greatest CNR improvements.

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A novel approach in food package defect detection is proposed based on system identification theory, in which the channel defect detection problem can be regarded as the conventional system identification problem, i.e., estimation of the system impulse response based on the input-output sequence using parametric and nonparametric models. The well-known parametric model ARX has been investigated in this paper. The data are collected with a focused ultrasound transducer (17.3 MHz, 6.35-mm diameter, f/2, 173 microm -6 dB pulse-echo lateral beam width at the focus) scanned over a rectangular grid, keeping the packages in the focus. Performance is measured in terms of detection rate, image contrast, and contrast-to-noise ratio. The results using the ARX model are compared with previous image formation techniques and also compared with the non-parametric method, i.e., spectral analysis. The results show that the ARX model has the comparable detection rate as RFCS and higher detection rate than BAI and RFS (except 6-microm air-filled channel in plastic trilaminate film) for channel in plastic trilaminate film. The ARX model has achieved the moderate contrast enhancement and ranks second in contrast-to-noise ratio enhancement among the compared techniques. The ARX model has a low detection rate for channel defects in aluminum trilaminate film, which shows that its performance is material-dependent. Finally, the parametric method, ARX model demonstrates better performance than the non-parametric method, spectral analysis for food package defect detection.

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The monopole-source solution was used to calculate the three-dimensional complex acoustic pressure field for focused circular apertures in a medium having homogeneous acoustic and thermal properties. The three source diameters were 1, 2, and 4 cm and the eight transmit f-numbers (ratio of the radius of curvature/source diameter) were 0.7, 1.0, 1.3, 1.6, 2.0, 3.0, 4.0, and 5.0. For these focused field geometries, eight ultrasonic frequencies were evaluated (1, 2, 3, 4, 5, 7, 9, and 12 MHz) from which the three-dimensional temperature distribution was calculated using the bio-heat transfer equation in homogeneous, perfused media (attenuation=absorption=0.3 dB/cm-MHz; perfusion length: 1.0 cm). For each of the 192 cases, the acoustic field was normalized to the derated spatial peak, temporal average intensity (I(SPTA.3)) of 720 mW/cm(2), the maximum value allowed by the FDA 510(k) diagnostic ultrasound equipment approval process. Using the normalized acoustic field, the axial temperature increase profiles and the maximum temperature increases (DeltaT(max)) were determined for each case. Also, from the normalized acoustic field, the unscanned soft-tissue thermal index (TIS) was determined. In general, DeltaT(max), TIS, and source power increase with increasing transmit f-number, source diameter, or frequency. The TIS generally underestimates (is less than) DeltaT(max) for f-numbers /=3. These exceptions suggest a breakdown of the ODS procedures far calculating TIS.

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Positioning of the graft for anterior cruciate ligament (ACL) reconstruction and securing the graft at various degrees of knee flexion are interrelated factors when attempting to restore a knee's normal kinematics. The interrelationships between graft positioning on the femur and tibia (graft 'isometricity'); securing the graft at various positions of knee flexion; and the resulting restoration or disruption of the knee kinematics were studied on ten fresh frozen cadaveric knee specimens. Well placed ('isometric') grafts appeared to restore almost normal knee kinematics regardless of the position of the knee at the time of securing the grafts. This was, however, not the case in non-ideally placed grafts. 'Nonisometric' ACL substitutes which became taut in extension, overconstrained the knee if the graft was secured in flexion. If the same graft was secured in extension, increased joint laxity in flexion occurred. In contrast, 'nonisometric' ACL substitutes which became taut in flexion overconstrained the knee if the graft was secured in extension. If the same graft was secured in flexion, the graft became slack during extension.

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Hermetically-sealed flexible food packages require very effective seal integrity testing to extend the shelf stability of thermally processed food. The initial goal of this study was to estimate the detection limits of laboratory-generated channels which simulate defects in food packages using pulse-echo ultrasonic imaging techniques. Packages with well characterized (via transmission optical microscopy) laboratory-generated channels that simulate defects with diameters between 9 and 325 microm in the seal plane traversing the major axis of the heat seal were generated in heat-sealed microwavable retort-pouch plastic film (trilaminate). Pulse-echo techniques in the 13-17 MHz center frequency range were investigated. The samples were examined with a conventional B-mode imaging technique, which was found to be inadequate for subwavelength imaging of the types of typical channel defects found in shelf-stable food packages. Based on conventional B-mode image features, a new goal of this study was established to develop and evaluate an imaging technique which would exhibit subwavelength imaging capabilities. The new imaging technique called backscattered amplitude integral (BAI) is introduced here. It was observed that BAI-mode imaging has the ability for subwavelength detection of channel defects, e.g., detection of a 10-microm diameter channel defect at a center frequency of 13.1 MHz (lambda=182 microm).

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A new imaging technique has been proposed that combines conventional B-mode and synthetic aperture imaging techniques to overcome the limited depth of field for a highly focused transducer. The new technique improves lateral resolution beyond the focus of the transducer by considering the focus a virtual element and applying synthetic aperture focusing techniques. In this paper, the use of the focus as a virtual element is examined, considering the issues that are of concern when imaging with an array of actual elements: the tradeoff between lateral resolution and sidelobe level, the tradeoff between system complexity (channel count/amount of computation) and the appearance of grating lobes, and the issue of signal to noise ratio (SNR) of the processed image. To examine these issues, pulse-echo RF signals were collected for a tungsten wire in degassed water, monofilament nylon wires in a tissue-mimicking phantom, and cyst targets in the phantom. Results show apodization lowers the sidelobes, but only at the expense of lateral resolution, as is the case for classical synthetic aperture imaging. Grating lobes are not significant until spatial sampling is more than one wavelength, when the beam is not steered. Resolution comparable to the resolution at the transducer focus can be achieved beyond the focal region while obtaining an acceptable SNR. Specifically, for a 15-MHz focused transducer, the 6-dB beamwidth at the focus is 157 mum, and with synthetic aperture processing the 6-dB beamwidths at 3, 5, and 7 mm beyond the focus are 189 mum, 184 mum, and 215 mum, respectively. The image SNR is 38.6 dB when the wire is at the focus, and it is 32.8 dB, 35.3 dB, and 38.1 dB after synthetic aperture processing when the wire is 3, 5, and 7 mm beyond the focus, respectively. With these experiments, the virtual source has been shown to exhibit the same behavior as an actual transducer element in response to synthetic aperture processing techniques.

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Theoretical and experimental methodology are presented for accurately determining the effective radii of unfocused, circular plane piston transducers as well as using tone burst hydrophone measurements to verify steady-state theoretical calculations. Experiments using two specially fabricated unfocused, composite piezoelectric transducers demonstrate the validity of the methodology. For spherically focused circular transducers, a simple model is used to estimate the transient diffraction encountered in co-axial flat hydrophone measurements.

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This paper considers the problem of detecting lines in speckle imagery, such as that produced by synthetic aperture radar (SAR) or ultrasound techniques. Using the physical principles that account for the speckle phenomenon, we derive the optimal detector for lines in fully developed speckle, and we compare the optimal detector to several suboptimal detection rules that are more computationally efficient. We show that when the noise is uncorrelated, a very simple suboptimal detection rule is nearly optimal, and that even in colored speckle, a related class of detectors can approach optimal performance. Finally, we also discuss the application of this technique to medical ultrasonic images, where the detection of tissue boundaries is considered as a problem of line detection.

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The principal motivation of the study was to assess experimentally the question: "Is the MI (Mechanical Index) an equivalent or better indicator of nonthermal bioeffect risk than I(SPPA.3) (derated spatial peak, pulse average intensity)?" To evaluate this question, the experimental design consisted of a reproducible biological effect in order to provide a quantitative assessment of the effect. The specific biological effect used was lung damage and the species chosen was the rabbit. This work was initiated, in part, by a study in which lung hemorrhage was observed in 7-week old C3H mice for diagnostic-type, pulsed-wave ultrasound exposures, and, therefore, 6- to 7-week old C3H mice were used in this study as positive controls. Forty-seven adult New Zealand White male rabbits were exposed to a wide range of ultrasound amplitude conditions at center frequencies of 3 and 6 MHz with all temporal exposure variables held constant. A calibrated, commercial diagnostic ultrasound system was used as the ultrasound source with output levels exceeding, in some cases, permissible FDA levels. The MI was shown to be at least an equivalent, and in some cases, a better indicator of rabbit lung damage than either the I(SPPA.3) or p(r.3) (derated peak rarefactional pressure), thus answering the posed question positively. Further, in situ exposure conditions were estimated at the lung pleural surface (PS); the estimated in situ I(SPPA.PS) and p(r.PS) exposure conditions tracked lung damage no better than I(SPPA.3) and p(r.3), respectively, whereas the estimated in situ MI(PS) exposure condition was a slightly poorer predictor of lung damage than MI. Finally, the lungs of six adult crossbred pigs were exposed at the highest amplitude exposure levels permitted by a diagnostic ultrasound system (to prevent probe damage) at both frequencies; no lung damage was observed which suggests the possibility of a species dependency biological effect.

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UNLABELLED: In order to estimate incidence, severity and associated factors in the development of the degenerative arthritis of the knee following a cruciate ligament injury, a multicenter, longterm follow-up study was undertaken. The time interval between injury and follow-up exam was a minimum of 15 years (range 15-52 years). Extensive physical examination and radiographic analyses from four "Knee Centers" (Hospital for Special Surgery, New York; Orthopädische Klinik, Bruderholz; Orthopaedic and Arthritic Hospital, Toronto; Orthopaedic Department Wichita, Kansas) on 328 patients revealed that the best correlation to the degree of osteoarthritis could be found to the time of meniscectomy. All other operations (suture of cruciate ligament, intraarticular or extraarticular reconstruction) showed much less correlation to the severity of the degenerative arthritis found at the follow-up exam. IN CONCLUSION: Preservation of as much meniscus tissue as possible at the time of injury seems to be the best warranty for slowing down degenerative arthritis after cruciate ligament injury.

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The Doppler technique has traditionally been the method used to extract motion information from ultrasonic echoes reflected by moving tissues. The Doppler technique has been around for a long time, and has been extensively reviewed and analyzed in the literature. Recently, time-domain methodologies for estimating tissue motion have gained in popularity. Time-domain methods have advantages over Doppler methods in many applications, and as of yet have not been comprehensively reviewed. An overview of time-domain techniques that have appeared in the literature over the past few years is presented. Their potential advantages over Doppler are examined, and the individual techniques are compared.

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A real-time ultrasound time-domain correlation (UTDC) blood flowmeter has been developed. Real-time performance has been achieved through the implementation of a custom-designed high-speed residue-number system (RNS) hardware correlator. The flowmeter is interfaced to a commercial ultrasound imager and can produce one-dimensional velocity versus range graphs at a rate of three per second. It has been validated in a blood flow phantom under a variety of conditions along with in vivo measurements in the human carotid artery. The theory of the time-domain correlation technique, design and implementation of flowmeter hardware, and the important correlation parameters which affect the performance of the flowmeter are described.

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For Part I, see ibid., vol.40, no.6, p.768-775 (1993). The performance of a real-time ultrasound time-domain correlation (UTDC) flowmeter employing a high-speed residue number system correlator under various flow conditions for different correlation parameter settings is evaluated. Previous work has incorporated a weighted-averaging scheme to estimate the flow velocity over a wide number of echo signal spacings. The present evaluation indicates that a linear averaging of 50 adjacent echo signal pairs produces equivalent accuracy and precision at real-time processing speed as compared to previous non-real time systems incorporating weighted averaging.

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A comparison was made of the stability of isometric versus nonisometric anterior cruciate ligament (ACL) reconstructions when subjected to immediate postoperative continuous passive motion (CPM). Anterior cruciate ligament reconstructions were performed on 13 anatomic specimen knees using bone/patellar tendon/bone grafts. Nine ACL substitutions were considered isometric with maximum graft length changes of less than 1 mm. Four ACL substitutions were nonisometric with graft length changes of 3 mm or greater resulting from tightening in flexion. The specimens were subjected to CPM through 0 degrees-95 degrees knee flexion. Knee stability was remeasured with a knee arthrometer at three and 14 days after beginning CPM. All four nonisometric specimens had failed within three days, with increased anterior laxity of 2-9 mm in both the Lachman (20 degrees) and anterior drawer (90 degrees) positions. All nine isometric reconstructions successfully retained pre-CPM anterior stability within 1 mm after 14 days of CPM. This investigation illustrates the importance of isometric graft placement for ACL reconstruction success. Continuous passive motion does not appear to adversely affect immediate ACL-substitute integrity or fixation if graft placement is isometric (less than 1 mm of graft excursion through 0 degrees-110 degrees of knee motion). Continuous passive motion may cause graft deformation, fixation failure, or both, with resultant loss of knee stability if the graft is not isometrically positioned (greater than 3 mm of graft excursion resulting from tightening in flexion).

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In order to study the functional anatomy of the knee joint, careful anatomical dissections were conducted on over 130 fresh-frozen cadaveric knee specimens. We found no evidence to support the two-bundle and three-bundle theories of cruciate ligament fiber patterns. The longest fibers in the anterior cruciate ligaments (ACL) measured 37 mm, and the longest in the posterior cruciate ligament (PCL), 41 mm. Cruciate ligament insertions follow a transition line on tibia and femur. Usually not all the fibers of the cruciate ligaments are taut at the same time. They are progressively recruited according to the biomechanical demands placed on them. Fibre recruitment in the ACL is from knee flexion to extension and in the PCL from extension to flexion. The concept of fiber recruitment was recently evaluated mathematically. As a working hypothesis, the knee joint can be looked upon as a biological realization of the crossed four-bar linkage, even in three dimensions. In vitro measurements have shown that correct graft placement in cruciate reconstructions is critical for knee biomechanics. Incorrect placement of grafts may lead to decreased range of motion and/or increased laxity. Distance changes of 3 mm between femoral origin and tibial insertion of a graft may lead to a 400% increase of graft preload and will thus easily reach published pull-out forces for some of the graft fixation methods (button = 248 N). Precise drill guides and isometers may be helpful in any operative technique (open, arthroscopic). Using the IKDC evaluation form and the KT-1000 arthrometer, our studies on 25 patients demonstrated a direct correlation between intraoperative graft tracking and the clinical outcome 2 years after operation. Biomechanical studies to investigate in vivo strain patterns of the anterior cruciate ligament and in vitro strain patterns of isometrically placed cruciate graft reconstructions showed that they did not reach critical fixation failure or graft rupture loads. The highest values were measured in Lachman and anterior drawer testing. In the 20-kg Lachman test the maximum load was 96 +/- 6 N. This was twice the maximum loads of any of the quadriceps exercises (40-50 N). With an isometrically placed graft, full active range of motion postoperatively and exercises with isolated or combined contractions of quadriceps and hamstring muscles will result in small graft loads. Postoperative immobilization with plaster and/or protection with braces may therefore become obsolete.

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Because predisposition to autoimmunity has been associated with HLA-D alleles and alopecia areata is hypothesized to be a T-cell mediated autoimmune hair loss, we determined DR and DQ alleles in 88 white and 10 American black patients with alopecia areata as well as controls with the use of restriction fragment length polymorphism typing with cDNA probes. White patients with alopecia areata have an increase in the phenotype frequencies of DR4 and DQw8 and an increase in genotype frequencies of DR4 and DR5 (now DRw11[5]). These associations are in agreement with those reported in two other studies but are not significant when corrected by the number of HLA antigens tested. Sixty-one percent of all patients with AA have DR4 and/or DRw11(5) specificities vs 40% of controls, with more DR4,DRw11(5) and DQw7(w3), DQw8(w3) heterozygotes among patients. DQw6(w1) phenotype frequencies and DRw52a phenotype and genotype frequencies are significantly decreased in patients with alopecia areata relative to controls. This highly significant negative association with the HLA DRB3 allele DRw52a in whites persisted even when DR4- or DRw11(5)-positive individuals were excluded from the patient and control groups. These data suggest that HLA-DR4 and DRw11(5) with their associated DQw7(w3) and DQw8(w3) specificities may confer susceptibility to alopecia areata, while DRw52a may confer resistance.

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Four overlapping cDNA clones were isolated from a lambda gt11 human placenta cDNA library using purified human IgG antibody, from a patient with bullous pemphigoid. The sequence was homologous to human placenta glutathione-S-transferase-pi (GST-pi). Using the placenta clone, epidermal cDNA clones were isolated from a human keratinocyte library. Expression of GST-pi mRNA in human skin, cultured keratinocytes and fibroblasts, and disorders of squamous hyperplasia was demonstrated by Northern blotting and in situ hybridization. Human epidermal and placental cDNA clones hybridized to the same genomic DNA fragments. Hybridization of placental cDNA to interspecific somatic cell hybrids showed retention of chromosome 11, confirming the assignment of GST 3 to the long arm of chromosome 11 by molecular means. Anti-GST-pi antibody did not give a basement membrane zone pattern, although some normal and BP sera contained antibodies to GST-pi. Human skin expresses glutathione-S-transferase-pi, which belongs to an enzyme family important for detoxification and carcinogenesis.

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An ultrasonic human-blood-flow velocity profile measurement method using time-domain correlation of consecutive echo pairs has been developed. The time shift between a pair of range gated echoes is estimated by searching for the shift that results in the maximum correlation. The time shift indicates the distance a group of scatterers has moved, from which flow velocity is estimated. The basis for the computer simulations and error analyses of the scheme includes a band-passed white Gaussian noise signal model for an echo from a scattering medium, the estimate of flow velocity from both a single scatterer and multiple scatterers, and a derived precision estimation. The error analysis via computer simulation includes an evaluation of errors associated with the correlation method. For a uniform flow velocity profile, beamwidth modulation represents the greatest error source. However, for a nonuniform flow velocity profile, the jitter caused by a small flow velocity gradient can exceed the other error sources. A detailed computer simulation evaluated the interdependencies of window length, beam width, vessel diameter, and viewing angle on the estimation of flow velocity.

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A novel ultrasonic volumetric flow measurement method using time-domain correlation of consecutive pairs of echoes has been developed. An ultrasonic data acquisition system determined the time shift between a pair of range gated echoes by searching for the time shift with the maximum correlation between the RF sampled waveforms. Experiments with a 5-MHz transducer indicate that the standard deviation of the estimate of steady fluid velocity through 6-mm-diameter tubes is less than 10% of the mean. Experimentally, Sephadex (G-50; 20-80 mum dia.) particles in water and fresh porcine blood have been used as ultrasound scattering fluids. Two-dimensional (2-D) flow velocity can be estimated by slowly sweeping the ultrasonic beam across the blood vessel phantom. Volumetric flow through the vessel is estimated by integrating the 2-D flow velocity field and then is compared to hydrodynamic flow measurements to assess the overall experimental accuracy of the time-domain method. Flow rates from 50-500 ml/min have been estimated with an accuracy better than 10% under the idealized characteristics used in this study, which include straight circular thin-walled tubes, laminar axially-symmetric steady flow, and no intervening tissues.

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An instrument has been developed to measure the acoustic pressure field in vivo during an obstetric ultrasound examination. This provides for improved intensity values for exposure calculations, to assist in assessment of bioeffects. The ultrasonic field is sampled using a calibrated seven-element linear array hydrophone of poly(vinylidene difluoride) transducers, which is placed as close as possible to the ovary, embryo, or fetus using a vaginal approach. The RF signals from the hydrophone are digitized at 50 MHz, and the maximum amplitude waveform received in the examination is recorded. The output of the clinical B-scanner is calibrated by a measurement with the hydrophone in a water bath. From the hydrophone measurements, the in vivo I(SPTA), I(SPTP), and I(SPPA) are computed. Further analysis allows the frequency-dependent tissue attenuation to be assessed.