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Background Thrombolysis for acute ischaemic stroke (AIS) patients aged ≥80 years is evidence based, although its use in previously dependent patients is controversial. Methods Data from 831 thrombolysed AIS patients in our centre from 2009–2017 were used to compare demographic trends and outcomes (haemorrhage, mortality, three-month independence) in patients aged Results The percentage of treated patients aged ≥80 years increased year-on-year, doubling from 25% to 50% (pConclusion Patients aged ≥80 years and with dependency increasingly receive thrombolysis. Given poorer outcomes thrombolysis trials are needed in pre-stroke dependent patients.

Objective: The Clock Drawing Test (CDT) is commonly used as a screening tool for the assessment of dementia. The association between the CDT in acute stroke and long-term functional and cognitive outcomes in this population is unknown. The present prospective study is the first to examine if CDT scores in the acute stage after stroke are related to long-term outcomes and to compare the predictive ability of two scoring systems in a large sample of stroke patients. Method: A total of 340 patients admitted to an acute stroke unit were included in the present study. Separate stepwise multiple linear regression analyses were performed with eight independent variables (demographic/pre-stroke variables - age, sex, premorbid functioning; stroke-related variables - stroke severity, localization; cognitive variables - Orientation Test, CDT [2 scoring systems]), and four dependent variables administered one year post-stroke (Barthel Index, modified Rankin Scale, Reintegration to Normal Living index, Global Deterioration Scale). Results: Although both CDT scoring methods were related to all long-term outcome measures, the more comprehensive scoring system was the only baseline variable that significantly explained the variance in outcome measures in all four multiple regression models. Conclusion: Performance on the CDT in acute stroke is related to long-term outcomes including patients' degree of independence in performing activities of daily living, the degree to which they achieved reintegration into daily occupations, and the degree of cognitive decline observed one-year post-stroke. Future studies are needed to clarify the nature of the relationship between different CDT scoring systems and post-stroke outcomes.

Intravenous thrombolysis increases disability-free survival after acute ischaemic stroke in a time-dependent fashion. We aimed to determine whether pre-hospital notification, introduction of a CT scanner near to assessment site and introduction of out-of-hours thrombolysis services affect thrombolysis timing. Methods Timings related to thrombolysis were collected between May 2012 and June 2014 at a single hospital site; these included time to stroke physician assessment, time to cranial CT imaging and door to needle time. All thrombolysed ischaemic stroke patients admitted via the emergency department were included. Ambulance services were asked to pre-notify the emergency department of any suspected stroke patient during this period. Results We studied 182 patients (48% female; mean age 74 years; 59% pre-notified). Pre-hospital notification was associated with a significantly higher rate of CT scanning within 25 minutes (60% vs 24%, odds ratio [OR] 4.7, 95% confidence interval [CI] 2.4–9.0; pConclusion Pre-hospital notification is associated with earlier stroke physician review, CT imaging and delivery of thrombolysis. Referral to an out of hours thrombolysis service was not associated with additional delay.

Introduction Debate exists as to whether wake-up stroke (WUS) (i.e. symptoms first noted on waking) differs from stroke developing while awake [awake onset stroke (AOS)]. Unknown onset stroke (UOS) with unclear symptom onset time is infrequently studied. Aims This study aimed to examine differences in stroke characteristics and outcomes in these three groups. Methods The stroke registry database from Halifax Infirmary, Canada, was interrogated for hospitalised stroke patients between 1999–2011. Information was available on demographics, stroke characteristics, and functional status at discharge and six months (modified Rankin score [mRS]). Results Of 3890 patients, 65% had AOS, 21% WUS and 14% UOS. UOS patients were significantly older, more commonly female and living alone than AOS patients, with no difference between AOS and WUS. UOS rates increased from 10 to 16% of patients during the study period ( P < 0·0001). UOS but not WUS had a higher stroke severity than AOS. Intracerebral hemorrhage was less common (9 vs. 13%) and lacunar stroke more common (23 vs. 19%) in WUS compared to AOS. In UOS left hemisphere location was more likely, and lacunar stroke less common. Excellent outcomes were slightly lower for WUS. UOS had significantly higher rates of in-hospital mortality (23 vs. 16%, P < 0·0001) and poorer functional outcome six months after stroke (mRS < 3 in 26% of UOS and 46% of AOS, P = 0·02). Conclusion WUS has lower rates of ICH but similar stroke severity and outcomes to AOS. UOS prevalence appears to be increasing, with higher stroke severity and worse prognosis.

Neuromyelitis optica typically presents at a median age of 40-50 years. The myelitis is usually of acute onset, long (>3 vertebral segments) and causes severe sensorimotor and bladder and bowel disturbances. We describe a 73-year-old Caucasian woman with aquaporin-4 antibody-positive neuromyelitis optica whose index event was intermittent paroxysmal tonic spasms (and no other myelitis features) that recurred for 6 months and was associated with a short spinal cord lesion on MRI. This case reiterates recent observations that neuromyelitis optica can occur in older persons, and its myelitis can be 'short' and clinically mild.

physicians are often asked to prognosticate soon after a patient presents with stroke. This study aimed to compare two outcome prediction scores (Five Simple Variables [FSV] score and the PLAN [Preadmission comorbidities, Level of consciousness, Age, and focal Neurologic deficit]) with informal prediction by physicians.demographic and clinical variables were prospectively collected from consecutive patients hospitalised with acute ischaemic or haemorrhagic stroke (2012-13). In-person or telephone follow-up at 6 months established vital and functional status (modified Rankin score [mRS]). Area under the receiver operating curves (AUC) was used to establish prediction score performance.five hundred and seventy-five patients were included; 46% female, median age 76 years, 88% ischaemic stroke. Six months after stroke, 47% of patients had a good outcome (alive and independent, mRS 0-2) and 26% a devastating outcome (dead or severely dependent, mRS 5-6). The FSV and PLAN scores were superior to physician prediction (AUCs of 0.823-0.863 versus 0.773-0.805, P 0.0001) for good and devastating outcomes. The FSV score was superior to the PLAN score for predicting good outcomes and vice versa for devastating outcomes (P 0.001). Outcome prediction was more accurate for those with later presentations (24 hours from onset).the FSV and PLAN scores are validated in this population for outcome prediction after both ischaemic and haemorrhagic stroke. The FSV score is the least complex of all developed scores and can assist outcome prediction by physicians.

Background:weaimedtoassesswhethertheperformanceofstrokeoutcomemodelscomprisingsimpleclinicalvariablescould beimprovedbytheadditionofmorecomplexclinicalvariablesandinformationfromthe firstcomputedtomography(CT)scan. Methods: 538 consecutive acute ischaemic and haemorrhagic stroke patients were enrolled in a Stroke Outcome Study between 2001 and 2002. Independent survival (modified Rankin scale ≤2) was assessed at 6 months. Models based on clinical and radiological variables from the first assessment were developed using multivariate logistic regression analysis. Results: three models were developed (I–III). Model I included age, pre-stroke independence, arm power and a stroke severity score (area under a receiver operating characteristic curve, AUC = 0.882) but performed no better than Model II, which comprised age, pre-stroke independence, normal verbal component of the Glasgow coma score, arm power and being able to walk without assistance (AUC 0.876). Model III, including two radiological variables and clinical variables, was not statistically superior to model II (AUC 0.901, P = 0.12). Model II was externally validated in two independent datasets (AUCs of 0.773 and 0.787). Conclusion: this study demonstrates an externally validated stroke outcome prediction model using simple clinical variables. Outcome prediction was not significantly improved with CT-derived radiological variables or more complex clinical variables.

Symptomatic intracerebral haemorrhage following thrombolysis for ischaemic stroke causes significant morbidity and mortality. This study assessed which of four risk scores (SEDAN, HAT, GRASPS and SITS) best predicts symptomatic intracerebral haemorrhage. Methods: Data from 431 patients treated at Aberdeen Royal Infirmary (2003- 2013) were extracted from a thrombolysis database. Score performance was compared using area under the curve. Results: Any intracerebral haemorrhage occurred in 12% of patients (53/413); 11% fulfilling the SITS-MOST symptomatic intracerebral haemorrhage definition (6/53), 34% the ECASS II definition (18/53), and 43% the National Institute of Neurological Disorder and Stroke definition (23/53). Stroke severity, as defined by the National Institutes of Health Stroke Scale, significantly improved after 24 hours in patients without intracerebral haemorrhage, but not in those with. Significant symptomatic intracerebral haemorrhage predictors were age, glucose, stroke severity, hyperdense middle cerebral artery on CT scan, ASPECTS score and anti-platelet therapy. The haemorrhage after thrombolysis score performed best at predicting symptomatic intracerebral haemorrhage (area under the curve 0.67-0.78, p < 0.001). Conclusion: The haemorrhage after thrombolysis score uses the least variables and has the best predictive value for symptomatic intracerebral haemorrhage. Using predictive scores for clinical decision making depends on estimation of overall benefits as well as risk.

We describe the case of a male patient who presented with mononeuritis multiplex due to polyarteritis nodosa following recent hepatitis B infection. Despite immunomodulatory treatment, the condition progressed with renal and small bowel involvement and the patient died. This case illustrates the difficulty in treating this multisystem disorder and we review the literature on its pathogenesis and treatment.

The compound probability density function (pdf) is investigated for the ability of its parameters to classify masses in ultrasonic B scan breast images. Results of 198 images (29 malignant and 70 benign cases and two images per case) are reported and compared to the classification performance reported by us earlier in this journal. A new parameter, the speckle factor, calculated from the parameters of the compound pdf was explored to separate benign and malignant masses. The receiver operating characteristic curve for the parameter resulted in an A(z) value of 0.852. This parameter was combined with one of the parameters from our previous work, namely the ratio of the K distribution parameter at the site and away from the site. This combined parameter resulted in an A(z) value of 0.955. In conclusion, the parameters of the K distribution and the compound pdf may be useful in the classification of breast masses. These parameters can be calculated in an automated fashion. It should be possible to combine the results of the ultrasonic image analysis with those of traditional mammography, thereby increasing the accuracy of breast cancer diagnosis.

Classification of breast masses in ultrasonic B-scan images is undertaken using a multiparameter approach. The parameters are generated on the basis of a non-Rayleigh statistic model of the backscattered envelope from the breast tissue. They can be computed automatically with minimal clinical intervention once the location of the mass is known. A new discriminant is developed that combines these parameters linearly. It is seen that this new discriminant performs classification of masses into benign or malignant better than the classification by any one of the individual parameters. The data set studied consisted of 99 cases (70 patients with benign masses and 29 patients with malignant masses). The areas under the receiver operating characteristic (ROC) curves (A/sub z/) and statistical attributes of the areas were studied to establish the enhancement in performance. The A/sub z/ value after combining all the parameters was found to be 0.8701. Upon combining this parameter with the level of suspicion (LOS) scores of a radiologist, the performance is further enhanced with an area under the (empirical) ROC of 0.94 having an operating point at a sensitivity of 0.965 and specificity of 0.87. It is suggested that this automated approach may hold promise as a means of classifying breast masses.

Classification of breast masses in greyscale ultrasound images is undertaken using a multiparameter approach. Five parameters reflecting the non-Rayleigh nature of the backscattered echo were used. These parameters, based mostly on the Nakagami and K distributions, were extracted from the envelope of the echoes at the site, boundary, spiculated region and shadow of the mass. They were combined to create a linear discriminant. The performance of this discriminant for the classification of breast masses was studied using a data set consisting of 70 benign and 29 malignant cases. The Az value for the discriminant was 0.96 +/- 0.02, showing great promise in the classification of masses into benign and malignant ones. The discriminant was combined with the level of suspicion values of the radiologist leading to an Az value of 0.97 +/- 0.014. The parameters used here can be calculated with minimal clinical intervention, so the method proposed here may therefore be easily implemented in an automated fashion. These results also support the recent reports suggesting that ultrasound may help as an adjunct to mammography in breast cancer diagnostics to enhance the classification of breast masses.

Congenital abnormalities of the internal carotid artery (ICA) are infrequent and can be associated with aberrations of the Circle of Willis. A 47-year-old gentleman presented with transient neurological symptoms and cerebral infarction and carotid Doppler showed a stenotic right ICA. Subsequent computed tomographic angiography showed a hypoplastic ICA with a low-lying bifurcation at the C6 level and aplasia of the anterior communicating artery. This patient was commenced on aggressive medical therapy and at 7-month follow-up was symptom-free. This case report highlights the need for a centralized registry with long-term follow-up data in order to identify optimal management.

Classification of masses in ultrasonic B-mode images of the breast tissue using "normalized" parameters of the Nakagami distribution was recently investigated. The technique, however, did not yield performances that were comparable to those of an experienced radiologist, and utilized only a single image for tissue characterization. Because radiologists commonly use two to four images of a mass for characterization, a similar procedure is developed here. A simple summation of the normalized Nakagami parameters from two different images of a mass is utilized for classification as benign or malignant. The performance of the normalized Nakagami parameters before and after the summation has been carried out through a receiver operating characteristic (ROC) study. The bootstrap procedure has been utilized to compute the mean and SD of the ROC area, A(z), obtained for each parameter. It has been observed that combining normalized Nakagami parameters from two images of the mass may help to improve classification performance over that from utilizing the parameters of just a single image. The performance of this automated parameter-based approach appears to match that of a trained radiologist.

The Nakagami distribution was proposed recently for modeling the echo from tissue. In vivo breast data collected from patients with lesions were studied using this Nakagami model. Chi-square tests showed that the Nakagami distribution is a better fit to the envelope than the Rayleigh distribution. Two parameters, m (effective number) and alpha (effective cross section), associated with the Nakagami distribution were used for the classification of breast masses. Data from 52 patients with breast masses/lesions were used in the studies. Receiver operating characteristics (ROC) were calculated for the classification methods based on these two parameters. The results indicate that these parameters of the Nakagami distribution may be useful in classification of the breast abnormalities. The Nakagami distribution may be a reasonable means to characterize the backscattered echo from breast tissues toward a goal of an automated scheme for separating benign and malignant breast masses.

The K-distribution had been introduced as a valid model to represent the statistics of the envelope of the backscattered echo from phantom and tissue. This paper investigates the efficacy of the parameters of this statistical model; namely, the effective number and the effective cross-section, to characterize breast lesions as benign or malignant. Based on the normalized values of the effective number and the effective scattering cross-section, images containing benign and malignant masses were classified for a data set from 52 patients having breast masses/lesions. The receiver operating characteristic (ROC) curves were then obtained to test the classification based on these two parameters. The results indicate that the parameters of the K-distribution may be useful in classification of the breast lesions as benign and malignant.

This paper presents a complete PSpice model of an ultrasound single-element transducer, including electrical and mechanical matching as well as the focusing lens. By using this model, it is possible to obtain a relation between the electrical driving source and the acoustic velocity on the transducer surface. This boundary condition then allows the acoustic field to be calculated by numerical methods. Experimental data obtained with two different transducers are in good agreement with results predicted by the related models.

There is a strong interest in finding out which statistical model is the most appropriate for describing the envelope of the backscattered ultrasonic echoes from different types of tissues. The Rayleigh model is commonly employed, but this requires conditions, such as the presence of large number of randomly located scatterers with fairly uniform cross-sections, that are not always met. However, our research indicates that a model based on the K-distribution may provide a better fit to empirical data over a range of scattering conditions than the standard Rayleigh model. In this study, we looked at the K-distribution as a descriptor of the backscattered envelope of the breast and liver tissues (in vivo). By examining data from various tissue regions, a goodness-of-fit test (a least squares error method) was used to determine whether a Rayleigh or K-distribution model is more appropriate. From a large group of patients and volunteer scans (a total of 72 subjects), the fit between the K-distribution and the data is shown to have a much smaller error than the Rayleigh model.

We recently proposed a method for the estimation of imaging distortions associated with ultrasound images, based on the higher-order statistics (HOS) of radio frequency data. In this correspondence, we utilize the HOS-based estimated distortions to deconvolve ultrasound images of the breast. We also estimate imaging distortions based on the second-order statistics (SOS) of radio frequency ultrasound data and subsequently utilize them to deconvolve the same breast images. Both subjective and objective measures suggest that deconvolution with HOS-based distortion estimates led to significantly higher resolution gains as compared to the gains achieved when SOS-based distortion estimates were used.

We address the problem of improving the spatial resolution of ulrasound images through blind deconvolution. The ultrasound image formation process in the RF domain can be expressed as a spatio-temporal convolution between the tissue response and the ultrasonic system response, plus additive noise. Convolutional components of the dispersive attenuation and aberrations introduced by propagating through the object being imaged are also incorporated in the ultrasonic system response. Our goal is to identify and remove the convolutional distortion in order to reconstruct the tissue response, thus enhancing the diagnostic quality of the ultrasonic image. Under the assumption of an independent, identically distributed, zero-mean, non-Gaussian tissue response, we were able to estimate distortion kernels using bicepstrum operations on RF data. Separate 1D distortion kernels were estimated corresponding to axial and lateral image lines and used in the deconvolution process. The estimated axial kernels showed similarities to the experimentally measured pulse-echo wavelet of the imaging system. Deconvolution results from B-scan images obtained with clinical imaging equipment showed a 2.5-5.2 times gain in lateral resolution, where the definition of the resolution has been based on the width of the autocovariance function of the image. The gain in axial resolution was found to be between 1.5 and 1.9.

The envelope of the ultrasonic echo backscattered from tissues is modeled using non-Rayleigh statistics, namely the K-distribution. We show that the K-distribution can be used to describe the envelope of the echo, and its parameters may be used to distinguish between different regions in ultrasonic B-scan images. The validity of the model is tested using phantoms. Preliminary results indicate that the parameters of the K-distribution may be used to separate targets, in which the number of scatterers or the scattering cross-sections differ from that of the background. The method of employing the parameters of the K-distribution appears to be better than the methods based solely on the signal-to-noise ratio.

Background models to predict functional status post-stroke have utility in balancing groups in randomised trials, for outcome comparison between stroke centres and may assist in outcome prediction. This study aimed to develop models of both excellent [modified Rankin score (mRS) 0-1] and devastating outcomes (mRS of 5-6). Methods patients admitted with ischaemic or haemorrhagic stroke in 2001-02 to the Halifax Infirmary, Canada, were enrolled. Sixteen clinical variables from the first neurological assessment and six radiological variables from the acute CT scan were used to the model outcome at 6 months. Results five hundred and thirty-eight stroke patients were enrolled. Thirty per cent had an excellent outcome and 30% had a devastating outcome. Three models of the excellent outcome were developed [area under the receiver operator curve (AUC) 0.866-882] including the variables age, pre-stroke functional status, stroke severity, ability to lift both arms, walk independently, normal verbal Glasgow Coma Scale and leukoaraiosis. Predictive models of the devastating outcome (AUC of 0.859-0.874) included additional variables living alone pre-stroke and total anterior circulation stroke. The simplest models of both outcomes were externally validated (AUC of 0.856-0.885). Conclusion this study demonstrates new externally validated predictive models of both excellent and devastating outcomes. Leukoaraiosis was the only independent radiological predictor of both outcomes. Living alone pre-stroke predicted devastating outcome post-stroke.

A model for the scattering of ultrasound from breast tissue is proposed. The model is based on the use of non-Rayleigh statistics, specifically the K distribution to describe the backscattered echo from the tissue. A multiparameter test based on this model has been designed to characterize the tissue. The data from the B-scan images of the breasts of 6 different patients were analyzed using this model. The results indicate that the non-Rayleigh statistics seem to be useful in characterizing and identifying malignant, benign, and normal tissue regions. >

Graduated compression stockings are widely used for deep venous thrombosis (DVT) prophylaxis. Although below-knee stockings are used more often than thigh-length stockings, no reliable evidence indicates that they are as effective as thigh-length stockings.To compare the effectiveness of thigh-length stockings with that of below-knee stockings for preventing proximal DVT in immobile, hospitalized patients with stroke.Parallel-group trial with centralized randomization (minimization within centers) to ensure allocation concealment. The ultrasonographers who looked for DVT were blinded, but the patients and caregivers were not. (Controlled-trials.com registration number: ISRCTN28163533)112 hospitals in 9 countries.3114 immobile patients hospitalized with acute stroke between January 2002 and May 2009.1552 patients received thigh-length stockings and 1562 patients received below-knee stockings to wear while they were in the hospital.Ultrasonographers performed compression duplex ultrasonography in 1406 patients (96% of survivors) in each treatment group between 7 and 10 days after enrollment. They performed a second scan in 643 patients in the thigh-length stockings group and 639 in the below-knee stockings group at about 25 to 30 days. The primary outcome was symptomatic or asymptomatic DVT in the popliteal or femoral veins, detected on either scan.Patients were retained in their assigned group for all analyses. The primary outcome occurred in 98 patients (6.3%) who received thigh-length stockings and 138 (8.8%) who received below-knee stockings (absolute difference, 2.5 percentage points [95% CI, 0.7 to 4.4 percentage points]; P = 0.008), an odds reduction of 31% (CI, 9% to 47%). Seventy-five percent of patients in both groups wore the stockings for 30 days or until they were discharged, died, or regained mobility. Skin breaks occurred in 61 patients who received thigh-length stockings (3.9%) and 45 (2.9%) who received below-knee stockings.Blinding was incomplete, 2 scans were not obtained for all enrolled patients, and the trial was stopped before the target accrual was reached.Proximal DVT occurs more often in patients with stroke who wear below-knee stockings than in those who wear thigh-length stockings.Medical Research Council of the United Kingdom, Chief Scientist Office of the Scottish Government, and Chest Heart and Stroke Scotland.

For pt.I see ibid., vol.39, no.3, p.352-9 (1992). The existence of regularly spaced scatterers in the range cell of an ultrasonic imaging system results in speckle with a nonuniform phase distribution. Characteristic phase distributions occur at those particular demodulator frequencies at which the spacing is a multiple of one-quarter wavelength. A demodulator frequency sweeping technique for scatterer spacing estimation has been developed that uses parametric expressions of the phase statistics to detect and to identify scatterers with regular spacings. Changes in these parameters separately identify the mean scatterer spacing when it is an even and an odd multiple of the quarter wavelength of the demodulator frequency. This technique has good tolerance for variations in mean scatterer spacing, and has real-time implementation capability. >

Background and Purpose— Studies suggest that women with stroke are investigated less aggressively and receive tissue plasminogen activator less frequently than men. We tested whether gender differences in the investigation, treatment, and outcome of stroke are due to confounding factors. Methods— Gender differences in the use of investigations, trial enrollment, treatment with intravenous tissue plasminogen activator, and in-hospital outcomes were examined in data from our prospective registry using multivariate analysis to adjust for age, prestroke functional status, stroke subtype and severity, and atrial fibrillation. Results— Of 2725 consecutive hospitalized patients (1996 to 2006), 88% had ischemic stroke and 48% were women. Women were older (median age, 77 versus 70 years), had more severe strokes, and were less likely to be independent prestroke (78% versus 87%) compared with men (all P Conclusion— The majority of the gender differences in stroke were explained by confounding. More research is required to understand gender differences in stroke pathophysiology and the utilization of thrombolytic therapy.

This paper is based on the report of a survey of members of the Australian Psychological Society who are in private practice, which was carried out in March 1988. The results disclose a number of aspects of private practice of psychology in Australia that should give the profession cause for concern. There is no strong “private-practice sector” of the profession - possibly as few as 9% of APS members are in private practice - and a very high proportion of the small number of private practitioners who do exist are part-timers. Many of these part-timers, most of whom are employed in the health system or in education, arc providing their services to clients at cut rates - rates at which it would be impossible to sustain themselves and their families if private practice was their sole remunerated occupation. There is confusion about the APS's recommended fee, and the fee structure is not appropriate to non-clinical practitioners. Very few members, even among the full-time practitioners, charge privat...

We focus on piezoelectric devices in biomedical applications only. The devices are classified depending on their electrical, mechanical, or hybrid output signal. The hybrid device operates in a reversible mode and can generate both electrical and mechanical signals at its terminals. Electrical output piezoelectric sensors include frequency generators, force and pressure measurement sensors, accelerometers, velocity and displacement sensors, and receivers such as microphones. Linear scanning motors and acoustic wave generators fall into the category of mechanical output devices or actuators. Also, acoustic wave generators, such as lithotripters, loudspeakers, and ultrasonic therapy applicators, can be considered as actuators. Medical ultrasonic transducers used to generate images of internal organs of the body can be defined as hybrid or combination devices, as they act as both actuators and receivers producing an electrical signal proportional to the input mechanical stimulus at their terminals, and conversely, a mechanical displacement amplitude proportional to the electrical excitation. Keywords: piezoelectricity; ferroelectric; transducers; scanning; actuators; receivers; ultrasonics

This work attempts to measure the sound speed in objects by extracting the time delay of the system. In biological tissues, the accurate determination of the propagation path length is very difficult due to the highly irregular shape of the tissues. The accuracy in measuring the propagation path length will patly affect the accuracy of measurement of the speed of sound in the tissues. In order to overcome this problem. a pair of miniprobe rmnsducers [I, 21 was fabricated at the tips of a variable path caliper to fix and measure the path length with 0.05(mm) in accuracy. Methods to develop the measurement of the sjmd of sound by extracting the time delay of the system are proposed. Sound speed in some materials have been measured using the proposed methods as preliminary to the measurement of sound speed in biological tissues.

Identification of inhomogeneities is of importance in the areas of tissue characterization, nondestructive evaluation and underwater acoustics. This paper presents a specific approach to the identification and classification of inhomogeneities by using a pulsed swept frequency technique (chirping). The unique feature of this technique is that it allows frequency domain data to be determined directly from time domain data without needing to use Fourier transform algorithm and vice versa. The combined information contained in the time and frequency domain allows such parameters as size, shape, position, and structure of the object to be determined. The theoretical principles of the pulsed swept frequency technique are briefly outlined and the results of the experimental measurements of time and frequency domain scattering characteristics from objects of simple geometry are presented. Preliminary experimental data taken in the range of ka=100-900 indicate that the chirping approach can be successfully used in identification of differently shaped objects in water as well as in tissue characterization.

Ultrasonic imaging began, like life, in the sea, with the development of sonar for detecting submarines after World-War 1. However, to begin to image soft tissues the ranging time of ocean sonars needed to be reduced, and the electronics speeded up, by a factor of about the ratio between nautical miles and centimeters. This was only possible after the electronic developments made for radar in World-War 2. The rest of our technical history closely follows the developments in semiconductors and fabrication methods that led to modern electronics. This is a largely personal story of a recently graduated engineer with radar experience, who began with fabricating equipment to be used in the hospital to diagnose breast cancer, and continued with involvement the development of echocardiography and Doppler devices. Along the way many others have contributed to the field, including work in other countries that is not covered here. In future, ultrasonic imaging may hold the key to understanding some fundamental questions in human health if adopted for screening studies. It alone offers a relatively inexpensive imaging method that is free of known hazards.

The authors show that when mechanical scanning used in color flow mapping is controlled using a stepper motor, the signal-to-noise (S/N) ratio is improved because the uncancelled signal due to the transducer scanning effect is reduced. As a result, color flow mapping may be extended to the imaging of small vessels and under weakly scattering, low-flow-rate conditions. Experimental results obtained using a Doppler phantom with a neoprene simulated vessel of 0.6-cm internal diameter are presented. >

Breast cancer diagnosis through ultrasound tissue characterization was studied using receiver operating characteristic (ROC) analysis of combinations of acoustic features, patient age, and radiological findings. A feature fusion method was devised that operates even if only partial diagnostic data are available. The ROC methodology uses ordinal dominance theory and bootstrap resampling to evaluate A/sub z/ and confidence intervals in simple as well as paired data analyses. The combined diagnostic feature had an A/sub z/ of 0.96 with a confidence interval of [0.93, 0.99] at a significance level of 0.05. The combined features show statistically significant improvement over prebiopsy radiological findings. These results indicate that ultrasound tissue characterization, in combination with patient record and clinical findings, may greatly reduce the need to perform biopsies of benign breast lesions.

The L1 norm (absolute error minimization) deconvolution was applied to medical ultrasound. Its implementation requires a large amount of memory and computing time. A quadrature form of L1 norm deconvolution was derived for narrowband signals, which not only greatly reduced the size of the problem but also lessened the effects of undersampling on medium reflectivities. Preliminary tests on simulated and experimental data showed that L1 norm method performs very well even in the presence of a moderate noise level for both RF and quadrature signals. The time and memory saving in the latter algorithm is remarkable. >

Identification of inhomogeneities is of importance in the areas of tissue characterization, nondestructive evaluation and underwater acoustics. An approach to the identification of inhomogeneities by using a pulsed swept frequency technique (chirping) is presented. This technique allows frequency domain data to be determined directly from time domain data without using a Fourier transform algorithm and vice versa. The combined information contained in the time and frequency domain allows such parameters as size, shape, position, and structure of the object to be determined. The theoretical principles of the pulsed swept frequency technique are briefly outlined and the results of the experimental measurements from objects of simple geometry are presented. Preliminary experimental data indicate that the chirping approach can be successfully used in identification of differently shaped objects in water as well as objects embedded in tissue. >

It is known that if single-frequency, continuous-wave ultrasound or electromagnetic energy is reflected from straight line flow, defined here as one or more scatterers moving with constant velocity along an infinite straight line, the Doppler effect will shift the echo spectrum center frequency from the transmitted value, and broaden its bandwidth. It is shown here that if such straight line flow is shifted anywhere in the field without change of orientation, the absolute echo bandwidth remains unchanged. This result is unexpected, since the bandwidth arises from amplitude modulation of the echo from the scatterers as they pass through the incident field, and the shape of this field varies with position. The Doppler bandwidth may therefore be used to estimate the transverse component of the flow velocity anywhere in the sound beam. The effect of the system relative aperture on the minimum spectral broadening and maximum frequency indication may also be assessed at any range. >

The triple cepstrum, the third power of the inverse Fourier transform (IFT) of the logarithm of signal power spectrum, is used to characterize two-layer structures. The thickness of each layer can be found from the positions of the peaks in the triple cepstrum. Simulations and preliminary experiments have shown that the relative reflection coefficients can be reconstructed, in the ideal and lossless case, from the polarity and the amplitude of these peaks, as predicted by theory. The impedance pattern can be predicted even at low signal to noise ratio. A potential application of this method is to characterize blood vessel walls. The resulting thickness and impedance pattern could be useful in detecting and classifying plaques, particularly in the early stages. >

When regularly spaced scatters exist in an insonated region, the speckle phase may not be uniformly distributed. A novel frequency sweeping technique for scatterer spacing estimation is proposed and applied to simulated and to experimental data. Parametric expressions of the phase statistics are proposed and tested and tested for the estimation. Changes in these parameters identify the mean scatterer spacing for even and for odd multiples of the 1/4 wavelength cases, when sweeping the receiver quadrature demodulation frequency. This technique has good tolerance for variations in scatter spacing, and has real-time implementation capability. >

The Power-law Shot Noise (PLSN) model has been recently proposed for modeling the ultrasound RF echo. Its power-law exponent parameter, which was linked to tissue attenuation, has been effectively used in characterizing normal and abnormal tissue. The K-distribution model has also been proposed in the past for modeling the echo envelope, and functions of its parameters, linked to scatterer density, have been used to discriminate between normal and abnormal tissue. However, neither model produced satisfactory stand-alone features for differentiating between benign and malignant tumors. Observing PLSN and K parameters are linked to different tissue properties, we here propose to use vectors consisting of combinations of these parameters as signatures for malignant versus benign tissue characterization. We test the performance of the proposed features using receiver operating characteristic analysis of 100 clinical images of the breast.

Frequency compounding was recently investigated for computer aided classification of masses in ultrasonic B-mode images as benign or malignant. The classification was performed using the normalized parameters of the Nakagami distribution at a single region of interest at the site of the mass. A combination of normalized Nakagami parameters from two different images of a mass was undertaken to improve the performance of classification. Receiver operating characteristic (ROC) analysis showed that such an approach resulted in an area of 0.83 under the ROC curve. The aim of the work described in this paper is to see whether a feature describing the characteristic of the boundary can be extracted and combined with the Nakagami parameter to further improve the performance of classification. The combination of the features has been performed using a weighted summation. Results indicate a 10% improvement in specificity at a sensitivity of 96% after combining the information at the site and at the boundary. Moreover, the technique requires minimal clinical intervention and has a performance that reaches that of the trained radiologist. It is hence suggested that this technique may be utilized in practice to characterize breast masses.

The parameters of the Nakagami distribution have been utilized in the past to classify lesions in breast tissue as benign or malignant. To avoid the effect of operator-gain settings on the parameters of the Nakagami distribution, normalized parameters were utilized for the classification. The normalized parameter was defined as the ratio of the parameter at the site of the lesion to its average value over several regions away from the site. This technique, however, was very time consuming. In this paper, the application of frequency diversity and compounding is explored to achieve this normalization. Lesions are classified using these normalized parameters at the site. A receiver operating characteristic (ROC) analysis of the parameters of the Nakagami distribution has been conducted before and after compounding on a data set of 60 benign and 65 malignant lesions. The ROC results indicate that this technique can reasonably classify lesions in breast tissue as benign or malignant.

The method of backpropagation is used to estimate the range between two planar surfaces. This method is shown to be more tolerant in a noisy environment than another method that uses the spatial derivative of the measured wave field to estimate the range.