John M. Reid

Scattering of Ultrasound by Blood

The ultrasonic volumetric scattering cross section of the erythrocyte has been measured over a range of frequencies by comparing the rms value of the gated backscattered signal from the blood with that of a wave reflected from a flat reflector with known reflection coefficient. It is found to be proportional to the fourth power of the frequency predicted by the wave scattering theory for small particles in the frequency range from 5 MHz to 15 MHz. The relation between the scattering coefficient and the hematocrit is also examined up to a hematocrit of 45 percent. This coefficient is found to increase along with the hematocrit until it reaches a maximum around hematocrit = 26 percent and then decreases as the hematocrit increases. Twerskys wave scattering theory is applied to describe this result.

Ultrasonic Duplex Echo-Doppler Scanner

Ultrasonic B-mode displays are produced by a new diagnostic scanner that yields dynamic Doppler information from blood flow in addition to both static and dynamic echo information from stationary and more slowly moving tissues. The effect is produced by combining the flow imaging capability of a multigate pulse-Doppler flow detector with a fast rotational pulse-echo B-mode scanner. The duplex system was designed for performing ultrasonic echo-Doppler arteriography where the location and geometry of the interface between occlusive atherosclerotic tissue and blood is of prime concern. Initial results on normal arteries in vivo are illustrated. Spatial alignment of echo and Doppler images is obtained by using the same transducer and scanning mechanism for both. However, clinical trials on patients with verified occlusive arterial disease indicated a two-transducer system would be more desirable. It is concluded that superposition of images of both tissue and blood decreases the uncertainties inherent in the display of either image alone.

Analysis and measurement of ultrasound backscattering from an ensemble of scatterers excited by sine‐wave bursts

This paper develops a practical approximation for the backscattering of periodic bursts of sine waves by a volume of randomly distributed scatterers. The approximation is applied to the measurement of a “volumetric backscattering cross section,” using a substitution method in which the rms value of the gated backscattered signal is compared with the rms value of a wave reflected from a target of known coefficient of reflection. It is shown that the signal backscattered from the ensemble depends on the attenuation of the wave in the volume and upon the burst and gate lengths. An equation to obtain the volumetric backscattering cross section from experimental data is derived.

Gender Differences in Stroke Examined in a 10-Year Cohort of Patients Admitted to a Canadian Teaching Hospital

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<0.001). The proportion of women, but not men, aged ≥80 years, increased significantly between 1996 to 1997 and 2005 to 2006. After adjustment for confounding, women were less likely to have infratentorial strokes (OR, 0.78; 95% CI, 0.62 to 0.97), be able to walk unaided on admission (OR, 0.69; 95% CI, 0.54 to 0.87), be treated with tissue plasminogen activator (OR, 0.51; 95% CI, 0.35 to 0.72), experience pneumonia (OR, 0.38; 95% CI, 0.26 to 0.55), achieve a discharge Barthel Index of ≥95 (OR, 0.75; 95% CI, 0.61 to 0.94, and were more likely to experience a urinary tract infection (OR, 2.06; 95% CI, 1.61 to 2.64). There was no gender difference in adjusted use of investigations. 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.

Ultrasonic Doppler Technique for Imaging Blood Vessels

Present ultrasonic Doppler flow detectors that use the Doppler effect on waves scattered from moving blood have provided useful information when directed by hand to trace the circulation of animals and man. By scanning with a highly directive flow detector, the areas of flow can be localized. Images can be formed of the interior of blood vessels. These images have the appearance of arteriograms and venograms made by dye contrast radiography, but have none of its hazards. The resolution appears adequate for useful images.

Cervical Carotid Imaging With a Continuous-Wave Doppler Flowmeter

A noninvasive technique for carotid arteriography using an ultrasonic directional Doppler flowmeter to image the carotid bifurcations is described. The technique uses a position sensing arm to hold the sharply focusing probe and translates the position of arterial flow onto an image storage screen. By multiple manual sweeps across the cervical carotids, a two-dimensional projection of the locus of arterial flow is developed. The probe beam is then applied through the eyelids to assess the posterior orbital ophthalmic flow. The adequacy of the internal carotid circulation and the presence of stenosis and calcified plaques are determined. Experience with the first 60 patients surveyed using the Doppler technique demonstrated a high degree of accuracy and reproducibility. The ultrasonic angiography provided local flow and velocity information that x-ray angiography did not. X-ray angiography is frequently indicated by the ultrasonic findings when risks of x-ray angiography might not otherwise be taken. The technique was found especially sensitive in detecting calcified atherosclerotic plaques and may be used in screening for the stroke-prone patient and following arterial lesions over extended periods of time.

Ultrasonic instrumentation for hematology.

Abstract In this paper recent progress on our effort to utilize ultrasound for diagnosing blood disorders is reported. Since the processes of erythrocyte aggregation and hemolysis will alter the acoustic scattering property of the blood, which is a function of the volume concentration as well as the dimension of the cells, ultrasonic backscattering characteristics from erythrocytes were used to study the problem of red cell aggregation and osmotic fragility. Changes in ultrasonic attenuation of the erythrocytes in Sickle Cell disease were used to characterize the tendency of red cells to sickle or deform under hostile physiological environment. Close relationships between ultrasonic absorption, cell morphology, pH, and oxygen tension of the blood have been observed.

Angular Dependence of Scattering of Ultrasound from Blood

The angular scattering of 5-MHz ultrasonic waves by blood was measured in the range from 60 to 1500. Experimental and theoretical results agree very well. A discussion on the use of angular scattering for determining the mechanical properties of the erythrocyte is presented.

Cerebrovascular evaluation with Doppler ultrasound

1. An Overview of Non-invasive Cerebrovascular Evaluation Using Doppler Ultrasound.- 2. Sound and Ultrasound.- 3. Doppler Flowmeter Systems.- 4. Doppler Imaging Systems.- 5. Other Ultrasonic Techniques and Current Research.- 6. Technique of Doppler Examination.- 7. Vascular Murmurs.- 8. Blood Flow in the Arteries.- 9. Hemodynamics of Carotid Artery Stenosis.- 10. Audio Spectral Analysis.- 11. The Periorbital Collateral Arteries.- 12. Ultrasonic Detection of the Non-Stenotic Plaque.- 13. Obstructive Lesions Diagnosed by Doppler Ultrasound.- 14. Clinical Management Decisions Based on Doppler Cerebrovascular Evaluation.- 15. Full Capability Doppler Diagnosis.- Doppler Cerebrovascular References.- Credit and Recognition List.- Index of Subjects.

Transmission of Ultrasound Through the Larynx as a Means of Determining Vocal-Fold Activity

A procedure is reported for determining vocal-fold closure using a technique of transmitting continuous-wave ultrasound through the larynx. A frequency of 3.2 MHz and an applied acoustic power of less than 1 mV/cm 2 was used. Physiological interpretation of received signals is discussed in terms of glottal closure, vocal-fold thickness, vocal-fold vibratory pattern, and thyroid cartilage ossification. Suggestions are offered for choice and arrangement of transducers for this application.