Continuous wave ultrasonic Doppler tomography.

In continuous wave ultrasonic Doppler tomography (DT), the ultrasonic beam moves relative to the scanned object to acquire Doppler-shifted frequency spectra which correspond to cross-range projections of the scattering and reflecting structures within the object. The relative motion can be circular or linear. These data are then backprojected to reconstruct the two-dimensional image of the object cross section.

Noninvasive measurement of local arterial pulse wave velocity in humans by ultrasound.

An improved method for noninvasive measurement of the local velocity of arterial pulse wave propagation by an echo-tracking-based ultrasound system is described. A data acquisition image interface was programmed in the ultrasound machine simultaneously to record M-mode ultrasound signals at two locations of a given distance apart along an artery. The selections of measurement sites, separation, and time resolution were performed on the control interface.

Coherent ultrasonic Doppler tomography.

Ultrasonic imaging based on the pulse-echo principle is widely used throughout the world, particularly in medical applications. However, its spatial resolution is poor (around 2 times the wavelength, or 200 μm at 15 MHz), limiting its ability to detect small but clinically important lesions (such as microcalcifications in breast cancer). The work presented here is different from the traditional approach.

A tutorial on ultrasonic physics and imaging techniques.

Ultrasound is a widely used modality for both therapy and diagnosis in medicine and biology. Currently, in the field of medical diagnosis, ultrasound is responsible for about one in five of all diagnostic images. The physical characteristics of medical ultrasound, along with its behaviour as it interacts with biological tissues, are described in this tutorial.

Fetal radiation dose from CT pulmonary angiography in late pregnancy: a phantom study.

Pulmonary embolism (PE) is the leading direct cause of maternal mortality in the UK. Accurate diagnosis is important but, even though CT pulmonary angiography (CTPA) is the recommended imaging modality for PE in the general population, there is limited guidance for pregnant patients. Knowledge of the radiation doses to both the mother and the fetus is therefore important in the justification of CTPA in this situation.

Investigation of normal ranges for left ventricular ejection fraction in cardiac gated blood pool imaging studies using different processing workstations.

Background: An investigation has been undertaken to calculate normal ranges for left ventricular ejection fraction (LVEF) measured by the gated blood pool (GBP) technique. A common set of normal studies was used at 11 hospitals within the south of England to assess the variability of results and normal ranges.

Methods: Normal studies were identified by retrospective review of patients who had undergone a GBP study and echocardiogram at the Royal United Hospital, Bath.

Measurement of cartilage volumes in rheumatoid arthritis using MRI.

MRI is a valuable imaging modality for assessment of the articular cartilage in rheumatoid arthritis (RA) and is potentially of use in monitoring disease progression and response to therapy. In this study, we investigated the sources of error in volume measurements obtained by segmentation of MR images of knee cartilage in patients with RA and followed cartilage volume in a group of RA patients for 12 months. 23 RA patient volunteers were recruited for knee imaging.

No loss of cartilage volume over three years in patients with knee osteoarthritis as assessed by magnetic resonance imaging.

Objective: Magnetic resonance imaging (MRI) has the potential to provide accurate quantification of structural changes in joint disease, with sensitivity to change, as it can provide direct visualization of the cartilage and bone. In this study, we investigated whether knee cartilage volume, as assessed by MRI, is sensitive to change over time in patients with osteoarthritis (OA).

Design: Sixteen patient volunteers (10 male, six female) with established OA of the knee were entered into the study and demographic data recorded.

Physics and engineering: milestones in medicine.

The history of the development of the applications of physics and engineering in medicine provides an insight into contemporary practice and can help to mould the future. Physics and engineering form a continuum, and, in the present context, engineering is indistinguishable from applied physics. The modern scientific era, which extends over 500 years, is characterised by numerous significant developments: for example, the Nobel prizes which most closely relate to physics and engineering in medicine were for X-rays and radioactivity, the electrocardiogram, the scattering of radiation, the cyclotron, nuclear magnetic resonance, the transistor, radioimmunoassay and computed tomography; and a medical physicist has received the Peace Prize.

Continuous wave ultrasonic tomography.

As an object rotates with respect to a stationary ultrasonic beam, the scattering centers within the object return echoes that are Doppler-shifted in frequency by amounts depending on the velocities of the individual scatterers. The scattering centers that lie on a line of constant cross-range all have the same effective velocity in the direction pointing toward the transducer; therefore, the backscattered echo amplitude at any particular frequency is the line integral of the scattered radiation at the cross-range corresponding to that frequency. The amplitudes of the returned signals at other frequencies give the line integrals for the scatterers at the corresponding cross-ranges.

Advances in ultrasound: from microscanning to telerobotics.

This paper is in memory of W V Mayneord (1902-1988). Experiments conducted in Mayneord's laboratory were amongst the first to show that ultrasound had diagnostic potential. Now, one in every four imaging studies uses ultrasound.

On-line quantitative analysis of surface electromyography of the pelvic floor in patients with faecal incontinence.

Background: Needle electromyography (EMG) remains the 'gold standard' for the assessment of external anal sphincter innervation. It is, however, an invasive and poorly tolerated technique. In this study a quantitative form of surface electromyography was compared with needle EMG of the external anal sphincter.

Ultrasound in vascular pathologies.

The choice of the optimal ultrasonic frequency for vascular studies is determined by the required resolution and penetration. Anatomical real-time two-dimensional imaging and blood flow studies provide complementary information. Intravascular scanning allows high-frequency ultrasound to be used, with correspondingly good spatial resolution.

Doppler studies of the vascular system.

Ultrasonic Doppler methods are routinely used to study the vascular system. Flow and tissue motion information can be obtained by frequency and time domain processing. Instruments range in complexity from simple continuous wave devices without imaging capability through to advanced real-time 2D colour flow scanners and intravascular devices.

Further validation of the Elderly Mobility Scale for measurement of mobility of hospitalized elderly people.

Objective: To further assess the validity and inter-rater reliability of the Elderly Mobility Scale (EMS). Also whether the scale reflects elderly people's perceptions regarding their mobility, and whether it can predict discharge destination, or likelihood of falling.

Design: Questionnaire-based study completed on admission and weekly after this on all patients referred to physiotherapy for mobility problems over the course of one month.

Admission plasma glucose and diabetes mellitus in elderly admissions to hospital.

Over 6 months, all admissions to three geriatric wards were studied to define an admission plasma glucose level (APG) that identified previously undiagnosed diabetes mellitus. Subjects with APG> or =7.0 mmol l(-1) had a modified oral glucose tolerance test (OGTT) when well before discharge if their dose of steroid and/or thiazide was constant, and they were neither terminally ill nor dead; excluded were 1 subject on reducing steroid doses, and 9 moribund admissions without APG.

Diabetes and cognitive impairment: a community-based study of elderly subjects.

To ascertain whether diabetes in elderly people is associated with cognitive impairment, we offered all residents of Melton Mowbray aged 75, 80 and 85 years both a modified glucose tolerance test (1985 WHO criteria) and Folstein mental state examination (MMSE, 23/24 cut-off). Analysis of the results, stratified by age, revealed that subjects with known diabetes were more likely than normal subjects to have low MMSE [odds ratio 3.30 (95% CI 1.

Phantoms for studying the acceleration and turbulence of liquids using magnetic resonance imaging.

Magnetic resonance angiography is a relatively new method used to image vascular structure. However, a limitation manifested through signal loss due to non-stable flow makes this technique unreliable for directly visualizing occlusions and estimating the degree of stenosis. In this study, a quantitative approach is developed to understand further the situations where signal loss occurs and a phase mapping technique is used quantitatively to study acceleration in test objects designed to generate flow disturbance.

A comparative study of velocity measurements in major blood vessels using magnetic resonance imaging and Doppler ultrasound.

Velocity measurements in major blood vessels were obtained in studies of volunteers using magnetic resonance imaging (MRI) and compared with Doppler ultrasound (US). The vessels studied were the abdominal aorta, superior mesenteric artery, common carotid artery, superficial femoral artery and middle cerebral artery. Using a paired t-test, no significant difference was found between velocity values estimated by MRI and US (p > 0.

Blood flow measurement by Doppler ultrasound: a question of angles.

Ultrasound Doppler equipment is widely used to estimate blood velocity and volume flow. Recently there has been correspondence concerning the origin of the Doppler shift in blood vessels. The assumption that only the movement of the target need be considered is challenged by the observation that Doppler shifts occur where there is relative motion.

The development of equipment for the technical assessment of respiratory motion induced artefacts in MRI.

A device and technique to study the effects of respiratory motion on the quality of magnetic resonance images is proposed. The construction of the device enables a variety of test objects to be mounted and used in the evaluation of imaging parameters that may be affected by motion. The equipment is constructed of cast acrylic and the movement is actuated and controlled pneumatically thus ensuring that there are no interactions with the magnetic field and radiofrequency detection system to cause further image artefacts.

An image processing technique for the identification of contact pixels applied to x-ray CT images of implanted hip prostheses.

Uncemented prosthetic joint implants used in orthopaedic surgery are usually coated with a porous surface to encourage bone ingrowth. Better contact between the endosteal bone and the porous surface improves ingrowth, and such contact may be increased if the joint further subsides into position in the first weeks following implantation. An image processing technique has been developed as part of a study undertaken to determine the effect of early subsidence on endosteal contact.

Milestones in cardiac ultrasound: echoes from the past. History of cardiac ultrasound.

Although the antecedents of cardiac ultrasound can be traced back to the 1870s, it was in 1954 that Edler and Hertz published their milestone paper. M-mode echocardiography reached its peak in the early 1970s, when the fibre-optic recorder made the method clinically viable. It was not long before real-time two-dimensional imaging was developed, however, and the invention of pulsed Doppler laid the foundation of duplex scanning.

Soft-tissue localization of 99mTc-hydroxymethylene diphosphonate due to interaction with calcium.

Soft tissue localization of 99mTc-labelled bone imaging agents is often associated with high calcium levels either locally or systemically. This could be due to the formation of a large molecular complex after administration of the radiopharmaceutical. We have investigated the formation of such a complex between 99mTc-hydroxymethylene diphosphonate (HMDP) and calcium by a number of techniques.