Characterization of the ultrasound beam produced by the MIST therapy, wound healing system.

The MIST Therapy wound healing device (Celleration, Eden Prairie, MN, USA), which uses low-frequency ultrasound to deliver an atomized saline spray to acute wounds, was evaluated in a laboratory environment. The output of the MIST device was characterized by its frequency, transmission in the presence and absence of the saline spray and intensity. When measured up to 500 mm away from the transducer tip, the transmission of 39.5 kHz ultrasound was not significantly attenuated by the saline itself. In the absence of the saline spray, the acoustic intensity range of the MIST device was calculated to be 429-188 mW cm(-2) across the manufacturer-specified treatment range (12.5-20 mm). Because of the acoustic impedance mismatch between air and soft tissue, the MIST Therapy device would deliver only 0.1% of this incident intensity into the wound site.

Joint recommendations for reporting carotid ultrasound investigations in the United Kingdom.

At present in the United Kingdom a number of different criteria are used to grade disease in carotid ultrasound investigations. One main cause of this has been the difference in the method of grading angiograms used in the NASCET and ECST large carotid surgery trials. It is desirable that all centres reporting carotid ultrasound investigations report to the same standard. This paper presents recommendations for the reporting of ultrasound investigations of the extra cranial arteries produced by a Joint Working Group formed between the Vascular Society of Great Britain and Ireland, and the Society for Vascular Technology of Great Britain and Ireland. The recommended criteria are based on the NASCET method of grading carotid bulb disease. Key recommendations include recording peak systolic velocity (PSV) and end-diastolic velocity (EDV) in both internal and distal common carotid arteries; measuring all velocities at a Doppler angle of 45-60 degrees; the use of internal carotid PSV of >1.25 ms(-1) and >2.3 ms(-1) and a Peak Systolic Velocity Ratio of >2 and >4 to indicate >50% and >70% stenosis respectively; and the use of the St Mary's Ratio to grade >50% stenoses in deciles. General recommendations are also given for the acquisition, interpretation and reporting of the data.

The role of duplex sonography and angiography in the investigation of carotid artery disease.

Some patients with symptomatic carotid stenoses of greater than 70 % benefit from carotid endarterectomy. This study was designed to compare the accuracy of duplex ultrasound with angiography in assessing the degree of carotid stenosis in 73 patients with symptoms of recent carotid territory ischaemia. Ultrasound was found to be most accurate in the group of patients with normal vessels or mild stenoses (0-29 %) when there was 90 % concordance between ultrasound and angiography. Ultrasound was found to be least accurate in the group of patients with severe stenoses (70-99 %) in whom it was more likely to underestimate than to overestimate the degree of stenosis. Only one patient said to have < 30 % stenosis on ultrasonography had a > 70 % stenosis on IADSA. Our results indicate that patients with normal arteries or mild disease shown by ultrasound have a very small chance of having surgically amenable lesions in the neck. Ultrasound is reliable as an exclusory screening test. However, all other stenoses should also be investigated by catheter angiography if surgery is considered. Taking angiography as the reference, only 52 % of patients with severe stenoses, which might be taken as an indication for surgery, were correctly identified on ultrasonography. Ultrasound alone is a poor technique for identifying patients for surgery and a combination of ultrasound screening with angiography for > 30 % stenoses detected by ultrasound is recommended.

Comparison of lower limb arterial assessments using color-duplex ultrasound and ankle/brachial pressure index measurements.

The strength of agreement between two noninvasive methods of assessing lower limb arterial disease and their relationship to patient symptoms following exercise have been investigated. Color-duplex ultrasound (CDU) and ankle/brachial pressure index (ABPI) (before and afer exercise) measurements were obtained from 200 consecutive patients referred to a vascular investigations laboratory. From these patients, 290 limbs were available for study, comprising limbs without previous vascular surgery, from patients without diabetes and who could attempt a walking exercise test. The overall level of agreement between CDU and resting ABPI measurements was 83% (Kappa 0.66). The ABPI technique identified the more serious disease; a resting ABPI of less than 0.6 gave 100% agreement with CDU. With higher resting ABPIs the level of agreement became poorer: 83% (0.6 < or = ABPI <0.9) and 76% (normal ABPI > or = 0.9). The addition of postexercise ABPI measurements in determining significant arterial disease increased the strength of relationship between the two techniques by only 2% (85%, Kappa 0.69). The exercise test was generally limited by the most symptomatic limb in each patient, and the agreement between CDU and postexercise ABPI measurements in these limbs was higher at 93% (Kappa 0.81). In comparison, agreement for the least symptomatic group of limbs was found to be poor (69%, Kappa 0.37). Compared with symptoms after exercise, overall agreements with CDU and ABPI were both 67% (Kappa 0.27). The agreement was better (91%) when the resting ABPI was less than 0.6. The ABPI is biased toward the detection of more severe disease and is more consistent with CDU when the most symptomatic limbs are compared. The relationship between either test and symptoms after exercise is strong only for limbs with major disease.

The use of duplex ultrasound in the assessment of arterial supply to the penis in vasculogenic impotence.

Impotence may be caused by arterial disease affecting the vessels supplying the corpora cavernosa. Color duplex ultrasound was used to measure the peak systolic velocity and systolic rise time in the deep penile arteries in 22 impotent men following papaverine stimulation. The results were compared with the findings of selective internal pudendal pharmaco-arteriography. A further comparison was made using color duplex ultrasound with 37 impotent men who all responded well to papaverine. A systolic rise time of 110 msec. or more was found to be the best discriminant of disease in the arteries supplying the corpora giving a positive predictive value of 0.92. A long systolic rise time in a papaverine responder may indicate that the arterial supply is borderline or that the arterial flow is maximal and that the problem lies on the sinusoidal-venous side. It appears that in the absence of a pathological condition there is a large surplus arterial supply.

The assessment of carotid and vertebral arteries: a comparison of CFM duplex ultrasound with intravenous digital subtraction angiography.

The use of duplex ultrasound with colour flow mapping is compared with that of intravenous digital subtraction angiography (IVDSA) in the investigation of carotid and vertebral artery disease. Ninety-nine carotid and vertebral arteries were examined independently by IVDSA and ultrasound for location and degree of disease in 30 men (mean age 58) and 20 women (mean age 53). For purposes of comparison the carotid tree was divided into six segments. In 46% of cases no disease was detected by either modality. In 36% of cases where disease was found, ultrasound found mild disease in arteries reported as normal by IVDSA. Both modalities detected the six cases of total occlusion found in the study. IVDSA underestimated five cases of major disease found by ultrasound at the bifurcation or in the bulb. Overall agreement in grading vessel segments was good, with 74.5% in complete agreement and 90.3% grading stenoses to within +/- 25% of the other modality. There was good qualitative agreement in the findings for vertebral arteries. In four patients conventional arteriography was also available for comparison.

The role of colour duplex ultrasonography in the diagnosis of vasculogenic impotence.

Colour duplex ultrasonography was used to obtain peak systolic velocity (PSV) readings from cavernosal arteries at rest and during papaverine-induced tumescence. Results from 31 men with vasculogenic impotence were compared with those from 17 men with non-vasculogenic impotence and a control group of 6 potent men. In the flaccid state no significant differences in PSV readings were found between the vasculogenic and control groups. Following the injection of papaverine, men from the vasculogenic group without venous leakage were alone in having significantly lower PSV readings compared with the potent controls. All 23 men with normal penile haemodynamics had a mean PSV greater than or equal to 20 cm/s during tumescence. This was also the case for 19 (61%) of the vasculogenic group, including 9 (69%) of the 13 patients with venous leakage. The remaining 12 men in the vasculogenic group (39%) had a mean PSV less than 20 cm/s, this being diagnostic of an inadequate arterial inflow. Colour duplex ultrasonography can identify patients who have marked arterial insufficiency as the major cause of their impotence and hence allows more rational selection for angiography and revascularisation. Lesser degrees of arterial deficit are difficult to characterise using mean PSV readings alone.

Towards an ideal blood analogue for Doppler ultrasound phantoms.

If a phantom is to produce Doppler spectral waveforms accurately matching those that would be obtained in vivo, it is necessary to use a fluid that behaves like blood in vivo, both acoustically and rheologically. The use of blood itself is undesirable and an analogue is required. Blood exhibits non-Newtonian behaviour as a result of aggregation of erythrocytes at low shear rates. This behaviour affects flow not only in sub-millimetre diameter vessels, but also in large scale structures. An alternative to blood is described that uses finely powdered nylon suspended in a mixture of glycerol and water. The nylon particles used have dimensions and density close to those of erythrocytes and they aggregate at low shear rates to give non-Newtonian behaviour. Viscosity may be varied over a wide range by the addition of liquid detergent. Consideration is given to the importance of haematocrit in modelling pulsatile and disturbed flows as it affects the haemodynamics of flow and the backscattered power of an ultrasound beam. This adaptable blood analogue is suitable for use in models of both large structures and fine vessels.

Combined use of Doppler and conventional ultrasound for the diagnosis of vascular and other lesions in the head and neck.

Twenty-three patients with swellings of the head and neck were prospectively investigated by Doppler ultrasound and ultrasound imaging to determine the type and vascularity of the lesions and thereby aid pre-operative diagnosis. Four vascular lesions were correctly identified while vascularity was not found in patients with lipoma, cysts, abscess, or muscular hypertrophy. Increased vascularity was found in or near some tumours and lymphangiomas, but by careful comparison of findings these lesions were not confused with true vascular lesions. The value of the investigations was demonstrated by a change in the treatment in 6 of the cases in this series.

The use of a Diasonics DRF400 duplex ultrasound scanner to measure volume flow in arterio-venous fistulae in patients undergoing haemodialysis: an analysis of measurement uncertainties.

A pilot study to measure volume flow in arterio-venous fistulae in patients undergoing haemodialysis was undertaken to determine the accuracy and precision of values obtained using a modern duplex ultrasound scanner. A Diasonics DRF400 duplex ultrasound scanner was used with a small parts 10 MHz mechanical sector probe incorporating a 4.5 MHz Doppler transducer. Volume flow was measured in the brachial artery of 13 patients with surgically created arterio-venous fistulae in the distal circulation. Volume flow was also measured using a flow phantom in which the true volume flow was known. An analysis of the measurements made by the duplex scanner was performed to determine the sources of random and systematic uncertainty. Repeatability was improved with the probe clamped in position over the brachial artery giving a coefficient of variation in repeated measurements of volume flow in a patient of +/- 12%. Measured flows ranged from 884-3088 mL min-1. Comparison with measurements on the flow phantom showed these values from patients to be overestimated by 200-600 mL min-1. The values from the phantom should therefore be used to calibrate patient measurements. Analysis of uncertainties showed that precision was limited by random uncertainties in the measurement of vessel diameter and Doppler angle.