Versatile microcomputer-based system for the capture, storage and processing of spectrum-analysed Doppler ultrasound blood flow signals

Compensatory fuzzy neural networks-based intelligent detection of abnormal neonatal cerebral Doppler ultrasound waveforms

Compensatory fuzzy neural networks (CFNN) without normalization, which can be trained with a backpropagation learning algorithm, is proposed as a pattern recognition technique for intelligent detection of Doppler ultrasound waveforms of abnormal neonatal cerebral hemodynamics. Doppler ultrasound signals were recorded from the anterior cerebral arteries of 40 normal full-term babies and 14 mature babies with intracranial pathology. The features of normal and abnormal groups as inputs to pattern recognition algorithms were extracted from the maximum velocity waveforms by using principal component analysis. The proposed technique is compared with the CFNN with normalization and other pattern recognition techniques applied to Doppler ultrasound signals from various arteries. The results show that the proposed method is superior to the others, and can be a powerful technique to be used in analyzing Doppler ultrasound signals from various arteries.

Evaluation of an automated real-time spectral analysis technique

An adaptive real-time Doppler peak-frequency tracing algorithm was evaluated in vitro and compared to manual peak-frequency traces. A computer-controlled pump was used to generate physiological flow waveforms in a vasculature-mimicking phantom. Spectral waveforms were obtained on an ATL HDI along with real-time estimates of diagnostic parameters, including maximum systolic, minimum diastolic, time-averaged peak frequencies and pulsatility and resistance indices. The effect of the signal-to-noise ratio on the measured parameters was investigated. The imprecision in the measured parameters was found to depend somewhat on the waveform shape; e.g., the imprecision in PI was 4.1% for a normal renal waveform and 8.5% for a waveform having reverse diastolic flow. The peak frequency envelopes of the same waveform data were traced manually by nine operators, and the resulting diagnostic parameters were compared to ones obtained from automated peak-frequency traces of the same waveform data. The agreement between parameters measured by the automated routine and those measured manually was found to depend somewhat on the waveform shape; e.g., the bias in the PI was 1.3% for a renal waveform lacking diastolic flow, and 12% for a waveform with reverse diastolic flow. The between-observer variations in the manual measurements ranged from 0.8% up to 9.4%. The overall variations associated with the automated traces were found to be smaller than or equal to those of the manual traces.

The use of a calcium-channel blocker, nicardipine, for severely asphyxiated newborn infants

A continuous infusion of nicardipine was given to four severely asphyxiated fullterm infants who were at high risk for adverse outcome and had abnormal cerebral Doppler haemodynamic studies. The heart rate increased in all four infants and mean arterial blood pressure (MAP) fell in three. Two infants had a sudden and marked fall in MAP, together with severe impairment of skin blood-flow and a concurrent fall in cerebral blood-flow velocity. The serum level of nicardipine was less than 40ng/mL in all cases. The use of nicardipine, and possibly other calcium-channel blockers, may be associated with marked hypotension, and if there is no cerebral autoregulation, may cause further cerebral hypoperfusion, so use of these drugs in asphyxiated newborn infants should only be attempted if blood pressure is carefully monitored.

Studies on the pathogenesis of the early dumping syndrome induced by intraduodenal instillation of hypertonic glucose

A reaction indistinguishable from the early dumping syndrome was induced in four of nine normal volunteers by intraduodenal instillation of a hypertonic glucose meal. Tachycardia and marked peripheral vasodilatation were demonstrated in 'dumpers' by Doppler ultrasound measurements of the arterial blood flow signal. The dumping reaction was not detectably altered by the addition of guar to the meal. Plasma VIP concentration rose and plasma volume fell to a similar degree in 'dumpers' and 'non-dumpers', suggesting that neither event is an integral component of the dumping mechanism. In contrast, the rates of rise of blood glucose and enteroglucagon concentration were markedly greater in 'dumpers'. The results are inconsistent with the conventional explanation that the early dumping syndrome is caused by a large osmotic fluid shift, but are compatible with a mechanism involving an initial period of intestinal hypermotility.

Severe birth asphyxia and abnormal cerebral blood-flow velocity

Thirty-four fullterm infants with postasphyxial encephalopathy (PAE) were studied with ultrasound to assess cerebral blood-flow velocity (CBFV). A control group of 126 healthy infants also had CBFV recordings during the first week of life. Measurements for the majority of the asphyxiated group fell into two abnormal patterns in relation to the control group: four had low CBFV (less than 2 SD below the mean) and 17 had high CBFV (greater than or equal to 2 SD above the mean); all had severe PAE. Median age at the first high measurement was 26 hours. There were no statistically significant differences between infants with normal and abnormal CBFV in measurements of PaCO2 or mean arterial blood-pressure. A Pourcelot Resistance Index (PRI) less than 0.55 was common in the presence of high CBFV, but never seen with low measurements. 21 of the 34 infants died of their asphyxial insult and four of the survivors have severe cerebral palsy at a median age of two years. Three of the four with low CBFV died, and no infant with CBFV greater than 3 SD survived without severe impairment. The positive predictive value of CBFV measurements less than 2 SD or greater than 3 SD for death or severe impairment is 94 per cent, compared with 83 per cent for low PRI alone. The authors believe that high CBFV is the result of vasoparalysis of cerebral arterioles and that it represents a form of irreversible cerebral injury.

A pulse-foot-seeking algorithm for Doppler ultrasound waveforms

A simple algorithm for detecting and flagging the start of the systolic upstroke or 'pulse foot' of Doppler ultrasound waveforms is described. It operates in three stages. It first locates the true maximum of each waveform, it then works back to the point of maximum gradient on the upslope of the waveform, and finally works back to the maximum rate of change of gradient at the foot of the waveform. The algorithm has been used to process the Doppler signals from over 150,000 individual cardiac cycles and has only been completely defeated by signals which, on review, have been considered too noisy for further analysis.

Cerebral artery Doppler ultrasonography for prediction of outcome after perinatal asphyxia

43 term infants with clinical neurological manifestations of intrapartum asphyxia and who survived for more than 2 days were studied sequentially, while in hospital, with doppler ultrasound examination of the anterior cerebral arteries. 36 survivors with post-asphyxial encephalopathy were followed up for a median of 18 months and none who had had normal doppler measurements (defined by results in 49 non-asphyxiated babies) became seriously handicapped. Of the 18 infants with abnormal waveforms 12 had an adverse outcome (death or handicap). In the asphyxiated infants, doppler examination predicted outcome with an accuracy of 86%. The prediction of adverse outcome by abnormal doppler showed a sensitivity of 100% and a specificity of 81%. All abnormal results had occurred by 62 hours from birth.

Haemodynamic assessment of the femoropopliteal segment: comparison of pressure and Doppler methods using ROC curve analysis

Combined aorto-iliac and femoropopliteal vascular disease remains a problem in vascular surgery. Arteriography does not provide information on the relative contributions of the two lesions to the presenting symptoms. Aorto-iliac haemodynamics may reveal occult aorto-iliac disease but does not show whether combined proximal and distal reconstruction will be required to provide symptomatic relief. Haemodynamic assessment of both segments may help in this respect. A haemodynamic assessment of the femoropopliteal segment of 72 limbs in 38 patients is reported. The segmental pressure drop between a common femoral arterial cannula and a below-knee occlusion cuff is compared with a non-invasive Doppler method combining both transit time and damping factor. Comparison is made using receiver operating characteristic (ROC) curve analysis. The measurement of segmental pressure drop is more accurate than the Doppler method in detection of femoropopliteal stenoses of greater than 50 per cent of the luminal diameter (P less than 0.05).