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Biomedical subjects

E N Coleman

Publications and source records attributed to E N Coleman.

At least 19 recordsLinked to original sources
PubMed1992

Feasibility of estimating the temperature distribution in a tumor heated by a waveguide applicator.

The feasibility of using a 2-dimensional (2D) modeling approach for retrospectively describing complete temperature distributions in the midplane of a tumor during a clinical hyperthermia treatment was tested. An experimental treatment, using a 915-MHz waveguide applicator to heat a large melanoma in a dog, was modeled. Detailed measurements of temperatures were made during the treatment. The steady-state blood flow distribution at the midplane was imaged by positron emission tomography (PET), and these data were used to prescribe the modeled perfusion pattern. A 2D finite element method (FEM) was used to approximate the solution to Maxwell's Equations to obtain the specific absorption rate (SAR) distribution. The blood-flow estimates, assumed material properties, SAR distribution, and temperature boundary conditions were then used with the same mesh in a second FEM program to obtain a solution to the bioheat transfer equation. This latter routine was embedded in a state-and-parameter-estimation program that systematically varied selected parameters until the differences between computed and measured temperatures were minimized. Optimizations were performed independently for three subsets of the measured temperature data to assess the sensitivity of the predicted temperature field to the number of measurements. The calculated temperature distributions that resulted were similar to each other, and the predicted temperatures at the sensor points excluded from these optimizations were in reasonable agreement with the measurements. However, lack of unique blood flow values following optimization indicates that the methods of estimating blood flow will need to be improved or that there are problems with model mismatch. This work is a clinical case study of an evolving 2D system of thermal dosimetry which relies on both empirical and theoretical concepts. The methodology is being evaluated for its ability to generate prognostically significant descriptors of the treatment temperature field.

Animals↗
PubMed1991

Doppler ultrasound and the silent ductus arteriosus.

A clinically undetectable, small ductus arteriosus was identified by Doppler ultrasonography in 21 individuals. Infants were excluded from the study and no patient had pulmonary hypertension. Persistence of the ductus arteriosus is likely to be more common than shown by less sensitive diagnostic methods. Some patients considered to have infective endocarditis with a normal heart may have a silent ductus arteriosus. Evidence of such an association would justify ligation or antibiotic cover as prophylactic measures.

Adolescent↗
PubMed1989

Normal limits of the high-fidelity pediatric ECG. Preliminary observations.

A study of more than 1,780 neonates, infants, and children was carried out, using a digital electrocardiograph with a sampling rate of 500 per second, to revise the normal limits of the pediatric ECG. The 12-lead ECG was used with V4R replacing V3. All leads were recorded simultaneously off-line in digital form on magnetic tape and were subsequently analyzed using well-established computing techniques. The results showed that the upper 98 percentile limit of normal amplitudes could be up to 46% higher than previously published limits. Differences in some mean values were very much higher, though these are of less clinical significance. In addition, QRS durations were found to be wider than previously published data. Sex-related differences could be demonstrated in both amplitude and duration measurements, particularly in the early adolescent years. This study confirms that to record pediatric ECGs with high fidelity, it is necessary to use equipment that converts the ECG from analog to digital form at a rate of 500 samples/sec. Significant errors in amplitude and duration measurements may be expected if a much lower sampling rate is utilized.

Adolescent↗
PubMed1989

Doppler flow characteristics in the assessment of pulmonary artery pressure in ductus arteriosus.

The Doppler spectral pattern of flow through the ductus arteriosus was studied in 117 patients. In 37 who underwent catheterisation, Doppler records and aortic and pulmonary artery pressure were available (21 simultaneously with two catheters) for review while the others had surgical ligation of the duct on the basis of the results of non-invasive tests. Four flow patterns were obtained: (a) continuous flow, maximum velocity in late systole with gradual fall throughout diastole; (b) continuous flow, high systolic flow with rapid fall to a very low early diastolic velocity maintained throughout diastole; (c) continuous low velocity, maximum in late diastole; and (d) bidirectional flow. Flow pattern (a) was associated with normal or slightly raised pulmonary artery pressure; (b) with raised pulmonary artery pressure; and (c) and (d) with pulmonary artery pressure at systemic values. Comparison of the Doppler and measured pressure differences between the great arteries was reasonably good for peak values but poor for the trough readings. Doppler ultrasound clearly showed ductal flow; the flow pattern gave an indication of the pulmonary artery pressure, but pressure measurement by application of the Bernoulli equation to the flow velocities cannot yet be regarded as reliable.

Adolescent↗
PubMed1988

Doppler assessment of the interventricular pressure drop in patients with ventricular septal defects.

Doppler ultrasound was used to assess the pressure drop between the ventricles in 109 infants and children (61 less than two years old) with a ventricular septal defect who underwent cardiac catheterisation. The pressure in both ventricles was measured at catheterisation in 103 patients either simultaneously through two catheters (41) or with a single catheter withdrawn across the septum or removed from one ventricle to the other (62). When pressure was measured simultaneously with two catheters (41 patients) the peak to peak and instantaneous gradients showed a maximum difference of 20 mm Hg with levels within 10 mm Hg of each other in 36. Comparison of the difference in the gradients with the average of the measurements demonstrated a tendency for Doppler to underestimate the difference when it was high (greater than 50 mm Hg) and overestimate it when it was low. A Doppler estimate of a low pressure difference between the ventricles indicates pulmonary arterial hypertension and a high one low pulmonary artery pressure, but in the intermediate group Doppler is as yet not sufficiently sensitive to allow selection of those patients who require further investigation and possible operation. Doppler ultrasound was found to be a sensitive method of detecting a very small ventricular septal defect. Thus although Doppler is a very useful means of assessing and following patients with a ventricular septal defect, further studies are required to determine its exact place in clinical practice.

Adolescent↗
PubMed1987

Doppler ultrasound in the assessment of severity of coarctation of the aorta and interruption of the aortic arch.

Doppler ultrasound was used to investigate 48 infants and children (age 2 days-16 years, weight 1.0-58 kg) with aortic arch abnormalities. In only 38 of the 42 with an important coarctation was an increased blood flow velocity from the distal arch demonstrated. In three with interruption of the aortic arch an increased velocity recorded from the region of the distal arch was thought to represent ductal flow. There was little difference between the peak to peak and instantaneous maximum gradients in the 20 patients with important coarctation in whom direct pressure measurements both proximal and distal to the obstruction were made at catheterisation. There were poor agreements between Doppler and measured peak to peak and instantaneous gradients in the 17 patients found to have both an increased velocity and important coarctation. It is concluded that although an increased blood flow velocity in the distal arch is usually demonstrated in coarctation this may not occur with severe obstruction. Furthermore, the maximum velocity is not related to the anatomical severity of the obstruction and the Doppler estimate of pressure drop in coarctation may not even reliably predict that measured at catheterisation.

Adolescent↗
PubMed1986

Doppler ultrasound in the estimation of the severity of pulmonary infundibular stenosis in infants and children.

Pressure gradients estimated by Doppler echocardiography were compared with values obtained at cardiac catheterisation in 31 children (aged seven days to 16 years, mean 2 years 7 months) with pulmonary infundibular stenosis including 16 with tetralogy of Fallot. Various parasternal and subcostal positions were explored to obtain the maximum velocity of blood flow and the obstructive gradient was calculated from the modified Bernoulli formula. The gradient across the obstruction could be measured directly at the time of catheterisation in only 21 patients. The correlation coefficient for the Doppler and total measured gradients was r = 0.90 for catheter entry and r = 0.77 for catheter withdrawal. Doppler ultrasound, by measuring the total gradient from the right ventricle to the pulmonary artery, provides a non-invasive assessment of the severity of pulmonary stenosis, and in those with infundibular obstruction allowance need not be made for possible energy losses caused by the elongated obstruction or the presence of narrowing at more than one level.

Adolescent↗
PubMed1985

The severity of pulmonary valve or artery obstruction in children estimated by Doppler ultrasound.

Doppler echocardiographic estimation of pressure gradient has been compared to that measured at cardiac catheterisation in 37 children, 6 weeks to 15 years of age, with suspected pulmonary valve stenosis or a pulmonary artery band. Various parasternal and subcostal positions were explored to obtain the maximum velocity of blood flow and the valve gradient was calculated from the modified Bernoulli formula. The Doppler study was performed at the time of catheterisation in 19, the maximum velocity being measured during catheter withdrawal in 7, immediately after withdrawal in 7, and while simultaneous right ventricular and pulmonary arterial pressures were measured in 5. Five other patients were studied within 24 hours of catheterisation and the other 13 within 6 months. Comparison of Doppler and catheterisation gradients showed a close correlation, this being particularly good where simultaneous right ventricular and pulmonary arterial pressures were measured. Doppler now provides an accurate non-invasive measurement of the severity of pulmonary valve stenosis and the adequacy of a pulmonary artery band.

Adolescent↗
PubMed1982

Complete congenital heart block. Report of 35 cases.

Congenital complete atrioventricular block is uncommon, and the outlook is usually regarded as favourable. Thirty-five patients with congenital heart block are presented. There was no obvious sex difference and their ages ranged from 12 days to 85 years, though most were under the age of 20 years when first seen. Accompanying heart disease was noted in six, but presentation with symptoms in early infancy was a more serious risk factor in our experience. Permanent pacing was required in 21, three of whom were neonates. One of the 14 unpaced patients died unexpectedly at the age of 5 years. Long term supervision is necessary, as most will require permanent pacing before their 50th birthday.

Adolescent↗
PubMed1982

The management of congenital aortic stenosis.

The progress of 128 patients with congenital aortic stenosis has been followed from one to 28 (mean 14) years. Fifty-eight underwent cardiac catheterisation, and 46 (36% of the total) required surgical treatment. Of these, 42 were under 20 years old. Additional cardiac lesions were noted in five. Infective endocarditis was encountered in four. The onset of symptoms or increasing evidence of left ventricular hypertrophy on the electrocardiogram were the principal indications for catheterisation. Two-dimensional echocardiography is now important in this context. There were four deaths in the 46 surgically treated patients; three of these were early and the fourth was a late death three years after operation due to a massive cerebral embolus complicating infective endocarditis. The 42 survivors of operation and the 82 unoperated patients have remained under long-term supervision. Further surgery was necessary in 12 of the 42 surgically treated patients--valve replacement in seven of them two to eight years after valvotomy, replacement of a calcified xenograft valve in three, and repeat operation in two because of recurrence of subvalvar obstruction. Aortic stenosis is not a benign condition in childhood and adolescence. Close supervision is necessary and when any deterioration is detected further investigation as a prelude to probable surgery is mandatory. This should not be embarked on lightly in childhood unless there are pressing indications, particularly in view of the serious disadvantages of valve replacement in childhood.

Adolescent↗
PubMed1981

Two-dimensional echocardiography in infants with persistent truncus arteriosus.

Two-dimensional echocardiography was used to study a consecutive series of 13 infants with persistent truncus arteriosus. In all a single great artery with the long upward course characteristic of the aorta was shown. This great artery could be identified as a persistent truncus arteriosus by the recognition of a branch arising from its ascending part (10 out of 13) or of more than three semilunar valve cusps (5/13). These criteria allowed the correct diagnosis to be reached in 12 of the 13 infants.

Diagnosis, Differential↗
PubMed1979

Pulmonary hypertension accompanying ventricular septal defect and patent ductus arteriosus. Management in infancy and early childhood.

Forty-one infants and children with the combination of patent ductus arteriosus (PDA) and ventricular septal defect (VSD) were encountered over 20 years. Twenty-four presented in infancy with congestive cardiac failure. Pulmonary hypertension was present in 32, the cause in 19 being increased pulmonary blood flow. Increased pulmonary vascular resistance (PVR) was detected in 13 (indicated by a pulmonary to systemic resistance ratio (Rp : RS) greater than 0.24:1 and PVR greater than 4 units). Thus 22% had a pulmonary artery systolic pressure less than 30 mmHg and 68% had a pulmonary vascular resistance below four units, indicating an unusually mild form of the combined condition in these patients. Surgical management is discussed, and in particular the question of simultaneous closure of the defects during infancy. Cardiac failure, resistant to drug treatment, and increased PVR are indications of operation. The PDA should be closed and only if there is no substantial fall in pulmonary artery pressure is the VSD repaired.

Child↗
PubMed1978

Echocardiographic identification of aorta and main pulmonary artery in complete transposition.

No completely reliable echocardiographic technique has been described for the separate identification of the aorta and main pulmonary artery in complete transposition of the great arteries. A mechanical wide-angle (60 degrees) sector scanner has been applied to this problem in 17 infants and young children, including 8 newborns before angiocardiography. In all patients a longitudinal scan (saggital section) identified the main pulmonary artery by its directly posterior course immediately beyond the pulmonary valve, and the aorta by its retrosternal course upwards before turning posteriorly above the main pulmonary artery. In addition, a high transverse scan showed the precise spatial relation of the great arteries, and, in 11 of the 17, tilting the scanning plane upwards showed branching of the main pulmonary artery. In 8 infants examined with M-mode echocardiography, an upward sweep from the pulmonary valve showed abrupt termination of the echo from the posterior wall coinciding with the posterior arching of the main pulmonary artery.

Aorta, Thoracic↗
PubMed1977

Two-dimensional echocardiography with a wide angle (60 degrees) sector scanner.

A wide angle (60 degrees) sector scanner producing a real-time two-dimensional echocardiogram has been used to examine healthy infants, children, and adults. Its method of use is described and findings from longitudinal and transverse scans are presented. The points of difference between the various types of electronic and mechanical two-dimensional scanning systems are discussed. This equipment minimises problems of chest contact and rib and lung interference and, by providing echocardiograms of high line density from a wide angle, is a suitable real-time two-dimensional scanning system for examining patients of all ages.

Adult↗
PubMed1977

Modified axial lead system in children.

Preliminary studies have been made on the use of the modified axial lead system in infancy and childhood. A highly significant correlation between internipple distance and height suggested that internipple distance be used as an index for the selection of a template to facilitate placement of the chest electrodes (Z and X). A series of 4 triangular templates was designed. The use of a template one size too large or too small was shown not to lead to any significant error in waveform measurement. A further study showed that the reference level for the application of the praecordial electrodes should be the 5th intercostal space as for adults, but that no serious diagnostic error was likely to arise if the 4th or 6th intercostal space was chosen by mistake. A study of the Frank lead system suggested that the use of the 5th intercostal space as a reference level was more appropriate than the 4th intercostal space, which is generally adopted by users of that system. The conclusion reached was that the axial lead system is the preferred orthogonal lead system for children, with templates for 4 ranges of internipple distance (less than 10 cm; 15 to 20 cm; and less than 20 cm--adult build) being proposed to simplify electrode placement.

Adolescent↗