PubMed Health⌕ Search

Biomedical subjects

H G Bogren

Publications and source records attributed to H G Bogren.

At least 19 recordsLinked to original sources
PubMed2001

Prevalence and importance of pneumothoraces visualized on abdominal computed tomographic scan in children with blunt trauma.

BACKGROUND: Chest radiographs are routinely obtained for the identification of pneumothoraces in trauma patients. Computed tomographic (CT) scanning has a higher sensitivity for the detection of pneumothoraces, but the prevalence and importance of pneumothoraces detectable by CT scan but not by chest radiography in children sustaining blunt trauma is unclear. METHODS: We conducted a prospective observational cohort study of children less than 16 years old with blunt trauma undergoing both abdominal CT scan and chest radiography in the emergency department of a Level I trauma center over a 28-month period. All abdominal CT scans were interpreted by a single faculty radiologist. The chest radiographs of all patients with pneumothoraces detected on CT scan as well as a random sample of chest radiographs from pediatric blunt trauma patients without pneumothoraces on abdominal CT scan (in a ratio of four normals per pneumothorax) were reviewed by a second faculty radiologist. Both radiologists were masked to all clinical data as well as to the objective of the study. RESULTS: Five hundred thirty-eight children underwent both abdominal CT scan and chest radiography in the emergency department. Twenty patients (3.7%; 95% confidence interval [CI], 2.3-5.7%) were found to have pneumothoraces on CT scan. Of these 20 patients, 9 (45%; 95% CI, 23-68%) had pneumothoraces identified on initial chest radiography and 11 patients did not ("unsuspected pneumothoraces"). Twelve pneumothoraces were identified in these 11 patients; 6 were graded as minuscule and 6 as anterior according to a previously established scale. One patient with an unsuspected pneumothorax underwent tube thoracostomy. None of the 10 patients (0%; 95% CI, 0-26%) with unsuspected pneumothoraces who were managed without thoracostomy (including two patients who underwent positive pressure ventilation) had complications from their pneumothoraces. CONCLUSION: Less than half of pediatric blunt trauma patients with pneumothoraces visualized on abdominal CT scan had these pneumothoraces identified on initial chest radiograph. Patients with pneumothoraces identified solely on abdominal CT scan, however, uncommonly require tube thoracostomy.

Abdominal Injuries↗
PubMed2000

Four-dimensional aortic blood flow patterns in thoracic aortic grafts.

Time-resolved cardiac gated three-directional velocity data obtained with magnetic resonance velocity-encoded phase contrast sequences were used to study blood flow patterns in thoracic aortic grafts. Twelve patients were studied, 6 with traumatic descending aortic pseudoaneurysms, 3 with atherosclerotic aneurysms, and 3 with dissecting aneurysms. All grafts had an inflow jet; outflow jet; and/or vortices proximal, in, or distal to the graft. Flow abnormalities were generally mild in the descending aortic traumatic pseudoaneurysms seen in young people. The atherosclerotic aneurysms seen in elderly patients had the most abnormal flows with multiple vortices in and outside the graft. Blood persisted up to one and a half heartbeats in some vortices and took three to five heartbeats to flow from ascending to descending aorta compared with two to three in age-matched normal subjects. Rather large energy losses, probably up to 33% of the cardiac output in our worst case, may occur in thoracic aortic grafts.

Adult↗
PubMed1999

4D magnetic resonance velocity mapping of blood flow patterns in the aorta in young vs. elderly normal subjects.

Four-dimensional magnetic resonance MR velocity mapping was developed to study normal flow patterns in the thoracic aorta using time-resolved cardiac gated three-directional velocity data. Sixteen normal subjects were studied, one young group (average age 31 years) and one group with elderly people (average age 72 years). Blood flowed in a right-handed helix from the ascending aorta to the aortic arch. A straight flow pattern or a left-handed helix was seen in the descending aorta. Blood flow was never parabolic. Blood flowed forward in early systole, retrograde in mid-to-end systole, and forward again in diastole in all subjects as a basic pattern. Continuous retrograde flow over a long distance was not seen, but blood entered a retrograde flow column at various levels. In young people blood passed from the aortic valve to the mid-descending aorta in less than one heartbeat. In people in their sixties it took two heartbeats and in people older than 78 years, it took three heartbeats. The maximum systolic forward velocities were higher in young subjects than in elderly while the retrograde velocities were lower. J. Magn. Reson. Imaging 1999;10:861-869.

Adult↗
PubMed1999

Analysis of flow patterns using MRI.

This paper describes new software programs for analysis and visualization of blood flow patterns derived from time-resolved 3D velocity data sets. Using the programs, data can be displayed in cross-sectional or 3D perspective view. Particle paths revealing the flow patterns are computed by forward and backward time integration of the velocity field. Vector arrowmaps are computed as short-duration paths starting from uniformly spaced points over the lumen volume. Background, divergence, and local boundary correction is done to improve the realism of the paths. The programs have been used to visualize flow patterns from non-gated and cardiac-gated 3D velocity enclosed data in over 35 subjects. Arrowmaps are preferred for revealing local regions of different blood flow characteristics within the vessel, while particle paths are preferred for revealing global organization of the flow. They are complementary display strategies. Advanced data handling and display features are essential for analyzing and visualizing large velocity encoded data sets.

Adult↗
PubMed1999

Complex flow patterns in the great vessels: a review.

The article reviews the applications of magnetic resonance velocity mapping based on phase shifts in the protons to quantify blood flow velocity and blood flow volume. The method can be used to study normal physiology of blood flow in the aorta and its major branches, including forward and backward flow, to measure the aortic valve function in aortic valvular disease, stenosis and regurgitation, as well as pulmonary artery flow velocities in pulmonic insufficiency and regurgitation. Superior vena cava flows, pulmonary vein flows, left-to-right shunts, atrial and ventricular pulmonary conduit flows can also be measured. Two- and three-directional velocity mapping is reviewed and can be used to study three- or four-D flows in the aorta and the major arteries in great detail.

Aorta↗
PubMed1996

Magnetic resonance coronary angiography in heart transplant recipients.

BACKGROUND: Magnetic resonance angiography (MRA) using segmented k-space fast low-angle shot imaging has recently been used to demonstrate the proximal coronary arteries in healthy subjects and in patients with coronary artery disease. We assessed the sensitivity and specificity of coronary MRA in heart transplant recipients and investigated the feasibility of coronary MRA in patients with metallic sutures and clips in the chest. MATERIALS AND METHODS: Sixteen cardiac transplant patients aged 57.2 +/- 7.9 years (mean +/- SD) were recruited. Forty-eight arterial segments were evaluated, including the left main artery (LMA), left anterior descending artery (LADA) and right coronary artery (RCA). We excluded the left circumflex artery which could not be imaged accurately. The average time between heart transplant operation and MRA was 6 years, whereas that between MRA and X-ray angiography was 4 months. The coronary MRA was interpreted by two experienced investigators who were blinded to the coronary X-ray angiography results. Similarly, the coronary X-ray angiography results were interpreted by two experienced investigators blinded to the MRA results. The coronary arterial segments were classified by MRA as being normal or as having an amount of disease that was significant (> 50% lesion) or insignificant (< 50% lesion). RESULTS: There were 28 true-negative, five true-positive, four false-negative and six false-positive results. Of the 28 true-negative cases, 13 were in the LMA, six in the LADA and nine in the RCA. There was one false-positive LMA, two false-positive LADA and three false-positive RCA stenoses. There were four false-negative results in the LADA and one in the RCA. Clips precluded evaluation in one LMA, one LADA and one RCA. One LMA and one LADA were not evaluated as a result of poor images. One false-positive RCA stenosis was caused by a metallic clip. Three of the false-negative LADA stenoses had lesions in the distal third of the artery. The sensitivity, specificity, negative and positive predictive values were generally poor for the left coronary artery. The best results were for the RCA (sensitivity 100%, specificity 75%, positive predictive value 50% and negative predictive value 100%). The specificity in the left coronary arteries (LMA and LADA) was 86%, but the other indicators were all poorer. For the RCA, LMA and LADA combined, the overall sensitivity was 56%, specificity 82%, predictive accuracy 45% and negative predictive value 88%. In three patients, < 50% RCA lesions were seen in the MRA data, which were all confirmed by angiography. No < 50% lesions were seen in the LMA or in the LADA by MRA or by X-ray angiography. CONCLUSION: Coronary MRA using the segmented fast low-angle shot technique is feasible in heart transplant recipients but the sensitivity and specificity of this method are limited. Further developments in coil design, rapid imaging techniques and respiratory monitoring methods are necessary to improve the accuracy of coronary MRA.

Aged↗
PubMed1996

Assessment of coronary artery stenosis by magnetic resonance imaging.

OBJECTIVE: The findings of magnetic resonance and x-ray angiography were compared for assessment of coronary artery stenosis in this validation study. BACKGROUND: Magnetic resonance angiography of the coronary arteries has recently been described, but there has been no comparison with x-ray angiography of localisation or assessment of important characteristics of coronary stenosis. METHODS: A breath hold, segmented k-space, 2D gradient echo imaging technique incorporating fat suppression was used in 39 patients (55 coronary stenoses) with known coronary artery disease. RESULTS: Overall, 47 stenoses (85%) were assessed by magnetic resonance (29 of 33 stenoses in the left anterior descending artery, one of one in the left main stem, 14 of 17 in the right coronary artery, and three of four in the left circumflex artery were detected). There was close agreement between magnetic resonance and x-ray angiography for the distance of the stenosis from the arterial origin (magnetic resonance mean (SD) 27 (16) mm versus x-ray angiography 27 (16) mm, P = NS, mean difference -0.2 mm). The distance to 39 stenoses (83%) agreed to within 5 mm, with increased scatter for more distal stenoses. The severity of magnetic resonance signal loss, assessed visually at the site of stenosis, varied significantly according to the percentage diameter stenosis (F = 30, P < 0.0001); stenosis severity with severe signal loss was 89 (7)%, with partial signal was 70 (16)%, and with irregular wall only 37 (11)%, with significant differences among the three groups (P < 0.001). A significant correlation was found between the proportional magnetic resonance signal loss at the stenosis and the percentage diameter stenosis severity (r = -0.67, P < 0.0001). The length of stenosis measured by magnetic resonance (6 (3) mm) was greater than by x-ray angiography (5 (2) mm, P < 0.006, mean difference +1.1 mm). Spearman's rank test showed that there was significant overestimation of stenosis length by magnetic resonance as stenosis severity increased (rs = 0.34, P < 0.02). CONCLUSIONS: Accurate localisation of coronary stenosis and a qualitative assessment of stenosis severity are possible by magnetic resonance, but stenosis length is overestimated as severity increases, probably because of disturbed patterns of flow with turbulence distal to severe stenoses. Reasonable results for the detection of coronary artery stenosis by magnetic resonance were achieved in this highly selected population, but further progress in imaging techniques is necessary before moving towards appreciable clinical application.

Angina Pectoris↗
PubMed1995

Magnetic resonance velocity vector mapping of blood flow in thoracic aortic aneurysms and grafts.

Magnetic resonance imaging with multidirectional cine velocity mapping was used to study relationships between aortic blood flow patterns and the geometry of thoracic aortic aneurysms and grafts. Ten patients with 13 thoracic aortic aneurysms, single or multiple, or grafts (4) participated in the study. The causes of disease were atherosclerosis (4), Marfan's syndrome (2), trauma (1), and unknown (1), and there were two dissections. Spin-echo imaging and cine velocity mapping in 10 mm thick slices with vertical and horizontal velocity encoding were done. Maps of the two velocity components were processed into multiple computer-generated streaks whose orientation and length corresponded to velocity vectors in the chosen plane. The dynamic arrow maps were compared with previously reported aortic arrow maps from normal subjects. The forward flow occupied the entire lumen in the normal aorta in systole and small vortices were only present in the sinuses of Valsalva. Atherosclerotic aneurysms in the ascending aorta were located at the anterior right and had oblique, eccentric jet flows that created a large secondary vortex in the aneurysm. Patients with Marfan's syndrome had a central jet and two large vortices, one on each side. All other aneurysms, dissections, and grafts had irregular flows and vortices not seen in normal subjects. Magnetic resonance imaging with multidirectional velocity mapping is a powerful noninvasive tool to assess morphologic features and disturbed blood flow in aortic aneurysms and grafts. Recognizably altered flow patterns were found to be associated with altered vessel geometry. The significance of this requires further investigation.

Adult↗
PubMed1993

Measurement of coronary artery flow reserve by magnetic resonance velocity mapping in the aorta.

Coronary artery flow occurs predominantly in diastole via retrograde flow in the ascending aorta, some of which supplies the coronary arteries while the remainder recirculates in the ascending aorta. We used magnetic resonance velocity mapping to measure global coronary artery diastolic flow in the ascending aorta. In eight normal subjects and in four patients with possible ischaemic heart disease but with normal perfusion scans, the mean coronary flow reserve (CFR) was 269 ml/min. CFR was zero in seven patients with coronary artery disease. We have shown that CFR can be measured non-invasively with this technique.

Aorta↗
PubMed1989

The function of the aorta in ischemic heart disease: a magnetic resonance and angiographic study of aortic compliance and blood flow patterns.

Regional compliance of the ascending aorta, aortic arch, and the descending aorta was measured in 70 normal subjects at varying ages, in 17 patients with coronary artery disease (10 coronary artery disease patients, 3 with syndrome X), and in 13 trained athletes using magnetic resonance imaging. Ascending aortic compliance was measured angiographically in 22 patients with documented coronary artery disease and in 11 patients with syndrome X. Magnetic resonance velocity mapping was used in six patients with documented coronary artery disease and in three patients with syndrome X to study two-dimensional velocity profiles in the proximal and mid-ascending aorta and to quantify both forward and reverse flow. The measurements were compared with earlier published measurements from 24 normal subjects. It was found that patients with ischemic heart disease or syndrome X had decreased or no measurable aortic compliance and that they had significantly reduced or abnormal ascending aortic reverse flow likely to cause reduced coronary artery flow. A new theory is advanced that decreased myocardial perfusion leading to ischemic heart disease has two sources: (1) insufficient blood flow into the coronary artery inlet due to abnormal aortic function and independent of coronary artery stenosis and (2) local coronary artery stenosis. Observations supporting the theory are presented.

Adult↗
PubMed1989

Pulmonary artery distensibility and blood flow patterns: a magnetic resonance study of normal subjects and of patients with pulmonary arterial hypertension.

Pulmonary artery distensibility was studied with spin-echo magnetic resonance imaging in 20 normal subjects of variable age and in four patients with pulmonary arterial hypertension. The distensibility was found to be significantly lower (8%) in patients with pulmonary arterial hypertension than it was in normal subjects (23%). No age-related difference occurred. Magnetic resonance velocity mapping of the pulmonary artery blood flow was performed in 26 normal subjects--11 had mapping in the mid pulmonary artery, 15 had mapping in the distal pulmonary artery, and mapping in the four patients with pulmonary arterial hypertension was in the mid pulmonary artery. The pulmonary artery flow volume was compared with aortic flow and left ventricular stroke volume and a very good correlation was found. A retrograde flow of 2% occurred in the normal subjects serving to close the pulmonic valve. Antegrade plug flow occurred in most normal subjects but varied among individuals. There were also other variations in the flow pattern among normal individuals. All patients with pulmonary arterial hypertension had a markedly irregular ante- and retrograde flow and a large retrograde flow (average 26%). Magnetic resonance imaging offers a noninvasive way to evaluate pulmonary arterial hypertension as well as to quantitate pulmonary and aortic flows in, for example, left-to-right shunts.

Adult↗
PubMed1989

Quantitation of antegrade and retrograde blood flow in the human aorta by magnetic resonance velocity mapping.

Magnetic resonance velocity mapping was used in 24 normal subjects to study two-dimensional velocity profiles in the proximal and mid-ascending aorta, and to quantify both forward and reverse flow. The aortic flow measurements were validated by comparison with left ventricular stroke volume in all subjects and by comparison with pulmonary flow measurements in 12. Agreement was good with standard errors of the estimate of 7.8 and 7.1 ml, and correlation coefficients of 0.93 and 0.95, respectively. Systolic velocity maps were similar in the proximal aorta and the mid-ascending aorta, with maximum early systolic flow along the left posterior wall. Toward the end of systole and throughout diastole, a channel of reverse flow developed in the same region in the mid-ascending aorta, but in the proximal aorta it split to enter the sinuses of Valsalva, predominantly the left and the right coronary sinuses. Mean percentage ratio of retrograde-to-antegrade flow was 6.3%, with the majority of retrograde flow occurring in early diastole. The findings suggest that the retrograde flow is related to coronary artery flow and it is possible that aortic disease, which is known to influence aortic flow patterns, may also influence coronary flow.

Adolescent↗
PubMed1989

Regional aortic compliance studied by magnetic resonance imaging: the effects of age, training, and coronary artery disease.

Arterial compliance was measured in 70 healthy volunteers, 13 athletes, and 17 patients with coronary artery disease. Magnetic resonance images were acquired at end diastole and end systole through the ascending aorta, the aortic arch, and the descending thoracic aorta. Regional compliance was derived from the change in luminal area in a slice of known thickness and from the pulse pressure. Total arterial compliance was also measured from the left ventricular stroke volume and the pulse pressure. In the volunteers, mean (SD) regional compliance (microliters/mm Hg) was greatest in the ascending aorta (37 (18], lower in the arch (31 (15], and lowest in the descending aorta (18 (8], and it decreased with age. Compliance in the athletes was significantly higher than in their age matched controls (41 (16) versus 22 (11) microliters/mm Hg). In the patients with coronary artery disease it was significantly lower (12 (4) v 18 (10] than in age matched controls. Total arterial compliance also fell with age in those with coronary artery disease although there was more variation. The results suggest a possible role for compliance in the assessment of cardiovascular fitness and the detection of coronary artery disease.

Adult↗
PubMed1988

Magnetic resonance velocity mapping in aortic dissection.

We describe three patients with chronic aortic dissection in whom both spin-echo magnetic resonance imaging (MRI) and cine field-echo imaging were performed. The field even-echo rephasing (FEER) sequence showed the intimal flaps much more clearly than the spin-echo sequence and provided a distinction between thrombus and static blood. Velocity mapping allowed flow measurements in the true and false lumens. The management of the three patients was based upon the information provided by MRI. It is suggested that MRI may avoid invasive investigation and be the method of choice in haemodynamically stable patients with aortic dissection provided that the FEER sequence is used.

Aged↗
PubMed1986

Normal variations of the position of the eye in the orbit.

Photoradiographic measurements of projected corneal and nasion pituitary distances in Swedish adults and in white and black adults in the United States were transformed to true measurements. A new photographic method to compute nose-corneal distance was developed and compared to the photoradiographic and Hertel measurements. A new photographic method was developed to record interpupillary distance more accurately than earlier methods. A highly significant difference in eye position between white and black people was found. Variations in normal eye position in the same individual were studied in 39 subjects. Normal eye position was found to vary in an anterior-posterior direction, with an average variation of 1.5 to 2 mm (range, 0-3.7 mm). The interpupillary distance was found to be very stable. A difference of at least 2 mm, and perhaps 3 to 4 mm in exophthalmometric measurements is necessary to detect a pathological difference.

Anthropometry↗