PubMed Health⌕ Search

Biomedical subjects

J Doornbos

Publications and source records attributed to J Doornbos.

At least 19 recordsLinked to original sources
PubMed1992

The signal intensity of the normal odontoid process (dens) displayed on magnetic resonance images.

In order to analyse the normal signal intensity of the medullary space of the odontoid process (dens) relative to age, the craniovertebral junction of 33 asymptomatic volunteers in six age groups was examined by means of magnetic resonance imaging. To avoid partial-volume effects 3-mm slices were used in sagittal and axial planes. The signal intensities relative to cerebral white matter varied from 0.51 to 1.23 in the sagittal plane and 0.56 to 1.51 in the axial plane. The signal intensities relative to muscle varied from 0.76 to 2.40 in the sagittal plane and 0.96 to 2.30 in the axial plane. The signal intensities relative to fat varied from 0.22 to 0.62 in the sagittal plane and 0.23 to 0.68 in the axial plane. No correlation with age of the volunteers was found. The normal medulla of the dens may exhibit a low signal intensity on T1-weighted images irrespective of age.

Adipose Tissue↗
PubMed1992

Magnetic resonance evaluation of regional left ventricular function. Effect of through-plane motion.

RATIONALE AND OBJECTIVES: Measurements of segmental contraction of the left ventricle by standard magnetic resonance imaging (MRI) and two-dimensional echocardiography involve the comparison of diastolic and systolic time frames acquired from the same imaging plane in space. As the cone-shaped left ventricle shortens along its long axis during systole, the observed contraction may differ from the true myocardial contraction. METHODS: Spin-echo MRI examinations in 21 healthy subjects were performed to evaluate the error caused by failing to compensate for through-plane motion. RESULTS: The authors found that at the base and the mid-ventricle the observed contraction systematically underestimates true contraction by an average of 16% and 21%, respectively (P less than .001). At the apex, the segmental contraction may be overestimated or underestimated. CONCLUSIONS: Because of this error, standard MRI and echocardiography are less suited for basic research on cardiac contraction patterns. However, standard imaging techniques are valuable in clinical studies comparing groups of patients, because all measurements will suffer from the same systematic error.

Adult↗
PubMed1991

Acute myocardial infarction: comparison of T2-weighted and T1-weighted gadolinium-DTPA enhanced MR imaging.

Magnetic resonance images were obtained from 32 patients with acute myocardial infarction, using a four-echo technique (echo time (TE) = 30, 60, 90, and 120 ms) pregadolinium(Gd)-DTPA injection and a TE = 30 ms sequence pre- and post-Gd-DTPA. Intensity ratios of infarcted and normal myocardium were calculated, as were contrast-to-noise and signal-to-noise ratios. The four intensity ratios pre-Gd-DTPA were 1.20 +/- 0.15, 1.42 +/- 0.22, 1.78 +/- 0.38, and 1.99 +/- 0.60 for TE = 30, 60, 90, and 120 ms, respectively, and 1.42 +/- 0.19 post-Gd-DTPA (p = NS for post-Gd-DTPA vs TE = 60, p = 0.007 for TE = 90 vs TE = 120, p less than 0.0001 for all other comparisons). The four contrast-to-noise ratios pre-Gd-DTPA were 1.69 +/- 0.97, 2.69 +/- 1.13, 3.17 +/- 1.15, and 2.90 +/- 1.09 for TE = 30, 60, 90, and 120 ms, respectively, and 2.71 +/- 1.26 post-Gd-DTPA (p = NS for post-Gd-DTPA vs TE = 60, 90, and 120, p = NS for TE = 120 vs TE = 60 and 90, p less than 0.01 for all other comparisons). The four signal-to-noise ratios pre-Gd-DTPA were 8.67 +/- 1.47, 6.52 +/- 0.76, 5.20 +/- 0.64, 4.17 +/- 0.53 for TE = 30, 60, 90, and 120 ms, respectively, and 9.17 +/- 1.92 post-Gd-DTPA (p = 0.03 for post-Gd-DTPA vs TE = 30, p less than 0.0001 for all other comparisons). In conclusion, the detectabilities of acute myocardial infarction were similar at TE = 60 ms and at Gd-DTPA enhanced short-TE MR imaging. However, image quality proved to be superior using the Gd-DTPA enhanced short-TE technique.

Adult↗
PubMed1991

Myocardial infarct sizing and assessment of reperfusion by magnetic resonance imaging: a review.

Early thrombolytic therapy restores patency of thrombotic coronary artery occlusion in many patients. Intravenous streptokinase appears to be effective in achieving recanalization of the occluded infarct-related artery, thereby reducing myocardial infarct size. However, it may be difficult to assess non-invasively the relative value of different reperfusion therapies. MR imaging with or without the use of contrast agents may become a reliable non-invasive technique to assess infarct size after reperfusion therapy. There are indications that early MR imaging after administration of Gd-DTPA is able to differentiate reperfused from non-reperfused infarcts. Furthermore, MR infarct sizing using Gd-DTPA can demonstrate infarct size reduction in patients with successful reperfusion. The availability of ultrafast imaging methods and MR contrast agents may allow assessment of myocardial perfusion in the near future. This article reviews the current status of MR imaging for evaluating ischemic myocardial disease.

Contrast Media↗
PubMed1991

Magnetic resonance imaging of myocardial infarction: correlation with enzymatic, angiographic, and radionuclide findings.

Spin-echo cardiac magnetic resonance imaging studies were performed in 20 patients with a first 7- to 14-day-old (mean 10) myocardial infarction. The magnetic resonance imaging findings were compared with coronary angiography (14 patients), myocardial enzyme release (18 patients), radionuclide angiography (19 patients), and thallium-201 perfusion scintigraphy (19 patients). Regional T2 relaxation times determined from the signal intensities at echo times 30 msec and 90 msec were significantly prolonged in the infarcted areas. Based on abnormal T2 times for every patient, a regional and a total myocardial damage score was determined. The infarct-related artery was correctly identified in 93% of patients by magnetic resonance imaging, in 79% of patients by thallium-201 scintigraphy, and in 62% of patients by radionuclide angiography. The total damage score correlated well with enzymatic infarct size (r = 0.75, p less than 0.001). The correlation between left ventricular end-systolic volume index determined by magnetic resonance imaging and by radionuclide angiography was r = 0.89 (p less than 0.002). The left ventricular end-systolic volume index correlated significantly with enzymatic infarct size (r = 0.72, p less than 0.001), total damage score (r = 0.68, p less than 0.002), and radionuclide left ventricular ejection fraction (r = -0.68, p less than 0.002). Correlations between the magnetic resonance damage score and the thallium-201 perfusion score were r = 0.60 (p less than 0.01) for the exercise images, and r = 0.72 (p less than 0.001) for the redistribution images. This study shows that spin-echo magnetic resonance imaging is quite comparable with the established noninvasive imaging modalities currently used in patients with acute myocardial infarction.

Adult↗
PubMed1991

Gadolinium-DTPA-enhanced magnetic resonance imaging of the isolated rat heart after ischemia and reperfusion.

The objective of this study was to assess the potential of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) to identify myocardial ischemia and reperfusion in the isolated rat heart model. Ischemia was induced by reducing the perfusion pressure from 80 to 30 mm Hg for 2 hours. Hearts were not reperfused, or were reperfused for 20 minutes or for 2 hours. Perfusion was performed with Evans blue dye and/or Gd-DTPA for 3 minutes. Twenty isolated rat hearts were perfused according to the Langendorff method, and divided into five groups according to the perfusion status and the use of Gd-DTPA and/or Evans blue as perfusion markers. The Evans blue distribution in the hearts was assessed by point-counting volumetry. The Gd-DTPA distribution was assessed by magnetic resonance microimaging at 6.3 T field strength. Evans blue staining clearly identified areas with "no flow" or "no reflow." Perfusion with Gd-DTPA enhanced signal intensity significantly, both in ischemic and reperfused myocardium. Signal intensity in hearts reperfused for 2 hours was increased significantly compared to nonreperfused ischemic hearts, but not to ischemic hearts reperfused for 20 minutes. Magnetic resonance imaging with the aid of Gd-DTPA can identify ischemia and reperfusion in the isolated rat heart, dependent on residual perfusion.

Animals↗
PubMed1991

Normal anorectum: dynamic MR imaging anatomy.

In this study, the anatomy of the anorectum in relation to the surrounding structures and the anorectal angle were analyzed with magnetic resonance (MR) imaging at rest, during perineal contraction, and during straining in 10 asymptomatic subjects. The intra- and inter-observer and intra- and interpatient variations in the measurements of the anorectal angle, position of the anorectal junction, and position of the plica of Kohlrausch in the rectum were established at rest, during perineal contraction, and during straining. The values for the anorectal angle and position of the anorectal junction obtained with MR imaging were compared with standard radiography defecography findings. It was shown that MR imaging has the potential for measuring these parameters in a more precise and more patient-friendly way than defecography. Unlike dynamic defecography, MR imaging is able to depict the mobility of the posterior rectal wall. A descent of over 20 mm from rest to straining should be considered pathologic. This finding might play a role in patient selection for operation.

Adult↗
PubMed1991

Acute, subacute, and chronic myocardial infarction: quantitative analysis of gadolinium-enhanced MR images.

The value of gadolinium enhancement to enable detection of infarcted myocardium at T1-weighted magnetic resonance (MR) imaging was assessed in 84 patients after acute myocardial infarction (AMI). Five healthy subjects served as controls. All patients underwent MR imaging before and 20 minutes after administration of gadopentetate dimeglumine. Contrast enhancement of normal myocardium varied 7% +/- 4 after administration of gadopentetate dimeglumine. Mean intensity ratio after gadolinium enhancement in group 1 (imaging less than 1 week after AMI), group 2 (imaging 1-3 weeks after AMI), and group 3 (imaging 3-6 weeks after AMI) was significantly higher than before gadolinium enhancement. In group 4 (imaging more than 6 weeks after AMI), no significant difference was observed. After gadolinium enhancement, the intensity ratio was abnormally increased in 82% of the MR examinations in group 1, in 62% of group 2, in 58% of group 3, and in 12% of group 4. Gadolinium enhancement improved visualization of myocardial infarction at MR imaging up to 6 weeks after onset of symptoms and had a maximal effect within 1 week after AMI.

Adult↗
PubMed1990

Imaging of acute myocardial infarction in pigs with Indium-111 monoclonal antimyosin scintigraphy and MRI.

Indium-111 antimyosin F(ab')2 was used in a series of scintigraphic studies on experimentally induced myocardial infarctions in pigs. Antimyosin distribution recorded by planar images of in vivo pigs and by single photon emission computed tomography (SPECT) of excised hearts delineated areas of myocardial necrosis if infarct volume exceeded 3.3 cm3. Scintigraphic images were compared with magnetic resonance images (MRI) obtained from excised hearts and with photographs of slices of the hearts. Infarct size and localization determined with antimyosin were compared. The MR images, with or without gadolinium-DTPA (Gd-DTPA), of the in vivo pigs were all false-negative; some myocardial wall thinning and high bloodpool signals were visible. Results show that both the antimyosin and the MR technique are specific methods for the visualization of induced myocardial necrosis in this animal model. However, the use of antimyosin is limited to a period ranging from 24 to 72 hours after infarction.

Animals↗
PubMed1990

Variability of myocardial signal on magnetic resonance images.

The diagnosis of myocardial disease by magnetic resonance (MR) imaging depends on accurate measurement of myocardial signal intensity. The authors performed 15 experiments in four rabbits at 1.9 T with spin-echo MR imaging to study the variability of myocardial signal intensity throughout the cardiac cycle and to measure myocardial T2 values. Variability in signal from the myocardium throughout the cardiac cycle was observed in all experiments. During systole, a significant increase in myocardial signal was noted, when data acquisition was performed with electrocardiogram (ECG)-gating and controlled ventilation (P = .02). An inverse relationship between myocardial signal and phase noise was found, indicating the motion-related nature of the variation of myocardial signal. A similar inverse relationship was observed in images obtained from a normal human volunteer. Ex vivo myocardial T2 values of rabbit myocardial tissue were significantly higher than the in vivo values (P = .003), reflecting residual motion despite cardiac gating and controlled ventilation.

Animals↗
PubMed1990

Diagnostic significance of gadolinium-DTPA (diethylenetriamine penta-acetic acid) enhanced magnetic resonance imaging in thrombolytic treatment for acute myocardial infarction: its potential in assessing reperfusion.

The diagnostic value of gadolinium-DTPA (diethylenetriamine penta-acetic acid) enhanced magnetic resonance imaging in patients treated by thrombolysis for acute myocardial infarction was assessed in 27 consecutive patients who had a first acute myocardial infarction (14 anterior, 13 inferior) and who underwent thrombolytic treatment and coronary arteriography within 4 hours of the onset of symptoms. Magnetic resonance imaging was performed 93 hours (range 15-241) after the onset of symptoms. A Philips Gyroscan (0.5 T) was used, and spin echo measurements (echo time 30 ms) were made before and 20 minutes after intravenous injection of 0.1 mmol/kg gadolinium-DTPA. In all patients contrast enhancement of the infarcted areas was seen after Gd-DTPA. The signal intensities of the infarcted and normal values were used to calculate the intensity ratios. Mean (SD) intensity ratios after Gd-DTPA were significantly increased (1.15 (0.17) v 1.52 (0.29). Intensity ratios were higher in the 17 patients who underwent magnetic resonance imaging more than 72 hours after the onset of symptoms than in the 10 who underwent magnetic resonance imaging earlier, the difference being significantly greater after administration of Gd-DTPA (1.38 (0.12) v 1.61 (0.34). When patients were classified according to the site and size of the infarcted areas, or to reperfusion (n = 19) versus non-reperfusion (n = 8), the intensity ratios both before and after Gd-DTPA did not show significant differences. Magnetic resonance imaging with Gd-DTPA improved the identification of acutely infarcted areas, but with current techniques did not identify patients in whom thrombolytic treatment was successful.

Adult↗
PubMed1990

Myocardial infarct size after reperfusion therapy: assessment with Gd-DTPA-enhanced MR imaging.

In 21 patients with proved acute myocardial infarction, the size of the infarct was estimated with serial magnetic resonance (MR) imaging after intravenous injection of gadolinium diethylenetriaminepentaacetic acid (DTPA) (0.2 mmol per kilogram of body weight). Early reperfusion after thrombolytic therapy or percutaneous transluminal coronary angioplasty performed during the acute phase of infarction was documented with coronary angiography in nine patients (group 1). In 12 patients (group 2), no reperfusion was achieved (n = 5) or no thrombolytic therapy was given (n = 7). All group 2 patients were considered to have no reperfusion. Infarct sizes measured with MR imaging were significantly smaller in group 1 than in group 2 at 8 days +/- 4 after infarct onset (8% +/- 5% vs 15% +/- 4%, respectively; P less than .001). Serial MR images showed individual variations in infarct size, findings that may be clinically significant. Estimation of infarct size with Gd-DTPA-enhanced MR imaging is accurate in demonstrating the effect of successful reperfusion therapy on infarct size.

Adult↗
PubMed1989

Improved detection of acute myocardial infarction by magnetic resonance imaging using gadolinium-DTPA.

To assess the value of the paramagnetic contrast agent Gadolinium (Gd)-DTPA in Magnetic Resonance Imaging (MRI) of acute myocardial infarction (AMI), we studied 20 patients with a first AMI by ECG-gated MRI before and after intravenous administration of 0.15 mmol/kg Gd-DTPA. The MRI studies were performed after a mean of 98 hours (range 15-241) after the acute onset of AMI. Spin-echo measurements (TE 30 msec) were made using a Philips Gyroscan (0.5 Tesla). After performing the baseline MRI scans, the MRI procedure was repeated every 10 minutes for up to 40 minutes following injection of Gd-DTPA. In 18 (90%) patients contrast enhancement in the infarcted myocardial areas was observed after Gd-DTPA. In these patients intensity versus region curves, derived from 9 to 11 adjacent myocardial regions of interest, showed increased signal intensities in the infarcted areas after administration of Gd-DTPA. The precontrast signal intensity ratio between infarcted and normal myocardium was 1.14 +/- 0.15 (mean +/- SD); the postcontrast ratios at 10 minutes were 1.41 +/- 0.21 (P less than 0.05), at 20 minutes 1.61 +/- 0.19 (P less than 0.01), at 30 minutes 1.43 +/- 0.20 (P less than 0.05), and at 40 minutes 1.33 +/- 0.20 (P = NS). It is concluded that MRI using the contrast agent Gd-DTPA significantly improves the visualization and detection of infarcted myocardial areas in patients with AMI and that optimal contrast enhancement is obtained 20 minutes after administration of Gd-DTPA.

Adult↗
PubMed1989

Reperfused and nonreperfused myocardial infarction: diagnostic potential of Gd-DTPA--enhanced MR imaging.

Forty-five patients with suspected acute myocardial infarction were examined with magnetic resonance (MR) imaging before and serially up to 30 minutes after intravenous injection of gadolinium diethylenetriaminepentaacetic acid (DTPA), 0.1 mmol/kg of body weight. Coronary angiography after thrombolytic therapy was performed in all patients to assess reperfusion. Intensity ratios between both reperfused and nonreperfused infarcted areas and normal myocardium increased significantly up to 15-20 minutes after administration of Gd-DTPA and were still elevated 30 minutes after injection (P less than .0001). In accordance with the findings in experimental studies, four distribution patterns of infarct enhancement were observed. The overlap in enhancement patterns and similar maximal intensity ratios after Gd-DTPA administration for both reperfused and nonreperfused infarcts preclude a reliable differentiation on the basis of these factors alone. Significant enhancement of both reperfused and nonreperfused infarcts allows adequate infarct imaging up to at least 30 minutes after administration of Gd-DTPA.

Adult↗
PubMed1988

MR imaging of acute myocardial infarction: value of Gd-DTPA.

The potential of gadolinium (Gd)-DTPA to improve the detection of acute myocardial infarction by MR has been shown in experimental canine studies. To determine its value in humans, we studied five patients 2-17 days after myocardial infarction by using ECG-gated MR before and after administration of 0.1 mmol/kg Gd-DTPA. One patient had a rupture of the interventricular septum, complicating an acute inferior-wall infarction. Spin-echo images were obtained before and immediately after injection of Gd-DTPA and were repeated every 10 min for up to 40 min. In four patients, intensity-vs-time curves revealed increasing signal intensity in the infarcted area in the first 20 min after injection of gadolinium. Contrast between normal and infarcted myocardium was greatest 20-30 min after Gd-DTPA injection. In one patient, increasing signal intensity of the infarcted myocardium was observed up to 40 min after Gd-DTPA injection. The precontrast intensity ratio between infarcted and normal myocardium was 1.1 at echo time (TE) = 30 msec and was 1.4 at TE = 60 msec (p less than .05). The postcontrast intensity ratio was 1.6, which was not statistically different from the ratio at TE = 60 msec but which was significantly higher than the ratio at TE = 30 msec (p less than .01). Infarct definition was substantially improved on postcontrast images. The septal rupture was clearly seen, and the infarcted myocardium surrounding the septal rupture showed enhancement on postcontrast images. These results suggest that Gd-DTPA can improve MR visualization and detection of acute myocardial infarction.

Adult↗