Biomedical subjects

J Doornbos

Publications and source records attributed to J Doornbos.

80 records · Page 5Linked to original sources

PubMedDate not supplied

Gadolinium-enhanced magnetic resonance imaging in acute myocardial infarction.

To evaluate the usefulness of the paramagnetic contrast agent Gadolinium-DTPA (diethylenetriaminepentaacetic acid) in Magnetic Resonance Imaging of acute myocardial infarction, we studied a total of 45 patients with a first acute myocardial infarction by ECG-gated magnetic resonance imaging before and after intravenous administration of 0.1 mmol/kg Gadolinium-DTPA. All patients received thrombolytic treatment by intravenous streptokinase. The magnetic resonance imaging studies were performed after a mean of 88 h (range 15-241) after the acute onset of acute myocardial infarction. Five patients without evidence of cardiac disease served as controls. Spin-echo measurements (TE 30 ms) were made using a Philips Gyroscan (0.5 Tesla) or a Teslacon II (0.6 Tesla). The 45 patients were divided into four groups of patients. In Group I (5 patients) Gadolinium-DTPA improved the detection of myocardial infarction by Gadolinium-DTPA. In Group II (20 patients) the magnetic resonance imaging procedure was repeated every 10 min for up to 40 min following administration of Gadolinium-DTPA. Optimal contrast enhancement was obtained 20-25 min after Gadolinium-DTPA. In Group III (27 patients) signal intensities were significantly higher in the patients who underwent the magnetic resonance imaging study more than 72 h (mean 120) after the acute event, suggesting increased accumulation of Gadolinium-DTPA in a more advanced stage of the infarction process. In Group IV (45 patients) Gadolinium-DTPA was administered in an attempt to distinguish between reperfused and nonreperfused myocardial areas after thrombolytic treatment for acute myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMedDate not supplied

Follow-up of regional myocardial T2 relaxation times in patients with myocardial infarction evaluated with magnetic resonance imaging.

Multi-echo spin-echo cardiac magnetic resonance imaging studies (echo times 30, 60, 90 and 120 ms) were performed in 19 patients with a 7-14-day (mean 10) old myocardial infarction and were repeated in 13 patients 4-7 months (mean 6) later. Also, 10 normal subjects were studied with magnetic resonance imaging. T2 relaxation times of certain left ventricular segments were calculated from the signal intensities at echo times of 30 and 90 ms. Compared to normal individuals, the mean T2 values on the early magnetic resonance images of the patients with inferior infarction showed significantly prolonged T2 times in the inferiorly localized segments, while on the follow-up magnetic resonance images the T2 times had almost returned to the normal range. Also the patients with anterior infarction showed significantly prolonged T2 times in the anteriorly localized segments on the early nuclear magnetic resonance images, but the T2 times remained prolonged at the follow-up magnetic resonance images. For every patient a myocardial damage score was determined, which was defined as the sum of the segmental T2 values in the patients minus the upper limit of normal T2 values obtained from the normal volunteers (= mean normal + 2SD). The damage score on both the early and late magnetic resonance imaging study correlated well with infarct size determined by myocardial enzyme release. Only the patients with an inferior infarction showed a significant decrease in damage score at follow-up magnetic resonance imaging. It is concluded that the regional T2 relaxation times are increased in infarcted myocardial regions and may remain prolonged for at least up to 7 months after the acute event, particularly in patients with an anterior infarction. These findings demonstrate the clinical potential of T2-weighted magnetic resonance imaging studies for detecting myocardial infarction, and estimating infarct size for an extended period after acute myocardial infarction.

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PubMedDate not supplied

Cardiovascular applications of magnetic resonance imaging and phosphorus-31 spectroscopy.

Recent advances in cardiovascular applications of magnetic resonance (MR) imaging and phosphorus-31 spectroscopy are reported. MR velocity mapping is a valuable adjunct to conventional imaging techniques, providing information on flow velocities as well as on absolute blood flow volume in the aorta and pulmonary arteries. Recently, ultrafast MR techniques have become available to evaluate myocardial perfusion with the aid of MR contrast agents as perfusion marker. Dynamic MR imaging is a powerful tool to assess cardiac function and ventricular mass. In particular, right ventricular function and mass can be evaluated with great accuracy, contributing to improved assessment of the significance of disease processes which may affect the right heart. The role of phosphorus-31 spectroscopy of the heart is expanding for the evaluation of ischemic myocardial disease and cardiomyopathies. The phosphocreatine to adenosine triphosphate ratio appears to be a marker of disease in patients with cardiac hypertrophy. In conclusion, MR imaging and phosphorus-31 spectroscopy is gaining widespread acceptance for evaluation of many cardiovascular disease processes.

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PubMedDate not supplied

MR imaging of the normal larynx.

Magnetic resonance imaging of the larynx was performed on 15 volunteers. Searching for optimal images in the sagittal, frontal, and transverse planes, we compared images made with a special surface coil and the standard head coil, images with different slice thicknesses, images with different repetition times (TR) and images with different matrices. The field of view and the scan times were kept as small as possible. Using a surface coil, we obtained high resolution images in all three planes. These images provide clinically relevant information, not shown by current radiological techniques: hyoepiglottic ligament, thyrohyoid ligament, thyroepiglottic ligament and cricothyroid ligament, the borders between the preepiglottic space and both paraglottic spaces (PGS), the borders between both PGS and thyroid cartilage, and the vocalis and thyroarytenoid muscles. Short TR is preferred because, with shorter scan time, more measurements could be made. Images with a 128 X 128 matrix size had a much better signal-to-noise ratio than images with a 256 X 256 matrix size. Magnetic resonance has great potential in imaging normal and pathological anatomy of the larynx.

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PubMedDate not supplied

MR imaging in assessment of cardiac transplant rejection in humans.

To evaluate the efficacy of myocardial T2 values in the assessment of allograft rejection, we performed magnetic resonance (MR) imaging at 0.5 T serially in seven cardiac transplant recipients and singly in seven normal volunteers. Cardiac-gated multi-echo spin echo images were obtained; T2 values were estimated by a two-point method from regions of interest in the myocardium. Patients underwent MR and cardiac biopsy at various times after transplantation. Forty-two patient exams were performed. All biopsies showed either no rejection or early stages of rejection: grade 0 in 8 examinations, grade 1 in 28, and grade 2 in 6. Myocardial T2 values in patients in early stages of cardiac rejection were slightly higher (but not statistically significant) than those in non-rejecting patients and normal volunteers. Although this study did not allow prospective detection of cardiac rejection in our patient group, it demonstrated a trend toward higher T2 values at higher biopsy grades that may indicate an ability to assess more severe stages of transplant rejection.

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PubMedDate not supplied

Cardiac first-pass and myocardial perfusion in normal subjects assessed by sub-second Gd-DTPA enhanced MR imaging.

To evaluate first pass in the right ventricular (RV) and left ventricular (LV) cavities and myocardial perfusion, subsecond MR imaging was performed in seven normal subjects following intravenous bolus injection of Gd-DTPA. After the baseline scans, sequential ECG-triggered images were obtained every three to four RR intervals. The procedure consisted of an initial presaturation pulse (150 degrees), and the acquisition time for one image was approximately 500 ms with 64 phase-encoding steps. After bolus administration of Gd-DTPA (0.05 mmol/kg body wt), progressively increasing signal intensities were observed in the RV cavity, the LV cavity, and the myocardial wall. Gadolinium DTPA enhanced subsecond MR offers temporal information of the first transit in the cardiac chambers and may provide useful clinical reference data for assessment of myocardial perfusion in patients with coronary artery disease.

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PubMedDate not supplied

Echo planar MRI of the heart on a standard system: validation of measurements of left ventricular function and mass.

OBJECTIVE: Our goal was to validate cardiac measurements derived from multishot echo planar MRI (EPI) as compared with the well validated conventional GRE technique. METHOD: Ten healthy subjects underwent breath-hold EPI and non-breath-hold GRE imaging in the short axis orientation of the left ventricle (LV) on a standard 1.5 T MR system. Ten section levels were obtained to encompass the entire LV. Measurements were obtained of end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), ejection fraction (EF), LV mass, time to end-systole (TES), and peak filling rate (PFR). Analysis of variance was performed to determine agreement between GRE- and EPI-derived measurements. RESULTS: The acquisition time for EPI was much shorter than that for GRE (2.5 vs. 15 min). Both imaging techniques yielded good quality images allowing LV volumetrics. Agreement between GRE and EPI was best for measurements of EDV, SV, and LV mass; somewhat less agreement was found for ESV, EF, TES, and PFR. The intraobserver variability for measuring TES and PFR was higher for GRE than EPI (one sided F test; critical values at p = 0.05 were > 3.18). CONCLUSION: Multishot EPI of the heart provides accurate measurements of LV function and mass in a time-efficient manner.

Adult↗

PubMedDate not supplied

Measurement of aortic and pulmonary flow with MRI at rest and during physical exercise.

PURPOSE: Our aim was to assess the feasibility of measuring great vessel flow during submaximal exercise using MR flow mapping. METHOD: In 16 healthy volunteers, MR measurements of great vessel flow were obtained at rest and during two levels of submaximal physical exercise using an MR-compatible bicycle ergometer. RESULTS: Great vessel flow showed good correlation at rest and during exercise (r = 0.9, p < 0.0005). Significant increase in heart rate was observed during exercise. Aortic flow volume increased from 64 +/- 13 ml/beat at rest to 71 +/- 11 ml/beat at 50 W (p < 0.0005) to 79 +/- 13 ml/beat at 100 W (p < 0.0005). Pulmonary flow volume increased from 63 +/- 14 ml/beat at rest to 70 +/- 13 ml/beat at 50 W (p < 0.005) to 76 +/- 12 ml/beat at 100 W (p = NS). CONCLUSION: Quantification of great vessel flow can be performed safely in healthy volunteers using MR flow measurements during submaximal physical exercise. These measurements may be used to study hemodynamic abnormalities in patients with cardiac disease.

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