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M Oudkerk

Publications and source records attributed to M Oudkerk.

At least 91 records · Page 5Linked to original sources
PubMed1999

Magnetic resonance imaging of the coronary arteries: clinical results from three dimensional evaluation of a respiratory gated technique.

BACKGROUND: Magnetic resonance coronary angiography is challenging because of the motion of the vessels during cardiac contraction and respiration. Additional challenges are the small calibre of the arteries and their complex three dimensional course. Respiratory gating, turboflash acquisition, and volume rendering techniques may meet the necessary requirements for appropriate visualisation. OBJECTIVE: To determine the diagnostic accuracy of respiratory gated magnetic resonance imaging (MRI) for the detection of significant coronary artery stenoses evaluated with three dimensional postprocessing software. METHODS: 32 patients referred for elective coronary angiography were studied with a retrospective respiratory gated three dimensional gradient echo MRI technique. Resolution was 1.9 x 1.25 x 2 mm. After manual segmentation three dimensional evaluation was performed with a volume rendering technique. RESULTS: Overall 74% (range 50% to 90%) of the proximal and mid coronary artery segments were visualised with an image quality suitable for further analysis. Sensitivity and specificity for the detection of significant stenoses were 50% and 91%, respectively. CONCLUSIONS: Volume rendering of respiratory gated MRI techniques allows adequate visualisation of the coronary arteries in patients with a regular breathing pattern. Significant lesions in the major coronary artery branches can be identified with a moderate sensitivity and a high specificity.

Adult↗
PubMed1999

In vivo assessment of three dimensional coronary anatomy using electron beam computed tomography after intravenous contrast administration.

Intravenous coronary angiography with electron beam computed tomography (EBCT) allows for the non-invasive visualisation of coronary arteries. With dedicated computer hardware and software, three dimensional renderings of the coronary arteries can be constructed, starting from the individual transaxial tomograms. This article describes image acquisition, postprocessing techniques, and the results of clinical studies. EBCT coronary angiography is a promising coronary artery imaging technique. Currently it is a reasonably robust technique for the visualisation and assessment of the left main and left anterior descending coronary artery. The right and circumflex coronary arteries can be visualised less consistently. Improvements in image acquisition and postprocessing techniques are expected to improve visualisation and diagnostic accuracy of the technique.

Contrast Media↗
PubMed1999

Breath-hold MR cholangiopancreatography with three-dimensional, segmented, echo-planar imaging and volume rendering.

End-expiration, 21-second breath-hold, three-dimensional magnetic resonance (MR) cholangiopancreatography (MRCP) was developed with segmented echo-planar imaging. In 15 healthy subjects and 14 randomly selected patients undergoing liver studies, three-dimensional MRCP images were obtained and volume rendered. In 15 (100%) healthy subjects and 13 (93%) patients, clear depiction of biliary, hepatic, and pancreatic ducts (with lumen diameter of at least 2 mm) was possible with good signal-to-noise ratio.

Adult↗
PubMed1999

Magnetic resonance imaging of the coronary arteries: anatomy of the coronary arteries and veins in three-dimensional imaging.

Magnetic resonance imaging of coronary arteries will visualize, besides the arteries, the myocardium, blood in the cavities and cardiac veins. This will hamper the application of projectional visualization techniques such as those used in conventional coronary angiography. Volume rendering, a different visualization technique, can be used to create a three-dimensional impression of a magnetic resonance data set on a two-dimensional surface. In this article, we will review the volume-rendering technique and anatomy of the coronary arteries and veins in the obtained images. Also we will discuss the relation between arteries and veins and the possible sites of confusion.

Animals↗
PubMed1998

Intravenous coronary angiography by electron beam computed tomography: a clinical evaluation.

BACKGROUND: -Noninvasive detection of coronary stenoses with electron beam CT (EBCT) after intravenous injection of contrast medium has recently emerged. We sought to determine the diagnostic accuracy of EBCT angiography in the clinical setting using conventional coronary angiography as the "gold standard." METHODS AND RESULTS: Thirty-seven patients (30 men) were investigated. After intravenous injection of 150 mL of contrast medium, 40 to 60 consecutive transaxial tomograms, covering the proximal and middle parts of the coronary arteries, were obtained with ECG triggering at end diastole during breath-holding. Three-dimensional reconstructions of the proximal and middle parts of the arteries were compared with the conventional angiograms. Of the 259 proximal and middle coronary segments, 211 (81%) were analyzable by EBCT. Of the left anterior descending coronary artery (LAD) segments, 95% were assessable. Right coronary artery (RCA) and left circumflex artery (LCx) segments were assessable in 66% and 76%, respectively. Overall sensitivity and specificity to detect a >50% diameter stenosis were 77% and 94%, respectively. This was 82% and 92% for the LAD, 60% and 97% for the RCA, and 83% and 89% for the LCx (all figures based on assessable lesions). CONCLUSIONS: Intravenous EBCT coronary angiography is a promising coronary imaging technique. The technique is not yet robust enough to be an alternative to conventional coronary angiography. It can detect and rule out significant coronary artery disease of the left main proximal and mid portions of the LAD with good accuracy.

Adult↗
PubMed1998

[Electron-beam computed tomography: preliminary experiences in the Netherlands].

The difference between computer tomography (CT) and electron beam tomography (EBT) is that for CT the x-ray tube rotates in a ring round the patient, and for EBT the x-ray beam rotates itself. As a result, with EBT the speed of making images is not limited by the mechanical rotation of the tube, and 16 images can be made per second. An EBT scan of a whole thorax takes 9 seconds. Specific application areas are fast moving organs and patients who cannot remain in one position for long, e.g. children and intensive care patients. Research is being conducted into the possibilities of this non-invasive technique for the demonstration of coronary artery lesions, pulmonary embolism, pulmonary metastases and dynamic examination of the major respiratory tract. Costs of an EBT scan currently amount to Dfl. 450.--but they will probably decrease as this imaging system is developed further. The exposure to radiation is about the same as that caused by a (spiral) CT.

Diagnostic Imaging↗
PubMed1998

Coronary arteries.

Conventional coronary angiography (CA) is the standard of excellence for the evaluation of coronary artery disease. However, non-invasive imaging modalities have developed that can play an important clinical role in the diagnosis. Magnetic resonance imaging (MRI) can offer a comprehensive evaluation of the heart and the coronary arteries by virtue of its high soft tissue contrast capabilities, double-oblique tomographic sections and the possibility of quantifying physiological parameters without need of ionizing radiation. Magnetic resonance coronary arteriography (MRCA) using breath-hold and free-breathing techniques has been investigated but is still in the experimental phase; its precise role for the assessment of coronary stenosis must still be identified. Nonetheless, MRCA has proven clinically relevant in determining the course of anomalous coronary arteries and the patency of coronary artery bypass grafts. Novel intravascular contrast agents promise faster coverage of the cardiac anatomy and may provide a long-awaited boost for MRCA. Contrast-enhanced electron-beam computed tomography (EBT), another competing imaging modality, is now being subjected to widespread evaluation following initially encouraging results.

Coronary Angiography↗
PubMed1998

Understanding the discrepancies between 31P MR spectroscopy assessed liver metabolite concentrations from different institutions.

The high divergence between the liver metabolite concentrations and pH values reported in previous quantitative 31P magnetic resonance studies, for instance phosphomonoester (0.7-3.8 mM) and phosphodiester (3.5-9.7 mM), has not been addressed in the literature. To assess what level of discrepancy can be caused by processing and metabolite integration, in this study chemical shift imaging localized 31P magnetic resonance spectra of human liver were quantitated by three methods currently applied in clinical practice: peak areas defined manually by placement of two cursors vs. frequency domain curve fitting with the assumption of either Gaussian or Lorentzian line shapes. Large reproducible differences were found in liver metabolite peak areas but not in pH, indicating that processing and peak integration methods can only explain part of the discrepancies between the results from different institutions.

Adenosine Triphosphate↗
PubMed1998

1H MR spectroscopy monitoring of changes in choline peak area and line shape after Gd-contrast administration.

Fifteen percent loss in the peak area of choline containing compounds (Cho) was recently observed in 1H MR spectra of contrast-enhancing tumor at 5-10 min after Gd-contrast administration [Magn. Reson. Med. 37:222-225, 1997]. In this study, chemical shift imaging (CSI, 1500/135 ms PRESS) was used to assess the spectral changes in 47 Gd-enhancing glial brain tumors and metastatic brain tumors measured at 0-5, 5-10, and/or 10-15 min after administration of Gd-contrast. Percent Cho peak area losses measured at these times, 3 +/- 3, 12 +/- 2, and 14 +/- 3 SEM, respectively, coincided with trends of line narrowing and up-field shift of the Cho peak. Significant changes in creatine and N-acetyl acetate signals were not observed. It is concluded that the Gd-induced loss of tumor Cho signal measured after 5 min, typically required for post contrast-MRI and the positioning of the CSI volume on tumor, shows little further change with time, if any.

Adult↗
PubMed1998

A comparison of adult pulmonary autograft diameter measurements with echocardiography and magnetic resonance imaging.

UNLABELLED: In 38 consecutive patients the pulmonary autograft was used in aortic root replacement. Investigations were performed with transthoracic echocardiography, transoesophageal echocardiography and magnetic resonance imaging in 31, 27 and 27 patients respectively. The mean age at operation was 28.7 years (range 19.0-52.0) and the follow-up period was 2.8 years (range 0.8-6.7). The pulmonary autograft diameter was measured at the subannular region (1), at the annulus at the hinge points of the valve leaflets (2), at the sinus (3), at the sino-tubular junction (4) and at the distal part of the autograft (5). With transoesophageal echocardiography the mean systolic measurements at levels 1 to 5 were 32, 31, 42, 35 and 34 mm, respectively. The corresponding diastolic measurements were smaller: 25, 28, 42, 35 and 34 mm respectively. There was no significant difference between transthoracic echocardiography and transoesophageal echocardiography measurements of the proximal autograft (levels 1-3). Diameters obtained with magnetic resonance imaging were 1 to 3 mm larger than those obtained with transthoracic echocardiography and transoesophageal echocardiography (P < 0.05), except the annulus at systole (P > 0.3). CONCLUSIONS: The mean pulmonary autograft diameters measured using transthoracic echocardiography, transoesophageal echocardiography and magnetic resonance imaging were larger than native aortic and pulmonary diameters of a normal population in the same age group. Diameters of the distal 2 levels could not be imaged reliably with transthoracic echocardiography. Magnetic resonance imaging diameter measurements were, in general, larger than with echocardiography.

Adult↗
PubMed1998

Breath-hold coronary MR angiography with volume-targeted imaging.

PURPOSE: To illustrate a new concept for fast coronary artery screening with breath-hold volume targeted magnetic resonance (MR) imaging. MATERIALS AND METHODS: Ten volunteers and 25 patients were imaged at a field strength of 1.5 T with an MR system with phased-array-coil reception and capable of echo-planar imaging. End-expiration breath-hold volume localization of the entire heart was performed with three-dimensional (3D) multishot segmented echo-planar imaging in 16-22 heartbeats. Interaction with a multiplaner reformation platform provided the optimal double-oblique volumes necessary to target seven coronary artery segments. Each segment was evaluated with 24-mm-thick volumes and breath holds at end expiration and magnetization transfer-enhanced 3D turbo fast low-angle shot imaging in 21 heartbeats. An intravascular contrast agent was used in eight patients to improve blood-myocardium contrast for the heart volume localizer acquisitions. RESULTS: The entire coronary tree was consistently covered in fewer than 13 breath holds. The scheme was successful in all volunteers and in 22 patients who could achieve adequate breath hold. With end-expiration acquisitions, the prescribed 24-mm-thick volumes were reproducible for all coronary segments in all cooperative subjects. CONCLUSION: Despite its status as the indisputable standard of reference for the detection of coronary artery disease, conventional coronary angiography remains costly and highly invasive, with associated risks of major complications, including stroke and death. Breath-hold volume targeted acquisitions permit rapid localization and coverage of the entire coronary tree with adequate resolution for evaluating the coronary arteries.

Adult↗
PubMed1997

[Reserve concerning pulmonary angiography in pulmonary embolism is not justified].

OBJECTIVE: Evaluation of the safety of pulmonary angiography in patients with clinically suspected pulmonary embolism. DESIGN: Retrospective cohort study. SETTING: Academic Hospital, Rotterdam, the Netherlands. METHOD: The data on complications of pulmonary angiography were collected from four Dutch hospitals over a period of about five years (Academic Medical Centre and Slotervaart Hospital, Amsterdam; St. Elisabeth Hospital, Tilburg and Dr. Daniel den Hoed Cancer Centre/University Hospital Rotterdam). RESULTS: Pulmonary angiography was performed in 697 patients. No fatal complications were noted (mortality: 0%; 95% confidence interval (95% CI); 0.00-0.53). Complications were seen in 3 patients; dissection of the pulmonary artery in I patient and contrast extravasation in 2 patients (morbidity: 0.4%; 95% CI: 0.09-1.25). CONCLUSION: In patients with clinically suspected pulmonary embolism, pulmonary angiography is a safe diagnostic modality. It is recommended that, in patients in whom the diagnosis of pulmonary embolism cannot be confirmed or excluded by noninvasive diagnostic methods, pulmonary angiography should be performed (according to the Dutch consensus "Diagnostic pulmonary embolism').

Adolescent↗
PubMed1997

1H chemical shift imaging reveals loss of brain tumor choline signal after administration of Gd-contrast.

1H MR spectra obtained by chemical shift imaging (CSI) of contrast-enhancing brain tumors before and after the administration of Gd-contrast agent were quantitated and compared with the results in normal brain tissue included in the volume of interest. Twenty-seven combined magnetic resonance imaging and spectroscopy (MRI, MRS) examinations of brain tumor lesions included T1-weighted MRI and CSI (TR/TE 1500/135 ms double-spin echo) repeated 5-10 min after the administration of Gd-contrast agent (0.1-0.2 mM). In 1H MR spectra of contrast-enhancing tumor Gd-contrast induced a mean loss of 15% of the peak area of choline-containing compounds (Cho, P < 0.001) that was correlated with precontrast Cho linewidth (r = -0.72, P < 0.00001). This phenomenon limits the diagnostic use of brain tumor MRS examinations performed immediately after contrast-enhanced MRI.

Aspartic Acid↗
PubMed1997

Prediction of pathological subtrochanteric fractures due to metastatic lesions.

We report a radiographic review of 54 consecutive patients with 24 impending and 30 actual pathological fractures due to metastatic bone lesions in the subtrochanteric femoral region. In an attempt to develop criteria for metastatic lesions at risk of fracturing, the following variables based on anteroposterior and lateral X-rays were considered: appearance of the lesion, width of the lesion, ratio between width of the lesion and bone width, length of the lesion, length of cortex involvement, proportion of transverse cortical bone destroyed and local pain. Nearly all (99%) of the lesions were radiographically classified as lytic. In 27 cases (50%) they were radiographically unmeasurable. Maximal longitudinal cortical destruction showed a difference between patients with an actual or impending fracture. Prophylactic internal fixation of pathological subtrochanteric fractures due to metastatic lesions has to be considered in cases of increasing pain. If the conventional X-ray can not be evaluated, a computed tomography (CT) scan has to be considered.

Adult↗
PubMed1997

Gd-enhanced MR imaging of brain metastases: contrast as a function of dose and lesion size.

MR imaging contrast of brain metastases after cumulative doses of gadolinium chelate is quantitated and compared in order to assess the clinical utility of high dosage. T1-weighted spin-echo MR images of 39 patients with metastatic brain tumors were made before and after each of three equal doses cumulating to 0.1, 0.2 and 0.3 mmol Gd-complex per kg body weight. Quantitation of MRI contrast was limited to homogeneous brain metastases larger than 3 mm (n = 246). Post-Gd MRI contrast doubled with dose escalation from 0.1 to 0.3 mmol/kg and also increased with lesion size, by a factor of 2.5 between metastases of 3 and 16 mm diameter, that is after correcting for partial volume effect. At 0.2 and 0.3 mmol/kg the respective numbers of visible metastases increased by 15% and 43% compared with 0.1 mmol/kg (p < 0.0001, both). Image contrast figures differed significantly between doses (p = 0.018). Both the number of metastases and the image contrast is significantly higher when dose escalation is performed. It is indicated that the number of detected metastases will increase further at Gd doses beyond 0.3 mmol/kg. Post-Gd MRI contrast increases with lesion size, to an extent that can not be attributed to partial volume attenuation.

Analysis of Variance↗
PubMed1997

MRI in patients with axillary metastases of occult breast carcinoma.

In 4 women with adenocarcinoma metastasis in an axillary lymph node and no primary tumor found, we investigated whether Magnetic Resonance Imaging (MRI) of the breast could detect a clinically and mammographically occult breast tumor. MRI detected an enhancing lesion in 3 women and an enhancing double lesion in one patient. MRI directed ultrasound guided fine needle aspiration cytology confirmed the 5 breast carcinomas in the 4 women. In women with metastasis in an axillary lymph node consistent with breast cancer and without a primary tumor, MRI of the breast should added to clinical examination and mammography before defining it as an occult primary and planning therapy.

Adenocarcinoma↗
PubMed1997

Phosphorus-31 chemical shift imaging of metastatic tumors located in the spine region.

RATIONALE AND OBJECTIVES: Phosphorus-31 magnetic resonance spectroscopy was used in 14 cases to examine metastases of known malignant tumors located in the spine region. The purpose was to test the hypothesis that tumor phosphomonoester (PME) is elevated. METHODS: Two-dimensional chemical shift imaging was used in combination with a slice-select gradient in the third dimension to obtain true three-dimensional localization. RESULTS: The spectral maps revealed PME signals increased up to 10 times in voxels containing contrast-enhancing metastatic spine lesions compared with adjacent areas and peripheral muscle voxels. Phosphomonoester increase was significant for all tumors combined (8.6 +/- 5.3 arbitrary units versus 2.4 +/- 0.5 and 2.2 +/- 0.8 arbitrary units in unaffected myelum and corpora; P < 0.001), though smaller than 2 standard deviations in 5 of 14 cases. The latter shared high proportions of phosphocreatine, phosphocreatine > 30% of total phosphate, indicating substantial amounts of muscle tissue included in the tumor voxels (partial volume effect). CONCLUSIONS: Phosphorus-31 MR spectroscopy can be of value in the recognition of malignant vertebral column abnormalities. Malignant tumor is marked by drastic PME increases-fourfold to tenfold, provided that partial volume effects are small.

Female↗