Biomedical subjects

J F Debatin

Publications and source records attributed to J F Debatin.

At least 19 recordsLinked to original sources

PubMed1997

Preliminary assessment of three-dimensional magnetic resonance imaging for various colonic disorders.

BACKGROUND: Improvements in magnetic resonance imaging (MRI) technology have enabled the acquisition of three-dimensional MRI datasets in a single breath hold. We adopted this technique to make a three dimensional intraluminal and extraluminal assessment of the colon in three patients with various colonic disorders. METHODS: One patient was studied after having a double-contrast barium enema. Two patients had MRI scans after colonoscopy, which showed three colonic tumours in one and multiple polyps in the ascending colon of the other. The process of rectal filling with 1.5-2.0 L water mixed with 15-20 mL 0.5 mol/L gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) was monitored with MR fluoroscopic sequence. Three-dimensional datasets of the contrast-filled colon were taken with patients in prone (before and after intravenous administration of 0.1 mmol/kg bodyweight Gd-DTPA) and supine positions. 64 sections with a voxel-resolution of 2.0 x 2.0 x 1.25 mm3-were taken during a 28 s breath hold. Three-dimensional maximum intensity projection, multiplanar reconstruction, and virtual colonoscopic images of the colon were created from these. FINDINGS: Analysis of the coronal source images in conjunction with multiplanar reconstructions revealed all relevant abnormalities, including diverticula, carcinomas, and polyps. Three dimensional maximum-intensity projections gave a morphological overview of the whole colon. Targeted projections, made up of a limited number of coronal source images, showed diverticula and smaller polyps more clearly. After patients were given intravenous contrast all colonic mass lesions were enhanced. Datasets obtained in prone patients gave the best intraluminal views of the colon. Virtual magnetic resonance colonoscopy showed colonic haustra as well as the ileocaecal valve, but did not show clearly the diverticula. All intraluminal mass lesions, on the other hand, were easy to see. INTERPRETATION: The potential of three-dimensional colonic MRI to provide accurate, minimally invasive, cost-effective polyp screening, as well as comprehensive colonic tumour staging, warrants further investigation.

Aged↗

PubMed1997

Normal myocardial perfusion assessed with multishot echo-planar imaging.

A new magnetic resonance imaging strategy is presented for accessing myocardial perfusion. Most previous work has relied on using T1-weighted fast gradient-echo imaging to monitor dynamically the signal changes during the passage of a contrast media bolus. However, the gradient-echo approach is limited by an inability to image the entire heart with adequate temporal resolution. This paper focuses on a electrocardiogram-gated multishot echo-planar imaging sequence, using the simple strategy of using the intrinsic T1 weighting produced by a repetition time equal to the heart period. To quantitate the sequence's performance with respect to normal myocardial perfusion, seven volunteers were imaged, each with three different doses of the contrast medium gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA). The first-pass dynamics of the contrast were quantified in 13 regions per heart for each examination. In all volunteers, the complete heart could be covered, with five to seven slices, every two heartbeats. Enhancement was homogeneous throughout the left ventricular myocardium, with an enhancement of approximately 50% for the optimum contrast dose of 0.05 mmol/kg Gd-DTPA.

Adult↗

PubMed1997

Coronary flow and coronary flow reserve measurements in humans with breath-held magnetic resonance phase contrast velocity mapping.

Objective evidence for coronary lesion significance can be obtained with ischemic stress testing. Since flow-limiting stenoses have already undergone compensatory vasodilatation to maintain flow, the response to vasoactive stimulation is dampened. The degree of response limitation is reflected by the coronary flow reserve (CFR). Absolute volume flow rates can be accurately and noninvasively measured with MRI techniques. The purpose was to assess the ability to measure coronary volume flow rate noninvasively, and characterize the effect of pharmacologic stress on coronary flow quantitatively by using ultrafast, breath-held segmented k-space phase-contrast-MR imaging (PC-MRI). Ten healthy volunteers were examined by using ultrafast breath-held PC-MRI. Coronary volume flow rates were measured in the anterior descending coronary artery (LAD) at rest and following intravenous administration of dipyridamole. CFR was determined based on these data. Mean LAD volume flow rates increased from 38 +/- 11 ml/min before application of dipyridamole to 169 +/- 42 ml/min. The mean CFR amounted to 5.0 +/- 2.6 (median = 4.15). This study demonstrates the feasibility of breath-held PC-MRI to noninvasively quantify coronary volume flow rates over the cardiac cycle. Pharmacologically induced changes in volume flow rate and thus CFR can be quantitated.

Adult↗

PubMed1997

Guidewire antennas for MR fluoroscopy.

Before MRI can be used for guiding vascular interventions, the problem of dependably visualizing guidewires must be solved. Ideally, the position and curvature of the tip of the guidewire should be visible to facilitate steering through the vascular system. In this paper, various antennas are described that can be incorporated into a guidewire tip. These antennas allow the guidewire to be visualized with high contrast. Computer simulation and experimental evidence are presented showing the value of adding a passive MR signal source, with a short T1, internal to the coil. The internal source increases the available signal, narrows the apparent width of the guidewire, and allows the use of fast imaging sequences.

Blood Vessels↗

PubMed1997

Virtual colonoscopy with magnetic resonance imaging: in vitro evaluation of a new concept.

BACKGROUND & AIMS: Screening for colonic polyps is desirable. A new concept based on cross-sectional and endoscopic analysis of a magnetic resonance (MR) data set is presented. METHODS: Ex vivo autopsy colonic specimens, containing artificially placed polyps, were obtained and filled with a gadolinium-containing solution. Forty-four thin-section MR images were obtained in a 1.5-T MR scanner in 28 seconds. A three-dimensional endoscopic fly-through of these images was rendered. Fly-throughs and two-dimensional cross-sectional images were analyzed by two observers for the presence of polyps. RESULTS: The average sensitivity and specificity for the detection of polyps based on three-dimensional endoscopic MR colon imaging were 87% and 96%, respectively. Analysis of cross-sectional images showed an overall sensitivity and specificity of merely 57% and 84%, respectively. The difference in the interpretation of three-dimensional MR colonoscopy and two-dimensional cross-sections was statistically significant (P < 0.001). With three-dimensional MR colonoscopy, overall sensitivity for detection of polyps measuring < or =5 mm in length and diameter was 70%; for larger polyps, it increased to 95% (P < 0.01). CONCLUSIONS: The feasibility of an MR-based endoluminal assessment of the colon is shown. Minimal invasiveness, lack of radiation exposure, and high in vitro diagnostic accuracy warrant further investigation of this novel concept.

Colonic Polyps↗

PubMed1997

[Ultrafast contrast-enhanced 3D MR angiography of the aorta and renal arteries in apnea].

PURPOSE: To determine the value of ultrafast, gadolinium-enhanced, three-dimensional breathhold magnetic resonance angiography (MRA) in the assessment of the aorta and renal arteries in comparison to conventional arteriography (CA). PATIENTS AND METHODS: 49 patients (31 m, 18 f) were evaluated with both CA and 3D MRA. The 3D MRA data set consisted of 44 continuous sections, acquired in apnoea (23-28 s) using the following parameters: TR/TE 3.9/1.5 ms, flip angle 40 degrees, 3/4 k-space acquisition. 0.3 mmol/kg BW gadolinium-DTPA were administered intravenously in a bolus, using an automated injector. A test bolus method was used for timing of the bolus and beginning of the data acquisition. Intraarterial CA was used as the gold standard in 47 patients; in two patients the intraoperative findings were employed as the standard of reference. CA and MRA were interpreted separately by two different radiologists, who were blinded to the results of the other examiner. RESULTS: All 11 accessory renal arteries were visualised on MRA. MRA-based assessment of renal artery stenosis was identical with CA in 31 of 41 (75%) stenoses, Sensitivity and specificity values for assessment of renal arterial disease were 84.4% and 96.1%, for haemodynamically significant lesions they amounted to 90% and 98.9%, respectively. CONCLUSION: The presented ultrafast contrast-enhanced 3D MRA technique allows for the reliable assessment of aortic and renal arterial morphology and pathology.

Adult↗

PubMed1997

Laser ablation-induced changes in the prostate: findings at endorectal MR imaging with histologic correlation.

PURPOSE: To correlate laser ablation-induced changes in the prostate as depicted at endorectal magnetic resonance (MR) imaging with results at histologic examination. MATERIALS AND METHODS: In eight patients with prostate carcinoma, visually guided laser ablation was performed during lymphadenectomy. Radical prostate resection was performed 4-9 days (mean, 6.9 days) after ablation in seven patients and at 70 days in one patient. The study protocol consisted of (a) endorectal T2-weighted fast spin-echo imaging, (b) dynamic T1-weighted spoiled gradient-echo imaging prior to and after injection of contrast material, and (c) gadolinium-enhanced T1-weighted spin-echo imaging. Imaging findings were correlated with macroscopic and histologic findings. RESULTS: Histologic examination revealed periurethral necrosis with a marginal zone that consisted of partially necrotic tissue, dilated vessels, and hemorrhagic areas. Considerable interindividual difference was observed in the extent of morphologic alterations (area, 0-18.0 cm3). Gadolinium-enhanced images were best suited for assessment of laser ablation-induced changes. The correlation between the volume of altered tissue measured on MR images and in macroscopic specimens was excellent (r2 = .96). CONCLUSION: MR imaging helped monitor changes induced with laser ablation (which differed greatly among individuals). MR monitoring may thus be useful in patients with obstructive benign prostatic hyperplasia after laser ablation.

Aged↗

PubMed1997

MR imaging-guided intravascular procedures: initial demonstration in a pig model.

With use of an open 1.5-T magnetic resonance (MR) imager and a tracking catheter, the authors successfully placed the catheter into the left or right sacral artery in pigs. The tracking catheter comprised a 5.3-F percutaneous transluminal angioplasty catheter with a small copper radio-frequency coil in its tip. With use of the coil as an antenna, the catheter tip position was projected in real time onto MR angiography road maps in two planes. Guidance of placement of the catheter with the MR angiography road maps allowed successful embolization, balloon occlusion, and transjugular intrahepatic puncture of the portal system. Specialized catheters can be tracked in vivo to allow MR guidance in intravascular interventional procedures.

Animals↗

PubMed1997

Evaluation of the aortoiliac and renal arteries: comparison of breath-hold, contrast-enhanced, three-dimensional MR angiography with conventional catheter angiography.

PURPOSE: To determine the diagnostic accuracy of breath-hold, contrast material-enhanced, three-dimensional (3D) magnetic resonance (MR) angiography in the assessment of the aortoiliac inflow tract and renal arteries with conventional catheter angiography as the standard of reference. MATERIALS AND METHODS: In 39 patients with symptomatic peripheral vascular disease, both catheter and contrast-enhanced, 3D MR angiography were performed. In a prospective blinded analysis, each vascular segment (23 segments per arterial tree) was evaluated for the presence of obstructive stenosis, graded as mild (<50%), severe (50%-99%), or occlusion (100%), as well as for aneurysmal disease. RESULTS: Obstructive (n = 2) and aneurysmatic aortic (n = 6) lesions and 10 of 11 accessory renal arteries were identified and graded correctly with MR angiography. For detection of hemodynamically significant stenotic lesions (>50%) or occlusions with MR angiography, sensitivity and specificity, respectively, were 93% and 98% for the renal arteries, 96% and 100% for the common iliac arteries, 93% and 93% for the external iliac arteries, and 96% and 94% for the internal iliac arteries. CONCLUSION: The diagnostic performance of contrast-enhanced 3D MR angiography is comparable with that of catheter angiography and thus may contribute to assessment of the aorta, the renal arteries, and the pelvic arterial system in patients with peripheral vascular disease before they undergo therapy.

Angiography, Digital Subtraction↗

PubMed1997

Dynamic contrast-enhanced FMPSPGR of the pancreas: impact on diagnostic performance.

OBJECTIVE: The objective of this study was to evaluate the diagnostic impact of dynamic contrast-enhanced fast multiplanar spoiled gradient-recalled imaging (FMPSPGR) of the pancreas. MATERIALS AND METHODS: MR imaging examinations of the upper abdomen for 101 patients were evaluated retrospectively and compared with histologic and surgical results as well as imaging or laboratory and clinical follow-up results. Standard T1-weighted spin-echo images, T2-weighted fast spin-echo images with fat saturation, and FMPSPGR had been obtained for all patients. Of the 101 patients, 79 also underwent fat-saturated contrast-enhanced T1-weighted spin-echo MR imaging. Qualitative analysis consisted of evaluation of overall image quality and characterization of the pancreas as normal or abnormal, for which receiver operating characteristic curves were calculated. A contrast-to-noise ratio between the pancreas and the surrounding tissue was calculated for each patient. RESULTS: By a statistically significant margin, FMPSPGR performed better than conventional spin-echo MR imaging. For FMPSPGR, sensitivity and specificity were 87% and 100%, respectively, compared with T1-weighted spin-echo sequences (sensitivity, 50%; specificity, 96%), T2-weighted spin-echo sequences with fat saturation (sensitivity, 60%; specificity, 93%), and contrast-enhanced T1-weighted spin-echo sequences with fat saturation (sensitivity, 53%; specificity, 90%). Diagnostic confidence was highest with FMPSPGR. CONCLUSION: FMPSPGR should be used in all MR imaging examinations of the upper abdomen. This technique offers better visualization of important structures and increases confidence for a more specific and accurate diagnosis than does conventional spin-echo imaging.

Contrast Media↗

PubMed1997

MR angiography of patients with peripheral arterial disease before and after transluminal angioplasty.

OBJECTIVE: This study was performed to evaluate the feasibility of using MR angiography for following up patients who have undergone interventional therapy of the infrapopliteal vascular bed. SUBJECTS AND METHODS: Fourteen patients with peripheral vascular disease underwent MR imaging before and after percutaneous transluminal angioplasty (PTA) using a two-dimensional time-of-flight technique (TR/TE, 33/3.9; section thickness, 2.9 mm). As the gold standard, selective digital subtraction angiography was obtained for all evaluated extremities before and after PTA. For data analysis, the distal peripheral arterial system was divided into 11 segments: the popliteal artery; the tibioperoneal trunk; and the proximal, mid, and distal portions of the three trifurcation vessels. Each segment was characterized as normal, mildly diseased, moderately diseased, severely diseased, or occluded. RESULTS: We found overall agreement between the two techniques in 110 segments (71%) and 123 segments (80%) on data obtained before and after PTA, respectively. Before PTA, our interpretation of MR angiograms overestimated 14 lesions (9%). After PTA, we overestimated five lesions (3%) on MR angiograms. We underestimated lesion severity in 30 cases (19%). The high incidence of agreement between the two techniques was reflected by the high Kendall's tau-beta values of .83 and .87 for data obtained before and after PTA, respectively. CONCLUSION: The excellent depiction of the PTA-induced morphologic changes suggests great potential for the use of MR angiograms during interventional follow-up.

Aged↗

PubMed1996

Azygos blood flow: phase contrast quantitation in volunteers and patients with portal hypertension pre- and postintrahepatic shunt placement.

Flow volume in the azygos venous system was quantitated with Cine-phase contrast (PC) velocity mapping in volunteers and compared with patients with known portal hypertension, who were referred for transjugular intrahepatic portosystemic shunt (TIPS) placement. Subsequently, the TIPS-induced hemodynamic effects on portal and azygos flow were analyzed. To assess intra- and intersubject variability, flow in the azygos veins was measured in each of 10 normal subjects at three different times. Subsequently, portal and azygos flow was quantitated in 20 patients with portal hypertension, before and after TIPS placement. All imaging was performed on a 1.5-tesla magnetic resonance imaging (MRI) system. Azygos flow was measured transaxially at the midthoracic level. Cine-PC flow measurements of the main portal vein followed morphological evaluation of the portal venous system with axial and coronal breath-held magnet resonance angiogram. Azygos flow in normal subjects was characterized by high inter- and low intrasubject variability. Azygos flow in patients with portal hypertension was significantly higher (P < .001). Following successful TIPS placement in 18 patients, Cine-PC revealed a mean decrease in azygos flow of 46.3% (P < .001) and a 134% (P < .001) increase of portal flow. Reflecting the complexity of portal hemodynamics, there was no correlation between the changes in the portal and azygos systems. In 2 patients with early occlusion of TIPS, documented invasively, portal and azygos flow values remained largely unchanged. Cine-PC enables the noninvasive, quantitative assessment of flow within the azygos venous system. Azygos flow was found to be markedly elevated in patients with portal hypertension. Combined portal and azygos PC flow measurements quantitate the therapeutic effect of TIPS placement.

Adult↗

PubMed1996

Biopsy needle susceptibility artifacts.

Understanding the appearance of thin metallic structures in magnetic resonance imaging is important for evaluating the potential role of MRI in guiding and monitoring percutaneous interventions. As most MR compatible instruments are made from materials with a susceptibility different from water, their visibility is enhanced beyond what is expected on the grounds of displaced water alone. Unfortunately, this artifactually enhanced visibility is not constant, but instead depends on a variety of factors. This article presents computer simulations of the image distortion resulting from magnetic susceptibility differences between a needle and the surrounding tissue. The simulations show not only an artifact size that is dependent on needle composition, orientation, and pulse sequence, but also a corresponding shift of the artifact center away from the actual center of the needle. These effects place limits on the accuracy of MRI-guided needle tip placement.

Artifacts↗

PubMed1996

Ultra-high-speed MR imaging.

Conventional magnetic resonance imaging (MRI) has been shown to provide excellent morphological images of the body organs, particularly structures undergoing little physiologic motion. Nevertheless, the clinical usefulness of MRI has been hampered by long acquisition times, high cost of scanning because of limited patient throughput, and image artifacts due to patient motion. With recent technical developments, several ultrafast scanning techniques capable of acquiring images in a breath-hold now find their introduction into clinical use. The system improvements are potentially useful for a vast range of applications hitherto not accessible to MR imaging. Among these are functional brain imaging, realtime imaging of cardiac motion and perfusion, fast abdominal imaging, improved MR angiography, and potentially real-time monitoring of interventional procedures. Whereas some ultrafast techniques can be performed on conventional scanners, echo-planar imaging, the fastest currently available data acquisition strategy, requires specially designed hardware. This article provides an overview of the technical advances in ultrafast MRI and discusses potential applications and the possible future impact on body scanning.

Humans↗

PubMed1996

Technical note--approach to myocardial perfusion with echo planar imaging.

PURPOSE: To evaluate the feasibility of MRI-based myocardial first-pass contrast perfusion imaging with a multi-shot echo planar imaging (EPI) technique. SUBJECTS AND METHODS: A non-sequential (ECG-triggered) gradient echo two-shot EPI acquisition strategy capable of covering the entire heart in contiguous 10-mm sections every two cardiac cycles with an in-plane resolution of 1.56 X 1.56 mm was implemented on a 1.5-T Signa Advantage Scanner equipped with prototype hardware for non-resonant EPI in the transverse plane. The heart of a single volunteer was studied prior to and following the intravenous bolus application of a paramagnetic contrast agent (Gd-DOTA, 0.2 mmol/kg). RESULTS: Twelve contiguous transaxial 10-mm EPI images were obtained every two RR intervals for a total of 40 s. The myocardial contrast perfusion study was technically adequate. Contrast caused a signal loss of 87% in the right and 67% in the left ventricle and 59% in the myocardium. CONCLUSION: First-pass myocardial perfusion imaging with a gradient echo, two-shot echo planar imaging strategy is feasible.

Adult↗

PubMed1996

Towards active guidewire visualization in interventional magnetic resonance imaging.

Improving the visibility of interventional devices is of paramount importance if MRI-guided fluoroscopy is to become a reality. Passive visualization is problematic in that the susceptibility-induced artifacts are material- and orientation-dependent. Here a concept is presented for making interventional devices visible. It involves fitting a device with a straight-wire antenna. As the sensitivity of such an antenna is highest for signal sources in the immediate neighborhood, using the antenna for reception gives an outline image. In this manner a guidewire or other interventional device could be made MRI-visible. The image appearance of a straight-wire antenna depends on the orientation of the device with respect to the main magnetic field and imaging plane. This phenomena is discussed theoretically and documented with MR images.

Catheterization↗

PubMed1996

[Puncture with an open-sided, interventional MRI system. Illustration with a case report].

INTRODUCTION AND METHODS: A 0.5 T open-configuration MR system allows free access to the patient via a 58-cm-wide opening on both sides of the machine. A newly developed system for needle guidance enables the examiner to perform biopsies in combination with real-time imaging and to position laser fibers in the human body. For imaging, a 2D gradient echo sequence is used (TR 19 ms, TE 9 ms, flip angle 30 degrees FOV 24 x 24 cm, slice thickness 10 mm matrix 256 x 128). The acquired images are displayed on two LCD screens localized within the MR system, thus allowing an interactive needle guidance. This procedure is illustrated by a case report. DISCUSSION: The handling of the system for needle guidance was simple, mainly due to a real-time adaption of the scan plane to the needle direction. The possibility of multi-angulated approaches makes biopsies of hardly accessible anatomic regions feasible. CONCLUSION: We think that MR-guided needle positioning will play an important role in combination with thermosensitive therapies. Thermosensitivity of MR imaging allows extensive monitoring of such interventions.

Adult↗

PubMed1996

[Influence of respiration and pulsatility on the accuracy of MR-phase contrast flow measurements: "in vitro" evaluation].

PURPOSE: Determination of the influence of pulsatility of blood flow and respiration-induced vascular motion on the accuracy of MR phase contrast flow measurements. MATERIAL AND METHODS: Flow measurements in phantoms were performed with the phase contrast technique in a 1.5 Tesla MRI system using different flow volumes, varying degrees of flow pulsatility and a varying number of image phases. To determine the influence of respiratory motion on flow measurement accuracy, flow data was collected during motion of the whole phantom. RESULTS: Flow measurements based on 6 and 16 image phases were significantly more accurate (p < 0.05) than those based on one phase. An increase in the degree of pulsatility resulted in a widening of the error range. Hence, increasing pulsatility demands an increase in the number of acquired phases to maintain sufficient measurement accuracy. Simulated respiratory motion with an excursion depth of only 5 mm resulted in a significant overestimation of true flow ranging between 22.9 and 42.1%. Measurements without simulated respiratory motion were more accurate (p < 0.001). An excursion depth of 15 mm led to a vast increase in the apparent vessel size in excess of 100%. Flow volume measurements increased accordingly to 1126 ml/min (true flow = 720 ml/min). CONCLUSION: Accurate phase-contrast based flow measurements require an adjustment of acquisition parameters to correspond to the physiology of the vessel under consideration. Flow data in vessels subject to respiratory motion should only be collected in apnoea.

Blood Flow Velocity↗