Biomedical subjects

J F Debatin

Publications and source records attributed to J F Debatin.

At least 19 recordsLinked to original sources

PubMed1998

Tissue-independent MR tracking of invasive devices with an internal signal source.

An improved MR tracking coil design is described that provides more robust tracking performance. It is shown theoretically and experimentally that a coil equipped with an internal spin source increases the signal-to-noise ratio in comparison to a coil system without internal source. The tracking behavior is stable even in air, which is important for laparoscopic work, in which the device has to be placed inside the inflated abdomen. Two types of coil windings were tested: one with the windings perpendicular to the coil axis and the other one with the windings tilted relative to this axis. The experiments showed no significant effect on the signal-to-noise ratio between the two types. The improved MR-tracking coil design with internal source was successfully used in cholecystostomies and in laparoscopic interventions; both procedures were performed on swine.

Animals↗

PubMed1998

Detection of breast cancer with conventional mammography and contrast-enhanced MR imaging.

The aim of this study was to compare the diagnostic performance of conventional mammography and dynamic contrast-enhanced fast 3D gradient-echo (GRE) MRI regarding the detection and characterization of breast lesions relative to histopathologic analysis and to assess the results of a combined evaluation of both methods. fifty consecutive patients with 63 histopathologically verified breast lesions underwent dynamic contrast-enhanced GRE MRI in addition to routine conventional mammography. All lesions were classified by both methods on a five-point scale as benign or malignant, and the results were correlated to histopathology. Conventional mammography and dynamic MRI yielded a sensitivity and specificity of 82 and 64 %, and 92 and 76 %, respectively. The difference between the results was statistically not significant (p > 0.05) with areas under the receiver-operating-characteristics curves of 0.807 for mammography and 0.906 for MR imaging. Combination of the results of both methods slightly increased the sensitivity for detection of breast cancer to 95 % but decreased specificity to 52 %. In this selected patient subset, including only patients referred for excisional biopsy, contrast-enhanced dynamic MRI proved more sensitive and specific than conventional mammography regarding the detection of malignancy. While a combination of both methods yields a slightly improved sensitivity, specificity is vastly reduced.

Adult↗

PubMed1998

MR imaging of the augmented breast.

Mammographic evaluation of the augmented breast is challenging, since breast implants obscure significant amount of breast tissue while diminishing the effect of compression. Posttherapeutic scarring can make mammographic interpretation even more difficult. MRI has thus evolved into the modality of choice for diagnosing implant complications as well as detection of primary or recurrent breast cancer in these patient population. The present article attempts to give an overview of the MR findings of different breast augmentation and reconstruction techniques, i. e. prosthetic breast implants, breast reconstruction with autogenous tissue, free silicone injections and fat grafts, and their complications.

Adipose Tissue↗

PubMed1998

Dynamic MR defecography with a superconducting, open-configuration MR system.

PURPOSE: To evaluate dynamic magnetic resonance (MR) defecography performed with a superconducting, open-configuration system in diagnosis of defecation disorders. MATERIALS AND METHODS: Five healthy volunteers and 15 patients with defecation disorders were studied with MR defecography performed with a superconducting, open-configuration system; the patients also underwent fluoroscopic defecography. Before MR imaging, the rectum was filled with 300 mL of mashed potatoes mixed with 1.5 mL of gadopentetate dimeglumine. T1-weighted gradient-echo images were acquired every 2 seconds in the midsagittal plane with the patient at rest, at maximal contraction of the anal sphincter, during straining, and during defecation. RESULTS: MR defecography permitted analysis of the anorectal angle, anal canal, puborectal muscle, and descent of the pelvic floor. Owing to the high signal intensity of the intraluminal contrast material, the rectal walls were well demonstrated on the MR images, permitting visualization of intussusception and rectocele. Concomitant demonstration of structures surrounding the anorectal canal was helpful in assessment of spastic pelvic floor syndrome and descending perineum syndrome. MR defecography was superior to fluoroscopic defecography and allowed detection of all clinically relevant pathologic conditions except for one. CONCLUSION: Dynamic MR defecography is an attractive alternative for evaluation of defecation disorders.

Aged↗

PubMed1998

Radio-frequency-induced thermoablation: monitoring with T1-weighted and proton-frequency-shift MR imaging in an interventional 0.5-T environment.

PURPOSE: To evaluate the feasibility and accuracy of monitoring radio-frequency (RF) ablation with an open-configuration, 0.5-T magnetic resonance (MR) imager. MATERIALS AND METHODS: Thirty-six in vivo RF ablation experiments were performed in porcine paravertebral muscle (n = 24) and liver (n = 12). A 90 degrees C tip temperature was applied for 3-9 minutes. MR images were acquired after continuous or during intermittent RF application. Temperature changes were monitored as signal intensity and proton-frequency-shift (PFS) alterations in two T1-weighted gradient-echo sequences. An update image was obtained every 2.5 seconds (20/10 [repetition time msec/echo time [TE] msec]) or every 5.0 seconds (40/20). A color-coded subtraction technique enhanced the signal intensity and PFS changes. Macroscopic coagulation size was compared with MR image lesion size. RESULTS: The RF application mode had no significant effect on coagulation size in muscle or liver (P > .05). Twenty-two of 24 coagulative lesions in muscle and nine of 12 in liver were demonstrated with the PFS technique. Accuracy of lesion size determination depended on TE (TE = 20 msec, r = .95; TE = 10 msec, r = .78 [P < .01]). The T1-weighted technique depicted only six of 24 muscle and three of 12 liver lesion ablations. In the lesions depicted, macroscopic size was significantly underestimated (P < .001). CONCLUSION: PFS MR monitoring of RF effects in liver and muscle is feasible and accurate. The PFS technique outperformed the T1-weighted technique.

Animals↗

PubMed1998

Detection of mass lesions with MR colonography: preliminary report.

PURPOSE: To evaluate the performance of magnetic resonance (MR) colonography in the detection of colorectal mass lesions. MATERIALS AND METHODS: Twenty-three patients underwent MR colonography preceding colonoscopy. The colon was filled with a gadolinium-water mixture (1:100) with MR imaging guidance, and the patient was imaged prone and supine with a breath-hold three-dimensional spoiled gradient-recalled sequence. In addition, two-dimensional spoiled gradient-recalled images were acquired before and after intravenous administration of gadopentetate dimeglumine. Images were interactively analyzed on the basis of multiplanar reconstruction by two radiologists. For regions that were not conclusively assessable with multiplanar reconstruction, virtual intraluminal endoscopic images of the colon were reconstructed. MR findings were correlated with colonoscopic results. RESULTS: Two patients were excluded from the analysis. Findings in eight of 11 patients were correctly assessed as normal and in six of 10 as mass-positive. In the four patients with false-negative findings, one had two 8-mm polyps and the other three had polyps smaller than 5 mm. All nine mass lesions larger than 10 mm, as well as four of the 10 polyps ranging between 5 and 10 mm, were detected, but all polyps smaller than 5 mm were missed. In contrast to the polyps less than 5 mm, the four missed polyps (5-10 mm) could be identified retrospectively on virtual intraluminal endoscopic images. Contrast enhancement was documented in 13 polyps. CONCLUSION: Three-dimensional MR colonography provided virtual colonoscopic viewing and helped detection of colonic polyps.

Adult↗

PubMed1998

Diagnostic impact of four postprocessing techniques in evaluating contrast-enhanced three-dimensional MR angiography.

OBJECTIVE: The purpose of this study was to determine the added diagnostic value of various three-dimensional (3D) data viewing techniques when analyzing contrast-enhanced 3D MR angiography. MATERIALS AND METHODS: Twenty patients (mean age, 62 years) with symptomatic peripheral vascular disease were assessed with breath-hold, contrast-enhanced 3D MR angiography and catheter angiography, which served as the standard of reference. After an initial interpretation of the 3D MR angiographic data sets based only on standardized maximum intensity projections (MIP), the diagnostic gain of the stepwise addition of interactive multiplanar reformations, shaded-surface displays (SSD), and virtual intraarterial endoscopy (VIE) images was calculated. Time required for each step of postprocessing was measured. RESULTS: Pathologic changes were revealed by catheter angiography in 60 vascular segments (50 severe stenoses, seven aneurysms, and three occlusions). The average postprocessing times were MIP, 8 min (range, 5-12 min); multiplanar reformations, 9 min (range, 3-11 min); SSD, 15 min (range, 8-25 min); and VIE, 40 min (range, 18-63 min). Addition of multiplanar reformations to MIPs resulted in the greatest gain of diagnostic accuracy, from 92% to 96%, and diagnostic confidence. When analysis was based on all four techniques, receiver operating characteristic curve analysis revealed only minimal improvements in diagnostic confidence, whereas diagnostic accuracy remained unchanged at 96%. CONCLUSION: Accurate and time-effective analysis of contrast-enhanced 3D MR angiography should be based on MIP algorithms and multiplanar reformations. Additional evaluation with VIE or SSD techniques is time-consuming and provides little diagnostic gain.

Adult↗

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

Imaging temperature changes in an interventional 0.5 T magnet: in-vitro results.

BACKGROUND AND OBJECTIVE: To evaluate the ability of monitoring laser induced temperature changes in an open, interventional 0.5 T magnet, adopting fast T1-weighted sequences. MATERIALS AND METHODS: A fast gradient echo- (FGRE) and a fast spoiled gradient echo-sequence (FSPGR), both enabling an image update every 2.5 s, were investigated for their ability to visualize laser tissue effects at 5 Watt. Laser induced temperature was fluorooptically measured and correlated with signal intensity (SI) changes depicted by magnetic resonance imaging (MRI). MRI-lesions were compared with macroscopic findings. RESULTS: SI changes on FGRE images appeared as early as 15 s following the onset of laser application and were significantly more pronounced than those seen on FSPGR images (p < .0001). A correlation of r = 0.94 (FGRE) and r = 0.92 (FSPGR) between temperature and SI loss was established. Owing to a steeper slope, the FGRE sequence was considered more sensitive to temperature changes. The areas of macroscopic tissue change correlated with those of SI loss, but lesion size was generally underestimated by MRI. CONCLUSION: Laser monitoring is possible with rapid image updates in a midfield (0.5 T) interventional MRI environment using fast gradient echo sequence designs.

Animals↗

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

MRI contrast media - new developments and trends. CTA vs. MRA.

Recent developments in the non-invasive techniques of magnetic resonance angiography (MRA) and computerised tomographic angiography (CTA) are challenging conventional catheter angiography. Current indications for both techniques are discussed, such as their ability to diagnose aortic, pulmonary, renal, carotid and peripheral vascular diseases. Both tools provide almost identical clinical results, although each has their own advantages and disadvantages. MRA should be the technique of choice in young patients or those with real impairment since the gadolinium-based contrast agents are non-ionising and do not cause nephrotoxicity. On the other hand, MRA examination times are longer than those typically required for CTA, and therefore MRA is less suited to examinations of acute conditions.

Angiography↗

PubMed1997

[Value of contrast-enhanced 3D magnetic resonance angiography of the renal arteries].

PURPOSE: To determine the value of gadolinium-enhanced, three-dimensional breath-hold Magnetic Resonance Angiography (MRA) in the assessment of the aorta and renal arteries in comparison to conventional arteriography (CA). PATIENTS AND METHODS: 49 patients were evaluated with both CA and 3D MRA. 0.3 mmol/kg BW gadolinium-DTPA was 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. The intraarterial CA was used as the gold standard. RESULTS: MRA-based assessment of renal artery stenosis was identical with CA in 31 of 45 stenoses (68.8%). Sensitivity and specificity for assessment of renal arterial disease by MRA were 84% and 96%; for clinically relevant lesions they amounted to 90% and 98%. CONCLUSION: The presented contrast-enhanced 3D MRA technique allows for the reliable assessment of renal arterial morphology and pathology.

Adult↗

PubMed1997

Three-dimensional contrast-enhanced magnetic resonance angiography of the thoracic vasculature.

Magnetic resonance angiography (MRA) has become a useful non-invasive imaging technique for the assessment of vascular disease. Due to limitations such as respiratory motion artefacts, saturations problems, and long acquisition times, applications of MRA in the thorax have largely been restricted to imaging of the aorta. The recent introduction of breath-hold three-dimensional (3D) contrast-enhanced MRA promises not only to enhance conventional MR protocols for aortic imaging, but to extend the clinical indications of MRI to diseases affecting other vascular structures of the thorax, most notably the pulmonary arteries. This article describes the technical aspects of contrast-enhanced 3D MRA and reviews existing and potential future clinical applications.

Aorta, Thoracic↗

PubMed1997

Magnetic resonance-guided laparoscopic interstitial laser therapy of the liver.

BACKGROUND: There is a necessity for an imaging method during laparoscopy to get a three-dimensional access to the target. In this study we evaluated laparoscopic interstitial laser therapy of the liver under magnetic resonance imaging guidance. METHODS: Five domestic pigs underwent laparoscopy in an open-configuration magnetic resonance system. Under simultaneous real-time magnetic resonance imaging interstitial laser therapy was applied to the liver. Magnetic resonance images, macroscopic aspects of the lesions, and light microscopic findings were compared. RESULTS: The interventions could be safely performed. There was no image artifact caused by instruments or by the carbon dioxide. Dynamic gadolinium-enhanced imaging proved to significantly predict the macroscopic volume of the laser lesions. CONCLUSIONS: Magnetic resonance-guided laparoscopic interstitial laser therapy of the liver combines the advantages of minimal invasive surgery and magnetic resonance imaging. Further development should focus on laparoscopic instruments and temperature sensitive sequences.

Animals↗

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↗