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Biomedical subjects

J F Debatin

Publications and source records attributed to J F Debatin.

At least 163 records · Page 9Linked to original sources
PubMed1996

MR venography of the calf: value of flow-enhanced time-of-flight echoplanar imaging.

OBJECTIVE: Release of a tourniquet on the thigh and termination of Valsalva's maneuver result in a transient increase in venous blood flow in the leg. The purpose of this study was to determine the value of time-of-flight echoplanar imaging performed with these flow-enhancing methods to image the veins of the calf. SUBJECTS AND METHODS: Flow volumes in the femoral veins in eight volunteers were determined with a two-dimensional phase-contrast MR imaging technique before and immediately, 20, 40, and 60 sec after termination of Valsalva's maneuver and thigh vein occlusion. Subsequently, the calf veins of 11 healthy volunteers were imaged with a two-dimensional four-shot echoplanar MR imaging technique. Forty-one 5-mm-thick sections were obtained over 10 sec immediately after termination of venous occlusion. Visibility of the three venous bundles was analyzed in the proximal, middle, and distal portions of the calf on the basis of a four-point scale. Finally, the calf of a single patient with documented DVT was imaged by the same MR imaging technique. RESULTS: Both Valsalva's maneuver and venous occlusion caused significant increases in venous flow (p < .05) only during the first 20 sec after termination of the maneuver and the occlusion. Venous occlusion had a significantly greater effect than did Valsalva's maneuver (p < .05). Flow augmentation by venous occlusion of the thigh improved calf vein visualization with time-of-flight echoplanar MR imaging (p < .0001). Of the 99 calf vein segments examined, 93 were clearly seen. Thrombi were seen in the patient study. CONCLUSION: Multishot time-of-flight echoplanar imaging can exploit the short-lived effect of mechanical flow-enhancing measures, resulting in good visualization of calf veins. The true diagnostic impact of this technique needs to be evaluated in a patient study.

Adult↗
PubMed1996

Acute pulmonary embolism: value of transthoracic and transesophageal echocardiography in comparison with helical CT.

OBJECTIVE: The goal of this study was to prospectively compare the accuracy of transthoracic and transesophageal B-mode and Doppler echocardiography with helical CT for detecting acute pulmonary embolism. SUBJECTS AND METHODS: Thirty-five consecutive patients underwent transthoracic and transesophageal echocardiography and contrast-enhanced helical CT. Echocardiographic examinations were analyzed for indirect criteria, including increased main pulmonary artery diameter, tricuspid regurgitation, and dilatation of the right ventricular cavity, as well as for direct thrombus visualization. Sensitivity, specificity, and negative and positive predictive values were calculated. RESULTS: Pulmonary embolism was revealed by helical CT in 22 of 35 patients; in 11 of these 22 cases, central pulmonary embolism was seen. Transthoracic and transesophageal B-mode echocardiography failed to reveal pulmonary embolism in nine patients, two of whom had central pulmonary embolism. The sensitivity and specificity of the combination of both echocardiographic investigations were 59% and 77% respectively (82% and 92% for central pulmonary embolism). In three patients, pulmonary embolism was diagnosed by direct clot detection with transesophageal echocardiography. In two patients, only the indirect parameters indicated pulmonary embolism. Overall indirect echocardiographic parameters were characterized by a low sensitivity that ranged from 50% for tricuspid regurgitation to 21% for main pulmonary artery diameter. CONCLUSION: In comparison with helical CT, transthoracic and transesophageal echocardiography had limited accuracy for detecting pulmonary embolism.

Acute Disease↗
PubMed1996

Contrast-enhanced MR imaging of the kidneys and adrenal glands.

Technical developments including motion artifact compensation and the use of paramagnetic contrast agents have substantially improved the performance of MR imaging of the kidneys and adrenal glands. MR imaging allows one to assess morphologic alterations of the kidneys as well as perfusion and functional derangements. MR imaging is the best noninvasive method for distinction of benign from malignant adrenal masses.

Adrenal Gland Diseases↗
PubMed1996

[Magnetic resonance controlled minimal invasive surgery: initial results and perspectives].

The development of an open-configured MR-imaging system opens new perspectives in minimal invasive surgery. The combination of laparoscopy and real-time MR imaging allows the guidance of diagnostic interventions as well as interstitial therapies of parenchymal organs. In the near future, tumor diagnosis, therapy and follow-up can be done using the same technique.

Equipment Design↗
PubMed1995

[MRI venous angiography of the abdomen].

The assessment of abdominal vessels by conventional methods is invasive and frequently does not yield an accurate diagnosis, particularly in evaluation of the portal venous system. MR angiography is non-invasive and is well suited to the examination of abdominal veins. Both vessel morphology and intravascular flow patterns can be characterized with this method. Clinical indications include portal hypertension, portal vein thrombosis, portosystemic shunts as well as assessment of congenital anomalies, thrombus and tumor propagation into the inferior vena cava and the renal veins. In the future MR angiography is likely to evolve into the modality of choice for non-invasive evaluation of abdominal venous structures.

Abdomen↗
PubMed1995

Evaluation of ultrafast phase-contrast imaging in the thoracic aorta.

PURPOSE: Two ultrafast phase-contrast (PC) data acquisition strategies, multishot echo-planar imaging (EPI)-PC and segmented k-space fast gradient-echo PC (FASTCARD-PC) were evaluated with regard to their measurement accuracy. MATERIALS AND METHOD: Flow measurements of the ascending and descending aorta were acquired in 10 healthy volunteers with an electrocardiogram (ECG)-triggered eight-shot EPI-PC sequence (TR/TE/flip 16/7.4/45 degrees, 32-ms flow-phase interval, 2 x 2 mm in plane resolution), and FASTCARD-PC (six k-lines per band, TR/TE/flip 11/6.1/45 degrees, 132-ms flow-phase interval, 2 x 1 mm in plane resolution). These were compared to flow-volume data acquired with conventional cine-PC (TR/TE/flip 24/7/45 degrees, 48-ms flow-phase interval, 2 x 1 mm in plane resolution). Using cine-PC as a gold standard, the measurement accuracy of FASTCARD-PC and EPI-PC were determined. RESULTS: Both EPI-PC and FASTCARD-PC significantly reduced data acquisition times compared to cine PC. EPI-PC flow measurements correlated well with aortic cine-PC flow-volume determinations (r = 0.98). Reflecting poorer temporal resolution, FASTCARD-PC measurements were less accurate (p < 0.05), evidenced by poor correlation with cine-PC data (r = 0.62). CONCLUSION: Ultrafast PC measurements are possible. In contrast to the segmented k-space PC technique, which is limited in temporal resolution, multishot EPI-PC provides high measurement accuracy in pulsatile vessles while keeping the image acquisition interval short enough for a comfortable breath-hold.

Adult↗
PubMed1995

Optimization of prostate carcinoma staging: comparison of imaging and clinical methods.

PURPOSE: The diagnostic value of endorectal coil MRI, body coil MRI, transrectal ultrasound, digital rectal examination and PSA levels were prospectively analysed in order to define the most accurate preoperative staging method. METHODS: 33 patients with prostate carcinoma, who underwent subsequent prostatectomy, were enrolled in the study and examined on a 1.5T system using the body coil as well as the endorectal surface coil before and after the administration of contrast material. The results were compared to digital rectal examination, prostate specific antigen levels and endorectal ultrasound. RESULTS: Staging accuracy of endorectal coil MRI was 87.9% with a sensitivity of 88.9% and specificity of 86.7%. For body coil MRI, the staging accuracy was 75.7%, the sensitivity 66.7% and the specificity 87.9%, for transrectal ultrasound 69.6%, 41.7% and 100% and for the digital rectal examination 56.6%, 33.3% and 100%, respectively. Prediction was improved by combining results of endorectal coil MRI with PSA values. CONCLUSION: Endorectal ultrasound and digital rectal examination both had a tendency to underestimate the extent of the lesion. Endorectal coil MRI proved to be the best preoperative staging method. In combination with PSA values, diagnostic accuracy could be further improved. Therefore, local staging of prostate cancer could be based on these two parameters alone.

Aged↗
PubMed1995

Fast spin-echo inversion-recovery imaging versus fast T2-weighted spin-echo imaging in bone marrow abnormalities.

RATIONALE AND OBJECTIVES: The purpose of this investigation is to compare a fat-suppressed T2-weighted fast spin-echo (FSE) sequence in bone marrow abnormalities with an FSE STIR sequence that recently has become commercially available. METHODS: Fast spin-echo images (repetition time [TR], 3500-5000 mseconds; echo time [TE], 96-114 mseconds) and FSE STIR images (TR, 3000-5000 mseconds; TE, 32-40 mseconds; inversion time [TI], 140-150 mseconds) were compared quantitatively and qualitatively calculating signal-to-noise ratios (SNRs), contrast-to-noise ratios (CNRs), and lesion conspicuity and using a qualitative scoring system. RESULTS: Signal-to-noise ratio (mean +/- standard deviation) was 36.4 +/- 19.3 for the FSE and 29.0 +/- 15.9 for the FSE STIR images (P = .002). Contrast-to-noise ratio (mean +/- standard deviation) was 18.7 +/- 14.3 for the FSE and 20.3 +/- 16.0 for the FSE STIR images (P = .45). Lesion conspicuity (mean +/- standard deviation) was 1.7 +/- 1.5 for the FSE and 3.5 +/- 4.0 for the FSE STIR images (P = .025). The most important difference in the qualitative evaluation related to the better signal homogeneity on the FSE STIR images. CONCLUSIONS: Fast spin-echo STIR images may be preferable to FSE images with fat suppression due to better image homogeneity and lesion conspicuity.

Adolescent↗
PubMed1995

Cardiac echo-planar MR imaging: comparison of single- and multiple-shot techniques.

PURPOSE: To compare the quality of cardiac images acquired with two-and four-shot echo-planar imaging (EPI) with that of images acquired with single-shot EPI. MATERIALS AND METHODS: Single-, two-, and four-shot EPI was performed to obtain axial images that traversed both cardiac ventricles. The subjects were 10 healthy men whose ages ranged from 22 to 38 years (mean, 27 years). The multiple-shot EPI data were acquired in snapshot (sequential) and cardiac-gated (non-sequential) modes. Image quality was compared by evaluation of the depiction of cardiac structures and analysis of signal intensity, contrast, and signal homogeneity. RESULTS: Multiple-shot EPI depicted the coronary and internal mammary arteries better than did single-shot EPI (P < .05). Intraventricular signal intensity was more homogeneous on multiple-shot images (P < .005). Cardiac-gated acquisition resulted in less image blurring and allowed acquisition of more phases per RR interval. CONCLUSION: Multiple-shot EPI rendered higher quality images than did single-shot EPI.

Adult↗
PubMed1995

Synchronization device for electrocardiography-gated echo-planar imaging.

An electrocardiography (ECG) synchronization technique allowed triggering of 1.5-T echo-planar acquisitions of the heart, with high gradient slew rates. In 51 volunteers (37 men and 14 women, aged 21-48 years), the ECG signal was amplified, filtered, and converted into an optical signal directly above the heart and was transmitted optically outside the bore. Reliable and artifact-free ECG tracings were obtained in all cases, regardless of the gradient switching speed.

Adult↗
PubMed1995

Real-time biplanar needle tracking for interventional MR imaging procedures.

PURPOSE: To evaluate real-time biplanar tracking of a specially designed needle with magnetic resonance (MR) imaging guidance. MATERIALS AND METHODS: The needle is made of polyetheretherketone and has a miniature radio-frequency coil incorporated into the tip. Tracking software on two workstations is used to compute three-dimensional coordinates of the coil and to display the position as a moving symbol in two imaging planes. Validation of needle tracking was performed in a harvested human liver. T2-weighted fast spin-echo images were used to target a 1-cm cyst. Success of needle placement was confirmed with aspiration and with updated gradient-recalled-echo images. RESULTS: The cyst was successfully targeted from different approaches. Tracking procedures were monitored in real time simultaneously on two separate images. CONCLUSION: Real-time biplanar needle tracking may prove to be useful for both diagnostic and therapeutic interventional MR imaging procedures.

Artifacts↗
PubMed1995

Management of congenital angiodysplasia of the lower limb: magnetic resonance imaging and angiography versus conventional angiography.

The purpose of the study was to compare magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) with conventional angiography in distinguishing congenital angiodysplasia amenable to radical cure from that in which only palliation is feasible and to design a rational pre-operative work-up in those patients undergoing an interventional procedure. Axial T1, T2 weighted spin-echo and contrast-enhanced 3D SPGR sequences were performed in 13 patients with angiodysplasia, followed by time-of-flight MRA. The results were compared with conventional arteriography and venography. Dysplasia was arteriovenous with microshunts in nine cases and purely venous in the remaining four. MRI was the best method for assessing the extent of malformation and involvement of anatomical structures. MR arteriography and MR venography were inferior to conventional techniques. It is concluded that MRI is valuable in distinguishing patients amenable to radical cure from those in whom only palliation is feasible. Pre-operatively, conventional arteriography and venography remain mandatory.

Adolescent↗
PubMed1995

Intravascular MR tracking catheter: preliminary experimental evaluation.

OBJECTIVE: This article reports on the preliminary evaluation of a new technique for guiding intravascular interventional procedures with MR imaging. Active real-time position monitoring of catheters with MR imaging is made possible by incorporating a small RF coil into the tip of the catheter. The purpose of this study was to evaluate the practicability and localizing precision of this MR catheter tracking technique in vitro and in vivo in comparison with fluoroscopy. MATERIALS AND METHODS: Feed cables employing a 0.9-mm-diameter coaxial cable, a 0.5-mm-diameter partially shielded coaxial cable, and a twisted pair cable attaching RF coils at the catheter tip to a coaxial plug at the catheter base were assessed. Further, miniature copper loop RF coils of two, three, and four turns were tested. In vitro validation of MR tracking was achieved by using a phantom consisting of a water-filled harvested segment of human aorta and iliac arteries embedded in gel. Accuracy of catheter placement was compared with MR and fluoroscopy. Subsequently, the MR tracking technique was evaluated in a swine model using a prototype 5-French MR tracking catheter. RESULTS: A fully shielded coaxial cable was found to be crucial for localizing the attached RF coil by means of the tracking technique. The number of coil turns had a lesser impact. Positions of the catheter tip measured with the MR technique and with fluoroscopy correlated well (r > .98), with a 6-mm 95% confidence interval of positional differences. Active real-time tracking of the coil-tipped catheters was achieved both in vitro and in vivo. The 5-French tracking catheter was successfully placed in the splenic and renal arteries of the swine. CONCLUSION: Robust in vivo tracking and accurate placement of catheters equipped with miniature RF coils are possible with MR imaging.

Animals↗
PubMed1995

[Fast and ultra-fast MRI imaging of the heart].

Conventional magnetic resonance imaging (MRI) is capable of providing satisfactory morphological images of the heart and the surrounding structures. It has further evolved into a well accepted modality for functional cardiac studies such as flow quantification and volumetry. MRI has, however, been hampered by long image acquisition times. This combined with its non-real-time nature and the limited spatial resolution hs made it difficult to extend MRT to the study of small cardiac structures. Recent technical improvements have made breath-held or real-time MRI feasible and thus laid the foundations for further applications in the field of cardiovascular imaging, notably MR coronary angiography, imaging of cardiac valve leaflets, as well as first-pass perfusion studies. Moreover ultrafast MR techniques may eventually replace conventional data acquisition strategies and thus drastically increase patient throughput by shortening acquisition time. This article provides an overview of the technical advances in MRI and their application to the cardiovascular system and discusses possibilities of combined ultrafast and interventional strategies.

Echo-Planar Imaging↗
PubMed1994

Interleaved echo planar flow quantitation.

A method is presented for rapid blood flow quantitation. It combines multiple shot echo planar imaging principles with phase contrast velocity encoding gradients. Preliminary validation experiments performed on a flow phantom indicate a good correlation with actual flow values. Measurements of pulsatile flow in the ascending and descending aorta, acquired in just 4 s, with a temporal resolution of 50 ms, are demonstrated.

Aorta↗