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Biomedical subjects

A Buecker

Publications and source records attributed to A Buecker.

At least 19 recordsLinked to original sources
PubMed2005

Treatment of 10 dogs with discospondylitis by fluoroscopy-guided percutaneous discectomy.

Ten dogs suffering from discospondylitis were treated by percutaneous discectomy and local and systemic antibiotic therapy. With fluoroscopic guidance, a cylinder 5 mm in diameter was removed from the centre of the intervertebral space, yielding a fenestration and decompressing the disc without producing any spinal instability. The causative bacteria were identified in nine of the 10 biopsy specimens, but in only three urine cultures and four blood cultures. In two cases, the antibiotics used initially had to be changed owing to the organisms' antibiotic resistance. The clinical signs of the dogs improved markedly after two to nine days (mean 4.2 days) and had resolved completely after five to 14 days (mean 9.1 days). In all the cases the disease could be classified histologically as either acute or chronic, and the disease was classified as chronic in one dog. No side effects were observed.

Animals↗
PubMed2005

Inversion prepared coronary MR angiography: direct visualization of coronary blood flow.

PURPOSE: Visualization of coronary blood flow by means of a slice-selective inversion pre-pulse in concert with bright-blood coronary MRA. MATERIALS AND METHODS: Coronary magnetic resonance angiography (MRA) of the right coronary artery (RCA) was performed in eight healthy adult subjects on a 1.5 Tesla MR system (Gyroscan ACS-NT, Philips Medical Systems, Best, NL) using a free-breathing navigator-gated and cardiac-triggered 3D steady-state free-precession (SSFP) sequence with radial k-space sampling. Imaging was performed with and without a slice-selective inversion pre-pulse, which was positioned along the main axis of the coronary artery but perpendicular to the imaging volume. Objective image quality parameters such as SNR, CNR, maximal visible vessel length, and vessel border definition were analyzed. RESULTS: In contrast to conventional bright-blood 3D coronary MRA, the selective inversion pre-pulse provided a direct measure of coronary blood flow. In addition, CNR between the RCA and right ventricular blood pool was increased and the vessels had a tendency towards better delineation. Blood SNR and CNR between right coronary blood and epicardial fat were comparable in both sequences. CONCLUSION: The combination of a free-breathing navigator-gated and cardiac-triggered 3D SSFP sequence with a slice-selective inversion pre-pulse allows for direct and directional visualization of coronary blood flow with the additional benefit of improved contrast between coronary and right ventricular blood pool.

Adult↗
PubMed2005

[Heart tumors: magnetic resonance imaging and multislice spiral CT].

Transthoracic echocardiography is usually the initial diagnostic test in patients with a suspected cardiac mass. However, this technique is restricted by its small field of views and insufficient acoustic window in some patients. Magnetic resonance imaging (MRI) and, since its introduction, multislice spiral computed tomography allow for detailed delineation of intra and pericardiac tumors, their extent, and their influence on cardiac function. Primary benign and malignant cardiac tumors have several characteristic features in MR imaging. Assessment of such features may narrow down the differential diagnosis or even allow for reliable diagnosis in selected cases. Many such features can also be assessed using MSCT. This article provides an overview of examination protocols of MRI and CT for cases in which a cardiac mass is suspected and describes the appearance of primary and secondary cardiac masses as well as intracavitary thrombi.

Adult↗
PubMed2005

Partial percutaneous discectomy for treatment of thoracolumbar disc protrusion: retrospective study of 331 dogs.

OBJECTIVES: To determine retrospectively the prognosis and outcome for dogs diagnosed with thoracolumbar intervertebral disc disease treated with partial percutaneous discectomy (PPD). METHODS: Three hundred and thirty-one dogs presenting with symptoms of thoracolumbar intervertebral disc disease from 1998 to 2003 were treated with PPD. Diagnosis and location of intervertebral disc disease was confirmed by clinical examination, radiography, myelography and magnetic resonance imaging. PPD was performed via fluoroscopy-guided removal of a 5 mm bore cylinder out of the central intervertebral space. RESULTS: Clinical success after surgery was achieved in 159 (88.8 per cent) grade II to IV patients and 58 (38.2 per cent) grade V patients. The mean (sd) time from percutaneous discectomy to first improvement was 8.3 (13.2) days. CLINICAL SIGNIFICANCE: The PPD approach to the thoracolumbar spine involves minor trauma (yielding rapid recovery) and less pain, and produces results comparable with open fenestration. Consequently, this simple minimal invasive technique can be recommended as an alternative to the technique of fenestration and can be easily performed in addition to open surgical decompression techniques or prophylactically. However, it is not a replacement for surgical treatment in dogs with thoracolumbar disc disease that require removal of disc fragments causing spinal cord or nerve root compression.

Animals↗
PubMed2003

Coronary MR imaging using free-breathing 3D steady-state free precession with radial k-space sampling.

PURPOSE: To investigate the potential of free-breathing 3D steady-state free precession (SSFP) imaging with radial k-space sampling for coronary MR-angiography (MRA), coronary projection MR-angiography and coronary vessel wall imaging. MATERIALS AND METHODS: A navigator-gated free-breathing T2-prepared 3D SSFP sequence (TR = 6.1 ms, TE = 3.0 ms, flip angle = 120 degrees, field-of-view = 360 mm(2)) with radial k-space sampling (384 radials) was implemented for coronary MRA. For projection coronary MRA, this sequence was combined with a 2D selective aortic spin tagging pulse. Coronary vessel wall imaging was performed using a high-resolution inversion-recovery black-blood 3D radial SSFP sequence (384 radials, TR = 5.3 ms, TE = 2.7 ms, flip angle = 55 degrees, reconstructed resolution 0.35 x 0.35 x 1.2 mm(3)) and a local re-inversion pulse. Six healthy volunteers (two for each sequence) were investigated. Motion artifact level was assessed by two radiologists. RESULTS: In coronary MRA, the coronary lumen was displayed with a high signal and high contrast to the surrounding lumen. Projection coronary MRA demonstrated selective visualization of the coronary lumen while surrounding tissue was almost completely suppressed. In coronary vessel wall imaging, the vessel wall was displayed with a high signal when compared to the blood pool and the surrounding tissue. No visible motion artifacts were seen. CONCLUSION: 3D radial SSFP imaging enables coronary MRA, coronary projection MRA and coronary vessel wall imaging with a low motion artifact level.

Adult↗
PubMed2003

Quantitative and qualitative assessment of left ventricular volume with ECG-gated multislice spiral CT: value of different image reconstruction algorithms in comparison to MRI.

PURPOSE: To assess the value of different image reconstruction algorithms for assessment of the left ventricular function using retrospectively ECG-gated multislice spiral computed tomography (MSCT) of the heart. MATERIAL AND METHODS: MSCT and cine magnetic resonance (MR) imaging of the heart were performed in 15 patients. For MSCT, standard and multisegmental image reconstruction with improved temporal resolution were used. Standardized multiplanar reformats in the short axis and long axis views were reconstructed from MSCT data. End-systolic (ESV) and end-diastolic volume (EDV), stroke volume (SV), ejection fraction (EF) and myocardial mass (MM) were calculated. Left ventricular wall motion was assessed qualitatively. RESULTS: MSCT was in acceptable agreement with MR imaging for quantification of the ventricular function. According to the Bland-Altman approach the mean differences for the left ventricular volumes (ESV, EDV, SV) ranged from -9.6 ml to 3.1 ml with standard image reconstruction and from -0.6 ml to 1.9 ml utilizing multisegmental image reconstruction with limits of agreement ranging from -26.6 ml to 12.5 ml and -15.6 ml to 15.0 ml, respectively. Applying the multisegmental image reconstruction algorithm, a significantly improved agreement with the MR data was found for EDV, SV and EF. For wall motion analysis, standard image reconstruction showed a significant difference to MR imaging with a correspondence in 83.75% of the 240 assessed segments, while multisegmental image reconstruction agreed with MR imaging in 92.5% of the segments. CONCLUSION: Multisegmental image reconstruction improves the quantitative assessment of left ventricular function when compared to standard image reconstruction. Multisegmental image reconstruction allows qualitative wall motion analysis.

Adult↗
PubMed2002

T1-weighted MR-lymphography after intramammary administration of Gadomer-17 in pigs.

PURPOSE: To evaluate the enhancement of regional lymph nodes and lymphatic vessels after intramammary injection of Gadomer-17. MATERIALS AND METHODS: T1-weighted MR-lymphography was performed in 8 domestic pigs after intramammary injection of 5 - 10 micromol/kg bodyweight (bw) Gadomer-17 on a 1.5 T-MR scanner. T1-weighted 3D gradient-echo images were acquired 10 to 120 minutes after contrast material injection in coronal and sagittal planes. The contrast enhancement of the draining lymphatic system was qualitatively assessed by two radiologists applying a three grade scale. RESULTS: T1-Weighted MR-lymphography after intramammary injection of Gadomer-17 was feasible in each pig. A dose of 5 micromol/kg body weight Gadomer-17 was best suited for MR-lymphography of the mammary line and the draining lymphatic system. Enhancement of regional lymph nodes and lymphatic vessels was classified as good in 5, and excellent in three cases. CONCLUSIONS: Intramammary injection of Gadomer-17 allows for good quality T1-weighted MR-lymphography of mammary gland draining regional lymph nodes and lymphatic vessels. This new technique might offer potential for the evaluation of the sentinel lymph node in patients with breast cancer.

Animals↗
PubMed2002

Real-time-MR guidance for placement of a self-made fully MR-compatible atrial septal occluder: in vitro test.

PURPOSE: This in vitro study investigated the feasibility to visualize the placement of three different atrial septal occluder systems using real-time MR control. METHODS: The experiments were performed on an interventional 1.5 T high field whole body system. Real-time MR imaging was achieved by radial or spiral k-space filling in conjunction with the sliding window reconstruction technique yielding an imaging speed of 15 frames per second. The CardioSeal, Amplatzer Septal Occluder and a specially designed MR-compatible closure device were tested in a water bath. A punctured plastic wall served as model for the atrial septal defect. RESULTS: The delivery systems of the CardioSeal and Amplatzer Occluder were ferromagnetic and caused substantial artifacts, making the device placement impossible, even if the magnetic forces would have been acceptable. The self-made prototype caused only minor susceptibility artifacts allowing its visualization on the MR images. The MR imaging techniques applied enabled real-time control of the occluder including steering through the artificial septal foramen and visualization of the occluder deployment. CONCLUSION: Real-time MR imaging allows for guidance and placement of an MR-compatible septal occluder in vitro suggesting the feasibility to perform atrial septal occlusion under MR-guidance in vivo as well.

Heart Atria↗
PubMed2002

Navigator-gated and real-time motion corrected free-breathing MR Imaging of myocardial late enhancement.

PURPOSE: A new magnetic resonance imaging approach for detection of myocardial late enhancement during free-breathing was developed. METHODS AND RESULTS: For suppression of respiratory motion artifacts, a prospective navigator technology including real-time motion correction and a local navigator restore was implemented. Subject specific inversion times were defined from images with incrementally increased inversion times acquired during a single dynamic scout navigator-gated and real-time motion corrected free-breathing scan. Subsequently, MR-imaging of myocardial late enhancement was performed with navigator-gated and real-time motion corrected adjacent short axis and long axis (two, three and four chamber) views. This alternative approach was investigated in 7 patients with history of myocardial infarction 12 min after i. v. administration of 0.2 mmol/kg body weight gadolinium-DTPA. CONCLUSION: With the presented navigator-gated and real-time motion corrected sequence for MR-imaging of myocardial late enhancement data can be completely acquired during free-breathing. Time constraints of a breath-hold technique are abolished and optimized patient specific inversion time is ensured.

Adult↗
PubMed2001

MR-guided percutaneous drainage of abdominal fluid collections in combination with X-ray fluoroscopy: initial clinical experience.

The aim of this study was to examine the feasibility of a hybrid interventional MR system, which combines a closed bore magnet with a C-arm fluoroscopy unit for percutaneous drainage of abdominal fluid collections. During the past 2 years, we have performed four drainage procedures in four patients (mean age 47 years). Three patients had abscesses (psoas muscle, kidney, subphrenic location) and the fourth patient had a recurrent splenic cyst. All procedures were performed on an interventional MR system consisting of a 1.5-T ACS-NT scanner combined with a specially shielded C-arm. The drainages were guided by T1-weighted fast gradient-echo images, T2-weighted single-shot turbo spin-echo images or both. A standard 18 G (1.2 mm) nonferromagnetic stainless steel needle with a Teflon sheath was used for the punctures following which a 0.89 mm nitinol guidewire was inserted into the fluid collection. Thereafter, the patient was positioned in the immediate adjacent fluoroscopy unit and a drainage catheter was placed under fluoroscopic control. All drainage catheters were successfully placed into the fluid collections, as proven by fluid aspiration and resolution of the collection. The mean time needed for the entire drainage procedure (MR and fluoroscopy) was 110 min. No procedure-related complications occurred. It is feasible to perform drainage procedures on a closed-bore MR scanner. The multiplanar imaging capabilities of MR are particularly helpful for fluid collections in the subphrenic location.

Abdominal Abscess↗
PubMed2001

MR-venography using high resolution True-FISP.

A new fast MR-venography approach using a high resolution True-FISP imaging sequence was investigated in 20 patients suffering from 23 deep vein thromboses. Diagnosis was proven by x-ray venography, CT or ultrasound examination. The presented technique allowed for clear thrombus visualization with a high contrast to the surrounding blood pool even in calf veins. Acquisition time was less than 10 minutes for imaging the pelvis and the legs. No contrast media was needed. The presented high resolution True-FISP MR-venography is a promising non-invasive, fast MR-venography approach for detection of deep venous thrombosis.

Adolescent↗
PubMed2001

Improved in-stent magnetic resonance angiography with high flip angle excitation.

RATIONALE AND OBJECTIVES: To optimize the intraluminal signal intensity of a nitinol stent by performing contrast-enhanced three-dimensional magnetic resonance angiography (CE-MRA) with varying flip angles (FAs). METHODS: Contrast-enhanced magnetic resonance angiography at 1.5 T and FAs of 30 degrees, 100 degrees, and 150 degrees was performed on five sheep with 10 iliac nitinol stents (Memotherm-FLEXX). Maximum-intensity projections (MIPs) and composite images of MIPs were performed and compared. RESULTS: Reconstructed MIPs at an FA of 150 degrees showed a slightly disturbed lumen visibility inside the stent accompanied by low-grade lumen visibility outside the stent and vice versa for an FA of 30 degrees. Composite images of a 30 degrees MIP added to a 150 degrees MIP resulted in improved image quality compared with the standard MIP of a single FA. CONCLUSIONS: Signal loss due to radiofrequency shielding inside nitinol stents imaged by CE-MRA can be reduced by applying high FAs. Composite MIP images allow simultaneous visualization of the lumen inside as well as outside the stent.

Alloys↗
PubMed2001

Diffusion-weighted MR imaging for differentiation of benign fracture edema and tumor infiltration of the vertebral body.

OBJECTIVE: The aim of this study was to investigate diffusion-weighted MR imaging for differentiation of benign fracture edema and tumor infiltration with and without accompanying fracture. SUBJECTS AND METHODS: In 10 volunteers, diffusion-weighted spin-echo, fat-suppressed spin-echo, and stimulated-echo sequences were optimized on a clinical 1.5-T scanner. In 34 patients, MR imaging with and without diffusion-sensitizing gradients (b = 598 sec/mm(2) in spin-echo and fat-suppressed spin-echo, b = 360 sec/mm(2) in stimulated-echo) was performed. Thirty-five lesions were analyzed, with 18 caused by acute (< or =10 days old) osteoporotic or traumatic fractures and 17 caused by untreated malignant vertebral infiltration including nine fractures. Signal attenuation in diffusion-weighted images and contrast-to-noise ratio were calculated. The diffusion-weighted images were analyzed by two radiologists. RESULTS: Images from three of 34 patients were excluded because of motion artifact. In osteoporotic and traumatic fractures, a strong signal attenuation of bone marrow edema was seen. In contrast to this, malignant-tumor infiltration caused only minor signal attenuation (p < 0.05), independent of accompanying pathologic fracture. All sequences showed identical changes of signal intensities. In four patients, initial diagnosis was changed by the findings in the diffusion-weighted images. CONCLUSION: Diffusion-weighted spin-echo, fat-suppressed spin-echo, and stimulated-echo sequences are equally suitable for imaging of the spine. Calculation of signal attenuation and observation of signal characteristics allowed differentiation of benign fracture edema and tumor infiltration and provided excellent distinction between benign and malignant vertebral fractures in our series.

Adult↗
PubMed2000

Real-time MR fluoroscopy for MR-guided iliac artery stent placement.

The purpose of this study was to test the feasibility of real-time magnetic resonance (MR) guidance of iliac artery stent placement. Radial scanning together with the sliding window reconstruction technique was implemented on a 1.5 T magnet, yielding a frame rate of 20 images per second. Seven prototype nitinol ZA stents were deployed in iliac arteries of living pigs under MR control. All stents were well visualized on the radial MR images, allowing depiction of the mounted stents as well as stent deployment without anatomy-obscuring artifacts. Stent placement was sucessful in all cases and took 6 minutes on average. The position of the stents was correctly visualized by real-time radial MR scanning, as proved by digital subtraction X-ray angiography. Combined radial scanning and the sliding window reconstruction technique allow real-time MR-guided stent placement in iliac arteries.

Alloys↗
PubMed2000

MR evaluation of stent patency: in vitro test of 22 metallic stents and the possibility of determining their patency by MR angiography.

RATIONALE AND OBJECTIVES: To determine the extent to which visualization of intrastent anatomy in stents of different composition and design is possible by using contrast-enhanced MR angiography. METHODS: Twenty-two MR-compatible stents, most of which had a diameter of 8 mm, were positioned in a phantom filled with aqueous gadolinium solution. Coronal and axial spoiled three-dimensional gradient-echo sequences were performed. Images were acquired with stents positioned at varying angulations to the main magnetic field B0. Profiles orthogonal to the stent axis allowed measurement of artifact sizes independent of window width and center. RESULTS: Oriented along B0, the Cragg, Corvita, Passager, Wallstent, Strecker, Impag, Perflex, and ZA stents allowed visualization of more than 48% of the lumen. The Memotherm, Smart, and Jostent SelfX stents showed a prominent reduction of the inner lumen to below 41%. The lumina of the covered Jostent, Palmaz, Sinus, and Symphony stents were completely obscured. The Impag, Perflex, and Strecker tantalum stents showed growing artifact sizes and a lumen reduction of at least 40% with increasing angulation to B0. CONCLUSIONS. Evaluation of the inner stent lumen by applying contrast-enhanced, three-dimensional gradient-echo sequences is not possible for the majority of stents because of their large artifacts. These depend on the stent type and orientation to B0. Even stents made of nitinol and cobalt alloys only allow qualitative patency assessment but no quantification of stenosis.

Artifacts↗
PubMed1997

Esophageal perforation: comparison of use of aqueous and barium-containing contrast media.

PURPOSE: To assess the need for follow-up esophagography with barium-containing contrast medium after examination with a water-soluble contrast medium in the detection of esophageal perforation. MATERIALS AND METHODS: Sixty-seven patients suspected of having esophageal perforation were examined prospectively with use of an aqueous contrast medium during a 1-year period. The examinations were performed with a digital fluoroscopy unit. Eighteen patients without proved extravasation at esophagography performed with aqueous contrast medium and without other contraindications underwent esophagography with barium-containing contrast medium. RESULTS: In four of 18 patients (22%) with unremarkable findings at esophagography performed with a water-soluble contrast medium, a perforation was detected subsequently with use of a barium-containing contrast medium. No complications related to barium extravasation occurred. CONCLUSION: Patients suspected of having esophageal perforation and who have unremarkable findings at esophagography with water-soluble contrast media need to undergo follow-up esophagography with a barium-containing contrast medium. The use of a digital fluoroscopy unit does not obviate the follow-up examination.

Adult↗
PubMedDate not supplied

MRI-guided biopsy of bone in a hybrid system.

This is a report of our experience with percutaneous, MRI-guided biopsies in 25 patients with skeletal lesions using a 1.5-T MR hybrid system. Twenty-five consecutive patients with skeletal lesions were referred for MRI-guided biopsy. Biopsies were performed with a 1.5-T Philips Gyroscan (Philips Medical Systems, Best, The Netherlands) combined with a c-arm fluoroscopy. Specimens were obtained percutaneously either with a 14- or 18-gauge "side-slit" type of biopsy needle (n = 10 skeletal lesions that had penetrated through the cortex), or using a prototype coaxial drill system powered either by hand or an optional motor (n = 15 skeletal lesions still covered with cortical bone). All but two biopsies could be completed within the MR unit. For one patient, who required a transpedicular approach to a lumbar vertebra, and for one child, who required general anesthesia, we decided to switch to CT guidance. In 19 of the 25 cases (17 of the 23 cases performed in MR), the sample was sufficient and the histopathologic diagnosis was confirmed. Three patients had an inadequate sample, and three others had adequate samples but inaccurate results. No procedural complications occurred. Percutaneous biopsy of skeletal lesions performed under MRI-guidance was found to be safe and reasonably accurate. There were no procedural complications in our small series. MRI may be used as an alternative to CT, but its role vis-à-vis CT has yet to be ascertained.

Biopsy, Needle↗