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T Sommer

Publications and source records attributed to T Sommer.

At least 19 recordsLinked to original sources
PubMed2006

Cardiac stress MR imaging with dobutamine.

Stress testing for detection of ischemia-induced wall-motion abnormalities has become a mainstay for noninvasive diagnosis and risk stratification of patients with suspected coronary artery disease (CAD). Recent technical developments in magnetic resonance imaging (MRI), including the adoption of balanced steady-state free precession (b-SSFP) sequences-preferentially in combination with parallel imaging techniques-have led to a significant reduction of imaging time and improved patient safety. The stress protocol includes application of high-dose dobutamine (up to 40 microg/kg/min) combined with fractionated atropine (up to a maximal dose of 1.0 mg). High-dose dobutamine stress MRI revealed good sensitivity (83-96%) and specificity (80-100%) for detection of significant CAD. Myocardial tagging methods have been shown to further increase sensitivity for CAD detection. Severe complications (sustained tachycardia, ventricular fibrillation, myocardial infarction, cardiogenic shock) are rare but may be expected in 0.1-0.3% of patients. Dobutamine stress MRI has emerged as a reliable and safe clinical alternative for noninvasive assessment of CAD. New pulse sequences, such as real-time imaging, might obviate the need for breath holding and electrocardiogram (ECG) triggering in patients with severe dyspnoea and cardiac arrhythmias, which may further improve the clinical impact and acceptance of stress MRI in the future.

Atropine↗
PubMed2006

Biliary metal stents and air embolism: a note of caution.

Metal stents are a valuable treatment modality for patients with biliary obstruction. However, we present here two patients whose cases may serve as a warning about an unusual complication associated with these stents. We encountered this complication after endoscopic retrograde cholangiography for obstructed metal biliary stents. The first patient, an 87-year-old man with a benign biliary stricture, failed to regain consciousness after clearing of his stent using a Dormia basket and balloon catheter. Cerebral air embolism was diagnosed on cerebral computed tomography, and transesophageal echocardiography revealed a patent foramen ovale as a precipitating factor for paradoxical air embolism. He survived and was discharged with a residual hemiparesis. In the second patient, a 54-year-old man who had a history of a Billroth II operation and chronic pancreatitis and who had a portal cavernoma with biliary obstruction due to collateral veins, electromechanical dissociation complicated the balloon-catheter stent revision. Echocardiography performed during cardiopulmonary resuscitation showed major air embolism to the right heart. The patient died. These cases demonstrate that air may gain access to the venous system during therapeutic endoscopic procedures of this type. It is likely that the large diameter of metal stents and the potential for these stents to lacerate venous structures facilitate the entry of air into the venous circulation, an event which may have life-threatening consequences.

Aged, 80 and over↗
PubMed2006

Atrial fibrillation - patients at high risk for cerebral embolism.

OBJECTIVE: Patients with atrial fibrillation (AF) have a risk of cerebral embolism. Echocardiographic parameters elevate this risk significantly. However, there is little knowledge about the long-term fate and the rate of clinically silent cerebral embolism under continued oral anticoagulation. The aims of our study were to assess prognosis of patients with AF and determine a high risk group with an increased risk of cerebral embolism under oral anticoagulation. METHODS: Consecutive patients with persistent or permanent AF and left atrial (LA) thrombi, dense spontaneous echo contrast (SEC) and/or reduced LA appendage peak emptying velocities (LAAv) were included in the study (N = 128). Patients with AF and without echocardiographic risk factors (N = 114) served as controls. All patients were examined with transesophageal echocardiography, cranial magnetic resonance imaging and clinically during a period of three years. RESULTS: During the three-year follow-up period 6 (5%) of the high risk patients had cerebral embolism with neurological deficits. 4 (3%) patients died due to embolic events and 17 (13%) patients had silent embolism as documented on MRI. In the control group 8 (7%) patients had embolic events (n = 1 clinically apparent and n = 7 silent embolism) documented on MRI, one was clinically apparent. Study patients with an event had more commonly previous thromboembolism (p < 0.0001). CONCLUSIONS: Patients with peristent or permanent AF and LA thrombi, dense SEC or reduced LAAv have an explicitly increased risk of cerebral embolism (21%) despite oral anticoagulation. Previous thromboembolic event is another important predictor for an event.

Atrial Fibrillation↗
PubMed2005

3D motion adapted gating (3D MAG): a new navigator technique for accelerated acquisition of free breathing navigator gated 3D coronary MR-angiography.

This study aimed to evaluate the influence of a new navigator technique (3D MAG) on navigator efficiency, total acquisition time, image quality and diagnostic accuracy. Fifty-six patients with suspected coronary artery disease underwent free breathing navigator gated coronary MRA (Intera, Philips Medical Systems, 1.5 T, spatial resolution 0.9x0.9x3 mm3) with and without 3D MAG. Evaluation of both sequences included: 1) navigator scan efficiency, 2) total acquisition time, 3) assessment of image quality and 4) detection of stenoses >50%. Average navigator efficiencies of the LCA and RCA were 43+/-12% and 42+/-12% with and 36+/-16% and 35+/-16% without 3D MAG (P<0.01). Scan time was reduced from 12 min 7 s without to 8 min 55 s with 3D MAG for the LCA and from 12 min 19 s to 9 min 7 s with 3D MAG for the RCA (P<0.01). The average scores of image quality of the coronary MRAs with and without 3D MAG were 3.5+/-0.79 and 3.46+/-0.84 (P>0.05). There was no significant difference in the sensitivity and specificity in the detection of coronary artery stenoses between coronary MRAs with and without 3D MAG (P>0.05). 3D MAG provides accelerated acquisition of navigator gated coronary MRA by about 19% while maintaining image quality and diagnostic accuracy.

Aged↗
PubMed2005

[3D motion adapted gating: a new navigator technique to shorten the acquisition time for coronary MRA].

PURPOSE: A major problem of free breathing coronary MR angiography (MRA) with respiratory navigator gating is low navigator efficiency and prolonged scan time due to irregular breathing patterns. 3D motion adapted gating (MAG) is a new adaptive navigator technique, which adapts in real time to changes of the end-expiratory position of diaphragm. This study evaluates the influence of 3D MAG on coronary MRA. METHODS AND MATERIALS: In 3D MAG, two additional gating windows are grouped around the conventional window. Additionally, each gating window is divided into three bands assigned to different portions of the k-space. The scan is terminated when three consecutive bands are filled and one complete image data set is collected. Free breathing navigator-gated coronary MRA was performed on 48 patients with suspected coronary artery disease. In random order, each patient underwent an ECG-gated, a 3D segmented k-space gradient echo sequence using 3D MAG and a conventional navigator technique. The coronary MRA was evaluated and compared using the following parameters: 1. navigator efficiency and scan time; 2. visualized coronary artery length; 3. qualitative assessment of image quality; and 4. detection of stenoses > 50 % in comparison with catheter angiography. RESULTS: Coronary MRA with 3D MAG had a significant increase in the average navigator efficiency (46 % +/- 12 % vs. 38 % +/- 12 %, p < 0.05), resulting in a significantly shorter scan time (mean: 18 % +/- 4 %, p < 0.05) for coronary MRA with 3D MAG compared to conventional navigator technique. Scans with and without 3D MAG had no significant differences in the continuously visualized vessel lengths, in the assessed image quality and in the sensitivity and specificity (83 % and 89 % vs. 83 % and 88 %, p > 0.05) of detecting coronary artery stenoses > 50 %. CONCLUSION: The 3D MAG technique improves the navigator efficiency and significantly (p < 0.05) shortens the scan time of navigator gated coronary MRA while maintaining image quality and diagnostic accuracy in the detection of coronary artery stenoses.

Adult↗
PubMed2005

[Magnetic resonance imaging of the brain in patients with cardiac pacemakers. Experimental and clinical investigations at 1.5 Tesla].

PURPOSE: In-vitro and In-vivo evaluation of feasibility and safety of MRI of the brain at 1.5 T in patients with implanted pacemakers (PM). MATERIALS AND METHODS: 24 PM models and 45 PM electrodes were tested In-vitro with respect to translational forces, heating of PM leads, behaviour of reed switch (activated vs. deactivated) and function at a 1.5 T MRI-system (actively shielded, maximum field gradient: 30 mT/m; rise time: 150 T/m/s). Based on these results, 63 MRI examinations in 45 patients with implanted PM were performed. Prior to MRI the PM were re-programmed in an asynchronous mode. The maximum SAR of MRI-sequences was limited to 1.2 W/kg. Continuous monitoring of ECG and pulse oximetry was performed during MRI. PM inquiry was performed prior to MRI, immediately after MRI and -- to assess long-term damages -- three months after the MRI exams, including determination of stimulation thresholds to assess potential thermal myocardial injuries at the lead tips. RESULTS: Translational forces (F (max) < or = 560 mN) and temperature increase (DeltaT (max) < or = 2.98 degrees C) were in a range which does not represent a safety concern from a biophysical point of view. No changes to the programmed parameters of the PM or damage of PM components were observed neither In-vitro (n = 0/24) nor In-vivo (n = 0/63). Despite the strong magnetic field, the reed switch remained deactivated in 54 % (13/24) of the cases during In-vitro simulated MRI exams of the brain. All patient studies (n = 63/63) could be completed without any complications. Atrial and ventricular stimulation thresholds (expressed as pulse duration at 2-fold rheobase) did not change significantly immediately post-MRI nor in the 3 months follow-up (pre-MRI: 0.17 ms +/- 0.13 ms, post-MRI: 0.18 ms +/- 0.14 ms, 3 months follow-up: 0.17 ms +/- 0.12 ms). CONCLUSION: MRI of the brain at 1.5 Tesla can be safely performed in carefully selected clinical circumstances when appropriate strategies are used (re-programming the PM to an asynchronous mode, continuous monitoring of ECG and pulse oximetry, limiting the SAR value of the MRI sequences, cardiological stand-by). Based on these studies, implanted PM should not longer be regarded as an absolute contraindication for MRI at 1.5 T.

Burns, Electric↗
PubMed2005

[CT coronary angiography in patients with atrial fibrillation].

PURPOSE: Reliable visualization of the coronary arteries with multislice spiral CT angiography (MSCTA) in patients with atrial fibrillation (AF) remains a challenge despite retrospective ECG gating. A recently developed new algorithm automatically compensates dynamic changes in the heart rate during the scan, thus reducing misregistration and motion artifacts. The HeartBeat-RT algorithm combines a fixed-percent delay determined from the first R wave and the fixed offset delay based on the second R wave in the ECG cycle. The purpose of this study was to find out the optimal reconstruction window in MSCTA in patients with AF for each of the three major coronary arteries during the cardiac cycle. MATERIALS AND METHODS: 20 patients with permanent AF were imaged on a 16-slice scanner (slice collimation: 16 x 0.75 mm; rotation time 0.42 s; 140 kV; 380 mAs; 120 ml Ultravist 370 (R) i.v.). The patients had not received any previous drugs for heart frequency regulation. Acquisition was started after bolus tracking of a biphasic bolus of 120 ml Ultravist 370 injected intravenously. Each coronary segment was reconstructed at 0 % - 90 % of the cardiac cycle in increments of 10 %. For image analysis we used coronary segments as defined by the American Heart Association. Two blinded independent readers assessed the image quality in terms of visibility and artifacts (five-point rating scale 1 = very poor, 2 = poor, 3 = fair, 4 = good and 5 = excellent) and the degree of stenosis (five-point rating scale 1 = 0 %, 2 = 1 % - 49 %, 3 = 50 % - 74 %, 4 = 75 % - 99 %, 5 = 100 %) on axial slices, multiplanar reconstructions and three-dimensional volume-rendered images. RESULTS: The heart rate during examination ranged between 42 and 156 beats per minute, the average heart rate was 78 +/- 23. Each of the two readers evaluated 300 segments in 20 patients. Visualization of all coronary artery segments was superior at 40 % (mean score of the image quality 2.79) as compared to the standard diastolic reconstruction window at 80 % (image quality 2.33). The second best image quality (2.57) was acquired at 0 % of the cardiac cycle. CONCLUSION: The use of a frequency adapted delay algorithm with the choice of an end-systolic reconstruction window provided diagnostically valuable images in patients with AF.

Aged↗
PubMed2005

[Radiologic features of inflammatory pseudotumors].

Inflammatory pseudotumor is a rare benign tumor entity. Because inflammatory pseudotumors mimic malignant tumors both clinically and radiologically, the radiologist should be familiar with this entity. Inflammatory pseudotumor most commonly involves the lung and the orbit, but it has been reported to occur in nearly every site in the body. For making a definite diagnosis a biopsy is often essential. The treatment options are varied and consist of surgery, high-dose steroids, irradiation, and chemotherapeutics.

Adult↗
PubMed2005

[Long-term fate of left atrial thrombi and incidence of cerebral embolism under continuous anticoagulation therapy].

PURPOSE: Patients (pts.) with atrial fibrillation (AF) and atrial thrombi are known to have an increased risk for cerebral embolism. However, little is known about the clinical course of atrial thrombi and the incidence of cerebral embolism in those patients during anticoagulation therapy. The high sensitivity of MR imaging (MRI) including diffusion-weighted imaging (DWI) suggests that this technique could provide an improved estimate of cerebral embolism associated with the presence of left atrial thrombi. The aims of this prospective study were to evaluate 1) the prevalence of clinically silent and apparent cerebral embolism in pts. with newly diagnosed AF and atrial thrombi using MRI/DWI, 2) the long-term fate of atrial thrombi under continues anticoagulation therapy and 3) the incidence of cerebral embolism during a follow-up period of 12 months with continuous anticoagulation therapy. MATERIALS AND METHODS: The study group consisted of 32 pts. with 1) newly diagnosed AF and evidence of left atrial (LA) thrombi detected by TEE and 2) a new start of anticoagulation therapy [International Normalized Ratio (INR) 2.0 - 3.0]. 19 pts. with 1) newly diagnosed AF and no evidence of atrial thrombi and 2) an equivalent anticoagulation regimen served as the control group. In both groups a) MRI/DWI studies of the brain (weeks 0, 4, 8, 12, 20, 28, 36, 44, and 52), b) transesophageal echocardiographic studies (TEE) for assessment of LA-Thrombi (weeks 0 and 52) and c) clinical neurological assessments (weeks 0, 20 and 52) were performed. RESULTS: In the study group (AF and LA-Thrombi) 11 out of 32 pts. (34 %) displayed signs of acute (n = 8) or chronic (n = 3) cerebral embolism in the initial MRI studies. In 4 out of 32 pts. (13 %), MRI/DWI depicted new or additional cerebral emboli (n = 12) during the follow-up period despite continuous anticoagulation therapy. 2 (n = 2/4; 50 %) of these patients had clinically apparent neurological deficits. In the control group 1 out of 19 pts. (5 %) showed evidence of chronic cerebral embolism as assessed by MRI/DWI at the beginning of the study (week 0). No embolic cerebral lesions were detected during the 12-month follow-up. Within 12 months only 63 % (n = 20/32) of LA thrombi in the study group resolved completely under anticoagulation. CONCLUSION: 1. The incidence of clinically inapparent cerebral emboli in pts. with newly diagnosed AF and atrial thrombi is much higher than the incidence of clinically apparent emboli and has been underestimated in the past. 2. New cerebral embolism may occur even with continued effective anticoagulation therapy in 13 % of pts. 3. Only 63 % of atrial thrombi resolve completely within 12 months under anticoagulation therapy.

Aged↗
PubMed2004

Intraperitoneal and intraluminal microdialysis in the detection of experimental regional intestinal ischaemia.

BACKGROUND: The aim was to investigate the possibility of using intraluminal or intraperitoneal microdialysis to monitor regional intestinal ischaemia. METHODS: Microdialysis catheters were inserted in the lumen, in and outside the intestinal wall, and in the peritoneum of each of ten pigs. Regional occlusive ischaemia was induced in 100 cm of jejunum. Levels of glucose, pyruvate, lactate and glycerol in the microdialysate were measured at 20-min intervals before and after induction of ischaemia. Systemic haemodynamics were monitored and laser Doppler flowmetry (LDF) recordings made in each of the intestinal segments. RESULTS: Ischaemia caused a significant decrease in glucose level, and an increase in lactate and glycerol concentrations and lactate/pyruvate ratio, at all catheters, although glucose could not be detected by the intraluminal catheter. The metabolic changes occurred simultaneously and were statistically significant in almost all catheters after 100 min. LDF revealed a significant decrease in intestinal blood flow, but there was considerable individual variation. CONCLUSION: Regional occlusive ischaemia in 100 cm of small intestine could be detected and monitored by means of a microdialysis catheter placed in the peritoneal cavity or the bowel lumen.

Animals↗
PubMed2004

Colonic obstruction caused by adhesive splenomegaly: report of a case.

INTRODUCTION: Splenomegaly caused by hematologic or infectious diseases is a well-known complication that may cause discomfort because of increased intra-abdominal pressure; however, complete obstruction of the large bowel usually never occurs. METHODS: We present a case of a 76-year-old male with polycythemia vera admitted with symptoms of complete colonic obstruction. At operation, the descending colon was found to be completely obstructed by a large adhesive spleen. Incision of the adhesions, complete colonoscopy, and mobilization of the colon was performed. RESULTS: Afterward, the patient had a normal colonic function; however, four days later he had a magnetic resonance-confirmed cerebral thrombosis followed by an episode of aspiration pneumonia, which he died of ten days after the operation. CONCLUSIONS: Colonic obstruction caused by splenomegaly is extremely rare, but may happen in patients with hematologic diseases.

Aged↗
PubMed2004

[High field MR imaging: magnetic field interactions of aneurysm clips, coronary artery stents and iliac artery stents with a 3.0 Tesla MR system].

PURPOSE: To evaluate magnetic field interactions of commonly used biomedical implants at 3.0 Tesla. MATERIALS AND METHODS: Fourteen aneurysm clips designed for permanent placement in intracranial aneurysms, 19 coronary artery stents and 20 iliac artery stents were evaluated in an actively shielded compact 3.0 T MR system (Intera, Philips Medical Systems, Best, The Netherlands, length of magnet 1.57 m). The magnetic deflection forces (translational movement) were evaluated as follows: The implants were suspended by a fine string and placed in the magnet bore at the location of the maximum magnetic field gradient. The translational forces F (z) were calculated from the measured angle of deflection from the vertical axis. The magnetic field-induced torque (rotational forces) was evaluated as follows: Each implant was placed in the center of the magnetic bore parallel to the static magnetic field B0 (position 0 degrees ). Any possible displacement of the implant was noted on a millimeter scale and any torque qualitatively evaluated using a 5 point grading scale (0: no torque; + 4: very strong torque). The implant was turned in steps of 45 degrees, and the procedure was repeated to encompass a full 360 degrees rotation. RESULTS: In 52 of the 53 devices tested, the deflection force (deflection angle: range 0-21 degrees, translational force: range 0-3.8 mN) was less than the gravitational force (i.e., the implant's weight). These devices (n = 52/53) did not show any alignment to or rotation in the magnetic field at any of the various 45 degrees -increment positions corresponding to a qualitative torque evaluation of grade 0/4. One device (n = 1/53), an iliac artery stent made of stainless steel (Zenith, Cook, Mönchengladbach, BRD), was found to have deflection forces (deflection angle 88 degrees translational force 299 mN) greatly exceeding the gravitational force as well as a pronounced torque (grade 4/4). CONCLUSION: Out of 53 biomedical implants evaluated for magnetic field interactions at 3.0 T, one iliac artery stent made of stainless steel was found to be potentially unsafe based on ASTM criteria. MR imaging at 3.0 Tesla may be performed safely in patients with any of the other 52 different implants evaluated in this study with respect to magnetic field translational attraction and torque.

Alloys↗
PubMed2004

[The value of applying nitroglycerin in 3D coronary MR angiographie with real-time navigation technique].

PURPOSE: Nitroglycerin administration results in dilation of epicardial coronary vessels and in an increase in coronary blood flow, and has been suggested to improve MR coronary angiography. This study evaluates systematically whether administration of nitroglycerin improves the visualization of coronary arteries and, as a result, the detection of coronary artery stenosis during free breathing 3D coronary MR angiography. MATERIALS AND METHODS: Coronary MR angiography was performed in 44 patients with suspected coronary artery disease at a 1.5 Tesla System (Intera, Philips Medical Systems) (a) with and (b) without continuous administration of intravenous nitroglycerin at a dose rate of 2.5 mg/h, using an ECG gated gradient echo sequence with real-time navigator correction (turbo field echo, in-plane resolution 0.70 x 0.79 mm(2), acquisition window 80 ms). Equivalent segments of the coronary arteries in the sequences with and without nitroglycerin were evaluated for visualized vessel length and diameter, qualitative assessment of visualization using a four point grading scale and detection of stenoses > 50 %. Catheter coronary angiography was used as a gold-standard. RESULTS: No significant differences were found between scans with and without nitroglycerin as to average length of the contiguously visualized vessel length (p > 0.05) and diameter (p > 0.05). There was also no significant difference in the coronary MR angiography with and without nitroglycerin in the average qualitative assessment score of the visualization of LM, proximal LAD, proximal CX, and proximal and distal RCA (2.1 +/- 0.8 and 2.2 +/- 0.7; p > 0.05). Sensitivity (77 % [17/22] vs. 82 % [18/22] p > 0.05) and specificity (72 % [13/18] vs. 72 % [13/18] p > 0.05) for the detection of coronary artery stenosis also did not differ significantly between scans with and without intravenous administration of nitroglycerin. CONCLUSION: Administration of nitroglycerin does not improve visualization of the coronary arteries and detection of coronary artery stenosis in free breathing 3D coronary MR angiography.

Coronary Angiography↗
PubMed2004

Validation of intramural intestinal microdialysis as a detector of intestinal ischaemia.

BACKGROUND: The purpose of this study was to validate intestinal microdialysis as a detector of intestinal ischaemia using measurements of glucose, lactate and glycerol from the jejunal wall. METHODS: Based on a previous study, the cut-off levels for the presence of regional intestinal ischaemia were defined for microdialysis glucose, lactate, glycerol and the lactate/glucose ratio. Changes of 60% in the metabolic compounds measured after 100 min were defined as the cut-off level for ischaemia. The cut-off levels were tested in a randomized, single-blinded study. Ten pigs were used; occlusive ischaemia was performed by clamping a segment of the mesentery to the intestine. Four catheters were inserted per pig, two in the ischaemic segment and two in the non-ischaemic segment. All catheters were numbered, randomly allocated and inserted in the intestine by the staff at the institute and unknown to the investigators. RESULTS: One pig was excluded because the clamping was insufficient. Technical problems with the catheters were registered in 15% of cases owing to damage of the microdialysis membrane, dislocation, or incorrect placement. The predictive values of presence of ischaemia for glucose, lactate, glycerol and the lactate/glucose ratio were: 0.91, 1,0.85 and 0.92, respectively. CONCLUSION: Using a 60% cut-off limit measured after 100 min, intestinal ischaemia can be detected and excluded using intestinal microdialysis, but some technical problems remain that need further investigation.

Animals↗
PubMed2002

Small bowel resection in the rat: the effect upon bone and mineral metabolism.

BACKGROUND AND AIMS: We analyzed bone and mineral metabolism after long-segment small bowel resection in the rat to detect functional and morphological alterations and to determine the development of osteopathy. METHODS: Twelve-week-old male Lewis rats were randomized into short (8-week) or long (16-week) follow-up groups. Sham operation, resection of the proximal third of the small bowel, resection of the distal third of the bowel and resection of the entire jejunum and ileum were carried out. Nineteen days before the end of the experiment the animals were transferred into a metabolic cage to analyze weight gain/loss, food intake, and fecal excretion/24 h. At the end of the experiment the animals were killed; blood samples and bowel and bone specimens were collected, length, weight, volume, density, mineral content, and fracturing energy were determined, and bone histology was examined. The calcium/phosphorus ratio, nonmineralized tissue content and the ratio fracturing energy/mean bone density were calculated. RESULTS: After 8 weeks there were significant differences to the control group in body weight, weight gain, food efficiency, femur length, weight, volume, mineral content, mineral density, fracturing energy per bone volume, and bone density but not in bone calcium or magnesium. After 16 weeks there were differences in body weight, weight gain, food efficiency, femur length, weight, volume, bone mineral content and density, bone minerals, and nonmineralized tissue but not in fracturing energy; the average values of all these parameters were lower in the resected groups, and lowest in the group after resection of the entire jejunum and ileum. Bone histology showed a reduction in trabecular bone mass after long-segment small bowel resection. CONCLUSIONS: Long-segment small bowel resection causes a significant loss of body weight despite of a comparable mean chow ingestion resulting in a significant decreased food efficiency. We conclude that there is no inverse relationship of bone calcium content and the fracture risk, and that there is no severe mineralization defect after long-segment small bowel resection.

Animals↗