Search PubMed⌕ Search

Biomedical subjects

T Pfammatter

Publications and source records attributed to T Pfammatter.

At least 55 records · Page 3Linked to original sources
PubMed1999

Magnetic resonance angiography versus duplex sonography for diagnosing renovascular disease.

Noninvasive testing for renovascular disease is required to identify patients who may benefit from revascularization procedures without exposing an unnecessary amount of patients to the risks of catheter angiography. All available methods of diagnosing renal artery stenosis have significant limitations. We compared a new technique, contrast-enhanced magnetic resonance angiography, with an established technique, duplex ultrasonography, for the detection of renal artery stenosis using catheter angiography as the standard of reference. Eighty-nine patients with clinically suspected renovascular disease underwent duplex renal scanning and contrast-enhanced magnetic resonance angiography. Sixty of these also underwent catheter angiography. All studies were interpreted for the presence of renal artery stenosis blinded to the results of the other imaging modalities. For detection of hemodynamically significant (>/=60% diameter reduction) main renal artery stenosis, sensitivity and specificity were 90% and 86%, respectively, for magnetic resonance angiography and 81% and 87% for duplex sonography. Most false readings involved differential grading of stenoses detected with all 3 techniques. When patients with fibromuscular dysplasia were excluded from the analysis, the sensitivity of magnetic resonance angiography increased to 97%, with a negative predictive value of 98%. Magnetic resonance angiography detected 96% and duplex 5% of accessory renal arteries seen at catheter angiography. Contrast-enhanced magnetic resonance angiography is a useful technique for diagnosing atherosclerotic renovascular disease. It overcomes the major limitations of duplex renal scanning. However, duplex has the advantage of providing hemodynamic information and appears better suited for the assessment of patients with suspected fibromuscular dysplasia.

Adult↗
PubMed1998

[Clinical use of contrast-enhanced MR angiography].

Compared to other non-invasive MR-angiography techniques, contrast-enhanced MR angiography is a robust imaging technique in the assessment of the arterial vascular system. This is due to the use of three-dimensional data acquisition, non-nephrotoxic paramagnetic contrast and short acquisition times. Clinical applications include the evaluation of the thoracic and abdominal arterial vessels. With the refinement of this technique also small peripheral arteries of the extremities can be imaged and an entire non-invasive diagnostic work-up of the peripheral arteries will be possible.

Contrast Media↗
PubMed1998

[The MRT and MRA of kidney transplants--vascular and perfusion assessment].

PURPOSE: To document the value of fast contrast enhanced-sequences in the assessment of the vascular supply and parenchymal perfusion in renal transplants. PATIENTS: 18 recipients of a renal transplant were examined with a 1.5-tesla-MR-system. The protocol included fast contrast enhanced 3D MR angiography and coronal 2D GRE sequences. The transplant artery and vein were assessed as well as regional parenchymal perfusion. RESULTS: 3D MRA detected three transplant artery stenoses and one occlusion. In addition, two renal vein thromboses and one compression were identified. Perfusion deficits were documented in 8 renal transplants: renal infarction (n = 4), cortical necrosis (n = 2), acute tubular necrosis (n = 1) and venous ischemia (n = 1). Fluid collections were documented as well as dilation of the collecting system and abnormalities of the surrounding tissues. CONCLUSION: Contrast enhanced MRI and MRA permit a comprehensive assessment of renal transplants without inducing nephrotoxicity.

Adult↗
PubMed1998

Contrast-enhanced magnetic resonance angiography of the renal arteries. Original investigation.

RATIONALE AND OBJECTIVES: The authors determine the value of contrast-enhanced, three-dimensional (3D) magnetic resonance angiography (MRA) in the assessment of the renal arteries in comparison with conventional arteriography (CA). METHODS: One hundred three patients (71 m, 32 f) were evaluated with both CA and 3D MRA. The 3D MRA data set consisted of 44 contiguous sections, acquired in apnea (23-28 seconds) using the following parameters: TR/TE 3.9/1.5 milliseconds, flip angle 40 degrees to 50 degrees, 3/4 k-space acquisition. A bolus of 0.3 mmol/kg BW gadolinium-DTPA was administered intravenously, using an automated injector. A test bolus method was used for timing of the bolus relative to the beginning of the data acquisition. Intra-arterial CA was used as the standard of reference in all patients. Separate interpretations of the CA and MRA results were made by two different pairs of radiologists, who were each blinded to the results of the other exam. RESULTS: In all, 31 of 33 accessory renal arteries were correctly identified. All 205 main renal arteries were seen with MRA. Of 65 significant stenoses identified on CA, 61 were correctly identified and graded by MRA. Sensitivity and specificity values for the assessment of significant renal arterial lesions were 93% and 90%, respectively. CONCLUSIONS: Breath-hold, contrast-enhanced 3D MRA allows for the reliable assessment of renal arterial morphology and pathologic states.

Aged↗
PubMed1998

Transcaval biopsy of retroperitoneal fibrosis.

An additional use of the transjugular hepatic Tru-cut biopsy needle is reported. A periaortic mass was biopsied with this device inserted through the femoral vein under fluoroscopy guidance. Based on the sampled tissue, a diagnosis of idiopathic retroperitoneal fibrosis was made. The procedure was well tolerated, and long-term follow-up confirmed the diagnosis. Transcaval retroperitoneal biopsy may represent an alternative to surgical biopsy of diffuse retroperitoneal disease in high operative-risk patients.

Adult↗
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

In situ repair of aortobronchial, aortoesophageal, and aortoenteric fistulae with cryopreserved aortic homografts.

PURPOSE: The surgical treatment of fistulae that originate from aortic aneurysms or prosthetic aortic grafts carries a high mortality rate. We investigated whether in situ repair with cryopreserved aortic homografts would improve the outcome. METHODS: Between April 1994 and June 1996, 11 patients (mean age, 62 +/- 10 years) with aortobronchial, aortoesophageal, or aortointestinal fistulae originating from mycotic aneurysms (five of 12) or prosthetic aortic grafts (six of 12) underwent in situ replacement of the thoracic (seven of 10) or abdominal (four of 10) aorta with homografts. Emergency surgery was performed in eight of 11 patients (73%). RESULTS: The hospital mortality rate was 9%; there was one sudden cardiac death on the seventh postoperative day. The mean hospital stay was 42 +/- 26 days (range, 21 to 90 days). After surgery, antibiotics were given for 38 +/- 6 days (range, 28 to 42 days). Neither reinfection, suture line rupture, nor anastomotic aneurysms were observed by magnetic resonance angiography, computed tomography, angiography, or transesophageal echocardiography after 14.3 +/- 8.2 months (range, 6 to 31 months). In one patient, percutaneous vascular stent placement was necessary after 18 months for an anastomotic stenosis of a thoracic homograft. CONCLUSIONS: In situ repair with cryopreserved aortic homografts seems to be a promising step in the treatment of aortobronchial, aortoesophageal, and aortointestinal fistulae. This technique has a low operative mortality rate and may prevent reinfection.

Aged↗
PubMed1997

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

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

Adult↗
PubMed1997

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

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

Angiography, Digital Subtraction↗
PubMed1997

Suprahepatic caval anastomotic stenosis complicating orthotopic liver transplantation: treatment with percutaneous transluminal angioplasty, Wallstent placement, or both.

OBJECTIVE: Our objective was to evaluate, over a 5-year period, the nonsurgical treatment of three patients with suprahepatic caval anastomotic stenosis who had undergone orthotopic liver transplantation. CONCLUSION: Balloon angioplasty is a safe and effective method for treating chronic caval stenosis occurring in patients who have undergone orthotopic liver transplantation. Caval stenosis identified in the early postoperative period, especially when such stenosis is associated with caval torsion or kinking, may be effectively treated by stent placement.

Adult↗
PubMed1997

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

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

Aged↗
PubMed1996

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

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

Adult↗
PubMed1996

A simple MR-compatible infusion pump.

A simple, mechanical infusion pump that employs a constant force, nonferromagnetic spring to squeeze a syringe is described. The contrast infusion rate is determined by the spring force, gadolinium solution viscosity, and the resistance of either a user-selected needle or a precision oriffice according to Poiseuille's Law or the Bernoulli effect. Its use in dynamic, gadolinium-enhanced 3D MR angiography is described.

Contrast Media↗