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Biomedical subjects

G Friedmann

Publications and source records attributed to G Friedmann.

At least 19 recordsLinked to original sources
PubMed1992

In vivo imaging of glucose consumption and lactate concentration in human gliomas.

Twenty patients with histologically confirmed gliomas were studied with positron emission tomography (PET) and proton magnetic resonance spectroscopy (1H-MRS). PET with 18F-2-fluoro-2-deoxy-D-glucose (FDG) provided tomograms of the metabolic rate of glucose. MRS images were obtained by combining volume-selective excitation with phase-encoded acquisition. With 32 x 32 gradient phase-encoding steps, an in-plane resolution of 7 x 7 mm was achieved. From this set of spectra, lactate maps were created and compared with PET maps of glucose metabolism. Maximum glucose metabolic rates within tumors (relative to metabolic rates of glucose in contralateral regions of the brain) were correlated significantly with maximum lactate concentrations (relative to N-acetyl aspartate peaks in the contralateral part of the brain). In 8 tumors, no lactate was detected, and in 7 of these the maximum glucose metabolic rate was below the median value. The tumor with the highest lactate concentration also had the highest glucose metabolic rate. The topographic relation between glucose metabolic rate and lactate concentration could be analyzed in 9 patients by three-dimensional alignment of the PET and MRS images. In that analysis, maximum lactate concentrations were often not found in the same location as maximum glucose metabolism, but lactate tended to accumulate in tumor cysts, necrotic areas, and the vicinity of the lateral ventricles. The combination of FDG PET and 1H-MRS imaging demonstrates details of the spatial relation between the two poles of nonoxidative glycolysis, glucose uptake and lactate deposition.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[Experimental studies on magnetic resonance tomographic and magnetic resonance angiographic imaging of poststenotic flow patterns].

A phantom has been developed, which permits the perfusion of defined stenosis with variable flow rates. The post-stenotic flow patterns were imaged by means of conventional MRI sequences and special angiographic sequences using a 1.5 total body scanner (Gyroscan S15, Philips). For conventional MRI images, spin-echo-sequences (TR 500 ms, TE 27 ms with reconstruction of the magnitude and phase images) and gradient-echo-sequences (TR 60 ms, TE 27 ms, flip angle 15 degrees with reconstruction of the magnitude images) were used. For MR angiography 2D inflow (multiple-single-slice-technique, TR 40 ms, TE 14 ms, flip angle 60 degrees) and flow-adjusted-gradient-sequences (TR 24 ms, TE 10 ms, flip angle 60 degrees) were performed. In addition to an analysis of the appearances, the length of the changed signal intensity beyond the stenosis was evaluated. For constant flow rates it increases with the severity of the stenosis. For a constant stenosis the length of the post-stenotic signal change alters with flow rate. The changes also depend on the direction of flow and the gradients of the chosen sequences. The comparison of magnitude and phase images allows the discrimination between turbulent and non-turbulent flow. It therefore appears possible to estimate the severity of arteriosclerotic occlusive disease by means of MRI in the future.

Blood Flow Velocity↗
PubMed1992

Human brain tumors: spectral patterns detected with localized H-1 MR spectroscopy.

Image-guided localized proton magnetic resonance (MR) spectroscopy of intracranial tumors was performed to correlate spectral patterns and histologic findings. Thirty-six patients were examined prior to any specific treatment. Evaluation based on signal intensity ratios showed that all tumor spectra differed from spectra of healthy brain tissue. Ratios of creatine to choline-containing compounds (Cr/Cho) and nitrogen acetyl-aspartate to Cho (NAA/Cho) were reduced significantly in all tumor spectra compared with spectra of normal tissue in contralateral brain hemispheres (P less than .005). Noncerebral tumors typically showed a vanishing or missing NAA signal, strongly reduced Cr signal, and additional signals, assigned to alanine in meningiomas and lipids in metastases. In contrast, 11 gliomas of grades 2 and 3 exhibited NAA/Cho ratios and Cr/Cho ratios that were less than normal but that were significantly larger (P less than .01) than corresponding values in eight meningiomas. Ten glioblastomas displayed spectra with various signal ratios, so no significant differences between them and other tumor types could be established. In nine gliomas a clearly detectable lactate signal was present. However, no direct correlation between lactate level and histologic tumor grading was found.

Adult↗
PubMed1991

[Aortobronchial fistulae as late complications following the surgical correction of aortic isthmus stenosis].

Three patients (2 men, aged 39 and 52 years, one woman, aged 47 years) developed hemoptysis 3-19 years after surgical resection of coarctation of the aorta. Digital subtraction angiography in the two men was suspicious of an aortobronchial fistula. An emergency thoracotomy revealed the diagnosis in the woman: she died during the operation of intractable arterial bleeding, the initial operation having been atypical (insertion of a graft extending across the isthmus to the ascending aorta). The 52-year-old man died of left heart failure after pneumonectomy (for massive bleeding into the left lung). An aneurysm sack at the aortic isthmus was resected and a vascular graft implanted in the 39-year-old man. There have been no further hemoptyses. These cases emphasize the need for including aortobronchial fistula as a cause of hemoptysis.

Adult↗
PubMed1991

[Conventional and cine-MRT in patients with aneurysms of the abdominal aorta].

We studied 40 patients with aneurysms of the abdominal aorta by MRI. These results were compared with those obtained by real-time sonography (n = 40), angiography (n = 32) and CT (n = 16). In 30 patients the imaging results were compared--as far as possible--with the operative findings. MRI proved more reliable, especially if compared with sonography, in evaluating renal or iliac artery involvement. Mural thrombi were detected more often (93%) by MRI than by CT (85%) or sonography (83%). Cine-MRI showed strong turbulences in 33%. Turbulences did not correlate with the size of the aneurysm.

Adult↗
PubMed1991

[Balloon-expandable stents in arterial changes of the iliac arteries. Early and follow-up results of 65 interventions].

69 balloon-expandable vascular endoprostheses (Palmaz stents) were placed in 65 iliac arteries of 57 patients. The indications for stent placement were total occlusions (n = 15), restenosis after PTA (n = 13), dissections (n = 4), post-operative strictures (n = 3) or others (n = 30). The peak systolic pressure gradient dropped from 43.9 to 2.9, the mean pressure gradient to 1.9 mmHg after stent placement. This was significantly lower than conventional PTA (residual peak systolic pressure gradient: 5.8). Complications occurred in 7.7% of all interventions. 78.4% of the patients showed no limiting claudication after stent placement. Angiographic controls after 47 weeks demonstrated an average intima proliferation of 0.4 mm, not leading to significant restenosis. Cumulative patency after 16 months was 96%. Iliac stents became an effective and in certain situations indispensable adjuvant to PTA.

Adult↗
PubMed1991

[Stents in iliac vascular changes].

The results of 79 iliac stent placements in 64 patients are reported. The technical success rate was 96%. The systolic pressure gradient dropped from 44 mmHg before to 2.8 mmHg after stent placement. This differed significantly as compared to a group treated by conventional PTA (gradient 5.8 mmHg). The cumulative patency after 18-20 months was 90%. Angiographic controls up to 19 months after "stenting" demonstrated only one secondary stent occlusion. Iliac stents therefore are a very valuable supplement to classic PTA.

Angioplasty, Balloon↗
PubMed1991

[Techniques, results and risks of chemoembolization of malignant liver tumors].

This is a report on 55 chemoembolizations (ChE) in 31 patients with primary (n = 10) and secondary (n = 21) liver malignomas. Probing of the segmental arteries was always possible by means of a coaxially placed 3F catheter system. Chemoembolization was effected with a mixture of ivalon particles, 20 mg mitomycin or 40-60 mg epirubicin and an ethibloc solution. More than 75% of the patients showed a decrease in tumour size and/or tumour density. The proportion of surviving patients was 80.6% after 6 months. Within this period, extrahepatic metastases were seen for the first time in 19.4% of the patients. References in literature on techniques and results of chemoembolization are discussed.

Adult↗
PubMed1990

Metabolic imaging of patients with intracranial tumors: H-1 MR spectroscopic imaging and PET.

Hydrogen-1 magnetic resonance (MR) spectroscopic images of patients with intracranial tumors were obtained. Metabolite maps of N-acetyl aspartate, choline, lactate, and creatine concentrations were reconstructed with a nominal spatial resolution of 7 mm and a section thickness of 25 mm. The metabolite maps showed variations in metabolite concentrations across the tumor. In one patient, it was observed that choline concentration was increased in one part of the tumor but decreased in another part. In another patient, the concentration of N-acetyl aspartate was extremely low in one part of the tumor but only slightly increased in another part of the tumor. Lactate was observed in all patients. In one patient, a combined measurement made with positron emission tomography (PET) and MR spectroscopic imaging was performed. This demonstrated that increased lactate concentration measured with H-1 MR spectroscopic imaging corresponded topographically with increased glucose uptake measured with fluorine-18 fluoro-2-deoxyglucose PET. Combined MR spectroscopic and PET measurements provide an opportunity to investigate, in greater detail than before, glucose uptake and catabolism by intracranial tumors.

Adult↗
PubMed1990

Positron emission tomography of fluorine-18-deoxyglucose and image-guided phosphorus-31 magnetic resonance spectroscopy in brain tumors.

Positron emission tomography (PET) of 2(18F)-fluoro-2-deoxy-D-glucose (FDG) and volume-selective phosphorus-31 magnetic resonance spectroscopy (31P-MRS) are methods used to assess the energy metabolism of the brain. Both methods were studied with respect to their contribution to differential diagnosis in 23 patients with various brain tumors. The various neuroectodermal tumors differed with respect to their metabolic rate for glucose (MRGL). Benign and malignant tumors could be better differentiated by using tumor metabolism relative to contralateral brain and by evaluating heterogeneities in tumors. Low-grade gliomas usually showed normal 31P-MR spectra; high-grade gliomas were characterized by reduced and often split phosphodiester peaks and alkaline pH. Meningiomas, which had variable MRGL, typically showed extremely low phosphocreatine levels, reduced phosphodiesters, and alkaline pH. We concluded that FDG-PET and 31P-MRS examine different aspects of tumor metabolism. Therefore, both can contribute independently and complementarily to the differential diagnosis of brain tumors.

Astrocytoma↗
PubMed1990

[Clinical value of new rapid nuclear magnetic resonance tomography in preoperative assessment of hypernephroma. A prospective comparative study of CT and MR].

The new technique of rapid magnetic resonance imaging (MRI) with a paramagnetic contrast agent provides excellent imaging of the kidneys and their lesions. MR imaging of this anatomical region at short breath holding intervals matches the well-known quality of computed tomography (CT) for the first time. MR and CT studies were performed on 36 patients with proven renal cell carcinoma. Different investigators evaluated the staging of the tumor by means of both techniques in a prospective study. In all patients a radical nephrectomy was performed. Surgical and pathological findings were compared. Though little difference was found in diagnostic value between the two systems, MRI results concerning the T-stage were better. Venous invasion was clearly shown by MRI without the use of contrast medium. Furthermore, sagittal and transaxial images provided a more direct assessment of the extent of the tumor and its demarcation to healthy parenchyma. Thus, MRI is helpful in planning of the surgical approach when organ-sparing excision of renal tumors is to be performed.

Adrenalectomy↗
PubMed1989

[A comparison of digital luminescence radiography and conventional radiodiagnosis in sialography].

In 25 patients sialographies were obtained by both conventional film-screen system combinations and computed radiography (CR), the digital exposure dose being 50% of the conventional one. In CR two differently post processed images were obtained from one x-ray exposure: one "conventionally" processed image resembling a conventional film-screen system combination and a complementary "enhanced" image showing a higher edge enhancement at the same spatial resolution. CR proved to be equivalent to conventional radiography despite the reduction in exposure dose. Using high edge enhancement the peripheral glandular ducts as well as the central ducts superimposed by bony structures were optically accentuated. However, diagnostical information exceeding the conventional film-screen system combination was not obtained by CR. Artefacts by post processing procedures relevant for diagnosis were not observed.

Adenoma↗
PubMed1989

Adrenal masses: evaluation with fast gradient-echo MR imaging and Gd-DTPA-enhanced dynamic studies.

Fast gradient-echo magnetic resonance (MR) imaging of 38 adrenal masses with proved diagnosis was performed during suspended respiration with various repetition times (TRs), echo times (TEs), and flip angles. Dynamic perfusion studies after gadolinium diethylenetriamine-pentaacetic acid (DTPA) administration were performed by repeated imaging at short time intervals. With more T2 weighting (TR = 60 msec, TE = 30 msec, and flip angle = 15 degrees), malignant tumors and pheochromocytomas had a significantly higher relative signal intensity than adenomas; overlap of signal intensity led to equivocal findings in nine cases. After administration of Gd-DTPA, adenomas showed only mild enhancement and quick washout; malignant tumors and pheochromocytomas showed strong enhancement and slower washout. Five of the nine cases that were equivocal in precontrast images could thus be correctly classified. In addition to this improved classification of adrenal masses, fast, dynamic contrast material-enhanced MR imaging resulted in a reduction in total examination time.

Adenoma↗
PubMed1989

[Renal artery stenosis: possibilities of magnetic resonance tomography].

Non-invasive detection of stenotic lesions of the renal arteries remains an important clinical problem. Recent advances in magnetic resonance angiography represent a significant progress towards achieving non-invasive diagnosis of vascular diseases. The purpose of this study was to evaluate the possibilities of assessment of renal artery stenosis with commonly available hard- and software equipment. Imaging of renal arteries was performed with a ECG-gated fast multiphase gradient echo sequence which allows production of a series of images in different heart phases. Examinations were performed in 15 healthy volunteers and in 12 patients with angiographically verified renal artery stenosis. In 10 patients additional dynamic studies with fast imaging during short breath-holding periods after administration of gadolinium-DTPA served for the assessment of renal perfusion. A superconducting system operating at 1.5 T was used to produce gradient echo sequences with small flip angles and dephasing gradients of constant amplitude. To find the optimal imaging method for depiction of the renal arteries the following parameters were systematically varied: respiratory gating, resolution, number of excitations, slice thickness, phase encoding direction, rephasing gradients, flip angle and echo time. A good visualization of the vessels was always possible and using the best parameter combination even the narrowed lumen could be assessed in some cases. With this technique or with gadolinium-enhanced dynamic studies the perfusion of the kidneys can be demonstrated. However, quantitation of the stenosis or quantitation of renal perfusion was not possible; even the depiction of the stenotic lesion was successful only in half of the cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

[Extracranial congenital arteriovenous fistula in a newborn infant].

A child with a congenital arteriovenous fistula between the arteria carotis externa and sinus sigmoideus is presented. This case showed further complications by the development of congestive heart failure and a Kasabach-Merritt syndrome. By an early excision already in the neonate age after diagnosis by digital subtraction angiography, the child could be saved.

Carotid Artery, External↗
PubMed1988

[Diagnosis of recurrent rectal cancer: Comparison of CT and MR].

For the assessment of local recurrence after surgical treatment of rectal carcinoma the results of MR and CT examinations in 29 patients were analyzed. Diagnosis was confirmed by surgery, by multiple biopsies and by follow-up examinations. CT yielded in only 11 cases clearly positive or negative findings. There were 4 false positive and 2 false negative results; in 12 cases the diagnosis remained uncertain. On the other hand, a clear differentiation was possible by MR in 23 cases with characteristically prolonged T2 in recurrent tumour and low signal intensities in fibrosis. Difficulties in differentiation were found only in early fibrotic reactions after surgery, inflammation or radiotherapy and in rare fibrotic tumours.

Adult↗