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Biomedical subjects

W Grodd

Publications and source records attributed to W Grodd.

124 records · Page 7Linked to original sources
PubMed1986

Gd-DTPA contrast enhancement and tissue differentiation in MR imaging of experimental breast carcinoma.

Gadolinium-DTPA (Gd-DTPA) enhancement of magnetic resonance (MR) imaging was tested for diagnostic utility in evaluating carcinoma. Human breast carcinoma implanted in ten nude mice was studied before and after injection of Gd-DTPA at two different doses (0.2 and 0.5 mmol/kg body weight). Before injection, all tumors appeared homogeneous in intensity on spin-echo images; after injection, it was possible to distinguish areas of strong enhancement from areas of weak enhancement. Histologic correlations showed that the strongly enhanced areas corresponded to richly vascularized connective tissue and apparently viable tumoral tissues, while the weakly enhanced areas corresponded to nonvascularized necrotic tissue. The results indicate that intravenously administered paramagnetic agents such as Gd-DTPA may improve the specificity and diagnostic accuracy of MR imaging by permitting better differentiation of tumor elements.

Adult↗
PubMed1986

The diagnostic value of renal cortex-to-medulla contrast on magnetic resonance images.

The diagnostic value of magnetic resonance contrast between the renal cortex and renal medulla as an indicator of renal disease was retrospectively studied in 38 patients (ten patients with a variety of diseases affecting the renal parenchyma, nine with renal obstruction, four with diffusely infiltrating renal-cell carcinoma, one with renal hematoma, nine with normally functioning renal allograft, and five with renal allograft failure). Twelve normal volunteers served as controls. On spin-echo (SE) images (TR 0.5 sec, TE 28 msec), the cortex-to-medulla contrast was present in the kidneys of all the normal volunteers (19% contrast +/- 2% S.D.) and in all the normally functioning allografts (17% contrast +/- 2% S.D.). Decrease or absence of cortex-to-medulla contrast (SE image with TR 0.5 sec and TE 28 msec) was found to be a sensitive but nonspecific sign of renal disease. It occurred in renal diseases of various causes and was produced by different pathophysiologic mechanisms such as edema, scarring, and tissue replacement by neoplasm or hematoma. Of the calculated T1 and T2 relaxation times and spin density of the cortex and the medulla, the T1 changes most consistently reflected renal disease.

Adolescent↗
PubMed1986

[Radiation treatment of malignant testicular tumors--results, side effects, analysis of recurrences].

A retrospective study was conducted in order to investigate the radiotherapeutic results of 123 patients with testicle tumors. The overall five-year survival rate was 85% out of 75 patients suffering from seminoma and 70% out of 48 patients suffering from teratoma. Recurrences as well as complications are analyzed in detail. The authors underline the necessity of an adaption of radiotherapy to the individual stage comprising the complete regional lymph node regions.

Adolescent↗
PubMed1985

[Nuclear spin tomographic studies in liver diseases].

Various diseases of the liver were studied by nuclear resonance tomography using a supra-conductive magnet, with 0.5 T field strength, and the value of the method for the diagnosis of these conditions has been studied. MR tomography is superior to CT for differentiating between solid and fluid lesions, such as haemangiomas since, by choosing suitable techniques, high contrast can be achieved without enhancement. Most diffuse parenchymal diseases and heterogeneous malignant tumours show little change in relaxation times and therefore cannot be diagnosed with great sensitivity or specificity. Nuclear magnetic tomography cannot replace the sonographic, CT and nuclear medicine techniques used for examining the liver, but is a useful addition for special problems.

Carcinoma, Hepatocellular↗
PubMed1984

[Nuclear spin tomographic study of the facial skeleton. I. Nuclear spin and computed tomographic anatomy].

The resolution of NMR and CT was compared using axial sections of the normal anatomic structures of the facial skeleton. It was shown that NMR was superior in differentiating muscles, tonsils, mucosa, lymph nodes and blood vessels. The demonstration of bone and its differentiation from air-containing spaces is often difficult. Metallic, non-ferromagnetic dental fillings, which cause serious artefacts on CT, do not affect NMR.

Adult↗
PubMed1983

[Proton relaxation characteristics of human and animal tissue in vitro. Changes during autolysis and fixation].

The results of measurements of proton relaxation times of various tissues from rats, pigs and humans are reported; these were obtained by a resonance spectroscope at 20 MHz and 40 degrees C. There were specific differences in both relaxation times (T1 and T2) of the liver and spleen. There was a difference of more than 150 ms in the longitudinal relaxation time between grey and white cerebral tissue. Autolytic changes show an increase in both relaxation times. Fixation produced a reduction in T1 only. The significance of these findings for NMR tomography is discussed.

Animals↗
PubMedDate not supplied

Nonlinear excitation profiles for three-dimensional inflow MR angiography.

An RF excitation pulse for three-dimensional (3D) time-of-flight (TOF) MR angiography (MRA) with a nonlinear excitation profile was numerically calculated under the condition of uniform vessel signal across the excitation volume (slab), and the superiority of the optform pulse as compared with conventional RF pulses and TONE pulses was demonstrated. For this purpose we acquired MRA of the lower leg and of the carotid and vertebral arteries in a 30-year-old healthy volunteer. Although the flow velocity ranges in these two anatomic locations are different by about a factor of 10, in both cases the corresponding optform pulse provided the best signal homogeneity at the highest level.

Adult↗
PubMedDate not supplied

Assessment and therapy monitoring of Leigh disease by MRI and proton spectroscopy.

In a 2-year-old boy with Leigh disease, spasticity, dysarthria, and optic atrophy gradually developed. Computed tomography and magnetic resonance imaging disclosed progressive, symmetric basal ganglia lesions. In muscle tissue, a defect of pyruvate dehydrogenase complex was found. Magnetic resonance volume selective proton spectroscopy (MRVS) of the basal ganglia demonstrated an abnormal lactate peak. A ketonemic diet coincided with clinical stabilization and arrest of progressive brain lesions. Lactate could no longer be demonstrated by MRVS. It reappeared with a new brain lesion coinciding with discontinuation of the diet. MRVS, therefore, appears to be a sensitive tool to evaluate pathologic lactate production in metabolic brain disease with disturbed energy metabolism and allows noninvasive therapy monitoring.

Basal Ganglia↗
PubMedDate not supplied

Stroboscopic articulography using fast magnetic resonance imaging.

A method to display dynamic aspects of vocal tract configuration during speech production by means of fast magnetic resonance imaging is presented. Data acquisition during repetitive movement relies on a stroboscopy-like procedure. The time resolution achieved is 120 images s-1 in a selected plane. As compared with other techniques of kinematic measurements of speech motor processes, this procedure allows for visualization of the temporal and spatial coordination of all relevant articulators, e.g. the entire tongue, the velum and the lower vocal tract. As an example, the method was applied to repetitions of stop consonant-vowel-nasal syllables.

Adult↗
PubMedDate not supplied

Selective chemical imaging with a three-dimensional gradient echo sequence.

A combination of frequency selective excitation and saturation is used to separated water and fat components in magnetic resonance imaging. In conjunction with a gradient echo sequence (fast low angle) shot and a three-dimensional data acquisition, a large volume of the body can be covered. A set of 32 water or fat images can be obtained within 3.5 min using a repetition time of 50 ms and a 256 x 256 half Fourier space matrix. As no correction data or additional image calculations are necessary, the method can easily be applied to routine examinations.

Humans↗
PubMedDate not supplied

Comparison of ionic and non-ionic nitroxide spin labels for urographic enhancement in magnetic resonance imaging.

Two nitroxide spin labels (NSL) were compared for in vitro relaxivity and in normal rats for efficiency of urographic enhancement. One of the NSL, PCA, a pyrrolidinyl agent, was ionic and one, NAT, was a non-ionic pyrrolidinyl NSL with multiple hydroxyl substituents for water solubility. Using both NSLs the renal medulla and papilla were noted to show greater contrast enhancement than the cortex, with a maximum enhancing effect between 5 and 15 minutes. Using doses of 1.0 and 2.5 mmol/kg, more than 100 per cent increases in spin echo intensities above the baseline were observed. The lowest tested dose of 0.1 mmol/kg showed an easily detectable enhancing effect for NAT. The good contrast enhancing properties of NAT, considered together with its better acute tolerance, justifies further investigation of this non-ionic compound.

Animals↗
PubMedDate not supplied

Magnetic resonance imaging in small lesions of the central nervous system. Improvement by gadolinium-DTPA.

T1 values and T2 values (CPGM-sequence) of neurinomas and meningiomas were determined, and showed values close to those of white and grey matter or, in regressive cystic neurinomas, near the cerebrospinal fluid (CSF). By this overlapping in relaxation times, as well as by crossover and boundary effects, small tumors may be obscured. The application of gadolinium-DTPA allows easier identification even of small lesions, by the high contrast achieved on the T1 weighted imaging sequences, which also avoids crossover and boundary effects with the adjacent parenchyma and CSF. This is demonstrated in intrameatal acoustic neurinomas, vascular tumors, small and en plaque growing meningiomas, and tumors of the spinal canal.

Brain↗
PubMedDate not supplied

Hypoechoic lesions without halo in echogenic liver. A frequent sonographic dilemma.

Sonographic evaluation for the presence of hypoechoic hepatic lesions without halo was carried out in 365 consecutive patients with echogenic livers. In 115 patients (31%) such lesions could be demonstrated. Computed tomography of the liver was performed in 52 of these patients, a long term sonographic follow-up in 76, and a biopsy in 3 cases. In 103 patients the hypoechoic lesions were due to sonographic pseudolesions (PL's), probably representing normal liver tissue in otherwise diffusely fatty infiltrated livers. The PL's showed characteristic sonographic appearances such as a missing mass effect, a 'landscape'-like configuration with angulated margins and slender extensions of hypoechoic tissue. The PL's were located below the capsule, near the gallbladder (41%), and ventral to the portal vein (37%). In 75 per cent they occurred in a liver with considerably increased echogenicity. In 12 patients hypoechoic lesions were caused by circumscribed malignant or infectious involvement of the liver. They could be discriminated from PL's by their mass-like appearance in 8 subjects. In 4 of these 12 cases the foci were of PL-typical appearance, but not of PL-typical location. In the light of these results and of recently published reports a rational diagnostic approach to hypoechoic lesions without halo in echogenic livers varies, depending on such factors as known primary malignancy or site of the lesion.

Diagnosis, Differential↗
PubMedDate not supplied

Dynamic contrast enhancement of intracranial tumors with snapshot-FLASH MR imaging.

PURPOSE: To investigate whether exact evaluation of the dynamic contrast enhancement pattern within intracranial tumors can help to classify tumor histology and vascularity. METHOD: Forty-nine patients suffering from different intra- and extraaxial intracranial tumors underwent MR-examination in a 1.5-T superconductive whole body system. After rapid injection of Gd-DTPA, 48 images were acquired during the first 1.5 to 2 minutes of contrast enhancement within the tumors. A fast snapshot-FLASH imaging technique allowed measurement times of 1 second per image. Appearance of Gd-DTPA in a venous sinus served as a temporal reference point. Transformation of 48 discrete measurement points (mean signal values of the enhancing tumor region) into a continuous curve, using a cubic spline approximation, allowed calculation of the time of maximum signal increase (Tm1) and the following time of half maximum increase (Tm2). These time parameters were compared to histopathologic findings, especially the degree of tumor vascularization. RESULTS: Significantly different dynamic patterns of the early enhancement period were found for the different tumors. All eight neurinomas, typically less vascularized than most meningiomas, showed a characteristically prolonged contrast enhancement with a long Tm2. Histopathologic findings concerning the degree of vascularization showed two subtypes in meningiomas (n = 17) as well as in pituitary macroadenomas (n = 7). This was confirmed by dynamic evaluation in all cases, in the sense that short Tm1 and Tm2 were found in cases with higher degrees of vascularization. Negatives values of Tm1 were measured in two glomus jugulare tumors, reflecting the arterialization of these vascular tumors. In neuroepithelial tumors (n = 15), the glioblastomas (n = 7) showed very short Tm1 compared to the lower grade gliomas (n = 8). This is explained by histologic findings of pathologic vessels with arteriovenous shunts. CONCLUSION: The evaluated dynamic time parameters can be used to narrow differential diagnostic possibilities and to infer the degree of vascularization of intracranial tumors.

Adenoma↗