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Biomedical subjects

W Grodd

Publications and source records attributed to W Grodd.

33 records · Page 2Linked to original sources
PubMed1987

Edema and the lack of blood perfusion produce opposite effects on the magnetic resonance characteristics of acutely ischemic rat kidneys.

Both kidneys of 28 rats were studied with magnetic resonance imaging (0.35 tesla, double spin-echo technique with echo-delay times [TEs] of 28 and 56 ms and repetition times [TRs] of 0.5 and 2.0 seconds). Kidneys were studied before and up to 4 hours after ligation of the abdominal aorta above the origin of the left renal artery (20 rats) or after ligation of the left renal artery (eight rats). Any changes in the relaxation times of cortex and medulla and in the cortex-to-medulla contrast (CMC) were correlated to histologic data and renal water content. After the first hour following ligation of either the abdominal aorta or the left renal artery, the cortex of the left kidneys showed a 20% shortening of the mean T2 relaxation time (P less than .001), a 16% shortening of the mean T1 relaxation time (P less than .001), a 73% increase in mean CMC on T2-weighted images (P less than .001) and a 42% decrease in mean CMC on T1-weighted images (P less than .001). There were no significant changes either in relaxation times of the medulla of the left kidneys or in relaxation times and CMC of the right kidneys. During the next three hours, relaxation times of cortex and CMC remained unchanged in the rats with ligated abdominal aorta. In the rats with ligated renal artery, relaxation times of cortex and CMC returned to normal values.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1987

[3-dimensional (3-D) image reconstruction of the facial skull and skull base in computerized tomography].

The diagnostic value of three-dimensional (3-D) image reconstruction in conditions affecting the craniofacial skeleton and the skull base has been assessed and the results compared with the CT scans used. Owing to reconstruction artefacts and some limitations in the exact display of 3-D images, no substantial improvement in diagnosis can be expected. Nonetheless, 3-D images facilitate the analysis and detection of complex fractures of the craniofacial skeleton and improve surgical planning and postoperative evaluation.

Facial Bones↗
PubMed1987

Albumin labeled with Gd-DTPA. An intravascular contrast-enhancing agent for magnetic resonance blood pool imaging: preparation and characterization.

A paramagnetic-labeled macromolecule, albumin-(Gd-DTPA), was prepared for use as an intravascular contrast agent for magnetic resonance imaging. An average of 19 Gd-DTPA chelates were covalently conjugated to human serum albumin through the bifunctional anhydride of DTPA. The albumin-(Gd-DTPA) was characterized with use of high-performance liquid chromatography, sodium dodecyl sulfate gel electrophoresis, atomic absorption, biuret and Bradford protein tests, and by its effect on proton relaxation (relaxivity). The average molecular weight was 92,000 daltons, indicating the albumin conjugate was predominantly monomeric. The T1 relaxivity of albumin-(Gd-DTPA) was 273 mM-1 sec-1 relative to carrier concentration, which corresponds to a relaxivity of 14.9 mM-1 sec-1 relative to gadolinium concentration. The average conditional stability constant for albumin-bound Gd-DTPA chelate was log K = 20.0. Spin-echo images of rats demonstrated persistent enhancement of vascular tissues and slowly flowing blood. Application of albumin-(Gd-DTPA) may augment the MR assessments of blood volume, tissue perfusion, and flow characteristics.

Contrast Media↗
PubMed1986

Contrast-enhanced MRI of periarticular soft-tissue changes in experimental arthritis of the rat.

This study was to determine if manipulation of magnetic resonance signal intensity by means of an intravenously injected paramagnetic contrast agent is useful for the detection and characterization of periarticular inflammation. Arthritis was induced in 20 rats by means of intradermal injection of Freund's complete adjuvant. MR imaging was performed with a resistive magnet operating at 0.35 T. A double spin-echo technique with TE's of 28 and 56 ms and TR's of 0.5 and 2.0 s was used. The hindpaws of the adjuvant-injected rats were imaged on Day 8, Day 11, or Day 15 following injection of the adjuvant. The images were obtained in the transverse plane before and after intravenous injection of gadolinium-DTPA (0.2 mmol/kg). Because of their long T2 relaxation time, inflammatory lesions were characterized by high MR signal intensity on precontrast images obtained with long TR and long TE (T2-weighted images). On the other hand, because of their long T1 relaxation time, the inflammatory lesions were of relatively low intensity and not easily recognized on precontrast images obtained with short TR and short TE (T1-weighted images). Postcontrast T1-weighted images were also sensitive in detecting periarticular inflammation as a result of T1 shortening by the gadolinium-DTPA. However, in our particular model, the data did not indicate any greater MR sensitivity for detecting arthritis by means of gadolinium-DTPA enhancement.

Animals↗
PubMed1986

[Magneto-pharmaceutic contrast changes in nuclear magnetic resonance tomography].

Changes in contrast due to paramagnetic substances depend on many factors, such as the properties and concentration of the substance, the external pulse and time parameters and the inherent relaxation time of the tissues. The physical background for contrast enhancement by paramagnetic substances is reviewed and the various groups of magneto-pharmaceuticals which have been used experimentally and clinically are described. The effect on signal intensity due to changes in dose, pulse sequence, repetition and echo times have been simulated and measured on phantoms and the effect of various tissue relaxation times on contrast has been investigated.

Animals↗
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↗
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

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↗