Biomedical subjects

R Nyman

Publications and source records attributed to R Nyman.

65 records · Page 4Linked to original sources

PubMedDate not supplied

Intra-abdominal bleeding in a 14-year-old girl with acute immune thrombocytopenic purpura.

We describe a 14-year-old girl with acute immune thrombocytopenic purpura. She presented with acute abdominal pain, and her hematocrit decreased from 44% to 29%. The bleeding was due to the rupture of a distended follicle on about the 14th day of her menstrual cycle. The patient's low platelet count made possible the continuous oozing of blood from the follicle into the abdominal cavity, causing peritoneal irritation and the fall in hematocrit. She received treatment with intravenous Ig. This case indicates that unnecessary surgery can be avoided if there is reason to believe that the cause of internal bleeding does not require surgical intervention.

Abdominal Pain↗

PubMedDate not supplied

Macroprolactinomas: serial MR imaging in long-term bromocriptine therapy.

PURPOSE: To study the changes in macroprolactinomas during long-term bromocriptine therapy by means of serial MR imaging, and to correlate the findings to the serum prolactin (S-PRL) levels. PATIENTS AND METHODS: Thirteen patients with macroprolactinomas were studied before and during bromocriptine therapy; six to 11 MR examinations were performed with a duration of follow-up of 22 to 74 months. Tumor size, extension, relationship to adjacent structures, and signal intensity patterns were evaluated. Signal intensity ratios and T2 values were calculated in areas of apparently solid tumor tissue. RESULTS: Bromocriptine effectively reduced the size of all tumors; the size reduction was already significant at 1 week, but often continued for several years. Reenlargement during therapy was seen in three cases. The development of chiasmal herniation parallel to increasing cisternal invagination into the sella was a common finding, but was not correlated to visual symptoms. Signal intensity patterns corresponding to hemorrhage, cysts or necrosis were frequently observed, and transitions from one pattern to another were common. Hemorrhage occurred mainly in tumors corresponding to high initial serum prolactin levels. After 1 year of therapy, there was a significant increase in T2 values, indicating an increased water content in residual solid tumor tissue. CONCLUSIONS: MR is valuable for follow-up in bromocriptine therapy of macroprolactinomas, and provides new information on the tumor size changes, the inner structure of the tumors, and the optic chiasm.

Bromocriptine↗

PubMedDate not supplied

Diagnostic methods in planning palliation of spinal metastases.

In a prospective study of 30 patients with newly diagnosed spinal metastases the benefit of different imaging techniques in planning palliation was studied. Magnetic resonance imaging (MRI) was compared to scintigraphy, conventional radiography and computerized tomography (CT), prior to radiotherapy or surgery. In the first comparison, a total of 159 pathologic lesions could be evaluated. MRI was superior in the detection of suspect metastases compared to conventional radiography and scintigraphy (P less than 0.0001 and p less than 0.01, respectively). MRI also gave useful information about adjacent soft tissue components, vessels, nerves and spinal cord compression, i.e. useful information when planning stabilizing surgery. Both MRI and CT were sensitive and specific methods but when comparing 120 pathologic lesions the detection rate of MRI was significantly higher than that of CT (p less than 0.01). In conclusion, scintigraphy and conventional radiography are adequate enough if palliative radiotherapy is planned. When considering surgery MRI is advocated preoperatively for defining operability.

Female↗

PubMedDate not supplied

Magnetic resonance imaging and angiography for the assessment of coarctation of the aorta.

Fifteen patients ranging in age from 9 to 25 years (median age 10 years), with coarctation of the aorta, were investigated with magnetic resonance (MR) imaging pre- and postoperatively. Three patients were examined because of suggested re-stenosis. Both MR examination and cineangiography were performed in 11 patients. The two techniques were comparable concerning the evaluation of both the site and the severity of coarctation as well as of the occurrence of collateral vessels. MR was considered suitable to replace angiography in the pre- and postoperative assessment of coarctation. The patients were preferably examined with a surface spine coil with ECG-gated sagittal, transverse and parafrontal images. The parafrontal images were necessary in order to minimize mistakes due to partial volume effects at the coarctation site. A surface coil placed over the sternum considerably improved the visualization of the internal mammary arteries.

Adolescent↗

PubMedDate not supplied

Field-echo pulse sequences used under suspended respiration for detection of liver metastases.

To obtain a fast MRI sequence for detection of liver metastases under suspended respiration, two healthy volunteers were examined with the field echo sequence FLASH, using a large number of repetition times, echo times, flip angels and matrix sizes. The spleen was used to simulate liver metastases and contrast-to-noise ratios between liver and spleen were calculated and the sequence with the highest ratio was considered optimal. The different FLASH sequences were also compared with spin echo sequences using short repetition and echo times. A FLASH sequence with a repetition time of 140 ms, an echo time of 14 ms, a flip angle of 80 to 100 degrees and a matrix size of 128 x 256 was considered the most suitable for detecting liver metastases. This sequence, together with other FLASH and spin echo sequences, were used for examination of five patients with liver metastases from endocrine gastrointestinal tumours.

Adult↗

PubMedDate not supplied

MR-cholangiography with a double contrast technique.

The combination of superparamagnetic particles (SPP) as a 'negative' contrast agent for the liver parenchyma and Cr-HIDA as a 'positive' one for the bile ducts was tested in dogs. The maximum effect of SPP was present about 30 minutes after injection with a reduction of the image intensity of the liver close to the background noise level at the highest dosages. This effect lasted for about 4 to 5 hours and it had disappeared after 24 hours. Before any contrast administration or after Cr-HIDA the bile ducts were not discernible, but a high signal in the gallbladder was present 15 to 30 minutes after injection of Cr-HIDA. After SPP the wider bile ducts were discernible because of the lowering of the signal intensity in the liver. When SPP were followed by Cr-HIDA, the bile had a higher signal intensity, and even tiny bile ducts were visible. After cholecystokinin visualization of the choledochus duct was achieved as well as contrast filling of the duodenum. The blood, urine, and liver function tests were found normal during the experiments. The combination of superparamagnetic particles and Cr-HIDA seems to be a promising method for MR-cholangiography. An evaluation of the anatomic structures of the liver should be possible with this method in different pathologies.

Animals↗

PubMedDate not supplied

Effect of superparamagnetic particles as oral contrast medium at magnetic resonance imaging. A phase I clinical study.

Non-biodegradable superparamagnetic particles were used as an oral contrast medium in different concentrations, and evaluated in 25 human volunteers. The aim of the study was to determine the most appropriate concentration of the contrast medium, and to evaluate the effect, distribution, safety and tolerance. With the concentration of 1.0 g/l a substantial reduction of the signal intensity in the bowel was achieved in both T1 and T2 weighted images. The intraabdominal structures were well differentiated from the bowels containing contrast medium. 'Metal' artifacts and blurring of adjacent structures, probably due to an increased local concentration, were observed at higher dosages. The distribution of the preparation in the gastrointestinal tract varied between individuals. As a rule a good contrast effect was achieved in the small bowel with the exception of the duodenum. The contrast medium was well accepted and did not cause any side effects of clinical importance. The results suggest that the preparation is well tolerated by humans and may be a useful contrast medium for abdominal MR imaging.

Contrast Media↗

PubMedDate not supplied

Magnetic resonance imaging for assessment of treatment effects in mediastinal Hodgkin's disease.

Six patients with mediastinal involvement of Hodgkin's disease were examined with magnetic resonance imaging (MRI) at 0.35 T before and/or at various stages of therapy, with the sequences TR/TE: 500/35, 500/70, 1600/35 and 1,600/70. Before therapy the image intensity of tumour involved lymph nodes deviated considerably from fat and muscle, but no clear difference was discerned between histopathologic subtypes or tumour localizations. After efficient therapy, the tumour image intensities and relaxation rates approached those of muscle and fibrous tissue, but remained at pre-therapy values when the patient was not in full remission. A similar pattern was found in a 'normal-tissue'--'tumour' plot, based on vector analysis of the original sets of 4 images. It is concluded that persistent tumour involvement in the mediastinum may be distinguished from fibrosis and that MRI may thus be of value in the follow-up of patients with Hodgkin's disease.

Adolescent↗

PubMedDate not supplied

Magnetic resonance imaging in diffuse malignant bone marrow diseases.

Twenty-four patients with malignant bone marrow involvement or polycythemia vera, 8 patients with reactive bone marrow and 7 healthy individuals were examined with spin-echo magnetic resonance imaging at 0.35 T and 0.5 T. Signs of an increased longitudinal relaxation time, T1, were found when normal bone marrow was replaced by malignant cells, polycythemia vera or reactive marrow. A shortened T1 was indicated in 4 patients in bone marrow regions treated by radiation therapy; the marrow was most likely hypocellular in these cases. The estimated T1 relaxation times were highly correlated to the cellularity of the bone marrow as assessed by histology. Among patients with close to 100 per cent cellularity neither T1 nor T2 discriminated between the various malignancies or between malignant and reactive, non-malignant bone marrow. Characterization of tissues in terms of normalized image intensities was also attempted, the motive being to avoid approximations and uncertainties in the assessment of T1 and T2. The normalization was carried out with respect to the image of highest intensity, i.e. the proton density weighted image. The results were in agreement with those for T1 and T2. It was concluded that MRI is valuable for assessing bone marrow cellularity, but not for differentiating between various bone marrow disorders having a similar degree of cellularity.

Adipose Tissue↗

PubMedDate not supplied

Magnetic resonance imaging, chest radiography, computed tomography and ultrasonography in malignant lymphoma.

Magnetic resonance imaging (MRI) was compared with chest radiography, computed tomography (CT) and ultrasonography (US) for demonstration of spleen and liver engagement and enlarged lymph nodes in patients with malignant lymphoma. The investigation comprised 24 patients with Hodgkin's disease (HD) and 39 with non-Hodgkin lymphoma (NHL). MRI demonstrated enlarged lymph nodes, distinctly separated from vessels, fat, muscle, liver and occasionally also pancreas without any contrast medium. The distinction between lymph nodes and spleen was, however, poor in the images. In the mediastinum, MRI was superior to chest radiography and had an accuracy similar to that of CT. In the abdomen and the pelvis MRI had slight advantages over CT in detection of enlarged lymph nodes. Compared with US the MRI results were similar in the abdomen and somewhat better in the pelvis. MRI and US were better than CT in revealing HD infiltrates in the spleen. Infiltration of NHL in the spleen was slightly better disclosed at US than at CT and MRI; most of the NHL infiltration, confirmed at histopathology, could, however, not be revealed with any of the modalities, except when the size of the spleen was considered. Regions in the spleen, displayed with low image intensity in the T2 weighted image, were most likely due to increased amount of fibrotic tissue in the lymphomatous lesions. Good demonstration of lymph nodes and lymphomatous lesions in the spleen with MRI required two sequences; one with short TR and TE (T1 weighted image) and one with long TR and TE (T2 weighted image).

Abdomen↗

PubMedDate not supplied

An attempt to characterize malignant lymphoma in spleen, liver and lymph nodes with magnetic resonance imaging.

An attempt was made to explore whether relaxation times and/or normalized image intensities obtained from magnetic resonance imaging (MRI) can separate malignant and non-malignant lymphomatous tissue. Spin-echo (SE) techniques with repetition times of 500 and 1,500 ms and echo times of 35 and 70 ms were used for estimating T1 and T2. Estimation of T1 and T2 with such a low number of spin-echo sequences resulted in considerable variation in the data especially when T1 was long. Similar information was also extracted by normalizing the image intensities to the 'proton density' image (1,500/35), and the spread of the data was then markedly reduced. Therefore, the method of normalizing was considered a more appropriate way of handling the image data when only a few sequences were available. No significant difference could be discerned in the MRI parameters between normal spleens and spleens infiltrated with malignant lymphoma, between normal livers and livers in patients with malignant lymphoma and between lymph nodes with low or high grade non-Hodgkin lymphoma. Lymphomatous tissue had similar MRI characteristics irrespectively of whether the cells were malignant or not, or located in spleens or in lymph nodes. The main biologic explanation for variation in data seems to be mostly the variable amounts of fibrosis, necrosis, oedema and/or iron content.

Adult↗