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K A Thuomas

Publications and source records attributed to K A Thuomas.

At least 19 recordsLinked to original sources
PubMed2003

Hypointensity in T2-weighted images of the basal ganglia in solvent-exposed patients with multiple sclerosis: clinical, MRI and CSF characteristics.

Several studies have indicated an association between MS and organic solvent exposure. Our objective was to analyse differences regarding cerebrospinal fluid (CSF) properties, magnetic resonance imaging (MRI) features and cerebral metabolites, measured by proton spectroscopy (1H-MRS), in 20 patients with spontaneous multiple sclerosis (MS) and in 20 patients with MS after solvent exposure; 15 healthy subjects served as controls. CSF examinations were retrospectively reviewed from the medical files. There were no significant differences in the CSF regarding pleocytosis, spinal-serum albumin ratio or mean extended IgG index. However, T2-weighted images of the solvent-exposed MS patients showed more hypointenseareas in the basal ganglia. Hypointensity on T2-weighted images of the basal ganglia in the solvent-exposed MS patients may correspond to neurodegeneration and could be an early event in MS.

Adult↗
PubMed1998

Increased accuracy in MR diagnosis of uveal melanoma by carbohydrate loading. A simple method that reflects rapid metabolic change.

PURPOSE: To evaluate patients with clinically diagnosed uveal melanoma. MATERIAL AND METHODS: Forty-eight consecutive patients were examined with spin-echo (SE) and fast spin-echo (FSE) MR sequences that utilized glucose-fructose enhancement together with a subtraction technique on a 1.5 T unit. RESULTS: Twenty-seven patients were enucleated and the eyes histologically examined for tumours (spindle cell, mixed cell, and epitheloid cell). The remaining patients were referred for other treatment. There were no significant differences in T2 although T2 was longer in the amelanotic lesions. Carbohydrate loading in combination with a subtraction technique gave: an increased signal intensity; a prolongation of T2; and an increased tumour size. The FSE sequences were as good as the SE sequences in the visualization of uveal malignant melanoma. CONCLUSION: MR imaging performed with carbohydrate loading registers metabolic changes induced in the tumour. This gives the method great validity in the diagnosis of uveal melanoma. The method is especially useful in amelanotic tumours that have longer relaxation times than melanotic tumours. The SE technique can be replaced with the FSE technique.

Adult↗
PubMed1998

Description and evaluation of a method based on magnetic resonance imaging to estimate adipose tissue volume and total body fat in infants.

Information about body fatness is important during nutritional assessment of infants, but current methods to estimate body composition in vivo are often not applicable in infants. Therefore, a new method based on magnetic resonance imaging (MRI) was developed. This method, which can assess the volume and distribution of adipose tissue (AT) as well as total body fat, was applied in 11 healthy full-term infants. Their total body water was also estimated using the isotope dilution technique. Adipose tissue volume (ATV) was calculated from AT area in 16 images of the body taken by an MRI scanner (1.5 tesla). AT area was assessed using a computer program in which AT criteria was defined by the observer. ATV of the infants was therefore evaluated once by three observers and twice by a fourth observer. The different observers estimated total, s.c., and non-s.c. ATV with a precision that varied between 1.9 and 7.2%, 2.0 and 4.8%, and 4.2 and 40.7%, respectively. Variations during AT area calculations accounted for a large part of the imprecision when assessing total and s.c. ATV. The linear relationship between percent total body water and total ATV in relation to body weight was significant in all evaluations. Although average total ATV varied when estimated by the four observers, there was, within each evaluation, a fairly constant order between infants with respect to their ATV. It is concluded that the MRI procedure represents a useful possibility to assess body fatness in infants.

Adipose Tissue↗
PubMed1998

Central poststroke pain: correlation of MRI with clinical pain characteristics and sensory abnormalities.

OBJECTIVE: To correlate MRI and sensory changes in patients with spontaneous lesions in the cerebral "pain pathway." METHODS: The authors used MRI and quantitative somatosensory testing in 73 patients with central poststroke pain (CPSP) and in 13 patients with pain-free stroke with sensory deficit. RESULTS: Lesions in any part of the discriminatory somatosensory pathway may or may not produce CPSP. Most CPSP patients have multiple lesions, many probably unrelated to pain. Ventroposterior thalamic nuclear lesions are more likely to produce half-body pain than lesions elsewhere (including the brainstem). In supratentorial lesions, the greatest pain is more likely to be in an extremity, and in infratentorial lesions, the greatest pain is likely to be in the face. Supratentorial CPSP patients have a deficit of sharpness and cold (peripherally mediated by A delta fibers) than pain-free stroke patients, whereas patients with infratentorial CPSP additionally have a deficit of C-fiber-mediated warmth and hot pain. Burning pain is more common than nonburning pain in younger patients. Warmth and cold, but not hot pain, exhibiting central convergence (spatial summation) are more affected in CPSP patients with burning than nonburning pain. Allodynic CPSP patients had a significantly greater deficit for warmth than patients without allodynia. CONCLUSIONS: Different stroke sites produce different patterns of sensory deficit. The progression from painless sensory deficit to CPSP is not purely quantitative.

Adult↗
PubMed1997

[Magnetic tomography in diagnosis of breast implant rupture].

At least 20,000 Norwegian women have silicone breast implants, either for breast augmentation or for reconstruction. One of the complications associated with breast implants is rupture of the implants. Magnetic resonance imaging (MRI) has been shown to be the most accurate imaging modality for evaluating the integrity of breast implants. Recognition of the different types of implants and the appearance of normal implants on MRI is very important for distinguishing these from intracapsular and extracapsular ruptures. Examples are shown of MRI findings in normal and ruptured implants.

Breast Implants↗
PubMed1997

Evaluation of knee-joint cartilage and menisci ten years after isolated and combined ruptures of the medial collateral ligament. Investigation by weight-bearing radiography, MR imaging and analysis of proteoglycan fragments in the joint fluid.

PURPOSE: To compare radiography, MR imaging, and chemical analysis in posttraumatic knees. MATERIAL AND METHODS: Ten matched pairs with either isolated partial rupture of the medial collateral ligament or combined medial collateral ligament/anterior cruciate ligament rupture were compared with matched controls 10 years after trauma. Weight-bearing radiographs and MR examinations were compared with proteoglycan fragment concentrations in the joint fluid. RESULTS: The chemical analyses were similar in both trauma groups. The radiographs showed mild signs of arthrosis in half the patients with combined injury. MR images showed almost all injured knees to have degenerative changes of various degrees in the cartilage and menisci. More frequent and more advanced changes were found after combined injury than after isolated injury (p < 0.01). There were no changes in the controls. CONCLUSION: MR imaging is the best method for detecting and differentiating early posttraumatic knee arthrosis.

Adolescent↗
PubMed1997

MR imaging of experimental subdural bleeding. Correlates of brain deformation and tissue water content, and changes in vital physiological parameters.

PURPOSE: To evaluate morphological and physiological changes during acute lethal subdural bleeding in 2 models of anaesthetized dogs. MATERIAL AND METHODS: In model I, blood from the aorta was led into a collapsed subdural rubber balloon while in model II, the blood was directed into the subdural compartment over the left cerebral frontoparietal lobe. Eight vital physiological parameters were continuously registered. MR imaging visualized the compression and displacement of cerebral tissue, and assessed the dynamic changes in cerebral tissue water. RESULTS: In model I, tissue herniation and compression of cerebral ventricles led to death at a haematoma volume corresponding to 8% of the intracranial volume. In model II, the extravasated blood progressed infratentorially and into the spinal sac with a volume that was 3 times larger than that of the lethal haematoma. Tissue water increased almost linearly during bleeding in both models. CONCLUSION: The high level of mortality after acute subdural haematoma is caused by a reduction in intracranial volume tolerance with a critical decrease in cerebral perfusion pressure, resulting in a fatal cerebral ischaemia.

Animals↗
PubMed1997

Long-term follow-up of proton irradiated malignant melanoma by glucose-fructose enhanced magnetic resonance imaging.

MR imaging is frequently used to diagnose uveal melanomas due to the characteristic short T2 relaxation time. T2 may be significantly prolonged within 2 h after ingestion of glucose and fructose due to changed water distribution in the melanoma. This method is used to follow melanomas for up to 6 years after proton beam irradiation. In the tumours, T2 was shortened in parallel in all the lesions during the first 9 months. After this, T2 increased only in tumours which showed recurrence. T2 determination and histopathological examination revealed no signs of recurrence in eyes which were enucleated due to neovascular glaucoma. It is concluded that MR imaging performed with carbohydrate loading, registers metabolic changes induced in the tumour, giving this method great validity in the follow-up of choroidal malignant melanoma after irradiation. Eighteen patients treated with proton beam for uveal melanoma at the cyclotron in Uppsala, Sweden, were followed.

Administration, Oral↗
PubMed1996

Magnetic resonance imaging: a new diagnostic aid in the care of high-voltage electrical burns.

Magnetic resonance imaging (MRI) can detect and delineate alterations in the hydration properties of tissues such as oedema and necrosis. The distinction between living tissue oedema and frank necrosis is also possible with MRI, by use of a spin-echo (SE) sequence and a fast spin-echo (FSE) sequence with a 1.5 T imager. With this background, the aim of this study was to examine the ability of MRI for early detection of concealed tissue injuries caused by high-voltage electrical burns, an entity not previously explored. Clinical use of MRI examinations in patients with high-voltage injuries admitted to the Burn Unit at Linköping University Hospital, has resulted in the significant elucidation of the deeper tissue injuries that occur. The T2-weighted images provided substantial information about the localization and amount of muscle necrosis, thus enabling increased surgical precision in the treatment of these high-voltage injury victims. FSE sequences produce T2-weighted images with increased speed of acquisition and/or increased image resolution compared to conventional SE sequence. Two illustrative examples are provided.

Adult↗
PubMed1996

The diagnostic validity of magnetic resonance imaging in acute knee injuries with hemarthrosis. A single-blinded evaluation in 69 patients using high-field MRI before arthroscopy.

Sixty-nine patients with traumatic knee hemarthrosis were evaluated an average of 3 days after trauma by high field (1.5T) magnetic resonance imaging (MRI) using sagittal T1, T2-weighted and coronal 3D-gradient echo images. All knees were arthroscopically examined shortly afterwards. The diagnostic validity of MRI for intraarticular pathology was determined using arthroscopy as golden standard. All patients had pathological findings on arthroscopy. The injuries were sports-related in 77% of the cases. MRI was highly sensitive (86%) and specific (92%) for diagnosis of anterior cruciate ligament tears. Diagnosis of medial meniscal tears showed a 74% sensitivity and 66% specificity. MRI detected lateral meniscal tears in 50% with an 84% specificity. As such, MRI missed 10 significant meniscus ruptures requiring surgical treatment. The sensitivity for partial or total medial collateral ligament tears was 56%, the specificity 93%. Rupture of the medial retinaculum in cases with patellar dislocation or significant damage of articular cartilage were only detected by MRI in a few cases (27% and 20% sensitivity, respectively). MRIs low diagnostic validity for intraarticular pathology with hemarthrosis may be attributed to the shifting paramagnetic properties of the blood remains and catabolic processes in meniscal and chondral tissues during the hemoglobin degradation process. Accordingly, MRI, with the technique used, could neither replace arthroscopy in the diagnosis and screening of acute knee injuries, nor select patients with need for immediate arthroscopic meniscal surgery.

Acute Disease↗
PubMed1996

Recurrence of malignant melanoma after irradiation diagnosed by glucose-fructose enhanced magnetic resonance imaging.

Two patients who had been given ruthenium plaque treatment for uveal melanoma were MR examined due to suspected recurrence. Spin-echo sequences were applied using a 1.5 T equipment. The examinations were performed in both patients two times with a 2-h interval. Immediately after the first examination the patients were perorally given 20 g glucose and 10 g fructose. An increase of signal intensity (prolongation of the relaxation times) and size of the uveal lesions could be visualized by a subtraction technique in both patients after the carbohydrate loading. In agreement with our previous studies of malignant melanoma the changed metabolism in the uveal lesions indicated recurrence of the tumour. One eye was available for histological examination. The morphological difference between areas of recurring and degenerating tumour was clearly seen. Similar changes were not observed by ultrasound.

Brachytherapy↗
PubMed1996

MR angiography of abdominal and peripheral arteries. Techniques and clinical applications.

This review article deals with MR angiography (MRA) of abdominal and peripheral arteries. Pulsatile flow, respiratory motion and peristalsis impose difficulties in imaging the vascular structures in the abdomen and the lower extremities. Development of new techniques, such as segmentation of the data acquisition, using specific acquisition windows in relation to a cardiac trigger, magnetization preparation of the tissue and phase-encoding re-ordering or sorting, have reduced the artifacts associated with abdominal and peripheral MRA. Clinical MR investigations of the arteries branching from the abdominal aorta such as the renal and mesenteric arteries and arteries in the lower extremities have revealed that severe stenoses or occlusions can be diagnosed accurately while the grading of less severe stenosis is more difficult. The phase-contrast method has been used to quantify blood flow and study the hemodynamics in abdominal and peripheral vessels. Quantitative flow information can be used to diagnose vascular disease and provides important physiological information. More prospective clinical studies, in which recently developed MRA techniques are compared with conventional angiography, are necessary before conclusive decisions can be made as to whether MRA may replace these methods.

Abdomen↗
PubMed1996

Fast spin-echo MR assessment of patients with poor outcome following spinal cervical surgery.

PURPOSE: The aim of the investigation was to evaluate poor outcome following spinal and cervical surgery. MATERIAL AND METHODS: A total of 146 consecutive patients operated with anterior discectomy and fusion (ADF) with the Cloward technique were investigated. Clinical notes, plain radiography, CT, and fast spin-echo (FSE) images were retrospectively evaluated. RESULTS: Some 30% of the patients had unsatisfactory clinical results within 12 months after surgery; 13% had initial improvement followed by deterioration of the preoperative symptoms, while 14.4% were not improved or worsened. Disc herniation and bony stenosis above, below, or at the fused level were the most common findings. In 45% of patients, surgery failed to decompress the spinal canal. In only 4 patients was no cause of remaining myelopathy and/or radiculopathy found. FSE demonstrated a large variety of pathological findings in the patients with poor clinical outcome after ADF. Postoperatively, patients with good clinical outcome had a lower incidence of pathological changes. CONCLUSION: FSE is considered the primary imaging modality for the cervical spine. However, CT is a useful complement in the axial projection to visualize bone changes.

Adult↗
PubMed1996

MR imaging in solvent-induced chronic toxic encephalopathy.

PURPOSE: To use MR to examine patients with CNS symptoms indicating +chronic intoxication. MATERIAL AND METHODS: Thirty-two subjects exposed to industrial solvents for 5 to 28 years and 40 age-matched, healthy controls were examined. RESULTS: All patients showed decreased signal in the basal ganglia on T2-weighted images. In 11 of the patients the white matter showed diffuse hyperintensity with loss of the grey-white matter discrimination and with distinct periventricular hyperintensities in 5 of the patients. The controls had no pathological changes in the brain. CONCLUSION: Although the relatively small number of patients may obscure the significance, findings observed on T2-weighted images were patchy periventricular hyperintensities and hypointensities in the basal ganglia. Fast spin-echo is a good technique with fast acquisition of images with true spin-echo contrast features.

Adult↗
PubMed1996

Tolerance and efficacy of Omniscan (gadodiamide injection) in MR imaging of the central nervous system.

PURPOSE: This Swedish multicenter trial was performed on patients with known or suspected lesions of the CNS for which an MR examination using a contrast medium was indicated. A total of 8 MR centers participated in the study to establish the safety and efficacy of Omniscan (gadodiamide injection) in clinical routine using a standard dose of 0.1 mmol Gd/kg b.w. MATERIAL AND METHODS: Seven hundred adult patients who had been referred for MR investigation of suspected CNS lesions were included in the study. Since most patients were examined on an outpatient basis, it was decided to use an explicit questionnaire regarding adverse events that developed within 24 h after examination. The efficacy evaluation involved comparisons of detectability, delineation, and number of lesions before and after injection of Omniscan. RESULTS: No serious or unexpected adverse event was found. There were a total of 70 (10.2%) patients with adverse events, excluding those judged not to be contrast media-related. However, only 15 patients (2.2%) had adverse events that possibly or probably were related to the contrast medium. Usually, the symptoms were headache, dizziness, abnormal taste, and nausea. Two patients complained of itching, but only one developed urticaria. The efficacy was similar to that of other currently used Gd-based MR agents. Lesions were more often seen on T2-weighted images, but the contrast medium improved lesion delineation, contributing to higher certainty in diagnosis, and provided more confidence in excluding suspected abnormality. CONCLUSION: Omniscan was found to be a safe and clinically valuable contrast medium for MR imaging of the CNS.

Adolescent↗