K A Thuomas

Uppsala University, Uppsala, Uppsala, Sweden

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Publications (74)118.98 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: MR imaging has been performed on malignant melanomas in vitro and in vivo. Changes of the water content in an enucleated malignant melanoma in vitro were followed by significant changes of the T1 and T2 values. In mice with implanted subcutaneous melanoma similar changes could be obtained after injection of glucose and fructose intraperitoneally. Malignant melanoma of the eye could be influenced in the same way in 10 consecutive patients after oral intake of glucose and fructose. The present study shows that the MR images may be significantly changed after a few hours by altered metabolism induced by glucose and fructose. It is anticipated that this is due to changes within the tumor leading to different water distribution. The finding may be of importance as a further help for diagnosing malignant melanoma of the eye.
    Acta Radiologica. 01/2010; 32(3).
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    ABSTRACT: 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.
    Neurological Sciences 05/2003; 24(1):2-9. · 1.41 Impact Factor
  • European Journal of Pediatric Surgery 01/1999; 8 Suppl 1:64-5. · 0.84 Impact Factor
  • E Olhager, K A Thuomas, L Wigström, E Forsum
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    ABSTRACT: 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.
    Pediatric Research 11/1998; 44(4):572-7. · 2.67 Impact Factor
  • K A Thuomas, P Naeser, A Wrigstad
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    ABSTRACT: To evaluate patients with clinically diagnosed uveal melanoma. 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. 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. 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.
    Acta Radiologica 05/1998; 39(3):239-42. · 1.33 Impact Factor
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    ABSTRACT: To evaluate morphological and physiological changes during acute lethal subdural bleeding in 2 models of anaesthetized dogs. 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. 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. 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.
    Acta Radiologica 08/1997; 38(4 Pt 1):610-20. · 1.33 Impact Factor
  • K A Thuomas, P Naeser
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    ABSTRACT: 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.
    Acta Ophthalmologica Scandinavica 03/1997; 75(1):17-21. · 1.85 Impact Factor
  • M Lundberg, K A Thuomas, K Messner
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    ABSTRACT: To compare radiography, MR imaging, and chemical analysis in posttraumatic knees. 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. 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. MR imaging is the best method for detecting and differentiating early posttraumatic knee arthrosis.
    Acta Radiologica 02/1997; 38(1):151-7. · 1.33 Impact Factor
  • M. Lundberg, K.-å Thuomas, K. Messner
    Acta Radiologica. 01/1997; 38(1):151-157.
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    ABSTRACT: To review pre- and postoperative fast spin-echo (FSE) MR images of disc herniation and spondylosis in patients after spinal cervical surgery. Data were reviewed of 68 patients after anterior discectomy and fusion (ADF) operations using the Cloward technique with solid single level (C5-C6 or C6-C7) or 2-level fusions (C5-C7). The average interval from surgery to review was 37 months. Age- and sex-matched controls without neck problems were examined. Preoperatively, the fusion groups had a higher incidence of protruded disc, and anterior and posterior osteophytes at the levels to be fused than the controls. Post-operatively, there was a significantly higher incidence of posterior osteophytes at the fused levels compared with the controls. Furthermore, the disc herniations and anterior osteophytes at the levels above and below the operated segments were more frequent in the fusion group. ADF causes acceleration of the degenerative changes at the fused level and at the levels below and above the fused segments.
    Acta Radiologica 10/1996; 37(5):614-7. · 1.33 Impact Factor
  • K A Thuomas, I Landau, E Kock, P Naeser
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    ABSTRACT: 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.
    Acta Ophthalmologica Scandinavica 09/1996; 74(4):330-3. · 1.85 Impact Factor
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    ABSTRACT: We wanted to compare the metabolite status of brain lesions in different clinical subtypes of multiple sclerosis (MS). Two acute MS lesions with ringlike appearances were also investigated. Twenty-three clinically stable MS patients, 2 patients with acute relapses, and 15 healthy individuals were examined by MR imaging and localized proton MRS. No metabolite differences were seen in plaques of different subtypes. Decreased NAA/Cr and NAA/choline ratios as well as increased inositol/Cr ratios were observed in the plaques of the clinically stable or chronic active MS patients as compared with controls. The ring plaques had hyperintense cores with surrounding halos, separated from the cores by rings with low signal intensity in T2-weighted images. The core exhibited a prolonged T2 relaxation time. Proton spectra initially contained lactate. No differences between the metabolite status of nonacute plaques in different clinical subtypes could be detected. The ring plaques contained lactate signals indicating oedema, inflammation, and macrophage invasion, and may be transition forms between acute oedematous lesions and chronic demyelinated plaques.
    Acta Radiologica 06/1996; 37(3 Pt 1):278-87. · 1.33 Impact Factor
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    ABSTRACT: 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.
    International Journal of Sports Medicine 05/1996; 17(3):218-22. · 2.27 Impact Factor
  • H Nettelblad, K A Thuomas, F Sjöberg
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    ABSTRACT: 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.
    Burns 04/1996; 22(2):117-9. · 1.80 Impact Factor
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    ABSTRACT: To use MR to examine patients with CNS symptoms indicating +chronic intoxication. Thirty-two subjects exposed to industrial solvents for 5 to 28 years and 40 age-matched, healthy controls were examined. 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. 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.
    Acta Radiologica 04/1996; 37(2):177-9. · 1.33 Impact Factor
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    ABSTRACT: The aim of the investigation was to evaluate poor outcome following spinal and cervical surgery. 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. 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. 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.
    Acta Radiologica 04/1996; 37(2):153-61. · 1.33 Impact Factor
  • L Ekelund, L Sjöqvist, K A Thuomas, B Asberg
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    ABSTRACT: 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.
    Acta Radiologica 02/1996; 37(1):3-13. · 1.33 Impact Factor
  • W Wu, K A Thuomas
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    ABSTRACT: To examine patients with sensorineural hearing loss (SNHL) with MR. 495 consecutive patients with SNHL and 120 age-matched healthy controls were examined. Spin-echo (SE) and fast spin-echo (FSE) images were used with 1.5 T equipment. An intracranial abnormality was found in 211 (42.6%) of the patients with 95 (19.2%) along the acoustic pathway. Eleven of the 95 patients had sensory hearing loss while 84 had neural hearing loss with the retrocochlear auditory pathway affected by lesions. In 62 of the 84 patients, the internal acoustic canal and cerebellopontine angle were involved. Twenty-two patients had intra-axial lesions. The controls had no pathologic changes along the auditory pathway. MR imaging in a patient with SNHL must cover the entire acoustic pathway from the cochlea to the superior temporal gyrus, and all the components of the auditory pathway should be scrutinized. The FSE-technique can be used to detect the lesions causing SNHL. FSE-sequences can replace SE-sequences.
    Acta Radiologica 12/1995; 36(6):603-9. · 1.33 Impact Factor
  • L Jonsson, R Tien, M Engström, K A Thuomas
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    ABSTRACT: Magnetic resonance imaging (MRI) is a new and important tool for use in diagnosing and investigating diseases affecting the facial nerve. In recent gadolinium-DTPA enhanced MRI (Gd-MRI) studies it has unequivocally been demonstrated that ipsilateral facial nerve contrast enhancement, predominantly in the meatal portion, is present in both Bell's palsy and herpes zoster oticus. In this overview, the results of MRI studies performed on patients with acute peripheral facial palsy, especially Bell's palsy and herpes zoster oticus, are discussed. The Gd-MRI pattern in Bell's palsy is very similar to that seen in herpes zoster oticus, and the findings reported so far support the theory that an inflammation may be the cause of the nerve injury in both cases. So far, however, Gd-MRI has not been helpful in evaluating the severity and/or prognosis of the facial palsy. Further studies employing improved techniques, including three-dimensional fast (or turbo) spin echo (3DFSE) MRI with heavily T2-weighted sections and high resolution three-dimensional Fourier transform (3DFT) MRI, need to be conducted in order to determine whether it is possible to follow the course of the disease and whether MRI and/or Gd-MRI are useful prognostic tools in the early stages of palsy.
    Acta Oto-Laryngologica 10/1995; 115(5):577-84. · 1.11 Impact Factor
  • W Wu, K A Thuomas
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    ABSTRACT: Twenty surgically proven pituitary microadenomas were examined with MR imaging and CT. MR demonstrated 20 of 20 microadenomas: 90% of the tumors were hypointense on T1-weighted images before Gd-DTPA administration and in 45% the tumors were more clearly delineated postcontrast. CT demonstrated 19 of 20 diagnosed microadenomas: showing low attenuation in 85% of the tumors precontrast. Iohexol facilitated delineation of the tumors in 45%. Focal enlargement of the gland and diaphragma sellae convexity were more useful than infundibular tilting and sellar-floor erosion as ancillary findings supporting the diagnosis. In general, CT and MR agreed regarding the microadenomas size and location, measurement of enlarged intrasellar contents, detection of the diaphragma sellae bulge, and demonstration of infundibulum abnormality. CT was more sensitive than MR in identifying sellar-floor erosion. We suggest that CT be the first method for demonstration of microadenomas.
    Acta Radiologica 10/1995; 36(5):529-35. · 1.33 Impact Factor

Publication Stats

603 Citations
118.98 Total Impact Points

Institutions

  • 1987–2010
    • Uppsala University
      • Department of Medical Cell Biology
      Uppsala, Uppsala, Sweden
    • Karolinska University Hospital
      Tukholma, Stockholm, Sweden
  • 1990–1999
    • Uppsala University Hospital
      • Department of Pediatrics
      Uppsala, Uppsala, Sweden
    • University of Gothenburg
      Goeteborg, Västra Götaland, Sweden
  • 1997
    • University of Oslo
      Kristiania (historical), Oslo County, Norway
  • 1994–1997
    • University Hospital Linköping
      Linköping, Östergötland, Sweden
  • 1992–1997
    • Linköping University
      • Faculty of Health Sciences
      Linköping, Östergötland, Sweden
  • 1995
    • China-Japan Friendship Hospital
      Peping, Beijing, China
  • 1991
    • University of Lodz
      Łódź, Łódź Voivodeship, Poland
  • 1988–1991
    • Akademiska Sjukhuset
      Uppsala, Uppsala, Sweden