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Biomedical subjects

Ari Karttunen

Publications and source records attributed to Ari Karttunen.

9 recordsLinked to original sources
PubMed2006

Enhancement of brain tumors in 0.23-T low-field MRI: comparison of edema attenuated inversion recovery (EDAIR) sequences with T1-weighted sequence.

RATIONALE AND OBJECTIVES: The aim of this study is to explore whether edema attenuated inversion recovery (EDAIR) sequences could be used to improve tumor contrast in contrast-enhanced low-field 0.23-Tesla magnetic resonance imaging (MRI) using 0.1 mmol/kg of gadolinium-based contrast agent. MATERIALS AND METHODS: Ten patients with brain tumors were examined by using the following contrast-enhanced sequences: T1-weighted spin echo, EDAIR with inversion time (TI) of 600 milliseconds, and EDAIR with TI of 800 milliseconds. Images were assessed both quantitatively and qualitatively. RESULTS: Results suggest that tumor contrast enhancement in low-field MRI can be improved without increasing contrast agent dose. EDAIR 600 appears to be optimal in most cases. CONCLUSIONS: This inversion recovery sequence could be applicable as an additional sequence in the imaging of metastases in low-field MRI, as well as imaging of any other enhancing brain tumors or lesions in low-field MRI.

Adolescent↗
PubMed2004

Muscle computed tomography patterns in patients with the mitochondrial DNA mutation 3243A>G.

Computed tomography provides a sensitive method for investigating skeletal muscle changes in neuromuscular diseases, but this method has not been applied to mitochondrial myopathies. We characterized the pattern of muscle involvement in patients with the 3243A>G mutation in mitochondrial DNA (mtDNA), the common MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes) mutation. Twenty-four patients, age 19-73 years, with 3243A>G were examined. Clinical evaluation included assessment of muscle strength and functional capacity. All the patients underwent muscle computed tomography, and muscle samples from 17 of them were examined for the presence of ragged red fibres and for the 3243A>G heteroplasmy. Venous blood lactate at rest and serum creatine kinase were determined. Clinical myopathy was found in six patients, while nine showed mild muscle weakness and nine had normal muscle function. The upper and lower limbs were equally affected, but the proximal muscles were more severely affected than the distal ones. CT revealed abnormalities in the muscles of 13 patients (54%; 95% confidence interval, 33-76%), including the six with clinical myopathy and seven without clinical myopathy. Myopathic changes were found most frequently in the pelvic muscles, with predominant involvement of the gluteus maximus. These data show that CT reveals frequent abnormal findings in the muscle of patients with the 3243A>G mtDNA mutation. Muscle CT is a useful adjunct to clinical evaluation in these patients.

Adult↗
PubMed2004

Computer-assisted diagnosis by temporal subtraction in postoperative brain tumor patients: a feasibility study.

RATIONALE AND OBJECTIVES: To introduce and evaluate a novel, image fusion-based technique that can be used to compare the findings of primary and control brain magnetic resonance imaging scans, with special attention to the differences found in this comparison. MATERIALS AND METHODS: A new technique named "colored difference mapping" was applied to the brain examinations of five patients. The possible changes in the magnetic resonance imaging findings were analyzed by the colored difference mapping technique and by using conventional film reading and the results were compared. RESULTS: Colored difference mapping accurately depicts the differences between successive magnetic resonance images and reveals small changes that are difficult to perceive in a visual evaluation. CONCLUSION: Colored difference mapping is suitable for comparison of images between two different radiologic examinations and helps to show even minimal changes in brain tissues.

Adolescent↗
PubMed2004

Dynamic MR imaging of brain tumors in low field using undersampled projection reconstruction.

A new application of the projection reconstruction method was developed, enabling dynamic T(1)-weighted contrast-enhanced magnetic resonance image (MRI) of brain tumors in a low-field imager. Two undersampled projection reconstruction spin echo sequences were implemented in an open low-field (0.23-T) MR imager, one with 64 and another with 42 projections in [0,pi], repetition time 150 ms, echotime 15 ms, and six slices were used in both sequences. The possibility of using these sequences to image dynamic contrast enhancement of brain tumors was studied in laboratory experiments and in two patient cases, one with fibrotic and the other with meningothelial meningioma. The laboratory experiments showed a nearly linear response in signal intensity to the concentration of gadopentetate dimeglumine in purified water up to 1.25 mM. Increasing concentrations up to 5.0 mM did not significantly affect the signal intensity, though starting from 3.0 mM concentration T(2) shortening decreased intensities slightly. The patient cases showed results consistent with an earlier study performed in a high-field imager. The results show that the studied sequences can be used to follow dynamic contrast enhancement in a low-field imager.

Aged↗
PubMed2003

A portable diagnostic workstation based on a Webpad: implementation and evaluation.

A wireless hand-held Webpad device was used to review a sample set of cranial computerized tomography (CT) studies to assess its diagnostic capabilities and its feasibility as a portable diagnostic workstation for radiology. The data-set consisted of 30 head CT studies of emergency cases. Two neuroradiologists and a senior radiologist participated in the evaluation of the portable workstation. They used a Web-based viewer that we developed, which provided all the major functionalities required for radiological image review. The reported radiological findings and diagnoses were compared with a gold standard, comprising a set of diagnoses previously formulated by a consensus panel of radiologists who had reviewed the original studies. The diagnoses made using the Webpad were correct (no major discrepancies) in 82 out of 90 interpretations (91%), which is comparable to the accuracy reported in image review with a conventional radiological workstation. The average total working time per diagnosis was 5 min 25 s (range 2-12 min). The simplicity of use of the system and its low cost make it suitable for distributing radiological studies within hospital facilities.

Adolescent↗