| 1. |
- Holtås, Stig, et al.
(författare)
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Epilepsiutredning. Magnettomografi allt viktigare diagnosteknik
- 1997
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Ingår i: Läkartidningen. - 0023-7205. ; 94:23, s. 2194-2200
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Tidskriftsartikel (refereegranskat)abstract
- Electroencephalography (EEG) and neuroradiology are both indispensible techniques in cases of suspected epileptic seizure, when the aim of investigation is to determine whether the seizure was of epileptic nature, and if so whether it was the result of specific provocative factors or an expression of epileptic disease. In the latter case, the epileptic condition should be classified and its aetiology determined, if possible. Routine or sleep EEG providing interictal epileptiform discharges is a useful aid to differential diagnosis. To obtain EEG recordings during actual seizures, long-term recordings, using either ambulatory equipment or an EEG-video procedure, are usually used. The combination of EEG and video recording, using surface or surgically implanted electrodes, is a procedure of major importance in the evaluation of patients refractory to medical treatment and possible candidates for epilepsy surgery. In cases of epilepsy suspected to be caused by tumour or cerebrovascular disease, neurological investigation does not differ from that routinely used in such conditions. MRI (magnetic resonance imaging) techniques have become important aids in the preoperative work-up in cases of chronic therapy-resistant partial epilepsy. MRI has also simplified the identification of minor morphological abnormalities causing partial epilepsy, and is the method of choice in such cases. The sensitivity of MRI is improved by its combination with volumetric measurements and spectroscopy. The use of functional neuroimaging with SPECT (single photon emission computed tomography) and PET (positron emission tomography) during seizures provides further information. A promising new development is the co-registration of MRI and functional imaging (dipolar reconstruction of EEG spikes and seizure patterns, SPECT, PET). MRI is a cornerstone of the preoperative work-up, but diagnosis and the choice of therapeutic approach is always based on the clinical picture, EEG, and functional and morphological imaging.
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| 2. |
- Källén, Kristina, et al.
(författare)
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Evaluation of malignancy in ring enhancing brain lesions on CT by thallium-201 SPECT
- 1997
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Ingår i: Journal of Neurology, Neurosurgery and Psychiatry. - 1468-330X. ; 63:5, s. 569-574
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To investigate patients with cystic enhancing lesions on CT and to determine whether thallium-201 (201Tl) SPECT adds to further preoperative information in differential diagnosis between gliomas and abscesses. METHODS: Twenty one patients with cystic ring enhancing CT findings were studied and uptake indices were compared with CT enhancement volumes, histopathology, and survival times. RESULTS: Fourteen high grade gliomas, three low grade gliomas, and four abscesses were found. Uptake was higher in the highly malignant glioma group (median thallium index (TI)=2.1), than in the low grade glioma group (median TI=1.4) or among the abscesses (median TI=1.6). Overlapping indices were found between high and low malignant cystic gliomas as well as between either one of the glioma groups and the infectious lesions, and there were no significant differences between groups. There was a level at the value 2, where TI > or = 2 correlated with tumour diagnosis. One low grade tumour had an extremely high index and a very high enhancement volume. Indices correlated significantly with CT enhancement volumes (P=0.005). There was no significant correlation between Tl indices and patient survival times among the high grade gliomas. One patient with a highly malignant tumour but low Tl uptake < 2, had a survival > five years. CONCLUSIONS: It is concluded that high 201Tl uptake in enhancing cystic lesions is an indicator of highly malignant glioma. However, the differentiation between the high malignant gliomas and abscesses or low malignant gliomas by 201TL SPECT is only partial with an overlap between these groups.
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| 3. |
- Björkman-Burtscher, Isabella, et al.
(författare)
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Proton (1H) MR spectroscopy for routine diagnostic evaluation of brain lesions
- 1997
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Ingår i: Acta Radiologica. - 1600-0455. ; 38:6, s. 953-960
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To describe the introduction and performance of proton MR spectroscopy (1H-MRS) in the daily routine of a modern standard MR unit. MATERIAL AND METHODS: Over an 8-month period, 52 patients with brain lesions were studied with 1H-MRS, using SE and STEAM sequences for chemical-shift imaging and single-volume spectroscopy. The quality of the spectra was graded from 1 (best) to 3, and the main factors influencing the quality of the spectra were evaluated. RESULTS: Of the measurements: 85% were graded as 1; 12% as 2; and 3% as 3. The main reasons for poor spectral quality were: the unfortunate positioning of the VOI; hemorrhage; and/or postoperative changes within the VOI. Of 40 patients with a final diagnosis: MRS provided an increased confidence in MR diagnosis in 18 cases; MRS contributed significantly to preoperative diagnosis in 3 cases; and the spectra were not specific (n = 10) or were difficult to evaluate (n = 9) owing to reduced quality (grade 2 or 3) in 19 cases. CONCLUSION: MRS of the brain can provide a high percentage of interpretable spectra and frequently can increase confidence in the MR diagnosis of brain lesions in clinical routine.
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| 4. |
- Ståhlberg, Freddy, et al.
(författare)
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Use of k-space segmentation in MR velocity mapping for rapid quantification of CSF flow
- 1997
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Ingår i: Journal of Magnetic Resonance Imaging. - : Wiley. - 1522-2586 .- 1053-1807. ; 7:6, s. 972-978
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Tidskriftsartikel (refereegranskat)abstract
- In this work, a k-space segmentation technique for quantitative studies of pulsatile cerebrospinal fluid (CSF) flow is suggested. Three k-space lines are sampled for each of two interleaved gradient-echo sequences (velocity-compensated and velocity-encoded) within each repetition interval. Nine cardiac phases are obtained at a heart rate of 60 bpm with maintained nominal resolution and a factor of 3 in reduction of acquisition time relative to our conventional nonsegmented flow quantification protocol. Segmented and conventional sequences were compared in phantoms, in healthy volunteers, and in two patients with clinically suspected normal pressure hydrocephalus. Good agreement between flow curves obtained with the two sequences was demonstrated in vitro as well as in vivo. A slight underestimation of flow values in volunteers was attributed to data filtering when using the segmented sequence. Because the CSF circulation is complex and tightly connected to the vascular circulation, specific clinical applications may require flow studies at multiple positions and with different velocity encoding. In such cases, the proposed sequence can be used to gain time, but alternatively, the segmentation technique can be used to further increase spatial resolution within reasonable examination times.
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| 5. |
- Wang, C, et al.
(författare)
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Diagnostic efficacy of MnDPDP in MR imaging of the liver. A phase III multicentre study
- 1997
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Ingår i: Acta Radiologica. - 1600-0455 .- 0284-1851. ; 38:4, s. 643-649
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To assess the diagnostic efficacy, safety and tolerability of mangafodipir trisodium (MnDPDP, Teslascan) in MR imaging of the liver. MATERIAL AND METHODS: Eighty-two patients from 4 centres underwent MR imaging with pre-contrast sequences including T1-weighted SE and GRE, and T2-weighted turbo SE sequences. MnDPDP at a dose of 5 mumol/kg b.w. was administered by slow i.v. infusion, and 20-60 min after infusion the T1-weighted SE and GRE sequences were repeated. Diagnostic efficacy was evaluated by counting the number of lesions and by evaluating whether more information for lesion characterisation was available in post-contrast images. Safety and tolerability were assessed by recording adverse events and infusion-related discomfort. RESULTS: Significantly more lesions were found in MnDPDP-enhanced T1-weighted SE and GRE images than in unenhanced images of the same sequences. More lesions were also found in these images compared with T2-weighted images at a level of marginal significance. More information was obtained from MnDPDP-enhanced images in 40 cases. Mild to moderate adverse events were experienced by 17% of the patients. CONCLUSION: MnDPDP-enhanced images can improve lesion detection in the liver and are helpful for lesion characterisation. To obtain optimal diagnostic information of liver lesions T2-weighted images are also valuable. MnDPDP is a safe contrast agent for MR imaging of liver lesions.
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| 6. |
- Wirestam, Ronnie, et al.
(författare)
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The perfusion fraction in volunteers and in patients with ischaemic stroke
- 1997
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Ingår i: Acta Radiologica. - 1600-0455. ; 38:6, s. 961-964
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Tidskriftsartikel (refereegranskat)abstract
- The fractional volume of capillary blood, i.e. the perfusion fraction f, was measured with the aid of an echo-planar imaging protocol originally designed for the measurement of water diffusion. In healthy volunteers, reasonable f values were obtained. In patients with cerebral ischaemic stroke, a marked decrease in the f value was seen in the infarcted region as compared with corresponding values in the contralateral hemisphere. We suggest that perfusion-fraction measurements may add to the diagnostic value of water-mobility examinations in patients with ischaemic disease.
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| 7. |
- Åkeson, Per, et al.
(författare)
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Brain lesion contrast in MR imaging. Dependence on field strength and concentration of gadodiamide injection in patients and phantoms
- 1997
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Ingår i: Acta Radiologica. - 1600-0455. ; 38:1, s. 14-18
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To compare the contrast effects of gadodiamide injection at 0.3 and at 1.5 T, at different concentrations in phantoms, and to correlate the results to clinical doses used for examining brain lesions. MATERIAL AND METHODS: Gel phantoms with T1 and T2 corresponding to brain gray matter were doped with different concentrations of gadodiamide injection and examined with T1-weighted sequences. Two different sets of phantoms were used, one for 0.3 T and one for 1.5 T. To express contrast, a quotient (RATIOphantom) between signals in each tube with gadodiamide injection and in the one without it was calculated. A corresponding quotient (RATIOpatient) between signals in brain metastases and in gray matter was calculated in 16 patients examined at 0.3 T (0.1 and 0.3 mmol Gd/kg b.w.) and in 5 patients examined at 1.5 T (0.1 mmol Gd/kg b.w.). RESULTS: Maximum RATIOphantom and RATIOpatient were more than 50% higher at 1.5 T than at 0.3 T at equal concentrations using heavily T1-weighted sequences. The use of SE TR/TE 600/30 instead of 400/25 reduced the contrast effect 15-45% depending on concentration. Comparing RATIOpatient to RATIOphantom suggests that the maximum T1 effect of Gd contrast media occurs at higher doses than in current clinical use, as at 0.1 mmol/kg b.w. we achieved 38% (0.3 T) and 56% (1.5 T) of the maximum phantoms. At 0.3 mmol/kg b.w. we achieved 63% (0.3 T) of the theoretical maximum. CONCLUSION: The contrast effect of Gd contrast media is higher at 1.5 T than at 0.3 T. Higher doses than presently used might prove useful especially at lower field strengths where the contrast effect of Gd is less pronounced. Heavy T1-weighting is also important.
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| 8. |
- Åkeson, Per, et al.
(författare)
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Time-dependency in brain lesion enhancement with gadodiamide injection
- 1997
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Ingår i: Acta Radiologica. - 1600-0455. ; 38:1, s. 19-24
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To determine the effective time window for MR imaging of tumors with blood-brain barrier (BBB) damage after injection of Gd-containing contrast media. MATERIAL AND METHODS: Eleven patients with 15 brain lesions (metastasis, glioma, abscess) were studied with a T1-weighted spin-echo sequence repeated over periods of up to 43 min after contrast injection. A quotient was calculated between the signals in the lesion and in the gray matter, and plotted against time. RESULTS: All lesions reached 70% of the maximum RATIO within 3.5 min. After 25 min 12 out of 15 lesions showed persistent enhancement within 15% of the maximal RATIO. CONCLUSION: The peak enhancement of BBB damage occurs around 3.5 min after injection. The effect does not change during the next 25 min. Scanning should not be started until 2-5 min after injection of the contrast medium, and there is no advantage in waiting longer as no major increase (or decline) of contrast can be expected.
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