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- Blystad, Ida, 1972-
(author)
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Clinical Applications of Synthetic MRI of the Brain
- 2017
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Doctoral thesis (other academic/artistic)abstract
- Magnetic Resonance Imaging (MRI) has a high soft-tissue contrast with a high sensitivity for detecting pathological changes in the brain. Conventional MRI is a time-consuming method with multiple scans that relies on the visual assessment of the neuroradiologist. Synthetic MRI uses one scan to produce conventional images, but also quantitative maps based on relaxometry, that can be used to quantitatively analyse tissue properties and pathological changes. The studies presented here apply the use of synthetic MRI of the brain in different clinical settings.In the first study, synthetic MR images were compared to conventional MR images in 22 patients. The contrast, the contrast-to-noise ratio, and the diagnostic quality were assessed. Image quality was perceived to be inferior in the synthetic images, but synthetic images agreed with the clinical diagnoses to the same extent as the conventional images.Patients with early multiple sclerosis were analysed in the second study. In patients with multiple sclerosis, contrast-enhancing white matter lesions are a sign of active disease and can indicate a need for a change in therapy. Gadolinium-based contrast agents are used to detect active lesions, but concern has been raised regarding the long-term effects of repeated use of gadolinium. In this study, relaxometry was used to evaluate whether pre-contrast injection tissue-relaxation rates and proton density can identify active lesions without gadolinium. The findings suggest that active lesions often have relaxation times and proton density that differ from non-enhancing lesions, but with some overlap. This makes it difficult to replace gadolinium-based contrast agent injection with synthetic MRI in the monitoring of MS patients.Malignant gliomas are primary brain tumours with contrast enhancement due to a defective blood-brain barrier. However, they also grow in an infiltrative, diffuse manner, making it difficult to clearly delineate them from surrounding normal brain tissue in the diagnostic workup, at surgery, and during follow-up. The contrast-enhancing part of the tumour is easily visualised, but not the diffuse infiltration. In studies three and four, synthetic MRI was used to analyse the peritumoral area of malignant gliomas, and revealed quantitative findings regarding peritumoral relaxation changes and non-visible contrast enhancement suggestive of non-visible infiltrative tumour growth.In conclusion, synthetic MRI provides quantitative information about the brain tissue and this could improve the diagnosis and treatment for patients.
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| 2. |
- Blystad, Ida, et al.
(author)
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Quantitative MRI for Analysis of Active Multiple Sclerosis Lesions without Gadolinium-Based Contrast Agent
- 2016
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In: American Journal of Neuroradiology. - : American Society of Neuroradiology (ASNR). - 0195-6108 .- 1936-959X. ; 37:1, s. 94-100
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Journal article (peer-reviewed)abstract
- BACKGROUND AND PURPOSE: Contrast-enhancing MS lesions are important markers of active inflammation in the diagnostic work-up of MS and in disease monitoring with MR imaging. Because intravenous contrast agents involve an expense and a potential risk of adverse events, it would be desirable to identify active lesions without using a contrast agent. The purpose of this study was to evaluate whether pre-contrast injection tissue-relaxation rates and proton density of MS lesions, by using a new quantitative MR imaging sequence, can identify active lesions.MATERIALS AND METHODS: Forty-four patients with a clinical suspicion of MS were studied. MR imaging with a standard clinical MS protocol and a quantitative MR imaging sequence was performed at inclusion (baseline) and after 1 year. ROIs were placed in MS lesions, classified as nonenhancing or enhancing. Longitudinal and transverse relaxation rates, as well as proton density were obtained from the quantitative MR imaging sequence. Statistical analyses of ROI values were performed by using a mixed linear model, logistic regression, and receiver operating characteristic analysis.RESULTS: Enhancing lesions had a significantly (P < .001) higher mean longitudinal relaxation rate (1.22 ± 0.36 versus 0.89 ± 0.24), a higher mean transverse relaxation rate (9.8 ± 2.6 versus 7.4 ± 1.9), and a lower mean proton density (77 ± 11.2 versus 90 ± 8.4) than nonenhancing lesions. An area under the receiver operating characteristic curve value of 0.832 was obtained.CONCLUSIONS: Contrast-enhancing MS lesions often have proton density and relaxation times that differ from those in nonenhancing lesions, with lower proton density and shorter relaxation times in enhancing lesions compared with nonenhancing lesions.
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| 3. |
- Blystad, Ida, 1972-, et al.
(author)
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Quantitative MRI for analysis of peritumoral edema in malignant gliomas
- 2017
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In: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 12:5
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Journal article (peer-reviewed)abstract
- Background and purpose Damage to the blood-brain barrier with subsequent contrast enhancement is a hallmark of glioblastoma. Non-enhancing tumor invasion into the peritumoral edema is, however, not usually visible on conventional magnetic resonance imaging. New quantitative techniques using relaxometry offer additional information about tissue properties. The aim of this study was to evaluate longitudinal relaxation R-1, transverse relaxation R-2, and proton density in the peritumoral edema in a group of patients with malignant glioma before surgery to assess whether relaxometry can detect changes not visible on conventional images. Methods In a prospective study, 24 patients with suspected malignant glioma were examined before surgery. A standard MRI protocol was used with the addition of a quantitative MR method (MAGIC), which measured R-1, R-2, and proton density. The diagnosis of malignant glioma was confirmed after biopsy/surgery. In 19 patients synthetic MR images were then created from the MAGIC scan, and ROIs were placed in the peritumoral edema to obtain the quantitative values. Dynamic susceptibility contrast perfusion was used to obtain cerebral blood volume (rCBV) data of the peritumoral edema. Voxel-based statistical analysis was performed using a mixed linear model. Results R-1, R-2, and rCBV decrease with increasing distance from the contrast-enhancing part of the tumor. There is a significant increase in R1 gradient after contrast agent injection (P<.0001). There is a heterogeneous pattern of relaxation values in the peritumoral edema adjacent to the contrast-enhancing part of the tumor. Conclusion Quantitative analysis with relaxometry of peritumoral edema in malignant gliomas detects tissue changes not visualized on conventional MR images. The finding of decreasing R-1 and R-2 means shorter relaxation times closer to the tumor, which could reflect tumor invasion into the peritumoral edema. However, these findings need to be validated in the future.
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| 4. |
- Nordanskog, Pia, 1971-
(author)
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On electroconvulsive therapy in depression : Clinical, cognitive and neurobiological aspects
- 2015
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Doctoral thesis (other academic/artistic)abstract
- Electroconvulsive therapy (ECT) is used worldwide to treat severe mental disorders. The most common mental disorder, and the third leading cause of disease burden in the world is depression. The clinical efficacy of ECT for severe depression is well-established. However, both the pathophysiology of depression and the mechanism of action of ECT remain elusive.The main aims of this thesis are to address the following issues: 1) the use and practice of ECT in Sweden has not been systematically evaluated since 1975, 2) cognitive side-effects (memory disturbances) are a major concern with ECT and 3) the mechanism of action of ECT remain elusive. The neurobiological aspects of ECT focus on two hypotheses. First, the recent years´ preclinical studies that have provided evidence that ECT induces hippocampal cell proliferation, including neurogenesis. Second, that enhanced functional inhibition of neuronal activity is a key feature.Current use and practice of ECT in Sweden (paper I) is based on data from the national quality register for ECT, the mandatory patient register of the National Board of Health and Welfare and a survey. Treated person rate (TPR) in Sweden 2013 was found to be 41 individuals / 100 000, and thus unchanged since the latest systematic investigation in Sweden 1975. In more than 70% of treatment series the indication was a depressive episode. The selection of patients for ECT and treatment technique in Sweden was similar to that in other western countries, but the consent procedure and the involvement of nurses and nursing assistants in the delivery of ECT differ. Data also shows that there is room for improvement in both the specificity of use and availability of ECT.The second study in this thesis is a longitudinal observational trial where 12 (paper II and III) and 14 (paper IV) patients with depression referred for ECT were investigated. Patients underwent a 3 T MRI structural scanning and DSC-MRI perfusion, a neuropsychological test battery and clinical ratings before ECT, within one to two weeks after ECT and after 6 and 12 months. In line with preclinical findings and the plasticity hypothesis of mechanism of action of ECT, the hippocampal volume increased after ECT in patients with depression. However, this increase was transient and returned to baseline levels within 6 months. No correlation was found between volumetric changes and clinical effect or cognitive outcome. Instead our results suggested an association to the number of treatments, without relation to the side of stimulation. A right-sided decrease in frontal blood flow distinguished remission from non-remission after ECT. There were significant impairments in verbal episodic memory and verbal fluency within one week after ending the ECT course, but these impairments were transient and no persistent cognitive impairments were seen during the follow-up.In summary, this thesis present the first update on the use and practice of ECT in Sweden in the last 40 years as well as a pioneering MRI-study on the hippocampal volume increase in the treatment of depression with ECT. Supportive to earlier findings we also found the cognitive side-effects that are measurable after ECT to be transient. Furthermore, we found that a decreased frontal blood flow is of importance for the anti-depressive response to ECT.
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