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- Dahlqvist Leinhard, Olof, 1978-
(författare)
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Quantitative magnetic resonance in diffuse liver and neurological disease
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Magnetic resonance (MR) has become one of the most important diagnostic tools in modern medicine. It provides superior soft tissue contrast compared to other imaging modalities, it is extremely flexible as it can be used to image all parts of the body, and it is considered to be safe for patients.Today almost all MR is performed in a non-quantitative manner, only by comparing neighbouring tissue in the search for pathology. It is possible to quantify the MR-signals to its physical entities, but time consuming and complicated calibration procedures have prevented this in clinical routine.In this work two different applications of quantitative MR-spectroscopy in diffuse liver and neurological disease, and a new rapid method for simultaneous quantification of proton density, T1 relaxation and T2* relaxation in MR-imaging are presented.In Paper I, absolutely quantified phosphorus MR-spectroscopy was tested as a predictive tool in order to determine the degree of fibrosis on patients with diffuse liver disease. One group with steatosis and none to moderate inflammation (n=13), one group with severe fibrosis or cirrhosis (n=16), and one group of healthy volunteers (n=13) were included in the study.Lower concentrations of PDE (p = 0.025), and a higher metabolic charge (AC) [42] (p < 0.001) were found in the cirrhosis group. A sensitivity and specificity of 81% and 69% respectively, were found for the discrimination between mild and advanced fibrosis using PDE concentrations, and 93% and 54% using AC. The results suggest PDE as a marker of liver fibrosis and AC as a potential clinically useful parameter in discriminating mild from advanced fibrosis.In Paper II proton MR-spectroscopy was used to investigate if there were differences in the concentrations of the observable metabolites in normal appearing white matter in patients with clinically definite multiple sclerosis (MS), and with normal MR-images compared to healthy volunteers. This 'MRI-negative' group consisted of fourteen patients which were compared with fourteen healthy controls. Absolutely quantified proton MR-spectra were acquired from four different voxels in NAWM.Significant differences in absolute metabolite concentrations were observed between the two groups. The MS-patients had lower total N-acetyl compounds (tNA) (p=0.002) compared to the healthy controls and lower concentration of choline-containing compounds (Cho) compared to the healthy controls (p<0.001). EDSS showed a slightly positive correlation to myolns concentrations (0.14mM/EDSS,r2 = 0.06) and a slightly negative correlation to tNA concentrations (-0.41 mM/EDSS,r2 = 0.22). The finding of lower Cho concentrations has not been reported previously and was unexpected.In Paper III a new rapid imaging method was presented for determination of proton density, B1, T2* relaxation and T1 relaxation. The method was based on a modified Look-Locker pulse sequence with two main differences. (1) The exchange of the inversion pulse in the Lock-Looker sequence to a saturation pulse in order to enable detection of the B1 field, and (2) the introduction of a multi-echo read-out to enable the detection of T2*. The signal intensity was then scaled to proton density using the estimated B1, T1, and T2* value.The method was validated in vitro, using phantoms filled with solution of different T1 and T2* water relaxation values, and by comparing the results of the measurements to reference metcyods. In vivo the method was compared with literature values.The validation showed that the method was highly accurate, both in vitro and in vivo, and that this method enabled quantitative imaging of MR-parameters within a clinically feasible examination time. Potential applications of the method are, among a great range of possibilities, to rapidly provide all the necessary quantification parameters in MR-spectroscopy, and to simultaneously provide fast quantitative diagnostic imaging.
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- Friman, O., et al.
(författare)
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A General Method for Correction of Intensity Inhomogeniety in Two Point Dixon Imaging
- 2008
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Ingår i: Proceedings of the International Society for Magnetic Resonance in Medicine annual meeting (ISMRM'08). - : International Society for Magnetic Resonance in Medicine.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Two point Dixon imaging can be used for quantitative fat estimation. However, field inhomogeneities pose a problem that needs to be corrected for before quantitative measurements can be obtained. We present a general framework for field inhomogeneitiy correction by fitting a set of smooth 3D spatial basis functions to voxels with high fat content. By choosing the number of basis functions, the smoothness constraint of the field can be controlled. The method is evaluated by measuring the FWHM of the fat peak in histograms for different number of basis functions. It is also compared to a previous method with good results.
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- Gustafsson, M C, et al.
(författare)
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Low Choline Concentrations in Normal-Appearing White Matter of Patients with Multiple Sclerosis and Normal MR Imaging Brain Scans
- 2007
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Ingår i: American Journal of Neuroradiology. - 0195-6108 .- 1936-959X. ; 28:7, s. 1306-1312
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND PURPOSE: Spectroscopic studies (1H-MR spectroscopy) of normal-appearing white matter (NAWM) in patients with multiple sclerosis (MS) with MR imaging brain lesions have already been performed, but our intention was to investigate NAWM in MS patients who lack brain lesions to elucidate whether the same pathologic changes could be identified.MATERIALS AND METHODS: We checked 350 medical files of patients with MS who are registered in our institution. Fourteen patients (11 women and 3 men; mean age, 48.6 years; handicap score, Expanded Disability Status Scale [EDSS] 2.9; range, 1–6.5) with clinically definite MS and a normal MR imaging of the brain were included. 1H-MR spectroscopy was performed in 4 voxels (size approximately 17 × 17 × 17 mm3) using absolute quantification of metabolite concentrations. Fourteen healthy control subjects (11 women and 3 men; mean age, 43.3 years) were analyzed in the same way.RESULTS: Significant differences in absolute metabolite concentrations were observed, with the patients with MS showing a lower total concentration of N-acetyl compounds (tNA), including N-acetylaspartate and N-acetyl aspartylglutamate (13.5 mmol/L versus 14.6 mmol/L; P = .002) compared with the healthy control subjects. Unexpectedly, patients with MS presented significantly lower choline-containing compounds (Cho) compared with healthy control subjects (2.2 mmol/L versus 2.4 mmol/L; P < .001). The EDSS showed a positive correlation to myo-inositol concentrations (0.14 mmol/L per EDSS; r2 = 0.06) and a negative correlation to tNA concentrations (−0.41 mmol/L per EDSS; r2 = 0.22).CONCLUSION: The unexpected finding of lower Cho concentrations has not been reported previously. We suggest that patients with MS who lack lesions in the brain constitute a separate entity and may have increased protective or healing abilities.
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- Kechagias, Stergios, et al.
(författare)
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Fast-food-based hyper-alimentation can induce rapid and profound elevation of serum alanine aminotransferase in healthy subjects
- 2008
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Ingår i: Gut. - : BMJ. - 0017-5749 .- 1468-3288. ; 57:5, s. 649-654
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To study the effect of fast-food-based hyperalimentation on liver enzymes and hepatic triglyceride content (HTGC).Design: Prospective interventional study with parallel control group.Setting: University Hospital of Linko¨ping, Sweden.Participants: 12 healthy men and six healthy women with a mean (SD) age of 26 (6.6) years and a matched control group.Intervention: Subjects in the intervention group aimed for a body weight increase of 5–15% by eating at least two fast-food-based meals a day with the goal to double the regular caloric intake in combination with adoption of a sedentary lifestyle for 4 weeks.Main outcome measures: Weekly changes of serum aminotransferases and HTGC measured by proton nuclear magnetic resonance spectroscopy at baseline and after the intervention.Results: Subjects in the intervention group increased from 67.6 (9.1) kg to 74.0 (11) kg in weight (p,0.001). Serum ALT increased from 22.1 (11.4) U/l at study start to an individual mean maximum level of 97 (103) U/l (range 19.4–447 U/l). Eleven of the 18 subjectspersistently showed ALT above reference limits (women .19 U/l, men .30 U/l) during the intervention. Sugar (mono- and disaccharides) intake during week 3 correlated with the maximal ALT/baseline ALT ratio(r=0.62, p=0.006). HTGC increased from 1.1 (1.9)% to 2.8 (4.8)%, although this was not related to the increase in ALT levels. ALT levels were unchanged in controls.Conclusion: Hyper-alimentation per se can induce profound ALT elevations in less than 4 weeks. Our study clearly shows that in the evaluation of subjects with elevated ALT the medical history should include not only questions about alcohol intake but also explore whetherrecent excessive food intake has occurred.
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- Magnusson, Maria, 1961-, et al.
(författare)
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Improved temporal resolution in radial k-space sampling using an hourglass filter
- 2009
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Ingår i: ISMRM 17th Scientific Meeting & Exhibition. - Honolulu, Hawaii, USA.
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Konferensbidrag (refereegranskat)abstract
- Radial sampling of k-space is known to simultaneously provide both high spatial and high temporal resolution. Recently, an optimal radial profile time order based on the Golden Ratio was presented in [1]. We have adopted and modified the idea, with a focus onhigher temporal resolution without sacrificing any image quality.[1] Winkelmann et. al.: An optimal radial profile order based on the golden ratio for time-resolved MRI, IEEE Trans. Med. Im, Vol.26, No.1,2007.
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- Magnusson, Maria, 1961-, et al.
(författare)
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Radial k-space sampling: step response using different filtering techniques
- 2009
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Ingår i: ISMRM Workshop on Data sampling and Image Reconstruction. - The Enchantment Resort, Sedona, Arizona, USA.
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Konferensbidrag (refereegranskat)abstract
- Radial sampling of k-space is known to simultaneously provide both high spatial and high temporal resolution. Recently, an optimalradial profile time order based on the Golden Ratio was presented in [1]. We have adopted and modified the idea, with a focus onhigher temporal resolution without sacrificing any image quality.[1] Winkelmann et. al.: An optimal radial profileorder based on the golden ratio for time-resolved MRI, IEEE Trans. Med. Im, Vol.26, No.1, 2007.
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