Alterations in the basal ganglia in patients with brain tumours may be due to excessive iron deposition.

The accumulation of iron in the brain is a common physiological process. However, alterations in the deposition of iron or other paramagnetic substances are associated with various diseases. In the present study, the deposition of paramagnetic substances in patients with brain tumours was evaluated using T2 relaxometry. A total of 23 patients with untreated tumours or with recurrent tumours following treatment, together with a group of 19 age-matched healthy controls, were examined using T2 relaxometry at 3T. The relaxation times in the basal ganglia, thalamus and white matter were evaluated. Significantly lower T2 relaxation times were identified in the basal ganglia and thalamus of the patients with tumours, as compared with those of the controls (P<0.05). No statistically significant difference was identified between patients with untreated or recurrent brain tumours. The reduction in T2 relaxation times in the brain tumour patients was possibly caused by the accumulation of iron, since iron homeostasis is known to be altered in patients with tumours. We propose that increased iron deposition is a consequence of a higher risk of oxidative stress caused by an increased iron concentration in the plasma or cerebrospinal fluid.

jSIPRO - analysis tool for magnetic resonance spectroscopic imaging.

Magnetic resonance spectroscopic imaging (MRSI) involves a huge number of spectra to be processed and analyzed. Several tools enabling MRSI data processing have been developed and widely used. However, the processing programs primarily focus on sophisticated spectra processing and offer limited support for the analysis of the calculated spectroscopic maps. In this paper the jSIPRO (java Spectroscopic Imaging PROcessing) program is presented, which is a java-based graphical interface enabling post-processing, viewing, analysis and result reporting of MRSI data. Interactive graphical processing as well as protocol controlled batch processing are available in jSIPRO. jSIPRO does not contain a built-in fitting program. Instead, it makes use of fitting programs from third parties and manages the data flows. Currently, automatic spectra processing using LCModel, TARQUIN and jMRUI programs are supported. Concentration and error values, fitted spectra, metabolite images and various parametric maps can be viewed for each calculated dataset. Metabolite images can be exported in the DICOM format either for archiving purposes or for the use in neurosurgery navigation systems.

Metabolic changes in the auditory cortex in presbycusis demonstrated by MR spectroscopy.

In humans, aging is accompanied by the deterioration of the hearing function--presbycusis. The major etiology for presbycusis is the loss of hair cells in the inner ear; less well known are changes in the central auditory system. Therefore, we used 1H magnetic resonance spectroscopy at 3T tomograph to examine metabolite levels in the auditory cortex of three groups of subjects: young healthy subjects less than 30 years old and subjects older than 65 years either with mild presbycusis corresponding to their age or with expressed presbycusis. Hearing function in all subjects was examined by pure tone audiometry (125-16,000 Hz). Significant differences were found in the concentrations of glutamate and N-acetylaspartate, with lower levels in aged subjects. Lactate was particularly increased in subjects with expressed presbycusis. Significant differences were not found in other metabolites, including GABA, between young and elderly subjects. The results demonstrate that the age-related changes of the inner ear are accompanied by a decrease in the excitatory neurotransmitter glutamate as well as a lactate increase in the auditory cortex that is more expressed in elderly subjects with large hearing threshold shifts.

Quantitative MR imaging and spectroscopy of brain tumours: a step forward?

OBJECTIVES: A prospective quantitative MR study of brain tumours was performed to show the potential of combining different MR techniques to distinguish various disease processes in routine clinical practice. METHODS: Twenty-three patients with various intracranial tumours before treatment (diagnosis confirmed by a biopsy) and 59 healthy subjects were examined on a 3-T system by conventional MR imaging, 1H spectroscopic imaging, diffusion tensor imaging and T2 relaxometry. Metabolic concentrations and their ratios, T2 relaxation times and mean diffusivities were calculated and correlated on a pixel-by-pixel basis and compared to control data. RESULTS: Different tumour types and different localisations revealed specific patterns of correlations between metabolic concentrations and mean diffusivity or T2 relaxation times. The patterns distinguish given tissue states in the examined area: healthy tissue, tissue infiltrated by tumour, active tumour, oedema infiltrated by tumour, oedema, etc. This method is able to describe the complexity of a highly heterogeneous tissue in the tumour and its vicinity, and determines crucial parameters for tissue differentiation. CONCLUSIONS: A combination of different MR parameters on a pixel-by-pixel basis in individual patients enables better identification of the tumour type, direction of proliferation and assessment of the tumour extension. KEY POINTS : • Magnetic resonance offers many different methods of examining the brain. • A combination of quantitative MR parameters helps distinguish different brain lesions • Different tumour types revealed specific correlation patterns amongst different MR parameters • The correlation patterns reflect highly heterogeneous complex tissue within tumours.

Changes in the brain during long-term follow-up after liver transplantation.

PURPOSE: To examine changes in the brain before liver transplantation caused by the accumulation of paramagnetic ion deposits and to investigate recovery after liver transplantation over a long-term horizon. MATERIALS AND METHODS: Fifteen patients indicated for liver transplantation, 26 patients up to 2 years after, and 40 patients 8-15 years after liver transplantation were subjected to MR relaxometry. T(1) and T(2) relaxation times in the basal ganglia, thalamus, and white matter were evaluated. RESULTS: Relaxometry revealed a shortening of the relaxation times due to the deposition of paramagnetic ions in the basal ganglia before liver transplantation (P < 0.05), complete normalization of the relaxation times shortly after transplantation in the globus pallidus and caudate nucleus, and partial recovery of T(2) in the putamen. Relaxation times remained stable even 15 years posttransplantation. Increased relaxation times posttransplantation were found in the white matter and thalamus. CONCLUSION: The shortening of the relaxation times observed in the basal ganglia before liver transplantation was caused by paramagnetic ion deposition. The recovery observable within 2 years after transplantation was permanent, and no recurrence of paramagnetic ion deposition was observed even 15 years posttransplantation. Changes in the white matter and thalamus after transplantation were attributed to damage caused by permanent exposure to immunosuppressants.

MR spectroscopy as a tool for in vivo determination of steatosis in liver transplant recipients.

OBJECT: Among several non-invasive methods of liver fat analysis, the most important role is played by MR imaging and spectroscopy (MRS). This study describes the 1H MRS at 3T measurement of liver fat volume fraction Φ(fat) in a group of liver transplant patients, an at-risk group for the development of de novo steatosis. MATERIALS AND METHODS: Seventy-seven liver transplant recipients who underwent routine protocolar posttransplant examination were divided into three groups: CON-PAT (control group for the cross validation test, 48 patients), PAT-PAT (patients test group for the cross validation test, 29 patients), and PAT (pooled data). Single voxel 1H MRS at 3T was used for the determination of Φ(fat) and histology results (His) were used as the reference standard. RESULTS: Linear and non-linear regression models were used to describe the relationship between Φ(fat) and His. Strong correlation was found for both models with r = 0.83-0.94 (P < 0.001); a higher r was found for non-linear regression in all tested groups. Areas under receiver operation curves were calculated for cut points His ≥ 5 and > 33% and were found in the range of 0.77-0.86. Fibrosis influences the calculation of Φ(fat) and different slopes were obtained for fibrosis stages F0-F1 and F2-F3, respectively. CONCLUSION: Significant correlation was found between the results of histology and 1H MRS measurement of liver fat content. The method is suitable for non-invasive repetitive examination of liver fat in liver-transplants patients between protocol biopsies and for the screening of steatosis in other liver diseases.

[Determination of liver triglycerides by 1H MR spectroscopy]. / Stanovení obsahu jaterního tuku metodou 1H MR spektroskopie.

BACKGROUND: Metabolic syndrome is responsible for increasing the fat content of the liver. Among several non-invasive methods of liver fat analysis, the most important role is played by magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS). This pilot study describes the methodology for measurements of triglycerides in the liver in a group of liver transplant patients using 1H MRS at 3T. METHODS AND RESULTS: Thirty-eight patients (12 Female, 27 male, aged 19-71) who underwent routine preventive examination at IKEM were included in the MRS study. The fat content of liver biopsies was classified according to the number of affected hepatocytes, HIS. Based on this classification, there were 20 patients with a steatosis score of S0, 15 patients with a score of S1, 2 patients with a score of S2 and 1 patient with a score of S3. 1H MR spectra were measured from three positions in the liver. Following Longo et al, the concentration of fat phi(fat), was calculated from the signal intensities of water and triglycerides. Linear correlation between the number of affected hepatocytes and fat content was described by the equation: HIS = 6.4 phi(fat) -2.1; r2 = 0.85; p = 0.001. CONCLUSIONS: The pilot study confirmed that examination of fat content using 1H MRS at 3T is well tolerated by patients. Significant correlation was found between the results of histology and 1H MRS measurement of liver fat content. The method is suitable for non-invasive repetitive and screening examination measurement of fat in the liver.

The correlation between 1H MRS choline concentrations and MR diffusion trace values in human brain tumors.

OBJECTIVE: The aim of this study was to develop a method for evaluating the spatial distribution of human brain gliomas in individual subjects by evaluating the correlation between the Choline (Cho) signal intensity and the diffusion trace (Tr(ADC)) values. MATERIALS AND METHODS: Eleven patients with different histopathologic diagnoses and five healthy subjects were examined with diffusion-weighted EPI-trace sequence and (1)H MR spectroscopic imaging. The calculation of the correlation between choline and Tr(ADC) values on a pixel-by-pixel basis and simulations estimating the influence of partial volume effects on the result were performed. RESULTS: Statistical evaluation of the data in the patients with a glioblastoma showed that pixels corresponding to different tissue states are situated in different areas in the Cho-Tr(ADC) correlation graph. Namely, points forming an inverse linear dependence interpreted as an area of an active tumor were observed. Different types of correlations were found in grade II and III gliomas. No statistically significant correlation was found in healthy subjects. Simulations proved that the observed linear dependence cannot be attributed solely to partial volume effects. CONCLUSION: The analysis of the correlation between Cho concentrations and Tr(ADC) values on a pixel-by-pixel basis should help the regional identification of the pathological state of a tissue in patients with a glioblastoma.