To Evaluate the Brain Iron Content by Susceptibility Weighted Imaging: Experimental Study and Clinical Application
|Course||Medical Imaging and Nuclear Medicine|
|Keywords||Magnetic Resonance Imaging R2* Susceptibility Weighted Imaging Rabbit Brain Iron Nuclei|
The subject includes two parts: First: The purpose of this study was to investigate the feasibility of the Susceptibility Weighted Imaging, in contrast of R2* sequence, to evaluate brain iron content in rabbit, the gold standard was the iron content measured by the atomic absorption spectrometer. Second: To analyse the brain content iron content in deep nuclear clusters of gray matter of the normal volunteers by the phase values of ESWAN, investigate the differences of the content of brain iron among deep nuclear clusters and the age-related trends.The First Part: To investigate the feasibility of the Susceptibility Weighted Imaging to evaluate the brain iron content in rabbitObjective: To investigate the feasibility of the Susceptibility Weighted Imaging, in contrast of R2 * sequence, to evaluate brain iron content in the basal ganglia of rabbit, the gold standard was the brain iron content measured by the atomic absorption spectrometer. Compare the ability of the two method to assess the biain iron content.Material and methods: 24 adult or old healthy New Zealand rabbits were examinated by 3.0T MRI respectively, The sequences included R2 and ESWAN scanning in coronal position, and T2WI in axil and sagiittal plane were also scanned. The main target for scanning were the basal ganglia. After examination the rabbits were euthanized by carbon dioxide gas, and the brain was extracted at once,then the tissues were fixed by immersion in 4% paraformaldehyde in phosphate buffer (pH 7.4) for two to three days. The basal ganglia of specimens were cut into pieces according to the coronal scanning standard. At last the coronal basal ganglia specimens were examined histologically, which were stained in the routine method, including hematoxylin-eosin coupled with luxol fast blue and Perls’method used to detect iron total nonheme iron from the basal ganglia which was measured by atomic absorption spectroscopy. The relationship between the values of ESWAN or R2* and the total nonheme iron was analysed.Result: The average value of the basal ganglia including the content of total iron, the value of R2* and ESWAN was 0.858±0.304 mg Fe/ g dry tissue, 0.0781±0.0562, -0.0875±0.054. The measured values are in line with normal distribution and homogeneity of variance. R2* values, ESWAN phase values had a linear relationship with brain iron (correlation coefficient R was 0.936 and 0.888, coefficient of determination R2 was 0.780 and 0.870, respectively), the linear relationship obtained by analysis of variance F = 82.419, 154.865, P <0.001, two linear relationships were highly statistically significant. ESWAN phase value had a srtonger linear relationship with brain iron content than R2* did.Conclusion:Both R2* values and ESWAN phase value can reflect the rabbit brain iron content, and there was a linear relationship between them; but ESWAN phase had evaluated brain iron content stronger than the value of R2* sequence.The Second Part: The distribution of iron content in brain nuclei and preliminary age-related study by SWI in MRObjective: To measure the normal brain iron content of the nuclei and age-related changes by The ESWAN phase in 3.0T MRI.Material and methods: 30 normal healthy adult volunteers, divided by age into three groups: 11 cases were aged between 18 and 30; 13 cases were aged 30-60 years; 6 cases were aged over 60 years. MRI examination were performed, including axial T2WI, ESWAN, etc. After the inspection, draw the regions of interest of the nucleus (globus pallidus, putamen, caudate nucleus, substantia nigra and red nucleus) manually, then phase values of ESWAN were measured. ANOVA (LSD method), Paired t test analysis were applied to analysis the statistical differences among the nuclei, two sides of the nuclei and age groups.Result: 1. ESWAN phase value of the globus pallidus, putamen, caudate nucleus, substantia nigra and red nucleus were in line with normal distribution and homogeneity of variance. the mean value of the globus pallidus, putamen, caudate nucleus, substantia nigra and red nucleus were -0.1920±0.06692, -0.1393±0.07250, -0.1494±0.04173, -0.1910±0.07889, -0.1286±0.07782; 2. The ESWAN phase values of five regions were significantly different, in which there was no significant difference between the globus pallidus and substantia nigra, and no significant difference among the putamen, red nucleus and caudate nucleus; but statistically significant differences between the globus pallidus, substantia nigra and the putamen, red nucleus, caudate nucleus. 3. The Paired t testconfirmed that there are significant differences between the two sides of the globus pallidus, putamen, caudate nucleus, substantia nigra, while no difference between the two sides of the red nucleus; 4. There was no significant difference between globus pallidus, substantia nigra and red nucleus in three age groups (P > 0.05), but statistically different among the putamen, the caudate nucleus in three age groups. Conclusion: The ESWAN phase values of globus pallidus, putamen, caudate nucleus, substantia nigra and red nucleus were different in which the absolute value of the globus pallidus and substantia nigra was maximum which reflected higher iron content of the two nuclei; There were significant differences between both sides of the nucleies but other than red nucleus; The ESWAN phase value of the putamen and the caudate nucleus became more negative with age, reflecting the iron content of the two nuclei gradually increased with age.