| CHAPTER 1:UTILITY OF ARTERIAL SPIN LABELING (ASL) MR IMAGING FOR THE MAPPING OF NORMAL CEREBRAL BLOOD FLOW IN DIFFERENT AGE GROUPSObjective:To assess the utility of arterial spin labeling MR imaging for the mapping of normal cerebral perfusion beginning with the control individuals of different age groups.Materials and methods:This study was conducted between January 2014 and January 2016 in eighty normal individuals of varying age (20—79 years; mean age= 50.12±6.87 years; 43 females and 37 males) with no history of any neurological disease, substance abuse, injury, and nonspecific headache. The subjects were divided into two separate age groups that included adults (n1= 40; 21 females and 19 males; age variance 20-49 years; mean age 35.2±7.45 years) and elderly (n2= 40; 22 females and 18 males; age variance 50-79 years, mean age 65.05±8.00 years) respectively. The recruited patients were found to be normal on routine imaging. Patients with possible risks of artifacts that may degrade ASL imaging were excluded. Imaging and post processing:Conventional MR images were acquired using a 3.0T MR imaging system. Conventional sequences included axial, sagittal and coronal T2-weighted, axial T1-weighted, fluid-attenuated inversion recovery sequence and DW imaging. ASL imaging used a 3-dimensional (3D) pseudocontinuous ASL method. Statistical analysis:The average values of three manually placed regions of interest in both gray and white matters of each lobe from both age groups were extracted and their ratios were calculated as gray-white CBF ratios. All statistical analyses were performed using SPSS 16.0. The one way ANOVA test was used to analyze the difference among the four lobes followed by the application of unpaired Student’s t test to compare the ratios differences between two age groups. P<0.05 was considered to indicate a statistically significant difference.Results:The gray-white CBF ratios of different lobes in adults individuals were measured in a lowest to highest range as frontal:1.44-1.59 (mean 1.49 ± 0.04), temporal:1.4-1.52 (mean 1.44 ± 0.04), parietal:1.37-1.55 (mean 1.46 ± 0.04) and occipital:1.46-1.58 (mean 1.42 ± 0.04), respectively. Similarly, in elderly group, the measurements were 1.25-1.44 (mean 1.35 ± 0.005), 1.18-1.38 (mean 1.28 ± 0.06),1.2-1.4 (mean 1.30 ± 0.06) and 1.16-1.36 (mean 1.25 ± 0.06) in frontal, temporal, parietal and occipital lobes, respectively. No significant difference of gray-white CBF ratios were found among the four different lobes (p>0.05) whereas, a significant difference in each lobes was noticed between two age groups (p=0.00). On bivariate analysis using Pearson’s correlation, a significant negative correlation was observed between an increasing age, and gray-white CBF ratios of all four lobes in both age groups (frontal:r=-0.24, temporal:r=-0.26, parietal:r=-0.25; occipital:r=-0.29, p= 00) in young and (frontal:r=-0.95; temporal:r=-0.94; parietal:r=-0.9; occipital:r=-0.91, p= 00) in elderly, respectively.Conclusion:Arterial spin labeling MR imaging can be very useful in quantifying the perfusion characteristics in almost all age groups of people and it can reliably predict perfusion variance if present in both normal and diseased subjects.CHAPTER 2:DIFFERENTIATION BETWEEN RECURRENT GLIOMAS AND RADIATION NECROSIS USING ARTERIAL SPIN LABELING PERFUSION IMAGINGAim:To evaluate the utility of this technique in the differentiation of recurrent gliomas from radiation necrosis.Materials and methods:Between March 2012 and March 2014,57 surgically treated patients with pathologically confirmed primary gliomas underwent follow-up MRI at 3.0T MR imaging (MRI) system. Using contrast-enhanced T1-weighted imaging, contrast-enhancing lesions were observed in 21 of these cases and were included in for the final study. Sixteen patients received radiotherapy with 50-60 Gy, while 5 received radio chemotherapy (50-60 Gy) combined with temozolomide. Patients to whom temozolomide was administered concurrently received a daily temozolomide dosage of 75 mg/m2 during intensity-modulated radiation therapy, and then at 150 mg/m2 for 5 days in each of six 28-day treatment cycles. Imaging evaluation:Follow-up MRI scans were performed every 3 months and included T2-weighted, diffusion weighted (DW) and ASL perfusion imaging, followed by DSC-MRI. Three maximally perfusion regions of the entire lesions were located by drawing regions of interest (ROIs) of area 0.5-2.0 cm2. The average of the values from these regions was calculated and normalized to the contralateral normal white matter. Statistical analysis:All statistical analyses were performed using SPSS 16.0 (Version 18, SPSS Inc., Chicago, IL, USA). The unpaired Student’s t-test was used for the comparison between the CBF and rCBV values of recurrent gliomas and those radiation necrosis. P<0.05 was considered to indicate a statistically significant difference.Results:In cases of glioma recurrence, the normalized ASL-CBF ratio (4.45±2.72) was higher than that in cases of radiation injury (1.22±0.61) (P<0.01). The normalized DSC-relative CBV ratio was also significantly higher in glioma recurrence (3.38±2.08) than it was in radiation injury (1.09±0.55) (P<0.05). A close linear correlation was found between the ASL and DSC MRI techniques (linear regression coefficient, R=0.83; P=0.005) in the differentiation of recurrent glioma from radiation injury.Conclusion:ASL imaging could potentially be used to determine the perfusion patterns in patients with surgically treated primary gliomas. Moreover, the results indicate that ASL perfusion can be considered as an accurate method of distinguishing between glioma recurrence and radiation necrosis. |
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