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1、 Diffusion Imaging exploits the random translational mobility of water molecules to obtain information on the microscopic behavior of tissues applies equal and opposite gradients on either side of a refocusing lobe in a standard pulse sequence proton in tissue without motion is initially dephased an
2、d becomes rephased by the opposite gradient mobile protons are not rephased and lead to drop in signal intensity amount of signal loss is a marker of interstitial movement of water and allows indirect evaluation of tissue structure Factors Affecting Water Diffusion In Living Tissue cellular compartm
3、entalization cell type and number cell membrane density and permeability macromolecule size and type tissue viscosity tissue temperature tissue perfusion Patients & Method 117 children with 260 space occupying lesions (72 boys, 39 girls, age range newborn-17 years, mean 8.26 years) CP head coil, 1.5
4、T (Siemens Symphony) axial SS EPI, echo factor 128 TR/TE 220/139, 19 slices, 5mm thick, 1.5 mm gap b = 0, 900 mm2/sec in three directions, phase direction AP 22 cm FOV, 128x128 matrix interpolated to 256x256 4 averages, acquisition time 50 sec, bandwidth 1346 Hz/pixel Trace image - diffusion-weighte
5、d imaging in three axes and post-processed as an expression of its natural logarithm ADC = -1/(b1 - b2) x ln (S1/S2) S1 and S2 - mean signal intensities in the regions of interest with two different gradient factors b1, b2 ADC map - produced by using more than two b values Mann-Whitney U Test, signi
6、ficance p.051.02.052.99.043 Subacute infarct 1.831.07.0151.24.0283.32.021 Chronic infarct 1.981.0201.0303.390 Acute infection 1.030.95.050.94.053.04.018 Hamartoma1.330.90.0011.09.0393.260 Cystic tumor 2.95 0.9901.3103.25.019 Benign tumor2.020.94.0280.98.0283.26.028 Low-grade glioma 1.500.9600.9303.3
7、80 Malignancy1.00 0.99.050.90.053.410 P Acute vs Subacute infarct.01 Acute vs Chronic infarct.001 Subacute vs Chronic infarct.05 Acute infarct vs Infection.05 Acute infarct vs Hamartoma.005 Acute infarct vs Cystic tumor.001 Acute infarct vs Benign tumor.006 Acute infarct vs Low-grade glioma.001 Acut
8、e infarct vs Malignancy.05 Subacute/chronic infarct vs Infection0 Subacute/chronic infarct vs Hamartoma.003 Subacute/chronic infarct vs Cystic tumor 0 Subacute/chronic infarct vs Benign tumor.05 Subacute/chronic infarct vs Low-grade glioma.025 Subacute/chronic infarct vs Malignancy.005 P Infection v
9、s Hamartoma.046 Infection vs Cystic tumor0 Infection vs Benign tumor.022 Infection vs Low-grade glioma.018 Infection vs Malignancy.05 Hamartoma vs Cystic tumor0 Hamartoma vs Benign tumor.001 Hamartoma vsLow-grade glioma.061 Hamartoma vsMalignancy.002 Cystic vs Benign tumor.01 Cystic tumor vs Low-gra
10、de glioma0 Cystic tumor vs Malignancy0 Benign tumor vs Low-grade glioma.004 Benign tumor vs Malignancy0 Low-grade glioma vs Malignancy0 4 day old Infant with Seizure Acute MCA Infarct Chronic Infarct Staph Aureus Abscess Herpes Encephalitis Arachnoid Cyst Craniopharyngioma Juvenile Pilocytic Astrocy
11、toma Medulloblastoma - 15 months post Rx 18 mon post Rx Recurrent MB Residual Medulloblastoma - PICA Infarct Observations inverse relationship between tumor cellularity and ADC low ADC in infection due to high viscosity, inflammatory cells, mucoid protein, cellular debris, and water binding to fibrinogen low ADC in acute infarct, higher ADC in subacute/chronic infarct similar ADC values for acute infarct, infection, and malignancy