Objective To study the value of three-dimensional pseudo-continuous arterial spin labeling(3D pCASL) for estimating collateral flow after middle cerebral artery(MCA) stenosis.Methods 3D pCASL was performed in 28 cases of negative diffusion weighted imaging(DWI) patients with MCA stenosis for estimating collateral vessels formation.The post-labeling delay(PLD) of 3D pCASL was set to 1.5 s and 2.5 s.The cerebral blood flow (CBF) of 3D pCASL with two PLD was calculated by AW workstation respectively.Nineteen normal persons were regarded as the control group.The 95% confidence interval of the ratio of left/right side of CBF of control group was set as reference value.The characteristic of the ratio of stenosed/contralateral side of CBF was analyzed.The characteristics of collateral flow was investigated with digital subtraction angiography(DSA).Results Abnormal perfusion was found in 28 patiens.Two types of abnormal perfusion were found, including typeⅠ: rCBF(PLD=1.5 s) decreased,rCBF(PLD=2.5 s) was normal (n=16);typeⅡ:rCBF(PLD=1.5 s) decreased,rCBF(PLD=2.5s) decreased (n=12).On brain DSA, abundant of collateral flow supply was found in 16 patients with typeⅠabnormal perfusion,whereas deficiency of collateral flow supply was found in 12 patients with typeⅡ.Conclusion 3D pCASL with two PLDs may provide important reference value for estimating collateral flow after middle cerebral artery stenosis.

Objective To explore the value of intravoxel incoherent motion (IVIM) imaging in evaluating diffusion and perfusion variations in subacute brain infarction.Methods MRI data of 35 patients with subacute brain infarction were analyzed retrospectively,including routine DWI,IVIM imaging and three-dimensional arterial spin labeling (3D-ASL) sequence.The ADC maps were obtained by routine DWI sequence.Pure molecular-based diffusion coefficient (D) maps,pseudo diffusion coefficient of perfusion (D*) maps and perfusion fraction (f) maps were obtained by IVIM sequence.Cerebral blood flow (CBF) maps were obtained by 3D-ASL sequence.ADC,D,D*,f,CBF values and the relative values (rADC,rD,rD*,rf,rCBF) of brain infarction lesion and contralateral mirror area were calculated.All the parameters between brain infarction lesion and contralateral mirror area were compared.The correlations were analyzed between rADC value and rD,rD*,rf values respectively,as well as between rCBF value and rD,rD*,rf values respectively.Results Quantitative analysis showed significant decreases of ADC,D,D*,f and CBF values in the brain infarction lesion compared with those in the contralateral mirror area (all P＜0.05).There were positive correlations between rADC value and rD,rf values (r=0.687,0.601,P=0.005,0.018).And the positive correlation was found between rCBF value and rf value (r=0.581,P=0.022).Conclusion IVIM imaging can concurrently provide the perfusion and diffusion informations of subacute brain infarction patients,which is helpful to further elucidate the mechanisms of subacute brain infarction.

Objective To assess the value of apparent diffusion coefficient (ADC)map with low b-value to monitor the ablated tissue after high-intensity focused ultrasonic (HIFU)treatment for uterine fibroids.Methods 25 patients with 34 uterine fibroids were treated with HIFU.All patients underwent the routine MRI scans (including pre-and post-contrast scanning)and monoexponential model DWI with b values of 150,600 and 1 000 s/mm2 before the surgery and within 24 hours after the surgery.The mean ADC values with different b-values of the ablated and non-ablated tissues between pre-and post-treatment were analyzed by one-way ANOVA test.The consistency of the ablation area between ADC maps with different b-values and contrast enhancement MRI were evaluated. Results With the b-value of 150 s/mm2 ,the mean ADC value of the ablated tissue was (1.48±0.27)×10-3 mm2/s,which was less significantly than that of pre-treatment (2.06±0.21)×10-3 mm2/s and non-ablated tissue (1.98±0.23)×10-3 mm2/s (P<0.05). However,there were no significant differences in ADC values with the b values of 600 s/mm2 and 1 000 s/mm2 among those areas (P>0.05).A fine consistency of the ADC map with the low b-value (150 s/mm2 )was found with non-perfusion volume on contrast-enhanced T1 WI,which was superior to that with high b-values (600 s/mm2 and 1 000 s/mm2 )(P<0.05).Conclusion ADC map with low b-value (150 s/mm2 )can be used to evaluate the blood-supply changes and ablated volume of uterine fibroids indirectly,which helps to assess the treatment effect of HIFU.