摘要目的：探讨动态对比增强MRI（DCE?MRI）定量渗透性参数和离体高分辨魔角旋转磁共振质子波谱（1H HRMAS NMRS）对X线全身照射（TBI）后大鼠股骨骨髓微血管渗透性状态与骨髓脂肪含量、脂肪酸成分变化之间的关系。方法36只6~8周龄SD大鼠随机分为TBI组和对照组（n=18/组），TBI组大鼠接受6.0 Gy高能量X线全身照射，对照组大鼠不进行照射处理。照射前、照射后第4、7天分别行股骨DCE?MRI灌注成像检查，测量股骨兴趣区（ROI）微血管转运常数（Ktrans）、反流速率常数（kep）、血浆容积分数（vp）和血管外细胞外容积分数（ve）；骨髓组织液氮冷冻行1H HRMAS NMRS检查，病理学检查测定骨髓内脂肪含量及微血管密度（MVD）。结果 TBI组在X线照射前后各时间点DCE?MRI灌注参数Ktrans、kep、vp、ve值差异具有统计学意义，Ktrans值呈逐渐增加，在照射后第7天达到峰值；vp值呈逐渐减小，kep值照射后第4天减小为（0.360±0.049）/min（均P<0.01），第7天为（0.689±0.138）/min （P<0.01）；ve值照射后第4天增大（3.331±0.817，P<0.01），第7天与第4天无明显变化（P=0.355）。TBI组在X线照射前后各时间节点大鼠股骨骨髓的（n-3）PUFA、（n-6）PUFA及SAFA比例的差异有统计学意义，照射后骨髓（n-6）PUFA比例逐渐增加，在第7天达到最大，（n-3）PUFA比例逐渐减小，均P<0.01。TBI组大鼠骨髓照射后各时间节点Ktrans与（n-3）PUFA呈负相关（r=-0.6393，P<0.01）、与（n-6）PUFA呈正相关（r=0.6841，P<0.05）。结论 TBI后骨髓微循环灌注和微血管渗透性与脂肪含量存在相关性，骨髓微循环改变可能存在“脂肪?血管渗透性”病理生理机制。

abstractsObjective To investigate the relationship between microvascular permeability, contents of adipose and fatty acids as shown by quantitative permeability parameters of dynamic contrast?enhanced MRI(DCE?MRI)and ex vivo 1H high?resolution magic angle spinning nuclear magnetic resonance spectroscopy(1H HRMAS NMRS)in femoral bone marrow of rats after total body irradiation(TBI)by X?ray. Methods Thirty?six 6?to?8?week?old SD rats were randomly divided into the TBI group and control group(n=18 each). The TBI group rats received 6.0 Gy high energy X?ray TBI,whereas the control rats did not receive any irradiation. Before irradiation and on days 4 and 7 after irradiation,femur DCE?MRI perfusion imaging was used to measure the volume transfer constant (Ktrans),reflux rate constant (kep), plasma volume fraction(vp)and extravascular extracellular volume fraction(ve)of microvessels in femoral region of interest(ROI). The rat bone marrow tissue was frozen with liquid nitrogen and then examined with&nbsp;1H HRMAS NMRS. The adipose content and microvessel density(MVD)in the bone marrow were studied pathologically. Results Across all time points before and after X?ray irradiation,the TBI group showed significant changes in DCE?MRI perfusion parameters Ktrans,kep,vp and ve,the Ktrans value was increasing until peaking on day 7 after irradiation;the vp value appeared serially decreasing(all P<0.01);the kep value was reduced to 0.360 ± 0.049/min (P<0.01) on day 4 and to 0.689 ± 0.138/min on day 7 (P<0.01) after irradiation;the ve value increased to 3.331 ± 0.817 on day 7(P<0.01),and remained unchanged on day 7 after irradiation(P=0.355). Across all time points before and after X?ray irradiation,the TBI group also showed significant changes in proportions of(n-3)poly?unsaturated fatty acids(PUFA),(n-6)PUFA and saturated fatty acids(SAFA)in femoral bone marrow. After irradiation,the proportion of bone marrow(n-6) PUFA gradually increased until reaching the maximum on day 7,while the proportion of bone marrow(n-3) PUFA gradually decreased(all P<0.01). At all time points in the TBI rats,the Ktrans value was negatively correlated with(n-3)PUFA(r=-0.639 3,P<0.01),and positively correlated with(n-6)PUFA(r=0.684 1, P<0.05) of the bone marrow. Conclusion Bone marrow microcirculation and microvascular permeability may be correlated with adipose content after TBI. The changes in bone marrow microcirculation may be underlain by a pathophysiology mechanism based on fat?vascular permeability.