Andersen C, Astrup J, Gyldensted C
Department of Neurosurgery, Skejby University Hospital, Denmark.
J Comput Assist Tomogr. 1994 Jul-Aug;18(4):509-18. doi: 10.1097/00004728-199407000-00001.
The purpose of our study was to quantify peritumoral brain edema (PTE) in vivo using NMR relaxation time imaging, as the longitudinal relaxation time T1 is proportional to tissue water content, and to use the method for monitoring the effects of glucocorticoids (GCCs) on PTE in brain tumor patients as a function of time.
Relaxation time imaging (T1 maps) was done on a 1.5 T MR scanner on 23 brain tumor patients [13 cerebral metastases (METs), 10 intracranial meningiomas (MMs), and 9 benign and 1 anaplastic MM] before, and 1, 3, and 7 days after initiation of GCC treatment (dexamethasone 0.26-0.64 mg/kg bw). In addition, 7 patients were studied for 14-63 days of treatment. Imaging analysis included mean T1 of the edema area as a function of time, and an image histogram evaluation technique, which measures 50% of the edema area, where T1 is highest (corresponding to the highest water content of the area), termed the "super-edema." Using a conversion equation, mean T1 in the edema area was recalculated into a percent of tissue water content.
After 7 days of GCC treatment total edema area was reduced by 10.3% in the MET patients. The average reduction in mean T1 was 4.6% after 24 h of treatment and 13.5% after 7 days. Expressed in terms of percent tissue water content, the average edema resorption rate in the MET patients was 0.4 +/- 0.1% H2O/day (p < 0.02). Super-edema area was reduced by 64% after 7 days (p < 0.0001). None of the benign MMs responded to GCC treatment, either in edema size or in mean T1, unlike the anaplastic type, in which there was a response comparable to that in the MET patients. The effect of GCCs in up to 63 days of treatment is demonstrated. It is shown that after 40-63 days of GCC treatment, PTE water content is close to the upper normal range for white matter.
PTE is heterogeneous in terms of the spatial distribution of T1 and, thereby, water content. GCCs reduce T1 in PTE around cerebral metastases significantly after a few days of treatment, possibly through a mechanism that reduces edema production below the level of edema resorption. PTE surrounding benign MM was not affected by GCC treatment, contrary to one anaplastic MM, which leads to the speculation that malignant tumors may produce substances that are affected by GCCs and are prerequisites for a GCC effect. Significant reductions in the highest T1 area (super-edema area) were observed after 24 h of treatment. The anti-edema effect of GCC may last at least 63 days. A lower dose-dependent threshold for the effect seems to exist. The possible mechanisms of actions of the GCCs on PTE are discussed.
我们研究的目的是利用核磁共振弛豫时间成像在体内定量肿瘤周围脑水肿（PTE），因为纵向弛豫时间T1与组织含水量成正比，并使用该方法监测糖皮质激素（GCCs）对脑肿瘤患者PTE的影响随时间的变化。
在23例脑肿瘤患者[13例脑转移瘤（METs）、10例颅内脑膜瘤（MMs），其中9例为良性，1例为间变性MM]开始GCC治疗（地塞米松0.26 - 0.64mg/kg体重）前、治疗后1天、3天和7天，使用1.5T磁共振扫描仪进行弛豫时间成像（T1图谱）。此外，对7例患者进行了14 - 63天的治疗研究。成像分析包括水肿区域的平均T1随时间的变化，以及一种图像直方图评估技术，该技术测量水肿区域的50%，此处T1最高（对应于该区域最高的含水量），称为“超级水肿”。使用转换方程，将水肿区域的平均T1重新计算为组织含水量的百分比。
GCC治疗7天后，MET患者的总水肿面积减少了10.3%。治疗24小时后平均T1平均降低4.6%，7天后降低13.5%。以组织含水量百分比表示，MET患者的平均水肿吸收速率为0.4±0.1% H2O/天（p<0.02）。7天后超级水肿面积减少了64%（p<0.0001）。与间变性MM不同，良性MM在水肿大小或平均T1方面对GCC治疗均无反应，间变性MM的反应与MET患者相当。展示了GCCs在长达63天治疗中的效果。结果表明，GCC治疗40 - 63天后，PTE含水量接近白质的正常上限范围。
PTE在T1的空间分布以及含水量方面存在异质性。GCC治疗几天后可显著降低脑转移瘤周围PTE的T1，可能是通过一种将水肿产生降低至低于水肿吸收水平的机制。与1例间变性MM相反，良性MM周围的PTE不受GCC治疗影响，这引发了一种推测，即恶性肿瘤可能产生受GCCs影响的物质，这些物质是GCCs发挥作用的前提条件。治疗24小时后观察到最高T1区域（超级水肿区域）显著减少。GCC的抗水肿作用可能至少持续63天。似乎存在较低的剂量依赖性效应阈值。讨论了GCCs对PTE的可能作用机制。
