Department of Neurosurgery, University of New Mexico, 1101 Yale Blvd, Domenici Hall, BRaIN Center Rm. 1131B, Albuquerque, NM, 87106, USA,
Transl Stroke Res. 2012 Sep;3(3):369-74. doi: 10.1007/s12975-012-0193-6. Epub 2012 May 30.
Computerized tomography (CT) is the most often used imaging modality in the evaluation of acute clinical stroke. However, the rapidity with which CT density changes occur after acute, severe, focal ischemia cannot be determined clinically. Even if the time of symptom onset is known, clinical stroke severity is highly variable. We studied the time course of CT density change after severe, rapid onset, acute, focal ischemia as documented by stable xenon CT cerebral blood flow (CBF) in monkeys. Eight monkeys (Macaca mulatta) were subjected to transorbital occlusion of the left posterior cerebral, anterior, middle, and internal carotid arteries to induce focal ischemia. CT density Hounsfield units (HU), CBF by stable xenon CT, arterial blood pressure, and blood gases were measured before occlusion, immediately after occlusion, at 30 min, and hourly for up to 6 h. Occlusion of the cerebral arteries decreased CBF to 8 ± 5 ml/100 g/ min within 15 min postocclusion. At 6 h, CBF was unchanged at 9 ± 4 ml/100 g/ min. CT density within the ischemic core fell from 42 to 38 HU immediately after occlusion (P < 0.05), rose transiently, then fell at 2 h (P < 0.01) and plateaued at 36 ± 5 HU for a total decrease of 4-5 HU between 4 and 6 h poststroke. Changes in CT density lag severe focal ischemia by 2 h. Thus, when CT hypodensity is seen in acute stroke, it is likely 2 h old. It also provides an explanation for the phenomenon of clinical CT mismatch with clinical deficits and normal CT.
计算机断层扫描（CT）是评估急性临床中风最常用的成像方式。然而，急性、严重、局灶性缺血后 CT 密度变化的速度无法在临床上确定。即使知道症状发作的时间，临床中风的严重程度也高度可变。我们研究了稳定氙 CT 脑血流（CBF）在猴子中记录的严重、快速发作、急性、局灶性缺血后 CT 密度变化的时间过程。8 只猴子（猕猴）接受眶内左侧大脑后、前、中和颈内动脉闭塞以诱导局灶性缺血。在闭塞前、闭塞后立即、30 分钟和每小时测量 CT 密度亨氏单位（HU）、稳定氙 CT 的 CBF、动脉血压和血气。大脑动脉闭塞在闭塞后 15 分钟内将 CBF 降低至 8±5ml/100g/min。6 小时时，CBF 保持在 9±4ml/100g/min。缺血核心内的 CT 密度在闭塞后立即从 42 降至 38HU（P<0.05），短暂升高，然后在 2 小时时下降（P<0.01），并在 36±5HU 处达到平台，在 4 至 6 小时之间总下降 4-5HU。CT 密度的变化比严重局灶性缺血滞后 2 小时。因此，在急性中风中看到 CT 低密时，它可能已经存在 2 小时了。它还解释了临床 CT 与临床缺损和正常 CT 不匹配的现象。
