Departments of Radiology, Massachusetts General Hospital, Boston, Massachusetts, USA.
AJNR Am J Neuroradiol. 2011 Oct;32(9):1688-96. doi: 10.3174/ajnr.A2586. Epub 2011 Aug 11.
Recently introduced fpVCT scanners can capture volumetric (4D) time-varying projections enabling whole-organ dynamic CTA imaging. The main objective of this study was to assess the temporal resolution of dynamic CTA in discriminating various phases of rapid and slow time-dependent neurovascular pathologies in animal models.
Animal models were created to assess phasic blood flow, subclavian steal phenomena, saccular aneurysms, and neuroperfusion under protocols approved by the SRAC. Animals with progressively increasing heart rate-Macaca sylvanus (100 bpm), Oryctolagus cuniculus (NZW rabbit) (150 bpm), Rattus norvegicus (300 bpm), Mus musculus (500 bpm)-were imaged to challenge the temporal resolution of the system. FpVCT, a research prototype with a 25 × 25 × 18 cm coverage, was used for dynamic imaging with the gantry rotation time varying from 3 to 5 seconds. Volumetric datasets with 50% temporal overlap were reconstructed; 4D datasets were analyzed by using the Leonardo workstation.
Dynamic imaging by using fpVCT was capable of demonstrating the following phenomena: 1) subclavian steal in rabbits (ΔT ≅ 3-4 seconds); 2) arterial, parenchymal, and venous phases of blood flow in mice (ΔT ≅ 2 seconds), rabbits (ΔT ≅ 3-4 seconds), and Macaca sylvanus (ΔT ≅ 3-4 seconds); 3) sequential enhancement of the right and left side of the heart in Macaca sylvanus and white rabbits (ΔT ≅ 2 seconds); and 4) different times of the peak opacification of cervical and intracranial arteries, venous sinuses, and the jugular veins in these animals (smallest, ΔT ≅ 1.5-2 seconds). The perfusion imaging in all animals tested was limited due to the fast transit time through the brain and the low contrast resolution of fpVCT.
Dynamic imaging by using fpVCT can distinguish temporal processes separated by >1.5 seconds. Neurovascular pathologies with a time constant >1.5 seconds can be evaluated noninvasively by using fpVCT.
最近推出的 fpVCT 扫描仪可以捕获容积（4D）时变投影，实现整个器官的动态 CTA 成像。本研究的主要目的是评估动态 CTA 在区分动物模型中快速和缓慢时变神经血管病变的各个阶段方面的时间分辨率。
动物模型的创建是为了评估相位血流、锁骨下盗血现象、囊状动脉瘤和神经灌注，这些都是在 SRAC 批准的方案下进行的。使用逐渐增加心率的动物模型（Macaca sylvanus100 bpm）、Oryctolagus cuniculus（NZW 兔）150 bpm）、Rattus norvegicus300 bpm）、Mus musculus500 bpm）进行成像，以挑战系统的时间分辨率。使用研究原型 fpVCT 进行动态成像，其龙门架旋转时间从 3 秒到 5 秒不等。重建了具有 50%时间重叠的容积数据集；使用 Leonardo 工作站分析 4D 数据集。
使用 fpVCT 进行的动态成像能够显示以下现象：1）兔子的锁骨下盗血（ΔT≈3-4 秒）；2）老鼠（ΔT≈2 秒）、兔子（ΔT≈3-4 秒）和 Macaca sylvanus（ΔT≈3-4 秒）的动脉、实质和静脉血流相位；3）Macaca sylvanus 和白色兔子左右心的顺序增强（ΔT≈2 秒）；4）这些动物颈内动脉、颅内动脉、静脉窦和颈静脉显影峰值时间不同（最小的，ΔT≈1.5-2 秒）。由于脑通过时间快和 fpVCT 的低对比度分辨率，所有测试动物的灌注成像均受到限制。
使用 fpVCT 进行的动态成像可以区分相隔>1.5 秒的时间过程。使用 fpVCT 可以非侵入性地评估时间常数>1.5 秒的神经血管病变。
