Department of Neurosurgery, University of Halle-Wittenberg, Halle, Germany.
J Neurosurg. 2011 Feb;114(2):394-9. doi: 10.3171/2010.5.JNS10307. Epub 2010 Jun 4.
Efficacy of radiosurgery in vestibular schwannoma (VS) is usually documented by changes of tumor size and by loss of contrast enhancement in MR imaging within the central portion of the lesion. Until now, however, correlation between contrast enhancement and timing of image acquisition in nontreated VS has not been analyzed systematically. The authors undertook this study to investigate changes in contrast enhancement with respect to latency of image acquisition after contrast agent administration.
The dynamics of contrast medium uptake were evaluated with T1-weighted VIBE MR imaging sequences performed immediately and 1.5, 3.5, 4.5, 9.5, and 11.5 minutes after administration of single dose of Gd in 21 patients with nontreated medium- to large-sized VSs. Signal-to-noise (SNR) and contrast-to-noise ratio (CNR) of tumors were evaluated, and volumes of central nonenhancing areas (NEAs) were determined.
The interior appearance of the tumors changed considerably over time. The NEA significantly diminished in size (p < 0.0001, Friedman test) and almost completely disappeared in all but 2 patients. Compared to images at 1.5 minutes, NEA volumes decreased to a median of 36% at 3.5 minutes and 34% at 4.5 minutes, showing smaller changes after that-9% at 9.5 minutes and 3% at 11.5 minutes. Tumor SNR and CNR increased over time. The maximum change in the median values for SNR and CNR were a 72% increase and 117% increase, respectively; both occurred at 1.5 minutes after Gd administration.
Contrast enhancement in VS MR imaging varies according to the duration of the delay between contrast agent administration and image acquisition. Postradiotherapy changes in contrast enhancement of VS can therefore not be attributed only to effective radiotherapy. So-called "loss of central contrast enhancement" may be falsely detected because of timing. A standardized protocol with defined timing of image acquisition may increase comparability of contrast uptake in VS.
在磁共振成像（MR）中，通过肿瘤大小的变化和病变中央部分对比增强的丧失来评估听神经鞘瘤（VS）的放射外科治疗效果。然而，到目前为止，尚未对未经治疗的 VS 患者的对比增强与图像采集时间之间的相关性进行系统分析。本研究旨在探讨对比剂给药后延迟采集图像时对比增强的变化。
对 21 例未经治疗的中大型 VS 患者，在单次 Gd 给药后即刻及 1.5、3.5、4.5、9.5 和 11.5 分钟，采用 T1 加权容积内插扰相梯度回波（VIBE）MR 成像序列评估对比剂摄取的动力学。评估肿瘤的信噪比（SNR）和对比噪声比（CNR），并确定中央无增强区（NEA）的体积。
肿瘤的内部外观随时间发生了很大的变化。NEA 显著缩小（p < 0.0001，Friedman 检验），除 2 例患者外，几乎完全消失。与 1.5 分钟时的图像相比，NEA 体积在 3.5 分钟时降至中位数的 36%，在 4.5 分钟时降至 34%，此后变化较小-在 9.5 分钟时减少 9%，在 11.5 分钟时减少 3%。肿瘤 SNR 和 CNR 随时间增加。SNR 和 CNR 的中位数最大变化分别为增加 72%和增加 117%，均发生在 Gd 给药后 1.5 分钟。
VS 磁共振成像中的对比增强取决于对比剂给药与图像采集之间的延迟时间。因此，VS 对比增强的放疗后变化不能仅归因于有效的放疗。由于时间因素，可能会错误地检测到所谓的“中央对比增强丧失”。具有定义的图像采集时间的标准化方案可能会提高 VS 对比剂摄取的可比性。
