Imaging Department, Institut Gustave Roussy, Villejuif, France.
Ultraschall Med. 2010 Aug;31(4):370-8. doi: 10.1055/s-0029-1245450. Epub 2010 Jun 24.
This study is intended to compare the value of uncompressed ultrasonic data, obtained after linear power detection of the ultrasonic radiofrequencies that we call linear data, with usual compressed video data for the quantification of tumor perfusion, particularly for monitoring antivascular therapy.
To form a clinically useful ultrasonic image, the detected power of the received signals (linear data) is compressed in a quasi-logarithmic fashion in order to match the limited dynamic range of the video monitor. The resulting reduced range of signals from an injected contrast agent may limit the sensitivity to changes in the time-intensity curves. Following a theoretical evaluation of the effects of compression on time-intensity curves and as an in vivo example, we measured at different times the effects of an antivascular drug administered to mice bearing melanoma tumors. The mean time-intensity curves within the tumors after bolus injection of a contrast agent were determined using both linear and video data. Linearized data was recovered using the inverse of the true scanner's compression law, which was experimentally determined. Three features were extracted from the time-intensity curves: peak intensity (PI), time to peak intensity (TPI) and area under the curve in the wash-in phase (AUC (wash-in)). When contrast reached its maximum value, the coefficient of variation reflecting the heterogeneity of the intensity of contrast uptake within the tumor, was computed using both data sets.
TPI was found to be similar with either data set (r = 0.98, p < 0.05, factor of 1.09). Linear PI and AUC (wash-in) had significantly earlier decreases after drug administration than video data (p = 0.015 and p = 0.03, respectively). The coefficient of variation was significantly lower when using video rather than linear data (p < 10 (-4)).
In conclusion, the use of linear data is the only mathematically valid methodology for determining a tumor's time-intensity curve and, in practice, it allows earlier demonstration of responses to antivascular drugs.
本研究旨在比较未经压缩的超声数据（通过线性功率检测超声射频获得，我们称之为线性数据）与常规压缩视频数据在肿瘤灌注定量中的价值，特别是在监测抗血管治疗方面。
为了形成有临床应用价值的超声图像，接收到的信号（线性数据）的检测功率被以准对数方式压缩，以匹配视频监视器的有限动态范围。这导致从注射对比剂的信号幅度减小，可能限制了对时间-强度曲线变化的敏感性。在对压缩对时间-强度曲线的影响进行理论评估并作为体内实例后，我们在不同时间测量了抗血管药物对携带黑色素瘤肿瘤的小鼠的影响。使用线性和视频数据来确定在对比剂团注后肿瘤内的平均时间-强度曲线。线性化数据使用通过实验确定的真实扫描仪压缩律的逆来恢复。从时间-强度曲线中提取了三个特征：峰值强度（PI）、达峰时间（TPI）和洗入相下的曲线下面积（AUC（洗入））。当对比度达到最大值时，使用两个数据集计算反映肿瘤内对比度摄取强度异质性的变异系数。
发现 TPI 与两种数据集均相似（r = 0.98，p < 0.05，因子为 1.09）。线性 PI 和 AUC（洗入）在药物给药后比视频数据更早地下降（p = 0.015 和 p = 0.03）。使用视频数据而不是线性数据时，变异系数显著降低（p < 10（-4））。
总之，使用线性数据是确定肿瘤时间-强度曲线的唯一数学上有效的方法，实际上，它可以更早地显示对抗血管药物的反应。
