Department of Radiology, The Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital (NKI-AVL), P.O. Box 90203, 1006 BE Amsterdam, The Netherlands.
Med Phys. 2010 Jun;37(6):2617-26. doi: 10.1118/1.3429048.
The aim of this study was to investigate the feasibility of image-guided navigation approaches to demarcate breast cancer on the basis of preacquired magnetic resonance (MR) imaging in supine patient orientation.
Strategies were examined to minimize the uncertainty in the instrument-tip position, based on the hypothesis that the release of instrument pressure returns the breast tissue to its predeformed state. For this purpose, four sources of uncertainty were taken into account: (1) U(ligaments): Uncertainty in the reproducibility of the internal mammary gland geometry during repeat patient setup in supine orientation; (2) U(r_breathing): Residual uncertainty in registration of the breast after compensation for breathing motion using an external marker; (3) U(reconstruction): Uncertainty in the reconstructed location of the tip of the needle using an optical image-navigation system (phantom experiments, n = 50); and (4) U(deformation): Uncertainty in displacement of breast tumors due to needle-induced tissue deformations (patients, n = 21). A Monte Carlo study was performed to establish the 95% confidence interval (CI) of the combined uncertainties. This region of uncertainty was subsequently visualized around the reconstructed needle tip as an additional navigational aid in the preacquired MR images. Validation of the system was performed in five healthy volunteers (localization of skin markers only) and in two patients. In the patients, the navigation system was used to monitor ultrasound-guided radioactive seed localization of breast cancer. Nearest distances between the needle tip and the tumor boundary in the ultrasound images were compared to those in the concurrently reconstructed MR images.
Both U(reconstruction) and U(deformation) were normally distributed with 0.1 +/- 1.2 mm (mean +/- 1 SD) and 0.1 +/- 0.8 mm, respectively. Taking prior estimates for U(ligaments) (0.0 +/- 1.5 mm) and U(r_breathing) (-0.1 +/- 0.6 mm) into account, the combined impact resulted in 3.9 mm uncertainty in the position of the needle tip (95% CI) after release of pressure. The volunteer study showed a targeting accuracy comparable to that in the phantom experiments: 2.9 +/- 1.3 versus 2.7 +/- 1.1 mm, respectively. In the patient feasibility study, the deviations were within the 3.9 mm CI.
Image-guided navigation to demarcate breast cancer on the basis of preacquired MR images in supine orientation appears feasible if patient breathing is tracked during the navigation procedure, positional uncertainty is visualized and pressure on the localization instrument is released prior to verification of its position.
本研究旨在探讨基于仰卧位患者预先采集的磁共振（MR）图像，通过影像引导导航方法来划定乳腺癌边界的可行性。
基于以下假设，即松开仪器压力会使乳房组织恢复到预先变形的状态，从而检查了最小化仪器尖端位置不确定性的策略。为此，考虑了四个不确定性源：（1）U（韧带）：仰卧位重复患者设置过程中内部乳腺几何形状的可重复性不确定性；（2）U（呼吸）：使用外部标记补偿呼吸运动后，乳房注册的残余不确定性；（3）U（重建）：使用光学图像导航系统（体模实验，n=50）重建针尖位置的不确定性；（4）U（变形）：由于针诱导的组织变形，乳房肿瘤的位移不确定性（患者，n=21）。进行了蒙特卡罗研究以建立组合不确定性的 95%置信区间（CI）。随后，在预先采集的 MR 图像中，将该不确定性区域可视化作为附加的导航辅助工具，以围绕重建后的针尖。该系统在五名健康志愿者（仅定位皮肤标记）和两名患者中进行了验证。在患者中，导航系统用于监测超声引导放射性种子定位乳腺癌。将超声图像中针尖和肿瘤边界之间的最近距离与同时重建的 MR 图像中的距离进行了比较。
U（重建）和 U（变形）均呈正态分布，分别为 0.1 +/- 1.2 毫米（均值 +/- 1 SD）和 0.1 +/- 0.8 毫米。考虑到 U（韧带）（0.0 +/- 1.5 毫米）和 U（呼吸）（-0.1 +/- 0.6 毫米）的先前估计，压力释放后，针尖位置的组合影响导致 3.9 毫米的不确定性（95%CI）。志愿者研究表明，与体模实验相比，靶向精度相当：分别为 2.9 +/- 1.3 毫米和 2.7 +/- 1.1 毫米。在患者可行性研究中，偏差在 3.9 毫米 CI 内。
如果在导航过程中跟踪患者呼吸，可视化位置不确定性，并在验证定位仪器位置之前释放定位仪器的压力，则基于仰卧位患者预先采集的 MR 图像进行图像引导导航来划定乳腺癌边界似乎是可行的。
