Department of Stereotactic and Functional Neurosurgery, University Hospital of Cologne, Cologne, 50924, Germany.
Department of Neurology, University Hospital of Cologne, Cologne, 50924, Germany.
Med Phys. 2017 Sep;44(9):4463-4473. doi: 10.1002/mp.12424. Epub 2017 Jul 20.
Orientating the angle of directional leads for deep brain stimulation (DBS) in an axial plane introduces a new degree of freedom that is indicated by embedded anisotropic directional markers. Our aim was to develop algorithms to determine lead orientation angles from computed tomography (CT) and stereotactic x-ray imaging using standard clinical protocols, and subsequently assess the accuracy of both methods.
In CT the anisotropic marker artifact was taken as a signature of the lead orientation angle and analyzed using discrete Fourier transform of circular intensity profiles. The orientation angle was determined from phase angles at a frequency 2/360° and corrected for aberrations at oblique leads. In x-ray imaging, frontal and lateral images were registered to stereotactic space and sub-images containing directional markers were extracted. These images were compared with projection images of an identically located virtual marker at different orientation angles. A similarity index was calculated and used to determine the lead orientation angle. Both methods were tested using epoxy phantoms containing directional leads (Cartesia™, Boston Scientific, Marlborough, USA) with known orientation. Anthropomorphic phantoms were used to compare both methods for DBS cases.
Mean deviation between CT and x-ray was 1.5° ± 3.6° (range: -2.3° to 7.9°) for epoxy phantoms and 3.6° ± 7.1° (range: -5.6° to 14.6°) for anthropomorphic phantoms. After correction for imperfections in the epoxy phantoms, the mean deviation from ground truth was 0.0° ± 5.0° (range: -12° to 14°) for x-ray. For CT the results depended on the polar angle of the lead in the scanner. Mean deviation was -0.3° ± 1.9° (range: -4.6° to 6.6°) or 1.6° ± 8.9° (range: -23° to 34°) for polar angles ≤ 40° or > 40°.
The results show that both imaging modalities can be used to determine lead orientation angles with high accuracy. CT is superior to x-ray imaging, but oblique leads (polar angle > 40°) show limited precision due to the current design of the directional marker.
在轴面中为脑深部刺激（DBS）定向引导头的角度引入了一个新的自由度，该自由度由嵌入式各向异性定向标记指示。我们的目的是开发使用标准临床方案从计算机断层扫描（CT）和立体定向 X 射线成像确定导联方向角度的算法，然后评估这两种方法的准确性。
在 CT 中，各向异性标记伪影被用作导联方向角度的特征，并使用圆形强度分布的离散傅立叶变换进行分析。方位角是从频率为 2/360°的相位角确定的，并对斜导进行了像差校正。在 X 射线成像中，将正面和侧面图像注册到立体空间，并提取包含定向标记的子图像。将这些图像与不同方向角度的相同位置虚拟标记的投影图像进行比较。计算相似指数并用于确定导联方向角度。使用具有已知方向的定向导联的环氧树脂体模（波士顿科学公司，马萨诸塞州，美国）测试了这两种方法。使用拟人化体模来比较 DBS 病例的这两种方法。
环氧树脂体模的 CT 和 X 射线之间的平均偏差为 1.5°±3.6°（范围：-2.3°至 7.9°），拟人化体模的平均偏差为 3.6°±7.1°（范围：-5.6°至 14.6°）。在对环氧树脂体模的不完美进行校正后，X 射线的真实值平均偏差为 0.0°±5.0°（范围：-12°至 14°）。对于 CT，结果取决于导丝在扫描仪中的极角。对于极角≤40°或>40°的导丝，平均偏差为-0.3°±1.9°（范围：-4.6°至 6.6°）或 1.6°±8.9°（范围：-23°至 34°）。
结果表明，两种成像方式都可以高精度地确定导联方向角度。CT 优于 X 射线成像，但由于定向标记的当前设计，斜导（极角>40°）的精度有限。
