Research & Development Centre, Bharathiar University, Coimbatore, Tamil Nadu, India.
Department of Radiation Oncology, Yashoda Hospitals, Hyderabad, Telangana, India.
Radiol Med. 2021 Jan;126(1):106-116. doi: 10.1007/s11547-020-01208-9. Epub 2020 Apr 29.
To study the accuracy of deformable registration algorithm for CT and cone beam CT (CBCT) using a combination of physical and digital phantoms.
The physical phantoms consisted of objects over a range of electron densities, shape and sizes. The system was tested for simple and complex scenarios including performance in the presence of metallic artefacts. Clinically present deformations were simulated using a set of five geometric and anatomic virtual phantoms.
The system could not account for large changes in size, shape and Hounsfield units. Deformations of low intensity structures and small objects were highly inaccurate, and errors were prominent for volume reduction scenario than volume growth. The presence of artefacts did alter the performance of the algorithm. Objects of low density and that close to artefacts were affected the most. Overall, deformations to CBCT were poor. In virtual phantoms, the system could not handle gas pockets and deformation errors in inverse direction were higher than that in forward direction.
The algorithm was tested for several non-clinical and clinical scenarios. The performance was acceptable for realistic and clinically present deformations. However, it is necessary to tread cautiously for structures with small volumes and large reductions in volume.
使用物理和数字体模的组合来研究 CT 和锥形束 CT（CBCT）的变形配准算法的准确性。
物理体模由一系列具有不同电子密度、形状和大小的物体组成。该系统针对简单和复杂场景进行了测试，包括存在金属伪影时的性能。使用一组五个几何和解剖虚拟体模来模拟临床存在的变形。
该系统无法适应大小、形状和 Hounsfield 单位的较大变化。低强度结构和小物体的变形非常不准确，体积减小的场景比体积增大的场景误差更为明显。伪影的存在确实改变了算法的性能。低密度和靠近伪影的物体受到的影响最大。总体而言，CBCT 的变形效果较差。在虚拟体模中，该系统无法处理气腔，反向变形误差高于正向变形误差。
该算法针对多种非临床和临床场景进行了测试。对于现实和临床存在的变形，其性能是可以接受的。然而，对于体积较小且体积大量减少的结构，需要谨慎处理。
