Department of Engineering and Applied Physics, University of Science and Technology of China, Hefei, Anhui, People's Republic of China.
Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China.
Med Phys. 2024 Oct;51(10):7320-7331. doi: 10.1002/mp.17274. Epub 2024 Jul 10.
Cone beam CT (CBCT) is widely utilized in clinics. However, the scatter artifact degrades the CBCT image quality, hampering the expansion of CBCT applications. Recently, beam-blocker methods have been used for CBCT scatter correction and proved their high cost-effectiveness.
A rotating beam-blocker (RBB) method for CBCT scatter correction was proposed to complete scatter correction and image reconstruction within a single scan in both full- and half-fan scan scenarios.
The RBB consisted of two open regions and two blocked regions, and was designed as a centrosymmetric structure. The open and blocked projections could be alternatively obtained within one single rotation. The open projections were corrected with the scatter signal calculated from the blocked projections, and then used to reconstruct the 3D image via the Feldkamp-Davis-Kress algorithm. The performance of the RBB method was evaluated on head and pelvis phantoms in scenarios with and without a bowtie filter. The images obtained from nine repeated scans in each scenario were used to calculate the evaluation metrics including the CT number error, spatial nonuniformity (SNU) and contrast-to-noise ratio (CNR).
For the head phantom, the CT number error was decreased to <5 after scatter correction from >200 HU before correction when scanned without a bowtie filter, and to <4 from >160 HU when scanned with a full bowtie filter. For the pelvis phantom, the CT number error was reduced to <12 after scatter correction from >250 HU before correction when scanned without a bowtie filter, and to <10 from >190 HU when scanned with a half bowtie filter. After scatter correction, the uniformity and contrast were both improved, resulting in an SNU of >79% decrease and CNR of >2 times increase, respectively.
High-quality CBCT images could be obtained in a single scan after using the proposed RBB method for scatter correction, enabling more accurate image guidance for surgery and radiation therapy applications. With almost no time delay between the successive open and blocked projections, the RBB method could eliminate the motion-induced anatomical mismatches between the corresponding open and blocked projections and could find particular usefulness in thoracic and abdominal imaging.
锥形束 CT（CBCT）在临床上得到了广泛应用。然而，散射伪影降低了 CBCT 的图像质量，限制了 CBCT 的应用拓展。最近，束阻挡器方法已被用于 CBCT 散射校正，并证明其具有很高的成本效益。
提出了一种用于 CBCT 散射校正的旋转束阻挡器（RBB）方法，以在全扇区和半扇区扫描中完成单次扫描内的散射校正和图像重建。
RBB 由两个开放区域和两个阻挡区域组成，设计为中心对称结构。在单个旋转过程中，可以交替获取开放和阻挡的投影。使用从阻挡投影计算出的散射信号对开放投影进行校正，然后通过 Feldkamp-Davis-Kress 算法重建 3D 图像。在带有和不带有 Bowtie 滤波器的头模和骨盆模体的场景中评估 RBB 方法的性能。在每个场景的九次重复扫描中获得的图像用于计算评估指标，包括 CT 值误差、空间不均匀性（SNU）和对比噪声比（CNR）。
对头模，在没有 Bowtie 滤波器扫描时，校正前 CT 值误差从>200 HU 降至<5，校正前 CT 值误差从>160 HU 降至<4；在使用全 Bowtie 滤波器扫描时，校正前 CT 值误差从>250 HU 降至<12，校正前 CT 值误差从>190 HU 降至<10。在散射校正后，均匀性和对比度都得到了改善，SNU 降低了>79%，CNR 提高了>2 倍。
使用提出的 RBB 方法进行散射校正后，单次扫描即可获得高质量的 CBCT 图像，为手术和放射治疗应用提供更准确的图像引导。由于连续开放和阻挡投影之间几乎没有时间延迟，RBB 方法可以消除相应的开放和阻挡投影之间的运动引起的解剖不匹配，并在胸部和腹部成像中具有特殊的用途。
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