Wang Tianyuan, Inubushi Sachiko, Ikeo Naoko, Mukai Toshiji, Okumura Keisuke, Akasaka Hiroaki, Yada Ryuichi, Yoshida Kenji, Miyawaki Daisuke, Ishihara Takeaki, Nakaoka Ai, Sasaki Ryohei
Division of Radiation Oncology, Kobe University Graduate School of Medicine, 7-5-2 Kusunokicho, Chuouku, Kobe, Hyogo, 650-0017, Japan.
Department of Mechanical Engineering, Kobe University Graduate School of Engineering Faculty of Engineering, 1-1 Rokkodai-cho, Kobe, Hyogo, 657-8501, Japan.
Med Phys. 2020 Oct;47(10):4703-4710. doi: 10.1002/mp.14412. Epub 2020 Aug 20.
To develop a novel biocompatible solid fiducial marker that prevents radiopaque imaging artifacts and also maintains high imaging contrast for kilovoltage x-ray image-guided radiation therapy.
The fiducial marker was made of pure zinc. An in-house water-equivalent phantom was designed to evaluate artifacts and visibility under various simulated treatment scenarios. Image artifacts were quantitatively assessed in terms of the metal artifact index (MAI) on kilovoltage computed tomography (CT) and cone-beam CT (CBCT) scans. Marker visibility was evaluated on two types of kilovoltage planar x-ray images in terms of the contrast-to-background ratio (CBR). Comparisons with a conventional gold fiducial marker were conducted.
The use of zinc rather than a gold marker mitigates imaging artifacts. The MAI near the zinc marker decreased by 76, 79, and 77 % in CT, and by 77 (81), 74 (80), and 79 (85) % in CBCT full-fan (half-fan) scans, when using one-, two-, and three-marker phantom settings, respectively. The high-contrast part of the zinc marker exhibited CBRs above 2.00 for 28/32 exposures under four (lung, tissue, low-density bone, and high-density bone) different simulation scenarios, making its visibility comparable to that of the gold marker (30/32 exposures with CBRs > 2.00).
We developed a biocompatible, artifact-robust, and highly visible solid zinc fiducial marker. Although further evaluation is needed in clinical settings, our findings suggest its feasibility and benefits for kilovoltage x-ray image-guided radiation therapy.
开发一种新型生物相容性固体基准标记物，该标记物可防止产生不透射线的成像伪影，并在千伏级X射线图像引导放射治疗中保持高成像对比度。
基准标记物由纯锌制成。设计了一种内部水等效体模，以评估在各种模拟治疗场景下的伪影和可见性。通过千伏级计算机断层扫描（CT）和锥束CT（CBCT）扫描上的金属伪影指数（MAI）对图像伪影进行定量评估。根据对比度与背景比（CBR），在两种千伏级平面X射线图像上评估标记物的可见性。与传统的金基准标记物进行了比较。
使用锌标记物而非金标记物可减轻成像伪影。在使用一标记、两标记和三标记体模设置时，锌标记物附近的MAI在CT中分别降低了76%、79%和77%，在CBCT全扇区（半扇区）扫描中分别降低了77（81）%、74（80）%和79（85）%。在四种（肺、组织、低密度骨和高密度骨）不同模拟场景下，锌标记物的高对比度部分在28/32次曝光中CBR高于2.00，其可见性与金标记物相当（30/32次曝光，CBR>2.00）。
我们开发了一种生物相容性好、抗伪影且可见性高的固体锌基准标记物。尽管需要在临床环境中进行进一步评估，但我们的研究结果表明了其在千伏级X射线图像引导放射治疗中的可行性和优势。
