Shan Jing, Tucker Andrew W, Lee Yueh Z, Heath Michael D, Wang Xiaohui, Foos David H, Lu Jianping, Zhou Otto
Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Phys Med Biol. 2015 Jan 7;60(1):81-100. doi: 10.1088/0031-9155/60/1/81. Epub 2014 Dec 5.
Chest tomosynthesis is a low-dose, quasi-3D imaging modality that has been demonstrated to improve the detection sensitivity for small lung nodules, compared to 2D chest radiography. The purpose of this study is to investigate the feasibility and system requirements of stationary chest tomosynthesis (s-DCT) using a spatially distributed carbon nanotube (CNT) x-ray source array, where the projection images are collected by electronically activating individual x-ray focal spots in the source array without mechanical motion of the x-ray source, detector, or the patient. A bench-top system was constructed using an existing CNT field emission source array and a flat panel detector. The tube output, beam quality, focal spot size, system in-plane and in-depth resolution were characterized. Tomosynthesis slices of an anthropomorphic chest phantom were reconstructed for image quality assessment. All 75 CNT sources in the source array were shown to operate reliably at 80 kVp and 5 mA tube current. Source-to-source consistency in the tube current and focal spot size was observed. The incident air kerma reading per mAs was measured as 74.47 uGy mAs(-1) at 100 cm. The first half value layer of the beam was 3 mm aluminum. An average focal spot size of 2.5 × 0.5 mm was measured. The system MTF was measured to be 1.7 cycles mm(-1) along the scanning direction, and 3.4 cycles mm(-1) perpendicular to the scanning direction. As the angular coverage of 11.6°-34°, the full width at half maximum of the artifact spread function improved greatly from 9.5 to 5.2 mm. The reconstructed tomosynthesis slices clearly show airways and pulmonary vascular structures in the anthropomorphic lung phantom. The results show the CNT source array is capable of generating sufficient dose for chest tomosynthesis imaging. The results obtained so far suggest an s-DCT using a distributed CNT x-ray source array is feasible.
胸部断层合成是一种低剂量的准三维成像模式，与二维胸部X线摄影相比，已被证明可提高对小肺结节的检测灵敏度。本研究的目的是探讨使用空间分布碳纳米管（CNT）X射线源阵列进行静态胸部断层合成（s-DCT）的可行性和系统要求，其中通过电子激活源阵列中的各个X射线焦点来采集投影图像，而无需X射线源、探测器或患者进行机械运动。使用现有的CNT场发射源阵列和平板探测器构建了一个台式系统。对管输出、束流质量、焦点尺寸、系统平面内和深度分辨率进行了表征。重建了拟人化胸部模型的断层合成切片以进行图像质量评估。源阵列中的所有75个CNT源在80 kVp和5 mA管电流下均能可靠运行。观察到管电流和焦点尺寸在源与源之间具有一致性。在100 cm处测得每mAs的空气比释动能读数为74.47 μGy mAs⁻¹。束流的第一个半价层为3 mm铝。测得平均焦点尺寸为2.5×0.5 mm。系统调制传递函数（MTF）在扫描方向上测得为1.7周期/mm，垂直于扫描方向为3.4周期/mm。随着角度覆盖范围为11.6°-34°，伪影扩散函数的半高全宽从9.5 mm大幅提高到5.2 mm。重建的断层合成切片清晰显示了拟人化肺部模型中的气道和肺血管结构。结果表明，CNT源阵列能够为胸部断层合成成像产生足够的剂量。目前获得的结果表明，使用分布式CNT X射线源阵列的s-DCT是可行的。
