应用反向滤过及迭代重建方法评估标准放射剂量与低剂量颈椎CT图像质量的对比研究

Comparison of Image Quality of the Cervical Spine between Standard-Dose and Low-Dose Protocol Using Filtered Back-Projection and Iterative Recyustruction Using Computed Tomography

目的:利用反向滤过重建(filtered back-projection,FBP)及迭代重建(iterative reconstruction,IR)方法评估标准剂量及低剂量对颈椎CT图像质量的影响。方法:40例受检对象行颈椎CT检查,将其随机分为两组:标准剂量组(SD,120 kVp,275 mAs)及低剂量组(LD,120 kVp,150 mAs),随机选择管电流值,所有数据均行FBP及IR重建。测量C3 C4及C6 C7椎间盘水平椎间盘、脊神经、脊髓、韧带以及周围软组织的图像噪声值(Image noise,IN),信噪比(signal-to-noise,SNR)及对比信噪比(contrast-to-noise,CNR)。结果:在测量的各椎间盘水平,迭代重建的信噪比及对比噪声比要明显高于反向滤过重建方法,并有效的降低了图像噪声。低剂量迭代重建图像与标准剂量反向滤过图像相比无明显统计学意义。排除剂量及扫描层面的影响,椎间盘、脊神经及韧带的图像质量,迭代重建评分要明显高于反向滤过重建,结果具有统计学差异;而低剂量迭代重建图像质量评分与标准剂量反向滤过重建相比无明显差异。软组织及椎体的图像质量,迭代重建图像质量评分要低于反向滤过重建方法,结果具有统计学差异;而低剂量迭代重建图像质量评分与标准剂量反向滤过重建相比无明显差异。整体病例图像质量评分,迭代重建方法要高于反向滤过重建方法,低剂量迭代重建方法要高于标准剂量反向滤过重建方法。结论:应用低剂量扫描方式以及迭代重建方法进行颈椎CT检查可以为临床提供较好的图像质量,对于椎间盘、脊神经、脊髓显示较好,对于周围软组织以及椎体来说,图像质量相对较差,同时可以降低大约40%的放射剂量。

Objective： To compare the image quality of a standard-dose （SD） and a low-dose （LD） cervical spine CT protocol using filtered back-projection （FBP） and iterative reconstruction （IR）. Methods： 40 patients investigated by cervical spine CT were prospectively randomized into two groups： SD （120 kVp, 275 mAs） and LD （120 kVp, 150 mAs）, both applying automatic tube current modulation. Data were reconstructed using both FBP and sinogram affirmed IR. Image noise, signal-to-noise （SNR） and contrast-to-noise （CNR） ratios were measured. At C3-C4 and C6-C7 levels, we used a four-point scale： intervertebral disc, content of neural foramina and dural sac, ligaments, soft tissues and vertebrae. They subsequently rated overall image quality using a ten point scale. Results： For both protocols and at each disc level, IR significantly decreased image noise and increased SNR and CNR, compared with FBP. SNR and CNR were statistically equivalent in LD-IR and SD-FBP protocols. Regardless of the dose and disc level, the qualitative scores with IR compared with FBP, and with LD- IR compared with SD-FBP, were significantly higher or not statistically different for intervertebral discs, neural foramina and ligaments, while significantly lower or not statistically different for soft tissues and vertebrae. The overall image quality scores were significantly higher with IR compared with FBP, and with LD-1R compared with SD-FBP. Conehtsion： LD-IR cervical spine CT provides better image quality for intervertebral discs, neural foramina and ligaments, and worse image quality for soft tissues and vertebrae, compared with SD-FBP, while reducing radiation dose by approximately 40 %.