尸体头颅低剂量光子计数CT颞骨图像质量评估

文献信息

中文摘要

背景与目的： 光子计数计算机断层扫描（PCCT）是一项新兴技术，与传统CT相比，可在更低辐射剂量下提供更高的空间分辨率和降噪效果；然而，剂量降低对具有临床意义的图像质量的影响尚未充分确立。遵循ALARA（合理可行尽量低）原则，本研究评估了不同递减辐射剂量下的颞骨图像质量，以确定维持诊断完整性所需的最低剂量。
材料与方法： 七具尸体头颅在四个管电流-时间乘积（290、75、25和11 mAs）下接受颞骨PCCT成像。所有扫描均在120 kV、0.55螺距和0.5秒旋转时间下采集，并以0.2 mm层厚在轴位和冠状面重建左右颞骨。三名委员会认证的放射科医师使用5点Likert量表独立评估预先设定、随机化的颞骨解剖标志，以确定临床实用性（1-无法诊断；5-极佳）。采用以患者、阅片者和解剖标志为随机截距的混合效应线性回归估计各剂量的平均评分。两两比较采用Tukey校正，单侧FDR校正t检验评估预测平均评分是否超过3（临床充分）。
结果： 在290和75 mAs下，预测平均评分分别为4.81（95% CI：4.42-5.21）和4.21（95% CI：3.82-4.61），显示所有评估解剖标志的图像质量为良好/极佳，并超过临床充分性阈值（FDR校正p<0.0001）。在25 mAs下，预测平均评分为2.80（95% CI：2.41-3.19），处于差/充分范围；在11 mAs下评分最低，为2.09（95% CI：1.70-2.48），低于临床充分性阈值（p=0.99）。总体而言，平均Likert图像质量评分随mAs递减而下降，在25 mAs时仍具技术可解释性但低于临床充分性阈值。所有两两比较均具有统计学显著性（Tukey校正p<0.0001）。阅片者间一致性（Krippendorff's α）在各解剖标志间范围为0.301至0.657。
结论： PCCT在管电流-时间乘积低至75 mAs时仍维持临床充分的颞骨图像质量，而25 mAs及以下剂量低于可靠临床使用的阈值。根据ALARA原则，该阈值通过显著降低剂量优化了安全性，同时维持复杂颞骨解剖所需的高图像质量。

英文摘要

BACKGROUND AND PURPOSE: Photon-counting computed tomography (PCCT) is an emerging technology that offers improved spatial resolution and noise reduction at lower radiation doses than conventional CT; however, the effect of dose reduction on clinically significant image quality has not been well established. Following the ALARA (As Low As Reasonably Achievable) principle, this study evaluated temporal bone image quality across decreasing radiation doses to identify the minimum dose required to maintain diagnostic integrity.
MATERIALS AND METHODS: Seven cadaveric heads underwent temporal bone PCCT imaging at four tube current-time products: 290, 75, 25, and 11 mAs. All scans were acquired at 120 kV, 0.55 pitch, and a 0.5 second rotation time and reconstructed with 0.2-mm slice thickness in axial and coronal planes for left and right temporal bones. Three board-certified radiologists independently assessed prespecified, randomized temporal bone landmarks using a 5-point Likert scale to determine clinical utility (1-nondiagnostic; 5-excellent). Mixed-effects linear regression with random intercepts for patient, reader, and landmark estimated mean scores by dose. Pairwise comparisons were Tukey-adjusted, and one-sided FDR-adjusted t-tests evaluated whether predicted mean scores exceeded 3 (clinically sufficient).
RESULTS: At 290 and 75 mAs, predicted mean scores were 4.81 (95% CI: 4.42-5.21) and 4.21 (95% CI: 3.82-4.61), respectively, demonstrating good/excellent image quality for all evaluated landmarks and exceeding threshold for clinical sufficiency (FDR-adjusted p<0.0001). At 25 mAs, predicted mean scores were 2.80 (95% CI: 2.41-3.19), falling in the poor/sufficient range, and at 11 mAs, were rated the lowest at 2.09 (95% CI: 1.70-2.48), scoring below the clinical sufficiency threshold (p=0.99). Overall, mean Likert image quality scores decreased with progressive mAs reduction, remaining technically interpretable but below the threshold for clinical sufficiency at 25 mAs. All pairwise comparisons were statistically significant (Tukey-adjusted p<0.0001). Interreader agreement (Krippendorff's α) ranged from 0.301 to 0.657 across landmarks.
CONCLUSION: PCCT maintains clinically sufficient temporal bone image quality at tube current-time products as low as 75 mAs, while doses of 25 mAs and below fall below the threshold for reliable clinical use. Per ALARA, this threshold optimizes safety via significant dose reduction while maintaining the high image quality necessary for complex temporal bone anatomy.