Impact of noise index combined with deep learning image reconstruction on image quality and radiation dose
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摘要:
目的 探讨深度学习图像重建(DLIR)在超低剂量肺部CT成像中的应用价值。 方法 选取2024年3~4月在陕西中医药大学附属医院行肺部CT平扫患者66例。所有患者均采用GE Revolution CT扫描,固定管电压100 kVp,第1次采用噪声指数(NI)=15的常规辐射剂量扫描,滤波反投影算法重建图像;第2次采用NI=45的超低辐射剂量扫描,中、高等强度深度学习图像重建(DLIR-M、DLIR-H)进行对比。在3组重建图像上测量左上肺乏血供区域CT值与标准差值(SD),SD代表噪声,计算信噪比(SNR)。由2位放射科诊断医师采用5分法进行主观评价,比较3组客观数值和主观评分。 结果 NI=45组约减少93.7%辐射剂量;DLIR强度影响超低剂量条件下客观指标,DLIR-H较DLIR-M有更低的噪声,更高的SNR(P < 0.05);2位医师对3组图像质量一致性评价好(Kappa值为0.952、0.846、0.903);对比3组图像质量评分、图像合格率及满意率,差异无统计学意义(P > 0.05)。 结论 在减少93.7%辐射剂量条件下,DLIR能够获得与常规剂量接近的肺部图像,进一步减低了肺部疾病筛查的辐射剂量。 Abstract:Objective To explore the application value of Deep learning image reconstruction (DLIR) in ultra-low-dose chest CT imaging. Methods A total of 66 patients with chest CT scans in the Affiliated Hospital of Shaanxi University of Traditional Chinese Medicine from March to April 2024 were collected.All patients were used GE Revolution CT scans, the fixed tube voltage was 100 kVp, and the first with conventional radiation dose with noise index (NI) =15, and filtered back projection reconstructed images; the second was scanned with ultra-low-dose with NI= 45, and medium and high intensity deep learning image reconstruction (DLIR- M、DLIR- H) were compared. The CT value and standard deviation (SD) of the left upper pulmonary hypovascular region were measured on three reconstructed images, SD represented noise, and the signal-to-noise ratio (SNR) was calculated. Subjective evaluation of 5-point method was used by two radiologists. The objective value and subjective score of three reconstructed images were compared. Results The NI=45 group reducted the radiation dose by 93.7%. The intensity of DLIR affected the objective value under ultra-low-dose condition, DLIR-H resulted in ower noise and higher SNR than DLIR-M (P < 0.05). Two physicians evaluated the image quality consistency of the three reconstructed images (Kappa= 0.952, 0.846, 0.903). The image quality scores, pass rates and satisfaction rates had no significant differences between three groups (P > 0.05). Conclusion Under the condition of reducing the radiation dose by 93.7%, DLIR can obtain images of the lung that are close to the conventional radiation dose, and the radiation dose for lung disease screening has been further reduced. -
Key words:
- ultra-low dose /
- lung CT /
- deep learning /
- image quality /
- radiation dose
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表 1 3组图像CT值、SD值及SNR值比较
Table 1. Comparison of CT, SD and SNR values of three groups of images
Item FBP DLIR-M+E3 DLIR-H+E3 F/H P CT -895.98±17.41 -892.83±18.36 -892.47±18.20 0.761 0.469 SD 67.80±5.62 73.12±6.18 63.89±5.17 44.005 < 0.001 SNR 13.43(1.67) 12.12(1.53) 14.06(1.87) 55.084 < 0.001 FBP: Filtered back projection; DLIR-M + E3/DLIR-H + E3: Deep learning image reconstruction at medium/high strength with additional post-processing using an edge-enhancement filter E3; SD: Standard deviation; SNR: Signal to noise ratio. 表 2 3组图像质量主观评分一致性分析
Table 2. Consistency analysis of subjective scores of image quality in three groups (n)
Image groups Evaluator Image quality score 1 2 3 4 5 FBP A 0 4 34 20 8 B 0 5 34 19 8 DLIR-M+E3 A 0 7 38 17 4 B 0 8 38 16 4 DLIR-H+E3 A 0 7 34 19 6 B 0 6 36 18 6 表 3 3组图像质量主观评分比较
Table 3. Comparison of subjective image quality scores among the three groups (n)
Image groups Image quality score < 3 3-4 ≥4 FBP 5 34 27 DLIR-M+E3 8 38 20 DLIR-H+E3 5 37 24 H 1.97 P 0.373 表 4 3组图像合格率、满意率比较
Table 4. Comparison of image pass rate and satisfaction rate among the three groups (%)
Image groups Passing rate Satisfaction rate FBP 92.4(61/66) 40.9(27/66) DLIR-M+E3 87.9(58/66) 30.3(20/66) DLIR-H+E3 90.9(60/66) 36.4(24/66) χ2 0.815 1.625 P 0.665 0.444 -
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