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PET/CT是将PET和CT两种先进的影像学技术有机地集合在一起的分子影像学设备。PET是采用正电子核素标记显像剂参与活体代谢,提供分子水平上反映体内代谢的影像,但对图像解剖结构显示不清楚;CT的分辨率高,图像具有精细的解剖结构信息,但缺乏功能信息。把两者有机地结合起来,实现了功能图像与解剖图像信息的互补,并且提高了诊断的灵敏度、特异度和准确率。但随着CT设备的广泛应用,潜在的辐射危害也引起了人们的关注[1]。PET/CT是肿瘤诊断和分期的最佳方法之一,但受检者所受辐射剂量必须充分考虑,以平衡检查的益处和辐射暴露的风险[2]。自动管电流调制(automatic tube current modulation,ATCM)技术能有效降低辐射剂量,近些年来得到了广泛应用[3-4]。笔者通过调节管电流区间和噪声指数(noise index,NI),评价ATCM技术对PET/CT中CT图像质量及受检者有效剂量(effective dose,ED)的影响。
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A、B、C 3组患者的身高、体重、BMI的差异均无统计学意义(F=0.73、0.40、0.95,均P>0.05)(表1),具有可比性。2名医师对CT图像质量评分的一致性较好,Kappa值为0.69~0.83。3组患者所有图像质量评分均不低于3分,且差异均有统计学意义(F=3.77~14.42,均P<0.05)(表2)。A、B、C 3组患者的SD值和SNR差异均有统计学意义(F=38.01~64.20和F=32.09~81.62,均P<0.05)(表3)。A、B、C 3组患者的CTDIvol、DLP、ED的差异均有统计学意义(χ2=62.18、57.19和57.16,均P<0.05)(表4)。ED的两两比较,B组比A组低,差异有统计学意义(χ2=19.70,P<0.05);C组比B组低,差异有统计学意义(χ2=9.50,P<0.05);C组比A组低,差异有统计学意义(χ2=56.55,P<0.05)。
组别 例数 身高(m) 体重(kg) MBI(kg/m2) A组 30 1.62±0.09 56.53±9.88 21.63±3.01 B组 30 1.64±0.07 57.97±9.05 21.65±2.93 C组 30 1.61±0.09 58.63±8.94 22.59±3.24 F值 0.73 0.40 0.95 P值 0.487 0.672 0.389 注:表中,A、B、C 3组为采用系统抽样方法进行的分组。PET:正电子发射断层显像术;CT:计算机体层摄影术;MBI:体质量指数。 表 1 90例行PET/CT检查的成年受检者的基本信息(
$\bar x $ Table 1. Basic information of PET/CT of 90 patients(
$\bar x $ 组别 例数 颈部CT(分) 胸部CT(分) 腹部CT(分) 盆腔CT(分) A组 30 4.37±0.49 4.43±0.50 4.30±0.53 4.30±0.47 B组 30 4.06±0.45 4.16±0.46 4.00±0.45 3.97±0.49 C组 30 4.00±0.49 4.10±0.48 3.67±0.55 3.63±0.49 F值 4.96 3.77 11.58 14.42 P值 0.010 0.029 0.000 0.000 注:表中,A、B、C 3组为采用系统抽样方法进行的分组。PET:正电子发射断层显像术;CT:计算机体层摄影术。 表 2 90例行PET/CT检查的成年受检者的CT图像质量主观评分(
$\bar x $ Table 2. Subjective evaluation of CT image quality of PET/CT of 90 patients (
$\bar x $ 组别 例数 SD SNR 颈部 胸部 腹部 盆腔 颈部 胸部 腹部 盆腔 A组 30 11.90±2.83 12.07±1.55 18.17±2.99 17.96±3.06 4.35±0.71 3.20±0.52 2.96±0.49 3.07±0.61 B组 30 19.89±3.44 15.42±1.93 21.61±3.71 22.82±2.82 2.71±0.48 2.51±0.32 2.46±0.41 2.33±0.33 C组 30 20.67±3.63 16.22±2.15 26.03±3.74 25.65±2.54 2.61±0.56 2.39±0.41 2.03±0.34 2.07±0.26 F值 64.20 40.39 38.01 57.21 81.62 32.09 37.61 53.67 P值 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 注:表中,A、B、C 3组为采用系统抽样方法进行的分组。PET:正电子发射断层显像术;CT:计算机体层摄影术;SD:标准差(即:噪声值);SNR:信噪比。 表 3 90例行PET/CT检查的成年受检者的CT图像质量客观评价结果(
$\bar x $ Table 3. Objective evaluation of CT image quality of PET/CT of 90 patients (
$\bar x $ 组别 例数 CTDIvol(mGy) DLP(mGy·cm) ED(mSv) A组 30 12.44±0.53 998.45±96.04 14.98±1.44 B组 30 9.39±2.01 741.60±168.87 11.12±2.53 C组 30 7.05±1.03 571.29±97.41 8.57±1.46 χ2值 62.18 57.19 57.16 P值 0.000 0.000 0.000 注:表中,A、B、C 3组为采用系统抽样方法进行的分组。PET:正电子发射断层显像术;CT:计算机体层摄影术;CTDIvol:容积CT剂量指数;DLP:剂量长度乘积;ED:有效剂量。 表 4 90例行PET/CT检查的成年受检者的辐射剂量(
$\bar x $ Table 4. Radiation dose of PET/CT of 90 patients (
$\bar x $
自动管电流调制技术在PET/CT中的实际应用
Application of automatic tube current modulation technology in PET/CT
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摘要:
目的 探讨自动管电流调制(ATCM)技术对PET/CT受检者CT图像质量及有效剂量的影响。 方法 将2017年10月至2018年7月接受PET/CT检查的90例受检者按系统抽样方法分为A、B、C 3组,每组各30例。CT采用ATCM扫描。A、B两组采用的管电流区间为60~240 mA,噪声指数分别为10、15;C组管电流区间为60~180 mA,噪声指数为15。记录容积CT剂量指数(CTDIvol)和剂量长度乘积(DLP),根据公式估算有效剂量。由两位核医学科主治及以上医师采用双盲法对受检者颈部、胸部、腹部、盆腔CT图像质量进行评分,测定图像CT值、噪声值并计算信噪比。采用方差分析比较3组的噪声值、信噪比差异,采用非参数检验中的Kruskal-Wallis检验比较3组的CTDIvol、DLP、有效剂量差异,组内两两比较采用Nemenyi检验。 结果 A、B、C 3组受检者所有图像质量评分均不低于3分,且差异均有统计学意义(F=3.77~14.42,均P<0.05)。A、B、C 3组受检者的噪声值[(11.90±2.83)~(26.03±3.74)]、信噪比[(2.03±0.34)~(4.35±0.71)]差异均有统计学意义(F=38.01~64.20和F=32.09~81.62,均P<0.05),CT图像质量均能满足临床诊断要求。A、B、C 3组受检者的CTDIvol[(12.44±0.53)、(9.39±2.01)和(7.05±1.03)mGy]、DLP[(998.45±96.04)、(741.60±168.87)和(571.29±97.41) mGy·cm]、有效剂量[(14.98±1.44)、(11.12±2.53)和(8.57±1.46) mSv]的差异均有统计学意义(χ2=62.18、57.19和57.16,均P<0.05)。其中,C组比A组的有效剂量低,差异有统计学意义(χ2=56.55,P<0.05)。 结论 应用PET/CT ATCM技术,合理调节管电流区间及噪声指数,保证图像质量的同时可有效降低受检者的有效剂量。 -
关键词:
- 正电子发射断层显像计算机体层摄影术 /
- 辐射剂量 /
- 自动管电流调制技术 /
- 图像质量
Abstract:Objective To investigate the effects of automatic tube current modulation (ATCM) on CT image quality and effective dose(ED) of PET/CT of 90 patients. Methods PET/CT of 90 patients from October 2017 to July 2018 were randomly divided into three groups, A, B, and C by systematic sampling(30 cases in each group), and CT was scanned by ATCM. The tube current interval of group A and B was 60–240 mA, and the noise index(NI) was 10 and 15; the tube current interval of group C was 60–180 mA, and the NI was 15. The CT volume dose index(CTDIvol) and dose length product(DLP) were recorded, and the ED was estimated according to the formula. The CT image quality of neck, chest, abdomen, and pelvis were evaluated blindly by two and above attending physicians in nuclear medicine to calculate signal-to-noise ratio(SNR) by measuring CT value and noise value of the CT image. Noise value and SNR were compared with variance analysis. CTDIvol, DLP, and ED were compared with Kruskal-Wallis and with Nemenyi in pairs. Results Differences in noise value[(11.90±2.83)–(26.03±3.74)] and SNR [(2.03±0.34)–(4.35±0.71)] among three groups were statistically significant (F=38.01–64.20, F=32.09–81.62, and all P<0.05), and the CT image quality met the clinical diagnostic requirements. CTDIvol were (12.44±0.53), (9.39±2.01), and (7.05±1.03) mGy, DLP were (998.45±96.04), (741.60±168.87), and (571.29±97.41) mGy·cm, and ED were (14.98±1.44), (11.12±2.53), and (8.57±1.46) mSv among three groups, with statistically significant differences(χ2=62.18, 57.19, 57.16, and all P<0.05). Group C was lower than group A(χ2=56.55, P<0.05) with statistically significant differences. Conclusion ATCM technology can ensure the image quality while reducing the ED effectively by modulating the current interval and NI reasonably. -
表 1 90例行PET/CT检查的成年受检者的基本信息(
$\bar x $ Table 1. Basic information of PET/CT of 90 patients(
$\bar x $ 组别 例数 身高(m) 体重(kg) MBI(kg/m2) A组 30 1.62±0.09 56.53±9.88 21.63±3.01 B组 30 1.64±0.07 57.97±9.05 21.65±2.93 C组 30 1.61±0.09 58.63±8.94 22.59±3.24 F值 0.73 0.40 0.95 P值 0.487 0.672 0.389 注:表中,A、B、C 3组为采用系统抽样方法进行的分组。PET:正电子发射断层显像术;CT:计算机体层摄影术;MBI:体质量指数。 表 2 90例行PET/CT检查的成年受检者的CT图像质量主观评分(
$\bar x $ Table 2. Subjective evaluation of CT image quality of PET/CT of 90 patients (
$\bar x $ 组别 例数 颈部CT(分) 胸部CT(分) 腹部CT(分) 盆腔CT(分) A组 30 4.37±0.49 4.43±0.50 4.30±0.53 4.30±0.47 B组 30 4.06±0.45 4.16±0.46 4.00±0.45 3.97±0.49 C组 30 4.00±0.49 4.10±0.48 3.67±0.55 3.63±0.49 F值 4.96 3.77 11.58 14.42 P值 0.010 0.029 0.000 0.000 注:表中,A、B、C 3组为采用系统抽样方法进行的分组。PET:正电子发射断层显像术;CT:计算机体层摄影术。 表 3 90例行PET/CT检查的成年受检者的CT图像质量客观评价结果(
$\bar x $ Table 3. Objective evaluation of CT image quality of PET/CT of 90 patients (
$\bar x $ 组别 例数 SD SNR 颈部 胸部 腹部 盆腔 颈部 胸部 腹部 盆腔 A组 30 11.90±2.83 12.07±1.55 18.17±2.99 17.96±3.06 4.35±0.71 3.20±0.52 2.96±0.49 3.07±0.61 B组 30 19.89±3.44 15.42±1.93 21.61±3.71 22.82±2.82 2.71±0.48 2.51±0.32 2.46±0.41 2.33±0.33 C组 30 20.67±3.63 16.22±2.15 26.03±3.74 25.65±2.54 2.61±0.56 2.39±0.41 2.03±0.34 2.07±0.26 F值 64.20 40.39 38.01 57.21 81.62 32.09 37.61 53.67 P值 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 注:表中,A、B、C 3组为采用系统抽样方法进行的分组。PET:正电子发射断层显像术;CT:计算机体层摄影术;SD:标准差(即:噪声值);SNR:信噪比。 表 4 90例行PET/CT检查的成年受检者的辐射剂量(
$\bar x $ Table 4. Radiation dose of PET/CT of 90 patients (
$\bar x $ 组别 例数 CTDIvol(mGy) DLP(mGy·cm) ED(mSv) A组 30 12.44±0.53 998.45±96.04 14.98±1.44 B组 30 9.39±2.01 741.60±168.87 11.12±2.53 C组 30 7.05±1.03 571.29±97.41 8.57±1.46 χ2值 62.18 57.19 57.16 P值 0.000 0.000 0.000 注:表中,A、B、C 3组为采用系统抽样方法进行的分组。PET:正电子发射断层显像术;CT:计算机体层摄影术;CTDIvol:容积CT剂量指数;DLP:剂量长度乘积;ED:有效剂量。 -
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