一体化PET/MR不同衰减校正方式定量准确性分析及图像质量评估
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摘要
目的:探究基于MR的衰减校正(AC)和基于CT的衰减校正对于美国国家电气制造商协会(NEMA)IQ标准体模在一体化正电子发射计算机断层显像与磁共振(PET/MR)定量评估中的准确性,以及两种衰减校正方法下PET/MR重建图像质量的差异。方法:利用SIGNAPET/MR系统分析MR-AC和CT-AC条件下NEMAIQ图像μ-map的衰减系数,评估两种衰减校正方式在NEMA IQ体模质量控制实验中定量的准确性;参照NEMA NU 2-2007标准,根据其推荐的图像质量参数计算公式,以图像信噪比(SNR)作为评估图像质量的指标,对两种衰减校正方式下PET/MR矩阵(192×192,256×256)、迭代(2,3,4次)以及使用飞行时间(TOF)技术与否不同重建条件的图像质量进行评估。结果:体模质量控制实验中,基于MR的AC存在衰减系数分配错误,将肺和脂肪的衰减系数错误的分配给了肺部插件以及体模背景;在不同重建条件下基于CT-AC的图像SNR均高于基于MR-AC图像的SNR。结论:以MR-AC作为衰减校正方式的质量控制实验不足以作为PET/MR的定量标准,以CT-AC作为衰减校正方式的图像有更高的SNR,更优的图像质量。
Objective: To investigate the accuracy of MR-based attenuation correction(AC) and CT-based AC for NEMA IQ standard phantom in quantitative assessment of integration positron emission tomography/magnetic resonance(PET/MR), and the differences of reconstructive PET/MR imaging quality under two AC methods. Methods:Using the SIGNA PET/MR system to analyze the attenuation coefficient of the NEMA IQ image μ-map under MR-AC and CT-AC conditions, and to assess the accuracy of quantification of two AC modes in quality control experiment of NEMA IQ phantom. Referring to the National Electrical Manufacturers Association(NEMA) NU 2-2007 standard,and according to the recommended calculation formula of image quality parameter, and using signal noise ratio(SNR) of imaging as indicator of assessing imaging quality to implement assessment for imaging quality with different reconstruction conditions included PET/MR matrix(192×192, 256×256), iteration(2, 3, 4 times) and whether used time of fly(TOF) under two AC modes. Results: In the quality control experiment of phantom, MR-based AC had an error that was the attenuation coefficients of lung and fat were incorrectly assigned to the lung insert and phantom background in the allocation of attenuation coefficients. The SNR of CT-AC based image was higher than that of MRAC based image under different reconstruction conditions. Conclusion: The quality control experiment that uses MRAC as the AC mode is not enough as the quantitative standard of PET/MR. And the image that uses CT-AC as the AC mode has higher SNR and better image quality.
Objective: To investigate the accuracy of MR-based attenuation correction(AC) and CT-based AC for NEMA IQ standard phantom in quantitative assessment of integration positron emission tomography/magnetic resonance(PET/MR), and the differences of reconstructive PET/MR imaging quality under two AC methods. Methods:Using the SIGNA PET/MR system to analyze the attenuation coefficient of the NEMA IQ image μ-map under MR-AC and CT-AC conditions, and to assess the accuracy of quantification of two AC modes in quality control experiment of NEMA IQ phantom. Referring to the National Electrical Manufacturers Association(NEMA) NU 2-2007 standard,and according to the recommended calculation formula of image quality parameter, and using signal noise ratio(SNR) of imaging as indicator of assessing imaging quality to implement assessment for imaging quality with different reconstruction conditions included PET/MR matrix(192×192, 256×256), iteration(2, 3, 4 times) and whether used time of fly(TOF) under two AC modes. Results: In the quality control experiment of phantom, MR-based AC had an error that was the attenuation coefficients of lung and fat were incorrectly assigned to the lung insert and phantom background in the allocation of attenuation coefficients. The SNR of CT-AC based image was higher than that of MRAC based image under different reconstruction conditions. Conclusion: The quality control experiment that uses MRAC as the AC mode is not enough as the quantitative standard of PET/MR. And the image that uses CT-AC as the AC mode has higher SNR and better image quality.
引文
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[11]National Electrical Manufactures Association.Performance measurements of positron emission tomographs[S].NEMA Standards Publication NU 2-2012;Rosslyn,USA:National Electrical Manufactures Association,2012:26-33.
[12]Demir M,Toklu T,Abuqbeitah M,et al.Evaluation of PET Scanner Performance in PET/MR and PET/CT Systems:NEMA Tests[J].Mol Imaging Radionucl Ther,2018,27(1):10-18.
[13]Mehranian A,Zaidi H.Impact of Time-of-Flight PET on Quantification Errors in MR Imaging-Based Attenuation Correction[J].J Nucl Med,2015,56(4):635-641.
[2]Delso G,Fürst S,Jakoby B,et al.Performance measurements of the Siemens mMR integrated whole-body PET/MR scanner[J].J Nucl Med,2011,52(12):1914-22.
[3]Oehmigen M,Ziegler S,Jakoby BW,et al.Radiotracer Dose Reduction in Integrated PET/MR: Implications from National Electrical Manufacturers Association Phantom Studies[J].J Nucl Med,2014,55(8):1361-1367.
[4]Delso G,Martinez-M?ller A,Bundschuh RA,et al.Evaluation of the attenuation properties of MR equipment for its use in a whole-body PET/MR scanner[J].Phys Med Biol,2010,55(15):4361-4374.
[5]Drzezga A,Souvatzoglou M,Eiber M,et al.First clinical experience with integrated whole-body PET/MR:comparison to PET/CT in patients with oncologic diagnoses[J].J Nucl Med,2012,53(6):845-855.
[6]Wiesmüller M,Quick HH,Navalpakkam B,et al.Comparison of lesion detection and quantitation of tracer uptake between PET from a simultaneously acquiring whole-body PET/MR hybrid scanner and PET from PET/CT[J].Eur J Nucl Med Mol Imaging,2013,40(1):12-21.
[7]Wollenweber SD,Ambwani S,Lonn AHR,et al.Comparison of 4-Class and Continuous Fat/Water Methods for Whole-Body,MR-Based PET Attenuation Correction[J].IEEE Transactions on Nuclear Science,2013,60(5):3391-3398.
[8]Grant AM,Deller TW,Khalighi MM,et al.NEMA NU 2-2012 performance studies for the SiPM-based ToF -PET component of the GE SIGNA PET/MR system[J].Med Phys,2016,43(5):2334.
[9]Boellaard R,Rausch I,Beyer T,et al.Quality control for quantitative multicenter whole-body PET/MR studies:A NEMA image quality phantom study with three current PET/MR systems[J].Medical Physics,2015,42(10):5961-5969.
[10]Olin A,Ladefoged CN,Langer NH,et al.Reproducibility of MR-based Attenuation Maps in PET/MRI and the Impact on PET Quantification in Lung Cancer[J].J Nucl Med,2018,59(6):999-1004.
[11]National Electrical Manufactures Association.Performance measurements of positron emission tomographs[S].NEMA Standards Publication NU 2-2012;Rosslyn,USA:National Electrical Manufactures Association,2012:26-33.
[12]Demir M,Toklu T,Abuqbeitah M,et al.Evaluation of PET Scanner Performance in PET/MR and PET/CT Systems:NEMA Tests[J].Mol Imaging Radionucl Ther,2018,27(1):10-18.
[13]Mehranian A,Zaidi H.Impact of Time-of-Flight PET on Quantification Errors in MR Imaging-Based Attenuation Correction[J].J Nucl Med,2015,56(4):635-641.