Bourdon Caleigh E, Koudys Zachary J, Lanting Brent A, Appleton C Thomas, Thiessen Jonathan D, Teeter Matthew G
Department of Medical Biophysics, Schulich School of Medicine & Dentistry, Western University, London, Canada.
Robarts Research Institute, London, Canada.
Eur J Hybrid Imaging. 2022 Nov 7;6(1):31. doi: 10.1186/s41824-022-00152-3.
Positron emission tomography (PET) in combination with magnetic resonance imaging (MRI) could allow inflammatory complications near total knee arthroplasty (TKA) to be studied early in their development. However, attenuation of the PET signal by the metal TKA implants imparts substantial error into measurements of tracer activity, and conventional MR-based attenuation correction (AC) methods have large signal voids in the vicinity of metal implants.
To evaluate a segmentation-based AC approach to measure tracer uptake from PET/MRI scans near TKA implants.
A TKA implant (Triathlon, Stryker, Mahwah, USA) was implanted into a cadaver. Four vials were filled with [F]fluorodeoxyglucose with known activity concentration (4.68 MBq total, 0.76 MBq/mL) and inserted into the knee. Images of the knee were acquired using a 3T PET/MRI system (Biograph mMR, Siemens Healthcare, Erlangen, Germany). Models of the implant components were registered to the MR data using rigid-body transformations and the other tissue classes were manually segmented. These segments were used to create the segmentation-based map and complete the AC. Percentage error of the resulting measured activities was calculated by comparing the measured and known amounts of activity in each vial.
The original AC resulted in a percentage error of 64.1% from the known total activity. Errors in the individual vial activities ranged from 40.2 to 82.7%. Using the new segmentation-based AC, the percentage error of the total activity decreased to 3.55%. Errors in the individual vials were less than 15%.
The segmentation-based AC technique dramatically reduced the error in activity measurements that result from PET signal attenuation by the metal TKA implant. This approach may be useful to enhance the reliability of PET/MRI measurements for numerous applications.
正电子发射断层扫描（PET）与磁共振成像（MRI）相结合能够在全膝关节置换术（TKA）附近的炎症并发症发展早期进行研究。然而，金属TKA植入物对PET信号的衰减会给示踪剂活性测量带来大量误差，并且传统的基于磁共振的衰减校正（AC）方法在金属植入物附近存在较大的信号空白区。
评估一种基于分割的AC方法，用于测量TKA植入物附近PET/MRI扫描的示踪剂摄取情况。
将一个TKA植入物（Triathlon，史赛克公司，美国新泽西州马霍瓦）植入一具尸体。四个小瓶中装入已知活性浓度（总量4.68MBq，0.76MBq/mL）的[F]氟脱氧葡萄糖，并插入膝关节。使用3T PET/MRI系统（Biograph mMR，西门子医疗公司，德国埃尔朗根）采集膝关节图像。利用刚体变换将植入物部件模型配准到磁共振数据上，其他组织类别则手动分割。这些分割区域用于创建基于分割的图谱并完成AC。通过比较每个小瓶中测量的和已知的活性量，计算出所得测量活性的百分比误差。
原始AC导致与已知总活性相比的百分比误差为64.1%。各个小瓶活性的误差范围为40.2%至82.7%。使用新的基于分割的AC，总活性的百分比误差降至3.55%。各个小瓶中的误差小于15%。
基于分割的AC技术显著降低了因金属TKA植入物导致的PET信号衰减所引起的活性测量误差。这种方法对于提高PET/MRI在众多应用中的测量可靠性可能是有用的。
