Ramsdell John C, Beynnon Bruce D, Borah Andrew S, Gardner-Morse Mack G, Zhang Jiming, Krug Mickey I, Tourville Timothy W, Geeslin Matthew, Failla Mathew J, Vacek Pamela M, Fiorentino Niccolo M
Department of Electrical and Biomedical Engineering, University of Vermont.
Department of Orthopaedics and Rehabilitation, University of Vermont.
Osteoarthr Imaging. 2023 Sep;3(3). doi: 10.1016/j.ostima.2023.100162. Epub 2023 Jul 11.
Quantitative magnetic resonance imaging (qMRI) parameters such as T1ρ and T2* characterize changes in cartilage matrix composition prior to cartilage loss. However, T1ρ and T2* measurement reliability in phantoms that mimic knee size and position within the scanner bore (left or right side of isocenter) is unknown. This study aimed to quantify sources of variance, and the systematic differences between left and right positions in T1ρ and T2* in small vials of a commercially available phantom and a knee-sized phantom.
Phantoms were imaged 100 mm to the left and right of isocenter on five days using 3D MAPSS (T1ρ) and 3D gradient echo (T2*) sequences at 3T. Variance component analysis estimated the variability attributable to slice, side, vial, and day. Measurement error was quantified with 95% confidence intervals (CI). Paired t-tests evaluated systematic differences between the left and right imaging locations (p<.05).
Averaged across days the left-to-right phantom positions produced differences of 0.1ms (p<.0001) for T1ρ and -0.8ms (p<.0001) for T2* in the knee-sized phantoms, and differences ranged from -1.5±0.3ms (p=0.0004) to -0.4±0.4ms (p=0.045) for T1ρ and -3.3±2.5ms (p<.0001) to 2.3±1.5ms (p<.0001) for T2* in the small vial phantoms. The total variance for T2* was much less for the knee-sized phantom (0.9) than the small-vial pairs with the same concentration (7.0).
This study revealed a position and phantom size dependence on qMRI parameters not reported previously. Future studies and quality control acquisitions should consider position within the MR scanner and phantom size in their design.
定量磁共振成像（qMRI）参数，如T1ρ和T2*，可在软骨丢失之前表征软骨基质成分的变化。然而，在模拟膝关节大小及在扫描孔内位置（等中心左侧或右侧）的模型中，T1ρ和T2测量的可靠性尚不清楚。本研究旨在量化方差来源，以及在市售模型的小瓶和膝关节大小模型中，T1ρ和T2在左侧和右侧位置之间的系统差异。
使用3D MAPSS（T1ρ）和3D梯度回波（T2*）序列在3T条件下，于等中心左侧和右侧100 mm处对模型进行为期五天的成像。方差成分分析估计了切片、侧面、小瓶和日期所导致的变异性。测量误差用95%置信区间（CI）进行量化。配对t检验评估左右成像位置之间的系统差异（p<0.05）。
在膝关节大小的模型中，T1ρ的左右模型位置平均每天产生0.1毫秒的差异（p<0.0001），T2为-0.8毫秒（p<0.0001）；在小瓶模型中，T1ρ的差异范围为-1.5±0.3毫秒（p=0.0004）至-0.4±0.4毫秒（p=0.045），T2为-3.3±2.5毫秒（p<0.0001）至2.3±1.5毫秒（p<0.0001）。膝关节大小模型的T2*总方差（0.9）远小于相同浓度小瓶模型对的总方差（7.0）。
本研究揭示了qMRI参数对位置和模型大小的依赖性，这是之前未报道过的。未来的研究和质量控制采集在设计中应考虑磁共振扫描仪内的位置和模型大小。
