Ng Chaan S, Chandler Adam G, Chen Yanwen, Wei Wei, Tannir Nizar M, Hobbs Brian P
Department of Radiology, Unit 1473, University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA.
Imaging Physics, University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA.
Res Diagn Interv Imaging. 2023 Apr 10;6:100028. doi: 10.1016/j.redii.2023.100028. eCollection 2023 Jun.
CT perfusion (CTp) values are affected by CT scan acquisition duration (t); their reproducibility is adversely affected by uncertainty in their measurement. The objectives were to assess the effects of t on CTp parameter values in metastases from renal cell carcinoma (mRCC) in thoracic and abdominal locations.
131 CTp evaluations in 53 patients with mRCC were retrospectively analyzed by distributed parameter modeling to yield tissue blood flow (BF), blood volume (BV), mean transit time (MTT), permeability (PS), and also hepatic arterial perfusion (HAP) and hepatic arterial fraction (HAF) for liver metastases and normal liver, with t from 25 to 590 s. Penalized piecewise polynomial regression (SPLINE) characterized functional relationships between CTp parameters and acquisition duration, t. Evidence for time-invariance was evaluated for each parameter at multiple time points by conducting inference on the fitted derivative to assess its proximity to zero as a function of acquisition time. Equivalence testing was implemented with three levels of confidence (low (20%), moderate (70%), high (95%)).
Systematic and non-systematic variability was observed for CTp parameter values with limited t. All parameters in all locations approached increasing stability with increasing t. PS, HAP and HAF required longer acquisition times than BF, BV and MTT to attain comparable levels of stability. Stabilization tended to require longer acquisition in liver than other tissues. t=380 s was required to obtain at least moderate level of confidence for all parameters and organs.
Increasing t yields increasingly more stable CT perfusion parameters, and thereby better reproducibility.
CT灌注（CTp）值受CT扫描采集时长（t）影响；其测量的不确定性会对其可重复性产生不利影响。目的是评估t对胸腹部肾细胞癌转移灶（mRCC）中CTp参数值的影响。
对53例mRCC患者的131次CTp评估进行回顾性分析，采用分布参数模型得出组织血流量（BF）、血容量（BV）、平均通过时间（MTT）、通透性（PS），以及肝转移灶和正常肝脏的肝动脉灌注（HAP）和肝动脉分数（HAF），t范围为25至590秒。惩罚分段多项式回归（样条法）表征了CTp参数与采集时长t之间的函数关系。通过对拟合导数进行推断，评估每个参数在多个时间点的时间不变性证据，以评估其作为采集时间函数与零的接近程度。采用三种置信水平（低（20%）、中（70%）、高（95%））进行等效性检验。
在有限的t条件下，观察到CTp参数值存在系统和非系统变异性。所有部位的所有参数随着t增加趋于更高的稳定性。与BF、BV和MTT相比，PS、HAP和HAF需要更长的采集时间才能达到相当的稳定性水平。肝脏比其他组织往往需要更长的采集时间来实现稳定。所有参数和器官至少需要t = 380秒才能获得中等置信水平。
增加t可使CT灌注参数越来越稳定，从而具有更好的可重复性。
