Siman W, Mawlawi O R, Mikell J K, Mourtada F, Kappadath S C
Department of Imaging Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA. The University of Texas Graduate School of Biomedical Sciences at Houston, Houston, TX, USA.
Phys Med Biol. 2017 Jan 21;62(2):448-464. doi: 10.1088/1361-6560/aa5088. Epub 2016 Dec 21.
The aims of this study were to evaluate the effects of noise, motion blur, and motion compensation using quiescent-period gating (QPG) on the activity concentration (AC) distribution-quantified using the cumulative AC volume histogram (ACVH)-in count-limited studies such as Y-PET/CT. An International Electrotechnical Commission phantom filled with low F activity was used to simulate clinical Y-PET images. PET data were acquired using a GE-D690 when the phantom was static and subject to 1-4 cm periodic 1D motion. The static data were down-sampled into shorter durations to determine the effect of noise on ACVH. Motion-degraded PET data were sorted into multiple gates to assess the effect of motion and QPG on ACVH. Errors in ACVH at AC (minimum AC that covers 90% of the volume of interest (VOI)), AC, and AC (average AC in the VOI) were characterized as a function of noise and amplitude before and after QPG. Scan-time reduction increased the apparent non-uniformity of sphere doses and the dispersion of ACVH. These effects were more pronounced in smaller spheres. Noise-related errors in ACVH at AC to AC were smaller (<15%) compared to the errors between AC to AC (>15%). The accuracy of AC was largely independent of the total count. Motion decreased the observed AC and skewed the ACVH toward lower values; the severity of this effect depended on motion amplitude and tumor diameter. The errors in AC to AC for the 17 mm sphere were -25% and -55% for motion amplitudes of 2 cm and 4 cm, respectively. With QPG, the errors in AC to AC of the 17 mm sphere were reduced to -15% for motion amplitudes <4 cm. For spheres with motion amplitude to diameter ratio >0.5, QPG was effective at reducing errors in ACVH despite increases in image non-uniformity due to increased noise. ACVH is believed to be more relevant than mean or maximum AC to calculate tumor control and normal tissue complication probability. However, caution needs to be exercised when using ACVH in post-therapy Y imaging because of its susceptibility to image degradation from both image noise and respiratory motion.
本研究的目的是在诸如Y-PET/CT等计数受限研究中，评估噪声、运动模糊以及使用静止期门控（QPG）进行运动补偿对通过累积活度浓度（AC）体积直方图（ACVH）量化的活度浓度（AC）分布的影响。使用填充低氟活度的国际电工委员会体模来模拟临床Y-PET图像。当体模静止且进行1-4厘米周期性一维运动时，使用GE-D690采集PET数据。将静态数据下采样为更短的时长，以确定噪声对ACVH的影响。将运动退化的PET数据分类到多个门控中，以评估运动和QPG对ACVH的影响。在QPG前后，将AC（覆盖90%感兴趣体积（VOI）的最小AC）、AC和AC（VOI中的平均AC）处ACVH的误差表征为噪声和幅度的函数。扫描时间的减少增加了球体剂量的表观不均匀性以及ACVH的离散度。这些影响在较小的球体中更为明显。与AC至AC之间的误差（>15%）相比，AC至AC处ACVH中与噪声相关的误差较小（<15%）。AC的准确性在很大程度上与总计数无关。运动降低了观察到的AC，并使ACVH向较低值倾斜；这种影响的严重程度取决于运动幅度和肿瘤直径。对于17毫米球体，运动幅度为2厘米和4厘米时，AC至AC的误差分别为-25%和-55%。使用QPG时，对于运动幅度<4厘米的情况，17毫米球体AC至AC的误差降至-15%。对于运动幅度与直径比>0.5的球体，尽管由于噪声增加导致图像不均匀性增加，但QPG在减少ACVH误差方面仍然有效。人们认为，在计算肿瘤控制和正常组织并发症概率时，ACVH比平均或最大AC更具相关性。然而，由于其易受图像噪声和呼吸运动导致的图像退化影响，在治疗后Y成像中使用ACVH时需要谨慎。
