Radiotherapy Department, IRCCS Istituto Clinico Humanitas, Rozzano (Mi), Italy.
Medical Physics Department, Arcispedale S. Maria Nuova, Reggio, Emilia, Italy.
J Appl Clin Med Phys. 2009 Oct 28;10(4):220-231. doi: 10.1120/jacmp.v10i4.2917.
This study aims at evaluating the dependence of 4D-PET data sorting on the number of phases in which the respiratory cycle can be divided. The issue is to find the best compromise to reduce the conflicting effects induced by increasing the number of phases: lesion motion on each set of images decreases, but on the other hand image noise increases. The IQ NEMA 2001 IEC body phantom was used to simulate the movement of neoplastic lesions in the thorax and abdomen, investigating the effect of target size (10-37 mm), lesion to background activity concentrations ratio (4-to-1 and 8-to-1), total acquisition time (3, 6, 12, 20 min) and number of phase partition (1, 2, 4, 6, 8, 10, 13). The phantom was moved in a cranial-caudal direction with an excursion of 25 mm and with a period of 4.0 s. Five parameters associated to lesion volume and activity concentration were considered to assess the capability of the 4D-PET technique to "freeze" the phantom motion. The results for all the parameters showed the capability of the 4D-PET acquisition technique to "freeze" the lesion motion. The division into 6 phases was found to be the best compromise between temporal resolution and image noise for the phase where the "lesions" move faster, whereas the partition into 4 phases could be used if a stable breathing phase is considered.
本研究旨在评估 4D-PET 数据分类对呼吸周期可分为的相位数量的依赖性。问题是要找到最佳折衷方案，以减少增加相位数量引起的冲突效应：病变在每一组图像上的运动减少，但另一方面，图像噪声增加。使用 IQ NEMA 2001 IEC 体模模拟胸部和腹部肿瘤病变的运动，研究了目标大小（10-37mm）、病变与背景活性浓度比（4 比 1 和 8 比 1）、总采集时间（3、6、12、20min）和相位分区数量（1、2、4、6、8、10、13）的影响。体模以 4.0s 的周期和 25mm 的偏移量在头足方向移动。考虑了与病变体积和活性浓度相关的五个参数，以评估 4D-PET 技术“冻结”体模运动的能力。所有参数的结果均表明 4D-PET 采集技术有能力“冻结”病变运动。对于“病变”移动较快的相位，发现将其分为 6 个相位是时间分辨率和图像噪声之间的最佳折衷方案，而如果考虑稳定的呼吸相位，则可以使用 4 个相位分区。
