Samuel Stanley, Miller Douglas L, Fowlkes J Brian
Department of Radiology, University of Michigan Medical Center, Ann Arbor, MI 48109-0553, USA.
Ultrasound Med Biol. 2006 Mar;32(3):439-47. doi: 10.1016/j.ultrasmedbio.2005.11.007.
The effect of pulse-repetition frequency (PRF) and number of exposures on membrane damage and subsequent death of contrast agent-attached phagocytic cells was examined. Phagocytic cells of a mouse macrophage cell line were grown as monolayers on thin Mylar sheets. Optison microbubbles were attached to these cells by incubation. Focused ultrasound exposures (Pr = 2 MPa) were implemented at a frequency of 2.25 MHz with 46 cycle pulses and clinically relevant PRFs of 1 kHz, 100 Hz, 10 Hz, 1 Hz and 0.1 Hz in a degassed water bath. A 1-MHz receive transducer measured the scattered signal. The frequency spectrum was normalized to a control spectrum from linear scatterers. Photomicrographs of the cell monolayer were made before and after exposure, and a dye exclusion test (Trypan blue) was used to find the percentage of blue-stained cells indicating cell death, which was then related to acoustic emission. For 10 acoustic pulses and a high prerinse gas body concentration, there was less cell death and correspondingly lower change in the acoustic emissions at a PRF of 1 kHz than with PRFs of 100 Hz, 10 Hz, 1 Hz and 0.1 Hz (p < 0.001). The reduced effect at high PRF may be indicative of some evolution of the shelled microbubble that requires significant total exposure duration (> 10 ms, but < 100 ms).
研究了脉冲重复频率（PRF）和曝光次数对附着有造影剂的吞噬细胞的膜损伤及随后死亡的影响。将小鼠巨噬细胞系的吞噬细胞以单层形式培养在聚酯薄膜薄片上。通过孵育使Optison微泡附着于这些细胞。在脱气水浴中，以2.25 MHz的频率、46个周期脉冲以及1 kHz、100 Hz、10 Hz、1 Hz和0.1 Hz的临床相关PRF实施聚焦超声曝光（Pr = 2 MPa）。使用1 MHz的接收换能器测量散射信号。将频谱归一化为来自线性散射体的对照频谱。在曝光前后拍摄细胞单层的显微照片，并使用染料排除试验（台盼蓝）来确定指示细胞死亡的蓝色染色细胞的百分比，然后将其与声发射相关联。对于10个声脉冲和高预冲洗气体浓度，与100 Hz、10 Hz、1 Hz和0.1 Hz的PRF相比，1 kHz的PRF下细胞死亡较少，声发射的相应变化也较低（p < 0.001）。高PRF下效应的降低可能表明有壳微泡的某种演变，这需要显著的总曝光持续时间（> 10 ms，但< 100 ms）。
