- 學位論文
單頻與共焦雙頻聚焦式超音波配合超音波顯影劑應用於局部血腦屏障開啟之探討
Investigation of Single Frequency and Confocal Dual Frequency Focused Ultrasound with Contrast Agent on Local Blood-Brain Barrier Disruption
摘要
前人研究指出利用聚焦式超音波結合超音波顯影劑能非侵入地開啟特定區域的血腦屏障。本研究探討以單頻與共焦雙頻超音波配合超音波顯影劑開啟局部血腦屏障的差異。單頻超音波頻率為518kHz，雙頻超音波頻率為513kHz+523kHz，設定最大負聲壓值相近，重複頻率為1Hz，脈衝長度為10ms。以水診器量測單頻與雙頻訊號，得到壓力分佈狀態。超音波施打於雄性大白鼠右側大腦，開啟此處血腦屏障，並以Evans Blue滲出作為定量。另外，施予單頻超音波，給予不同劑量顯影劑，期望能找出一個最佳化的參數將傷害降到最低，並以核磁共振造影配合Gd-DTPA觀測血腦屏障開啟，期望能找到核磁共振造影影像與Evans Blue萃取之關係。 單頻與雙頻超音波對於Evans Blue滲出總量並沒有明顯差異，但Evans Blue分佈卻有些不同。推測由於脈衝長度太短導致雙頻並沒有明顯增加血腦屏障開啟。此外，由實驗得知壓力的分佈與血腦屏障開啟範圍的確有所關連，雙頻造成血腦屏障開啟的範圍的確大於單頻造成的範圍。在尋找最佳化參數實驗中發現施打超音波20秒給予超音波顯影劑劑量10μl/kg為最佳參數，在此參數下能夠只開啟聚焦區域的血腦屏障，並且幾乎不會造成出血情況產生。以核磁共振造影監測此實驗能得到影像與Evans Blue萃取相關性極高，以T1-weighted SE影像變化與Evans Blue作分析得到相關係數高達0.911；以T1-weighted GE影像變化與Evans Blue作分析得到相關係數高達0.981。結果表示能以核磁共振造影影像來代替傳統萃取的結果，能更有效率地即時得到物質滲入血腦屏障的變化。
並列摘要
It has been shown that focused ultrasound (FUS) could disrupt local blood-brain barrier (BBB) noninvasively via the injection of ultrasound contrast agent (UCA). In this study, we use single frequency (518kHz) ultrasound and confocal dual frequency (513kHz+523kHz) ultrasound with the injection of UCA to disrupt the local BBB. Single frequency ultrasound and dual frequency ultrasound were set at almost the same acoustic negative peak pressure, and the pulse length was 10 ms. The brain of male Wistar rats were sonicated by ultrasound with the injection of UCA. The BBB disruption was evaluated by the extravasation of Evans Blue (EB). Additionally, we try out to find the optimal ultrasound parameters without producing hemorrhage, we use single frequency ultrasound with different doses of UCA. Expect this parameter could apply on future application. There was no difference at the total extravasation amount of EB between single and dual frequency ultrasound, but the EB distribution were slightly different. Because of the short duty cycle (1%), the enhancement of cavitation effect produced by dual frequency was not obvious. In addition, the BBBD area was related to the pressure distribution. The BBBD area produced by dual frequency ultrasound was larger than single frequency ultrasound. We optimize the ultrasound parameter to 20s sonication with 10μl/kg ultrasound contrast agent dose, in this case, we could open the BBB precisely on the focal region and cause nearly no hemorrhage. When the MR enhancement was quantitatively evaluated by the EB extravasation, the correlation was very high. When it went to T1-weighted SE, the correlation coefficient between them was 0.911 (p < 0.01). When it went to T1-weighted GE, the correlation coefficient between them was 0.981 (p < 0.01). In our result, we could use MR images to take the place of EB extravasation, and we could monitor the penetration of drugs or molecules in time.