| Summary: | 碩士 === 國立陽明大學 === 生物醫學影像暨放射科學系 === 100 === The permeability of blood–brain barrier (BBB) for albumin can be enhanced by focused ultrasound (FUS) in a targeted region when this is applied with the ultrasound contrast agent (UCA). This technology has been widely used in the research of drug delivery. However, most approaches use the invasive methods or magnetic resonance image (MRI) to confirm the BBB permeability. In our studies, we use micro-positron emission tomography (micro-PET) with high spatial resolution and sensitivity than clinical nuclear medicine machines to collocate with FUS to evaluate pharmacokinetics of radiotracers.
The contents of our studies were divided into two parts. In part 1, we evaluated the pharmacokinetics of 18F-FDG after intravenous administration in normal Sprague-Dawley (SD) rats with BBB disruption (BBB-D) induced by FUS. In part 2, we evaluated the pharmacokinetics of 18F-FBPA after intravenous administration in F98 glioma–bearing F344 rats with BBB-D induced by FUS.
There were three groups in part 1 study：Sham, injected 18F-FDG immediately after FUS (0hr), and injected 18F-FDG after FUS 24hrs (24hrs). The FUS was delivered to the targeted region in the right hemisphere brain. The results showed that pharmacokinetic parameters of 0hr group were all significantly decreased than Sham and 24hrs.It meant that the permeability of 18F-FDG is reduced by FUS.
In part 2 study, F98 glioma-bearing F344 rats were injected intravenously with 18F-FBPA and with or without induced by FUS. micro-PET was performed at the 9th day after tumor implantation. 180 minutes of data acquisition by micro-PET was initiated at the first minute after 18F-FBPA administration. Between with or without induced by FUS, the tumor to normal tissue ratios (T/N ratio) increased 1.75 times after BBB-D induced by FUS. We also used arterial input function (AIF) to evaluate pharmacokinetic parameters ratio (K1/k2) which increased 4.25 times after BBB-D.
These results showed that the accumulation of 18F-FBPA in the brain tumors after BBB-D was higher than brain tumors without BBB-D, and the T/N ratio could reach the highest value at about 30 minutes. We conjectured that using FUS in boron neutron capture therapy (BNCT) could increase therapy quality and curative effect.
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