Abstract
BackgroundThe potential of the D-isomerization of 4-borono-2-18F-fluoro-phenylalanine (18F-FBPA) to improve its target tumor to non-target normal brain tissue ratio (TBR) was evaluated in rat brain glioma and compared with those of L- and D-11C-methyl-tyrosine (11C-CMT).The L- or D-isomer of 18F-FBPA was injected into rats through the tail vein, and their whole body kinetics and distributions were assessed using the tissue dissection method up to 90 min after the injection. The kinetics of L- and D-18F-FBPA or L- and D-11C-CMT in the C-6 glioma-inoculated rat brain were measured for 90 or 60 min, respectively, using high-resolution animal PET, and their TBRs were assessed.ResultsTissue dissection analyses showed that D-18F-FBPA uptake was significantly lower than that of L-18F-FBPA in the brain and abdominal organs, except for the kidney and bladder, reflecting the faster elimination rate of D-18F-FBPA than L-18F-FBPA from the blood to the urinary tract. PET imaging using 18F-FBPA revealed that although the brain uptake of D-18F-FBPA was significantly lower than that of L-18F-FBPA, the TBR of the D-isomer improved to 6.93 from 1.45 for the L-isomer. Similar results were obtained with PET imaging using 11C-CMT with a smaller improvement in TBR to 1.75 for D-11C-CMT from 1.33 for L-11C-CMT.ConclusionsThe present results indicate that D-18F-FBPA is a better brain tumor imaging agent with higher TBR than its original L-isomer and previously reported tyrosine-based PET imaging agents. This improved TBR of D-18F-FBPA without any pre-treatments, such as tentative blood-brain barrier disruption using hyperosmotic agents or sonication, suggests that the D-isomerization of BPA results in the more selective accumulation of 10B in tumor cells that is more effective and less toxic than conventional L-BPA.
Highlights
The potential of the D-isomerization of 4-borono-2-18F-fluoro-phenylalanine (18F-FBPA) to improve its target tumor to non-target normal brain tissue ratio (TBR) was evaluated in rat brain glioma and compared with those of L- and D-11C-methyl-tyrosine (11C-CMT)
These retention times of 6.6 and 4.5 min for L- and D-18F-FBPA, respectively (Fig. 1c), and 11.1 and 9.2 min for L- and D-11C-CMT, respectively (Fig. 1d) were consistent with those obtained by the corresponding authentic standard compounds of L
The present study demonstrated that the D-isomers of 18F-FBPA and 11C-CMT had higher TBRs in rat brain C6 glioma than the corresponding L-isomers
Summary
The potential of the D-isomerization of 4-borono-2-18F-fluoro-phenylalanine (18F-FBPA) to improve its target tumor to non-target normal brain tissue ratio (TBR) was evaluated in rat brain glioma and compared with those of L- and D-11C-methyl-tyrosine (11C-CMT). The kinetics of Land D-18F-FBPA or L- and D-11C-CMT in the C-6 glioma-inoculated rat brain were measured for 90 or 60 min, respectively, using high-resolution animal PET, and their TBRs were assessed. Since L-BPA accumulates in tumor cells with a low target tumor to non-target normal brain tissue ratio (TBR) [6], L-18F-FBPA was developed to predict the exact concentration of 10B-BPA in tumor cells prior to BNCT [7,8,9,10,11,12]. The combined use of PET and inductively coupled plasma optical emission spectrometry confirmed that L-18F-FBPA-PET has the ability to estimate 10B concentrations delivered by L-BPA in the tumor and normal tissues of rats [10, 15] and humans [8]
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call