Non-invasive estimation of 10 B-4-borono-L-phenylalanine-derived boron concentration in tumors by PET using 4-borono-2-18 F-fluoro-phenylalanine.

In boron neutron capture therapy (BNCT), 10 B-4-borono-L-phenylalanine (BPA) is commonly used as a 10 B carrier. PET using 4-borono-2-18 F-fluoro-phenylalanine (18 F-FBPA PET) has been performed to estimate boron concentration and predict the therapeutic effects of BNCT; however, the association between tumor uptake of 18 F-FBPA and boron concentration in tumors remains unclear. The present study investigated the transport mechanism of 18 F-FBPA and BPA, and evaluated the utility of 18 F-FBPA PET in predicting boron concentration in tumors. The transporter assay revealed that 2-aminobicyclo-(2.2.1)-heptane-2-carboxylic acid, an inhibitor of the L-type amino acid transporter, significantly inhibited 18 F-FBPA and 14 C-4-borono-L-phenylalanine (14 C-BPA) uptake in FaDu and LN-229 human cancer cells. 18 F-FBPA uptake strongly correlated with 14 C-BPA uptake in 7 human tumor cell lines (r = .93; P < .01). PET experiments demonstrated that tumor uptake of 18 F-FBPA was independent of the administration method, and uptake of 18 F-FBPA by bolus injection correlated well with BPA uptake by continuous intravenous infusion. The results of this study revealed that evaluating tumor uptake of 18 F-FBPA by PET was useful for estimating 10 B concentration in tumors.

Dynamic changes in 18F-borono-L-phenylalanine uptake in unresectable, advanced, or recurrent squamous cell carcinoma of the head and neck and malignant melanoma during boron neutron capture therapy patient selection.

BACKGROUND: We evaluated dynamic changes in 18F-borono-L-phenylalanine (18F-BPA) uptake in unresectable, advanced, or recurrent squamous cell carcinoma of the head and neck (SCC) and malignant melanoma (MM) during boron neutron capture therapy (BNCT) patient selection. METHODS: Dynamic changes in the maximum standardized uptake value (SUVmax), tumor-to-normal tissue ratio (TNR), and tumor-to-blood pool ratio (TBR) for 18F-BPA were evaluated in 20 patients with SCC and 8 patients with MM. RESULTS: SUVmax in SCC tumors decreased significantly from 30 to 120 min. There was a non-statistically significant decrease in SUVmax for SCC tumors from 30 to 60 min and from 60 to 120 min. Patients with MM had nonsignificant SUVmax changes in 18F-BPA uptake on delayed imaging. Nonsignificant 18F-BPA TNR and TBR changes were seen in patients with SCC and MM. CONCLUSIONS: Dynamic changes in SUVmax for 18F-BPA uptake had a washout pattern in SCC and a persistent pattern in MM. Dynamic 18F-BPA -PET studies should be performed to investigate the pharmacokinetics of 18F-BPA in humans and select appropriate candidates who may benefit from BNCT.

Estimation of radioactivity in single-photon emission computed tomography for sentinel lymph node biopsy in a torso phantom study.

OBJECTIVE: The number of lymph nodes to be removed is determined from residual counts. Advance estimation of residual radioactivity in lymphatic nodes before a biopsy is useful for reducing surgical operation time. The purpose of this study was to estimate the total radioactivity of a small hotspot in single-photon emission computed tomography (SPECT) of a torso phantom. METHODS: A cross-calibration study was performed to convert counts in SPECT images to radioactivity. A simulation study was performed to estimate the size of the volume of interest (VOI) covering a hotspot corrupted with full-width at half-maximum between 8 and 16 mm. The estimation of total radioactivity was validated in a torso phantom study using small sources. RESULTS: True radioactivity was approximately equal to integrated values of hotspots using the VOI with a diameter of 40 mm in our simulation study. The difference was less than 18% in cases of more than 9.4 kBq. CONCLUSION: The total radioactivity in small sources simulating a typical sentinel node was estimated from SPECT images using a VOI of 40 mm in a torso phantom study. Because the difference from actual values was less than 10% on average when radioactivities were more than 9.4 kBq, the total radioactivity of a lymph node can be estimated in a clinical examination.

Correlation of (18)F-BPA and (18)F-FDG uptake in head and neck cancers.

BACKGROUND AND PURPOSE: The aim of this study was to compare the accumulation of 4-borono-2-(18)F-fluoro-phenylalanine ((18)F-BPA) with that of (18)F-fluorodeoxyglucose ((18)F-FDG) in head and neck cancers, and to assess the usefulness of (18)F-FDG PET for screening candidates for boron neutron capture therapy (BNCT). MATERIAL AND METHODS: Twenty patients with pathologically proven malignant tumors of the head and neck were recruited from March 2012 to January 2014. All patients underwent both whole-body (18)F-BPA PET/CT and (18)F-FDG PET/CT within 2weeks of each other. The uptakes of (18)F-BPA and (18)F-FDG at 1h after injection were evaluated using the maximum standardized uptake value (SUVmax). RESULTS: The accumulation of (18)F-FDG was significantly correlated with that of (18)F-BPA. The SUVmax of (18)F-FDG ⩾5.0 is considered to be suggestive of high (18)F-BPA accumulation. CONCLUSIONS: (18)F-FDG PET might be an effective screening method performed prior to (18)F-BPA for selecting patients with head and neck cancer for treatment with BNCT.