PMC9937644_01
The reaction mechanism of BNCT.. (a) Thermal neutrons react with 10B and generate two types of radiation particles, Alpha particles and lithium particles (7Li3+), both of which are less than 10 microm in radiation range. (b) 10B selectively accumulates in tumor cells without entering normal cells and reacts with thermal neutron, leaving normal cells undamaged. (Image Credits: SHOSEI SHIMIZU). BNCT: Boron neutron capture therapy
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FIG1
The reaction process is illustrated in Figure 1. 10B absorbs the thermal neutrons and immediately splits into Alpha particles and lithium particles (7Li3+) (Figure 1a). It implies that the side effects should be minimal for normal tissues based on the principle (Figure 1b).
Dose distribution of BNCT for the recurrent GBM in the left temporal lobe on MRI.. (a) Cross-sectional dose distribution diagram. (b) Coronal plane dose distribution diagram.. BNCT: Boron neutron capture therapy; GBM: Glioblastoma
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FIG2
In this case, the dose distribution during BNCT is shown in Figure 2.
Contrast-enhanced T1-weighted axial brain MRI before, during, and after boron neutron capture therapy (BNCT).. (a) One day before BNCT. (b) One week after BNCT. (c) One month after BNCT. (d) Three months after BNCT. (e) Six months after BNCT. Contrast-enhanced lesions appeared, but it was unclear whether these lesions were due to necrosis or recurrence. (f) Eight months after BNCT. The lesion was determined to be due to necrosis, and the necrotic lesion excision was performed. (g) 12 months after BNCT. (h) 18 months after BNCT. (i) 24 months after BNCT. (j) 30 months after BNCT. (k) 36 months after BNCT. (l) 48 months after BNCT. (m) 51 months after BNCT. A contrast-enhanced lesion appeared on the dorsal side of the irradiation field. (n) 54 months after BNCT. (o) 58 months after BNCT.
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FIG3
The image immediately before BNCT showed a contrast-enhanced lesion at the surgical wound margin in the left temporal lobe in Figure 3a. On contrast-enhanced MRI one week after BNCT, the contrast effect for the surgical wound had increased in thickness, but it was difficult to discern from these images whether this was due to the treatment or the tumor (Figure 3b). And it was difficult to determine if the tumor was enlarged (Figure 3c). At three months after BNCT, there was no change in contrast effect or size around the surgical defect (Figure 3d). At six months, the contrast effect around the surgical defect was reduced and the margin of the defect showed a slightly higher signal than those insides, suggesting a mixture of hemorrhage and necrosis at the lesion (Figure 3e). Cerebral edema and swelling had clearly exacerbated, possibly due to postoperative changes (Figure 3f). At 12 months after BNCT, as shown in Figure 3g, there was a significant decrease in the contrast effect around the defect compared to that at eight months, which indicates a good sign that the tumor was not aggravated. Figure 3h demonstrates that 18 months after BNCT, the contrast effect at the limbus had also diminished, and edema and swelling in the cerebral hemispheres had resolved, again indicating no tumor recurrence. Contrast-enhanced MRI at 24 months after BNCT showed a further weakening of the limbic contrast effect and improvement of edema and swelling in the cerebral hemispheres, with no evidence of tumor recurrence (Figure 3i). At 30 months after BNCT, there was no obvious change in the medial aspect of the original wound, but some hyperintense signals were seen dorsally and laterally, making it difficult to determine whether the tumor had recurred (Figure 3j). At 36 months after BNCT in Figure 3k, there was a diminished contrast-enhancement surrounding the defect and improvement of edema and swelling of the cerebral hemispheres compared to the six-month earlier images. At 48 months, a heterogeneous contrast effect was observed in Figure 3l spreading to the superficial side of the defect site with a mixture of low and high signals, suggesting the lesion that was radiation necrosis rather than tumor recurrence. Although the possibility of tumor recurrence was considered in the differential diagnosis, the spread of necrosis in the dorsal region was ultimately identified as the determining factor at that time (Figure 3m). Contrast-enhanced MRI at 54 months after BNCT (Figure 3n) showed that the dorsal heterogeneous contrast-enhanced lesion continued to increase in size to 45x49x53 mm with mixed radiation necrosis. The last MRI of the patient was performed at month 58 after BNCT (Figure 3o), and the image revealed a coarse, substantial mass in the parietal to the occipital region that had increased in size markedly in a short period of time.