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Objectives/Hypothesis: To determine the relationship between signal intensity on gadolinium (Gd)‐enhanced magnetic resonance images and growth of vestibular schwannomas (VSs). Study Design: Cross‐sectional study. Methods: In this cross‐sectional study, we retrospectively reviewed the data of 31 patients with VSs who underwent magnetic resonance imaging (MRI). The mean signal intensities within the regions of interest in the tumor, pons, and temporal muscles were measured on Gd‐enhanced T1‐weighted MRI. Relative intensity ratios were calculated as follows: T/N pons ratio (T/Np) is the tumor signal intensity/pons signal intensity and T/N muscle ratio (T/Nm) is the tumor signal intensity/temporal muscle signal intensity. Volume measurements were used to assess the tumor size. Growth rate was determined by assessing previous imaging studies. Growing VS was defined as a tumor with a growth rate >100 mm3/year. Results: The mean (standard deviation) T/Np and T/Nm were 1.47 (0.27) and 1.50 (0.24), respectively, in nongrowing tumors and 1.78 (0.17) and 1.90 (0.12), respectively, in growing tumors. The T/Np and T/Nm differed significantly between the two groups (T/Np, P <.001; T/Nm, P <.001). Receiver operating characteristic curve analysis showed that cutoffs of 1.56 and 1.76 for T/Np (93.33% sensitivity, 75.00% specificity) and T/Nm (100.00% sensitivity, 93.75% specificity), respectively, could be used to diagnose a growth rate of >100 mm3/year. The area under the curve was 0.85 (95% confidence interval, 0.70–1.00) for T/Np and 0.94 (0.82–1.00) for T/Nm. Conclusion: Growing VSs show higher signal intensities on Gd‐enhanced MRI. Thus, measuring the signal intensity of VS on Gd‐enhanced MRI may aid in predicting VS growth. Level of Evidence: 3 Laryngoscope, 132:198–203, 2022 [ABSTRACT FROM AUTHOR]

Objective: The tumor-to-normal tissue (T/N) boron ratio is determined in a patient prior to boron neutron capture therapy (BNCT) using 4-borono-2-18F-fluoro-L-phenylalanine (18F-FBPA) positron emission tomography (PET). The T/N ratio is used as a reference parameter to calculate BNCT dose and to evaluate treatment effects. The boronophenylalanine (BPA) dosage for BNCT treatment is higher than the 18F-FBPA dosage for PET diagnosis. Therefore, we aimed to determine whether the T/N ratios between diagnosis and treatment were correlated.Methods: In this study, SAS tongue cancer cells were used to develop an orthotopic nude mouse model. Micro-PET was performed after the mice were injected a dose of 3.7 ± 0.74 MBq of 18F-FBPA via the tail vein. The 18F radioactivity in the tumor, muscle, and heart blood pool was calculated using AMIND software. Organs and blood were collected for boron concentration analysis using inductively coupled plasma-atomic emission spectroscopy after the mice were injected with 400 mg/kg BPA at 15, 30, 45, and 60 min.Results: Pharmacokinetics of the tumor and muscle from 45 to 60 min after 18F-FBPA and BPA injections were slightly increased, whereas that of blood was slightly decreased. Median T/N ratios at 60 min after 18F-FBPA and BPA injections were 3.5 and 3.43, respectively. Median value of the T/N ratio between them was 3.49 at 60 min. The T/N ratio at 60 min after 18F-FBPA injection was similar to that after BPA injection. However, median tumor-to-blood (T/B) boron ratios of 18F-FBPA and BPA at 60 min were 1.63 and 3.35, respectively. Median value between them was 1.83 at 60 min.Conclusions: In this study, the T/B ratios demonstrate the spread of a distribution between 18F-FBPA and BPA injections. At 60 min, the T/N ratio of the 18F-FBPA injection was similar to that of the BPA injection. Boron concentration in normal tissue was almost equal to that in blood. Therefore, the representative T/N ratio could be obtained at 60 min after 18F-FBPA injection, and it was used as a reference parameter for calculating accurate radiation dose. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the detectability of small hot lesions with the 3-dimensional transmission/emission (3D T/E) acquisition mode in FDG-PET scan. The correlation of target detectability, target size, target to non-target uptake ratio (T/N ratio) and standardized uptake value (SUV) were studied. Small hot lesions ranged from 4.4 mm to 36.9 mm in diameter were located in cylindrical phantom. The images of phantoms with a T/N ratio of 2.0, 4.0, 6.0, 8.0, 9.6, 13.2, 17.5, 23.8 and 30.3 were obtained with 2-dimensional transmission/emission (2D T/E) scan and 3D T/E scans. Targets in diameter more than 10.6 mm in diameter with an actual T/N ratio ranged from 6.0 to 30.3 could be identified on the images obtained with all the 2D T/E and 3D T/E acquisition modes. The detectability efficiency of small hot target in 2D T/E and 3D T/E scans was as same (77.8%). The T/N ratio of targets from 2D T/E images was 30% to 48.4% different to that from 3D T/E image, and the SUV of the target from the 2D T/E images was almost the same as that from 3D T/E images. This study revealed that 3D T/E scanning had similar hot spot detectability to 2D T/E scanning; 3D T/E and 2D T/E scanning had the same faculty for semiquantitative analysis using SUV. These findings may be helpful for the diagnosis and understanding of 3D T/E FDG-PET in hot lesion detection. [ABSTRACT FROM AUTHOR]

Boron-10-containing positron emission tomography (PET) radio-tracer, 18F-FBPA, has been used to evaluate the feasibility and treatment outcomes of Boron neutron capture therapy (BNCT). The clinical use of PET/MR is increasing and reveals its benefit in certain applications. However, the PET/CT is still the most widely used modality for daily PET practice due to its high quantitative accuracy and relatively low cost. Considering the different attenuation correction maps between PET/CT and PET/MR, comparison of derived image features from these two modalities is critical to identify quantitative imaging biomarkers for diagnosis and prognosis. This study aimed to investigate the comparability of image features extracted from 18F-FBPA PET/CT and PET/MR. A total of 15 patients with malignant brain tumor who underwent 18F-FBPA examinations using both PET/CT and PET/MR on the same day were retrospectively analyzed. Overall, four conventional imaging characteristics and 449 radiomic features were calculated from PET/CT and PET/MR, respectively. A linear regression model and intraclass correlation coefficient (ICC) were estimated to evaluate the comparability of derived features between two modalities. Features were classified into strong, moderate, and weak comparability based on coefficient of determination (r2) and ICC. All of the conventional features, 81.2% of histogram, 37.5% of geometry, 51.5% of texture, and 25% of wavelet-based features, showed strong comparability between PET/CT and PET/MR. With regard to the wavelet filtering, radiomic features without filtering (61.2%) or with low-pass filtering (59.2%) along three axes produced strong comparability between the two modalities. However, only 8.2% of the features with high-pass filtering showed strong comparability. The linear regression models were provided for the features with strong and moderate consensus to interchange the quantitative features between the PET/CT and the PET/MR. All of the conventional and 71% of the radiomic (mostly histogram and texture) features were sufficiently stable and could be interchanged between 18F-FBPA PET with different hybrid modalities using the proposed equations. Our findings suggested that the image features high interchangeability may facilitate future studies in comparing PET/CT and PET/MR. [ABSTRACT FROM AUTHOR]

An experimental study with phantoms was performed in order to evaluate the effect of the tumor volume on the quantitative estimation in tumor SPECT. The ratio of mean count/pixel in the phantom to that of the background (T/N ratio) was well correlated with the size of the phantom: even when the concentration of the Tc-99m O4 solution of globular phantoms with diameters of 29, 37 and 46 mm was constant, the greater the size of the phantom, the higher was the T/N ratio. This study showed that we should understand that the T/N ratio was certainly affected by the reduction of the tumor size itself whenever we evaluate treatment response or assess tumor viability after treatment by reference to the T/N ratio. [ABSTRACT FROM AUTHOR]- solution of globular phantoms with diameters of 29, 37 and 46 mm was constant, the greater the size of the phantom, the higher was the T/N ratio. This study showed that we should understand that the T/N ratio was certainly affected by the reduction of the tumor size itself whenever we evaluate treatment response or assess tumor viability after treatment by reference to the T/N ratio. [ABSTRACT FROM AUTHOR]

Simple Summary: Although boron neutron capture therapy (BNCT) is a promising therapeutic approach for malignant brain tumors, the optimal BNCT parameters for patients with life-threatening, end-stage brain tumors remain unclear. The results of this study show that for life-threatening, end-stage brain tumor patients, BNCT is a promising therapeutic modality that is associated with an overall survival time of 7.25 months and no severe adverse events (grade ≥ 3). Remarkably, patients who achieved a complete response had overall survival times and cancer-specific survival times of up to 17.66 and 22.5 months, respectively. In addition, since these patients are usually physically weak and already on the verge of life-threatening conditions, reducing the BNCT dose still has good therapeutic outcomes. Statistical analysis revealed the optimal BNCT parameters and tumor characteristics, including a tumor-to-normal tissue (T/N) uptake ratio of ≥4, a tumor volume of <20 mL, a mean tumor dose of ≥25 Gy-E, MIB-1 ≤ 40, and a lower recursive partitioning analysis (RPA) class. The results of this study provide a reference for other clinicians or radiation oncologists conducting BNCT treatment for such patients. Although boron neutron capture therapy (BNCT) is a promising treatment option for malignant brain tumors, the optimal BNCT parameters for patients with immediately life-threatening, end-stage brain tumors remain unclear. We performed BNCT on 34 patients with life-threatening, end-stage brain tumors and analyzed the relationship between survival outcomes and BNCT parameters. Before BNCT, MRI and 18F-BPA-PET analyses were conducted to identify the tumor location/distribution and the tumor-to-normal tissue uptake ratio (T/N ratio) of 18F-BPA. No severe adverse events were observed (grade ≥ 3). The objective response rate and disease control rate were 50.0% and 85.3%, respectively. The mean overall survival (OS), cancer-specific survival (CSS), and relapse-free survival (RFS) times were 7.25, 7.80, and 4.18 months, respectively. Remarkably, the mean OS, CSS, and RFS of patients who achieved a complete response were 17.66, 22.5, and 7.50 months, respectively. Kaplan–Meier analysis identified the optimal BNCT parameters and tumor characteristics of these patients, including a T/N ratio ≥ 4, tumor volume < 20 mL, mean tumor dose ≥ 25 Gy-E, MIB-1 ≤ 40, and a lower recursive partitioning analysis (RPA) class. In conclusion, for malignant brain tumor patients who have exhausted all available treatment options and who are in an immediately life-threatening condition, BNCT may be considered as a therapeutic approach to prolong survival. [ABSTRACT FROM AUTHOR]