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Background: Demyelinating peripheral neuropathy is characteristic of both polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes (POEMS) syndrome and chronic inflammatory demyelinating polyneuropathy (CIDP). We hypothesized that the different pathogeneses underlying these entities would affect the sonographic imaging features. Purpose: To investigate whether ultrasound (US)-based radiomic analysis could extract features to describe the differences between CIDP and POEMS syndrome. Material and Methods: In this retrospective study, we evaluated nerve US images from 26 with typical CIDP and 34 patients with POEMS syndrome. Cross-sectional area (CSA) and echogenicity of the median and ulnar nerves were evaluated in each US image of the wrist, forearm, elbow, and mid-arm. Radiomic analysis was performed on these US images. All radiomic features were examined using receiver operating characteristic analysis. Optimal features were selected using a three-step feature selection method and were inputted into XGBoost to build predictive machine-learning models. Results: The CSAs were more enlarged in patients with CIDP than in those with POEMS syndrome without significant differences, except for that of the ulnar nerve at the wrist. Nerve echogenicity was significantly more heterogeneous in patients with CIDP than in those with POEMS syndrome. The radiomic analysis yielded four features with the highest area under the curve (AUC) value of 0.83. The machine-learning model showed an AUC of 0.90. Conclusion: US-based radiomic analysis has high AUC values in differentiating POEM syndrome from CIDP. Machine-learning algorithms further improved the discriminative ability. [ABSTRACT FROM AUTHOR]

We report the commissioning results of Elekta Unity for the dosimetric performance and mechanical quality assurance (QA), and propose additional commissioning procedures. Mechanical tests included multi-leaf collimator (MLC) positional accuracy, radiation isocenter diameter at the center and off-center position, and coincidence between the magnetic resonance (MR) image center and radiation isocenter. Comparisons between the measurements and calculations of the simple irradiated field, intensity modulated radiation therapy (IMRT) commissioning, MLC output factor ratio, validation of independent dose calculation software and end-to-end testing were performed to evaluate dosimetric performance. The average values of the MLC positional accuracy for film- and imaging device-based analysis were −0.1 and 0.3 mm, respectively. The measured radiation isocenter size was 0.41 mm, and the off-center results were within 1 mm. The coincidence was −0.21, −1.19 and 0.49 mm along the x-, y- and z-axes, respectively. The calculated percent depth doses (PDD) and profiles agreed with the measurements. The results of independent dose calculation were within the action level recommended by American Associations of Physicist in Medicine. The gamma passing rate (GPR) for IMRT commissioning was 98.6 ± 0.9%, and end-to-end testing of adapted plans showed agreement within 2% between the measurement and calculation. We reported the results of mechanical and dosimetric performances of Elekta Unity, and proposed novel commissioning procedures. Our results should provide knowledge to the physics community for enhancing the QA programs. [ABSTRACT FROM AUTHOR]

Purpose: We determined correction factors for absorbed dose energy dependence and intrinsic energy dependence for measurements of absorbed dose to water around an 192Ir source using a radiophotoluminescent glass dosimeter (RPLD) calibrated with a 4‐MV photon beam. Methods: The ratio of the absorbed dose to the water and the average absorbed dose to RPLD for the 192Ir beam relative to the same ratio in a 4 MV photon beam defines the absorbed dose energy dependence and was determined at distances of 2–10 cm (at intervals of 1 cm) from the 192Ir source in a water phantom using the egs_chamber user code. The RPLD was calibrated to measure absorbed dose to water, Dw, in a 4 MV photon beam using an ionization chamber, which was also used to measure absorbed dose to water, Dw, in a water phantom using the 192Ir source. The detector response radiophotoluminescence (RPL signal per average absorbed dose in the detector) in the 192Ir beam relative to that in the 4 MV photon beam (the relative intrinsic efficiency) was determined experimentally. Finally, the beam quality correction factor was obtained as the quotient between the absorbed dose energy dependence and the relative intrinsic efficiency and corrects for the difference between the beam quality Q0 used at calibration and the beam quality Q used in the measurements. Results: The relative dose ratio of the average absorbed dose to water relative to RPLD ranged from 0.930 to 0.746, and the beam quality correction factor ranged from 0.999 to 0.794 for distances of 2–10 cm from the 192Ir source. The relative detector response to an 192Ir source and a 4‐MV photon beam was 0.930, and it did not vary significantly with distance. Conclusions: These results demonstrate that corrections for absorbed dose energy dependence and intrinsic energy dependence are required when using an RPLD to measure with sources different from the reference source providing the primary calibration. [ABSTRACT FROM AUTHOR]