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Purpose: To establish an artificial intelligence (AI)-empowered multistep integrated (MSI) radiation therapy (RT) workflow for patients with nasopharyngeal carcinoma (NPC) and evaluate its feasibility and clinical performance., Methods and Materials: Patients with NPC scheduled for MSI RT workflow were prospectively enrolled. This workflow integrates RT procedures from computed tomography (CT) scan to beam delivery, all performed with the patient on the treatment couch. Workflow performance, tumor response, patient-reported acute toxicities, and quality of life were evaluated., Results: From March 2022 to October 2023, 120 newly diagnosed, nonmetastatic patients with NPC were enrolled. Of these, 117 completed the workflow with a median duration of 23.2 minutes (range, 16.3-45.8). Median translation errors were 0.2 mm (from CT scan to planning approval) and 0.1 mm (during beam delivery). AI-generated contours required minimal revision for the high-risk clinical target volume and organs at risk, minor revision for the involved cervical lymph nodes and low-risk clinical target volume (median Dice similarity coefficients (DSC), 0.98 and 0.94), and more revision for the gross tumor at the primary site and the involved retropharyngeal lymph nodes (median DSC, 0.84). Of 117 AI-generated plans, 108 (92.3%) passed after the first optimization, with ≥97.8% of target volumes receiving ≥100% of the prescribed dose. Dosimetric constraints were met for most organs at risk, except the thyroid and submandibular glands. One hundred and fifteen patients achieved a complete response at week 12 post-RT, while 14 patients reported any acute toxicity as "very severe" from the start of RT to week 12 post-RT., Conclusions: AI-empowered MSI RT workflow for patients with NPC is clinically feasible in a single institutional setting compared with standard, human-based RT workflow., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background and Objective: Accurate data acquisition is very important to establish a reliable dose calculation model of the treatment planning system for small radiation fields in intensity modulated radiation therapy (IMRT) and stereotactic radiotherapy (SRT). This study was to analyze and compare small-field measurements using different methods and ionization chambers., Methods: Three types of farmer chambers were used, with active volumes of 0.65 cc, and 0.13 cc, 0.01 cc, respectively. The beam data, including the total scatter factor (Scp), collimator scatter factor (Sc), tissue-maximum ratio (TMR), were acquired in a 30 cm x 30 cm x 30 cm3 water phantom under two linear accelerators. Measurements were performed at accelerating potentials of 4, 6, and 8 MV with the beam size ranging from 1 cm x 1 cm to 10 cm x 10 cm. The measurements were analyzed and compared., Results: For the beam size of >or=3 cm x 3 cm, the differences in Scp and Sc measurements of the 0.65 cc, 0.13 cc and 0.01 cc ion chambers were within 0.8%, while the differences were much greater for the beam size of less than 3 cm x 3 cm (the maximum difference reached 64%). Using 4, 6 and 8 MV X-rays, Sc measured by the 0.13 cc chamber with an elongated source-to-surface distance (SSD) (>150 cm) were 25.4%, 6.9%, 24.6%, and 1.4%, 1.4%, 2.2% greater than those measured by a standard SSD (100 cm) for 1 cm x 1 cm and 2 cm x 2 cm beams respectively; although there was no significant difference in Sc measurements for the beams of >or=2 cm x 2 cm using the elongated SSD of the 0.13 cc and the 0.01 cc ion chambers, Sc measured by the 0.13 cc ion chamber were 0.2%, 8.5%, 3.4% less than those measured by the 0.01 cc ion chamber for the 1 cm x 1 cm beam. For the 1 cm x 1 cm beam, the TMR of the depth deeper than 15 cm measured with the 0.01 cc ion chamber was about 4% different compared with that measured with the 0.13 cc ion chamber; for radiation fields of >or=2 cm x 2 cm, the differences of TMR between the 0.01 cc and 0.13 cc chambers were within 1%. For the radiation fields of >or=3 cm x 3 cm, the measured TMR values had a good consistency with the calculated values obtained from the percentage depth doses (PDDs) at the depth of 0 to 15 cm; but the two values were obviously different at the depths of deeper than 15 cm (>2%)., Conclusions: For the measurement of small fields, the choice of a suitable detector is important due to the lack of lateral electron equilibrium. Misuse of the detector may affect the accuracy of the measurements for small radiation fields. When the lateral electron equilibrium is not established, the size of the detector used to measure the absorbed dose on the central axis should be considerably smaller than the field size.