T-DominO: Exploring Multiple Criteria with Quality-Diversity and the Tournament Dominance Objective

Real-world design problems are a messy combination of constraints, objectives, and features. Exploring these problem spaces can be defined as a Multi-Criteria Exploration (MCX) problem, whose goals are to produce a set of diverse solutions with high performance across many objectives, while avoiding low performance across any objectives. Quality-Diversity algorithms produce the needed design variation, but typically consider only a single objective. We present a new ranking, T-DominO, specifically designed to handle multiple objectives in MCX problems. T-DominO ranks individuals relative to other solutions in the archive, favoring individuals with balanced performance over those which excel at a few objectives at the cost of the others. Keeping only a single balanced solution in each MAP-Elites bin maintains the visual accessibility of the archive – a strong asset for design exploration. We illustrate our approach on a set of easily understood benchmarks, and showcase its potential in a many-objective real-world architecture case study

Evaluation of the radiation dose to the hands of orthopaedic surgeons during fluoroscopy using stored images

Data were collected from 642 orthopaedic interventions during which the images produced by X-rays were recorded. By examining these images, it is possible to determine the time that the orthopaedic surgeons’ hands were exposed to the direct radiation beam. The procedures with greater exposure to the direct beam were those involving the hand (median 15 s) and the wrist (median 13 s). Two surgeons wore a ring to measure the absorbed dose at the fingers: one on the dominant hand and the other on the non-dominant hand. The two surgeons performed 34 and 48 operations, respectively, in 14 months. The total doses measured with the rings were 2.30 and 1.04 mSv, respectively. The images of the interventions were examined, determining how much each individual hand was exposed. The interventional reference point (IRPeff (left or right)) was calculated by comparing the doses at the IRP with the exposure times of the right or the left hand. Summing the IRPeff of the two surgeons in 14 months, it is obtained the maximum values of 2.87 mGy for the left hand of one and 6.74 mGy for the right hand of the other, which are of the order of 1/100 of the annual dose limit for the extremities. © The Author(s) 2020. Published by Oxford University Press. All rights reserved

Small field output factors evaluation with a microDiamond detector over 30 Italian centers

The aim of the study was a multicenter evaluation of MLC&jaws-defined small field output factors (OF) for different linear accelerator manufacturers and for different beam energies using the latest synthetic single crystal diamond detector commercially available. The feasibility of providing an experimental OF data set, useful for on-site measurements validation, was also evaluated

Improving dose delivery accuracy with EPID in vivo dosimetry: results from a multicenter study

Purpose: To investigate critical aspects and effectiveness of in vivo dosimetry (IVD) tests obtained by an electronic portal imaging device (EPID) in a multicenter and multisystem context. Materials and methods: Eight centers with three commercial systems—SoftDiso (SD, Best Medical Italy, Chianciano, Italy), Dosimetry Check (DC, Math Resolution, LCC), and PerFRACTION (PF, Sun Nuclear Corporation, SNC, Melbourne, FL)—collected IVD results for a total of 2002 patients and 32,276 tests. Data are summarized for IVD software, radiotherapy technique, and anatomical site. Every center reported the number of patients and tests analyzed, and the percentage of tests outside of the tolerance level (OTL%). OTL% was categorized as being due to incorrect patient setup, incorrect use of immobilization devices, incorrect dose computation, anatomical variations, and unknown causes. Results: The three systems use different approaches and customized alert indices, based on local protocols. For Volumetric Modulated Arc Therapy (VMAT) treatments OTL% mean values were up to 8.9% for SD, 18.0% for DC, and 16.0% for PF. Errors due to “anatomical variations” for head and neck were up to 9.0% for SD and DC and 8.0% for PF systems, while for abdomen and pelvis/prostate treatments were up to 9%, 17.0%, and 9.0% for SD, DC, and PF, respectively. The comparison among techniques gave 3% for Stereotactic Body Radiation Therapy, 7.0% (range 4.7–8.9%) for VMAT, 10.4% (range 7.0–12.2%) for Intensity Modulated Radiation Therapy, and 13.2% (range 8.8–21.0%) for 3D Conformal Radiation Therapy. Conclusion: The results obtained with different IVD software and among centers were consistent and showed an acceptable homogeneity. EPID IVD was effective in intercepting important errors