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The MEVION S250i is intended to deliver proton radiation therapy treatment to patients with localized tumors or other conditions susceptible to treatment by radiation.

The MEVION S250i is a proton beam radiation therapy system, which provides a therapeutic proton beam for clinical treatment. It is designed to deliver a proton beam with the prescribed dose and dose distribution to the prescribed patient treatment site. The MEVON S250i is a modern proton therapy system combining a patented, gantry-mounted proton source and a precision scanning beamline with a highly integrated, image-based workflow. The proton accelerator is a superconducting synchrocyclotron. The synchrocyclotron source generates protons of energy 230 MeV and is mounted in a high-precision concentric gantry system that rotates and points at treatment isocenter at all times. The system components include a Beam Generation System, Beam Delivery System, Structural Support and Alignment System, Patient Positioning System, Control System Software, and a Hard-wired Safety System (HSS).

This document is a 510(k) summary for the Mevion S250i, a proton radiation beam therapy system. It focuses on demonstrating substantial equivalence to predicate devices rather than proving device performance against specific acceptance criteria through a clinical study. Therefore, much of the requested information about acceptance criteria, study details, and ground truth cannot be extracted directly from this document.

However, based on the provided text, I can infer some aspects related to acceptance criteria and the methods used to validate the device's substantial equivalence.

Here's a breakdown of the requested information, with disclaimers where the information is not explicitly provided:

1. Table of Acceptance Criteria and Reported Device Performance

The document does not present a formal table of "acceptance criteria" in the sense of predefined performance targets for a clinical study. Instead, it compares the technological characteristics of the MEVION S250i (Applicant Device) with two predicate devices. The implicit "acceptance criterion" for this 510(k) submission is that the technological characteristics of the MEVION S250i are "Substantially Equivalent" to the predicate devices and that there are "no new or different issues of safety or efficacy."

The table below summarizes the key technical characteristics provided in the document for comparison:

2. Sample Size Used for the Test Set and Data Provenance

The document describes technical verification and validation activities rather than a clinical study with a "test set" of patient data. Therefore, there is no information on:

• Sample size used for a test set (e.g., number of patients or cases).
• Data provenance (e.g., country of origin, retrospective or prospective).

The testing performed includes "Implementation of Design Changes," "Regression Testing," "Satisfaction of all Performance Requirements," "Software Verification and Validation," and "Electrical Safety and Electromagnetic compatibility (EMC)." These tests would involve technical measurements and simulations, not patient data in the clinical sense.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Their Qualifications

Since this is not a clinical study involving diagnosis or interpretation, there is no information about:

• Number of experts used to establish ground truth.
• Qualifications of such experts.

The "ground truth" in this context would be engineering specifications and validated physical phenomena related to proton beam generation and delivery. Design reviews were held, involving unspecified "appropriately trained health care professionals" for treatment settings and internal company experts for design and engineering.

4. Adjudication Method for the Test Set

As there is no clinical "test set" in the diagnostic sense, there is no information on an adjudication method like 2+1 or 3+1. Adjudication would not apply to the technical verification and validation directly described.

5. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study Was Done, and Effect Size

No, an MRMC comparative effectiveness study was not performed, or at least not described in this 510(k) summary. This type of study is typically for evaluating the impact of AI on human reader performance in diagnostic tasks, which is not the purpose of this device (a radiation therapy system).

6. If a Standalone (Algorithm Only Without Human-in-the-Loop Performance) Was Done

The device is a proton radiation therapy system, not a diagnostic algorithm. Its performance is inherent in its engineering design and delivery capabilities, which are evaluated through standalone technical verification and validation. The document states that "Verification and Validation Protocols have been executed to ensure adequate testing of all defined product design requirements and specifications" and "All technological characteristics and performance requirements identified in the Substantial Equivalence Comparison have been tested to ensure success of the design implementation." This would be analogous to "standalone" performance for such a device, but it's not an "algorithm-only" performance in the AI sense.

7. The Type of Ground Truth Used

The "ground truth" for the verification and validation activities described in this document would be:

• Engineering specifications and design requirements: The device's operation is designed to meet predefined technical parameters for beam energy, spot size, dose rate, accuracy, etc.
• Physical principles and measurements: The ability to generate and deliver a proton beam with specific characteristics (e.g., within established safety limits, dose rates, spatial accuracy) is verified against known physical laws and validated measurement techniques.
• Safety and efficacy standards: Compliance with relevant medical device standards and regulations.

There is no mention of pathology, expert consensus on images, or outcomes data being used to establish ground truth for this aspect of the device.

8. The Sample Size for the Training Set

The document does not describe the use of a "training set" in the context of machine learning. The device is a physical system with integrated software, not an AI/ML model that learns from large datasets. Therefore, no information is available regarding a training set size.

9. How the Ground Truth for the Training Set Was Established

As there is no "training set" as understood in AI/ML, this question is not applicable. The "ground truth" for the device's design and operation is established through engineering principles, physical measurements, and regulatory standards, as discussed in point 7.

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