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The S-250 is intended to deliver proton radiation treatment to patients with localized tumors or any other conditions susceptible to treatment by radiation.

The S-250 is a medical device indicated for the delivery of radiation for the treatment of patients with localized tumors or other conditions susceptible to treatment by radiation.

The S-250 is a low cost, one-room integrated device designed to administer proton radiation treatments to patients through delivery of a predetermined radiation dose to a pre-determined three dimensional treatment target volume in a manner that protects the patient, and hospital staff, from unnecessary exposure to radiation and other hazards.

The S-250 design requires a very compact proton accelerator which is supported on a rotating gantry such that a proton treatment beam can be directed toward the rotational center of the gantry over a range of about 180 degrees (straight up to straight down). The gantry holds the cyclotron at a large enough distance from the rotating arm(s) that a full treatment room floor can be extended around the treatment center and a treatment couch can support a patient over a large rotational (couch) range at isocenter.

The system will be a completely integrated system incorporating all functionality necessary to efficiently treat patients with proton beams. As such it incorporates near real time radiographic based patient alignment and coupled patient support devices (couch) with broad flexibility for supporting the patient relative to the treatment beam. The couch is capable of six-degree-of-freedom adjustment and be able to rotate about a vertical axis in a range of about 270 degrees, so as to provide full coverage of beam directions typically used in radiation therapy

To keep high precision of alignment of the field specific device (range compensator and apertures) to the patient, these devices will be supported on a separate gantry, close to the treatment center and not physically connected to the large gantry supporting the cyclotron. This will lighten the aiming requirements for the large gantry.

The S-250 is a proton beam irradiation 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 as provided by a separately marketed Treatment Planning System (TPS) not distributed by Mevion Medical Systems. The S-250™ is comprised of two main components. One is a beam delivery system whose primary responsibility is to ensure that the prescription parameters are properly delivered. The other is the beam generating system whose function is to generate the proton beam and direct it to the beam delivery system.

The provided document, K120676 for the Mevion S-250 Proton Radiation Beam Therapy System, does not include a detailed study proving the device meets specific acceptance criteria in the manner typically seen for diagnostic AI/ML devices. Instead, it is a 510(k) Premarket Notification Summary for a medical device that relies on substantial equivalence to predicate devices.

Here's an breakdown based on the information available:

1. Table of Acceptance Criteria and Reported Device Performance

This information is not provided in the document in the format of a table with specific performance metrics and acceptance criteria. The document states:
"Performance data demonstrates that the S-250 is as safe and effective as the predicate devices listed herein."

The acceptance criteria here are implicitly tied to the performance deemed acceptable for the predicate devices, implying that the S-250 meets those established safety and effectiveness standards through its design and testing. The document highlights that "The S-250 does not require new technical innovations beyond existing technologies" and lists various components that use conventional or straightforward design extensions.

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

This information is not applicable and not provided because a clinical study with a test set of patient data, as would be common for an AI/ML diagnostic device, was not conducted to demonstrate efficacy. The device is a radiation therapy system, and its efficacy is based on the established clinical utility of proton beam radiation therapy generally, and its substantial equivalence to other legally marketed proton therapy systems.

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

This information is not applicable and not provided. Ground truth in the context of an AI/ML diagnostic study is not relevant here as there was no such study performed.

4. Adjudication Method for the Test Set

This information is not applicable and not provided.

5. Multi Reader Multi Case (MRMC) Comparative Effectiveness Study

A multi-reader multi-case (MRMC) comparative effectiveness study was not performed as described in the document. The filing explicitly states: "The S-250 Proton Beam Radiation Therapy System offers no additional or changed diagnostic or therapeutic claims beyond the stated predicate devices. Therefore, demonstration of clinical efficacy is not a required element of this premarket notification." The document mentions a "Clinical Data Evaluation Report that summarizes peer-reviewed literature related to the clinical efficacy and safety proton beam radiation therapy systems," but this is a literature review, not a new comparative effectiveness study of the S-250.

6. Standalone Performance (i.e., algorithm only without human-in-the-loop performance)

This information is not applicable as the S-250 is a physical medical device (a proton radiation beam therapy system), not an algorithm or AI/ML software. Its intended use involves trained healthcare professionals.

7. Type of Ground Truth Used

Not Applicable for a direct device assessment as described in an AI/ML context. The "ground truth" for the S-250's deemed safety and effectiveness is its adherence to engineering and design standards, demonstration of proper function, and its substantial equivalence to established proton therapy systems that already have clinical efficacy demonstrated through years of use and literature.

8. Sample Size for the Training Set

Not Applicable. The S-250 is a hardware system, not an AI/ML model that is 'trained' on data in the conventional sense.

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

Not Applicable.

Summary of Device Acceptance and Study:

The acceptance of the Mevion S-250 system by the FDA, as detailed in this 510(k) summary, is primarily based on the Substantial Equivalence pathway.

The "study" that proves the device meets acceptance criteria is not a clinical trial with patient data or an AI/ML validation study. Instead, it relies on:

• Technological Comparison: The document meticulously compares the S-250's various components (e.g., high field magnet, radiofrequency system, beam extraction, gantry, dosimetry) to existing technologies and designs, asserting that it "does not require new technical innovations beyond existing technologies."
• Predicate Device Comparison: The S-250 is compared to several legally marketed predicate proton therapy systems (Harvard Cyclotron Lab, IBA Proteus 235, LLUMC, Indiana University Cyclotron Facility, Hitachi PROBEAT, Varian pt2). The core argument for substantial equivalence is that the S-250 and these predicates "have substantially the same Intended Use and principles of operation, and are substantially equivalent in terms of performance and technological characteristics."
• Performance Data (Implicit): The conclusion "Performance data demonstrates that the S-250 is as safe and effective as the predicate devices" implies that Mevion conducted internal verification and validation testing to ensure the S-250 performs to engineering specifications consistent with the safety and operational principles of the predicate devices. The document references "Verification and Validation Testing" and "Design Reviews" to ensure fulfillment of design requirements and product safety/efficacy.
• Risk Analysis: A "System Hazard Analysis" was performed to identify and mitigate potential health and safety hazards.
• Quality System Compliance: Mevion's quality system is stated to be in compliance with FDA Quality System Regulations, ISO 9001, ISO 13485, ISO 62304, ISO 14971, and the MDD.

The FDA's clearance (K120676) signifies that the agency agreed with Mevion's assessment that the S-250 is "substantially equivalent" to existing devices and thus safe and effective for its intended use, without requiring new clinical efficacy data for the device itself.

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