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ExacTrac is a system that is intended to be used to place patients at an accurately defined point within the treatment beam of a medical accelerator for stereotactic radiosurgery or radiotherapy procedures. The ExacTrac system uses optical tracking of infrared markers and x-ray registration to determine and correct the position of the patient. With the additional ExacTrac gating module, the treatment beam is gated in accordance with the patient's breathing level.

ExacTrac 5.5 is an Image Processing System for patient positioning with the ability of a gated treatment. It is based on an imported isocenter from a planning system or on an isocenter imported from a simulator. It allows verification and, if necessary, correction of the patient's position.

The correction of the patient's position is based on a comparison of digital reconstructed radiographs (DRR) calculated from a corresponding CT data set (reference image). Alternatively implanted radioopaque markers may be used for localization by comparing their position in the x-ray with their original position in the reference CT data set. Within the Gating module the 3D position of the implanted markers is compared, for at least one breathing level of the patient, to their expected position based on the CT data With the resultant correction values and target movement information the patient is repositioned and the system generates a signal to gate the linear accelerator depending on the patients breathing.

A scientific study to validate accuracy was performed.

1. A table of acceptance criteria and the reported device performance

2. Sample size used for the test set and the data provenance

The sample size for the test set and the data provenance (e.g., country of origin, retrospective or prospective) are not specified in the provided 510(k) summary.

3. Number of experts used to establish the ground truth for the test set and the qualifications of those experts

The number and qualifications of experts used to establish ground truth for the test set are not specified in the provided 510(k) summary.

4. Adjudication method for the test set

The adjudication method for the test set is not specified in the provided 510(k) summary.

5. If a multi-reader multi-case (MRMC) comparative effectiveness study was done, and the effect size of how much human readers improve with AI vs. without AI assistance

A multi-reader multi-case (MRMC) comparative effectiveness study and any effect size related to human reader improvement with or without AI assistance are not described in the provided 510(k) summary. The ExacTrac 5.5 system is intended for patient positioning and correction, not for diagnostic interpretation by human readers.

6. If a standalone (i.e., algorithm only without human-in-the-loop performance) was done

The provided text states: "ExacTrac 5.5 is an Image Processing System for patient positioning with the ability of a gated treatment... It allows verification and, if necessary, correction of the patient's position." The system operates by comparing images (DRRs or x-rays of markers) to a reference CT data set to determine and correct patient position. This implies a standalone algorithmic function to derive the correction values. However, the exact methodology of a "standalone" performance study as a separate entity is not explicitly detailed as such in the provided text, but the system's core function is an automated process.

7. The type of ground truth used

The ground truth used for localization is based on:

• "a comparison of digital reconstructed radiographs (DRR) calculated from a corresponding CT data set (reference image)."
• "Alternatively implanted radioopaque markers may be used for localization by comparing their position in the x-ray with their original position in the reference CT data set."
• "Within the Gating module the 3D position of the implanted markers is compared, for at least one breathing level of the patient, to their expected position based on the CT data."

This indicates that the ground truth relies on reference CT data sets and the known positions of implanted radioopaque markers as established during planning or simulation.

8. The sample size for the training set

The sample size for the training set is not specified in the provided 510(k) summary. The document describes a validation of the system after development, not a detailed account of the AI/algorithm training process.

9. How the ground truth for the training set was established

The method for establishing ground truth for a training set is not specified in the provided 510(k) summary. The document focuses on the validation of the system's performance for patient positioning against defined reference points.

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