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The Varex Nexus DR™ Digital X-ray Imaging System is a high resolution digital imaging system intended to replace conventional film techniques, or existing digital systems, in multipurpose or dedicated applications specified below. The Nexus DR™ Digital X-ray Imaging System enables an operator to acquire, display, process, export images to portable media, send images over a network for long term storage and distribute hardcopy images with a laser printer. Image processing algorithms enable the operator to bring out diagnostic details difficult to see using conventional imaging techniques. Images can be stored locally for temporary storage. The major system components include an image receptor, computer, monitor and imaging software.

The Varex Nexus DR™ Digital X-ray Imaging System is intended for use in general radiographic examinations and applications (excluding fluoroscopy, angiography, and mammography).

The Varex Nexus DR™ Digital X-ray Imaging System is a high resolution digital imaging system designed for digital X-ray imaging through the use of an X-ray detector. The Nexus DR™ Digital X-ray Imaging System is designed to support general radiographic (excluding fluoroscopy, angiography, and mammography) procedures through a single common imaging platform.

The modified device consists of an X-ray imaging receptor. Varian PaxScan 4336Wv4, computer, monitor, and the digital imaging software.

The Varex Nexus DR™ Digital X-ray Imaging System is a configurable product platform designed to allow Varex to leverage the common components of digital X-ray imaging systems from which the following medical modalities can be served: General Radiography (excluding fluoroscopy, angiography, and mammography). The Nexus DR™ Digital X-ray Imaging System is then configured to function on a computer with modality specific components, functionality and capabilities to complete the specific product package.

Like the predicate device, the modified Nexus DR™ Digital X-ray Imaging System is in a class of devices that all use similar technology to acquire digital radiographic images. These devices convert X-rays into visible light that shines onto a TFT array, which converts the visible light into a digital electronic signal. This process is ultimately used for the same purpose as Radiographic film, to create an X-ray image.

Identical to the predicate device, the modified device is capable of interfacing with the same wireless PaxScan 4336Wv4 flat panel detector in vTrigger Mode.

However, the modified device is also capable of operating in RAD Mode utilizing an external I/O box to interface with compatible X-ray generators, in non-integrated mode. Through the use of a digital flat panel detector, and a non-integrated generator, the Nexus DR™ Digital X-ray Imaging System (with Grid Suppression) is capable of acquiring digital radiographic images, processing and then displaying them in high quality for clinical diagnosis. The Nexus DR™ Digital X-ray Imaging System can then store the images on the local computer, archive them to CD/DVD media, transfer them to Hard Copy format via DICOM printers, or transfer them to PACS reviewing stations in DICOM format.

Anti-scatter grids play an important role for enhancing image quality in radiography by transmitting a majority of primary radiation and selectively rejecting scattered radiation. When anti-scatter grids are utilized by the end user, the modified device includes an additional feature that can detect and suppress the line artifacts caused by these grids.

This FDA 510(k) K171138 submission describes the Varex Nexus DR™ Digital X-ray Imaging System, specifically focusing on the addition of a 'Grid Suppression' feature. The submission aims to demonstrate substantial equivalence to a previously cleared device (K161459).

Here's an analysis of the acceptance criteria and study information provided:

1. Table of Acceptance Criteria and Reported Device Performance:

The document primarily focuses on demonstrating that the new feature (Grid Suppression) does not negatively impact the existing performance characteristics and that the device remains substantially equivalent to its predicate. Therefore, the "acceptance criteria" discussed are largely qualitative and related to maintaining equivalence rather than new quantitative performance metrics for the grid suppression itself.

The acceptance criteria throughout the document for the new Grid Suppression feature and RAD Mode are primarily based on maintaining the existing safety and effectiveness and image quality characteristics of the predicate device, while the new features perform their intended function (e.g., suppressing grid lines, interfacing with generators). The study relies on non-clinical bench testing to demonstrate this.

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

The document states: "Non-clinical Data submitted is consistent with FDA guidance document... Validation was completed in accordance with the Validation Protocols included with this submission. Protocols were designed, executed and documented according to the Design Validation process with predetermined test methods and corresponding acceptance criteria."

• Sample Size: Not explicitly stated for specific tests. The validation likely involved a sufficient number of test cases and images to demonstrate the functionality and non-degradation of image quality due to the new features. Given it's non-clinical, controlled test images/data would have been used.
• Data Provenance: The data is generated from non-clinical bench testing and validation. It is prospective in the sense that the testing was performed specifically for this submission. The country of origin of the data is not specified but is presumed to be from Varex Imaging Corporation's testing facilities.

3. Number of Experts Used to Establish Ground Truth and Qualifications:

• Not Applicable. This submission relies on non-clinical testing and benchmarking against the predicate device's established performance metrics. Clinical images and expert review for ground truth are explicitly stated as not necessary to establish substantial equivalence for the modifications.

4. Adjudication Method for the Test Set:

• Not Applicable. Since clinical experts were not used to establish ground truth for this non-clinical submission, no adjudication method was employed.

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

• No. An MRMC study was not conducted. The document explicitly states: "Clinical images were not necessary to establish substantial equivalence based on the modifications to the device (the PaxScan 4336Wv4 Flat Panel Detector uses identical technology as the predicate device image detector), and bench testing results provide enough evidence that the subject device works as intended."
• Effect Size: Not applicable as no such study was performed.

6. Standalone (Algorithm Only) Performance:

• Yes, implicitly. The grid suppression feature is described as "an intuitive software algorithm to detect and suppress the line artifacts caused by anti-scatter grids." The validation testing, being non-clinical, would have assessed the performance of this algorithm in a standalone manner (i.e., algorithm only without human-in-the-loop performance evaluation) to confirm its effectiveness in suppressing grid lines without introducing new artifacts or degrading image quality. The performance metrics listed (spatial resolution, SNR, MTF, DQE maintain "Same") indicate that the overall system performance, even with the new algorithm, remained consistent with the predicate.

7. Type of Ground Truth Used:

• Benchmarking/Predicate Device Equivalence (established performance metrics). For the core imaging performance metrics (Spatial Resolution, SNR, MTF, DQE, etc.), the ground truth is the established performance of the predicate device, which the modified device is shown to match. For the new grid suppression feature, the "ground truth" would be the successful removal of grid artifacts from test images while preserving diagnostic quality, as determined by technical validation protocols.

8. Sample Size for the Training Set:

• Not explicitly stated. The document refers to "an intuitive software algorithm" for grid suppression. For such an algorithm, a training set would likely be used during its development. However, the specific size of this training set is not disclosed in the provided FDA summary.

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

• Not explicitly stated in the provided document. If machine learning was involved in developing the "intuitive software algorithm" for grid suppression, the training set ground truth would typically be established by presenting the algorithm with a dataset of images, some with grid artifacts and some without, and potentially images where the presence/absence of grid lines and their characteristics have been manually labeled or synthetically generated. This is standard algorithm development practice, but the specifics are not detailed in this 510(k) summary.

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