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AVIS-DICOM

documentation on the project for processing DICOM images

Boon Logic

System Architecture

This server is made to process DICOM test images and return major and minor defect information to the user.

Whole Pipeline

Labview SDK

Located on the test bench controller, this interfaces with the AVIS server over the internal network.

Labview SDK



Example image

All Options Labview

AVIS AI Server

On-prem 1U mountable rack to be delivered on site.

Labview SDK

Specifications:

Features:

See the Server Connections Document for more information.

REST API

REST interface for accessing the server and its processed results.

Labview SDK

General  
Status Timestamp of the call to determine if server is active
Version Version numbers for all included software

Included Software:

Test Bench  
Attach
(Required)
Assign identifier
Detach Remove identifier from the list of valid test benches
Status Status in pipeline of individual test bench
OR
List of all test benches’ statuses in their respective pipelines
Parameters  
Define Set values and forego autotuning for any set values
Returned Complete list of parameters used in processing of the image (including auto-set values)
subcell
width (configurable) - number of pixels across for the subimage
shift (set) - number of pixels to shift over between each subimage
preprocess
filter (configurable) - filter to preprocess the whole image. Options are median, gaussian, or none
parameter (configurable) - parameter associated with the filter. If the filter is median, this value corresponds to the window width, if the filter is gaussian, then this corresponds to the sigma value
edge (configurable) - number of pixels to trim around the edge of the image
thresholds
contrast (configurable) - defect contrast threshold for determining whether the candidate is minor or major
variation (set) - the distance measurement to distinguish variation between subimages (Boon value)
distance (set) - distance index between subimages’ clusters (Boon value)
local z value (set) - statistical normality value measuring the variation of pixel values within the subimage (Boon value)
histogram maximum (set) - value for cropping histogram of magnitude values for each subimage
Image  
Send
(Required)
Send DICOM image to AVIS server to be processed
Results  
Returned
(Required)
Summary of defect values resulting from the last image processed
image - identifier associated with the last image processed
major - number of major candidates found
minor - number of minor candidates found
coordinates
major - list of coordinates where each major defect candidate was located on the original image
Summary  
Returned
(Required)
Send DICOM image to AVIS server to be processed

Example summary file

Labview SDK

See the API Documentation for more information.

Image Process

General pipeline happening on the backend when each DICOM image is pushed to the AVIS server.

Labview SDK

Step 1: Crop SF images

Using the image name identifier, the right edge is clipped if the DICOM image name contains the filter identifier “SF”. If the filter is LF, this step is skipped.

Step 2: Filter image

Using the specified filter type in the configuration (gaussian, median, or none), the image is passed through the filter. The filtered image is now the image used in the rest of the processing pipeline.

Step 3: Subdivide image

Using the subcell width from the configuration (in number of pixels), the DICOM image is subdivided into smaller images. The number of pixels between each subimage is the subcell shift value in the configuration.
Labview SDK
Subimages are shown in yellow. This simplified example is for a width of 3 and a shift of 2.

Step 4: Convert subimages to histograms of magnitudes

Each subimage is converted to a histogram of magnitudes using the raw pixel values. Pixel values are binned so that the histogram is has 64 bins of pixels. These histograms are what are used to create the model for each image and find any defects.

Clustering Process

Boon Logic clustering process of the DICOM image.

Labview SDK

The histograms for the image are clustered using Boon Logic’s nano clustering technique. From the raw image, shown on the right, the resulting clusters are assigned frequency values where high values are associated with areas of the image that are different from the rest of the image regions. The image shown on the right is a contour plot of an example DICOM image’s results with areas in white depicting parts of the image that are potential defects.
Labview SDK Labview SDK

Note that areas along the edge of the image are white where the original image has a natural gradient. This will be taken into account and ignored in the classification step if those areas are indeed just gradients.

Classification Process

Process for classifying the candidates as major or minor defects.

Labview SDK

Major candidates - values fall above ALL thresholds

Minor candidates - values fall above SOME thresholds

Factors

Contrast

  1. Fits each candidate subimage to a plane
  2. Find the difference between the min pixel value and the expected plane value (as well as the difference between the max and the plane)
  3. Difference value divided by the expected plane value gives the contrast measurement
  4. Contrast value is compared to the threshold value (defaulted to 0.02)

Distance

  1. Cluster distance from other clusters created throughout the image
  2. 95th percentile of all distance indexes within the image is the threshold
  3. Compare candidate distance index against threshold

Local Z value

  1. Finds the overall mean and standard deviation of the image’s pixel values.
  2. Find the candidates’ z value for the min (and max) local pixel value
  3. Compare z values against the average z value throughout the whole image

Deliverables

* 1U rack-mountable server (see AVIS DICOM Server section)

* Results values

AVIS Enabled Process

Labview SDK