Visual Optimality And Stability Analysis Of 3DCT Scan Positions

Artem Amirkhanov 1,2

Michael Reiter 2

Christoph Heinzl 2

M. Eduard Gröller 1

1 Institute of Computer Graphicsand Algorithms

Vienna University of Technology

2 Upper Austrian University of Applied Sciences

Wels Campus, Austria

Artem Amirkhanov 2

Scanning Geometry

X-ray source

Specimen

Detector

Rotary plate

Placement is crucial forMeasurements accuracy

Iso-surface quality

Requires knowledge, intuitive

Good placement is hard to findFor a complex specimen

For measurement features

Doing several scans is expensive

Artem Amirkhanov 3

Specimen Placement

CAD model is availableQuality control – from manufacturer

Reverse engineering – preliminary scan

Use a CAD model to estimate a good placement

Visual analysis tool is required forSimulation-based preview

Optimal placement estimation

Tool

Artem Amirkhanov 4

Motivation

Optimal Placement

Artem Amirkhanov 5

Why Placement is Important?

Beam-hardening artifactsCupping artifacts

Streaks

Bad planar faces artifactsBlurring

Artem Amirkhanov 6

Good/Bad Placement Example

Bad:

Good:

Shortest penetration lengths Method: ray casting

Smallest bad planar faces areaMethod: Radon-space analysis

Stable within a certain range of reliabilityMethod: stability widget

Artem Amirkhanov 7

Criteria and Methods

Artem Amirkhanov 8

Workflow

• Ray casting• Radon-space analysis

Simulation

• Stability analysis• Data exploration and analysis

Visual analysis

Optimal placementOptimal placement

CAD modelCAD model

ParameterspacesParameterspaces

Artem Amirkhanov 9

Simulation

Set of candidate placements

Placement is defined by the orientation

Orientation is defined by two Euler angles α and β

α

β

Artem Amirkhanov 10

Ray Casting Simulation

Reflects the scanning setup

Set of projections for every placement

ParametersMaximum penetration length

Average penetration length

Artem Amirkhanov 11

Radon-Space Analysis

Supporting planes → points in Radon space

Finding bad points in Radon space

ParameterBad faces area percentage

Artem Amirkhanov 12

Parameters Representation

Best Worst

Parameter value:

Artem Amirkhanov 13

Stability Widget

Better Same Worse

Parameter value:

Penetration-length histogramsVisualizing ray subsets .

Color coding bad faces .

Artem Amirkhanov 14

Data Visualization and Exploration

Artem Amirkhanov 15

Evaluation Using Dimensional Measurements

Two test-part specimens

Measurement featuresRadius

Distance

CALYPSO used to estimate measurement quality

Complex real world specimen

Best and worst placements

Variance comparison of the iso-surfaces with the CAD model

Artem Amirkhanov 16

Evaluation Using Variance Comparison

Artem Amirkhanov 17

Evaluation

Bad Placement Good Placement

Position deviation spectrum in [mm] Position deviation spectrum in [mm]

0 -1 -22 1 0 -1 -22 1

Artem Amirkhanov 18

Limitations and Future Work

Orientation onlyDetect orientation and position in sequence

Still requires user interactionCombining parameters

Artem Amirkhanov 19

Conclusions

VS

Contact: artem.ogre@gmail.com