Reconstruction artifacts connected to drifts in components and limited mechanical accuracies of micro-CT and nano-CT systems A. Sasov

Slow thermal drift with long decay Random object movement during rotation

Slow thermal drift with long decay Random object movement during rotation

Slow thermal drift with long decay: How to measure? R D Micro- focus or submicro- focus x-ray source Object manipulator: rotation, translation X-ray detector Sample Electron beam Metal target Electron-induced X-ray source

Slow thermal drift with long decay: How to measure?

Slow thermal drift with long decay: How to measure?

Slow thermal drift with long decay Type of X-ray source? Sealed microfocus Grounded cathode Open (pumped) micro/nanofocus Grounded anode Sealed microfocus Grounded anode POSITION INSTABILITY: Up to +/ of spot size Up to +/- 5 of spot sizeTypically under 0.5 of spot size

Slow thermal drift with long decay Object: 10µm glass fibers in epoxy; 800nm isotropic voxel size Ok

Slow thermal drift with long decay How to avoid ?

Slow thermal drift with long decay Object: Composite material with plastic spheres; 600nm isotropic voxel size

Slow thermal drift with long decay before after

Slow thermal drift with long decay Random object movement during rotation

How to measure?

Random object movement during rotation How to measure?

Random object movement during rotation Where it’s coming from?

Random object movement during rotation Where it’s coming from?

Random object movement during rotation Where it’s coming from? Micos UPR160 air bearing stage: Max. radial runout is 180nm (+/- 90nm) LAB AirBearing: Max. radial runout is 39nm …with active compensation - <5nm

Random object movement during rotation What to do if air-bearings cannot be used?

Random object movement during rotation How results look like? Object: filamentous cyano bacterium, 100 nm pixel size, 50nm X-ray spot size Scanning Set-Up: Stepping motor in vacuum (microstepping mode)

Random object movement during rotation What can be done? 1.Standard FBP reconstruction =unsharp/proper position 2. Forward projection =unsharp simulated projections 3. Centering original projections =sharp proper position 4. Repeat FBP with centered prj. =sharp reconstruction

Random object movement during rotation Object: filamentous cyano bacterium, 100 nm pixel size, 50nm source spot size 350 nm cell wall

Slow thermal drift with long decay Random object movement during rotation Nrecon (CPU, GPU-accelerated, 32 / 64bit OS)