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Current Topics in Medical Physics Research. Xiaoming Zheng, PhD. School of Dentistry and Health Science Chengdu, China, 2009. Current Research Interests . Image reconstruction algorithms Scatter and resolution corrections Image quality assessment Clinical image analysis

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Current topics in medical physics research l.jpg

Current Topics in Medical Physics Research

Xiaoming Zheng, PhD.

School of Dentistry and Health Science

Chengdu, China, 2009


Current research interests l.jpg

Current Research Interests

  • Image reconstruction algorithms

  • Scatter and resolution corrections

  • Image quality assessment

  • Clinical image analysis

  • Computer aided diagnosis

  • Radiation detectors


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Filtered Back-Projection


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Butterworth Filter and Cutoff Frequency


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Iterative Reconstruction


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Rescaled Block Iterative Reconstruction Algorithm


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Attenuation Compensation


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Scatter Compensation


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Resolution Compensation


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Images Reconstructions

  • Iterative Reconstruction: Rescaled Block Iterative Algorithm including attenuation, scatter, and distance resolution compensation. Parameters tested: iteration 1,3,5,7,10 and post Gaussian filter FWHM 0,1,2,3,4 pixels

  • Filtered Back-Projection: Parameters tested: Butterworth filter cut-off frequencies: 0.10, 0.15, 0.20, 0.25 and 0.30 pixel-1


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Reconstructed images

FBP

Iterative


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Human and Numerical Observer Image Quality Studies

  • Human observer study using receiver operating characteristics

  • Numerical observer employing an ideal observer model.


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Receiver Operating Characteristics


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Numerical Observers


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Types of Channels


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Numerical Observer Results: RBI


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Human Observer Results


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Scatter and Cross-talk Correction in Dual Radionuclide Imaging


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The Neural Network


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Before Correction

After Correction


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Image Registration


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Statistical Parametric Mapping


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Radiation Dose Optimization in CT

  • Biological effect of ionizing radiation

  • Cancer rate vs radiation dose

  • Radiation dose reduction: image quality vs radiation dose

  • Technical parameters: kVp, mAs, etc.


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CT Scan Parameters and Dose Index

Brain

Abdomen


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CT Dose Index and image quality scores summary


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Single Slice CT Images


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16 Slice CT Images


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64 Slice CT Images


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Computer Assisted Diagnosis

  • Provide second opinion to radiologists.

  • FDA approved systems include breast and lung cancer detections.

  • Image processing

  • Image data base

  • Artificial intelligence.


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PET/SPECT Simulation Using GEANT


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Radiation Detectors

  • Room temperature Semiconductor Detectors: Materials and mechanisms

  • Magnetic resonance coils designs.


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Scintillator-based gamma camera

Detector head

(GE Medical Systems)


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CZT / NaI comparison

ELGEMS CZT pixilated

small field imager

Anger camera (NaI)

Test image

Thyroid phantom


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Semiconductor - CZT

g

CdZnTe: Gamma rays create electron/hole pairs. The gamma energy level is proportional to the electrical current.

X

CdZnTe (CZT)

E

h

+

e

-


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The GaAs detectors


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Hybrid Modalities – PET/CT


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Hybrid Imaging Systems


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New Imaging Systems

  • New detector technology.

  • Optical imaging: visible, ultraviolet, inferred.

  • Molecular imaging: PET, fMRI, Optical

  • Hybrid imaging systems.

  • T Herts imaging.


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Optical Imaging


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Teraherts Imaging


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Thickness of tissue probed

30 mm 100mm 1mm 1cm 10cm

l

400 nm

800 nm

1600 nm

10 mm

100 mm

Confocal/ multi-photon microscopy

Diffuse optical tomography

Optical coherence tomography

Thermography

THz imaging


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Magnetoencephalography


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Medical Physics Topics?

  • Treatment of depression: Transcranial magnetic stimulation.

  • Killing of cancer cells: Electric field on biological molecules.


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