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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

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

  • Computer aided diagnosis

  • Radiation detectors


Filtered Back-Projection


Butterworth Filter and Cutoff Frequency


Iterative Reconstruction


Rescaled Block Iterative Reconstruction Algorithm


Attenuation Compensation


Scatter Compensation


Resolution Compensation


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


Reconstructed images

FBP

Iterative


Human and Numerical Observer Image Quality Studies

  • Human observer study using receiver operating characteristics

  • Numerical observer employing an ideal observer model.


Receiver Operating Characteristics


Numerical Observers


Types of Channels


Numerical Observer Results: RBI


Human Observer Results


Scatter and Cross-talk Correction in Dual Radionuclide Imaging


The Neural Network


Before Correction

After Correction


Image Registration


Statistical Parametric Mapping


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.


CT Scan Parameters and Dose Index

Brain

Abdomen


CT Dose Index and image quality scores summary


Single Slice CT Images


16 Slice CT Images


64 Slice CT Images


Computer Assisted Diagnosis

  • Provide second opinion to radiologists.

  • FDA approved systems include breast and lung cancer detections.

  • Image processing

  • Image data base

  • Artificial intelligence.


PET/SPECT Simulation Using GEANT


Radiation Detectors

  • Room temperature Semiconductor Detectors: Materials and mechanisms

  • Magnetic resonance coils designs.


Scintillator-based gamma camera

Detector head

(GE Medical Systems)


CZT / NaI comparison

ELGEMS CZT pixilated

small field imager

Anger camera (NaI)

Test image

Thyroid phantom


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

-


The GaAs detectors


Hybrid Modalities – PET/CT


Hybrid Imaging Systems


New Imaging Systems

  • New detector technology.

  • Optical imaging: visible, ultraviolet, inferred.

  • Molecular imaging: PET, fMRI, Optical

  • Hybrid imaging systems.

  • T Herts imaging.


Optical Imaging


Teraherts Imaging


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


Magnetoencephalography


Medical Physics Topics?

  • Treatment of depression: Transcranial magnetic stimulation.

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


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