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 FBPIterative

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 ScannerkVpmAsCTDIv (mGy) Brain Toshiba GE Siemens Abdomen Toshiba GE Siemens

CT machine Brain CTDI V (mGy) Image quality rank score Abdomen CTDI V (mGy) Image quality rank score Machine Image quality score average Single slice slice slice 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.

(GE Medical Systems) Detector head Scintillator-based gamma camera

CZT / NaI comparison ELGEMS CZT pixilated small field imager Anger camera (NaI) Test image Thyroid phantom

CdZnTe (CZT) E h e + - X  CdZnTe: Gamma rays create electron/hole pairs. The gamma energy level is proportional to the electrical current. Semiconductor - CZT

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  m 100  m 1mm 1cm 10cm  400 nm 800 nm 1600 nm 10  m 100  m Thermography THz imaging Confocal/ multi-photon microscopy Diffuse optical tomography Optical coherence tomography

Magnetoencephalography

Medical Physics Topics? Treatment of depression: Transcranial magnetic stimulation. Killing of cancer cells: Electric field on biological molecules.