topics in medical physics xiaoming zheng, phd. school of dentistry and health sciences december...
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Topics in Medical Physics
Xiaoming Zheng, PhD.School of Dentistry and Health
SciencesDecember 2009, Chengdu.
Medical Physics at CSU
• Major medical imaging modalities• Physics in nuclear medicine• Magnetic resonance imaging• Physics in computed tomography• Ultrasound physics• Health physics.
Major Imaging Modalities
Typical CT Images
Positron Emission Tomography
On Site Cyclotron
Whole Body PET Images
Magnetic Resonance Imaging
MRI Radio Frequency Coils
MRI Pulse Sequence
MRI Tissue Contrast Images
Ultrasound Imaging
Ultrasound Image
Medical Physics Research Topics
• 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
f fca
f
a HH
d Snk
nk rn
r
nk
r mnm
mnm S
m m
mr
1 1'
Hf k
c
H
Ha crn
mnm S
mnm
r rnr
; m ax
Attenuation Compensation
Scatter Compensation
S WCW
CW
' .
5 2
1
1
3
3
Resolution Compensation
PET simulation using GEANT
Problems in Dual Radionuclide Imaging: Scatter and Cross-talk
The Neural Network
Receiver Operating Characteristics
Numerical Observers
Image Registration
Compositeusing
intensity-based
registration
Compositeusingpoint-based
registration
Brain Activation 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,
Computer Assisted Diagnosis
• Provide second opinion to radiologists.
• FDA approved systems include breast and lung cancer detections.
• Image processing
• Image data base
• Artificial intelligence.
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 pixilatedsmall field imager
Anger camera (NaI)
Test image Thyroid phantom
CdZnTe (CZT)Eh
e+
-
X CdZnTe: Gamma rays
create electron/hole pairs. The gamma energy level is proportional to the electrical current.
Semiconductor - CZT
The GaAs The GaAs detectorsdetectors
The detection systemThe detection system
Detctor characteristicsSi or GaAspixel: 170 x 170 m2
64 x 64 pixels
area 1.18 cm2
Photon Counting Chip ( PCC)CERN EP Microelectronics Group
MEDI PI X Collaboration:CERN, Universita’ ed I NFN Pisa,
Napoli e CagliariUniversita’ di Glasgow e Friburgo
charcteristics:SACMOS 1 mm technologypixel: 170 x 170 m2
64 x 64 channelsarea 1.7 cm2
threshold adjust 3-bit15-bit counter
detector
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 100m 1mm 1cm 10cm
400 nm
800 nm
1600 nm
10 m
100 m
Thermography
THz imaging
Confocal/ multi-photon microscopy Diffuse optical
tomographyOptical coherence tomography
Magnetoencephalography
Medical Physics Topics?
• Treatment of depression: Transcranial magnetic stimulation.
• Killing of cancer cells: Electric field on biological molecules.