Transcript Principle of the X-ray tube

Medical Imaging:
the Glass Patient
Prof.dr.ir. Bart M. ter Haar Romeny
Technische Universiteit Eindhoven
Dept. of Biomedical Engineering
Image Acquisition Techniques

Classical X-Ray

Computed Tomography

Nuclear Medicine

Ultrasound

Magnetic Resonance Imaging
Prof. Röntgen presenting
his invention at Würzburg,
23 January 1896
28 December 1895
The first X-ray ever:
the hand of Röntgen’s wife,
end 1895.
One of the first
medical examples:
a shot of hail
in a hand, 1896
Principle of the X-ray tube:
High Voltage
supply
vacuum
Filament
connection
-
cathode
Tungsten anode
+
Anode
connection
+ kV
X-rays output
The kinetic energy of the electrons is released by the collision
at the anode. The tube is vacuum.
Classical X-ray images
Image
intensifier
High voltage
generator
X-ray
tube
Fluoroscopy with the image intensifier during angioplasty:
Real-time visualization of catheters and vessels.
DSA = Digital Subtraction Angiography
= Röntgen X-ray with contrast in vessels
Dotter procedure:
Blow up balloon in
obstructed vessel
CT = Computed Tomography =
Röntgen X-ray slices  3D
Tomoscan AV
Greek  = to cut, to slice
EasyVision
CT: solve for 512x512 pixels by 512x512 equations
Result: a slice
Examples CT
3D visualization
Simulation of the physics
of light reflection
(ray casting/tracing)
“2.5D” image
Nuclear Medicine
Principle:
 Instable radioactive isotopes are
made, and build in a pharmacon
 Patient gets contrast medium
injected, which specifically stores
in tissue
 Signal position is measured with a
gamma-camera
Ionizing radiation: GAMMA
GAMMA photon(s)
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
When the nucleus gets too large, the “strong force” is not strong
enough to compensate the repulsive force of the protons
Alpha radiation: He nuclei
(come only microns far in tissue)
Beta radiation: electrons
(come only cm far in tissue)
Gamma radiation: high energy photons (easily go through tissue)
Nuclear Imaging
Camera
3-rotating-head SPECT scanner
SPECT =
Single
Photon
Emission
Computed
Tomography
PET = Positron Emission Tomography
Positron = anti-electron
When it meets an electron → annihilation (explosion)
Two photons go in opposite direction, ring coincidence detector
No task
During task
Molecular Imaging
Highly specific tracer biomolecules
Nano-vesicles:
- antibody bindings
- 90.000 Gadolinium atoms
- container for pharmaca
- break by US shockwave
- less side effects
- chemotherapy on target
Ultrasound
Kretz Medicor 530D
Doppler
transducer
skin
F0
V
F1
vessel
(red) bloodcells
Fd = F0 - F1 = 2 x V x cos
c
Fd = Doppler (‘difference’) frequency
3D ultrasound
Magnetic Resonance Imaging (MRI)
Y
Z (B0 )
X
Receiver Coil
1000 x 1000 pixels =
1 million measurements
Philips Medical Systems
Superconducting Magnet
MR Angiography
• Excitation only of a thin slice
• Non excited blood flows in the slice
• Readout of little ‘zero-signal’ areas
• For all slices → angiogram
Why so many imaging modalities?

Choice modality: Tissues have different
properties for different physical
interactions

Contrast: Tissue types differ in one or
more of these properties

CT
Anatomical imaging versus functional
imaging
MR
A new 3D technique:
Virtual endoscopy
Anna Vilanova, Vienna TU / TUE - BMT
Univ. of Dusseldorf
Philips Medical Systems
New Eyes are assisting the Radiologist
The overwhelming amount of data calls for
condensed presentation and analysis
Groeller - TU Vienna
Philips Medical Systems
Vital Images
Image Guided Surgery
Physics everywhere
• Image Acquisition
• Pattern recognition
• Computer aided
diagnosis
• Biomedical research
• New researchers
• Strong benefit for
the patient
Bev Doolittle: The forest has eyes