7 - x-rays - 30 min

X-Rays

Nov. 1895 – Wilhelm Röntgen Announces X-ray discovery in Germany

Jan. 13, 1896 – Images needle in patient’s hand– X-ray used presurgically

1901 – Receives first Nobel Prize in Physics

History

Definition

• Electromagnetic radiation (1017 to 1021 Hz).• High energy

• When a fast-moving electron swings around a heavy nucleus, it accelerates rapidly

• Electron emits much of its energy as X-ray photon

Bremsstrahlung

• When a colliding electron excites an atom to high-energy state, that atom can then radiate an x-ray photon

Characteristic

Definition

electron beam generator

tungsten target metal

resultant X-ray beam

silver halide film

• The electrons come from a tungsten lamp which current can be from 25 to 1.200 mA

• Electrons accelerated with voltages from 25 kV to 150 kV

• Let electrons hit heavy atoms

X-rays

X-ray Tube

http://www.spineuniverse.com/videos/x-rays/

X-ray Tube

• Some x-rays emitted via bremsstrahlung and some as characteristic X rays

• X-ray tube filters awaylowest energy photons (Bremsstrahlung)

X-ray Production

X-ray Tube

Accelerate electrons towards anode results in:

Typically Tungsten Target • High melting point• High atomic number• 3000 rpm to 10000 rpm

1. Collision events produce heat (95 % of energy)2. Photoelectric effect

3. X-ray

X-ray Tube

X-ray Tube

X-ray Tube

Operator can change:• Tube voltage• Filament current• Exposure time(millisecond to several minutes)

An increase in voltage leads to decreased image contrast and increased SNR.

Collimator

Aluminium grid

Patient

X -ray source

Target film

Grid

Aluminium grid

Patient

X -ray source

Target film

Grid

Grid

Grid

Grid

Block Diagram

High voltage generator X-ray tube

Collimator and filters

Automatic exposurecontrol

Control panel

Storage system

File processingsystem

Detection system

CAD = COMPUTER-ASSISTED DIAGNOSIS

Block Diagram

X-ray Generator

Control PanelPower Supply

Autotransformer

kV Selection

Timer

mA Selection

X-ray Tube

High Voltage Circuit

Filament Circuit

Timer

Block Diagram

Block DiagramSiemens Polimobil III

10 kHz

Power Supply

100 W to more than 100 kW

• Dedicated distribution transformers• Appropriate size conductors• Higher line voltage (reduce conductor size)• Low-power operates in 220 V• Higher power equipment 440/480 V

Portable X-ray

Automatic X-ray Film Processor

Digital X-ray

DICOMDigital Imaging and Communications in Medicine

Format definition and a network communications protocols

Safety

• Shielded walls

• Charging in capacitors (360 VDC)

Maintenance“ALWAYS turn off high voltage circuit”

• Mechanical Arms

Broken chain

Maintenance“ALWAYS turn off high voltage circuit”

• Power supply – fuse burnt by spikes• Inversor circuit• Tube heating

– Loose alignment of rotor axe – friction– Burn filament– Air bubbles

Calibration Equipment

Angiography - Contrast Injection

Mammography

Normal tissue

Tissue with cancer cells

Mammography

History

In 1930 in the United States, Stafford Warren reported the diagnostic value of performing mammography on live patients.

Wiley - Encyclopedia of Biomedical Engineering - 6 Vol. Set

Mammography

History

In 1930 in the United States, Stafford Warren reported the diagnostic value of performing mammography on live patients.

Wiley - Encyclopedia of Biomedical Engineering - 6 Vol. Set

(<35 kVp)

2 Positions:

horizontal and 45 degrees

Mammography

X ray source

X-ray beam

Screen-film

cassette

Mammography

Mammography

CAD Image

Fluoroscopy

Fluoroscopy

CRC Press - Biomedical Photonics Handbook

X–rays Dental

Radiotherapy

RadiotherapyELECTRON-BEAM