UFC - Ultra Fast Ceramic
UFC - Technology
What is UFC?
Functional ceramics are all-important for high image quality. UFC or Ultra Fast Ceramic is a scintillator material which quickly and efficiently transforms radiation from the X-ray tube into light signals. These signals in the visible spectrum are in turn picked up by photodiodes, transforming them into electric signals, which are computed to become visual 2D or 3D images.
Conventionally, other single crystalline substances are used in X-ray detectors such as cadmium tungstate (CdWO4), or cesium iodide (CsI). In our Ultra Fast Ceramic we use a crystal lattice of rare earth compounds gadolinium oxysulfide (GOS). UFC has a large X-ray absorption coefficient and due to its fast decay, reacts very rapidly to changes in X-ray intensity. These properties make it the ideal scintillator not only for time-critical medical imaging, but also for other fields and dynamic applications.
What's the difference?
UFC is superior to conventional detector materials in many ways - from light output, to decay time and drift. This outstanding product has proven itself in the challenging field of medical imaging.
Now, we see our Ultra Fast Ceramic being used in more and more industries - in order to deliver ever-improving levels of accuracy and efficiency elsewhere.
How fast is UFC?
Due to its fast decay behaviour and extremely short afterglow, Siemens UFC scintillator material is optimized for use with the fastest CT scanners, with rotational speeds well under 0.4 seconds.
In high-speed cardiac imaging, UFC requires no compromises in the number of image projections or any other correction algorithms which would impair image quality. UFC's primary advantage is its speed in combination with other unique properties – from minuscule drift, to short afterglow and excellent mechanical behaviour and handling.
Since scanners are becoming increasingly faster, this advantage of fast decay times continues to gain in importance in medical imaging as in other dynamic applications.
1.1 Physical Properties
1.1.1 X-ray and γ - Properties
X-ray Attenuation Coefficient, based on: μ = 1/d ln (I/Io)
Data based on experiments using a CT X-ray tube and filters 3.0 mm Al + 0.6 mm Titan; tungsten anode; attenuation coefficient of a 1.4 mm UFC detector.
Data based on calculations for mono energetic radiation
a) Temporary Radiation Damage (Drift)
Signal change (typical) = 0.4% at 120 kV/250mA; t=60s
1005 mm (focus detector distance). Filter 10 mm Al equivalent at 80kV.
b) Permanent Radiation Damage
No permanent damage observed during 10 years of operation and in measurement
with 30 kGray.
Uniformity of Spectral Linearity
Typical uniformity = 0.025% over a length of 10 mm using the dual energy method:
120 kV/ 194 mAs/ 1005 mm (focus detector) and
140 kV/ 126 mAs/ 1005 mm (focus detector distance)
1.2 Optical Properties
1.2.1 Optical Constants
Refractive index n = 2.2
1.2.2 Point Spread Function (subject to future changes)
FWHM 1) = full width at half maximum
FWTM 2) = full width at tenth maximum
Simulation for a flat wafer with no boundaries. No reflector was used.
X-ray tube voltage 140 kV, filter 2 mm Al/1.26 mm Ti.
1.2.3 Light Output Uniformity
Light output change < 1% over a length of 30 mm.
Uniform X-ray exposure uncoated ceramic.
Use of a reflector may affect this value.
1.3.1 Emission Wavelength Spectrum
1.3.2 Short Time Afterglow
• time 0 for tuning off source is known within ~0.2 ms
• decay to < 10-3 occurs within 0.2 ms
• a trend to teach 10-4 is seen at 2.5 - 4 ms
1.3.3 Long - Term Afterglow with Pulsed X-ray Source
• data interval is 1 ms
• decay to 10-4 is seen after 1 ms and decay to < 10-5 within 10 ms
• digitization noise becomes relevant below 10-5
• a trend towards 10-6 is seen between 10 ms and 100ms
1.4 Bulk Properties
7.29 – 7.33 g/cm3 (99.95% of theoretical density)
1.4.2 Vickers Hardness (subject to future changes)
HV = 910 ± 50 (Force: 1.5 N, duration: 20 s, rate: 20 p/s)
1.4.3 Thermal Properties
Specific Heat Capacity
Cp ≈ 0.318 ± 0.016 Jg-1K-1 at 305 K
Thermal Expansion Coefficient (volume)
10.0 *10-6 ± 0.3 * 10-6 K-1 between 423 K – 873 K
Thermal change of light output
The average change of light output is 6 GU/K (Temperature = from 301K to 310K)
9.6 ± 1.4 Wm-1K-1 at 293 K
1.4.4 Electrical Properties
σd< 1 * 10-13 Ω -1 m-1
Photoconductivity (at typical light intensities) can be neglected.
2.1 General Resistance
UFC is resistant to all kinds of oil, solvent and water. It dissolves in concentrated mineral acids.
2.2 Weather Resistance
No change in characteristic properties after 3 months at an atmosphere of 100% O2, a relative humidity of 100% and a temperature of 70 °C (158°F).
2.3 Machining Properties
UFC may be precision machined and processed using all kinds of abrasive methods as sawing, lapping, polishing as well as etching.
2.4 Handling Tools
The UFC needs to be handled according to the rules of good craftsmanship. It may not be handled using smooth metals (up to non-hardened steel). Metallic contaminations are difficult to remove.
2.5 Environmental Safety
Due to its non poisonous nature UFC has no impact on the environment unlike other solid state scintillation materials.
Rectangular wafers or crude blocks.
Flatness: < 10 μm
3.3 Surface Roughness
Rz = 2.5 μm – 8 μm