Presentation on theme: "Radiation and Medical Physics Academic Staff David Bradley,Tony Clough, Simon Doran, Geoff Grime,Paul Jenneson, Paul Sellin,Nicholas Spyrou External Funding."— Presentation transcript:
Radiation and Medical Physics Academic Staff David Bradley,Tony Clough, Simon Doran, Geoff Grime,Paul Jenneson, Paul Sellin,Nicholas Spyrou External Funding 2001-6 ~ £4m from EPSRC, PPARC, SRIF and Industry
The research of the group covers many areas, from radiation detector development to NMR in medicine. Topics to be covered today: Muon Radiography 3- Positron tomography Ion Beam Analysis of Materials
MUON RADIOGRAPHY OF LARGE INDUSTRIAL STRUCTURES Walter Gilboy, Paul Jenneson - Surrey University Stefaan Simons - University of London Steven Stanley, Dominic Rhodes – British Nuclear Fuels
COSMIC RADIATION “It falleth as the gentle rain from heaven” (Apologies to Shakespeare) Sea level muon intensity 10,000 m -2 min -1 It’s free, universally available and VERY GREEN!
Monitoring Blast Furnace liner thickness Blast Furnace A very large steel containing vessel lined internally with up to 2 metres of carbon heat insulation below 1 metre liquid iron The Problem The liner gradually wears away and when it reduces below 50 cm the danger of molten iron breakthrough through the base increases. A possible monitoring solution When negative muons are reduced to rest in matter nuclear absorption of negative muons can occur. The rate is approximately proportional to Z 4 so that absorption in iron (Z=26) is much more likely than absorption in carbon (Z=6). The resulting nuclear excitation gives rise to neutron emission and the greater yield from the higher Z material can be used to distinguish the two materials. The carbon acts as a neutron moderator and thermalised neutrons diffusing out of the furnace can be detected relatively easily. The potential of this approach has been investigated with a simple experimental set-up and the results compared to Monte Carlo predictions.
Cadmium sheet Wooden pallet Incident Cosmic ray Muons 5-10 cm layer of lead Carbon Block He-3 Tube Muon induced neutron experimental layout
Relative Count Rate µs mainly stopping in C µs mainly stopping in Pb C moderator too thin
THREE-GAMMA IMAGING IN POSITRON EMISSION TOMOGRAPHY N.M. Spyrou and K. Kacperski Centre for Nuclear and Radiation Physics University of Surrey, U.K.
Conventional PET 511 keV Mainly BGO (Bismuth Germanate) scintillation detectors used: High stopping power gives: good efficiency good spatial resolution Good timing Poor energy resolution (12% FWHM @ 511keV at best) Can we get more out of PET ? Is there more information in the annihilation radiation that could possibly be extracted ? Yes!
Physics of positron annihilation Annihilation with free electron (70%) Positronium formation (30%) p-Ps o-Ps 511 keV 25% 75% =0.125 ns =142 ns slow down 0.27% 511 keV 99.73% 98.7% 1.3% Chemical reactions Conversion Pick-off Altogether ~ 0.5% of 3 annihilations
How can the 3 annihilations be useful? Although 3 events are rare compared 2 events, the information obtained per event is greater than for 2 annihilation It is NOT an alternative but an addition to conventional PET imaging Additional information gained may lead to reduced administered dose Tumour Hypoxia The 3 yield is sensitive to the local chemical environment and may be able to confirm the level of oxygenation in tumours Extracting more information
The concept of 3 imaging in PET r 2 r 3 E 2 r 1 E 1 E 3 z y r x h D 0 3 33 2 2211 rrrrrr 1 xx c E xx c Exx c E p x 0 3 33 2 2211 rrrrrr 1 yy c E yy c Eyy c E p y 0 3 33 2 2211 rrrrrr 1 zz c E zz c Ezz c E p z From the law of momentum conservation: 3 photons of energies E 1,E 2,E 3 detected in coincidence at r 1, r 2, r 3 2D or 3D set of nonlinear equations Solve for r The position of annihilation site recovered from a single event! 2 321 2cmEEE e
New PET scanner design 2 r 1,r 2... conventional PET image List mode r 1,r 2 3 ; E 1, E 2 3... 3 ? Is E 1, E 2 3 > E min < E max ? solve for r ? 3 image reject YES NO YES E 1 + E 2 3 = 1022keV Is r within the object Add to image Coincidence SCA Preamp/ Amp Gating
Conclusions 3 annihilation events can be used for imaging in PET The information conveyed by single 3 event is higher New type of scanner may give an overall improvement in PET imaging at lower doses There are only few 3 events High resolution CZT detectors are required to make 3 imaging possible; scintillation detector energy resolution is insufficient The quality of the 3 image will be rather poor. Further Research Direction: Can the differences of 3 yields in tissues be used to measure tumour hypoxia?
Applying External Micro-PIXE Technique to Investigate Chlorine Diffusion In Mortars AS Clough MS Rihawy FE Gauntlett MJ Mulheron
Surrey External Micro-Beamline Beam from Tandetron
A cylindrical sample of a mortar, containing 1% NaCl by weight, is immersed in water. After immersion the sample is sectioned in planes -one parallel to, one perpendicular to the base - to study chlorine diffusion horizontally and vertically. Water Mortar Cylinder Chloride Diffusion from a Mortar
Samples were placed in the external ion beam, raster scanned over an area 3mm diameter then moved in steps of 3mm to allow a series of scans across the section. Characteristic X-rays for elements found in the samples were mapped.
Conclusion Scanning external beam MeV PIXE analysis provides a simple, rapid and low cost method of determining chlorine profiles in mortars at low levels (~ 0.5%) by weight with a spatial resolution of about 20 microns. We intend to extend this study to various kinds of mortars and concrete.
Ion Beam Developments at Surrey Horizontal nanobeam for ion beam writing and ion beam analysis Vertical single-ion beamline for studying interactions with cells - pioneered independently at Columbia University, NY and the Gray Laboratory, Middlesex by Alumni: David Brenner and Melvyn Folkard. Magnet Computer controlled raster scanner deflection plates Quadrupole focussing magnets Tandetron Object aperture LN 2 cooled sample stage Scanning microbeam target chamber External Scanning microbeam (~ 10 microns spot size) Vertical and horizontal nanobeams (<10 nm spot size) under construction
Ion microbeam analysis of diffusion in materials Tony Clough, Fern Gauntlett, Salah Rihawy ION MICROBEAM ANALYSIS TECHNIQUE APPLICATIONS FUTURE WORK
Side view Front view of sample stage Particle detectors LN 2 cooled sample stage Focussed 3 He or p scanning microbeam X-ray detector Scanning zone Cu blocks Sample Scanning Microbeam Target Chamber HPGe detector
NRA (Nuclear Reaction Analysis) Ions can scatter inner electrons from a target atom. As the electrons rearrange, X-rays characteristic of the target element are produced. L X-rays are produced from the transition of electrons from outer shells to the L shell. K X-rays are produced from the transition of electrons from outer shells to the K shell. Protons detected from the reaction: 3 He + d p + Q = 18.4 MeV PIXE (Particle Induced X-ray Emission)
Water diffusion into fibre optic pressure sensors Fibre optic ~ 125 m in diameter soaked in D 2 O at 210°C and 19 bar for 50 days 1 cm long sections mounted between copper blocks on sample plate and circular cross-section cleaved at block surface. Plate mounted in scattering chamber, cooled with LN 2 and the fibre cross-section exposed to a scanning 2 MeV 3 He beam. The detected protons and X-rays were recorded as a function of beam position.
Copper sample holder Tissue sample Scanned regions appear darker Figure 10: Porcine muscle tissue in copper blocks sample holder, scanned areas visible as discolouration on meat