Andrei Nomerotski 1 Instrumentation for Medical Applications Andrei Nomerotski (Oxford Particle Physics) VC Forum, 17 November 2009

Andrei Nomerotski 2 Particle Detectors in Medicine  Energy scales of modern particle physics are much beyond needs of medicine but detection techniques are similar u High energy particles cascade to low energy particles  Detection of visible light and X-rays is in demand both in medical imaging and particle physics  Medical imaging u Slow rates (~Hz)  Modest # of frames per second u Complicated processing  Each frame is a lot of information u High data rates

Andrei Nomerotski 3 Driving Factors  Huge progress in micro (nano) electronics u New silicon technologies u New types of detectors u Complicated processing at sensor level  New materials  Computing  faster CPU u Taking advantage of Moore’s law u Software sophistication

Andrei Nomerotski 4 Outline  In the following will talk about u Positron Emission Tomography u Medical Imaging using silicon detectors u In Vivo Dosimetry

Andrei Nomerotski 5 Positron Emission Tomography (PET) 5 Cancer diagnostic tool Distinguish normal and cancerous tissue on the basis of their biological function

Andrei Nomerotski 6 FDG-PET: basic principle Two opposite PET detectors operating in coincidence 511 keV 511 keV  -ray 511 keV  -ray 18 F-fluoro-deoxy-glucose

Andrei Nomerotski 7 Whole Body PET  Usually combined with Computer Tomography (CT) u PET accuracy ~5 mm u Overlaid images give better accuracy u CT allow for attenuation corrections  2M scans annually u 20% per year growth

Andrei Nomerotski 8 Scintillator: Converts 511 keV gamma-rays into the light PMTs: Convert the scintillation light into a measurable electrical voltage pulse 511 keV gamma-rays 8 PET detector components

Andrei Nomerotski 9 Solid-State PET Detectors Avalanche photodiode (APD) High detection efficiency (~50%) Wide dynamic range Low gain (~100) Silicon Photomultiplier (SiPM) Work in Geiger mode Gain is comparable to PMTs (~10 6 ) High speed (similar to PMTs) Limited dynamic range Being considered Already developed

Andrei Nomerotski 10 Silicon Photomultiplier (SiPM) SiPM devicesSiPM microcells Schematic diagram 1mm x 1mm HAMAMATSU Inc. Geiger mode operated silicon arrays on a common substrate Invented in 90’s Last years – big improvements in parameters and available bareas

Andrei Nomerotski 11 Silicon Photomultiplier  Hamamatsu MPPC

Andrei Nomerotski 12 New Fast Scintillators  Promising new scintillators: PreLudeTM420 (LYSO) and BrilLanCeTM380 (LaBr3(Ce)) u By Saint-Gobain Cristaux et Detecteurs

Andrei Nomerotski 13 Time Of Flight PET  Use time information to localize interaction with ~few cm precision  Allows for better image quality for same dose u Or lower dose (=higher throughput) for same image quality  Need to achieve ~100 ps timing accuracy u Currently ~400 ps

Andrei Nomerotski 14 Combined PET & MRI  Difficult to combine due to strong magnetic field and high frequency interference  SiPMs work in strong magnetic field  PET scanner inside MRI scanner  Advantage over PET/CT - lower dose From S.Cherry, Advances in PET Imaging Technology

Andrei Nomerotski 15 PET R&D Activities in Oxford Physics  Ongoing R&D on SiPM  can be used for PET  Preparing a bid to Wellcome/STFC to build a TOF-PET demonstrator  Discussing common R&D projects with Churchill  Offer SiPM/TOF-PET MPhys project in Physics

Andrei Nomerotski 16 Medical Imaging

Andrei Nomerotski 17 Medical Imaging  Concentrate on X-ray imaging with silicon detectors  Nicely demonstrates advances in silicon industry u Not driven by science any more rather by telecommunications and PlayStation users  Nowadays use processes with 0.09  m = 90 nm min feature size with 45 nm in sight  Medipix – silicon pixel detector with integrated electronics and readout u Started at CERN in 90’s as by-product of R&D for future LHC experiments u Very successful with dozens of applications outside of PP (and medicine)

Andrei Nomerotski 18 X-Rays in Silicon  Visible photon range few  m  20keV X-ray range 5  m  100 keV X-ray range 80  m  For larger energies need different materials (higher Z)

Andrei Nomerotski 19 Hybrid-Pixel Detectors Pulse processing electronics provides simultaneously fast and noise free images

Andrei Nomerotski 20 Medipix2 Bump Bonding

Andrei Nomerotski 21 Charge sensitive preamplifier with individual leakage current compensation 2 discriminators with globally adjustable threshold 3-bit local fine tuning of the threshold per discriminator 1 test and 1 mask bit External shutter activates the counter 13-bit counter 1 Overflow bit Signal ~ few 1000 electrons (!) Medipix2 Pixel Cell Schematic

Andrei Nomerotski 22 Medipix2 Cell Layout

Andrei Nomerotski 23 Medipix2 Chip Architecture 256 x 256 pixels 5ms readout time 200MHz) 300  s readout time 100MHz)

Andrei Nomerotski 24 Medipix Data Acquisition  Max frame rates ~ 1 kHz  USB interface- easy to use X-ray detector Medipix with USB interface

Andrei Nomerotski 25 Sample Images

Andrei Nomerotski 26 High resolution X-ray imaging using a micro- focus X-ray source Needle holding the sample Edges are enhanced by phase contrast effect S. Pospisil, J. Jakubek and co-workers, IEAP, CTU, Prague, CZ

Andrei Nomerotski 27 Future Trends  Microelectronics becomes more and more complex u Intelligence at pixel level  Medipix3 introduce corrections to amplitude to improve amplitude resolution

Andrei Nomerotski 28 Charge summing and allocation concept 55µm The winner takes all

Andrei Nomerotski 29 Medipix3 Simulation  Much improved amplitude resolution  Immune to threshold variations

Andrei Nomerotski 30 Material Reconstruction in CT Photon counting at 8 keV threshold water / non iodine iodine Brightness = density of materials (g/cm 3 )  Measurements in collaboration with the University of Canterbury, Christchurch G. Anton, T. Michel and co-workers, Univ. Erlangen, D  Amplitude information important to distinguish between different materials

Andrei Nomerotski 31 In Vivo Dosimetry  A lot of interest given JAI activities on therapy of cancer using particle accelerators  TLD, diodes, MOSFETs u TLDs are complicated to process u Diodes need a cable and continuous readout  New: MOSFET u Metal Oxide Semiconductor Field Effect Transistors u Absorbed dose change characteristics of MOSFET u Compact ~1 mm  Much needed instrument with a lot of room for improvement and new ideas scanditronix-wellhofer.com

Andrei Nomerotski 32 Medipix Activities in Oxford Area  Several Medipix/Timepix users u Diamond Light Source for crystal diffraction studies u Oxford Chemistry/Physics for Ion Imaging Mass Spectrometry u Oxford Engineering for Mammography  Talking to each other, may think about joining the Medipix collaboration

Andrei Nomerotski 33 Future: Monolithic Sensors  Future trend is in integration of detector and electronics in one sensor, MAPS (Monolithic Active Pixel Sensor)

Andrei Nomerotski 34 Monolithic Sensors with 3D Integration  Technologies becoming available to thin silicon wafers to 10 microns and to bond them together  New approach to monolithic sensors: 3D integration  Precision 1  m alignment u Interconnection of wafers by metal vias

Andrei Nomerotski 35 Ultra Thin Devices  First attempts to produce ultra-thin devices in industry and for particle detection are under way  hopefully will make its way to medical applications as well

Andrei Nomerotski 36 Summary  Enormous progress in detector technologies and nanoelectronics which can be applied to medical applications u Especially to imaging  A lot of interest from Physics side to apply better detectors to medicine  Medical applications are driven by practical needs and economics  benefit from communications between two communities Acknowledgements: Medipix collaboration