核物理探测器技术外文文献英文

Nuclear physics detector technology applied to plant biology research A G Weisenberger a n B Krossa S J Leea J McKissona J E McKissona W Xia C Zorna C R Howell b c A S Crowellb c C D Reidb M Smithd aThomas Jefferson National Accelerator Facility Newport News VA USA bDuke University Durham NC USA cTriangle Universities Nuclear Laboratory Durham NC USA dUniversity of Maryland Baltimore MD USA a r t i c l e i n f o Available online 27 September 2012 Keywords Particle physics detectors Scintillators Positron emission tomography Plant biology a b s t r a c t The ability to detect the emissions of radioactive isotopes through radioactive decay e g beta particles x rays and gamma rays has been used for over 80 years as a tracer method for studying natural phenomena More recently a positron emitting radioisotope of carbon 11C has been utilized as a11CO2 tracer for plant ecophysiology research Because of its ease of incorporation into the plant via photosynth esis the 11CO2 radiotracer is a powerful tool for use in plant biology research Positron emission tomography PET imaging has been used to study carbon transport in live plants using 11CO2 Presently there are several groups developing and using new PET instrumentation for plant based studies Thomas Jefferson National Accelerator Facility Jefferson Lab in collaboration with the Duke University Phytotron and the Triangle Universities Nuclear Laboratory TUNL is involved in PET detector development for plant imaging utilizing technologies developed for nuclear physics research The latest developments of the use of a LYSO scintillator based PET detector system for 11CO2 tracer studies in plants will be briefl y outlined 2012 Elsevier B V All rights reserved 1 Introduction Positron emission tomography PET is a nuclear medicine imaging technology based on in vivo volumetric image reconstruc tion that has been used for both clinical human and preclinical animal applications PET radioisotopes are used as tags on mole cules known to have a biological function within the patient or animal A common use of PET in clinical practice is for the determination of the bio distribution of various cancers In preclini cal applications PET is often used in drug development through animalbasedimagingstudies Additionally positronemitting isotopes have particularly proven to be very useful in plant biology research applications Following is a brief discussion of the use of nuclear physics based technology from two different nuclear physics research laboratories in a new plant biology research program 2 Nuclear physics technology The most used positron emitters are 11C 13N and15O in plant biology applications Often various studies are done utilizing scintil lator counters 1 PIN diodes 2 autoradiography 3 or phosphor image plates 4 to explore uptake partitioning and allocation of 11C or13N labeled photosynthates and compounds in plants Most biologically signifi cant radiotracers utilized in plant ecophysiological studies can utilize positron emitting isotopes making PET a useful imaging modality for this application The 11CO2 tracer is a positron emitter used in plant biology research for instance in carbon transport studies in live plants because it is taken up easily through photosynthesis Plant biology research at the Duke University Phyto tron makes use of the positron emitter trace 11CO2 generated by the 4 MeV tandem Van de Graaff accelerator at the Triangle Universities Nuclear Laboratory TUNL 5 The Duke University Biology Depart ment s Phytotron is located 100 m from the TUNL van de Graaf facility A Tefl on tube passed through underground conduit allows the delivery of 11CO2 gas to a dedicated environmental growth chamber EGC in the Phytotron By making use of nuclear physics detector technology we are developing a plant specifi c PET detector system PhytoPET that is based on detector modules built from individual 5 cm 5 cm Hamamatsu H8500 position sensitive photomultiplier tubes PSPMT Each H8500 PSPMT is coupled to a 48 48 element LYSO Ce scintillator array 10 mm thick arranged with a 1 0 mm pitch custom built by Proteus Inc Chagrin Falls OH as shown in Fig 1 6 EachPhytoPETdetectormodulehasanouterdimension L W H of 120 mm 60 mm 60 mm The modules can be stacked to accommodate different plant shapes Each module is constructed such that when stacked the module is locked into position by a complementary set of three detents and glued metal balls Since blocking light to a plant impacts the plant physiology Contents lists available at SciVerse ScienceDirect journal homepage Nuclear Instruments and Methods in Physics Research A 0168 9002 see front matter 2012 Elsevier B V All rights reserved http dx doi org 10 1016 j nima 2012 08 097 nCorresponding author Tel 1 757 269 7090 E mail address drew jlab org A G Weisenberger Nuclear Instruments and Methods in Physics Research A 718 2013 157 159 studies specularly refl ective detector housing is used Additionally we have constructed a set of aluminum bases which also have the set of three registering balls to support the columns The base plates can also be interlocked by a hinge that allows the column to be positioned at a fi xed angle with respect to the neighbor and the gap between the columns kept to a minimum As shown in Figs 1 and 2 the PhytoPET detector modules can be re arranged and stacked to accommodate various sized plants and plant structures An Ethernet based 12 bit fl ash ADC data acquisition system with on board coincident matrix defi nition which we refer to as EFAD 16 was developed The EFAD 16 ADC was based on a Jefferson Lab VME model called FADC250 7 The FADC250 was designed at Jefferson Lab to support a new high energy physics experiment requiring high resolution and high speed with a distributed triggering system With the capability to handle approximately 20 000 channels and a trigger rate of 200 kHz the FADC was recognized as a capable foundation for a PET system This work leveraged the resources of the Jefferson Lab Fast Electronics Group leading to the development of the EFADC 16 The module form factor was modifi ed from the FADC250 as a VME64 module on a 6U card to a stand alone card No longer requiring the overhead of a VME bus interface the EFADC utilizes Gigabit Ethernet for selected event transmission and direct fi ber optic links for coincidence identifi cation and triggering The EFAD 16 module has the following front end characteristics 16 individual inputs 50Oinput LEMO series 00 Full scale range selectable 0 5 V 1 0 V or 2 0 V Simultaneous sampling 250 Msample s Aperture jitter 0 45 ps RMS 2 bit ADC Integral Nonlinearity70 8 LSB Differential Nonlinearity70 5 LSB Signal to Noise Ratio 56 8 dB 100 MHz 3 Imaging Trials Plans are underway to construct over 20 modules to allow for complete coverage of a small plant Fig 2 shows an initial plant PET study of an oak seedling using fi ve of the modules Iterative limited angle tomographic reconstruction method was used to construct the carbon translocation images of the central plane of Fig 1 Left photographs of a 120 mm 60 mm 60 mm PhytoPET detector module with a sample fl ood scintillator image obtained via the 511 keV photon emission from a 22Na source Right diagrams indicating possible module placement Fig 2 Top photograph and diagram of fi ve PhytoPET detectors used in a EGC during a 11CO2 study Bottom images of carbon translocation in a oak seedling The plant was placed in a 11CO2 atmosphere A montage is shown of carbon translocation from leaf to root over 5 min intervals A G Weisenberger et al Nuclear Instruments and Methods in Physics Research A 718 2013 157 159158 the plant Results indicate that the system has the potential to provide a powerful tool for plant biology research Acknowledgments Support for this research came from the DOE Offi ce of Biological and Environmental Research the DOE Offi ce of Nuclear Physics Grant DE FG02 97ER41033 and National Science Founda tion Grant nos IBN 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