Abstract:
A method for providing  11 C-labeled cyanides from  11 C labeled oxides in a target gas stream retrieved from an irradiated high pressure gaseous target containing O 2 , wherein  11 C labeled oxides are reduced with H 2  in the presence of a nickel catalyst under a pressure and a temperature sufficient to form a product stream comprising at least about 95% 11 CH   4 , the  11 CH 4  is then combined with an excess of NH 3  in a carrier/reaction stream flowing at an accelerated velocity and the combined  11 CH4 carrier/reaction stream is then contacted with a platinum (Pt) catalyst particulate supported on a substantially-chemically-nonreactive heat-stable support at a temperature of at least about 900° C., whereby a product stream comprising at least about 60% H  11 CN is provided in less than 10 minutes from retrieval of the  11 C labeled oxide.

Description:
CROSS-REFERENCE TO RELATED APLICATIONS 
       [0001]    This application is a divisional of U.S. patent application Ser. No. 13/584,033, filed Aug. 13, 2012, which claims benefit of U.S. Provisional Application Ser. No. 61/524,121, filed on Aug. 16, 2011, the entire contents of both of which are incorporated herein by reference. 
     
    
     STATEMENT OF GOVERNMENT LICENSE RIGHTS 
       [0002]    This invention was made with Government support under contract number DE-ACO2-98CH10886, awarded by the U.S. Department of Energy and under grant number R21A1084189, awarded by the U.S. National Institutes of Health. The Government has certain rights in the invention. 
     
    
     FIELD OF THE INVENTION 
       [0003]    The present invention relates generally to chemical processes for synthesizing radioactive compounds for imaging, such as by positron emission tomography (PET). More particularly, the present invention relates to a compact, stand-alone instrument and method for producing C-11 cyanide (H 11 CN) in a fast and efficient manner. 
       BACKGROUND 
       [0004]    Positron emission tomography (PET) is a molecular imaging technology that is increasingly used for detection of disease. PET imaging systems create images based on the distribution of positron-emitting isotopes in the tissue of a patient. The isotopes are typically administered to a patient by injection of PET radiotracer probe molecules that comprise a positron-emitting isotope, (e.g. carbon-11, nitrogen-13, oxygen-15, or fluorine 18), covalently attached to a molecule that is readily metabolized or localized in the body or that chemically binds to receptor sites within the body. For PET radiotracer probes the short half-lives of the positron emitting isotopes require that synthesis, analysis and purification of the probes are completed rapidly. 
         [0005]    Carbon-11 (C-11) cyanide is a highly valuable precursor molecule for PET radiotracer synthesis by chemical transformations such as displacement and cross-coupling reactions. The resulting C-11 cyano-compounds can also be converted to various functional groups such as amines, amides, carboxylic acids, which are abundant in various biological substrates, drugs and radiotracers. Various methods for synthesizing C-11 cyanide are known in the art. However, conventional C-11 cyanide production systems that are currently commercially available are large in size, not stand-alone or not cost-effective. 
         [0006]    Moreover, due to the short half-life (20 min) of C-11, a short production time is required. However, the production time involved in typical C-11 cyanide production systems of the prior art leave little remaining time for useful analytic purposes. 
         [0007]    Accordingly, there is a need to develop smaller or miniaturized systems and devices that are capable of processing small quantities of molecular probes. In addition, there is a need for such systems that are capable of expediting chemical processing to reduce the overall processing or cycle times, simplifying the chemical processing procedures, and at the same time, provide the flexibility to produce a wide range of probes, biomarkers and labeled drugs, or drug analogs, inexpensively. 
       SUMMARY 
       [0008]    The present method relates to providing  11 C labeled cyanides from  11 C labeled oxides in a target gas stream retrieved from an irradiated high pressure gaseous target containing O 2 . The method generally includes:
       (i) reducing  11 C labeled oxides with H 2  in the presence of a nickel catalyst under a pressure and a temperature sufficient to form a product stream comprising at least about 95%  11 CH 4 ;   (ii) combining the  11 CH 4  with an excess of NH 3  in a carrier/reaction stream flowing at an accelerated velocity; and   (iii) contacting the combined  11 CH 4  carrier/reaction stream with a platinum (Pt) catalyst particulate supported on a substantially-chemically-nonreactive heat-stable support at a temperature of at least about 900° C., and more preferably is at least about 940° C., whereby a product stream comprising at least about 60% H 11 CN is provided in less than 10 minutes from retrieval of the  11 C labeled oxides.       
 
         [0012]    In a preferred embodiment, the method further includes mixing the  11 CH 4  and NH 3  carrier/reactant stream prior to contacting the stream with the Pt catalyst at elevated temperature. The method further preferably includes removing unreacted  11 CO 2  from the product stream resulting from step (i) to provide a cleansed  11 CH 4  product stream of increased  11 CH 4  content. The act of removing preferably includes passing the product stream resulting from step (i) through a soda lime trap whereby  11 CO 2  is scrubbed from the stream. 
         [0013]    The act of reducing preferably includes passing a pressurized stream of  11 CO 2 , NH 2 , and N 2  through a heated zone packed with a mixture of nickel (Ni) catalyst powder and a molecular sieve, such heated zone having an entrance and an exit. The heated zone is preferably arranged with subzones of substantially all nickel catalyst powder at the entrance of the zone and at the exit of the zone so that the nickel-only subzones sandwich a third subzone which houses the mixture of the nickel powder and the molecular sieve. The molecular sieve is provided in an amount sufficient to trap substantially all of the nonreacted  11 CO 2  present in the pressurized stream for subsequent desorption in the presence of heat for reduction to  11 CH 4 . 
         [0014]    The act of flowing at accelerated velocity includes passing NH 3  gas to the combining of (ii) at a rate of at least about 550 ml/min up to a speed which permits substantially complete reaction of the  11 CH 4  in the combined stream to form H 11 CN. The accelerated velocity for passing the NH 3  gas is preferably a rate from about 600 ml/min to about 700 ml/min, and more preferably, a rate from about 640 ml/min to about 660 ml/min. 
         [0015]    In a preferred embodiment, the platinum catalyst particulate of (iii) is platinum black and the substantially-chemically-nonreactive heat-stable support is a molecular sieve, which is heat stable up to at least 1500° C. 
         [0016]    The present method includes miniaturizing a reaction furnace having a reaction chamber for reacting  11 CH 4  with NH 3  to form H 11 CN in the presence of a platinum catalyst. The method generally includes:
       (i) supporting platinum particulate with a substantially-chemically-nonreactive heat-stable support; and   (ii) minimizing the size of said reaction chamber for housing said supported platinum particulate to obtain high efficiency H 11 CN conversion from a reaction stream passed therethrough, said reaction stream comprising substantially and NH 3 ,
 
whereby the size of said furnace can be miniaturized.
       
 
         [0019]    In a preferred embodiment, the platinum particulate is platinum black and the substantially-chemically-nonreactive heat-stable support is a molecular sieve. The step of minimizing preferably means providing a chamber having a volume not greater than about 30 cubic centimeters. 
         [0020]    The present method further involves optimizing the conversion of  11 CO 2  to form  11 CH 4  by reducing  11 CO 2  with H 2  using nickel catalyst. The method generally includes:
       (i) passing a  11 CO 2  stream with a stream of N 2  and H 2  under pressure through a chemical reduction zone having an entry and an exit, such zone subdivided into three subzones, an entry subzone, a middle subzone, and an exit subzone, the entry and exit subzones are provided with a substantially only nickel-catalyst powder and the middle subzone is provided with a mixture of nickel catalyst powder and molecular sieve; and   (ii) heating the chemical reduction zone to promote such reduction, whereby  11 CO 2  is at least partially reduced in the entry and exit subzone while the substantial balance of  11 CO 2  is absorbed by the molecular sieve and is subsequently desorbed therefrom in the presence of heat and substantially completely reduced in the presence of the nickel powder.       
 
         [0023]    A present system is also provided and relates to producing H 11 CN gas from  11 C-labeled oxides in less than ten (10) minutes. The present system generally includes a  11 CO 2  inlet conduit for receiving and conveying  11 CO 2  gas from a target, a H 2  inlet conduit for receiving and conveying H 2  gas from a source, a N 2  inlet conduit for receiving and conveying N 2  gas from a source, a nickel furnace fluidly connected with the  11 CO 2  inlet, the H 2  inlet and the N 2  inlet for receiving the  11 CO 2  gas, the H 2  gas and the N 2  gas respectively therefrom. The furnace heats the  11 CO 2  gas, the H 2  gas and the N 2  gas in the presence of a nickel catalyst contained therein to produce  11 CH 4  gas. A  11 CH 4  conduit is connected to an outlet of the nickel furnace for receiving and conveying the  11 CH 4  gas from the nickel furnace, a NH 3  inlet conduit for receiving and conveying NH 3  gas from a source, a platinum furnace fluidly connected with the  11 CH 4  conduit and the NH 3  inlet conduit for receiving the  11 CH 4  gas and the NH 3  gas respectively therefrom and for heating the  11 CH 4  gas and the NH 3  gas in the presence of a platinum catalyst. The platinum furnace produces H 11 CN gas and a H 11 CN outlet conduit is fluidly connected to an outlet of the platinum furnace for receiving and conveying the H 11 CN gas from the platinum furnace. The  11 CO 2  inlet conduit, the H 2  inlet conduit, the N 2  inlet conduit, the nickel furnace, the  11 CH 4  conduit, the NH 3  inlet conduit, the platinum furnace and the H 11 CN outlet conduit collectively define a total system gaseous volume of about less than 18 mL whereby the system provides a total system cycle time for producing H 11 CN gas of less than ten (10) minutes. In a preferred embodiment, the system occupies a space less than or equal to about 20 cm×28 cm×27 cm. 
         [0024]    Also, the system preferably includes a soda lime trap disposed in the  11 CH 4  conduit for removing unreacted  11 CO 2  gas from the  11 CH 4  conduit. The system preferably further includes a mixer fluidly connected with the  11 CH 4  conduit and the NH 4  inlet conduit for respectively receiving and mixing the  11 CH 4  gas and the NH 3  gas from the  11 CH 4  conduit and the NH 3  inlet conduit. 
         [0025]    The nickel furnace preferably includes an alumina tube and an electrical resistance heating wire wrapped around the alumina tube. The alumina tube preferably has a length of about 4.5 cm, an outer diameter of about 1.3 cm and an inner diameter of about 0.95 cm. 
         [0026]    The platinum furnace preferably includes an alumina tube and an electrical resistance heating wire wrapped around the alumina tube. The alumina tube preferably has a length of about 15 cm, an outer diameter of about 2 cm and an inner diameter of about 1.6 cm. 
         [0027]    The preferred embodiments of the present C-11 cyanide production system and the method for producing C-11 cyanide, as well as other objects, features and advantages of this invention, will be apparent from the following detailed description, which is to be read in conjunction with the accompanying drawings. The scope of the invention will be pointed out in the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]      FIG. 1  is a schematic drawing of the present C-11 cyanide production system. 
           [0029]      FIG. 2  is a side view of the nickel furnace of the system shown in  FIG. 1 . 
           [0030]      FIG. 3  is a cross-sectional view of the soda lime trap of the system shown in  FIG. 1 . 
           [0031]      FIG. 4  is a cross-sectional view of the mixer of the system shown in  FIG. 1 . 
           [0032]      FIG. 5  is a side view of the platinum furnace of the system shown in  FIG. 1 . 
           [0033]      FIG. 6  is a diagrammatic side view of an embodiment for rapidly cooling the nickel furnace of the present invention. 
           [0034]      FIG. 7  is a schematic diagram of an alternative embodiment of the present invention, wherein two nickel furnaces are provided in parallel. 
           [0035]      FIG. 8  is a diagrammatic cross-sectional view of a preferred embodiment of a nickel catalyst package used in the nickel furnace of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0036]    Referring first to  FIG. 1 , the present system  10  is generally a combination of commercially available and custom design components provided in a miniaturized form in order to provide a compact and efficient system for producing C-11 cyanide (H 11 CN) gas. This system  10  is preferably supported on a compact “mother board” frame or plate (not shown) having overall dimensions of approximately 20 cm (D)×28 cm (W)×27 cm (H). Hardware for attaching the components to the frame or plate preferably take the form of clips or other such brackets fixed to the plate or frame, which allow for quick and releasable plug-in connection of the various components. As a result, easy access and quick replacement of the components is provided with the system  10  of the present invention. 
         [0037]    The present system  10  includes four inlet ports  12 ,  14 ,  16 ,  18  for introducing the necessary process gases to the system. The inlet ports  12 ,  14 ,  16 ,  18  are preferably in the form of needle valves, or other type of quick-connect devices for connecting flexible hoses or other conduits from their respective gas sources. Inlet port  12  receives radioactive C-11 carbon-dioxide ( 11 CO 2 ) gas from a target source. Inlet port  14  receives nitrogen (N 2 ) gas from a source. Inlet port  16  receives hydrogen (H 2 ) gas from a source and inlet port  18  receives ammonia (NH 3 ) gas from a source. 
         [0038]    Immediately down-stream of each inlet port  12 ,  14 ,  16 ,  18  is a 2-way solenoid valve  20 ,  22 ,  24 ,  26  and a flow control valve  28 ,  30 ,  32  and  34  for controlling and regulating the flow of the respective process gas into the system. Also, preferably provided on at least the nitrogen (N 2 ) inlet port  14  and the ammonia (NH 3 ) inlet port  18  are pressure regulators  36 ,  38  to control the respective pressure of the nitrogen and ammonia gases entering the system. 
         [0039]    The solenoid valves, control valves, pressure regulators and needle valves are generally commercially available parts but are selected to provide a small cross-sectional flow. Similarly, the tubing or conduits for conveying the process gases between the various components of the system have a relatively small cross-section of equal to or less than about 0.2 cm to minimize the overall volume of the gas in the system. As a result, the overall flow cycle time is reduced and, as will be discussed in further detail below, the conditioning time (i.e., the time required to initially bring the system to operational condition) can also be reduced. 
         [0040]    The C-11 carbon dioxide ( 11 CO 2 ) inlet  12 , the nitrogen (N 2 ) inlet  14  and the hydrogen (H 2 ) inlet  16  are all disposed upstream and are fluidly connected to a nickel furnace  40 . A pressure gauge  42  is also preferably provided upstream of the nickel furnace for monitoring the pressure of the process gases entering the nickel furnace. The pressure gauge  42  is connected to a vent  46  via a 3-way solenoid valve  48  for venting process gasses should the pressure get too high. 
         [0041]    The C-11 carbon dioxide ( 11 CO 2 ) line  12 A, the nitrogen (N 2 ) line  14 A and the hydrogen (H 2 ) line  16 A all preferably meet and feed into a single two way solenoid valve  44  located immediately upstream of the nickel furnace  40 . The two way nickel furnace inlet solenoid valve  44  provides for a single shut-off of all gases entering the nickel furnace if required. 
         [0042]    As shown additionally in  FIG. 2 , the nickel furnace  40  is a custom designed, miniaturized furnace, which permits extremely rapid heat-up and cool-down time, as compared to nickel furnaces used in conventional C-11 cyanide production systems. The nickel furnace  40  includes a commercially available alumina tube  50  having a length of about 4.5 cm, an outer diameter of about 13 mm and an inner diameter of about 9.5 mm. A length of Kanthal A-1® electrical heating wire  52  is tightly wrapped around the outer surface of the alumina tube  50 . The wire  52  preferably extends along the central axial length of the tube  50  to create a heating zone  54  having a length of about 3.8 cm. Opposite ends of the wire  52  are preferably provided with electrical terminals or are otherwise exposed to allow for connection to an electric source. 
         [0043]    The wire  52  preferably has a resistance of 4.147 ohms/foot to provide a total resistance of 32 ohms. Therefore, providing a current of 3.75 A would produce a heater producing 450 W. With this design, the nickel heater  40  can be heated from room temperature to 400-450° C. in approximately 10-15 seconds. 
         [0044]    The electrical heating wire  52  can be fixed to the tube  50  using a commercially available ceramic paste. Alternatively, the wire  52  can be releasable from the tube  50  to enable a rapid cool-down of the tube. In particular, the wire  52  and the tube  50  can be assembled to allow the pre-formed coiled wire to be axially translated away from the tube in order to separate the tube from the still hot wire after the heating process is complete, as shown in  FIG. 6 . In this manner, the tube  50  will cool down faster than the heating wire, which will provide a quicker cycle time to repeat the process. 
         [0045]    Another way to improve cycle time of the system, with respect to the heating and cooling time required for the nickel furnace  40 , is to provide the system with two nickel furnaces  40   a  and  40   b  in parallel, as shown in  FIG. 7 . Thus, while one of the furnaces  40   a,  for example, is in use and being heated, the other furnace  40   b  is not in use and is being cooled. In this case, a three-way valve  55  is provided to divert the incoming gas to the furnace  40   a  in use, while the other furnace  40   b  cools. Once the reaction is complete in the furnace  40   a  in use, the reacted gas is evacuated and this furnace  40   a  is allowed to cool down. In the meantime, once the idle furnace  40   b  is sufficiently cool, the three-way valve  55  switches over to divert gas to this furnace  40   b,  while the other furnace  40   a  cools. The result is a dramatic reduction in system down-time, which would otherwise be required to allow a single nickel furnace to cool after each cycle. 
         [0046]    In any case, the nickel furnace  40  contains a nickel catalyst, which is used to react the C-11 carbon dioxide ( 11 CO 2 ) gas fed to the furnace. The nickel catalyst is preferably provided in a nickel catalyst package  57 , as shown in  FIG. 8 , which can be inserted into the tube  50  of the nickel furnace  40 . The nickel catalyst package  57  is preferably about 2.5-3.0 cm long and is divided into subzones. A central subzone is defined by a molecular sieve  59  and an entrance subzone  61   a  and an exit subzone  61   b  are respectively defined by two nickel plugs  62  bounding opposite ends of the sieve  59 . 
         [0047]    The sieve  59  is preferably a 4 A 80/100 mesh sieve. A suitable molecular sieve for use in the present system is available at Grace Davison Discovery Science—Catalog:5624 (www.discoverysciences.com). The sieve  59  captures an amount of nickel catalyst powder for trapping un-reacted C-11 carbon dioxide ( 11 CO 2 ) gas. A suitable nickel catalyst powder can be obtained from Shimadzu Corp. under the trade name of Shimalite-Ni (reduced), P/N 221-27719, Lot No. 591461. In a preferred embodiment, about 130 mg nickel powder is captured in 260 mg of nickel sieve. 
         [0048]    The nickel plugs  62  are essentially high concentration nickel catalyst powder packed together to form a relatively dense disc-shaped element, as compared to the sieve  59 . In a preferred embodiment, each nickel plug  62  contains about 20 mg of nickel powder. This results in a nickel package  57  having a nickel/molecular sieve ratio of about 170 mg/260 mg. 
         [0049]    It has been found with conventional nickel catalyst packages, which typically consist of only a molecular sieve containing the nickel catalyst without nickel end plugs, most of the chemical reaction occurs at the gas entrance and exit portions of the sieve. As a result, the ends of conventional nickel catalyst packages are typically depleted of nickel catalyst well before the center portion of the package. 
         [0050]    By providing a higher concentration of nickel, in the form of nickel plugs  62 , at the entrance and exit regions of the package  57  with the present system on, more efficient use of the nickel catalyst can be achieved. Specifically, the nickel package  57  of the present system optimizes the process of conversion of  11 CO 2  to form  11 CH 4  by reducing  11 CO 2  with H 2  using nickel catalyst. 
         [0051]    Thus, a  11 CO 2  stream with a stream of N 2  and H 2  is passed under pressure through the nickel package  57  in the nickel furnace  40 , wherein the nickel package forms a chemical reaction zone having an entry and an exit. The chemical reaction zone is subdivided into an entry subzone  61   a,  a middle subzone  61   c,  and an exit subzone  61   b,  wherein the entry and exit subzones are provided with a nickel catalyst powder in a concentrated form (i.e., the nickel plugs  62 ) and the middle subzone is provided with a mixture of nickel catalyst powder and molecular sieve  59 . The chemical reduction zone is then heated to promote the reduction, whereby  11 CO 2  is at least partially reduced in the entry and exit subzone while the substantial balance of  11 CO 2  is absorbed by the molecular sieve and is subsequently desorbed therefrom in the presence of heat and substantially completely reduced in the presence of the nickel powder. 
         [0052]    As a result, the package  57  can be made smaller, while providing the same amount of nickel catalyst as compared with conventional nickel catalyst packages. In turn, by making the nickel catalyst package  57  smaller, the nickel furnace  40 , and thus the entire system can be made smaller. 
         [0053]    Returning to  FIG. 1 , a first radiation detector  56  and a cooling fan  58  are preferably provided immediately adjacent to the nickel furnace  40 . The first radiation detector  56  is provided to monitor un-reacted C-11 carbon dioxide ( 11 CO 2 ) gas in the nickel furnace  40 , while the cooling fan  58  is provided to provide for rapid cooling the nickel furnace once the reaction time is complete. With the cooling fan  58  provided, the heat nickel furnace  40  can cool from 450° C. to room temperature in approximately 15 minutes. 
         [0054]    Connected to the outlet of the nickel furnace  40  is a nickel furnace outlet line  60  for delivering reacted gas from the nickel furnace further along the system. Preferably provided in the nickel outlet line  60  is a two-way solenoid valve  63  which allows for the control of reacted gas entering the outlet line  60  from the nickel furnace  40 . The outlet line  60  further preferably includes a three-way solenoid valve  64  for diverting converted C-11 methane ( 11 CH 4 ) gas and un-reacted C-11 carbon dioxide ( 11 CO 2 ) gas from the system. A second three-way solenoid valve  66  can be provided to further divert the converted C-11 methane ( 11 CH 4 ) gas and/or the un-reacted C-11 carbon dioxide ( 11 CO 2 ) gas to a vent  68  or an access outlet  70 . 
         [0055]    The converted C-11 methane ( 11 CH 4 ) gas not diverted from the system  10  is then fed into a sodalime trap inlet line  72 , which feeds the C-11 methane ( 11 CH 4 ) gas to a sodalime trap  74 . As shown additionally in  FIG. 3 , the sodalime trap  74  is customized and designed on a miniaturized scale, to remove unwanted C-11 carbon dioxide ( 11 CO 2 ) from the system. The sodalime trap  74  is essentially a narrow tube  76  having an amount of sodalime  78  contained therein. The tube  76  includes a removeable cap  80  threaded at one end of the tube to permit replenishment of the sodalime  78  in the trap  74  as needed. The cap preferably includes an inlet  82  for connection to the sodalime inlet line  72 . Provided at the opposite end of the tube  76  is an outlet  84  for connection to a sodalime outlet line  86 . 
         [0056]    The sodalime trap  74  removes essentially all of the un-reacted C-11 carbon dioxide ( 11 CO 2 ) from the system. In this regard, a second radiation detector  88  is preferably provided adjacent the sodalime trap  74  to monitor any un-reacted C-11 carbon dioxide ( 11 CO 2 ). 
         [0057]    The sodalime outlet line  86  meets with an ammonia (NH 3 ) line  90 , which feeds ammonia gas from the ammonia inlet  18  to the system. The ammonia (NH 3 ) line  90  and the sodalime trap outlet line  86  feed a mixer  92 , which mixes the ammonia (NH 3 ) gas and the C-11 methane ( 11 CH 4 ) gas. 
         [0058]    As additionally shown in  FIG. 4 , the mixer  90  is also a custom made part that provides efficient mixing on a small scale. The mixer  90  includes a tube  90  having a cap  94  connected at an inlet end of the tube and an outlet  96  connected at the opposite end of the tube. The cap  94  is preferably connected to the inlet end of the tube  92  via a threaded connection to allow for removal of the cap as needed. 
         [0059]    The cap is formed with a needle nozzle  98  which extends into the interior of the tube  92 . The needle nozzle  98  is closed at its distal end and is provided with a plurality of apertures  100  through which gas fed into the interior of the nozzle may exit. Extending outwardly from the cap in a direction opposite to the inward direction of the needle nozzle  98  is an inlet port  102  for connection with a mixer inlet line  104 , which in turn is connected with the sodalime outlet trap  86  and the ammonia (NH 3 ) inlet line  90 . An internal conduit  106  extends from the cap inlet  102  to the needle nozzle  98  and is in fluid communication with the plurality of apertures  100  formed in the needle nozzle. Thus, gas flowing from the mixer inlet line  104  into the mixer  90  exits through the apertures  100  of the needle nozzle  98  into the interior of the tube  92  in a manner which will provide efficient mixing of the ammonia (NH 3 ) and the C-11 methane ( 11 CH 4 ) gases. 
         [0060]    A platinum furnace inlet line  108  is connected to the outlet  96  of the mixer  90  for delivering the mixed ammonia (NH 3 ) and C-11 methane ( 11 CH 4 ) gases to a platinum furnace  110 . As shown additionally in  FIG. 5 , the platinum furnace  110  is also a custom made part designed with the goals of miniaturization and rapid heating in mind. In this regard, the platinum furnace includes a quartz tube  112  wrapped with a Kanthal A-1® electrical heating wire  114 . The quartz tube is preferably about 150 mm in length, having an outer diameter of 20 mm and an inner diameter of 16 mm. The wire  114  is wrapped around the outer surface of the quartz tube  112  along a central length of the tube to provide a heating zone  116  of approximately 100 mm in length. The Kanthal A-1® heating wire  114  preferably has a 24 AWG, a length of about 6.8 meters and a diameter of 1 mm. The wire has a maximum operating temperature of between 1350-2460° C. and is applied to the quartz tube  112  with a commercially available ceramic paste. Opposite ends of the wire are preferably provided with electrical terminals or are otherwise exposed to allow for connection to an electric source. 
         [0061]    The platinum furnace  110  further contains an amount of platinum catalyst for converting the mixed ammonia (NH 3 ) and C-11 methane ( 11 CH 4 ) gases to C-11 cyanide (H 11 CN) gas. The platinum catalyst is provided as a particulate supported on a substantially chemically non-reactive, heat stable support. The support can be provided in the form of a 3-5 platinum gauze. For example, two platinum gauze pieces, (Product Number: 298107-1.7G), having a 5 cm×5 cm size and totaling about 2-9 grams can be packed in the quartz tube. 
         [0062]    However, in a preferred embodiment, the platinum black powder is captured or otherwise supported in a molecular sieve. Thus, a molecular sieve is preferably utilized as the platinum black powder support. Any commercially available 100% platinum black powder can be used. A suitable platinum black catalyst powder is supplied by Engelhard Industries, Inc., 113 Astor Street, Newark, N.J. under for example, Lot #10-077. The molecular sieve preferably has a size of about 4 Angstroms. 
         [0063]    It has been surprisingly found that a molecular sieve supporting platinum black provides an efficient means for providing platinum to the high-temperature reaction within the platinum furnace  110 . Specifically, the surface area of available platinum is greatly increased by supporting platinum black in the molecular sieve. The lower limit of the amount of platinum black provided in the sieve is determined by the amount sufficient to catalyze the mixed ammonia (NH 3 ) and C-11 methane ( 11 CH 4 ) gases to C-11 cyanide (H 11 CN). The upper limit of the amount of platinum black provided in the sieve is determined by the amount at which platinum coagulation will occur within the platinum furnace tube. 
         [0064]    A platinum furnace outlet line  118  is fluidly connected to the platinum furnace outlet for removing reacted C-11 cyanide (H 11 CN) gas from the platinum furnace  110 . A two-way solenoid valve  120  and a flow meter  122  are provided in the platinum furnace outlet line  118  to regulate the flow of the C-11 cyanide (H 11 CN) gas from the platinum furnace  110 . A three-way solenoid valve  124  is also preferably provided in the platinum furnace outlet line  118  to selectively allow for extraction of the C-11 cyanide (H 11 CN) gas from the system or to divert the C-11 cyanide (H 11 CN) gas back to the three-way solenoid valve  48  provided in the reacted gas lines  12 A,  14 A,  16 A to divert the cyanide gas to the vent  46 . 
         [0065]    Having described the components of the system  10 , operation of the system will now be described in the following EXAMPLE of an actual use of the system, with reference to the drawings. 
       EXAMPLE 
       [0066]    Radioactive C-11 carbon dioxide ( 11 CO 2 ) gas was taken from a target and delivered to the nickel furnace  40  upon the opening of solenoid valves  20 ,  44 ,  63  and  64 . Once the first radiation detector  56  hit its plateau all valves were closed. Solenoid valves  44  and  24  were then opened to feed hydrogen (H 2 ) gas to the nickel furnace. Once the pressure gage  42  reached 10-15 psi, the solenoid valves  44  and  24  were closed. Nitrogen gas was then introduced at a pressure of about 8.5 psi. This processing step took about 2 minutes. 
         [0067]    The nickel furnace  40  was then heated to 450° C. in less than one minute. Once at operating temperature, the carbon dioxide was heated for about 3 minutes to convert the C-11 carbon dioxide ( 11 CO 2 ) gas to C-11 methane ( 11 CH 4 ) gas. During heating, the cooling fan  58  was turned off. Once heating was complete, the solenoid valves  26  and  120  were opened to release the converted C-11 methane ( 11 CH 4 ) gas to the platinum furnace  110 , which had been preheated to 950° C. Preheating of the platinum furnace took about 10 minutes. 
         [0068]    Ammonia gas was then fed to the system at a pressure of about 6.5 psi. The ammonia gas was mixed with the methane gas in the mixer  90  and was delivered to the platinum furnace. The platinum furnace  110  converted the C-11 methane ( 11 CH 4 ) gas to a product stream containing about 80% C-11 cyanide (H 11 CN) gas. This step took about 2 minutes. 
         [0069]    To cool the nickel furnace  40 , solenoid valves  24 ,  44 ,  63  and  64  were opened to allow hydrogen (H 2 ) to flow. The cooling fan  58  was now turned on until the nickel furnace  40  cooled to below 30° C. 
         [0070]    C-11 cyanide (H 11 CN) gas production results utilizing platinum black catalyst powder supported in a molecular sieve are as follows: 
       Run #1  
       [0071]    1 min beam: 50-70 mCi 
         [0072]    After 9 mins—End of Beam (BOB): 22.4 mCi 
       Run #2   
       [0073]    After 7 mins—EOB: 24.1 mCi 
       Run #3   
       [0074]    After 7 mins—EOB: 22.6 mCi 
         [0075]    Thus, the present system utilizes custom designed furnaces, which are capable of heating to adequate temperatures for both reduction of CO 2  (preferably, 420° C.) and formation of C-11 CN (preferably 800-900° C.) within 20 min to be ready for the production from the start. The whole synthesis time is 6 min, which is faster than commercially available systems (about 10 min). Also, the recycle time is 10 min (i.e., every 10 min, another batch of C-11 CN can be produced). 
         [0076]    It is also conceivable that the system of the present invention can be equipped with multiple  11 CO 2  (nickel)/ 11 CH 4  (platinum) furnaces, which allows more than two productions consecutively without delaying to accommodate a demanding production schedule. 
         [0077]    The present system is stand-alone and small enough to be portable (20 cm (D)×28 cm (W)×27 cm (H)), as long as the sources of gases are connected. The product ion control for synthesis can be controlled by one-button (work-away mode) or step-by-step modes. If needed, each valve or furnace can be controlled manually in case of emergency. The control box module (35.5 cm (L)×25.5 cm (W)×8 cm (H)) is connected to a conventional computer. The function of each module is designed to work independently and at the same time, if combined, the whole system works as one integrated production system. The radiochemical yield in the prototypical system is high (60-80%) and production has been shown to be reproducible over 100 times. 
         [0078]    As a result of the present system, a cost-effective, stand-alone, and high yielding C-11 cyanide system is provided, which is also very compact and small enough to be workable in a conventional shielded hood of a laboratory. Thus, the small size of the present system requires less lead shielding. 
         [0079]    The present system is also highly flexible to produce other C-11 labeled small molecules itself or integrated with the production of other small molecules such as  11 CO 2 , C-11 methane, and C-11 carbon monoxide. The system also affords a functional modular design with flexibility for functional combination to produce other C-11 molecules with a short production time and recycling time for production schedule. 
         [0080]    Although preferred embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments and that various other changes and modifications may be affected herein by one skilled in the art without departing from the scope or spirit of the invention, and that it is intended to claim all such changes and modifications that fall within the scope of the invention.