Abstract:
A system and method for measurement of radioactivity concentration of a radiopharmaceutical are disclosed. The radiopharmaceutical may be a radioactive tracer solution including a tracer solution and a buffer solution. The system may include a vial that receives the tracer solution and the buffer solution; a scale; a radioactivity measuring device; and a controller that determines the radioactive concentration based on a measured radioactivity of the tracer solution and the buffer solution in the vial, and a weight of the tracer solution and the buffer solution in the vial. The method may include the steps of (1) transferring the tracer solution into a vial; (2) measuring a radioactivity of the tracer solution in the vial; (3) determining a weight necessary to achieve a desired radioactivity concentration; and (4) diluting the tracer solution in the vial to the determined weight with a buffer solution.

Description:
[0001]    This application is based on and claims the benefit of U.S. Provisional Patent Application No. 60/950,911 filed on Jul. 20, 2007, the disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention generally relates to the measurement of radioactivity, and, more particularly, to a system and method for measurement of radioactivity concentration of a radiopharmaceutical. 
         [0004]    2. Description of the Related Art 
         [0005]    Medical imaging is used extensively to diagnose and treat patients. A number of modalities are well known, such as Magnetic Resonance Imaging (MRI), Computed Tomography (CT), Positron Emission Tomography (PET), and Single Photon Emission Computed Tomography (SPECT). These modalities provide complementary diagnostic information. For example, PET and SPECT scans illustrate functional aspects of the organ or region being examined and allow metabolic measurements, but delineate the body structure relatively poorly. On the other hand, CT and MRI images provide excellent structural information about the body, but provide little functional information. 
         [0006]    PET and SPECT are classified as “nuclear medicine” because they measure an emission of a radioactive tracer that has been injected into a patient. After the radioactive tracer, or radiopharmaceutical, is injected, it is absorbed by the blood or a particular organ of interest. The patient is then moved into the PET or SPECT detector that measures the emission of the radiopharmaceutical and creates an image from the characteristics of the detected emission. 
         [0007]    A significant step in conducting a PET or SPECT scan is the step of acquiring the radioactive tracer. Examples of radiopharmaceuticals include FDG (2-[ 18 F]-fluoro-2-deoxyglucose), other  18 F based fluorinated tracers,  13 N ammonia,  11 C based tracers,  15 O gas, and  15 O water, and others. 
         [0008]    The half lives of these radiopharmaceuticals range from two minutes to two hours. Thus, the injection into the patient and the imaging must take place within a very short time period after production of the radiopharmaceutical. Because of this, it is important for the technician operating the medical imaging device to know the radioactive concentration, as well as the time and date that the radioactive concentration was measured. This may be determined by measuring the total radioactivity of a tracer in an ionization chamber, and taking an aliquot in a syringe to measure the activity concentration. Either the aliquot is put into an ionization chamber or the change of radioactivity of the bulk solution is determined. With the known volume of the aliquot and the measured radioactivity, radioactivity concentration can then be determined. 
       SUMMARY OF THE INVENTION 
       [0009]    A system and method for measurement of radioactivity concentration of a radiopharmaceutical are disclosed. According to one embodiment, the radiopharmaceutical may be radioactive tracer solution including a tracer solution and a buffer solution. The system includes a vial that receives the tracer solution and the buffer solution; a scale; a radioactivity measuring device; and a controller that determines the radioactive concentration based on a measured radioactivity of the tracer solution and the buffer solution in the vial, and a weight of the tracer solution and the buffer solution in the vial. 
         [0010]    In one embodiment, the tracer solution may comprise 2-[18F]-fluoro-2-deoxyglucose. The buffer solution may be a sodium chloride solution. The tracer solution may be provided to the vial by tubing. 
         [0011]    The system may further comprise a gas source in communication with the vial and the buffer solution. The system may also comprise a fill line in communication with the vial. The system may also comprise a plurality of valves that direct the flow of at least a gas and a liquid. The system may also comprise a plurality of filters for filtering at least one of a gas and a liquid. 
         [0012]    The method for measurement of radioactivity concentration of a radiopharmaceutical may include the steps of (1) transferring the tracer solution into a vial; (2) measuring a radioactivity of the tracer solution in the vial; (3) determining a weight necessary to achieve a desired radioactivity concentration; and (4) diluting the tracer solution in the vial to the determined weight with a buffer solution. 
         [0013]    The method may also include the steps of determining an initial weight for the vial, and determining a radiation base noise level. 
         [0014]    The method may also include the step of mixing the tracer solution and the buffer solution. 
         [0015]    The step of transferring a tracer solution into a vial may include opening a valve between a source of the tracer solution and the vial, and filtering the tracer solution. 
         [0016]    The step of diluting the tracer solution in the vial to the determined weight with a buffer solution may include pressurizing a container containing the buffer solution with a gas from a gas source, opening a valve between the container containing the buffer solution and the vial, and transferring the buffer solution to the vial. 
         [0017]    The step of mixing the tracer solution and the buffer solution may include opening a valve between a gas source and the vial, filtering the gas from the gas source, and bubbling the gas through the tracer solution and buffer solution. 
         [0018]    It is a technical advantage of the present invention that a system and method of measuring radioactivity concentration of a radiopharmaceutical are disclosed. It is another technical advantage of the present invention that the tubing that communicates the different parts of the system may be replaceable. It is another technical advantage of the present invention that the system and method minimize human interaction. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    For a more complete understanding of the present invention, the objects and advantages thereof, reference is now made to the following descriptions taken in connection with the accompanying drawings in which: 
           [0020]      FIG. 1  is a block diagram of a system for measurement of a radioactivity concentration of a radiopharmaceutical according to one embodiment of the present invention. 
           [0021]      FIG. 2  is a flowchart depicting a method for measurement of a radioactivity concentration of a radiopharmaceutical according to one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0022]    Preferred embodiments and their advantages may be understood by referring to  FIGS. 1-2 , wherein like reference numerals refer to like elements. 
         [0023]    Disclosed herein is a novel system and method for making this determination quickly and with no, or minimal, human interaction. 
         [0024]    The present invention may be implemented in a transportable manufacturing facility for radioactive materials. An example of such is described in U.S. Patent Publ. No. 2004/0086437, the disclosure of which is incorporated by reference in its entirety. 
         [0025]    Referring to  FIG. 1 , a system for the measurement of radioactivity concentration and total radioactivity of a radiopharmaceutical is disclosed. The radiopharmaceutical may be a radioactive tracer solution including a tracer solution  110  and a buffer solution  150 . According to one embodiment, system  100  includes bulk vial  120 , ionization chamber  130 , scale  140 , gas source  160 , and filling line  170 . Filters F 1 , F 2 , F 3 , F 4 , and F 5  may be provided to system  100 . In addition, valves V 1 , V 2 , V 3 , V 4 , V 5 , and V 6  direct the flow of gasses and/or fluids within system  100 . Controller  180  controls the operation of valves V 1 , V 2 , V 3 , V 4 , V 5 , and V 6 , ionization chamber  130 , and scale  140 . For simplicity, the electrical connections between controller  180 , valves V 1 , V 2 , V 3 , V 4 , V 5 , and V 6 , ionization chamber  130 , and scale  140  are not shown. 
         [0026]    As shown in  FIG. 1 , system  100  includes tubing between tracer source  110 , vial  120 , buffer solution  150 , gas source  160 , and filling line  170 . In one embodiment, the tubing may be surgical tubing, including silicon tubing as specified by USP class VI or Pharm. Eur. III. In another embodiment, the tubing may be any smooth tubing. In one embodiment, the surgical tubing may be removeable and replaced as necessary and desired, such as for each new batch of tracer. 
         [0027]    Tracer source  110  may be a source of any radioactive tracer. For example, tracer source  110  may be a source of FDG (2-[ 18 F]-fluoro-2-deoxyglucose), any other 18F-based fluorinated tracer,  13 N ammonia,  11 C carbon-based tracers,  15 O water, etc. In one embodiment, tracer source  110  may be the output of a synthesizer. 
         [0028]    In one embodiment, bulk vial  120  may be a bespoke container made from polycarbonate (Makrolon Rx1805). 
         [0029]    Although system  100  is described as including bulk vial  120 , which may then be used to fill smaller vials, it should be recognized that smaller vials (not shown) may be used in place of bulk vial  120 . In one embodiment, these smaller vials may be sized for individual dosages. 
         [0030]    Ionization chamber  130  is used to measure the radioactivity of the material in bulk vial  120 . In one embodiment, ionization chamber may be QQQ-624, manufactured by Veenstra Instruments, The Netherlands. 
         [0031]    In one embodiment, ionization chamber  130  may also measure background radiation before bulk vial  120  is filled with the tracer in order to determine a baseline radioactivity. 
         [0032]    Scale  140  measures the weight of bulk vial  120  and/or the contents of bulk vial  120 . In one embodiment, scale  140  may have a maximum load of 1500 g, and manufactured by Tedea-Huntleigh. 
         [0033]    Buffer solution  150  may include any isotonic solution, i.e., a solution that has an equal amount of dissolved solute in it compared to the human blood. In one embodiment, a sodium chloride solution, may be used. In another embodiment, buffer solution  150  may be a phosphoric buffer solution. However, any injectable solution may be used to dilute the tracer. 
         [0034]    Gas source  160  may be a source for any inert gas. In one embodiment, gas source  160  may be a source of N 2 . 
         [0035]    Filling line  170  is used to fill individual vials  175  for transport of the solution to the patient. 
         [0036]    Filters F 1 , F 2 , F 3 , F 4 , and F 5  are provided in order to filter gas and liquid as they travel through system  100 . In one embodiment, polytetrafluoroethylene (PTFE) filters may be used to filter gasses. For example, filters F 2 , F 3  and F 4  may be PTFE filters. Other filters for filtering gasses may be used as necessary and desired. 
         [0037]    In one embodiment, polyethersulfone filters may be used to filter liquids. For example, filter F 1  may be filter type 65770, manufactured by Filtertek, and F 5  may be filter type SLGP 033RB manufactured by Milipore. Other filters for filtering liquids may be used as necessary and desired. 
         [0038]    As noted above, valves V 1 , V 2 , V 3 , V 4 , V 5 , and V 6  direct the flow of gasses and fluids within system  100 . In one embodiment, V 1 , V 2 , V 3 , V 4  and V 5  are pinch valves that pinch tubing in order to disrupt fluid or gas flow. An example of a suitable pinch valve is model S104 08 Z030A 24VDC, manufactured by Sirai. 
         [0039]    In one embodiment, V 6  may be a medical valve. An example of a suitable medical valve is Type 562416 manufactured by Elcam. Valve V 6  may be a three position valve, providing two directions of flow and an “off” position. 
         [0040]    Other valves may be used as necessary and/or desired. 
         [0041]    As noted above, controller  180  controls the operation of valves V 1 , V 2 , V 3 , V 4 , V 5 , and V 6 , ionization chamber  130 , and scale  140 . In one embodiment, controller  180  may be a microprocessor-driven controller. For example, a PLC, such as B&amp;R series 2003, manufactured by B&amp;R Industrieelektronik, Austria, may be used. 
         [0042]    In another embodiment, at least some of valves V 1 , V 2 , V 3 , V 4 , V 5 , and V 6  may be manually controlled. 
         [0043]    Referring to  FIG. 2 , a method for measurement of radioactivity concentration and total radioactivity of a radiopharmaceutical is disclosed. Although the method depicted in  FIG. 2  will be described in the context of the system of  FIG. 1 , it should be recognized that the method is not limited to use with such a system. 
         [0044]    In step  210 , initial measurements are made. In one embodiment, the weight of bulk vial  120  without the tracer solutions is determined. The background radiation level may also be measured in order to determine a radiation base noise level. 
         [0045]    In step  220 , the tracer is transferred from tracer source  110  into bulk vial  120 . In one embodiment, this may be achieved by opening valve V 1  and allowing gas pressure to force the tracer through filter F 1  into bulk vial  120 . 
         [0046]    In step  230 , the weight of bulk vial  120  may be monitored as the transfer proceeds. Once a desired weight is achieved and/or time has passed, valve V 1  is closed. 
         [0047]    In step  240 , radioactivity is measured. In one embodiment, this may be accomplished by using, for example, ionization chamber  130 . The radiation base noise level measured in step  210  may be subtracted from the measured radiation level to determine the radioactivity of the tracer solution. 
         [0048]    In step  250 , the weight necessary to achieve the desired radioactive concentration is determined. This weight may be determined by multiplying the desired activity concentration by the measured activity, and then subtracting from the result the weight of the tracer. 
         [0049]    In step  260 , the tracer is diluted to the desired radioactive concentration. In one embodiment, this may be achieved by pressurizing the bottle containing buffer solution  150  with a gas from gas source  160  by opening valve V 3 . Valve V 2  is then opened, and buffer solution is forced into bulk vial  120  through Filter F 2 . Once the predetermined weight is reached, V 2  and V 3  are closed. 
         [0050]    In step  270 , the diluted tracer solution may be mixed to achieve a homogenous concentration. In one embodiment, the mixing is achieved with gas bubbles. For example, valve V 5  may be opened, and valve V 6  may be biased to allow gas from gas source  160  to be transferred to bulk vial  120 . The resulting gas bubbles create a homogenous solution. 
         [0051]    Valve V 5  may be shut after the passage of a predetermined amount of time, or after a predetermined volume of gas has passed. 
         [0052]    In step  280 , an indication of the radioactivity, volume and radioactivity concentration may be provided. This may be provided visually via a display, or it may be provided on a label. Other information, including tracer identification, time and date of measurement, etc. may be provided. 
         [0053]    In step  290 , individual vials may be filled with an amount of radioactive tracer. In one embodiment, this may be achieved by opening valve V 4 , and biasing valve V 6  to allow the passage of fluid from bulk vial  120  to filling line  170 . Gas from gas source  160  forces the radioactive tracer to exit filling line  170  into individual vials  175 . 
         [0054]    After filling, the remaining radioactivity may be flushed with buffer solution with gas pressure, by opening valve V 3 , V 2  and V 6  and positioning the outlet of filter F 5 , or filing line  170 , over, for example, a sink. 
         [0055]    Other embodiments, uses, and advantages of the present invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. The specification and examples should be considered exemplary only.