Patent Publication Number: US-8524006-B2

Title: Target bodies and uses thereof in the production of radioisotope materials

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of U.S. patent application Ser. No. 12/518,645, filed Jun. 11, 2009, which is a national stage application of PCT/US2007/025431, filed Dec. 11, 2007, which claims the benefit of U.S. Provisional Application No. 60/874,437 filed Dec. 11, 2006. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to radioisotope materials and, more specifically, to a system and method for efficiently producing radioisotope materials. 
     BACKGROUND 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     Production of radioisotopes can be achieved by accelerating charged or uncharged particles, via a particle accelerator, onto a target containing an enriched radioisotope starting material. Typically, such material includes high proportions of a nonradioactive material, which may at least partially transmute into radioactive material when the nonradioactive material is irradiated with energetic particles (e.g., protons or neutrons). White colliding with the target having the nonradioactive starting material deposited thereon, the charged particles (e.g., protons) interact with nuclei of the enriched radioisotope starting material to induce nuclear reactions within the radioisotope starting material, thereby producing the desired radioisotope. Unfortunately, during bombardment of the target, accelerated protons may also interact with the target&#39;s base material disposed adjacent to the starting material, thereby producing radioisotopes that may exhibit a relatively long decay time or half-life, which is the amount of time it takes a radioactive material to decay half its initial amount. As a result, the long half-life radioisotopes of the base material tend to prevent immediate reclamation of the nonradioactive portion of the starting material. Consequently, a substantial period of time, in some cases up to six months or more, may elapse before the level of radiation decreases to a safe level, permitting reclamation of the source nonradioactive portion of the starting material. During this time, the highly radioactive materials are generally stored in special areas, which may significantly increase the cost of producing radioisotopes. 
     SUMMARY 
     Certain exemplary aspects of the invention are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below. 
     A system and method are provided for reclaiming an enriched radioisotope starting material from a target body bombarded with energetic charged particles. The system and method enable an operator to reclaim the starting material in a relatively short time (e.g., several hours) after the target body&#39;s bombardment, greatly simplifying the target body&#39;s chemical processing, as well as reducing the cost of such processing (e.g., reducing the need for costly long-term storage). Specifically, in some embodiments, a chemical protective layer is disposed between a radioisotope starting material and a base material of the target body. After the target body is irradiated with a suitable source (e.g., particle accelerator), then the irradiated radioisotope starting material can be removed without removing the base material due to the protection provided by the chemical protective layer. For example, the chemical protective layer may be chemically resistant to a chemical used to remove the irradiated radioisotope starting material. The system and method may enable the operator to obtain three different radioisotopes in a single bombardment of the target body, further reducing cost of radioisotope production. For example, the irradiated radioisotope starting material may be removed via a first chemical that generally does not react with the chemical protective layer, the chemical protective layer may be subsequently removed via a second chemical that generally does not react with the base material, and then the base material may be subsequently removed via a third chemical. 
     A first aspect of the invention is directed to a target body having a radioisotope starting material (e.g., thallium 203) that, when bombarded with energetic particles, yields radioisotopes from which radiopharmaceuticals may be derived. The radioisotope starting material is disposed over a chemical protective layer (e.g., chromium having a rough or matte finish), which in turn, is disposed over a base layer (e.g., copper or aluminum) of the target body. The target body may be coupled (e.g., connected directly or indirectly) to a coolant system (e.g., a circulating fluid coolant such as water) adapted to remove heat from the target body while it is irradiated with energetic particles. 
     A second aspect of the invention is directed to a target body for use in the production of radioisotopes. This target body includes a base, a protective layer disposed on the base, and a radioisotope starting material disposed on the protective layer. The base, the protective layer, and the starting material are oriented such that the protective layer is disposed between the base and the radioisotope starting material. Further, the base of this target body includes a coolant path. 
     Yet a third aspect of the invention is directed to a method for producing a target body having a protective layer disposed thereon. The protective layer (e.g., a layer of chromium) may be electroplated onto the base layer of the target body. Electroplating of the chromium onto a base layer of the target body may be performed so that the chromium attains a surface which has a rough texture. In other words, the surface may appear dull and feel relatively rough, rather than a shiny appearance and smooth feel. The rough texture of the chromium&#39;s surface provides a surface morphology suitable for retaining a radioisotope starting material. For example, the surface morphology may be achieved by a relatively prolonged electroplating process (e.g., 30 minutes rather than 5 minutes). 
     Still a fourth aspect of the invention is directed to a method for producing a target body for use in the production of a radioisotope. In this method, a protective layer (e.g., a layer of chromium) is electroplated onto a base of the target body. Thereafter, a radioisotope starting material (e.g., thallium 203) is deposited onto the protective layer such that the protective layer is located between the base and the radioisotope starting material. 
     Yet a fifth aspect of the invention is directed to a method for removing a material from an irradiated target body. In this aspect, a first layer containing a first radioisotope material is chemically stripped from the irradiated target body. Removal of a second layer of the target body is substantially hindered or prevented using a third layer of the target body. This third layer of the target body is located between the first layer and the second layer prior to the first layer being chemically stripped from the irradiated target body. 
     Still yet a sixth aspect of the invention is directed to a method of producing a radioisotope. In this method, energetic particles are bombarded onto a starting material that is deposited on a chemical protective layer of a target body to generate a radioisotope of the starting material. 
     In yet a seventh aspect, the invention is directed to a system for producing radioisotopes. This system includes a particle accelerator, a target body, and a control system coupled to the particle accelerator. The target body of this seventh aspect includes a base, a protective layer disposed on a surface of the base, and a radioisotope starting material disposed on the protective layer. This protective layer is located between the base and the radioisotope starting material. Further, the protective layer includes chromium, tantalum, tungsten, gold, niobium, aluminum, zirconium, or platinum, or a combination thereof. 
     Various refinements exist of the features noted above in relation to the various aspects of the present invention. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present invention alone or in any combination. Again, the brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of the present invention without limitation to the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Various features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying figures in which like characters represent like parts throughout the figures, wherein: 
         FIG. 1  is a block diagram of a particle accelerating system; 
         FIG. 2  is a diagram of a cyclotron; 
         FIG. 3  is a diagram of a linear particle accelerator; 
         FIG. 4  is a cut-away, cross-sectional view of a target body; 
         FIGS. 5 and 6  are perspective views of a target body; 
         FIG. 7  is a flow chart of a method for preparing a target body; 
         FIG. 8  is a flow chart of a method for electroplating of a target body; 
         FIG. 9  is a flow chart of a method for producing radioisotopes; 
         FIG. 10  is a flow chart of a method for collecting multiple radioactive materials from a target body; 
         FIG. 11  is flow chart of a method for using medical imaging; and 
         FIG. 12  is a block diagram of an imaging system. 
     
    
    
     DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENTS 
     One or more specific embodiments of the present invention will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     When introducing elements of various embodiments of the present invention, the articles “as”, “an”, “the”, and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Moreover, the use of “top”, “bottom”, “above”, “below” and variations of these terms is made for convenience, but does not require any particular orientation of the components. As used herein, the term “coupled” refers to the condition of being directly or indirectly connected or in contact. 
     Turning now to the figures,  FIG. 1  is a block diagram of an exemplary particle accelerating system  10 . The system  10  includes a target body  12  having multiple layers, at least one of which is adapted for producing a radioisotope when that layer is irradiated with energetic charged particles. The target body  12  may include a layer  14 , including an enriched radioisotope starting material, which may produce a radioisotope when bombarded or irradiated with the energetic charged particles. In turn, the radioisotope may be used alone or in combination with other substances (e.g., tagging agents) as a radiopharmaceutical for medical diagnostic or therapeutic purposes. The layer  14  may include a radioisotope starting material, such as cadmium-112, or zinc-68, or thallium 203, or a combination thereof. For instance, in some embodiments, the layer  14  may include enriched thallium 203 from which radiopharmaceutical thallium 201 can be obtained and used in nuclear medicine. 
     The starting material that makes up the layer  14  may be disposed on a protective layer  16  having a matt-finish or rough surface configured to retain the starting material on the target body  12 . In other words, the surface of the protective layer  16  may appear dull and feel rough. The protective layer  16  is a chemical protection layer adapted to chemically shield base layer  18  while the target body  12  is chemically processed to obtain desired radiopharmaceuticals produced from irradiation of the target body  12 . The protective layer  16  may include chromium and/or other materials, such as iridium, tantalum, tungsten, gold, niobium, aluminum, zirconium, or platinum, or a combination thereof, that are inert to a chemical substance used when the layer  14  is chemically stripped-off the target body  12  after bombardment. That is, the layer  16  may generally prevent unwanted radioisotope byproducts having a long half-life contained within the base layer  18  from dissolving within the chemical stripping solution, such as nitric acid, which may contain radioisotopes produced from the layer  14 . In this manner, the protective layer  16  may ensure that only the desired radioisotopes are obtained via the chemical stripping procedure, such that the starting material may be reclaimed with ease in a relatively short amount of time. 
     The protective layer  16  may be deposited onto the base layer  18  via electroplating or other methods enabling formation of the layer  16  onto the base layer  18  without the use of any adhesive or intermediate layer. For example, the target body  12  may be electroplated for a relatively long duration of time (e.g., 15, 20, 25, 30, 45, 50, or more minutes) to increase the amount and roughness of the protective layer  16  on the base layer  18 . It has been found that a suitable rough layer  16  of chromium may be achieved by electroplating the base layer  18  for about 25-30 minutes, which is significantly greater than conventional electroplating of chromium (e.g., several minutes or less). It should be noted that the results (e.g., relatively thick, rough layer  16 ) of this prolonged electroplating of chromium is undesirable for other applications, which generally desire a smooth shiny layer of chromium. That being said, a unique result of the prolonged electroplating is an improved ability to adhere other materials onto the electroplated layer  16 . 
     The base layer  18  of the target body  12  may include a metal, such as copper, aluminum and/or other conductive material(s). For example, the base layer  18  may be molded out of aluminum and then coated with copper. Being conductive, the base layer  18  of the target body  12  may be adapted to transfer heat efficiently away from the target body  12  as temperature increases while the target body  12  is irradiated. 
     The particle accelerating system  10  includes a particle accelerator  20  configured to accelerate charged particles, as shown by line  22 . The charged particles  22  accelerate to attain enough energy to produce radioisotope material once the particles  22  collide with the target body  12 . Thus, the layer  14  may include a mixture of radioisotope and radioisotope starting material. Production of the radioisotope is facilitated through a nuclear reaction occurring once the accelerated particles  22  interact with the starting material of the layer  14 . For example, when producing radioisotope thallium 201, enriched thallium 203 may be irradiated with protons  22  accelerated via the accelerator  20 . The protons  22  may originate from a particle source  24  that injects the charged particles  22  into the accelerator  20  so that the particles  22  may be accelerated towards the target body  12 . 
     As the accelerated charged particles  22  collide with the target body  12 , a substantial amount of the particles&#39; kinetic energy may be absorbed by the target body  12 . Absorption of the energy imparted by the accelerated particles  22  may cause the target body  12  to heat up. To mitigate overheating of the target body  12 , the target body  12  may be coupled to a coolant system  26  disposed adjacent to the target body  12 . The coolant system  26  may include fluid connectors that are fluidly coupled to the target body  12  so that fluid, such as water, may circulate along or through the target body  12 , thereby removing heat absorbed by the target body  12  during irradiation of the same. In the illustrated embodiment, the coolant system  26  is shown as being separate from the target body  12  and disposed behind the target body  12 . In other embodiments, the cooling system  26  may be part of the target body  12 , or it may be disposed remote from the target body  12 . 
     The particle accelerating system  10  includes a control system  28  coupled to the particle accelerator  20 , the target body  12 , and/or the coolant system  26 . The control system  28  may be configured to, for example, control parameters, such as accelerating energy of the particles  22 , current magnitudes of the accelerated charged particles  22 , and other operational parameters relating to the operation and functionality of the accelerator  20 . The control system  28  may be coupled to the target body  12  to monitor, for example, the temperature of the target body  12 . The control system  28  may be coupled to the coolant system  26  to control temperature of the coolant and/or monitor and/or control flow rate. 
     Referring now to  FIG. 2 , another particle accelerator  40  is illustrated for use with the target body  12  having the protective layer  16 . The particle accelerator  40  may include a cyclotron used for accelerating charged particles, such as protons. The cyclotron  40  may employ a stationery magnetic field and an alternating electric field for accelerating charged particles. The cyclotron  40  may include two D-shaped hollow vacuum chambers  42 ,  44  separated by a certain distance. Disposed between the chambers  42 ,  44  is a particle source  46 . The particle source  46  emits charged particles  47  such that the particles&#39;  47  trajectories begin at a central region disposed between the hollow D-shaped vacuum chambers  42 ,  44 . A magnetic field  48  of constant direction and magnitude is generated throughout the chambers  42 ,  44  such that the magnetic field  48  may point inward or outward perpendicular to the plane of the chambers  42 ,  44 . Dots  48  depicted throughout the vacuum chambers  42 ,  44  represent the magnetic field pointing inwardly or outwardly from the plane of chambers  42 ,  44 . In other words, the D-shaped surfaces of the hollow vacuum chambers  42 ,  44  are disposed perpendicular to the direction of the magnetic field. 
     Each of the hollow vacuum chambers  42 ,  44  may be connected to a control  50  via connection points  52 ,  54 , respectively. The control  50  may regulate an alternating voltage supply, for example contained within the control  50 . The alternating voltage supply may be configured to create an alternating electric field in the region between the chambers  42 ,  44 , as denoted by arrows  56 . Accordingly, the frequency of the voltage signal provided by the voltage supply creates an oscillating electric field between the chambers  42 ,  44 . As the charged particles  47  are emitted from the particle source  46 , the particles  47  may become influenced by the electric field  56 , forcing the particle  47  to move in a particular direction, i.e., in a direction along or against the electric field, depending on whether the charge is positive or negative. As the charged particles  47  move about the chambers  42 ,  44 , the particles  47  may no longer be under the influence of the electric field. However, the particles  47  become may become influenced by the magnetic field pointing in a direction perpendicular to their velocity. At this point, the moving particles  47  may experience a Lorentz force causing the particles  47  to undergo uniform circular motion, as noted by the circular paths  47  of  FIG. 2 . Accordingly, every time the charged particles  47  pass the region between the chambers  42 ,  44 , the particles  47  experience an electric force caused by the alternating electric field, which increases the energy of the particles  47 . In this manner, repeated reversal of the electric field between the chambers  42 ,  44  in the region between the chambers  42 ,  44  during the brief period the particles  47  traverse therethrough causes the particles  47  to spiral outward towards the edges of the D-shaped chambers  42 ,  44 . 
     Eventually, the particles  47  may reach a critical radius such that their velocity may be too great for the particles  47  to sustain a circular path, causing them to shoot-off tangentially into the target body  12 . Energy gained while the particles  47  accelerate may be deposited into the target body  12  when the particles  47  collide with the target body  12 . Consequently, this may initiate nuclear reactions within the target body  12 , producing radioisotopes within the layers  14 - 18  of the target body  12 . The control  50  may be adapted to control the magnitude of the magnetic field  48  and the magnitude of the electric field  56 , thereby controlling the velocity and, hence, the energy of the charged particles as they collide with the target body  12 . The control  50  may also be coupled to the target  14  and/or the coolant system  26  to control parameters of the target  14  and/or the coolant system  26  as described above with respect to  FIG. 1 . 
       FIG. 3  illustrates a linear particle accelerator  70  for use with the target body  12  having the protective layer  16 . The linear accelerator  70  may include a long hollow tube formed of a conducting material such as copper or aluminum. Disposed within the tube  72  are small hollow tubes  74   a - 74   d , formed of a conducting material. The hollow tube  72  of the linear accelerator  70  may be coupled to a radio frequency (RF) generator  76  having an electrode configured to emit a RF signal of particular frequencies to propagate within the tube  72 . The RF generator  76  is further coupled to control  78  adapted to control operational parameters, such as RF frequencies and other functionalities of the linear accelerator  70 . 
     Electromagnetic waves generated by the RF generator  76  propagate within the hollow tube  72  causing charged particles  80  originating from the particle source  82  to accelerate when the particles  80  are subjected to an electric field propagating down the tube  72 . This electric field accelerates the particles  80  further down the tubes  72  as the particles  80  gain kinetic energy. The charged particles  80  are also guided through hollow tubes  74   a - 74   d , such as those shown by  FIG. 3 , to ensure a linear path of the particles  80 . As depicted by  FIG. 3 , the lengths of the hollow tubes  74   a - 74   d  increase down the length of the hollow tube  72  as the velocity of the particles  80  increases. In this manner, the charged particles  80  may be optimally accelerated in accordance with the RF frequency produced by the RF generator  76 . 
     Control  78  may be connected to the hollow tube  72 , the RF generator  76 , the target body  12 , and/or the coolant system  26 . The control  78  may control the frequency of the RF generator  76 , thereby controlling the acceleration of the charged particles  80  as the charged particles  80  propagate along the hollow tube  74   a - 74   d . Control  78  may be coupled to the target body  12  to monitor parameters, such as temperature, and other related feedback pertaining to the accelerator  70  and the target body  12 . 
       FIG. 4  is a partial cross-sectional view of an embodiment of the target body  12 . The target body  12  may include a starting material  14 , such as enriched thallium 203, cadmium-112, zinc-68 or other types of source materials, disposed on a chromium layer  16 . The protective chromium layer  16  is disposed on a target base layer  18 . The chromium layer  16  can be disposed on the base layer  18  via an electroplating process. Again, the electroplating process may be prolonged relative to conventional electroplating of chromium (e.g., 30 minutes rather than several minutes or less), such that a desired thickness is achieved to protect the base layer  18  and a desired roughness is achieved to secure the starting material  14  to the chromium layer  16 . Other materials such as tantalum, tungsten, gold, niobium, aluminum, zirconium, or platinum, or a combination thereof, may be disposed on the base layer  18  via the electroplating process. 
     Electroplating the chromium layer  16  onto the base layer  18  may involve certain steps for ensuring that the chromium layer  16  has attributes suitable to support the starting material  14  and produce a radioisotope. Such attributes may include chromium layer thickness and surface texture. The process of electroplating chromium onto the target body  12  may include buffing and/or polishing portions of the target body  12  designated for chromium electroplating. Portions of the target body  12  not designated for chromium electroplating may be coated with certain protective coats that may prevent the electroplating of the chromium to those portions of the target body  12 . Thereafter, the target body  12  may be immersed in a tank or vessel containing a solution of chromium and other associated materials contributing to the electroplating process. The target body  12  may be immersed in the tank until a desired chromium thickness is electroplated onto the target base layer  18 . In some embodiments, the target body  12  may be electroplated for an amount of time extending between 25-45 minutes. During the electroplating process the electroplating tank may be maintained at approximately 125 degrees. 
     After a desired thickness of chromium is electroplated onto the base layer  18 , the target body  12  may be removed from the chromium tank and inspected to verify that the thickness and other attributes of the chromium layer are suitable to support the starting material  14 . For example, the difference in weight of the target body  12  before and after the electroplating process may be measured and a chromium thickness may be obtained. Further, as previously mentioned, it may be desirable to obtain a chromium layer with a rough surface morphology adapted to retain the radioisotope source material while the target body  12  is irradiated. That is, the surface of the chromium layer  16  may have roughness and granularity suitable for maintaining, for example, thallium 203 onto the target body  12  during its bombardment by charged particles. Thus, after the target body  12  is electroplated, the chromium disposed thereon is not polished in any manner so that the surface of the chromium layer  16  retains its roughness. Such surface roughness characteristics of the chromium layer  16  may be inspected via an electron microscope and/or via its ability to retain water for certain periods of time. 
     The base layer  18  of the target body  12  may include or be substantially consist of a metallic material such as copper, aluminum, or other conductive materials or combinations thereof. In some embodiments, the base layer  18  may be an aluminum structure coated with copper. As further depicted by  FIG. 4 , a coolant passage  90  may be formed as part of a channel or groove lengthwise along the target body  12 . The coolant channel  90  facilitates fluid flow along the target body  12  so that heat may be removed from the target body  12  while the target body  12  is irradiated with charged particles. 
     During bombardment of the target body  12 , nuclear interactions between the colliding charged particles and atomic nuclei of materials of the target body  12  may transform a portion of those nuclei into radioisotopes. For example, after bombardment, the layer  14  may include a combination of enriched thallium 203 and radioisotope lead 201. The lead 201 may subsequently decay into thallium 201, which is a desired radioisotope for use in nuclear medicine. Similarly, some atomic nuclei of the chromium layer  16  and the base layer  18  may transform into radioisotope nuclei from which other desired radiopharmaceuticals may be yielded. 
     Extracting the desired radiopharmaceuticals from the target body  12  may involve chemical processing of the target body  12 . The chemical processing of the target body  12  may be adapted to remove certain layers of the target body  12  while keeping others intact. After bombardment, for example, the thallium 203 and the lead 201 may be stripped from the target body  12  using hot nitric acid, which is configured to remove those substances but not the chromium layer  16 . That is, the radioisotope starting material, such as thallium 203, may be susceptible to removal by chemicals that may cause the thallium 203 to strip from the target body  12 , whereas the chromium layer  16  may be chemically inert or resistant to removal by such stripping chemicals and, therefore, may not strip from the target body  12 . Thus, the chromium layer  16  shields the base layer  18  from the nitric acid-stripping, thereby generally preventing or reducing the likelihood of radioisotope metals with a long half-life disposed in the base layer  18  from dissolving into the solution containing the thallium 203 and the lead 201. In this manner, further chemical processing of the solution containing the thallium 203 and the lead 201 may proceed in a relatively short amount of time after bombardment so that the aforementioned substances are separated. The solution containing the thallium 203 and the lead 201 can be processed to further chemically separate the lead 201, leaving behind a solution containing thallium 203, which can be reclaimed and, thus, reused for producing additional thallium 201 for radiopharmaceuticals. In this manner, it may be possible to reclaim the thallium 203 quite quickly (e.g., several hours or days) from the chemical solution, thereby generally avoiding expensive storage (e.g., for several months or even years) of the chemical solution containing the thallium 203 and 201 until radiation levels produced from other radioisotope metals subsides. 
     After the layer  14  containing the thallium 203 and the lead 201 is removed from the target body  12 , the target body  12  may further be chemically processed to remove the chromium layer  16 , from which chromium 51 may be derived. The chromium 51 may be used as a radiopharmaceutical, particularly, for tagging red blood cells. The chromium 51 may be removed from the target body  12  using hydrochloric acid, which does not react with metals of the base layer  18  of the target body  12 . Using hydrochloric acid may prevent radioisotope metals produced from the base layer  18  (i.e., during bombardment of the target body  12 ) from dissolving into the solution containing the chromium 51. In this manner, a single bombardment of the target body  12  may yield two radiopharmaceuticals, i.e., thallium 201 from the layer  14  and chromium 51 from the layer  16 . Because operational costs of particle accelerators used for bombarding targets to produce radiopharmaceuticals can be relatively high, producing two radioisotopes at the price of one target irradiation may significantly improve cost effectiveness of producing radiopharmaceuticals. As discussed further below, a single irradiation of the target may further produce a third radiopharmaceutical obtainable from radioisotopes produces by the base layer  18  of the target body  12 . 
       FIG. 5  illustrates a perspective view of another target body  100  having the protective layer  16 . The target body  100  may be similar to the target body  12  discussed with reference to  FIGS. 1-4 . Accordingly, the target body  100  includes the layers  14 ,  16  and  18  similar to those layers discussed with reference to the target body  12 . The target body  100  is shown as including a hollow chamber  101  having tubular openings  102 ,  104 . The tubular openings  102  and  104  extend from the back surface of the target body  100  downward into the target&#39;s base material  18 . The tubular openings  102 ,  104  may be connected internally within the base layer  18  such that a channel is formed between the two tubular openings  102 ,  104 . 
     The tubular openings  102 ,  104  may be coupled to an external cooling source, such as the coolant source  26  shown in  FIG. 1 , which may be configured to supply a coolant such as water to the target body  100 . Using external tubes coupled to the openings  102 ,  104 , the coolant may enter through opening  102  into a channel disposed therebetween and exit the target body  100  via opening  104  back to the coolant source. Grooves  106  disposed on the inner side of the base layer  18  are configured to increase the surface area of the target body  100 , thereby improving heat transfer from the target to the coolant as the target body  100  heats while the target it is irradiated. 
       FIG. 6  is a perspective view of another target body  120  having the protective layer  16 . The target body  120  is similar to the target body  12  discussed with reference to  FIGS. 1-4 . Particularly,  FIG. 6  depicts a back side perspective view of the target body  120 . In the illustrated embodiment, the target body  120  includes the source layer  14  disposed adjacent to the protective layer  16 , such as chromium electroplated to the target&#39;s base material  18 . Further, the target body  120  may include grooves  122 - 128  forming linear and circular channels on the backside of the target body  120 . The grooves  122 - 128  may extend substantially into the target&#39;s base  18 , thereby effectively increasing the surface area of the backside of the target body  120 . In other embodiments, the grooves  122 - 128  may form other shapes and geometries and/or may have varying depths. The backside of the target body  120  may be coupleable to a coolant source, such as the coolant source  26  discussed herein with reference to  FIG. 1 . The coolant source  26  may supply a coolant to the backside of the target body  120  so that coolant may flow through the grooves or channels  122 - 128 , removing excessive heat from the target body  120  as it heats up while the target is irradiated. Moreover, the channel  122  may form a seal with a portion of the coolant source  26 . 
       FIG. 7  is a flow chart  140  illustrating a process for producing a target (e.g.,  12 ) having a protective layer. The method begins at block  142  where a base material, such as the base material  18  shown in  FIG. 1 , is produced. The material of the base layer  18  may include a metallic substance, such as copper or aluminum or combinations thereof. Thereafter, the method proceeds to block  144  where a protective layer, such the chromium layer  16  shown in  FIG. 1 , may be disposed on the base layer  18 . The protective layer  16  may be adapted to chemically shield the base material  18  from certain chemicals once the target body  12  is chemically processed and the layer  14  is removed from the target body  12 . 
     The protective layer  16 , such as the chromium layer, can be electroplated on the base layer  18  to a certain thickness and roughness. For example, the electroplating process may be significantly extended (e.g., 20-50 minutes rather than several minutes or less) to increase the thickness and create a rough or a matt-finished surface. Thereafter, the method proceeds to block  146  where a source or starting material layer, such as the thallium 203 layer  14  may be disposed on the protective layer  16 . 
       FIG. 8  is a flow chart  150  illustrating an electroplating process. The process begins at block  151  whereby portions of the base layer  18  of the target body  12  designated for electroplating may be buffed or polished prior to being electroplated. Thereafter, in step  152 , portions of the base layer  18  not designated for electroplating may be coated with a coating material adapted to prevent those areas or portions from being electroplated. Thereafter, the method proceeds to block  153  where the target body  12  may be immersed in a tank containing a chromium solution. The tank may be coupled to a power supply providing sufficient current to enable the electroplating process. The chromium solution in the tank may be kept at a temperature of approximately 125 degrees Fahrenheit as the target body  12  is electroplated for an amount of time ranging between 20-50 minutes. Next, the method proceeds to step  154  where the target body  12  may be removed from the tank. Thereafter, the method proceeds to step  155 , whereby the surface of the newly formed electroplated chromium layer  16  may be inspected to verify that it has the desired texture and surface morphological characteristics. Such characteristics may adapt the surface of the chromium layer  16  to retain the layer  14 . 
       FIG. 9  is a flow chart  160  of a process for producing radioisotopes from a radioisotope starting material. The process  160  provides a method for reclaiming the starting material  14  with relative ease in a short period of time (e.g., several hours or days rather than several months or years) after the irradiation of the target body  12  by energetic particles. The process begins at block  162  whereby a source or a starting material (e.g., thallium 203) may be disposed on the target body  12  over the protective layer  16 . In other embodiments, the starting material may include other types of substances from which radiopharmaceuticals may be produced. Once the starting material  14  is disposed on the target body  12 , the process may proceed to block  164  during which the target body  12  may be irradiated with charged particles. Thereafter, the process may proceed to block  166  whereby irradiation of the source layer  14  may initiate nuclear reactions transforming portions thereof into a radioisotope that may be used as a radiopharmaceutical. For example, bombardment of thallium 203 with energetic protons may yield radioisotope lead 201. Although lead 201 may not be the final product used as a radiopharmaceutical, its subsequent nuclear decay may produce a radiopharmaceutical, namely, thallium 201. 
     The method then may proceed to block  168  whereby the layer  14  containing the source material and the newly formed radioisotope material may be removed from the target body  12  ( FIG. 1 ). For example, stripping-off lead 201 and thallium 203 disposed on the target body  12  after irradiation may be achieved by using a hot nitric acid solution. The hot nitric acid solution may dissolve the layer  14  without affecting the chromium protective layer  16 . Thereafter, the process may proceed to block  170  where the radioisotope material and the starting material may be chemically separated. For example, the lead 201 may be separated from the starting thallium 203 by a variety of suitable chemical methods. After removing the lead 201 from the original solution, the thallium 203 is left behind. Accordingly, the method may proceed to block  172  where the starting material, such as the thallium 203, may be reclaimed for reuse. In this manner, the thallium 203 can be reclaimed and reused quite quickly (e.g., several hours or days) after the target body  12  is irradiated. Hence, the process  160  provides a significant improvement over previous methods, which would allow reclaiming the thallium 203 only after a substantial period of time, which may be as long as six months or greater. 
       FIG. 10  illustrates a flow chart  190  of a process for removing and separating radioisotopes from a target, such as the target body  12  of  FIG. 1 , after the target is bombarded with energetic charged particles. The method begins at block  192  when a layer  14  containing radioisotope starting material and radioisotope material are disposed on a target. A protective layer, such as the chromium protective layer  16 , may be disposed underneath the starting material  14  and may also include radioisotopes resulting from the irradiation of the target body  12 . Accordingly, the process may proceed to block  194  during which the radioisotope and the starting material may be removed from the target body  12  via chemical processing, such as the chemical processing mentioned above with reference to the process  160  of  FIG. 9 . Again, such chemical processing may be adapted to chemically react and, thus, remove only the radioisotope and the starting materials  14  disposed on the target body  12 , while not reacting with the underlying protective chromium layer  16 . The protective chromium layer  16  is adapted to shield the underlying base layer  18  of the target body  12  so that radioisotope materials produced from the base layer  18  may not dissolve or become part of a solution containing the desired radioisotope material and the starting material  14 . By generally preventing radioisotope material originating from the base layer  18  of the target body  12  to mix with the desired radioisotope material, a more efficient and quick recovery of the source radioisotope material may be possible. 
     Hence, once the radioisotope and the starting material are both removed or stripped from the target body  12 , the method may proceed to block  196  where the radioisotope material and the radioisotope starting materials are separated and collected for use. The method then proceeds to block  198  where the protective chromium layer  16 , including radioisotopes produced therefrom, may be stripped-off the target  14 . In this manner, a second radioisotope bi-product, which can also be used as a radiopharmaceutical, is obtained from the protective chromium layer  16 . The removal of the protective chromium layer  16  from the target  14  may be achieved using specific chemicals designed to remove the chromium layer  16  while being chemically inert to the materials from which the base layer  18  of the target are made. This generally prevents radioisotopes having long half-lives contained within the base layer  18  of the target from dissolving in a solution containing radioisotopes derived from the protective chromium protective layer  16 . In certain embodiments, chromium 51 may be produced in the chromium layer  16  as a byproduct when the target  14  is irradiated, and can be removed from the target  14  using hydrochloric acid which may not interact with metals contained in the base layer  18  of the target. Again, this enables claiming the chromium 51 radioisotope without having to wait for prolonged periods of time to allow radiation levels produced from long half-life radioisotopes within the base layer  18  to decay to an acceptable level. 
     Thereafter, the method may proceed to step  200  whereby the base material or portions thereof may be stripped-off to produce a third radioisotope, such as copper which may in turn subsequently decay into usable radiopharmaceuticals. Thus, the method  190  may enable the production of three radiopharmaceuticals from a target in a single irradiation. This significantly improves the cost-effectiveness of producing radioisotopes from which radiopharmaceuticals may be obtained. 
       FIG. 11  is a flowchart  210  illustrating an exemplary nuclear medicine process utilizing one or more radiopharmaceuticals described herein and as illustrated with reference to  FIGS. 1-10 . As illustrated, the process  210  begins by providing a radioisotope isotope for nuclear medicine at block  212 . For example, block  212  may include generating thallium 201 or another radioisotope from a target body  12  having the protective layer  16  as described above. At block  214 , the process  210  proceeds by providing a tagging agent (e.g., an epitope or other appropriate biological directing moiety) adapted to target the radioisotope for a specific portion, e.g., an organ, of a patient. At block  216 , the process  210  then proceeds by combining the radioisotope isotope with the tagging agent to provide a radiopharmaceutical for nuclear medicine. In certain embodiments, the radioisotope isotope may have natural tendencies to concentrate toward a particular organ or tissue and, thus, the radioisotope isotope may be characterized as a radiopharmaceutical without adding any supplemental tagging agent. At block  218 , the process  210  then may proceed by extracting one or more doses of the radiopharmaceutical into a syringe or another container, such as a container suitable for administering the radiopharmaceutical to a patient in a nuclear medicine facility or hospital. At block  220 , the process  210  proceeds by injecting or generally administering a dose of the radiopharmaceutical and one or more supplemental fluids into a patient. After a pre-selected time, the process  210  proceeds by detecting/imaging the radiopharmaceutical tagged to the patient&#39;s organ or tissue (block  222 ). For example, block  222  may include using a gamma camera or other radiographic imaging device to detect the radiopharmaceutical disposed on or in or bound to tissue of a brain, a heart, a liver, a tumor, a cancerous tissue, or various other organs or diseased tissue. 
     Referring to  FIG. 12 , an imaging system  240  that may use the radiopharmaceuticals acquired by the techniques of  FIGS. 1-11  may include an imaging device  242 , a system control  244 , data acquisition and processing circuitry  246 , a processor  248 , a user interface  250 , and a network  252 . Specifically, the imaging device  242  is configured to obtain signals representative of an image a subject after a radiopharmaceutical has been administered to the subject. The imaging system  240  may include a positron emission tomography (PET) system, a single photon emission computer tomography system, a nuclear medicine gamma ray camera, or another suitable imaging modality. Image data indicative of regions of interest in a subject may be created by the imaging device  242  either in a conventional support, such as photographic film, or in a digital medium. 
     The system control  244  may include a wide range of circuits, such as radiation source control circuits, timing circuits, circuits for coordinating data acquisition in conjunction with patient or table of movements, circuits for controlling the position of radiation detectors, and so forth. The imaging device  242 , following acquisition of the image data or signals, may process the signals, such as for conversion to digital values, and forward the image data to data acquisition circuitry  246 . In the case of analog media, such as photographic film, the data acquisition system may generally include supports for the film, as well as equipment for developing the film and producing hard copies that may be subsequently digitized. For digital systems, the data acquisition circuitry  246  may perform a wide range of initial processing functions, such as adjustment of digital dynamic ranges, smoothing or sharpening of data, as well as compiling of data streams and files, where desired. The data is then transferred to a processor  248  where additional processing and analysis is performed. For conventional media such as photographic film, the processor  248  may apply textual information to films, as well as attach certain notes or patient-identifying information. In a digital imaging system, the data processing circuitry performs substantial analyses of data, ordering of data, sharpening, smoothing, feature recognition, and so forth. 
     Ultimately, the image data is forwarded to an operator/user interface  250  for viewing and analysis. While operations may be performed on the image data prior to viewing, the operator interface  250  is at some point useful for viewing reconstructed images based upon the image data collected. In the case of photographic film, images may be posted on light boxes or similar displays to permit radiologists and attending physicians to more easily read and annotate image sequences. The image data can also be transferred to remote locations, such as via a network  252 . In addition, the operator interface  250  may enable control of the imaging system, e.g., by interfacing with the system control  244 . 
     While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.