Phosphorylated polyazamacrocyclic compounds for complexation of metal ions
This is a divisional of application Ser. No. 07/923,715 filed Jul. 31, 1992 and issued Nov. 8, 1994 as U.S. Pat. No. 5,362,476 which is a continuation-in-part of U.S. Ser. No. 07/615,619 filed Nov. 19, 1990, issued as U.S. Pat. No. 5,342,60 which is a continuation-in-part of U.S. Ser. No. 07/357,193 filed May 25, 1989 now abandoned, and U.S. Ser. No. 07/291,053 filed Dec.28, 1988, the latter now issued as U.S. Pat. No. 4,983,376 which is a continuation-in-part of application Ser. No. 07/007,729 filed on Jan. 27, 1987, (abandoned) which was a continuation-in-part of application Ser. No. 06/662,075, filed on Oct. 18, 1984, now issued as U.S. Pat. No. 4,639,365. All of the above applications are incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to compositions and methods for enhancing contrast in imaging internal structures and functions of living subjects. 
     2. Imaging Modalities 
     Imaging of internal structures and functions of living subjects may be accomplished by applying electromagnetic radiation from external sources (as in conventional x-rays and computerized axial tomography) or internal sources (as in PET or positron emission tomography and radionuclide scans). Use of ionizing radiation is avoided in imaging with nuclear magnetic resonance (NMR) and untrasonography, making these methods advantageous for many applications. 
     Whatever the imaging modality, consideration is given to means of increasing image contrast through localization of contrast agents in the region to be imaged. Such agents are frequently metals which emit, absorb, or scatter energy or, as in the case with NMR agents, increase the image signal strength locally. For best effect, agents must be localized. This may be accomplished, for example, by direct injection of contrast agent (as in myelograms or retrograde urethrograms), through metabolic uptake of an agent (as in PET), and by conjugation of contrast agents with monoclonal antibodies which tend to accumulate in certain tissues. The latter process in particular has been used in NMR image enhancement with chelated metal ions. Though well known, the process has several shortcomings: 
     1 preparation of the antibody is complex; 
     2 diminished immunoreactivity of the antibody occurs following conjugation; 
     3 there is limited uptake of the conjugate by the target tissue; and 
     4 there may be unfavorable interactions between the chelated ion and the antibody. 
     Because of the advantages of NMR imaging (good resolution and avoidance of ionizing radiation), an NMR contrast agent capable of greater localization would be clinically important. Such an agent would offer significant advantages over contrast agents of the prior art. 
     3. NMR Contrast Agents 
     The quality of the images obtained from an NMR scan is based on two properties: the proton densities of the various tissues and differences in proton relaxation rates. The proton density of tissues cannot be readily altered. Proton relaxation rates can be adjusted by adding a paramagnetic relaxation agent, more commonly known as a &#34;contrast agent.&#34; Contrast agents enhance the contrast in NMR images between magnetically similar but histologically dissimilar tissues. 
     Gadolinium, which has strong paramagnetic properties because of its seven unpaired electrons, has been tested as a contrast agent. It has a large magnetic moment which efficiently relaxes magnetic nuclei and increases tissue contrast in the region of the gadolinium. 
     One drawback of gadolinium as a contrast agent is its toxicity to animals, although a possible remedy for this problem is incorporation of gadolinium in a compound that would pass through the body and be excreted without releasing toxic gadolinium ions. Unfortunately, the rare earth elements (including gadolinium) do not form stable covalent bonds with organic molecules, so such molecules can decompose in vivo and release the toxic ions. 
     Thus, there is a need for effective contrast agents which avoid the toxicity problems inherent in using gadolinium or another metal ion. Further, it is desirable that a contrast agent control or influence the distribution of chelated ions in the body. 
     A even more desirable approach to the site-specific delivery of metal ions would be through use of stable chelates having inherent affinity for various tissue types. Inherent tissue affinity built into the organic chelating agent through modifications in both ionic charge and degree of lipophilic character would offer substantial advantages over currently available agents. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a series of new phosphorous-containing triaza- and tetraazamacrocyclic chelators which have inherent affinity for certain tissues. Following intravascular injection, chelates comprising these compositions preferentially accumulate in certain tissues, depending on the time after injection. In particular, 1,4,7,10 tetraazacyclododecane-1,4,7,10-tetra(methylenephosphonate monobutyl ester) has a high affinity for liver tissue and the gastrointestinal tract (in that order). Chelates comprising this agent are thus suitable for liver imaging because of the lipophilic character imparted by the ester functionality. Such agents are not metabolized, and eventually pass out of the body via the urine or feces. 
     While the monobutyl ester above appears well adapted for liver imaging, analogous alkyl esters have also been considered. Monopentyl esters are nearly as good for liver imaging, but monooctyl esters have the disadvantage of very low aqueous solubility. Monopropyl esters, on the other hand, may be used for liver imaging but are less efficient because a substantial portion of the agent is rapidly lost to the kidneys; monoisopropyl esters would behave similarly. Hence, the most preferred embodiment is that described above with monobutyl esters. 
     For use with NMR, compositions of the present invention must be chelated with a metallic element. While the element is preferably of the rare-earth series (preferably gadolinium), those skilled in the art will recognize that other metallic ions might also be useful for imaging. For example, other metal chelates (e.g., chelates of radionuclides or heavy metals) may be used for imaging by scintigraphy, x-radiation, and analogous imaging methods where changes in local tissue parameters can increase image contrast. Depending on the metal ion preferred for a particular contrast agent application, either triaza- or tetraaza- compounds of the present invention may be selected as chelators. 
     Chelators of the present invention have the formula ##STR3## where x is 2, 3 or a combination of p 2(s) and q 3(s) where p+q=y; 
     y is 3 or 4; 
     R is (CH 2 ) z  P(═0)OR 1  OR 2  ; 
     R 1  is H or CH 3;   
     R 2  is butyl, pentyl or hexyl; and 
     z is 1 to 3. 
     In one important embodiment, this compound may be complexed with a metal to be a polyazamacrocyclic compound-metal complex having the formula ##STR4## where x is 2, 3 or a combination of p 2(s) and q 3(s) where p+q ═y; 
     y is 3 or4; 
     R is (CH 2 ) z  P(═O)OR 1  OR 2  ; 
     R 1  is H or CH 3;   
     R 2  is butyl, pentyl or hexyl; 
     z is 1 to 3; 
     r is 2 or 3; and 
     M is a metal ion. 
     The y designation characterizes the compound as triazamacrocyclic or tetraazamacrocyclic. The x is preferably 2, although 3 is feasible under many circumstances. Combinations of p 2(s) and q 3(s) for x are of course readily produced but the total of p+q must be y for the number of units in the polyaza macrocycle. H or CH 3  for R 1  are believed equivalent in use. 
     In a preferred embodiment of either the compound or its metal complex y is 3, p is 1 and q is 2 or p is 2 and q is 1. 
     In another preferred embodiment of the compound or its metal complex, y is 4, p is 1 and q is 3, p is 2 and q is 2 or p is 3 and q is 1 and z is most preferably 1. n is preferably 2. 
     In a more preferred embodiment x is 2, y is 4, z is 1, R 1  is H and R 2  is butyl. 
     In another preferred embodiment X is 2, y is 3, z is 1, R 1  is H and R 2  is butyl. 
     The M +r  is preferably a paramagnetic lanthanide, although other divalent or trivalent metal ions, including radionuclides and heavy metals, may also be so complexed. 
     In one important application, the present invention involves a method for enhancing a magnetic resonance image of a subject. This method comprises administering to the subject a polyazamacrocyclic compound-metal complex having the formula ##STR5## where x is 2, 3 or a combination of p 2(s) and q 3(s) where p+q=y; 
     y is 3 or 4; 
     R is (CH 2 ) z  P(═O)OR 1  OR 2  ; 
     R 1  is H or CH 3;   
     R 2  is butyl, pentyl or hexyl; 
     z is 1 to 3; 
     r is 3; and 
     M is gadolinium. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 schematically illustrates the structure of NOTPME (where R is CH 2  CH 3  and R 1  is H). 
     FIG. 2 schematically illustrates the structure of DOTEP. 
     FIG. 3 schematically illustrates the structure of DOTPMB. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     EXAMPLE 1 
     Triazamacrocyclic Compounds 
     NOTPME Synthesis 
     Materials 
     1,4,7-triazacyclononane, paraformaldehyde, diethylphosphite, and activated carbon Darco G-60 were purchased from Aldrich Chemical Company. MgSO 4  was from Mallickrodt, sodium hydroxide, and benzene from J. T. Baker, and diethylether from Fisher Scientific. All chemicals were of highest purity and were used without further purification. Solutions of ZnCl 2 , GdCl 2 , MgCl 2  and Ca Cl 2  were standardized complexometrically. 
     Synthesis of NOTPME 
     1,4,7-Triazacyclononane (1.91 g, 14.71 mmol) and diethylphosphite (7.018 g, 16.94 mmol, 15% excess) were dissolved in 125 ml of benzene and heated to reflux. Anhydrous paraformaldehyde (1.727 g, 30% excess) was added in small portions to the above refluxing mixture while the benzene-water azeotropic mixture was removed by distillation- After the addition of paraformaldehyde was complete, the entire solution was boiled for 30 minutes and then evaporated to obtain a yellow viscous oil. The oil was dissolved in 150 ml anhydrous diethylether and dried with anhydrous MgSO 4  overnight. MgSO 4 , along with a white precipitate which formed, were filtered off and discarded. The filtrate was decolorized with activated carbon and filtered. The filtrate was evaporated in vacuum to obtain a viscous oil of 1,4,7-triazacyclononane-N,N&#39;,N&#34;-tris(methylenephosphonate diethylester) (NOTPDE). Pure NOTPDE was obtained in 96% yield (9.21 g, 14.17 mmol) and was used for the synthesis of NOTPME (structure shown in FIG. 1) without further purification.  1  H NMR data of NOTPDE in CDCl 3  (TMS at zero) are as follows: δ (ppm) : 1.33 (t, 18H, --CH 3 ), 2.97 (s, 12H, N--CH 2 ), 3.00 (d, 6H, P--CH 2 ), 4.13 (p, 12H, O--CH 2 ). 
     9.20 g of NOTPDE (14.15 mmol) was mixed with 2.50 g of NaOH in 9 ml H 2  O) and after 2 hours the entire reaction mixture was boiled until a clear solution was obtained (approximately 5 minutes). The solution was cooled to room temperature and was allowed to stand overnight. The crystals formed were filtered off from the viscous mother liquor using a pressure filter funnel with a coarse porosity grade filter disc. The crystals were washed once with cold absolute ethanol, three times with absolute ethanol-diethylether (1:1) mixture and finally with diethyl ether. The crystals of Na 3  NOTPME were dried in dry nitrogen stream at 25° C. for 2 hours. Traces of H 2  O and ethanol were removed upon vacuum drying (10 mm Hg) NOTPME for 5 hours at 50° C. Pure NOTPME thus obtained were white crystals, very hygroscopic, readily soluble in H 2  O and fairly soluble in chloroform. The yield of pure NOTPME was 40.8% (3.24 g, 5.77 mmol). 
       1  H NMR (D 2  O, HDO peak set as reference at 4.90 ppm), δ (ppm): 1.23 (t, 9H, --CH 3 ), 2.54 (s, broad, 6H, P--CH 2 ), 2.79 (s, broad, 12 H, N--CH 2 ), 3.91 (p, 6H, O--CH 2 ). 
     EXAMPLE 2 
     Tetraazamacrocyclic Compounds 
     DOTEP Synthesis 
     DOTEP, shown in FIG. 2, was prepared as follows. 2 ml of dichloroethylphosphine was slowly mixed with ice to form the corresponding ethylphosphinic acid. After warming to room temperature, 390 mg of 1,4,7,10-tetraazacyclododecane tetrahydrochloride (cyclen.4HCl) (Parrish Chem. Co., Ogden, Utah) was added and the mixture heated to boiling under a nitrogen atmosphere. A solution containing 157 mg of paraformaldehyde dissolved in 10 ml of 6M HCl was added at a rate of 0.5 ml/hr, while the mixture continued to reflux. The final mixture was refluxed an additional 4 hours then cooled to room temperature. This solution was concentrated under vacuum to a viscous oil, redissolved into 6 ml of water and loaded onto a DOWEX 50Wx4 (hydrogen form) cation exchange column (7.5 ml bed volume). The column was washed to neutrality with water and the product eluted with 60 ml of 0.66 M HCl. The fractions containing DOTEP were combined, evaporated, redissolved in absolute ethanol and evaporated to a white solid. This solid was dispersed into anhydrous ether, filtered off, pre-dried under nitrogen and dried under vacuum at 60°-70°C. to yield a white, very hygroscopic solid (360 mg, 44% yield). This solid was stored in sealed ampoules. Elemental analysis and potentiometry shows the solid to be DOTEP.2HCl. 
     EXAMPLE 3 
     Tetraazamacrocyclic Compounds 
     DOTP Dibutyl Ester Synthesis 
     Tetraaza-12-crown-4 4HCl (1 g, 3.14×10 -3  mol) was dissolved in water and the pH adjusted to 9.0 using 1M NaOH. The solvent was evaporated and the residue dried under vacuum for 1 hour. Formaldehyde (6.6 mL of 37% solution, 7.15 g, 0.24 mol) was added and the solution stirred for 30 minutes at room temperature. Dibutyl phosphite (5.10 mL of 96% purity, 0.025 mol) was then added and the reaction mixture stirred for 15 hours at room temperature (dipentyl and dihexyl phosphite are so used to produce dipentyl and dihexyl esters respectively). The resulting mixture consisted of two layers. The bottom layer was mostly excess formaldehyde, as indicated by  13  C NMR. The upper layer contained the product and excess phosphite. This layer was separated, concentrated and dried under vacuum for 1 hour. The resulting syrup was loaded onto a silica-gel column (2.5×11 cm). The excess phosphite was washed away with methylene chloride (250 mL). The product was eluted with 5% methanol in methylene chloride. 20 mL fractions were collected and monitored by TLC. The fractions containing the product were combined, concentrated, and dried under vacuum,. A pale yellow oil was obtained in 75% yield (2.34 g) .  1  H NMR (CDCl 3 ): 0.87 (t, J=7.3, 6H), 1.33 (m, J=7.3, 4H), 1.60 (p, J=7.3, 4H), 3.18 (br s, 4H), 3.39 (d, J=8.5, 2H), 4.03 (m, J=7.3, 6.1, 4H).  13  C NMR (CDCl 3 ): 11.3 (s), 16.5 (s), 30.3 (d, J=5.9), 47.3 (d, J=148), 50.0 (br s), 63.8 (d, J=7.3). 
     EXAMPLE 4 
     Tetraazamacrocyclic Compounds 
     DOTP Monobutyl Ester (DOTPMB) Synthesis 
     The dibutyl ester was suspended in 1M KOH (20 mL). The mixture was stirred at 85° C. for 17 hours and then at 106° C. for 9 hours. The solvent was evaporated and the sample dried under vacuum for 1 hour. Methylene chloride (40 mL) was then added and the remaining solid KOH crushed as much as possible. The solvent was again evaporated and this procedure repeated another two times. The solvent was evaporated and the residue dissolved in methanol (60 mL). The mixture was filtered and then concentrated to a syrup under vacuum. Methylene chloride (80 mL) was added and the mixture filtered. The solvent was evaporated and the residue dried under vacuum to yield a white solid in 71% yield.  13  C NMR (D 2  O; ref. dioxane at 67.0 ppm): 13.5, 18.9, 32.9 (d, J=5.9), 50.7 (d, J=140.6), 51.5 (br s), 64.6 (d, J=5.9). 
     EXAMPLE 5 
     Biodistribution of Gd-DOTPMB 
     Complexation and Biodistribution 
     A complex of DOTPMB (FIG. 3) and Gd (0.012 M based on metal, 2:1 ligand/metal ratio) was prepared and spiked with tracer quantities of Gd-159. Complexation was determined to be greater than 99% by standard analytical methods described in earlier reports. Two Sprague-Dawley rats were then injected with the complex at a 0.05 mmol/kg level. The animals were sacrificed after 30 minutes and dissected for biodistribution data (Tables I and II); actual counts obtained from various tissues are shown in Table II. At the end of this time period, an average of 58% of the injected dose was found in small intestine (see entry for SM INTES in Table I). A similar experiment performed with a third rat yielded 52% in small intestine (Tables III and IV); actual counts obtained from various tissues are shown in Table IV. The bulk of the remaining activity in each case was eliminated via the renal system (Tables II and IV). 
     In order for localization to occur in the small intestine, the complex must first pass through the liver. Thus, since liver activity at the 30 minute time point (1%) was minimal (see e.g., Table I), the peak of liver localization passed within the prior 30 minutes. This is evident in an example of biodistribution 15 minutes after administration of chelated tracer, which is documented in Tables VIII and IX. Although by 15 minutes the peak of liver localization had passed for mouse 1, with 4% in the liver and 88% in the small intestine, mouse 2 still had a significant liver concentration (66%) at the 15 minute point. These animal models suggest that imaging within 15 minutes after administration of chelated tracer will be necessary for best definition of the liver. The following test description supports that conclusion. Higher doses would, of course, lengthen the time of liver localization at concentrations sufficient to substantially enhance liver imaging. 
     Gamma Imaging of DOTPMB 
     A Sm(153)-DOTPMB complex was prepared as described above for gamma imaging of a Sprague-Dawley rat. Images were acquired at one minute intervals over a 16-minute period. The image sequence revealed concentration of the chelate in liver within one minute following injection. The complex is then rapidly transported from the liver to the stomach and small intestine. Tables V, VI and VII contain data taken at 1 hour, 24 hours and 72 hours after injection, showing movement of the agent from stomach and intestine to feces. 
     
                       TABLE I                                                     
______________________________________                                    
TIME:  30 Minute Biodistribution                                          
DATE  LIGAND        METAL    COMMENTS                                     
8/6/91                                                                    
      DOTPMB-K,     Gd-159,  99% Complexation                             
4:1, LIG:MET Molar Ratio, (Metal = 3 × 10-4M)                       
       % DOSE/GRAM                                                        
       RAT 1 RAT 2      AVERAGE    +/-                                    
______________________________________                                    
WEIGHT   216.72  228.17     222.45   8.096                                
BONE     0.019   0.006      0.01     0.009                                
TAIL     0.077   0.068      0.07     0.007                                
LIVER    0.114   0.069      0.09     0.032                                
KIDNEY   0.169   0.126      0.15     0.031                                
SPLEEN   0.011   0.021      0.02     0.007                                
MUSCLE   0.007   0.005      0.01     0.001                                
BLOOD    0.021   0.017      0.02     0.003                                
HEART    0.014   0.000      0.01     0.010                                
LUNG     0.126   0.023      0.07     0.073                                
BRAIN    0.002   0.003      0.00     0.000                                
0.000 = NO ACTIVITY DETECTED                                              
                            DOSE                                          
BONE     0.281   0.106      0.193    0.124                                
TAIL     0.212   0.191      0.201    0.015                                
LIVER    1.234   0.755      0.994    0.339                                
KIDNEY   0.392   0.299      0.346    0.066                                
SPLEEN   0.009   0.011      0.010    0.002                                
MUSCLE   0.658   0.506      0.582    0.108                                
BLOOD    0.299   0.250      0.274    0.035                                
HEART    0.011   0.000      0.006    0.008                                
LUNG     0.158   0.029      0.094    0.091                                
BRAIN    0.004   0.004      0.004    0.001                                
STOMACH  0.574   0.530      0.552    0.031                                
SM INTES 80.304  36.405     58.354   31.041                               
LG INTES 0.591   0.433      0.512    0.112                                
______________________________________                                    
 
    
     
                                           TABLE II                                
__________________________________________________________________________
(see legend for Table I)                                                  
DATA                                                                      
    COUNTS                                                                
          ORGAN                                                           
               N ENTER WT                                                 
                       BCKG COR                                           
                              % DOSE/G                                    
                                     % DOSE                               
__________________________________________________________________________
 1        Std A                                                           
               × Rat 1 Wt                                           
                       0                                                  
 1        Std B                                                           
               × 216.72                                             
                       0                                                  
 2  414838                                                                
          Std C                                                           
               av 414404.5                                                
                       414405                                             
 3  1480  Bone 0.60     47    1.87E-02                                    
                                     2.81E-01                             
 4  1311  Tail 2.74     878   7.73E-02                                    
                                     2.12E-01                             
 5  5546  Liver                                                           
               10.86   5113   1.14E-01                                    
                                     1.23E+00                             
 6  2058  Kidney                                                          
               2.32    1625   1.69E-01                                    
                                     3.92E-01                             
 7  469   Spleen                                                          
               0.75     36    1.14E-02                                    
                                     8.57E-01                             
 8  478   Muscle                                                          
               1.52     45    7.06E-03                                    
                                     6.58E-01                             
 9  576   Blood                                                           
               1.62     143   2.12E-02                                    
                                     2.99E-01                             
10  481   Heart                                                           
               0.82     48    1.40E-02                                    
                                     1.15E-02                             
11  1088  Lung 1.25     655   1.26E-01                                    
                                     1.58E-01                             
12  449   Brain                                                           
               1.62     16    2.31E-03                                    
                                     3.74E-03                             
13  2811  Stomach      2378   5.74E-01                                    
14  333215                                                                
          Sm Intes     332782 8.03E+01                                    
15  2883  Lg Intes     2450   5.91E-01                                    
16  150310                                                                
          Urine        149877 3.62E+01                                    
17  400   Urine          0    0.00E+00                                    
18  428   Urine          0    0.00E+00                                    
19  443   BKG  228.17  WT Rat 2                                           
20  451   Bone 0.67     18    6.30E-03                                    
                                     1.06E-01                             
21  1225  Tail 2.82     792   6.77E-02                                    
                                     1.91E-01                             
22  3561  Liver                                                           
               10.96   3128   6.89E-02                                    
                                     7.55E-01                             
23  1674  Kidney                                                          
               2.38    1241   1.26E-01                                    
                                     2.99E-01                             
24  480   Spleen                                                          
               0.53     47    2.12E0-02                                   
                                     1.12E-02                             
25  469   Muscle                                                          
               1.66     36    5.16E-03                                    
                                     5.06E-01                             
26  559   Blood                                                           
               1.80     126   1.68E-02                                    
                                     2.50E-01                             
27  430   Heart                                                           
               0.85      0    0.00E+00                                    
                                     0.00E+00                             
28  554   Lung 1.28     121   2.27E-02                                    
                                     2.91E-02                             
29  452   Brain                                                           
               1.55     19    2.88E-03                                    
                                     4.46E-03                             
30  2629  Stomach      2196          5.30E-01                             
    151297                                                                
          Sm Intes     150864        3.64E+01                             
    2229  Lg Intes     1796          4.33E-01                             
    116731                                                                
          Urine        116298        2.81E+01                             
    901   Urine         468          1.13E-01                             
    423   Urine         10           0.00E+00                             
    424   BKG           10                                                
__________________________________________________________________________
 BKG AVG = 434                                                            
 
    
     
                       TABLE III                                                   
______________________________________                                    
TIME:  30 Minute Biodistribution                                          
DATE  LIGAND        METAL    COMMENTS                                     
8/6/91                                                                    
      DOTPMB-K,     Gd-159,  99% Complexation                             
4:1, LIG:MET Molar Ratio, (Metal = 3 × 10-4M)                       
                 % DOSE/GRAM                                              
                 RAT 3                                                    
______________________________________                                    
WEIGHT: 235.14                                                            
Bone               0.006                                                  
Tail               0.013                                                  
Liver              0.016                                                  
Kidney             0.121                                                  
Spleen             0.000                                                  
Muscle             0.000                                                  
Blood              0.000                                                  
Heart              0.000                                                  
Lung               0.009                                                  
Brain              0.004                                                  
0.000 = No Activity Detected                                              
Bone               0.109                                                  
Tail               0.038                                                  
Liver              0.196                                                  
Kidney             0.303                                                  
Spleen             0.000                                                  
Muscle             0.026                                                  
Blood              0.000                                                  
Heart              0.000                                                  
Lung               0.012                                                  
Brain              0.005                                                  
Stomach            0.012                                                  
Sm Intes           51.549                                                 
Lg Intes           2.232                                                  
______________________________________                                    
 
    
     
                                           TABLE IV                                
__________________________________________________________________________
(see legend for Table III)                                                
DATA                                                                      
    COUNTS                                                                
          ORGAN                                                           
               N ENTER WT                                                 
                       BCKG COR                                           
                              % DOSE/G                                    
                                     % DOSE                               
__________________________________________________________________________
1         Std A                                                           
               × Rat 1 Wt                                           
                       0                                                  
1         Std B                                                           
               × 235.14                                             
                       0                                                  
2   414367                                                                
          Std C                                                           
               av 413946                                                  
                       413946                                             
3   439   Bone 0.69    18     6.30E-03                                    
                                     1.09E.01                             
4   578   Tail 2.95    157    1.29E-02                                    
                                     3.79E-02                             
5   1232  Liver                                                           
               11.96   811    1.64E-02                                    
                                     1.96E-01                             
6   1675  Kidney                                                          
               2.51    1254   1.21E-01                                    
                                     3.03E-01                             
7   418   Spleen                                                          
               0.66    0      0.00E+00                                    
                                     0.00E+00                             
8   423   Muscle                                                          
               1.91    2      2.53E-04                                    
                                     2.56E-02                             
9   412   Blood                                                           
               1.84    0      0.00E+00                                    
                                     0.00E+00                             
10  417   Heart                                                           
               0.85    0      0.00E+00                                    
                                     0.00E+00                             
11  470   Lung 1.25    49     9.47E-03                                    
                                     1.18E-02                             
12  442   Brain                                                           
               1.28    21     3.96E-03                                    
                                     5.07E-03                             
13  470   Stomach      49     1.18E-02                                    
14  213806                                                                
          Sm Intes     213385        5.15E+01                             
15  9661  Lg Intes     9240          2.23E+00                             
16  102818                                                                
          Urine        102397        2.47E+01                             
17  12520 Urine        12099         2.92E+00                             
18  1447  Urine        26            6.28E-03                             
19  1421  BKG                                                             
__________________________________________________________________________
 BKG AVG = 421                                                            
 
    
     
                       TABLE V                                                     
______________________________________                                    
One Hour Biodistribution, Imaged Rat                                      
TIME: One Hour biodistribution                                            
DATE  LIGAND          METAL     COMMENTS                                  
8/8/91                                                                    
      DOTPMB-K, D.    Sm = 153  99% Complex                               
4:1, LIG:MET Molar Ratio (Metal = 3 × 10-4M)                        
             % DOSE/GRAM % DOSE                                           
______________________________________                                    
WEIGHT: 263.82                                                            
Bone           0.004         0.067                                        
Tail           0.038         0.093                                        
Liver          0.014         0.144                                        
Kidney         0.084         0.245                                        
Spleen         0.016         0.011                                        
Muscle         0.001         0.078                                        
Blood          0.001         0.019                                        
Stomach                      45.144                                       
Smll Int                     31.408                                       
Lrg Int                      0.003                                        
______________________________________                                    
 
    
     
                       TABLE VI                                                    
______________________________________                                    
24 Hour Biodistribution, Imaged Rat                                       
TIME: 24 Hour biodistribution                                             
DATE    LIGAND        METAL      COMMENTS                                 
8/8/91  DOTPMB-K      Sm = 153   99% Complex                              
4:1, LIG:MET Molar Ratio (Metal = 3 × 10-4M)                        
             % DOSE/GRAM % DOSE                                           
______________________________________                                    
WEIGHT: 163.82                                                            
Bone           0.008       0.146                                          
Tail           0.015       0.036                                          
Liver          0.010       0.106                                          
Kidney         0.154       0.451                                          
Spleen         0.029       0.020                                          
Muscle         0.017       1.883                                          
Blood          0.000       0.004                                          
Stomach                    0.053                                          
Smll Int                   2.109                                          
Smll Int                   19.611                                         
Lrg Int                    8.351                                          
Feces                      35.981                                         
Urine                      2.799                                          
Paper                      0.126                                          
______________________________________                                    
 
    
     
                       TABLE VII                                                   
______________________________________                                    
Rat Injected: 8/8/91                                                      
TIME: 72 hour biodistribution                                             
Date:    Ligand        Metal   Comments                                   
8/12/91  DOTPMB-K      Sm-153  99% Complex                                
4:1, LIG:MET MOLAR RATIO (Metal = 3 × 10-4M)                        
             % DOSE/GRAM % DOSE                                           
______________________________________                                    
WEIGHT: 269.58                                                            
Bone           0.014       0.219                                          
Tail           0.002       0.005                                          
Liver          0.002       0.030                                          
Kidney         0.019       0.054                                          
Spleen         0.000       0.000                                          
Muscle         0.000       0.000                                          
Blood          0.000       0.000                                          
Feces                      5.832                                          
Feces                      5.467                                          
Feces                      2.464                                          
Urine                      0.077                                          
Bladder                    0.242                                          
______________________________________                                    
 
    
     
                       TABLE VIII                                                  
______________________________________                                    
File = BTY15ST Summary Standardized Data Mouse #2                         
(15 minute biodistribution), 99% complex, 25.0 UL dose                    
Ca added to complex at 1;1 molar, lig: Ca                                 
DATE    LIGAND         METAL    COMMENTS                                  
10/30/91                                                                  
        DOTPME-K       Sm-153   #08-07-91                                 
2:1, Lig:Met Molar Ratio (Metal = 3 × 10-4M), pH 7 -= 8             
        % DOSE/GRAM                                                       
        MOUSE 1   MOUSE 2   AVERAGE                                       
______________________________________                                    
WEIGHT    15.854      10.702    13.278                                    
BONE      0.171       3.169     1.670                                     
TAIL      1.374       83.296    42.335                                    
LIVER     3.979       66.441    35.210                                    
KIDNEY    0.889       14.568    7.728                                     
SPLEEN    1.260       0.831     1.046                                     
MUSCLE    0.173       1.437     0.805                                     
BLOOD     43.105      3.743     23.424                                    
HEART     0.472       2.418     1.445                                     
LUNG      0.697       2.735     1.716                                     
BRAIN     0.023       0.139     0.081                                     
TUMOR     0.648       4.844     2.746                                     
STOMACH   14.272      4.343     9.308                                     
SMALL INT.                                                                
          88.504      40.343    64.423                                    
LARGE INT.                                                                
          3.320       2.298     2.809                                     
URINE     0.000       0.000     0.000                                     
BODY 1    0.408       1.637     1.022                                     
BODY 2    0.148       5.594     2.871                                     
______________________________________                                    
 *MOUSE 2 DID NOT BECOME ACTIVE AFTER ANESTHESIA, HOWEVER ALIVE***        
 
    
     
                       TABLE IX                                                    
______________________________________                                    
             % DOSE                                                       
             MOUSE 1 MOUSE 2                                              
______________________________________                                    
BONE           0.149     2.100                                            
LIVER          3.379     37.732                                           
KIDNEY         0.199     3.610                                            
SPLEEN         0.095     0.039                                            
MUSCLE         1.179     6.615                                            
BLOOD          44.420    2.604                                            
HEART          0.033     0.157                                            
LUNG           0.090     0.210                                            
BRAIN          0.010     0.054                                            
TUMOR          0.062     0.237                                            
STOMACH        3.565     0.586                                            
SMALL INT.     86.734    27.837                                           
LARGE INT.     2.994     1.145                                            
URINE          12.857    0.007                                            
BODY 1         2.294     6.890                                            
BODY 2         0.585     17.147                                           
______________________________________                                    
 
    
     Changes may be made in the construction, operation and arrangement of the various parts, elements, steps and procedures described herein without departing from the concept and scope of the invention as defined in the following claims.