a more complete understanding of the procedures and products of the present invention may be had by reference to the accompanying drawings in which fig1 is a schematic flow diagram of the processes of the invention setting forth the preferred modes of operation . fig2 illustrates an apparatus suitable for carrying out the process shown in fig1 . the flow diagram of fig1 mentions certain specific reactants and procedural steps which are the most desirable in carrying out the present invention . other reactants and procedural steps can be employed , however , as will be explained more fully in a later section of this specification . for instance , although the flow diagram refers specifically to the use of 76 br 2 , 77 br 2 or 82 br 2 as the brominating agent for the dye precursor compound , the use of other gamma - emitting isotopes of br 2 is feasible . in the starting stage of this flow diagram there is given , as an example of a suitable dye precursor compound , phenolphthalein . all of the dyes in the following table can be prepared by the process of this invention . they are shown in their final brominated form , including tetrabromophthalein . the starting compounds are , of course , the same as the final dye compounds except that they are not brominated in any position . table i______________________________________ ## str1 ## 1 ○ bromphenol blue : 4 , 4 &# 39 ;-( 3h - 2 , 1 ,- benzoxathiol - 3 - ylidene ) bis [ 2 , 6 - dibromophenol ] s , s ,- dioxide ## str2 ## 2 ○ bromcresol purple : 4 , 4 &# 39 ;-( 3h - 2 , 1 - benzoxathiol - 3 - ylidene ) bis [ 2 - bromo - 6 - methylphenol ] s , s - dioxide ## str3 ## 3 ○ bromcresol green : 4 , 4 &# 39 ;-( 3h - 2 , 1 - benzoxathiol - 3 - ylidene ) bis [ 2 , 6 - dibromo - 3 - methylphenol ] s , s - dioxide ## str4 ## 4 ○ ethyl eosin : 2 &# 39 ;, 4 &# 39 ;, 5 &# 39 ;, 7 &# 39 ;,- tetrabromofluorescein ethyl ester ## str5 ## 5 ○ philoxine b ( red ); ## str6 ## 6 ○ tetra bromo phenol blue : ## str7 ## 7 ○ tetrabromophenolphthalein : 3 , 3 - bis -( 3 , 5 - dibromo - 4 - hydroxy - phenyl )- 1 ( 3h )- isobenzofuranone ## str8 ## 8 ○ sulfobromophthalein sodium ( bsp ): 5 , 5 &# 39 ;-( 4 , 5 , 6 , 7 - tetrabromo - 3 - oxo - 1 ( 3h )- isobenzofuranylidene ) bis [ 2 - hydroxybenzenesulfonic acid ] disodium salt ## str9 ## 9 ○ eosine i bluish : 4 &# 39 ;, 5 &# 39 ;- dibromo - 3 &# 39 ;, 6 &# 39 ;- dihydroxy - 2 &# 39 ;, 7 &# 39 ;- dinitro spiro [ isobenzofuran - 1 ( 3h ), 9 &# 39 ;[ 9h ] xanthen ]- 3 - one disodium salt ## str10 ## 10 ○ bromthymol blue : 4 , 4 &# 39 ; -( 3h - 2 , 1 - benzoxathiol - 3 - ylidene ) bis [ 2 - bromo - 3 - methyl - 6 -( 1 - methylethyl ) phenol ] s , s - dioxide ## str11 ## 11 ○ bromoxylenol blue : ## str12 ## 12 ○ bromophenol red : ## str13 ## 13 ○ eosine yellowish : 2 &# 39 ;, 4 &# 39 ;, 5 &# 39 ;, 7 &# 39 ;- tetrabromofluorescein______________________________________ preferably the reaction is carried out in an inert organic reaction medium , such as glacial acetic acid , in which the dye precursor compound is placed . the reactant bromine , i . e ., 76 br 2 , 77 br 2 or 82 br 2 , is in either the gaseous or liquid state . it is preferably introduced into the reaction mixture in the gaseous state through some kind of gas dispersing means . introduction of the reactant bromine gas in this manner effects sufficient agitation of the reaction mixture to avoid the necessity of any other kind of agitation , although this may , of course , be done if so desired . with respect to the bromine reactant , if 82 br 2 is chosen , it can be supplied directly as it is commercially available . since 77 br 2 is not commercially available , it must be generated from k 77 br , in a manner such as is described by slaunwhite and neeley , analytical biochemistry , vol . 5 , page 133 ( 1963 ). the reaction vessel containing the reaction mixture is disposed in a leaded fume hood and can be heated in any desired manner , but it is preferred to do this by immersion in an oil bath maintained at the desired reaction temperature . the heating is carried out at a temperature and for a time period sufficient to effect the desired bromination reaction . the temperature may be in the range of from about 110 ° c . to 125 ° c . thetime of reaction may be in the range of from about 4 hours to 12 hours . since hbr is formed as a by - product of the bromination reaction , it is vented from the reaction vessel , and passed serially through two naoh containing traps wherein it is neutralized to form nabr . since this is radioactive , it can be disposed of in any suitable and approved manner . after the reaction has been completed , the reaction vessel is flushed with nitrogen gas to remove hbr , and the solvent is removed by evaporation . the reaction vessel is then removed from the oil bath , preferably by the use of tongs , but maintained disposed in the leaded fume hood . while still in the hood , the contents of the reaction vessel are removed , and then subjected to a separation procedure such as selective extraction in order to recover the dye compound labelled with the radioactive bromine . thereafter , and while still being maintained within the leaded fume hood , the dye compound is subjected to a purification procedure , e . g ., column chromatography . as stated above , fig2 illustrates an apparatus arrangement suitable for carrying out the process set forth in the flow sheet of fig1 . if 77 br 2 is employed in the apparatus of fig2 then the 77 br 2 source consists of a 77 br 2 generator which converts 77 br - to 77 br 2 . this has been previously described by slaunwhite and neeley , utilizing manganese dioxide as the oxidizing agent . the 77 br 2 is distilled into the reaction mixture and then the reaction vessel is sealed . the following examples are given merely as illustrative of the present invention and are not to be considered as limiting . the above starting compound and glacial acetic acid were added to a reaction vessel disposed in an oil bath , all of which were placed in a leaded fume hood . thereafter , 77 br 2 in gaseous form was supplied to the reaction vessel . then the reaction vessel was heated in the oil bath at 123 ° c . and the reaction was completed in about 4 - 24 hours . after the reaction was completed , the reaction vessel was flushed with nitrogen gas to remove hbr , and the solvent was removed by evaporation . the reaction vessel was then removed from the oil bath , preferably by the use of tongs . thereafter , and while still in the leaded fume hood , the contents of the reaction vessel were removed and selectively extracted to recover the desired product , i . e ., the dye compound labelled with radioactive bromine , which was then purified by column chromotography . the product had the formula : ## str15 ## this product was diluted with an aqueous buffer , and then stored in a lead container in the leaded fume hood in which it had been prepared . the procedure set forthin example 1 above was carried out , but employing as the starting material in each example , the immediate precursor compound containing no bromine but otherwise corresponding to the compounds listed as entries 2 - 13 table i above . the reaction temperature and time of reaction were varied as required to obtain the desired product . the products obtained by these examples 2 - 13 correspond to entries 2 to 13 in said table i above . with respect to the dyes which are labelled with radioactive 76 br , 77 br or 82 br , this invention is not limited to the specific dyes disclosed in the foregoing description . thus , these specific dyes can be modified so that the bromine substituents can be at positions other than those specifically shown . in addition , the dyes which are labelled with radioactive 76 br , 77 br or 82 br and which can be prepared by this invention are not limited to the classes of dyes shown in the foregoing description . any known bromine - containing dye which is excreted to a large extent in the bile of a number of animal species is suitable if it is labelled with 76 br , 77 br or 82 br , i . e ., if the non - radioactive br substituents are replaced by 76 br , 77 br or 82 br in part or in whole . finally , with respect to the dyes which are taught as labelled with radioactive 76 br , 77 br or 82 br , thisinvention is not limited to the use of these three bromine isotopes . any gamma - emitting isotope of bromine can be employed . moreover , although the flow diagram of fig1 shows the reaction as being carried out in glacial acetic acid , there are many other inert reaction media which are suitable for this purpose . examples thereof are lactic acid and propionic acid . in general , any acidic media in which the brominating agent and the precursor dye are soluble are suitable . the flow diagram of fig1 shows the reaction vessel being heated by immersion in an oil bath . many other variants for such heating are available . for example , the reaction vessel can be jacketed , and a heat exchange liquid circulated therethrough . an alternative is the use of an electrically heated resistance wire wrapped around the exterior of the reaction vessel . next , the flow diagram of fig1 teaches separation of the dye compound from the reaction mixture by evaporation of the reaction medium followed by selective extraction . this , of course , could be varied in many ways . for example , chromatographic techniques such as tlc and hplc , etc ., are suitable . further , the flow diagram of fig1 shows purification of the dye compound by column chromatography . other procedures such as recrystallization , etc . are also suitable . an alternative synthesis in which the starting material is the relatively inexpensive bromide anion ( 76 br - , 77 br - , or 82 br - ) can be carried out . specifically , a solution of the alkali salt of the appropriate isotopic bromide is added to an acidic solution of potassium bromate and the specific precursor dye . the resultant solution is extracted into benzene , and the extract worked up in a similar fashion to that described in example 1 for the reaction mixture containing the labelled dye . the selected dye labelled with a gamma - emitting isotope of bromine , i . e ., 76 br , 77 br or 82 br , is injected intravenously into the patient . following injection , the liver and biliary system are monitored using equipment which maps radioisotope distribution within the human body . digital data can also be stored on magnetic tape , allowing computer processing to provide graphs showing activity variations with time in selected areas of the scan ( liver , gallbladder , intestine , etc .). distribution studies of the labelled dye after intravenous injection show initial rapid clearance of the radioactivity from the blood , specifically by the liver , with subsequent , almost complete , excretion into the biliary tract . stated otherwise , the labelled dye of this invention rapidly accumulates in the liver , and then is excreted from the liver to the biliary tract , so as to be useful for hepatic - biliary morphology and function studies . the monitoring equipment to be employed is well known in the art . one type of monitoring equipment found to be particularly useful for the purposes of this invention is of the scanning type , i . e ., the scanning head thereof is caused to trace an interlaced pattern which covers the area of the body which is of interest . one example of such equipment is that described in u . s . pat . no . 3 , 509 , 341 to hindel et al , issued apr . 28 , 1970 . in this system there is provision for storing the scanning data on magnetic tape for any desired use . if it is desired to use monitoring equipment of the camera type , i . e ., stationary with respect to the human body , but which can be employed to monitor specific areas of the human body , then u . s . pat . no . 3 , 983 , 394 to martone et al , issued sept . 28 , 1976 , is of particular interest . in this system there is provided window generating circuitry for defining a window in the detector field of view , and for gating to an output an indication of only those stimuli occurring within the window . this enables a very precise monitoring of a specific organ in the human body to be carried out . the system described in u . s . pat . no . 3 , 308 , 438 to spergel et al , issued mar . 7 , 1967 , is of particular interest with respect to the dynamic imaging studies referred to above . in this system radiation data are accumulated for a short period of time and then destructively read out of the memory and displayed on a cathode ray tube at selected rates . such a system has numerous advantages , e . g ., an immediate and accurate presentation of the monitored subject may be observed in detail as the actual events occur , or the system may be employed to provide permanent records for subsequent study as desired . the invention being thus described , it will be obvious that the same may be varied in many ways . such variations are not to be regarded as a departure from the spirit and scope of the invention , and all such modifications are intended to be included within the scope of the following claims .
a process for preparing bromine - containing dyes labelled with gamma - emitting isotopes of bromine , and the product thereof which is useful as an imaging agent for the hepato - biliary system , particularly in dynamic imaging methods . the dyes prepared are from the class of triarylmethane dyes , and also from the phthalein subclass of the class of xanthene dyes , and the labelling thereof is effected with 76 br , 77 br or 82 br . the process for preparing these dyes involves reacting the non - brominated dye precursor with either 76 br 2 , 77 br 2 or 82 br 2 . this is a substitution type of reaction in which a ring hydrogen is substituted by either 76 br , 77 br or 82 br .