in addition to use of known porphyrins , a number of additional photo - sensitive compounds may be complexed with selected metals . these additional compounds include , without limitation , 5 - amino levulenic acid ( 5 - ala ), protoporphyrin ix , tcpp , hematoporphyrin derivative , photofrin , photofrin ii , uroporphyrin , coproporphyren , tetraphenylporphinesulfonate ( tpps ) and tetraporphen ( 4 , n - methylulpyridil ) ( tmpp ). each of these photosensitive compounds , to include the below listing of metaloporphyrins are available from frontier scientific ( formerly porphyrin products ), of logan utah . these commercially available metaloporphyrins are further treated to convert the elemental metals to radioactive isotopes . conversely , these radioactive metaloporphyrins useful as radiopharmaceutical agents may be formed by purchasing or isolating radioactive metals of interest which are then combined with the desired porphyrin molecules to form radioactive metaloporphyrins . u . s . pat . no . 5 , 391 , 547 is hereby incorporated by reference for purposes of disclosing the use of metaloporphyrins and the methods by which metaloporphyrins are manufactured and combined with metal isotopes . some of the metaloporphyrins suitable for use in the present invention that are commercially available through frontier scientific include protoporphyrin ix and derivatives thereof including protoporphyrin ix dimethyl ester , protoporphyrin ix acid , and protoporphyrin ix na salt ; porphine ; octaethylporphine ; hematoporphyrin ix and derivatives thereof including hematoporphyrin d and hematoporphyrin ix dimethyl ester ; etioporphyrin and etioporphyrin i ; meso - tetraphenylporphine and derivatives thereof including meso - tetra ( n - methyl - 4 - pyridyl ) porphine , meso - tetra ( 4 - pyridyl ) porphine , meso - tetra ( 4 - sulfonatophenyl ) porphine and meso - tetra ( 4 - carboxyphenyl ) porphine ; coproporphyrin i and coproporphyrin iii ; deuteroporphyrin ix and derivatives thereof including deuteroporphyrin ix bis glycol and deuteroporphyrin disulfonic acid ; mesoporphyrin ix ; tetra tosylate ; uroporphyrin i ; and iso - hematoporphyrin ix . each of these porphyrins may be complexed with a radioactive isotope as desired . referring to fig1 the first step in the method is to introduce the radio tagged porphyrin compound to a patient having been diagnosed with , or having a suspected plaque buildup . the administration may be conducted by intravenous administration of the porphyrin radiopharmaceutical or may be conducted through a catheter specifically placed to direct the porphyrin radiopharmaceutical to a specific arterial site within the patient . this is shown as step 10 . the necessary period of time is then given to allow cell uptake of the compound , shown at block 12 . in block 14 , tomographic scanning can be conducted to determine sites of plaque buildup . if no appreciable arteriosclerotic abnormalities are observed , then the procedure is complete ; however , if arteriosclerotic abnormalities are found , delivery of the radio tagged compound results in selective ionizing radiation of the intra - arterial tissue occurring , shown at step 16 . as necessary , step 16 can be repeated by repeated introduction of the radio - tagged porphyrin compound or the further introduction of a different radio - tagged porphyrin compound , thereby enabling a selective number of radiation treatments to take place in order to destroy the targeted tissue . repeated radiation treatment is shown as optional step 18 . although step 16 is shown as a separate step , it shall be understood that the radiation treatment takes place simultaneously each time a patient is provided the radio - tagged porphyrin compound , even with the initial administration . additionally , for each necessary radiation therapy treatment , the particular metaloporphyrin can be dosed with the desired amount and type of radioactive material thereby providing adjustability for delivering the desired amount of radiation and type of radiation . as also mentioned above , if it were desired to actually visualize the destruction of the targeted tissue , an interventional procedure could take place such as by introduction of a catheter to the targeted area . using photo - detection methodology , the tissue can be observed to confirm the results of the treatment . this optional step is shown as step 20 . additionally , photo - dynamic therapy could also be conducted if an interventional procedure was performed to record and / or confirm the results of the procedure . this is shown as optional step 22 . further , an interventional procedure such as balloon angioplasty or stent emplacement can be augmented by the use of the porphyrin radiopharmaceuticals of the present invention . by this means , the porphyrin radiopharmaceuticals are administered prior to or after performing the interventional procedure to enhance the benefits gained from the interventional therapy and to decrease or eliminate the rate of restenosis seen following these procedures . the ability to simultaneously conduct a non - interventional diagnostic procedure and to simultaneously provide treatment is a very clear advantageous use of metaloporphyrins in diagnosing and treating arteriosclerotic abnormalities . the porphyrin which is used as a carrier for delivering the radiation to the patient also helps to localize the radioactive material in the tissue that requires the treatment . as described in u . s . pat . no . 5 , 391 , 547 , these porphyrin - based therapeutic agents may additionally localize to cancers of the lung . thus , as an additional benefit of the therapeutic treatment of arteriosclerotic plaque , these metaloporphyrin radiopharmaceuticals may additionally detect and treat any cancerous tissue present in patients in need of treatment for arteriosclerotic plaque . beta emitters , such as iodine - 131 ( 131 i ), yttrium - 90 ( 90 y ), copper - 67 ( 67 cu ) and rhenium - 186 ( 186 re ) have radiation safety advantages in that the beta particles do not penetrate tissue far enough that significant damage is done to healthy tissues . alpha emitters , such as astatine - 211 ( 211 at ) and bismuth - 212 ( 212 bi ), deliver larger doses to normal and arteriosclerotic tissue . gamma emitters provide the energy necessary to image the arteriosclerotic tissues which the metaloporphirins have accumulated in but may not be cytotoxic enough to kill that tissue thereby preventing the use of many gamma emitters for therapy . for example , gallium - 67 and indium - 111 are gamma emitters routinely used for medical imaging but are generally too weak to produce therapeutic effects . alternatively , copper - 67 releases abundant beta particles suitable for radiotherapy as well as gamma emissions suitable for diagnostic imaging . low energy x - ray emitters such as 125 i reduce the risks of damage to healthy tissues but high doses must be used to achieve a therapeutic outcome . the therapeutic compounds of the present invention can be administered to a patient alone or in combination with pharmaceutically acceptable carriers , the proportion of which is determined by the solubility and chemical nature of the compound and standard pharmaceutical practice . the physician will determine the ultimate dosage of these therapeutic agents which will be most suitable for prophylaxis or treatment and will vary with the form of administration and the particular compound chosen , and also , with the particular patient under treatment . the physician will generally aim to initiate treatment with the lowest dose that will successfully treat the arteriosclerotic lesion . for the radioactive compounds of the present invention , the dose is measured by the radioactivity emitted by the compound . thus , the weight of the metaloporphyrin and the coordinated metal is not used in determining the proper treatment dosage . for most patients , the effective range of therapeutic dosages is between about 5 gy and 25 gy of radiation . typically , the range is between about 9 gy and about 18 gy . preferably , the range is between about 15 gy and about 20 gy . referring specifically to the use of isotopes of copper , a metaloporphyrin complexed with 67 cu provides not only the ability to conduct visualization through spect scanning , but the 67 cu also provides beta radiation for purposes of providing radiation therapy . alternatively , 64 cu decays by electron capture , and beta decay accompanied by emission of radiation and gamma photons and can be used for treatment and for purposes of conducting pet scanning . therefore , it is also contemplated within the spirit and scope of the invention to provide metaloporphyrins for tomographic scanning and for radiation treatment . thus , it is also contemplated that the radioactive metals within the metaloporphyrin complexes may be selected for the production of gamma , positron , and beta emissions as desired to enable the desired type of tomographic scanning , as well as radiation therapy . moreover , it is possible to use a first radioactive metaloporphyrin for diagnosis and treatment of arteriosclerotic plaque followed by the use of a second radioactive metalophophyrin for the visualization of arteriosclerotic plaque to monitor treatment progression . in this way , the porphyrin and / or the radioactive isotope may be chosen due to their respective suitability for the procedure performed ; either detection or destruction of the arteriosclerotic tissue . for example , the initial diagnosis and treatment may be conducted with a 64 cu - containing porphyrin or a 67 cu - containing porphyrin while any subsequent visualization of arteriosclerotic plaque may be performed with 111 in - containing porphyrin . further to modifying or selecting the porphyrin and intercalated radioactive isotope for specific procedures , the porphyrin and isotope may be selected for repetition of the therapy . finally , it is contemplated that the therapy may also be modified in number and frequency of repetitive treatments based on the porphyrin and / or radioactive isotope used . this application has been described with respect to a preferred embodiment ; however , various modifications can be made which fall within the spirit and scope of the invention .
a method for treating arteriosclerotic lesions is provided wherein the method is characterized by administering a chemical compound to the patient , the compound being a porphyrin complexed with a radioactive metal . cells which exhibit an affinity for the porphyrin element indicate sites of plaque buildup . the radioactive metal within the compound is cytotoxic to cells in and surrounding the plaque and may allow tomographic scanning of the plaque as well . the complexed compound can be introduced to the patient a desired number of times to provide the necessary radiation treatment and ongoing monitoring of plaque removal .