the coiled marker of the invention is of such flexibility , both axially and transversally , so that , when inserted in a flexible organ such as a breast or a prostate , it will follow the changes of shape of said organ . the lateral flexibility of the markers must be similar to the flexibility of the tissues in which they are inserted . the coiled marker does not present any mechanical . resistance to the change of shape . after insertion through a needle , the marker is largely straight . when the organ changes in shape , either under the influence of the treatment , or under natural growth or stresses , the flexible markers will take a curved shape . it has been experienced that the coiled markers grip the organ they arc inserted into , and follow the longitudinal change of shape . one can therefore follow the change of shape and relative position of markers for following increase in size and change of shape of the organ . the fact that the markers of the invention have an excellent ultrasound visibility means that these repeated examination may be performed with the ultrasound technique , thereby avoiding the doses of repeated x - ray exposures . the implantation of two or more coiled markers in an organ allows following the position of the organ in the body . this is especially necessary for flexible organs such as breast or prostate . depending on contents of bladder or colon , the prostate may be displaced by several cm . treatment by an external beam may be directed with a precision better than 1 mm . fig1 a , 1 b , 1 c 1 d illustrate how the change of shape of an organ can be followed using the markers of the invention . in fig1 a , two markers 1 , 2 have been inserted into an organ 3 ( symbolized here as a gel - filled balloon ). the markers are straight after insertion . in fig1 b , the organ has been submitted to a uniform pressure from above , and the change in shape of the organ can be inferred from the change in relative orientation of the markers . similarly , in fig1 c , the organ has been submitted to a uniform tension from above , and the markers show a corresponding change in relative position . in fig1 d , the organ has been submitted to a non uniform pressure , e . g . due to stresses within the body ( full bladder or stomach , gas , swelling , etc ), stresses from localized growths ( tumors ), external stresses ( clothing or hardware in contact with the patient ), changes in weight , changes in hydration , etc . these are reflected in the change of shape of the intervening length of marker 1 . the use of two or more interstitial markers of the invention inserted parallel allow even better follow - up of the change of shape , as shown on fig2 a and 2 b . as illustrated on fig3 a , 3 b , and 3 c , the evolution of an organ or tumor can be followed using the interstitial markers of the invention . in fig3 a , one or more markers have been inserted parallel and straight around a region of interest 4 . subsequent images are taken after a period and can show growth ( fig3 b ) or decrease in size ( fig3 c ) of the region of interest . it is to be emphasized that the imaging technique used for the follow - up must be able to see the markers , but do not have to be able to see the region of interest . therefore , an imaging technique that is faster , less invasive , or more comfortable for the patient can be used . especially , the ultrasound imaging technique can be used . another application of the interstitial marker according to the invention is the marking of an “ excision bed ”. specifically , in numerous medical procedures a volume of tissue is surgically removed , such as in the case of a lumpectomy . in many of these cases it is important to be able to return to this same tissue volume for follow - up procedures such as radiation therapy , additional surgical excision , etc . as this “ empty ” volume is ill defined until the healing process is complete , elongated flexible markers placed in the tissue immediately adjacent to this volume can provide a detailed description of the location . in this case , point markers suffer the same deficiencies as identified above for soft tissue or tumor volume marking with the added issue that the typical 2 - 3 mm migration can cause the marker to fall into the excision volume and simply be “ floating ” in this tissue void . the extended length of the interstitial marker according to the invention eliminates this possibility . in these cases , the elongated marker could be either inserted into the target tissue or sutured in place in cases where an open surgical procedure has been used . fig4 represents a human breast 5 indicating the subsurface excision bed 6 ( void formed by the lumpectomy ), and the skin - level surgical scar 8 . the surgeon would have the option of deploying a continuous length of marker 7 around the periphery of the excision bed or several lengths placed strategically about the bed itself . the marker according to the invention is particularly useful in the external beam therapy of prostate cancer . patients who have been diagnosed with prostate ( or other ) cancer have a number of surgical ( radical prostatectomy or other surgical excision of the affected tissue ) and non - surgical options to evaluate for their treatment . these non - surgical options include radiation therapy options , hormone therapy , hypothermia , hyperthermia , drugs and genetic therapy . to date , only radiation therapy and surgical removal have shown 10 - year disease free survival rates above 80 % and represent the standard of care in the industry . of the radiation therapy options , the optimal goal is to deliver as much radiation ( up to the prescribed dose ) as possible to the organ ( in this case prostate ) and as little radiation as possible to all the surrounding tissues to reduce the comorbidity ( or side effects ) of this procedure . as a result , the progression of external beam radiation therapy over the past two decades has been focused on providing a beam of radiation that matches the shape of the organ . with each passing year , publications show advances in being able to target the radiation in more effective was and continually lessening the dose to adjacent tissues . at this point in time , the most accurate of these therapies ( proton therapy ) claim the ability to localize the beam to 0 . 1 mm of the intended target location . fig5 illustrates the method for marking the boundaries of anatomical regions , with the application to the prostate 9 . elongated marker 10 has been inserted in the prostate , near the prostate / rectum boundary . such marker may typically have a length of 4 cm , and is used for height adjustment . elongated markers 11 and 12 are located at the left and right hand side of the prostate , and delimit the lateral width of the gland in the mid - plane . these markers are used in conjunction with marker 10 for left - right alignment . marker 13 defines the prostate apex , and is used for cranial - caudal adjustment of patient position . marker 14 defines the prostate base , and is used also for cranial - caudal adjustment . once in place , these markers will follow the change of position , size and orientation of the gland , and thereby allow follow - up of the decrease or increase in size of the organ , and allow precise positioning and directing during radiation beam treatment . fig6 illustrates a known device 15 used to deploy the elongated marker pattern identified in fig5 through the use of needles 16 and a rectilinear template 17 designed for transperineal alignment with trus ( transrectal ultrasound ), and a method of patterned insertion of the elongated markers 1 through these needles , with pusher wires . prostate markers may also be inserted digitally through the rectum and positioned with tactile guidance and / or ultrasound imaging guidance . fig7 represents a coiled marker 1 , having an outer diameter of 500 μm ( 0 . 5 mm ), made of thin wire having a rectangular section of 50 × 200 μm , coiled with the broad side along the axis of the coil , and having a length of 5 cm . the length of the marker may be chosen as required by the application , and may be as short as 1 cm for marking the longitidinal ends of an organ , as in the case of prostate apex and base , and as long as necessary , e . g . for biopsy sites , where lengths of 10 cm or more may be used . depending on the application , the outer diameter may be chosen between 25 μm and 2500 μm , and the wire may have a circular cross section with a diameter between 10 μm and 2500 μm or a rectangular cross section with sizes between 10 μm and 500 μm . the aspect ratio i . e . the ratio of length to outer diameter in the example shown is 100 , but it has been determined that an aspect ratio in the range on 10 to 250 or higher provides a good combination of flexibility and x - ray and ultrasound visibility . another characteristic feature of a helical coil is the pitch , that may be defined as the axial length between two successive coil windings . other examples of coils suitable for particular applications are given below : primarily designed for use with ultrasound or diagnostic x - ray imaging techniques . the lateral flexibility obtained by using a coil according to the invention is very high . this flexibility is easily determined by measuring the droop of a length of helical coil fastened horizontally from one end . the other end droops in response to its own weight . it was determined that a coil made of stainless steel , having an outer diameter of 350 μm , a rectangular cross section wire of 200 μm by 50 μm , a 220 μm pitch , and a free length of 35 . 5 mm , droops by 2 . 9 mm . fig8 represents a preferred embodiment of a coiled marker 1 , having sections of different pitch . sections of high pitch 18 ( less dense coils ) provide a good flexibility , while sections of low pitch 19 ( dense coils ) provide good x - ray and ultrasound visibility . fig9 a - 9 d represent images of the marker coils of the present invention obtained from various imaging techniques : fluoroscopy ( fig9 a ), ct ( fig9 b ), x - ray ( fig9 c ) and ultrasound ( fig9 d ). it has been discovered by the inventors of the present invention that a helical coil , such as disclosed in u . s . pat . no . 6 , 419 , 621 , which is incorporated herein by reference , can effectively be used as an interstitial marker according to the invention . more precisely , said document discloses a radioactive coiled wire . these radioactive coiled wires are obtained through an activation process that may be exposure to an accelerated beam of charged particles of a precursor material , through ion implantation technique , or through thin film deposition of an isotope . the coil that can be used as interstitial marker is the coil prior to activation . this allows using same material for use as an interstitial marker as well as precursor for making a brachytherapy device . these coils may also be used after activation , and be used simultaneously as a brachytherapy device and as a marker , for a combined brachytherapy / external beam irradiation treatment .
the present invention related to an interstitial marker for localizing an organ , tumor or tumor bed within a mammalian body wherein said marker has a proximal end , a distal end , and a continuous intervening length , at least a portion of the intervening length of said marker being visible under at least one imaging modality and having a flexibility such that said marker follows movements and changes of shape of said organ , tumor or tumor bed .