This invention relates to devices and methods for use in therapeutic treatments. In particular, the present invention relates to a marker-flange for use in Magnetic Resonance Imaging (MRI) guided radiation therapy with a brachytherapy applicator.
Brachytherapy (also referred to as “short-distance therapy”) is a medical treatment procedure wherein target tissues, such as cancerous tumors, are treated with radiation sources that are placed inside or directly adjacent to the target tissue. Example target tissue includes cervical, vaginal, endometrial, breast, prostate, esophageal, lung, and skin cancers. Example applicators include interstitial needles, intraluminal applicators and intracavitary applicators.
Brachytherapy is a favorable alternative or supplemental treatment to External Beam Radiation Therapy (EBRT). In particular, EBRT procedures are performed by directing a radiation beam at the target tissues within the body from a radiation source external to the body. This normally results in radiation beams passing through healthy tissue before reaching the target tissue. However, by placing a radiation source inside or directly adjacent to the target tissue, brachytherapy procedures are capable of delivering a focused dose of radiation to the target tissue with relatively low dosages of radiation being delivered to surrounding or intervening healthy tissues and nearby organs at risk. Thus, as compared to EBRT procedures, brachytherapy procedures offer an effective manner for treating target tissue with very high radiation doses while presenting less concern for overdosing nearby healthy tissues.
Advances in computer imaging technology have led to the use of three-dimensional imaging systems for guiding the introduction of a brachytherapy applicator, as well as the radiation sources delivered thereby, into a patient's body and toward the target tissue. In the past x-ray based imaging systems, such as computed tomography (CT) imaging, were used to image and reconstruct a three-dimensional model of the applicator and the treatment region (e.g., the target tissues and the surrounding healthy tissues and organs at risk) for use as a guide in inserting and placing the applicator in a position for treatment. In recent years, however, preference has been given to the use of magnetic resonance (MR) imaging. In particular, MR imaging is preferred due to its ability to accurately define soft tissues such as the target tissue and the surrounding healthy tissues and organs at risk (e.g., the cervix, prostate, etc.). CT imaging does not offer the same accuracy in identifying these soft tissues. In addition, unlike CT scanning, MR imaging does not expose tissues to ionizing radiation. MR imaging is thus preferred for brachytherapy treatments, which often require multiple dosing procedures and which would therefore require subjecting the patient to repeated doses of ionized radiation if performed with a CT imaging modality.
One challenge that has arisen with MRI-guided brachytherapy is the three-dimensional reconstruction of brachytherapy applicators. This is significant because the brachytherapy applicator represents the irradiation source pathway, thereby defining the regions that will be exposed to radiation doses during treatment. Applicator reconstruction inaccuracies lead to uncertainties in the delivery of radiation doses to both the target tissue and organs-at-risk. Even relatively small geometric uncertainties in the three-dimensional reconstruction of the brachytherapy applicator, in both its dimensions and its placement within the treatment region, may have a critical effect on the radiation doses delivered to the target tissue and organs-at-risk. In particular, a mispositioning of the applicator may result in one or both of an underdosage to the target tissue (leading to the recurrence of the cancerous tissue) and the overdosage of nearby healthy tissue (causing undesired damage of healthy tissues). Accuracy in the positioning of the applicator is paramount as it has been estimated that the radiation dose gradient in an intracavitary brachytherapy application (e.g., gynecological, prostate, etc.) can be as much as 5-12% per millimeter. T. P. Hellebust, et al., Recommendations from Gynecological (GYN) GEC-ESTRO Working group: considerations and pitfalls in commissioning and applicator reconstruction in 3D image-based treatment planning of cervix cancer brachytherapy, Radiotherapy and oncology: journal of the European Society for Therapeutic Radiology and Oncology 96, 153-160 (2010).
In the past, with x-ray based imaging modalities (e.g., CT imaging), brachytherapy procedures were performed with titanium applicators owing to the strength, durability and biocompatibility of the material. However, titanium has been found to generate substantial imaging artifacts when imaged under an MR imaging modality. These artifacts result in an increased uncertainty when attempting to reconstruct a three-dimensional model of a titanium applicator, in both its geometric dimensions and location within the treatment region. As such, current brachytherapy procedures are regularly performed with plastic applicators.
Procedures using plastic applicators are generally performed by inserting a dummy-marker catheter into the plastic applicator. The dummy-marker catheter contains a marker agent that is responsive to MR imaging, in that it is capable of generating a signal sufficient to be observed with MR imaging and used to reconstruct a three-dimensional model of the plastic applicator. The plastic applicator, with the dummy-marker catheter, is then guided during insertion into the treatment region with MR imaging. Once the plastic applicator is in place, the dummy-marker catheter is removed and the applicator is connected to an afterloader that controls the delivery of an irradiation source through the inserted brachytherapy applicator.
However, plastic brachytherapy applicators are not ideal. Plastic applicators generally have an outer diameter of 6-7 mm, which is almost twice the size of a titanium applicator, which generally has an outer diameter of 3-3.2 mm. This increased size of the plastic applicator results in an increased discomfort to patients upon insertion into sensitive regions of the body (e.g., the cervix, the prostate, etc.). In addition, plastic applicators are not as mechanically robust as titanium applicators, thereby increasing the risk that the applicator may break during insertion and result in complications to the treatment procedure.
Recently, there has been developed “applicator libraries”, such as BrachyVision™ v8.9 (available from Varian Medical Systems, Charlottesville, Va., USA). These applicator libraries store files containing characteristics of brachytherapy applicators, including geometric dimensions of various applicator configurations. In a treatment procedure, the applicator library files may be imported to a treatment data set and used to reconstruct a three-dimensional model of the physical applicator being used in the procedure. This may done by identifying a number of relevant points on the physical applicator with a three-dimensional imaging, and then registering the identified points with corresponding points in the stored library file. In this way, a model of the applicator may be generated showing its orientation within the treatment region. A further discussion of applicator libraries, and applicator commissioning, is provided by T. P. Hellebust, et al., Recommendations from Gynecological (GYN) GEC-ESTRO Working Group: considerations and pitfalls in commissioning and applicator reconstruction in 3D image-based treatment planning of cervix cancer brachytherapy, Radiotherapy and oncology: journal of the European Society for Therapeutic Radiology and Oncology 96, 153-160 (2010).
Even with the availability of applicator libraries however, there persist difficulties in attempting to use titanium applicators for brachytherapy procedures. In particular, though the precise dimensions of a titanium applicator may be recorded in a library file and imported into a clinical setting, complications arise in attempting to accurately register the imported dimensions from the library file with the dimensions of the physical applicator. This is due to the generation of susceptibility artifacts by the titanium material during MR imaging, which obscure the image and introduce inaccuracies in attempting to identify relevant points on the physical applicator for registration with the library file. Thus, performance of a brachytherapy procedure with a titanium applicator and a corresponding applicator library file normally requires the use of multiple imaging modalities (e.g., a combination of CT and MR imaging)—with a first imaging modality being used to reconstruct three-dimensional models (e.g., CT imaging modality), and a second imaging modality being used to guide insertion and placement of the applicator (e.g., MR imaging modality. This use of multiple imaging modalities complicates the procedure, increases the time and expense for performing the procedure, and continues to subject healthy tissues to ionizing radiation (e.g., through CT imaging).
The present application provides a novel marker-flange for MRI-guided brachytherapy. The marker-flange is configured to be received on, and affixed to, the external surface of a tandem in a brachytherapy applicator. The marker-flange includes a hollow chamber that holds an MR imaging responsive marker agent, and one or more ports for injecting and extracting a marker agent to and from the hollow chamber.
The marker-flange is provided with a configuration making it suitable for use as a cervical flange (i.e., a cervical stopper) with the tandem of an intracavitary brachytherapy applicator (e.g., a tandem-and-ovoid or tandem-and-ring applicator). In another example, the marker-flange is provided with a configuration making it suitable for use as a cervical sleeve. In yet another example, the marker-flange is provided with a configuration making it suitable for use as the “ring” structure in a tandem-and-ring applicator.
The marker agent contained within the hollow chamber of the marker-flange is an MR imaging responsive liquid marker material that generates MR image signal intensities sufficient to overcome susceptibility artifacts generated by titanium materials when subjected to MR imaging. In this manner, the combination of the external marker-flange with the marker agent provides clearly defined images with improved geometric accuracies, thereby facilitating the identification of relevant points on a physical brachytherapy applicator, and the registration of those points with corresponding points in an applicator library file.
The combination of the marker-flange and marker agent, with the improved signal intensities and geometric accuracies, thus facilitates the use of titanium applicators while also achieving increased reconstruction and dosimetry accuracies—while further enabling the procedure to be performed with only an MR imaging modality (thereby obviating the need for a CT imaging modality). The marker-flange and marker agent combination can also provide these same benefits when used with plastic applicators.
The marker-flange, with a marker agent therein, may be configured for a one-time use. Alternatively, the marker-flange may be configured for sterilization and refilling (enabling the removal and replacement of a marker agent) so as to permit repeated uses.
Both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the invention as claimed. The accompanying drawings provide a further understanding of the invention; are incorporated in and constitute part of this specification; illustrate several embodiments of the invention; and, together with the description, serve to explain the principles of the invention.
The following examples are intended to illustrate but not to limit the invention.
Marker-Flange
The flange body 110 may be formed as a solid mold, with the hollow chamber 118 and the ports 120 formed as spatial voids within the otherwise solid mold. Alternatively, the flange body 110 may be formed as a hollow body, from two separately molded halves, with the hollow chamber 118 formed as a separate circular lumen that is inserted between the two halves of the flange body 110 during assembly. When forming a separate lumen body for the hollow chamber 118, the ports 120 may be formed as projections on the lumen body and then joined in a liquid-tight connection with cavities formed on an opposing face A/B of flange body 110.
The flange body 110 is formed from a biocompatible material which is MR imaging compatible to the extent that it will not interfere with the generation of MR image signals from an MR image responsive marker agent contained within the hollow chamber 118. The flange body can be made out of plastic material such as polyethelene. Examples of suitable materials for forming the flange body 110 include polysulfone, acetal, carbon fiber, polytetrafluoroethylene, fluorinated ethylene propylene, polytetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyvinyl chloride, polypropylene, polyethelene, polyethylene terephthalate, broad fluoride, and similar biocompatible plastics. If the marker-flange 100 is desired for repeated uses, then the flange body 110 may be formed from a material suitable for repeated sterilization procedures, such as acetal which is feasible for repeated steam sterilization. However, alternative sterilization procedures may also be used, such as cold sterilization when the hollow chamber 118 contains a liquid or gel type MRI marker agent 122.
As shown in the example of
In another example shown in
In the example shown in
In another example, the outer wall 112 may be formed with a non-constant cross-sectional perimeter, such that the marker-flange 100 is provided with a contoured outer wall 112. A contoured shape for the outer wall 112 may include a tapered shape that decreases in width from one end to the other. Another contoured shape may include an hourglass shape, having an increased width at the proximal and distal ends and a decreased width in a mid-region therebetween. A further contoured shape may include a ribbed shape with a series of protuberances, or wave-like peaks and troughs, arranged along a length of the outer wall 112. The use of a contoured outer wall 112, such as the tapered and hourglass shapes, may facilitate a compact construction of a tandem-and-ovoid brachytherapy applicator by permitting the marker-flange 100 to closely conform to the curved portions of the ovoids. Also, a contoured shape such as the hourglass shape or the ribbed shape may provide a gripping region on the flange body to facilitate extraction of the flange marker 100, such as when the flange marker is integrated in a cervical sleeve 101.
As shown in
The inner wall 114 and the cavity 116 may also be configured for reception of tandem applicators that have non-cylindrical cross-sections (e.g., oval, triangular, rectangular and other polyhedron cross-sections). Independent of the shapes chosen, both the outer wall 112 and the inner wall 114 may also include beveled edges extending between the walls and the faces A/B.
In examples where the hollow chamber 118 is formed as a lumen body (separate from two halves of a hollow flange body 110), the material used to form the lumen body may be a similar material as that used for forming the flange body 110. The ports 120 communicate with the hollow chamber 118, and are at least partially filled with a sealing agent in a sufficient volume to provide a liquid tight seal between the hollow chamber 118 and an external environment outside the flange body 110. A suitable sealing agent will be biocompatible, and will be sufficiently elastic so as to retain a liquid-tight seal between the hollow chamber 118 and the environment external to the marker-flange 100 after having been penetrated by a syringe needle (e.g., a self-resealing liquid tight seal). Examples of suitable materials for a sealing agent include silicone caulk, acetal, polyethylene, and polysulfone. In examples where the marker-flange 100 is desired for repeated uses, the sealing agent is formed from a material suitable for repeated sterilization procedures, such as acetal and polysulfone. Again, sterilization procedures for the marker-flange 100 may include steam sterilization and cold sterilization.
In the Example shown in
One or more ports 120 may be arranged on only one of the faces A/B, or both of the faces A/B. In examples where the marker-flange 100 is provided with a shaped face A/B for contacting the cervix, the one or more ports 120 may be formed on the opposite face so as to avoid complications in forming a liquid-tight seal on the shaped surface. In examples where the marker-flange 100 is configured as a cervical sleeve 101 (as shown in
Again, in one example, the ports 120 are at least partially filled with a sealing agent in a sufficient volume to provide a liquid tight seal between the hollow chamber 118 and an external environment outside the flange body 110. The sealing agent in this example is sufficiently elastic so as to retain a liquid-tight seal between the hollow chamber 118 and the environment external to the marker-flange 100 after having been penetrated by a syringe needle (e.g., a self-resealing liquid tight seal). In another example, the ports 120 themselves may be formed of a material that is sufficiently elastic to exhibit a self-resealing, liquid tight, characteristic. In this alternative example, the marker-flange 100 may be formed without providing a sealing agent within the ports 120.
Marker-Flange Examples
The example shown in
The example shown in
As can be seen from a comparison of
Based on the differences in dimensions, marker-flanges 100 for use with titanium applicators may be produced with lesser quantities of raw materials for both the flange body 110 and the marker agent 122, thereby decreasing production costs. In particular, it is expected that the volume of an MR responsive marker agent 122 needed to fill the hollow chamber 118 for a marker-flange constructed for a plastic applicator will be approximately 133% (an additional ⅓rd) of the volume needed to fill the hollow chamber 118 of a marker-flange constructed for a the titanium applicator. For example, the marker-flange in
It is noted that the measurements and dimensions in the foregoing examples of
Marker-Flange Ring
In yet another example, the marker-flange may be constructed integrally with a tandem-and-ring applicator as the “ring” portion of the applicator assembly. An example of a tandem-and-ring applicator 900 is shown in
A particular feature of the marker-flange 901 is that the flange body 910 also includes a source pathway cavity 950, which is configured to receive a radiation source 940 during brachytherapy procedures. As such, the hollow chamber 918 is formed in the flange body 910 in a manner to compliment the arrangement of the source pathway cavity 950, and also to serve as a reference point for the location of the source pathway cavity 950 during reconstruction imaging. In addition, it is not necessary that the inner wall 914 (and cavity 916) of the marker-flange 901 be constructed with a diameter that is configured to achieve a press-fit connection with a tandem applicator. In particular, in the marker flange 901, the flange body 910 is supported by its integrated construction with the tandem-and-ring applicator 900. Accordingly, it is not necessary that the marker-flange be constructed with a cavity 916 that enables it to be affixes to the outer surface of a tandem applicator. Instead, the cavity 916 is constructed with a diameter sufficiently larger to enable the insertion and retraction of a tandem applicator therethrough, without any interference by contacting the inner wall 914. As such, it is possible to construct a single marker-flange 901 with a cavity 916 having sufficient dimensions that will enable it to be selectively used with either titanium tandem applicators or plastic tandem applicators.
Marker Agents
The hollow chamber 118 contains a marker agent 122 that is MR imaging responsive in that it is capable of generating a signal that is viewable with an MR imaging modality. The marker agent 122 may be injected into the hollow chamber 118 during manufacture, prior to delivery to an end user (e.g., a clinical procedure setting). Alternatively, the marker-flange 100 may be manufactured and delivered to an end user without a marker agent 122 contained in the hollow chamber 118, and an end user may inject a desired marker agent 122 into the hollow chamber 118 through the ports 120 prior to use in a clinical procedure. Due to the liquid-tight resealing character of the sealing agent in the ports 120, injection of a marker agent 122 through the ports 120 in this manner will not compromise the liquid-tight seal of the hollow chamber 118.
In testing there was observed a volume-effect for the MR imaging responsive marker agents 122, at least when contained and imaged within a plastic material. In particular, a catheter having an inner diameter of 0.1 cm and an outer diameter of 0.2 cm was inserted into the plastic ring of a tandem-and-ring brachytherapy applicator and imaged with an MR imaging modality. It was found that MR imaging of the ring (with the 0.1 cm/0.2 cm diameter catheter) did not result in any discernible images of the marker agent contained therein. The same procedure was then repeated with a larger catheter having an inner diameter of 0.2 cm and an outer diameter of 0.3 cm. It was found that MR imaging of the second ring (with the 0.2 cm/0.3 cm diameter catheter) successfully produced images of the marker agent contained therein. Thus, without being bound by theory and/or simulation, it is believed that there is a volume-effect for the marker agents 122 and it is therefore recommended that the marker-flange 100 be constructed with a hollow chamber 118 having a cross-sectional area of 0.2 to 0.3 cm. In this regard, it is also recommended that, in use, a sufficient volume of marker agent 122 be injected into the hollow chamber 118 to substantially fill the chamber so as to provide a suitable cross-section of the marker agent 122 for MR imaging.
Examples of MR imaging responsive marker agents 122 for use with the marker-flange 100 include: saline; Conray®-60 (an iothalamate meglumine composition available from Mallinckrodt Inc., St. Louis, Mo. USA); CuSO4 (1.5 g/L); liquid Vitamin E; fish oil; 1% Agarose Gel (1 g agarose powder/100 mL distilled water); and C4 (a cobalt-chloride complex contrast; CoCl2: Glycine=4:1). The C4 marker agent is synthesized using anhydrous cobalt (II) chloride and glycine [H2N(CH2)CO2H] reactants, which are dissolved in deionized water stirred at 60° C., followed by slow water evaporation yielding crystals of the synthesized compound. The crystals are then dissolved in deionized water stirred at 60° C. in the amount of 0.3-10% by weight.
The preferred marker agent 122 for use with the marker-flange 100 may vary based upon the imaging modality to be used in the procedure. For example, marker agents that yield favorable signals when imaged with a T1-weighted MR imaging modality (3.0 Tesla, with 1 mm slice thickness—hereafter “T1MRI”) may prove unfavorable when imaged with a T2-weighted MR imaging modality (3.0 Tesla, with 3 mm slice thickness—hereafter “T2MRI”), and vice-versa.
Signal intensities and geometric accuracies for the foregoing marker agents 122 were quantified through tests performed with the three phantoms shown in
Phantoms
The marker-flange phantom 402, shown in
The tandem-and-ring phantom 404, shown in
The interstitial needle phantom 406, shown in
Marker-Agent Signal Intensities
In all of the phantoms 402, 404 and 406, 3% agarose gel (3 g agarose powder/100 ml distilled water) was used to simulate human tissue. A Siemens MAGNETOM Trio® 3T MR scanner (available from Siemens Medical Systems, Erlangen, Germany), with a body/spine array coil, was used to obtain high resolution 3.0 Tesla MR images. The MR imaging was performed according to the protocol set forth by Y. Kim, et al., Int. J. Radiat. Oncol. Biol. Phys. 2011; 80:947-955. T2-weighted TSE (turbo-spin-echo) MRI (T2MRI) protocol consists of voxel size (1.0×1.0×3.0 mm3), slice thickness 3 mm, bandwidth 651 Hz, TR (repetition time) 2000 ms, and TE (echo time) 0.95 ms. T1-weighted GRE (gradient echo sequence) MRI protocol includes voxel size 1.2×0.9×1.0 mm3, slice thickness 1.0 mm, Bandwidth 600 Hz, TR 3.33 ms, and TE 0.95 ms. Both T2- and T1-weighted MRI (T1MRI) are scanned in axial direction with 3D isotropic reconstruction. The MRI marker signal can be increased by modifying MRI scan parameters. To demonstrate that the invented marker-flange generates significant marker signals under clinical MRI scan protocol, the clinical MRI scan protocols were not changed. A Siemens Biograph® 40 PET/CT scanner (available from Siemens Medical Systems, Erlangen, Germany) was used to obtain CT images of the marker-flanges 100 in the phantom 402 for use as “gold standard” measurements in quantifying the geometrical accuracy of the MR imaging signals generated by the marker-flange and marker agent combinations. The CT imaging protocol was kept constant between the individual images, including a slice thickness of 0.6 mm for high resolution images. ImageJ software (available from National Institute of Health Image, Bethesda, Md., USA) was used for comparative image analysis.
As can be seen in
As can be seen in
The geometric accuracy of the marker-flange 100 and marker agent 122 combinations were assessed by comparing measurements taken from the centers of the marker agent 122 in images obtained with MR imaging modalities and with similar measurements taken from images obtained with an CT imaging modality.
In particular, the phantom 402 was used to obtain images in both T1MRI and T2MRI modalities, as well as the CT imaging modality. The MR and CT images were then registered with one another in two steps using multi-imaging modality registration software Syngo® (available from Siemens Medical Systems). In step one, as shown in
After the CT and MR images were registered, four distances were measured from center regions of the marker agent 122 to reference walls (X1, X2, and X3) in an MRI Coronal view (
It is noted that the CT images used as the “gold standard” for comparison with the MRI images were taken at a slice thickness of 0.6 mm. Thus, the CT images provide a highly accurate geometrical reference for assessing the accuracy of the MRI images. In addition, it is noted that uncertainties caused from distortions and chemical shift artifacts were not separately measured; and that the values of Table 1 include any such uncertainties, along with any uncertainties induced by the registration algorithm and pixel size (0.4 mm) on the image registration software.
As can be seen from Table 1, under the T1MRI modality, the marker-flange 100 provided a geometric accuracy with an average difference (Δ) of less than 1 mm for each of the marker agents Conray®-60; saline; 1% agarose gel; and CuSO4. The marker agent CuSO4 showed the highest geometric accuracy under the T1MRI modality with a 3D MR image distortion of only 0.42±0.14 mm. It is noted that 0.5 mm is theoretically the smallest uncertainty when using a 1 mm slice thickness.
As can also be seen from Table 1, though less accurate than the T1MRI modality, each combination of the marker-flange 100 and marker agent 122 succeeded in achieving an average difference (Δ) of less than 3 mm under the T2MRI modality. Without wishing to be bound by theory and/or application, it is believed that these higher values under the T2MRI modality are due to the larger slice thickness (3 mm in T2MRI as compared to 1 mm in T1MRI).
Preferred Marker Agents
A preferred marker agent 122 will produce high-intensity signals while yielding high geometric accuracies. Thus, for three-dimensional reconstruction with a T1MRI modality, the marker agents CuSO4, C4, and liquid vitamin E are preferred. Alternatively, for three-dimensional reconstruction performed with a T2MRI modality, the marker agents saline and CuSO4 are preferred.
If the marker-flange 100 is desired for repeated uses, then it may also be preferred that the marker agent 122 is be minimally affected by evaporation and/or degradation so as to allow for better sustainability of the MRI signal intensity over time. It is noted that liquid vitamin E was found to be less effected by evaporation than CuSO4, with CuSO4 being observed to degrade in as a little as three months. Accordingly, preference may be given to using liquid vitamin E as a marker agent 122 (over CuSO4) in favor of its longer stability. Alternatively, a reusable marker-flange 100 may employ a degradable marker agent 122, such as CuSO4, with the marker agent being replenished on a regular schedule by extracting the degraded volume of the marker agent 122 from the marker flange and replacing it with a fresh volume of marker agent 122 via a port 120 in the flange body.
Methods of Use
The marker flange 100 may be received by an end user (e.g., a clinical treatment facility) with a suitable marker agent 122 contained in the hollow chamber 118. Alternatively, the marker-flange 100 may be received by an end user without any marker agent 122, and the end user may introduce a suitable marker agent 122 into the hollow chamber 118 prior to use. Introduction of the marker agent 122 may be achieved, with the use of a syringe, through the port 120.
Prior to initial use, the end user's applicator library should be updated to commission the marker-flange 100 and generate library files for use with the marker-flange. The commissioned library files for the marker-flange should include the geometric dimensions of the marker-flange 100 as well as relevant identifiable points on the marker-flange for use in registering the library file with corresponding points generated from imaging a physical marker-flange 100 affixed to a brachytherapy applicator.
Preferably, commissioning of the marker-flange 100 should include separate files for each variation of the marker-flange 100 (e.g., titanium marker flanges having a 1.6 cm width; plastic marker-flanges having a 1.9 cm width, and etc.). In addition to geometric dimensions of the marker-flange 100 itself, commissioning should also include geometric dimensions relating the location at which the marker-flange 100 will be affixed on an applicator with other relevant structures of the applicator (e.g., a distance from the affixed marker-flange location to a tandem tip; a distance from the affixed marker-flange location to an ovoid or ring structure; etc.). Commissioning should also include separate library files for each brachytherapy applicator (e.g., various tandem-and-ovoid applicators with a marker-flange; various tandem-and-ring applicators with a marker-flange; etc.), and may also include a separate file for each combination of an applicator, marker-flange 100, and marker agent 122.
When performing a brachytherapy procedure, the corresponding applicator library file for the chosen combination of a brachytherapy applicator, marker-flange 100 and marker agent 122 is selected. MR imaging is performed to identify relevant points on the marker-flange 100, and those point are registered with corresponding points stored in the applicator library file to reconstruct an accurate three-dimensional model of the brachytherapy applicator (and its orientation within the treatment region) based on the images of the marker-flange 100. The reconstructed model is then used to facilitate MRI-guided insertion and placement of the brachytherapy applicator in preparation for the delivery of a radiation source material to a target tissue.
In another example, the marker-flange 100 may be affixed on the brachytherapy applicator at a position to serve as a cervical flange. As a cervical flange the marker-flange 100 may be affixed to the outside surface of a tandem applicator and used to abut the cervix during insertion of the tandem into the cervical OS. In this manner, the cervical marker-flange 100 may be used to guide and limit the insertion distance of the tandem applicator into the uterus, thereby minimizing the possibility of causing harm the surrounding tissues (e.g., preventing perforation of the uterine wall from over-extension of the tandem).
In a further example, when configured as a cervical sleeve 101, the marker-flange 100 may again be affixed on the brachytherapy applicator at a position to serve as a cervical flange. However, as a cervical sleeve 101 the marker-flange 100 may facilitate brachytherapy treatments that will require multiple dose-delivery procedures. In particular, the integrated cervical sleeve 101 may be introduced into the vaginal cavity during an initial brachytherapy procedure, and the shaft 124 inserted into the cervical OS. The cervical sleeve 101 may then be sutured in place, using the channels 132 on the flange body 110 as anchoring structures, and the cervical sleeve may left in situ after completion of the initial brachytherapy procedure. Thereafter, in subsequent brachytherapy procedures, the cervical sleeve 101 (with the marker agent 122 contained therein) may be employed as a reference point in reconstructing a three-dimensional model of the treatment region and further facilitate an MRI-guided insertion of a brachytherapy applicator. When performing the subsequent dosing procedures, a separate marker-flange 100 may be affixed on the brachytherapy applicator to further assist in the three-dimensional reconstruction and MRI-guided insertion of the applicator itself.
In yet a further example, the marker-flange may be configured as a ring structure 901 integrated in a tandem-and-ring applicator 900. In such an instance, the marker-flange 901 may be used in a similar manner as contemplated in the previous methods (for marker-flanges generally). However, due to the proximity of the hollow chamber 918 to the source pathway cavity 950, the marker-flange 901 may also be used to achieve improved accuracy in the reconstruction of the source pathway within the ring structure of the tandem-and-ring applicator.
The inventive marker-flange 100 set forth herein, in combination with the marker agents 122, promotes the generation of strong MR image signal intensities with high geometric accuracies. In particular, the MR image signals generated by the marker-flange 100 have been found to overcome the susceptibility artifacts generated by titanium materials, thereby facilitating the use of titanium applicators in brachytherapy procedures with the use of only an MR imaging modality. In addition, the marker-flange 100 has been found to achieve improved geometric accuracies that are expected to improve geometric accuracies in the three-dimensional reconstruction of applicators, as well as improve the dose delivery accuracy of a radiation source. Furthermore, in addition to facilitating the use of titanium applicators, the inventive marker-flange 100 is expected to also improve reconstruction and dose delivery accuracies with plastic applicators.
To the extent necessary to understand or complete the disclosure of the present invention, all publications, patents, and patent applications mentioned herein are expressly incorporated by reference to the same extent as though each were individually so incorporated.
Having thus described exemplary embodiments of the present invention, it should be noted by those skilled in the art that the foregoing disclosures are exemplary only and that various other alternatives, adaptations, and modifications may be made within the scope of the present invention.
For example, although the foregoing examples are directed at a cylindrically shaped marker-flange 100, it is understood that the marker-flange 100 may be formed with any desired shape (e.g., conical; cubic; dodecahedron; etc.), and that certain shapes having select symmetrical axes may facilitate the MR imaging identification and three-dimensional reconstruction of the marker-flange. Additionally, although the marker-flange 100 has been disclosed relative to the foregoing marker agents 122, the marker-flange may also be used with other liquid marker agents, and may also be adapted for use with solid marker agents. Furthermore, although the examples in the foregoing disclosure are directed at brachytherapy procedures for the treatment of endometrial cancers, the marker-flange 100 may be adapted for use in other intracavitary brachytherapy procedures such as the treatment of prostate and esophageal cancers. In addition, ranges expressed in the disclosure are considered to include the endpoints of each range, all values in between the end points, and all intermediate ranges subsumed by the end points.
Accordingly, the present invention is not limited to the specific embodiments as illustrated herein, but is only limited by the following claims.
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Number | Date | Country | |
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20140275964 A1 | Sep 2014 | US |