WO2015023307A1 - Brachytherapy applicator and methods for generating anisotropic directional radiation profiles - Google Patents

Abstract

A brachytherapy applicator including an elongated intracavitary applicator, a plurality of channels disposed within the elongated intracavitary applicator, at least one shielding element, and configured to receive at least one radioactive element. In some instances, the at least one shielding element and the at least one radioactive element may be selectively positioned within the channels of the elongated intracavitary applicator to generate a desired anisotropic directional radiation profile for the treatment of cancer.

Description

BRACHYTHERAPY APPLICATOR AND METHODS FOR GENERATING ANISOTROPIC DIRECTIONAL RADIATION PROFILES

CROSS REFERENCES TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No.

61/710,149, filed October 5, 2012, which is hereby incorporated by reference in its entirety.

FIELD OF THE DISCLOSURE

[0002] The disclosure relates generally to brachytherapy and more particularly relates to systems and methods in brachytherapy for generating anisotropic directional radiation profiles for cancer treatment.

BACKGROUND OF THE DISCLOSURE

[0003] Breast cancer is the single most common cancer in women worldwide. It is also the principle cause of death from cancer among women. The U.S. has one of the highest rates of incidence, with approximately 225,000 cases a year. Due to advancements in diagnostic technologies and public awareness, up to 70% of new cases are candidates for local lumpectomies, which amounts to over 150,000 potential cases a year for brachytherapy. Cervical cancer is also prevalent among women. In 2013, there were an estimated 12,340 new cases with 4,030 deaths in U.S. Worldwide, the cervical cancer is the second most common cancer among women, with over 500,000 incidences per year. Brachytherapy use in cervical cancer is an integral part of the standard treatment. Brachytherapy is also an integral part of the treatment of other cancers, including rectal cancer, among others.

[0004] Currently, brachytherapy utilizes three dimensional (3D) imaging information (e.g., CT, MRI, and US) to build a unique patient model to deliver a customized treatment plan, driven by various dose-volume objectives. However, these improvements have not been accompanied by appropriate advancements in delivery technology that can utilize the abundant anatomic information available from the 3D images to the fullest. One problem is that all current brachytherapy applicators utilize geometric spreading of dwell positions, at best, to achieve conformal dose distributions by increasing the number of channels and spreading the brachytherapy applicator positions to logical locations. While useful, this approach is inherently limited by the isotropic radiation profile of the radiation source, such as 192-Ir. In this manner, it is intrinsically difficult to achieve conformal dose distributions to non-symmetric 3D target volumes.

SUMMARY OF THE DISCLOSURE

[0005] Some or all of the above needs and/or problems may be addressed by certain embodiments of the brachytherapy applicator disclosed herein. Accordingly to an embodiment, the brachytherapy applicator may include an elongated intracavitary applicator having a plurality of channels disposed within the elongated intracavitary applicator. The brachytherapy applicator includes at least one shielding element and at least one radioactive element insertable and removeably associated within the plurality of channels. In some instances, the at least one shielding element and the at least one radioactive element may both be selectively positioned at different locations within the elongated intracavitary applicator to generate a desired anisotropic directional radiation profile for the treatment of cancer.

[0006] Other features and aspects of the brachytherapy applicator will be apparent or will become apparent to one with skill in the art upon examination of the following figures and the detailed description. All other features and aspects, as well as other systems, methods, and assembly embodiments, are intended to be included within the description and are intended to be within the scope of the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The detailed description is set forth with reference to the accompanying drawings. The use of the same reference numerals may indicate similar or identical items. Various embodiments may utilize elements and/or components other than those illustrated in the drawings, and some elements and/or components may not be present in various embodiments. Elements and/or components in the figures are not necessarily drawn to scale. Throughout this disclosure, depending on the context, singular and plural terminology may be used interchangeably.

[0008] FIG. 1 depicts an example embodiment of a brachytherapy applicator in accordance with one or more embodiments of the disclosure. [0009] FIG. 2 depicts an example embodiment of a brachytherapy applicator in accordance with one or more embodiments of the disclosure.

[0010] FIG. 3 depicts an example embodiment of a portion of a brachytherapy applicator in accordance with one or more embodiments of the disclosure.

[0011] FIG. 4 depicts an example embodiment of a portion of a brachytherapy applicator in accordance with one or more embodiments of the disclosure.

[0012] FIG. 5 depicts an example embodiment of a portion of a brachytherapy applicator in accordance with one or more embodiments of the disclosure.

[0013] FIG. 6 depicts an example embodiment of a brachytherapy applicator in accordance with one or more embodiments of the disclosure.

[0014] FIG. 7 depicts an example embodiment of a single channel brachytherapy applicator in accordance with one or more embodiments of the disclosure.

[0015] FIG. 8 depicts an example embodiment of an isotropic radiation profile in accordance with one or more embodiments of the disclosure.

[0016] FIG. 9 depicts an example embodiment of a portion of a brachytherapy applicator in accordance with one or more embodiments of the disclosure.

[0017] FIG. 10 depicts an example embodiment of an anisotropic radiation profile in accordance with one or more embodiments of the disclosure.

[0018] FIG. 11 depicts an example embodiment in accordance with one or more embodiments of the disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0019] The brachytherapy applicator disclosed herein may be used to treat cervical, uterine, breast, and/or rectal cancer with brachytherapy, including high-dose-rate (HDR) brachytherapy. Other types of cancers or diseases also may be treated by the brachytherapy applicator of the present invention. That is, the brachytherapy applicator may be used in any suitable application for the treatment of cancer or other tissue diseases. HDR brachytherapy comprises the delivery of high-intensity radiation directly into cancerous sites. For example, at least a portion of the brachytherapy applicator may be positioned near a tumor, and radiation therapy may be administered by the brachytherapy applicator by selectively placing one or more radioactive elements inside one or more channels of the brachytherapy applicator to create a desired anisotropic radiation profile. The anisotropic radiation profile created the brachytherapy applicator may allow dose distribution to conform to the 3D target volumes unique to each patient, while minimizing radiation damage to surrounding healthy tissues.

[0020] The brachytherapy applicator disclosed herein may be incorporated into a tandem and colpostat applicator, a tandem and ovoids applicator, a ring and tandem applicator, a cylinder and tandem applicator, a Fletcher- style applicator, a Delclos-style applicator, a Manchester- style applicator, a Vienna-style applicator, a Stockholm-style applicator, a Miami-style applicator, or the like. The brachytherapy applicator disclosed herein may be incorporated into any suitable known applicator device for the treatment of cancer. In addition, the brachytherapy applicator disclosed herein may be used in conjunction with various accessories, including rings, tandems, cylinders, oviods, interstitial needles, balloons, or the like.

[0021] In certain embodiments, as depicted in FIG. 1 , a brachytherapy applicator

100 may include an elongated intracavitary applicator 102. In some instances, the elongated intracavitary applicator 102 may comprise a tandem structure. The elongated intracavitary applicator 102 may be any biocompatible tubing structure. For example, the elongated intracavitary applicator 102 may be plastic, such as polyoxymethylene. At least a portion of the elongated intracavitary applicator 102 may be suitable for intracavitary placement. For example, the elongated intracavitary applicator 102 may be shaped and configured to be inserted into the vagina, cervix, rectum, breast, or other bodily cavity for the treatment of cancer or other diseases. The elongated intracavitary applicator 102 may include a distal end 104 and a proximal end 106. In this manner, the distal end 104 may be suitable for intracavitary placement. FIG. 1 depicts the brachytherapy applicator 100 as a tandem and oviods applicator. That is, brachytherapy applicator 100 includes oviods 108.

[0022] FIG. 2 depicts a brachytherapy applicator 200 as a tandem and ring applicator. That is, brachytherapy applicator 200 includes a ring 202. As noted above, other applicator configurations may be used depending on the application and the cancer or other disease being treated. For example, as discussed below, the brachytherapy applicator may include a cylinder. Like the brachytherapy applicator 100, the brachytherapy applicator 200 may include an elongated intracavitary applicator 204. Similarly, the elongated intracavitary applicator 204 may include a distal end 206 and a proximal end 208.

[0023] As depicted in FIG. 3, the brachytherapy applicator 300 may include a plurality of channels 302 disposed within the elongated intracavitary applicator 304. Any number of a plurality of channels 302 may be selectively used for insertion of either a radioactive element or a shielding element, based upon the desired radiation profile to be administered. In some instances, the channels 302 may extend from a proximal end 306 of the elongated intracavitary applicator 304 to a distal end 308 of the elongated intracavitary applicator 304. That is, the channels 302 may be elongated. The elongated intracavitary applicator 304 may form a casing about the channels 302. The channels 302 may be arranged in a pattern or disposed in discrete locations. For example, the channels 302 may be arranged as an array about a cross-section of the elongated intracavitary applicator 304 in a honeycomb-like configuration. That is, the channels 302 may have a hexagonal or circular cross section, with the channels 302 being positioned adjacent to one another within the elongated intracavitary applicator 304 so as to fill the elongated intracavitary applicator 304 with the maximum number of channels 302. The channels 302 may comprise, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13, 14, 15, 16, 17, 18, 19, 20, or more channels 302. Any number of channels 302 may be used for receiving either a radioactive element or a shielding element. In other instances, the channels 302 may be disposed about a periphery of the elongated intracavitary applicator 304. That is, the channels 302 may be equally spaced apart from another in a circumferential array about a periphery, or cross-section taken perpendicular to the elongated axis of the elongated intracavitary applicator 304. However, the channels may be arranged in any pattern or disposed at any location within the elongated intracavitary applicator.

[0024] Still referring to FIG. 3, the brachytherapy applicator 300 may include at least one shielding element 310 and at least one radioactive element 312. In some instances, the shielding element 310 and the radioactive element 312 may comprise elongated rods. The shielding element 310 and the radioactive element 312 may be configured to be selectively positioned within the elongated intracavitary applicator 304 (e.g., about the distal end 308) in a desired pattern for the particular patient and condition to generate an anisotropic directional radiation profile for the treatment of cancer or other disease. [0025] For example, in some instances, one or more radioactive elements 312 may be positioned within the channels 302, and one or more shielding elements 310 may be positioned in the remaining channels 302 surrounding the radioactive elements 312. In this manner, the shielding elements 310 may direct the radiation profile created by the radioactive elements 312. Additional radioactive elements 312 and/or shielding elements 310 may be added or removed to vary the radiation profile. In some instances, no shielding elements 310 may be used, resulting in an isotropic radiation profile. In certain embodiments, the radioactive elements 312 and/or shielding elements 310 may be threaded into the channels 302 from the proximal end 306 of the elongated intracavitary applicator 304 to the distal end 308 of the elongated intracavitary applicator 304 or anywhere therebetween.

[0026] In certain embodiments, the invention provides methods of use wherein the brachytherapy applicator 300 may be positioned within a bodily cavity adjacent to a cancerous site. One or more radioactive elements 312 may be selectively placed within the channels 302, and one or more of the shielding elements 310 may be positioned in the remaining channels 302 surrounding the radioactive elements 312 to create a desired directional anisotropic radiation profile. The order in which the radioactive elements 312 and/or the shielding elements 310 are positioned within the channels 302 may depend on the particular patient and/or disease being treated. In most cases, the shielding elements will first be placed in the desired channels of the applicator prior to inserting one or more radioactive elements in the remaining channels. In some instances, after administering treatment, the radioactive elements 312 and/or the shielding elements 310 may be removed from the channels 302. Similarly, the radioactive elements 312 and/or the shielding elements 310 may be repositioned within the channels 302 during treatment or additional radioactive elements 312 and/or shielding elements 310 may be positioned in the channels 302 during or after treatment. In this manner, the brachytherapy applicator 300 provides real-time flexibility of dosage during treatments, and may be reconfigured to administer additional treatments.

[0027] In certain embodiments, as depicted in FIG. 4, the brachytherapy applicator 400 may include at least one shielding element 402 and at least one radioactive element 404. In this embodiment, the shielding element 402 may comprise a rod 406 having a number of channels 408 formed about a periphery 410 of the rod 406. The channels 408 may be radially spaced apart from one another to form a circular array when viewed in cross section perpendicular to the elongated axis of the rod. Any number of channels 408 may be used, including but not limited to, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or more channels 408. The channels 408 may extend from a proximal end 412 of the rod 406 to a distal end 414 of the rod 406. In some instances, the channels 408 may form grooves 416 having an open radially outer portion about an inner periphery of the elongated intracavitary applicator 418. Any number of channels 408 may be used. Moreover, the channels 408 may abut one another or the channels 408 may be spaced apart about the periphery 410 of the rod 406.

[0028] For example, the rod 406 and channels 408 may form a revolver-like configuration in cross section perpendicular to the elongated intracavitary applicator 418. One or more of the radioactive elements 404 may be positioned within the channels 408 for selectively generating the anisotropic directional radiation profile. That is, the rod 406 may act as a shield to direct the radiation profile created by the radioactive elements 404. In some instances, the rod 406 may be a metal alloy, such as tungsten or gold. In certain embodiments, additional shielding elements 420 may be positioned within the channels 408 that are not occupied by a radioactive element 404. In another embodiment, the rod 406 may not act as a shielding element 402, and only the shielding elements 420 positioned within the channels 408 that are not occupied by a radioactive element 404 may provide shielding and impart direction to the radiation profile. For example, the rod 406 may be plastic or integral with the elongated intracavitary applicator 418.

[0029] In certain embodiments, the brachytherapy applicator 400 may be positioned within a bodily cavity adjacent to a cancerous site. One or more of the radioactive elements 404 may be selectively placed within the channels 408 to create a desired directional anisotropic radiation profile. For example, the rod 406 may act as a shield to direct the radiation profile created by the radioactive elements 404. In some instances, after administering treatment, the radioactive elements 404 may be removed from the channels 408. Similarly, the radioactive elements 404 may be repositioned within the channels 408 during treatment or additional radioactive elements 404 may be positioned in the channels 408 during or after treatment. In this manner, the brachytherapy applicator 400 may be reconfigured to administer a variety of anisotropic irradiative treatments. In some instances, when acting as a shield, the rod 406 may be rotated within the elongated intracavitary applicator 418 to direct the anisotropic radiation profile.

[0030] FIG. 5 depicts an example embodiment of a brachytherapy applicator 500 for the treatment of breast cancer. In some instances, brachytherapy applicator 500 may include a balloon 502. The balloon 502 may be positioned about a distal end 504 of an elongated intracavitary applicator 506 for insertion and placement inside a lumpectomy cavity for the treatment of breast cancer. For example, the balloon 502 may be configured to be filled with water (or other fluids) to expand the lumpectomy cavity. Once expanded, one or more radioactive elements 508 may be positioned within the shielding rod 510 at the distal end 504 of the elongated intracavitary applicator 506. Although FIG. 5 depicts the balloon 502 incorporated into the revolver-like configuration of FIG. 4, the balloon 502 may equally be incorporated into the honeycomb-like configuration depicted in FIG. 3.

[0031] In some instances, a locking device 512 may be positioned about the elongated intracavitary applicator 506 to maintain the shielding rod 510 within the elongated intracavitary applicator 506. For example, in some instances, the shielding rod 510 may slide in and out of the elongated intracavitary applicator 506. In this manner, the balloon 502 and the elongated intracavitary applicator 506 may be positioned within a lumpectomy cavity. The shielding rod 510 may then be slide into the elongated intracavitary applicator 506, and the radioactive element 508 may be positioned within one of the grooves of the shielding rod 510. The locking mechanism may then be placed over the elongated intracavitary applicator 506 to secure the assembly in place. Such a configuration may allow for the removal of the shielding rod 510 and the radioactive element 508 without removing the balloon 502 and/or the elongated intracavitary applicator 506 from the lumpectomy cavity.

[0032] As depicted in FIG. 6, the brachytherapy applicator 600 may include a cylinder 602. The brachytherapy applicator 600 may include an elongated intracavitary applicator 604. Like the brachytherapy applicators described above, a distal end 606 of the elongated intracavitary applicator 604 may be configured to generate an anisotropic directional radiation profile using one or more radioactive elements and/or shielding elements. In addition, in some instances, the cylinder 602 may be configured to generate an anisotropic directional radiation profile using one or more radioactive elements and/or shielding elements. For example, the cylinder 602 may include the revolver-like configuration of FIG. 4 or the honeycomb-like configuration depicted in FIG. 3. In this manner, one or more radioactive elements and/or shielding elements may be positioned within the cylinder 602 to generate an anisotropic directional radiation profile about the cylinder 602. In other instances, the cylinder 602 may be a conventional cylinder that does not generate an anisotropic directional radiation profile.

[0033] In certain embodiments, the shielding element may comprise one or more tungsten rods. In another embodiment, the shielding element may comprise one or more gold rods. Any material suitable for shielding radiation may be used. For example, the shieling element may be any suitable metal alloy, such as a high density non-magnetic metal alloy. In another embodiment, the radioactive element may comprise 192-Ir, 60-Co, and/or 169-Yb. Other types of radioactive elements may be used. The elongated intracavitary applicator may be any biocompatible material, including plastic (e.g., polyoxymethylene). The elongated intracavitary applicator may at least partially enclose the shielding element and/or the radioactive element.

[0034] The anisotropic radiation profile provided by the brachytherapy applicators disclosed herein (when combined with optimized dwell positions and times) may increase the conformality of dose distributions that were previously unachievable. Example Embodiment - Cervical Cancer

[0035] A brachytherapy tandem applicator to treat cervix cancer using intracavitary HDR brachytherapy is disclosed herein. The brachytherapy tandem applicator for treating cervix cancer may include a similar configuration to the brachytherapy applicator 400 in FIG. 4. For example, the brachytherapy applicator may include a metal alloy shield (such as non-magnetic tungsten or gold alloy) with grooves to pass one or more HDR radioactive sources (such as 192-Ir, 60-Co, or 169-Yb) to create an anisotropic radiation profile, with inverse planning, that can create a desired and optimal dose distributions for the treatment of cervix cancer. The anisotropic radiation profile, when combined with optimized dwell positions and times, may increase the conformality of dose distributions that has been previously unachievable. The brachytherapy applicator disclosed herein is at least partially based on Dynamic Modulated Brachytherapy (DMBT) utilizing anisotropic modulation. DMBT utilizing anisotropic modulation is disclosed in: (1) Webster MJ, Devic S, Vuong T, et al. Dynamic modulated brachytherapy (DMBT) for rectal cancer. Med Phys 2013;40:011718; (2) Webster MJ, Devic S, Vuong T, et al. HDR brachytherapy of rectal cancer using a novel grooved-shielding applicator design. Med Phys 2013;40:091704; and (3) Webster MJ, Scanderbeg D, Yashar C, et al. Dynamic Modulated Brachytherapy for Accelerated Partial Breast Irradiation. Med Phys 2013;40:466. These three references are all hereby incorporated by reference in their entirety.

[0036] The metal grooved rod, enclosed in plastic (e.g., polyoxymethylene), may be inserted in the cervix-uterus anatomy, in combination with ovoids, rings, cylinders, interstitial needles, or other complementing applicators. The treatment may be initiated after insertion. The anisotropic radiation profile created through the intelligently shaped metal alloy rod may allow dose distribution to conform to the 3D target volumes unique to each patient, while minimizing radiation damage to surrounding healthy tissues such as the bladder, rectum, and sigmoids, for best treatment outcome. For example, the brachytherapy applicator may create an anisotropic radiation profile emitted from one or more HDR radioactive sources (such as 192-Ir, 60-Co, and/or 169-Yb) through intelligently shaped high density non-magnetic metal alloy tandem (such as tungsten or gold alloy) that is enclosed in a biocompatible plastic (such as polyoxymethylene) for easy insertion and placement inside the cervix-uterus anatomy. The anisotropic radiation profile, in combination with inverse planning optimization (collectively known as anisotropic modulation), may achieve improved dose conformality to arbitrary 3D target volumes. In contrast, existing technology uses isotropic radiation profiles in combination with a single channel tandem device. For example, FIG. 7 depicts an example embodiment of a single channel tandem device 700 that generates an isotropic radiation profile for use in intracavitary HDR brachytherapy of cervix cancer. The single channel tandem device 700 may include a centrally located single channel 702. A radioactive element 704 may be located within the channel 702. FIG. 8 depicts a Monte Carlo simulated dose distribution of an isotropic 192-Ir source in the conventional single channel tandem device 700 of FIG. 7.

[0037] FIG. 9 depicts a DMBT brachytherapy tandem applicator 900 similar to the brachytherapy applicator 400 in FIG. 4. For example, the DMBT brachytherapy tandem applicator 900 may include multiple peripheral channels 902 (e.g., six) grooved along a non-magnetic metal alloy 904 (e.g., tungsten alloy; p=18.0 g/cc), which is enclosed in a plastic tubing 906 (e.g., polyoxymethylene; p=1.41 g/cc). The total thickness of the DMBT brachytherapy tandem applicator 900 is about 6 mm, which enables insertion into the cervix. An example non-magnetic MRI-compatible metal alloy includes a tungsten rod having a composition of about 95 %-tungsten, 3.5%-nickel, and 1.5%-copper. A radioactive element 908 (e.g., 192-Ir) may be postioned in one of the channels 902. Due to the revolver-like design of the angular channel spacing (e.g., 60 degree spacing), the DMBT brachytherapy tandem applicator 900 allows for anisotropic modulation of radiation profiles (as depicted in the Monte Carlo simulation in FIG. 10) as opposed to the conventional isotropic radiation profiles (FIG. 8).

[0038] Once the DMBT tandem applicator is inserted in the cervix-uterus anatomy, in combination with ovoids, rings, cylinders, interstitial needles, and/or other applicators, the treatment optimization may be implemented with inverse planning algorithms to optimize the dwell positions and times to create conformal dose distributions to 3D target and organs-at-risk (OAR) volumes contoured from 3D imaging modalities such as CT, MRI, and/or ultrasound.

[0039] Several simulations of previously treated cervix cancer patients were performed to compare the DMBT brachytherapy tandem applicator to conventional brachytherapy applicators. An HDR inverse planning platform, geared with simulated annealing and constrained-gradient optimization algorithms, was used to re-plan 75 clinical cases treated with a conventional tandem & ovoids (T&O) applicator receiving a uniform prescription dose of 600 cGy to the HRCTV. For re-planning, the conventional tandem was replaced with that of the DMBT tandem for optimization, but left the ovoids in place and the dwell positions as originally planned. All DMBT plans were normalized to match the HRCTV VI 00 coverage of the original T&O plans. The Monte Carlo code was used to generate the anisotropic 192-Ir radiation profiles.

[0040] Table I lists the OAR D2cc values, averaged over 5 plans per patient, and the population-average of all 75 plans, for the Conv. T&O and DMBT plans. Paired t-test showed significant differences at the p=0.05 level between the two plans for all three OARs. For D2cc of bladder, rectum, and sigmoid; on average, 58±86 cGy (8.5±27.4%), 48±54 cGy (21.2±27.2%), 10±38 cGy (40.11212.3%) reductions were observed among 75 plans, with the best single-plan reductions of 321 cGy (40.8%), 218 cGy (37.9%), and 126 cGy (27.5%), respectively. In terms of target coverage, the HRCTV DHI was similar with 2.56+0.24 and 2.36+0.22, for the T&O and DMBT plans, respectively. In fact, the D90, D95, VI 50, and V200 values all agreed to within 3% of each other. The D5 was 52.3+11.6 Gy and 46.7+10.1 Gy for the Conv. T&O and DMBT plans, respectively. The total dwell times, normalized to a 10-Ci source strength, increased on average by 27.1 % (from 6.311.9 to 8.112.6 minutes), for the DMBT plans. This was expected, however, due to the increase in intensity modulation and the directionality of the radiation (i.e., anisotropic modulation) that accompanies the DMBT plans [18].

Table I. Individual D2cc values, averaged over each patient (5 plans per patient) and population (75 plans), for the Conv. T&O and DMBT plans. For all three OARs, the D2cc doses were significantly different at the level of p=0.05, using paired t-test. Diff. [Gy] = (DMBT - Conv. T&O). Diff. [%] = ((DMBT - Conv. T&O) / Conv. T&O). x 100%.

[0041] Table II lists the cumulative EQD2 values calculated, summed over the entire course of radiotherapy (i.e., EBRT + HDR) [2-5,13,24]. As shown, there are significant reductions in the total EQD2 D2cc doses from the Conv. T&O to DMBT plans. Of the 45 cases (15 patients x 3 OARs), 86.7% of cases (39/45) showed cumulative reductions of 413+663 cGy. In 6 cases the dose increased but minimally at 44+56 cGy. In fact, the paired t-test showed significant differences at the p=0.05 level between the two plans for all three OARs.

Table II. Individual D2cc values were converted to EQD2, using α/β = 3 Gy, then summed up over the 5 plans per patient HDR treatment course, and then added with the EQD2-converted EBRT dose of 180 cGy x 25 fxs. Therefore, the EQD2 values listed here represent what the patient would have received over the entire course of radiotherapy (i.e., EBRT + HDR Brachytherapy). Diff. [Gy] = (DMBT - Conv. T&O). Diff. [%] = ((DMBT - Conv. T&O) / Conv. T&O). x 100%. A total of 6 patients had violated the GEC-ESTRO recommended D2cc dose- volume constraints in the Conv. T&O plans (highlighted in bold and underlined), whereas only one of the patients had violations in the DMBT plans.

[0042] The DMBT tandem design is highly compatible with the traditional applicators such as the ovoids, rings, and cylinders due to the classic shape of a curved tandem with thickness no greater than a typical LDR tandem (-6-7 mm). With moderate- to-general anesthesia, typically administered during HDR treatments, the DMBT tandem may be easily inserted into the cervix. In addition, due to the high directionality of the radiation profiles, at least some of the advanced clinical cases where interstitial needles are necessary (e.g., parametrial or utero-sacral extensions) may actually become unnecessary. This will be a huge advantage to those select patients. For this reason, the previous interstitial cases are being retrospectively re-evaluated to determine the feasibility and clinical application range.

[0043] There are intrinsic difficulties when optimizing an HDR cervix plan with the classic isotropic 192-Ir radiation profile (i.e., with classic "pear shape" dose distribution). This is largely due to the non-symmetric shape of the HRCTV. Because of this, significant improvements (p<0.05) in the DMBT plans were observed in all three OARs examined with the best single-plan reductions of 321 cGy (40.8%), 218 cGy (37.9%), and 126 cGy (27.5%), for the bladder, rectum, and sigmoid, respectively. This was achieved without compromising the HRCTV coverage. Since higher brachytherapy doses and better target coverage are associated with improved local control rates, at the expense of increased rates of serious late side effects (-15 ), the DMBT applicator may allow safer dose escalations with improved target coverage. Due to the high importance of the implications, the extent of the limits may be investigated further.

[0044] In terms of CT compatibility, the shielding element may cause metal- induced artifacts that potentially obstruct manual contouring. This may be addressed by hardware solutions (e.g., increasing the X-ray energy) and software solutions (e.g., metal artifact reduction techniques) that can enhance the compatibility. Dose calculations with high-density metal presence are another potential concern to us since TG-43 formalism assumes a homogeneous water medium, thus needing a significant modification to the existing planning systems. However, with the recent introduction of model-based dose calculation algorithms (MBDCAs), heterogeneity corrections that used to be ignored are now starting to be accounted for. This may be beneficial since DMBT is entirely based on the anisotropicity of 192-Ir radiation profile. Next generation afterloader designs, which may have a 3^rd drive (or more), could also aid in the adoption of the DMBT treatment paradigm as the 3^rd drive (or more) may have an intelligently-designed shielding attached that can move in combination with an 192-Ir source, for example, thus creating anisotropic modulation tailored for individual patient anatomy. Such a concept does not only complement the up-and-coming trend of 3D-imaging-based brachytherapy planning, and with dose-volume-driven objectives, but is an intuitively natural progression that was already observed in the EBRT world, i.e., transition from the 3DCRT to IMRT for improved dose conformality in 3D target volumes.

[0045] Application of the DMBT tandem applicator (i.e., anisotropic modulation) to cervical cancer allowed for improved OAR sparing whilst achieving similar target coverage on a sizeable patient population. The technology is designed to maximally utilize the abundant anatomical information contained in 3D imaging, in IGABT, in fittingly aligned with the latest dose- volume-driven brachytherapy planning trend.

Example Embodiment - Breast Cancer

[0046] FIG. 5 depicts and example embodiment of a brachytherapy applicator 500 that may be used herein to treat breast cancer. The DMBT brachytherapy applicator may include a 9 mm diameter tungsten rod (p=19.0 g/cc) having 8 grooves along the edge to allow one or more radioactive sources to be slide therein. In addition, the brachytherapy applicator may include a central channel placed within the shield to allow a single dwell position that is located at the distal end of the tungsten rod/cavity to help treat the end-cap of the PTV. The elongated intracavitary applicator may be slide in and out of the lumpectomy cavity tunnel/scar opening (which is generally about 10-12 mm wide). The balloon may be inflated around the elongated intracavitary applicator to expand the cavity tissue outwards. Due to the 3-piece design, in some instances, only the balloon-lexan tubing will need to be in the patient during CT, MRI, and/or US treatment simulations to eliminate metal-induced imaging artifacts. The tungsten rod and the locking mechanism will only need be inserted/connected just before the treatment. This way, the patients will have the convenience of carrying only the balloon-lexan tubing in the cavity during the course of therapy, which only sticks out less than 1 cm from the breast in some isntances. This is an advantage compared with the other devices, where the entire lengths of the devices stick out from skin greater than 10 cm, limiting patient mobility, comfort, and convenience.

[0047] As depicted in FIG. 11 , DMBT significantly decreased the VI 50 (31 % from SAVI™) and V200 (9% from SAVI™) while maintaining the V90 target coverage. Except the increase in the total dwell times (4.09 minutes for a 10 Ci source, -50% increase), all variables are most favorable for DMBT. The increase in the dwell times are expected since the radiation profile is directional, and hence, do not contribute dose to opposite sides, which is the primary reason why high dose modulation is possible in the first place. OAR is also significantly spared (D_mean decrease of 12.4% from SAVI™). This certainly reduces pectoralis muscle and skin dose, without sacrificing the V90 coverage. To spare OAR to the level of DMBT, SAVI™ must need to sacrifice V90.

Claims

What is claimed is:

1. A brachythera y applicator, comprising:

an elongated intracavitary applicator;

a plurality of channels disposed within the elongated intracavitary applicator; and

at least one shielding element;

wherein the plurality of channels are configured to receive at least one radioactive element therein to selectively generate an anisotropic directional radiation profile for the treatment of cancer.

2. The brachytherapy applicator 1 , wherein the plurality of channels are formed about a periphery of the elongated intracavitary applicator.

3. The brachytherapy applicator 1, wherein the plurality of channels are arranged in an array across a cross-section of the elongated intracavitary applicator.

4. The brachytherapy applicator 3, wherein the at least one shielding element is configured to be positioned within the plurality of channels surrounding the at least one radioactive element.

5. The brachytherapy applicator 1 , wherein the anisotropic directional radiation profile is selectively configured to create a desired and optimal dose distribution and conformality by positioning the at least one radioactive element and a plurality of the shielding elements in multiple radial patterns.

6. The brachytherapy applicator 1 , wherein the elongated intracavitary applicator is configured to provide anisotropic radiation treatment for breast cancer, rectal cancer, or cervical cancer.

7. The brachytherapy applicator 1 , wherein the at least one shielding element comprises tungsten or gold.

8. The brachytherapy applicator 1, wherein the at least one radioactive element comprises 192-Ir.

9. The brachytherapy applicator 1 , wherein the anisotropic directional radiation profile increases conformality of dose distributions when combined with dwell positions and times.

10. The brachytherapy applicator 1 , further comprising a balloon positioned about a distal end of the elongated intracavitary applicator for insertion and placement inside a lumpectomy cavity.

11. The brachytherapy system 10, wherein the balloon is configured to be filled with water to expand the lumpectomy cavity.

12. A brachytherapy applicator, comprising:

an elongated intracavitary applicator;

a shielding element disposed within the elongated intracavitary applicator; and

a plurality of channels formed about a periphery of the shielding element; wherein the plurality of channels are configured to receive at least one radioactive element therein to generate an anisotropic directional radiation profile for the treatment of cancer.

13. The brachytherapy applicator 12, further comprising a balloon positioned about a distal end of the elongated intracavitary applicator for insertion and placement inside a lumpectomy cavity.

14. The brachytherapy applicator 12, wherein the plurality of channels form a circumferential array about the shielding element.

15. The brachytherapy applicator 12, wherein the plurality of channels comprise six or more channels.

16. A brachytherapy applicator, comprising:

an elongated intracavitary applicator;

a plurality of channels disposed within the elongated intracavitary applicator; and

at least one elongated shielding element;

wherein at least one elongated radioactive element or the at least one elongated shielding element are selectively positionable within each of the plurality of channels within the elongated intracavitary applicator to generate an anisotropic directional radiation profile for the treatment of cancer.

17. The brachytherapy applicator 16, further comprising a balloon positioned about a distal end of the elongated intracavitary applicator for insertion and placement inside a lumpectomy cavity.

18. The brachytherapy applicator 16, wherein the plurality of channels comprise at least 12 channels.