1. Field of the Invention
The present invention relates to rectal balloons that are used for immobilizing the region surrounding the prostate.
2. Description of the Related Art
Treatment of prostate cancer using radiation therapy is difficult due to the prostate's position near radiation-sensitive tissues, and is further complicated by prostate motion. Adenocarcinoma of the prostate commonly occurs in the posterior portion of the prostate gland, which is in very close proximity to the rectal wall. To date, external beam radiation treatment, urethrograms, CT scans and magnetic resonance imaging (MRI) have all been used to visually localize the prostate, as well as the normal critical structures in the surrounding area.
U.S. Pat. No. 5,476,095, issued on Dec. 19, 1995 to Schnall et al., proposes an insertable pickup probe for use in providing diagnostic MRI images. The pickup probe, in its preferred embodiment, is proposed for use in imaging the male prostate and comprises an elongated shaft supporting an inflatable patient interface balloon at its distal end. The interface balloon comprises an inner balloon and an outer balloon, between which a receiving coil is positioned. A lumen for air supply is provided in the shaft for expanding the inner balloon against the outer balloon to place the receiving coil in close proximity to the area of interest in order to provide MRI images.
Typically, the planning of radiation therapy for the treatment of prostate cancer involves the patient undergoing a CT-based simulation scan of the pelvis to determine the location of the prostate gland. In the simulation phase, the patient is placed on CT equipment that is preferably similar to the radiation treatment equipment (except that it does not generate the high energy radiation beam). The simulation equipment is positioned to simulate the delivery of the sequence of treatment beams prescribed by the treating oncologist. Normally, during the simulation procedure, CT images are acquired. These CT images allow the oncologist to locate the position of the tumor and help to facilitate the composition of a radiation treatment plan. This treatment plan delineates the positions of the radiation equipment components for delivery of the treatment beams.
During the actual treatment phase, the patient is placed in the same position on the treatment equipment as in the simulation scans. Radiation-emitting devices are generally known and used for radiation therapy in the treatment of patients. Typically, a radiation therapy device includes a gantry, which can be swiveled around a horizontal axis of rotation in the course of a therapeutic treatment. A linear accelerator is located in the gantry for generating a high-energy radiation beam for therapy. During treatment, the radiation beam is provided by this equipment and is delivered to the patient at the precise location as delineated by the physician during simulation. A further feature of radiation therapy involves portal images, which are commonly used in radiation therapy to verify and record the patient tumor location. Portal images include manual (film) and electronic images (EPI) taken before and/or after the treatment.
During external beam radiation therapy, radiation is directed to the target prostate which is near the rectal wall. A misdirected radiation beam may perforate the rectal wall causing radiation proctitus (rectal bleeding). This toxicity is related to the total radiation dose prescribed and the volume of the anterior rectal wall receiving a high radiation dose. A major factor limiting radiation oncologists' attempts to reduce the volume of the anterior rectal wall receiving a high radiation dose is the position of the prostate gland as well as the intrinsic motion up to 5 mm in the anterior to posterior direction caused by rectal peristalsis. Accordingly, oncologists generally will add a margin to the radiation field in order to ensure that the entire prostate gland receives the prescription dose. This margin is typically on the order of 5 to 15 mm. As a consequence, lower doses of radiation may need to be used so as not to overexpose radiation sensitive structures. However, this may lead to inadequate radiation treatment and a higher probability of local cancer recurrence.
U.S. Patent Publication No. 2003/0028097, published on Feb. 6, 2003 to D'Amico et al., proposes an insertable probe for immobilizing a region of interest during staging and radiation therapy thereof. In particular, a balloon is proposed having a rectangular cross section connected to a shaft. The shaft extends to an end of the balloon so as to allow fluid flow through an interior of the shaft and into the balloon so as to selectively inflate the balloon once the balloon is installed into the rectal cavity. The balloon, shaft and handle are bonded together so that they move radially as a single unit when torque is applied. A syringe is provided which connects the shaft and serves as an air pump to deliver a volume-limited amount of air to the air lumen of the shaft to the balloon. A stop cock is provided to maintain the air within the balloon.
One of the problems with the subject of U.S. Patent Publication No. 2003/0028097 is the discomfort associated with installing the rectal balloon within the rectal cavity. In particular, a relatively sturdy and wide diameter shaft is connected to a relatively large thick-walled balloon. Because the balloon is not supported by anything other than by the shaft, the balloon is formed of a relatively rugged and thick material. Because of the relatively large size of the shaft and the thick material of the rectangular-cross section balloon, the installation of the rectal balloon creates a large amount of discomfort for a patient. It is often difficult for the medical personnel to know exactly how far within the rectum the balloon has been installed. It is difficult to achieve a standardized and fixed position of the balloon during each and every use. The medical personnel must generally approximate the desired position of the balloon within the rectal cavity. As such, a need has developed whereby the rectal balloon can be formed of a minimal diameter shaft and of a balloon of relatively thin material.
When the rectal balloon of U.S. Patent Publication No. 2003/0028097 is in an inflated condition, the outer surface is generally round. As such, the prostate will tend to balance on the curved surface rather than be properly seated thereon. Since seating is important for proper use, this device requires that the physician approximate a seated position rather than providing any feedback of the seated position. When the balloon is in a curved inflated condition, the prostate will have a tendency to slide to one side of the balloon. As such, a need developed to provide a rectal balloon that retains the prostate in a proper seated position when the balloon is in a fully inflated condition.
As discussed above, a very important consideration when treating patients using radiation therapy is that the proper dose of radiation reaches the treatment site. This is very important whether the treatment method utilizes implanted radiation seeds or external beams of radiation. Excessive dosing of the patient can lead to severe side effects including impotence and urinary incontinence. A proper treatment plan should deliver an adequate amount of radiation to the treatment site while minimizing the dose delivered to the surrounding tissues.
U.S. Pat. No. 6,963,771, issued on Nov. 8, 2005 to Scarantino et al., describes a method, system and implantable device for radiation dose verification. The method includes (a) placing at least one wireless implantable sensor in a first subject at a target location; (b) administering a first dose of radiation therapy into the first subject; (c) obtaining radiation data from the at least one wireless implantable sensor; and (d) calculating a radiation dose amount received by the first subject at the target location based on the radiation data obtained from the at least one wireless sensor during and/or after exposure to the first administered dose of radiation to determine and/or verify a dose amount of radiation delivered to the target location.
U.S. Pat. No. 7,361,134, issued on Apr. 22, 2008 to Rozenfeld et al., proposes a method of determining the dose rate of a radiation source including locating three or more detectors in the vicinity of a source. Each of the detectors provides an output indicative of the amount of radiation received from the source and determines the location of the source from at least some of the detector outputs. International Pub. No. WO 2008/148150, published on Dec. 11, 2008 to Rozenfeld, proposes a semiconductor radiation sensor.
U.S. Patent Publication No. 2009/0236510, published on Sep. 24, 2009 to Lacroix et al., proposes a radiation dosimeter for measuring a relative dose of a predetermined radiation type within a detection region by using a plurality of scintillating optical fibers. U.S. Patent Publication No. 2006/0094923, published on May 4, 2006 to Mate, proposes a marker comprising a wireless transponder configured to wirelessly transmit a location signal in response to a wirelessly transmitted excitation energy.
A significant cause of patient discomfort associated with rectal balloons of the prior art is the buildup of gas pressure when the balloon is inserted into the rectum. This buildup of gas pressure can also affect the ability to properly seat the balloon in a desired position.
The above discussed U.S. Pat. Nos. 5,476,095; 6,963,771; and 7,361,134; and Pub. Nos. U.S. 2003/0028097; 2006/0094923; and 2009/0236510; and International Pub No. WO 2008/148150 are hereby incorporated by reference for all purposes in their entirety.
A need exists for a rectal balloon apparatus that relieves rectal gas pressure prior to or during inflation of the balloon. A need also exists for a rectal balloon apparatus that senses the amount of radiation received at or near a treatment site, and that also detects the motion of the rectal balloon apparatus and/or the means used by the apparatus to sense the radiation.