Patent Publication Number: US-2021186472-A1

Title: Tissue removal system

Description:
RELATED APPLICATION DATA 
     The present application is a continuation of U.S. patent application Ser. No. 15/915,409, filed Mar. 8, 2018, now issued as U.S. Pat. No. 10,874,380, which is a continuation of U.S. patent application Ser. No. 15/556,599, filed Sep. 7, 2017, now issued as U.S. Pat. No. 9,913,629, which is a National Phase entry under 35 U.S.C § 371 of International Patent Application No. PCT/US2016/062080, having an international filing date of Nov. 15, 2016, which claims the benefit under 35 U.S.C. § 119 to U.S. provisional patent application Ser. No. 62/255,650, filed Nov. 16, 2015. The foregoing applications are hereby incorporated by reference into the present application in their entirety. 
    
    
     FIELD 
     The disclosure relates generally to methods, systems and devices for surgical procedures, and relates more particularly to tissue removal systems for the removal of body tissues, including uterine polyps and other abnormal gynecological tissues. 
     BACKGROUND 
     There are many situations in which it is desirable to remove unwanted tissue from a patient. Uterine polyps and uterine fibroids represent two such types of unwanted tissue. Uterine polyps are wispy masses that are commonly found extending from the inner lining of the uterus. Uterine fibroids are well-defined, non-cancerous tumors that are commonly found in the smooth muscle layer of the uterus. In many instances, uterine polyps and uterine fibroids can grow to be several centimeters in diameter and may cause symptoms like menorrhagia (prolonged or heavy menstrual bleeding), pelvic pressure or pain, and reproductive dysfunction. It is believed that uterine polyps occur in up to 10 percent of all women, and that uterine fibroids occur in a substantial percentage of the female population, perhaps in at least 20 to 40 percent of all women. 
     One type of treatment for uterine polyps and uterine fibroids is hysteroscopic resection. Hysteroscopic resection typically involves inserting a hysteroscope (i.e., an imaging scope) into the uterus through the vagina, i.e., transcervically, and then cutting away the unwanted tissue from the uterus using a device delivered to the unwanted tissue by or through the hysteroscope. Hysteroscopic resections typically fall into one of two varieties. 
     In one variety, an electrocautery device in the form of a loop-shaped cutting wire is fixedly mounted on the distal end of the hysteroscope. The combination of the hysteroscope and the electrocautery device is typically referred to as a resectoscope. The transmission of electrical current to the uterus with a resectoscope is typically monopolar, and the circuit is completed by a conductive path to the power unit for the device through a conductive pad applied to the patient&#39;s skin. In this manner, tissue is removed by contacting the loop with the part of the uterus wall of interest. Examples of such devices are disclosed, for example, in U.S. Pat. No. 5,906,615, issued May 25, 1999, the contents of which are fully incorporated herein by reference as though set forth in full. 
     In the other variety of hysteroscopic resection, an electromechanical cutter is inserted through a working channel in the hysteroscope. The electromechanical cutter typically includes (i) a tubular member having a window through which tissue may enter and (ii) a cutting instrument positioned within the tubular member for cutting the tissue that has entered the tubular member through the window. In use, a distal portion of the electromechanical cutter is positioned near the part of the uterus wall of interest. Tissue is then drawn, typically by suction, into the window, and then the tissue drawn into the window is cut with the cutting instrument. Examples of the electromechanical cutter variety of hysteroscopic resection are disclosed in, for example, U.S. Pat. No. 9,060,760, issued Jun. 23, 2015; U.S. Pat. No. 8,062,214, issued Nov. 22, 2011; U.S. Pat. No. 7,226,459, issued Jun. 5, 2007; U.S. Pat. No. 6,032,673, issued Mar. 7, 2000; U.S. Pat. No. 5,730,752, issued Mar. 24, 1998; U.S. Patent Application Publication No. US 2009/0270898 A1, published Oct. 29, 2009; U.S. Patent Application Publication No. US 2009/0270812 A1, published Oct. 29, 2009; and PCT International Publication No. WO 99/11184, published Mar. 11, 1999, the contents of all of which are fully incorporated herein by reference as though set forth in full. 
     In both of the above-described varieties of hysteroscopic resection, prior to tissue removal, the uterus is typically distended to create a working space within the uterus. Such a working space typically does not exist naturally in the uterus because the uterus is a flaccid organ. As such, the walls of the uterus are typically in contact with one another when in a relaxed state. The conventional technique for creating such a working space within the uterus is to administer a fluid to the uterus through the hysteroscope under sufficient pressure to cause the uterus to become distended. Examples of the fluid used conventionally to distend the uterus include gases like carbon dioxide or, more commonly, liquids like water or certain aqueous solutions (e.g., a saline or other physiologic solution or a sugar-based or other non-physiologic solution). For instance, a 3 L bag of saline connected to a uterus (e.g., through a hysteroscope) can generate uterine distension pressure 50-60 mm of Hg. 
     One of the benefits of fluid distension is the tamponade effect that the distension fluid provides on resected vascular tissue. Since the distension fluid is typically maintained at a pressure that exceeds the patient&#39;s mean arterial pressure (MAP), the fluid pressure provided by the distension fluid prevents the leakage of arterial blood from the resected tissue from flowing or oozing into the uterine cavity. When arterial blood flows or oozes into the cavity, it mixes with the distension fluid and renders visualization more difficult and, if not constrained, the flowing or oozing blood will force the suspension of the procedure. Thus, maintenance of fluid pressure above the intracavity arterial pressure facilitates the maintenance of a clear visual field. 
     Nevertheless, one shortcoming with existing hysteroscopic tissue removal systems, particularly of the electromechanical cutter variety, is that it is often difficult to maintain fluid distension of the uterus during the resection procedure. This is because such systems typically employ a vacuum source that continuously subjects the electromechanical cutter to suction, even when the cutting mechanism of the electromechanical cutter is not switched on. The purpose of such suction is to draw tissue into the cutter, typically through the window, and to facilitate the removal of resected tissue from the uterus. However, such suction also typically has the unwanted effect of removing some of the distending fluid from the uterus along with the resected tissue. Moreover, because suction is continuously applied to the cutter, even when the cutting mechanism is not being operated, fluid tends to be continuously removed from the uterus whenever the cutter is inserted into the patient. If such fluid cannot be replenished quickly enough, the fluid pressure within the uterus may drop to an undesired level. In particular, a steep drop in uterine fluid pressure will result in the leakage of blood into the uterine cavity, causing a loss of visualization and ultimately stoppage of the procedure if the surgeon can no longer properly visualize the treatment site. Moreover, depending on the extent and speed of the drop in uterine fluid pressure, there may be a significant lapse of time before the uterine fluid pressure can be restored to a desired level such that adequate visualization is possible. Such lapses in time are clearly undesirable as they interrupt the resection procedure, as well as lengthen the overall time for the procedure and increase the risk that distending fluid may be taken up by a blood vessel in the uterus, i.e., intravasation, which uptake may be quite harmful to the patient. 
     One approach to the above problem has been to provide the electromechanical cutter with a mechanism actuated by an electrical switch that causes the window in the cutter to be closed off when the cutting mechanism is turned off. In this manner, when the cutting mechanism is switched off, only a minimal amount of distension fluid can escape from the uterus through the resection window of the cutter, and adequate uterine fluid pressure may be maintained. Unfortunately, the cost of the above-described electromechanical cutters may be prohibitive for certain procedures, such as polypectomies, for which the costs covered by most insurers are typically relatively low. 
     SUMMARY 
     In accordance with one embodiment, a tissue removal device for acquiring one or more samples of intrauterine tissue from a patient includes a housing. The device also includes an outer tube having a distal portion configured for transcervical insertion into a uterus, the outer tube having an outer tube lumen, a tissue in-take opening proximate a distal end thereof, and a proximal end coupled to the housing. The device further includes an inner tube slidably disposed within the outer tube lumen, the inner tube having an inner tube lumen extending from an open inner tube distal end to an open inner tube proximal end, the open inner tube distal end comprising a cutting edge configured to sever intrauterine tissue extending through the tissue in-take opening in the outer tube. Moreover, the device includes a vacuum generation chamber disposed within the housing. In addition, the device includes a movable piston slidably disposed in the vacuum generation chamber so that the piston forms a wall of the vacuum chamber. The inner tube lumen is selectively placed in fluid communication with the vacuum generation chamber via a distal one-way valve, the distal one-way valve being oriented so that material located in the inner tube lumen may be aspirated from the inner tube lumen into the vacuum generation chamber in response to movement of the piston in a distal direction, while material in the vacuum generation chamber is prevented by the distal one-way valve from entering the inner lumen. The device also includes a collection chamber. The vacuum generation chamber is selectively placed in fluid communication with the collection chamber via a proximal one-way valve, the proximal one-way valve being oriented so that material located in the vacuum generation chamber may be expelled from the vacuum generation chamber into the collection chamber in response to movement of the piston in a proximal direction, while material in the collection chamber is prevented from entering the vacuum generation chamber. The device further includes a manual actuator moveably coupled to the housing and operatively coupled to the piston, wherein movement of the actuator relative to the housing causes movement of the piston within the vacuum generation chamber. 
     In one or more embodiments, the in-take opening is a side facing opening relative to the outer tube. The distal one-way valve may be opened when the piston is moved in the distal direction and sealed when the piston is moved in the proximal direction. The proximal one-way valve may be opened when the piston is moved in the proximal direction and sealed when the piston is moved in the distal direction. The material may be intrauterine tissue or fluid from within the uterus. The proximal and distal one-way valves may be duck-billed valves. 
     In one or more embodiments, the device also includes a porous filter trap in selective fluid communication with the vacuum generation chamber, the porous filter trap configured to separate excised intrauterine tissue from fluid. The porous filter trap may be contained in the collection chamber. The porous filter trap may be selectively fluidly coupled to the vacuum generation chamber by the proximal one-way valve, so that material may pass from the vacuum generation chamber to the porous filter trap in response to movement of the piston in a proximal direction. The porous filter trap may be integrally formed. The device may also include a trap housing configured to releasably secure the porous filter trap onto the housing. The outer tube may include an edge adjacent the tissue in-take opening configured to facilitate collection of intrauterine tissue adjacent the tissue in-take opening. When the actuator is fully actuated, a volume of the vacuum generation chamber may be about three times a volume of the inner tube lumen. 
     In one or more embodiments, the proximal and distal one-way valves are configured such that, when the piston is not moving and the uterus is distended by distension fluid, both the proximal and distal one-way valves are open under pressure from the distension fluid. The proximal and distal one-way valves may be configured such that, when the piston is not moving and the uterus is distended by distension fluid, the distension fluid flows through the proximal and distal one-way valves. The distension fluid may urge intrauterine tissue through the tissue in-take opening and into an outer tube lumen. The proximal and distal one-way valves may each have a cracking pressure of about 40 mm Hg and the distension fluid may generate a distension pressure between about 50 mm Hg and about 60 mm Hg. The distal one-way valve may be at least partially formed in the piston. 
     In one or more embodiments, the device also includes a valve configured to selectively couple the inner tube lumen with a vacuum source external to the housing. The valve may be a pinch valve. 
     In one or more embodiments, the manual actuator may be operatively coupled to the inner tube such that movement of the actuator relative to the housing causes longitudinal movement of the inner tube within the outer tube lumen. The device may also include a cam and a cam follower operatively coupled to the inner tube and the housing such that movement of the actuator relative to the housing causes longitudinal and rotational movement of the inner tube within the outer tube lumen. The cam may be fixed to the inner tube and the cam follower may be fixed to the housing. The cam may be fixed to the housing and the cam follower may be fixed to the inner tube. 
     In one or more embodiments, the device also includes a yoke selectively coupling the manual actuator to the inner tube. When the manual actuator is coupled to the inner tube, movement of the actuator relative to the housing causes longitudinal movement of the piston within the vacuum generation chamber and the inner tube within the outer tube lumen. When the manual actuator is uncoupled from the inner tube, longitudinal movement of the actuator relative to the housing causes the piston within the vacuum generation chamber without longitudinal movement of the inner tube within the outer tube lumen. The device may include a knob configured to rotate the outer tube relative to the housing to change a circumferential position of the opening. 
     In accordance with one embodiment, a tissue removal device for acquiring one or more samples of intrauterine tissue from a patient includes a housing. The device also includes an outer tube having a distal portion configured for transcervical insertion into a uterus, the outer tube having an outer tube lumen, a tissue in-take opening proximate a distal end thereof, and a proximal end coupled to the housing. The device further includes an inner tube slidably disposed within the outer tube lumen, the inner tube having an inner tube lumen extending from an open inner tube distal end to an open inner tube proximal end, the open inner tube distal end comprising a cutting edge configured to sever intrauterine tissue extending through the tissue in-take opening in the outer tube. Moreover, the device includes a vacuum generation chamber disposed within the housing. In addition, the device includes a bellows disposed within the housing and having a movable wall and a vacuum generation chamber. The inner tube lumen is selectively placed in fluid communication with the vacuum generation chamber via a distal one-way valve, the distal one-way valve being oriented so that material located in the inner tube lumen may be aspirated from the inner tube lumen into the vacuum generation chamber in response to movement of the wall of the bellows in a distal direction, while material in the vacuum generation chamber is prevented by the distal one-way valve from entering the inner lumen. The device also includes a collection chamber. The vacuum generation chamber is selectively placed in fluid communication with the collection chamber via a proximal one-way valve, the proximal one-way valve being oriented so that material located in the vacuum generation chamber may be expelled from the vacuum generation chamber into the collection chamber in response to movement of the wall of the bellows in a proximal direction, while material in the collection chamber is prevented from entering the vacuum generation chamber. The device further includes a manual actuator moveably coupled to the housing and operatively coupled to the wall of the bellows, wherein movement of the actuator relative to the housing causes movement of the wall of the bellows within the vacuum generation chamber. In one or more embodiments, the wall of the bellows is a distal wall. 
     Additional objects, as well as aspects, features and advantages, of the disclosure are set forth in part in the description which follows, and in part will be obvious from the description or may be learned by practice of the invention. In the description, reference is made to the accompanying drawings which form a part thereof and in which is shown by way of illustration various embodiments for practicing the invention. The embodiments will be described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the disclosed inventions. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the disclosure is best defined by the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings illustrate the design and utility of embodiments of the disclosed inventions, in which similar elements are referred to by common reference numerals. These drawings are not necessarily drawn to scale. In order to better appreciate how the above-recited and other advantages and objects are obtained, a more particular description of the embodiments will be rendered, which are illustrated in the accompanying drawings. These drawings depict only typical embodiments of the disclosed inventions and are not therefore to be considered limiting of its scope. 
         FIG. 1  is a side view of a first embodiment of a tissue removal device constructed according to the teachings of the disclosure, with an actuator of the tissue removal device in an un-actuated state, and with a portion of a housing removed; 
         FIG. 2  is a side view of the tissue removal device depicted in  FIG. 1 , with the actuator of the tissue removal device in an actuated state, and with a portion of the housing removed; 
         FIG. 3  is a detailed cross-sectional side view of respective distal ends of outer and inner tubular members of the tissue removal device depicted in  FIG. 1 , with the actuator of the tissue removal device in an un-actuated state. 
         FIG. 4  is a detailed cross-sectional side view of respective distal ends of outer and inner tubular members of the tissue removal device depicted in  FIG. 1 , with the actuator of the tissue removal device in an actuated state. 
         FIG. 5  is a side view of a second embodiment of a tissue removal device constructed according to the teachings of the disclosure, with an actuator of the tissue removal device in an un-actuated state; 
         FIGS. 6-8  are increasingly detailed cross-sectional side views of the tissue removal device depicted in  FIG. 5 , with the actuator of the tissue removal device in an un-actuated state; 
         FIG. 9  is a detailed cross-sectional side view of the tissue removal device depicted in  FIG. 5 , with the actuator of the tissue removal device in an actuated state; 
         FIG. 10  is a side view of the tissue removal device depicted in  FIG. 5 , with the actuator of the tissue removal device in an un-actuated state; 
         FIGS. 11 and 12  are increasingly detailed perspective views of the tissue removal device depicted in  FIG. 5  showing a tissue trap housing, with the actuator of the tissue removal device in an un-actuated state; 
         FIG. 13  is a detailed cross-sectional side view of respective distal ends of outer and inner tubular members of the tissue removal device depicted in  FIG. 5 , with the actuator of the tissue removal device in an un-actuated state. 
         FIG. 14  is a detailed cross-sectional side view of respective distal ends of outer and inner tubular members of the tissue removal device depicted in  FIG. 5 , with the actuator of the tissue removal device in an actuated state. 
         FIGS. 15 and 16  are detailed perspective views of distal ends of the outer tubular members of tissue removal devices according to two embodiments. 
         FIGS. 17 and 18  are increasingly detailed cross-sectional side views of a third embodiment of a tissue removal device constructed according to the teachings of the disclosure showing a motion conversion system, with an actuator of the tissue removal device in an un-actuated state; 
         FIG. 19  is a detailed perspective view of the tissue removal device depicted in  FIGS. 17 and 18  showing the motion conversion system, with the actuator of the tissue removal device in an un-actuated state. 
         FIGS. 20 and 21  are detailed cross-sectional side views of a fourth embodiment of a tissue removal device constructed according to the teachings of the disclosure showing a bellows, with an actuator of the tissue removal device in un-actuated and actuated states, respectively. 
     
    
    
     DETAILED DESCRIPTION 
     For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification. 
     All numeric values are herein assumed to be modified by the term “about,” whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skilled in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the terms “about” may include numbers that are rounded to the nearest significant figure. 
     The recitation of numerical ranges by endpoints includes all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5). 
     As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise. 
     As used in this application, a “tubular member” is any elongate device having a lumen. The lumen may extend the entire length of the elongate device (i.e., from a first end to a second, opposite end), or the lumen may extend less than the entire length of the elongate device. A tubular member can be formed from any material, including, but not limited to, metals and polymers. While the tubular members described herein have substantially circular cross-sectional geometry, tubular members may have any cross-sectional geometry, including one that changes along the longitudinal axis of the device. Therefore, uses of terms that connote circular geometry, such as “radius,” “diameter,” “circumference,” and “annular,” are illustrative, and not intended to be limiting. Accordingly, such terms are intended to include analogous concepts in tubular members having non-circular geometries. 
     Conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or steps. Thus, such conditional language is not generally intended to imply that features, elements and/or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without user input or prompting, whether these features, elements and/or steps are included or are to be performed in any particular embodiment. The headings used herein are for the convenience of the reader only and are not meant to limit the scope of the inventions or claims. 
     Various embodiments are described hereinafter with reference to the figures. The figures are not necessarily drawn to scale, the relative scale of select elements may have been exaggerated for clarity, and elements of similar structures or functions are represented by like reference numerals throughout the figures. It should also be understood that the figures are only intended to facilitate the description of the embodiments, and are not intended as an exhaustive description of the invention or as a limitation on the scope of the invention, which is defined only by the appended claims and their equivalents. In addition, an illustrated embodiment needs not have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced in any other embodiments even if not so illustrated. 
     The disclosure is described below primarily in the context of devices and procedures optimized for performing one or more therapeutic or diagnostic gynecological or urological procedures such as the removal of uterine polyps or other uterine tissue. However, the devices and related procedures of the disclosure may be used in a wide variety of applications throughout the body, through a variety of access pathways. 
     For example, the devices of the disclosure can be optimized for use via open surgery, less invasive access such as laparoscopic access, or minimally invasive procedures such as via percutaneous access. In addition, the devices of the disclosure can be configured for access to a therapeutic or diagnostic site via any of the body&#39;s natural openings to accomplish access via the ears, nose, mouth, and via trans-rectal, urethral and vaginal approach. 
     In addition to the performance of one or more gynecological and urologic procedures described in detail herein, the systems, methods, apparatus and devices of the disclosure may be used to perform one or more additional procedures, including, but not limited to, access to and tissue manipulation or removal from any of a variety of organs such as the bladder, breast, lung, stomach, bowel, esophagus, oral cavity, rectum, nasal sinus, Eustachian tubes, heart, gall bladder, arteries, veins, and various ducts. Routes of access include but are not limited to trans-cervical; trans-vaginal-wall; trans-uteral; trans-vesicle; trans-urethral; and other routes. 
       FIGS. 1-4  illustrate an embodiment of a tissue removal device  100  in respective un-actuated ( FIGS. 1 and 3 ) and actuated ( FIGS. 2 and 4 ) states (described below). The tissue removal device  100  includes manually operated assemblies (also described below) for creating vacuum and for cutting tissue. As used in this application, “vacuum” includes but is not limited to, a pressure differential sufficient to move material (e.g., excised tissue and fluid) from one space to another space. As such, the tissue removal device  100  is capable of performing a tissue removal procedure (e.g., a polypectomy) with no external vacuum or power sources, and is therefore a “tetherless” or “non-tethered” device. This is in contrast to “tethered” tissue removal devices, which require various external power sources, motors, and/or vacuums to perform tissue removal procedures. 
     The tissue removal device  100  includes a housing  102  having a proximal end  104  and a distal end  106 . The tissue removal device  100  also includes an outer tubular member  108  having a proximal end  110  rotatably coupled to the distal end  106  of the housing  102  and a distal end  112  having a proximal tissue receiving window/tissue in-take opening  114 , as best shown in  FIGS. 3 and 4 . The outer tubular member  108  also includes a grip/rotator/knob  116  configured to facilitate user rotation of the rotatably coupled outer tubular member  108 . The rotator  116  is disposed adjacent and fixed to the proximal end  110  of the outer tubular member  108 . In this manner, the outer tubular member  108  is configured to selectively rotate relative to the housing  102  in response to manipulation of the rotator  116  to alter the circumferential position of the tissue receiving window  114 . The tissue removal device  100  further includes an inner tubular member  118  configured for axial movement within an outer tubular member lumen  148  in the outer tubular member  108 , as shown in  FIGS. 3 and 4 . The outer and inner tubular members  108 ,  118  can be either flexible or rigid. 
     The outer tubular member  108  may be configured for transcervical insertion. Additionally or alternatively, the outer tubular member  108  may be configured for insertion through a working channel of an endoscopic instrument so that the tissue receiving window  114  is disposed in an interior region of a patient&#39;s body. The distal end  112  of the outer tubular member  108  may be conformable or rigid. The inner tubular member  118  is hollow, and includes an open proximal end, an open distal end  122 , and an inner tubular member lumen  150  (see  FIGS. 3 and 4 ) extending between the open proximal end  120  and the open distal end  122 . The distal end  122  of the inner tubular member  118  includes a cutting edge  124  (e.g., annular) for severing tissue projecting into the tissue receiving window  114  as the inner tubular member  118  moves past the tissue receiving window  114  (see  FIGS. 3 and 4 ). 
     The tissue removal device  100  also includes a manually operated actuator, or trigger  126  rotatably coupled to the housing  102  by a pinned connection  130 , which acts as a pivot point, such that the trigger  126  is configured to rotate about the pinned connection  130 . The trigger  126  includes a first end  132  disposed inside of the housing  102 , and a second end  134  disposed outside of the housing  102 . The trigger  126  is rotatably coupled to the housing  102  such that a user may hold the housing  102  in one hand and actuate the trigger  126  by squeezing the second end  134  of the trigger  126  toward the housing  102 . Actuating the trigger  126  by squeezing rotates the second end  134  of the trigger  126  toward the housing  102  about the pivot point formed by the pinned connection  130 . A spring  128  is configured to bias the second end  134  of the trigger  126  away from the housing  102 , as shown in  FIG. 1 . As a result, when the trigger  126  is released after being actuated, the spring  128  restores the second end  134  of the trigger  126  to its un-actuated position away from the housing  102 . The spring  128  may be coupled to the housing  102  and the first end  132  of the trigger  126 . It should be understood that the individual components of the device  100  illustrated in  FIGS. 1-4  are not necessarily drawn to scale. Further,  FIGS. 1-4  are provided to illustrate the principles of the disclosed embodiments, and are not intended to be limiting. 
     The first end  132  of the trigger  126  is coupled to a piston/plunger  136 , which forms a movable distal wall of a vacuum generation chamber  138 , thereby enabling the vacuum generation chamber  138  to change its volume with movement of the piston/plunger  136 . Actuating the trigger  126  rotates the first end  132  of the trigger  126  about the pinned connection  130 , and moves the piston  136  relative to a proximal wall of the vacuum generation chamber  138 . In particular, actuating the second end  134  of the trigger  126  toward the housing  102  causes the piston  136  to be pulled distally away from the proximal wall of the vacuum generation chamber  138 , thereby increasing the volume of the vacuum generation chamber  138  and reducing the pressure therein to generate vacuum, as shown in  FIG. 2 . In one embodiment, when the trigger  126  is fully actuated (i.e., moved maximally toward the housing  102 ), a volume of the vacuum generation chamber  138  is increased to about three times a volume of the inner tubular member lumen  150 . In some embodiments, this volume ratio optimizes vacuum generation and tissue travel through the inner tubular member lumen  150 , and minimizes tissue clogging therein. 
     Releasing the trigger  126  allows the spring  128  to restore the second end  134  of the trigger  126  to its un-actuated position away from the housing  102 . When the trigger  126  is restored to its un-actuated position, the piston  136  is pushed proximally toward the proximal wall of the vacuum generation chamber  138 , thereby decreasing the volume of the vacuum generation chamber  138  and increasing the pressure therein, as shown in  FIG. 1 . 
     The proximal end  120  of the inner tubular member  118  may be fluidly coupled to and/or form part of the piston/plunger  136 . The vacuum generation chamber  138  is selectively fluidly coupled to the proximal end  120  of the inner tubular member  118  through a distal one-way valve  140  (e.g., a duck-bill valve). The distal one-way valve  140  may be fluidly coupled to and/or form a part of a proximal end of the piston/plunger  136 . The distal one-way valve  140  is configured to open when vacuum is generated in the vacuum generation chamber  138 , thereby allowing severed tissue and/or fluid to be drawn from the inner tubular member lumen  150  into the vacuum generation chamber  138 . The distal one-way valve  140  is also configured to close when pressure is increased in the vacuum generation chamber  138 , thereby preventing severed tissue and/or fluid from being pushed from the vacuum generation chamber  138  into the inner tubular member lumen  150 . 
     In particular, the distal one-way valve  140  is configured to open when the pressure distal of the distal one-way valve  140  (i.e., in the inner tubular member lumen  150 ) (the “distal pressure”) is approximately 20 mm Hg to 120 mm Hg greater than the pressure proximal of the distal one-way valve  140  (i.e., in the vacuum generation chamber  138 ) (the “proximal pressure”). Preferably, the distal one-way valve  140  is configured to open when the distal pressure is approximately 50 mm Hg greater than the proximal pressure. The distal one-way valve  140  is also configured to remain at least partially open as long as the distal pressure is at least approximately 50 mm Hg greater than the proximal pressure. When the distal pressure is less than approximately 50 mm Hg greater than the proximal pressure (or the proximal pressure is greater than the distal pressure), the distal one-way valve  140  will be closed. 
     The vacuum generation chamber  138  is also selectively fluidly coupled to a specimen collection chamber  142  through a proximal one-way valve  144  (e.g., a duck-bill valve). The proximal one-way valve  144  may be fluidly coupled to or form a part of a distal end of a connector  146  fluidly coupling the vacuum generation chamber  138  to the specimen collection chamber  142 . The proximal one-way valve  144  is configured to open when a pressure in the vacuum generation chamber  138  is greater than a pressure in the specimen collection chamber  142  (i.e., the reverse of the distal one-way valve  140 ), thereby allowing severed tissue and/or fluid to be pushed from the vacuum generation chamber  138  into the specimen collection chamber  142 . The proximal one-way valve  144  is also configured to close when vacuum is generated in the vacuum generation chamber  138  (i.e., the reverse of the distal one-way valve  140 ), thereby preventing severed tissue and/or fluid (e.g., air) from being drawn from proximal portions of the device  100  (e.g., the specimen collection chamber  142  or the connector  146 ) into the vacuum generation chamber  138 . 
     In particular, the proximal one-way valve  144  is configured to open when the pressure distal of the proximal one-way valve  144  (i.e., in the vacuum generation chamber  138 ) (the “distal pressure”) is approximately 20 mm Hg to 120 mm Hg greater than the pressure proximal of the proximal one-way valve  144  (i.e., in the connector  146  and the specimen collection chamber  142 ) (the “proximal pressure”). Preferably, the proximal one-way valve  144  is configured to open when the distal pressure is approximately 50 mm Hg greater than the proximal pressure. The proximal one-way valve  144  is also configured to remain at least partially open as long as the distal pressure is at least approximately 50 mm Hg greater than the proximal pressure. When the distal pressure is less than approximately 50 mm Hg greater than the proximal pressure (or the proximal pressure is greater than the distal pressure), the proximal one-way valve  144  will be closed. 
     While in this embodiment, the pressure differentials are achieved by changing the pressure in the vacuum generation chamber  138 , the pressure differentials can also be achieved by changing the pressure in the inner tubular member lumen  150  (for the distal one-way valve  140 ), and the connector  146  and the specimen collection chamber  142  (for the proximal one-way valve  144 ). In embodiments where the distal and proximal one-way valves  140 ,  144  are duck-billed valves, the “bills” are facing proximally to allow severed tissue and fluid to travel from the inner tubular member lumen  150  into the vacuum generation chamber  138 , and then into the connector  146  and the specimen collection chamber  142 . This valve configuration also minimizes backflow of allow severed tissue and fluid from the specimen collection chamber  142  and the connector  146  into the vacuum generation chamber  138 , and then into the inner tubular member lumen  150 . 
     The proximal end  120  of the inner tubular member  118  is either physically coupled to or forms part of the piston/plunger  136 . Accordingly, actuating the trigger  126  also moves the inner tubular member  118  longitudinally/axially within the outer tubular member  108 . The distance covered by the inner tubular member  118  during actuating the trigger  126  is greater than the length of the tissue receiving window  114  in the outer tubular member  108 . Actuating the trigger  126  rotates the trigger  126  about the pinned connection  130 , and moves the inner tubular member  118  relative to the outer tubular member  108 . In particular, actuating the second end  134  of the trigger  126  toward the housing  102  causes the inner tubular member  118  to be pushed distally within the outer tubular member  108 , as shown in  FIGS. 2 and 4 . Distal movement of the inner tubular member  118  within the outer tubular member  108  moves the cutting edge  124  at the distal end  122  of the inner tubular member  118  across the tissue receiving window  114 , thereby severing any tissue prolapsing through the tissue receiving window  114 , as shown in  FIG. 4  (without the tissue). The tissue removal device  100  is configured such that the vacuum generated in the vacuum generation chamber  138  by actuating the trigger  126  draws tissue into the tissue receiving window  114  before the cutting edge  124  severs the tissue. The device  100  is also configured such that the vacuum generated in the vacuum generation chamber  138  by actuating the trigger  126  also draws severed tissue from the inner tubular member lumen  150  into the vacuum generation chamber  138  through the open distal one-way valve  140  (when there is low pressure in the vacuum generation chamber  138 ). The device  100  is further configured such that sufficient vacuum to pull tissue into the tissue receiving window and to pull severed tissue into the vacuum generation chamber  138  is created within the vacuum generation chamber  138  with a single squeeze of the trigger  126 . 
     Releasing the trigger  126  allows the spring  128  to restore the trigger  126  to its un-actuated position with the second end  134  away from the housing  102 . When the trigger  126  is restored to its un-actuated position, the inner tubular member  118  is pulled proximally within the outer tubular member  108 , as shown in  FIGS. 1 and 3 . Proximal movement of the inner tubular member  118  within the outer tubular member  108  opens the tissue receiving opening as shown in  FIG. 3 . The tissue removal device  100  is configured such that the pressure generated in the vacuum generation chamber  138  by (e.g., the spring  128 ) restoring the trigger  126  to its un-actuated position pushes severed tissue from the vacuum generation chamber  138  into the specimen collection chamber  142  before the proximally traveling piston/plunger  136  reduces volume of the vacuum generation chamber  138  to less than the volume of the severed tissue. The device  100  is also configured such that sufficient pressure to push severed tissue into the specimen collection chamber  142  is created within the vacuum generation chamber  138  with a single restoration of the trigger  126  (e.g., by the spring  128 ). 
     As described above, each time the trigger  126  is actuated/squeezed, vacuum is created by the distally moving piston  136  in the vacuum generation chamber  138  and immediately applied to the tissue through the inner tubular member  118 , pulling the tissue into the tissue receiving window  114  (see  FIG. 4 ). Further, each time the trigger  126  is actuated/squeezed, the cutting edge  124  travels distally over the tissue receiving window  114 , severing tissue prolapsing therethrough. Moreover, the vacuum generated by each trigger  126  actuation/squeeze also opens the distal one-way valve  140  and draws severed tissue (either from the current or a previous stroke) from the inner tubular member lumen  150  into the vacuum generation chamber  138 . 
     Similarly, each time the spring  128  restores the trigger  126  to its un-actuated position, pressure is created by the proximally moving piston  136  in the vacuum generation chamber  138 . The pressure in the vacuum generation chamber  138  closes the distal one-way valve  140  and opens the proximal one-way valve  144  due to the respective pressure differentials as described above. The pressure in the vacuum generation chamber  138  also pushes the severed tissue (if any) and fluid therein through the open proximal one-way valve  144 , through the connector  146  and into the specimen collection chamber  142 . As a result, any tissue or fluid (including air) drawn into the device  100  by the vacuum during trigger  126  actuation is off-set by an equal volume of tissue and/or fluid that is ejected into the specimen collection chamber  142  (which may have a pressure vent during trigger  126  restoration, thereby preventing build-up of pressure in the device  100 .) 
     Further, each time the trigger  126  is restored, the cutting edge  124  travels proximally across the tissue receiving window  114 , opening the tissue receiving window  114  by moving the inner tubular member  118  previously blocking the window  114  proximally away from the window  114  (see  FIG. 3 ). As such, repeatedly actuating the trigger  126  of the tissue removal device  100  efficiently severs tissue, and moves the severed tissue, using vacuum and pressure from the vacuum generation chamber  138 , through the device  100  and into the specimen collection chamber  142 . At the completion of a tissue removal procedure, the specimen collection chamber  142  with the severed tissue therein, can be removed from the device  100 . In other embodiments, each time the trigger  126  is actuated/squeezed, the inner tubular member  118  and its cutting edge  124  are also rotated to facilitate tissue cutting along with the axial reciprocation. For instance, the tissue removal device can include a cam and cam follower (neither shown in  FIGS. 1-4 ) or other components to transfer the actuation motion to rotation of the cutting edge  124  of the inner tubular member  118 . An embodiment with a rotating inner tubular member is described below in  FIGS. 17-19  and described below. 
       FIGS. 5-14  illustrate another embodiment of a tissue removal device  100 ′ in respective un-actuated ( FIGS. 8 and 10-12  and actuated ( FIG. 9 ) states. The tissue removal device  100 ′ includes manually operated assemblies for creating vacuum and for cutting tissue (described below). These vacuum generation and tissue cutting assemblies of the tissue removal device  100 ′ are structurally and operationally similar to the vacuum generation and tissue cutting assemblies of the tissue removal device  100  depicted in  FIGS. 1-4  and described above. Like the tissue removal device  100  depicted in  FIGS. 1-4 , the tissue removal device  100 ′ depicted in  FIGS. 5-12  is capable of performing a tissue removal procedure (e.g., a polypectomy) with no further components, and is therefore also a “tetherless” device. 
       FIG. 5  depicts the tissue removal device  100 ′ in an external side view. The tissue removal device  100 ′ includes a pistol-shaped housing  102 ′. The more pistol-like shape of the tissue removal device  100 ′ results in the tissue removal device  100 ′ having a handle  152  with a bottom end  154  in addition to a body  156  with a distal end  106 ′ and a proximal end  104 ′. The ergonomics of the pistol-shaped housing  102 ′ also allows a user&#39;s hand to generate more power when actuating the tissue removal device  100 ′.  FIGS. 6-8  are increasingly detailed cross-section views of the tissue removal device  100 ′ depicted in  FIG. 5 , with  FIG. 8  showing the specimen collection chamber  142 ′ formed at the proximal end  104 ′ of the housing  102 ′ in detail. 
     The tissue removal device  100 ′ also includes an outer tubular member  108 ′ having a proximal end  110 ′ ( FIG. 7 ) rotatably coupled to the distal end  106 ′ of the housing  102 ′ and a distal end  112 ′ having a tissue receiving window  114 ′ ( FIGS. 5 and 6 ). The outer tubular member  108 ′ also includes a rotator  116 ′ configured to facilitate user rotation of the rotatably coupled outer tubular member  108 ′. The rotator  116 ′ is disposed adjacent and fixed to the proximal end  110 ′ of the outer tubular member  108 ′. In this manner, the outer tubular member  108 ′ is configured to selectively rotate relative to the housing  102 ′ in response to manipulation of the rotator  116 ′ to alter the circumferential position of the tissue receiving window  114 ′. In other embodiments, the rotator can be located at a proximal end of the tissue removal device. In such embodiments, the rotation may be coupled to the outer tubular member via a series of connectors and gears. The tissue removal device  100 ′ further includes an inner tubular member  118 ′ configured for axial movement within an outer tubular member lumen  148 ′ in the outer tubular member  108 ′, as shown in  FIGS. 13 and 14 . The outer and inner tubular members  108 ′,  118 ′ can be either flexible or rigid. 
     The outer tubular member  108 ′ may be configured for transcervical insertion. Additionally or alternatively, the outer tubular member  108 ′ may be configured for insertion through a working channel of an endoscopic instrument so that the tissue receiving window  114 ′ is disposed in an interior region of a patient&#39;s body. The distal end  112 ′ of the outer tubular member  108 ′ may be conformable or rigid. The inner tubular member  118 ′ is hollow, and includes an open proximal end  120 ′ (see  FIGS. 7 and 9 ), an open distal end  122 ′, and an inner tubular member lumen  150 ′ (see  FIGS. 13 and 14 ) extending between the open proximal end  120 ′ and the open distal end  122 ′. The distal end  122 ′ of the inner tubular member  118 ′ includes a cutting edge  124 ′ (e.g., annular) for severing tissue projecting into the tissue receiving window  114 ′ as the inner tubular member  118 ′ moves past the tissue receiving window  114 ′ (see  FIGS. 13 and 14 ). 
     The tissue removal device  100 ′ also includes a manually operated actuator, or trigger  126 ′ rotatably coupled to the housing  102 ′ by a pinned connection  130 ′, which acts as a pivot point, such that the trigger  126 ′ is configured to rotate about the pinned connection  130 ′. The trigger  126 ′ includes a first end  132 ′ disposed inside of the housing  102 ′ in the body  156 , and a second end  134 ′ disposed outside of the housing  102 ′. In an un-actuated state, most of the trigger  126 ′ is separated from and approximately parallel to the handle  152 . The trigger  126 ′ is rotatably coupled to the housing  102 ′ such that a user may hold the housing  102 ′ in one hand and actuate the trigger  126 ′ by squeezing the second end  134 ′ of the trigger  126 ′ toward the handle  152 . Actuating the trigger  126 ′ by squeezing rotates the second end  134 ′ of the trigger  126 ′ toward the handle  152  about the pivot point formed by the pinned connection  130 ′. A spring  128 ′ [not shown?] is configured to bias the second end  134 ′ of the trigger  126 ′ away from the handle  152 , as shown in  FIGS. 5-7 . As a result, when the trigger  126 ′ is released after being actuated, the spring  128 ′ restores the second end  134 ′ of the trigger  126 ′ to its un-actuated position away from the handle  152 . The spring  128 ′ may be coupled to the housing  102 ′ and the first end  132 ′ of the trigger  126 ′. It should be understood that the individual components of the device  100 ′ illustrated in  FIGS. 5-14  are not necessarily drawn to scale. Further,  FIGS. 5-14  are provided to illustrate the principles of the disclosed embodiments, and are not intended to be limiting. 
     The first end  132 ′ of the trigger  126 ′ is coupled to a piston/plunger  136 ′, which forms a movable distal wall of the vacuum generation chamber  138 ′, thereby enabling the vacuum generation chamber  138 ′ to change its volume with movement of the piston/plunger  136 ′. Actuating the trigger  126 ′ rotates the first end  132 ′ of the trigger  126 ′ about the pinned connection  130 ′, and moves the piston  136 ′ relative to a proximal wall of the vacuum generation chamber  138 ′. In particular, actuating the second end  134 ′ of the trigger  126 ′ toward the handle  152  causes the piston  136 ′ to be pulled distally away from the proximal wall of the vacuum generation chamber  138 ′, thereby increasing the volume of the vacuum generation chamber  138 ′ and reducing the pressure therein to generate vacuum, as shown in  FIG. 9 . In one embodiment, when the trigger  126 ′ is fully actuated (i.e., moved maximally toward the housing  102 ′), a volume of the vacuum generation chamber  138 ′ is increased to about three times a volume of the inner tubular member lumen  150 ′. In some embodiments, this volume ratio optimizes vacuum generation and tissue travel through the inner tubular member lumen  150 ′, and minimizes tissue clogging therein. 
     Releasing the trigger  126 ′ allows the spring  128 ′ to restore the second end  134 ′ of the trigger  126 ′ to its un-actuated position away from the handle  152 . When the trigger  126 ′ is restored to its un-actuated position, the piston  136 ′ is pushed proximally toward the proximal wall of the vacuum generation chamber  138 ′, thereby decreasing the volume of the vacuum generation chamber  138 ′ and increasing the pressure therein, as shown in  FIG. 7 . 
     While the tissue removal device  100 ′ depicted in  FIGS. 5-14  generates vacuum and pressure with a vacuum generation chamber  138 ′ having a movable piston/plunger  136 ′, other tissue removal devices may incorporate other manual vacuum/pressure generation mechanisms. For instance, some the embodiment depicted in  FIGS. 20 and 2  includes a bellows  190  in place of a piston/plunger  136 ′ that forms a wall of the vacuum generation chamber  138 ′ depicted in  FIG. 9 . The bellows  190  in  FIGS. 20 and 21  includes a movable or elastically deformable distal wall  190  in place of a movable piston/plunger. Like the piston/plunger, the distal wall  190  is fluidly coupled to the inner tubular member lumen  150 ′ via a distal one-way valve  140 ″. The movable distal wall  190  is physically coupled to the trigger  126 ′ such that actuating the trigger  126 ′ moves the distal wall  190  distally to increase the volume of the vacuum generation chamber  138 ″ (compare  FIGS. 20 and 21 ) and generate vacuum (i.e., lower pressure) therein. Further, releasing the trigger  126 ′ (which is biased in an un-actuated configuration) moves the distal wall  190  proximally to decrease the volume of the vacuum generation chamber  138 ″ and increase the pressure therein. In the embodiment depicted in  FIGS. 20 and 21 , the distal wall  190  is elastic (e.g., made from rubber) and the volume of the vacuum generation chamber  138 ″ can be increased and vacuum generated therein by elastically deforming/stretching the rubber distal wall  190  in a distal direction. Further, the elastic restoration of the distal wall  190  can be utilized to drive (partially or completely) longitudinal movement of the inner tubular member  118  and bias the trigger  126 ′ in its un-actuated configuration. Moreover, the distal one-way valve  140 ″ may be a flap valve  140 ″ configured to allow proximally directed fluid flow. Replacing the piston/plunger  136 ′ in  FIG. 7-9  with the bellows  190  in  FIGS. 20 and 21  eliminates the need for a slidable O-ring assembly to prevent fluid from leaking around the piston/plunger  136 ′, thereby reducing friction and the trigger force needed to actuate the trigger  126 ′. In other embodiments, the vacuum generation chamber may be replaced and/or supplemented with one or more peristaltic pumps, vane pumps, and rotatory pump. 
     The proximal end  120 ′ of the inner tubular member  118 ′ may be fluidly coupled to and/or form part of the piston/plunger  136 ′. The vacuum generation chamber  138 ′ is selectively fluidly coupled to the inner tubular member lumen  150 ′ through a distal one-way valve  140 ′ (e.g., a duck-bill valve). The distal one-way valve  140 ′ may be fluidly coupled to and/or form a part of a proximal end of the piston/plunger  136 ′. The distal one-way valve  140 ′ is configured to open when vacuum is generated in the vacuum generation chamber  138 ′, thereby allowing severed tissue and/or fluid to be drawn from the inner tubular member lumen  150 ′ into the vacuum generation chamber  138 ′. The distal one-way valve  140 ′ is also configured to close when pressure is increased in the vacuum generation chamber  138 ′, thereby preventing severed tissue and/or fluid from being pushed from the vacuum generation chamber  138 ′ into the inner tubular member lumen  150 ′. 
     In particular, the distal one-way valve  140 ′ is configured to open when the pressure distal of the distal one-way valve  140 ′ (i.e., in the inner tubular member lumen  150 ′) (the “distal pressure”) is approximately 40 mm Hg greater than the pressure proximal of the distal one-way valve  140 ′ (i.e., in the vacuum generation chamber  138 ′) (the “proximal pressure”). The distal one-way valve  140 ′ is also configured to remain at least partially open as long as the distal pressure is at least approximately 40 mm Hg greater than the proximal pressure. When the distal pressure is less than approximately 40 mm Hg greater than the proximal pressure (or the proximal pressure is greater than the distal pressure), the distal one-way valve  140 ′ will be closed. 
     The vacuum generation chamber  138 ′ is also selectively fluidly coupled to a specimen collection chamber  142 ′ through a proximal one-way valve  144 ′ (e.g., a duck-bill valve). The proximal one-way valve  144 ′ may be coupled to or form a part of the body  156  adjacent a proximal end  104 ′ thereof. The proximal one-way valve  144 ′ is configured to open when a pressure is increased in the vacuum generation chamber  138 ′ (i.e., the reverse of the distal one-way valve  140 ′), thereby allowing severed tissue and/or fluid to be pushed from the vacuum generation chamber  138 ′ into the specimen collection chamber  142 ′. The proximal one-way valve  144 ′ is also configured to close when vacuum is generated in the vacuum generation chamber  138 ′ (i.e., the reverse of the distal one-way valve  140 ′), thereby preventing severed tissue and/or fluid (e.g., air) from being drawn from proximal portions of the device  100 ′ (e.g., the specimen collection chamber  142 ′) into the vacuum generation chamber  138 ′. 
     In particular, the proximal one-way valve  144 ′ is configured to open when the pressure distal of the proximal one-way valve  144 ′ (i.e., in the vacuum generation chamber  138 ′) (the “distal pressure”) is approximately 40 mm Hg greater than the pressure proximal of the proximal one-way valve  144 ′ (i.e., in the specimen collection chamber  142 ′) (the “proximal pressure”). The proximal one-way valve  144 ′ is also configured to remain at least partially open as long as the distal pressure is at least approximately 40 mm Hg greater than the proximal pressure. When the distal pressure is less than approximately 40 mm Hg greater than the proximal pressure (or the proximal pressure is greater than the distal pressure), the proximal one-way valve  144 ′ will be closed. 
     The tissue removal device  100 ′ also includes a porous tissue trap  158  held in the specimen collection chamber  142 ′ by a tissue trap housing  160 . The tissue trap  158  is generally cylindrical with a closed proximal end and an open distal end leading to a tissue trap interior  174 . The distal end of the tissue trap  158  is configured to mate with a corresponding flange  176  on the body  156  of the tissue removal device  100 ′, such that excised tissue and fluid entering the specimen collection chamber  142 ′ must enter the tissue trap  158  before the fluid may exit the tissue removal device  100 ′. The tissue trap  158  has openings  162  formed in the longitudinal surface thereof that collectively form a flow path between the tissue trap interior  176  and a bottom portion  164  of the specimen collection chamber  142 ′. The openings  162  are size to retain excised tissue in the tissue trap  158  while allowing fluid (e.g., distention fluid) to pass through the tissue trap  158  and into the bottom portion  164  of the specimen collection chamber  142 ′. In one embodiment, the fluid passes through the openings  162  in the tissue trap  158  by gravity separation. The fluid drains from the bottom portion  164  of the specimen collection chamber  142 ′ through an external connector  166  and outside of the tissue removal device  100 ′. Outside of the tissue removal device  100 ′, the fluid may collect in a fluid trap (not shown) connected to the external connector  166 . Such a fluid trap may be open to atmosphere. The tissue trap  158  may be an integrally formed (i.e., molded from a single piece of material) component, which may be made by machining a block or tube of polymer. Alternatively, the tissue trap  158  may be formed using any other manufacturing method including, but not limited to, 3-D printing. 
     As shown in  FIG. 8 , the tissue trap housing  160  may include one or more depressions  168  configured to hold one or more O-rings to form a fluid tight seal between the tissue trap housing  160  and the proximal end  104 ′ of the body  156  of the tissue removal device  100 ′. As shown in  FIGS. 11 and 12 , the tissue trap housing  160  may include at least one detent  170  configured to cooperate with a wedge-shaped slot  172  to removably lock the tissue trap housing  160  onto the proximal and  104 ′ of the body  156  of the tissue removal device  100 ′. For instance, the tissue trap housing  160  may be locked with a ¼ turn of the tissue trap housing  160  relative to the housing  102 ′. After a tissue resection procedure and the excess fluid has drained out of the specimen collection chamber  142 ′, the tissue trap housing  160  can be removed from the proximal and  104 ′ of the body  156  of the tissue removal device  100 ′ by twisting the tissue trap housing  160  counterclockwise to unlock and pulling proximally. After the tissue trap housing  160  has been removed, the tissue trap  158  may remain attached to the proximal end  104 ′ of the body  156  or the tissue trap  158  may be removed with the tissue trap housing  160 . In the former case, the tissue trap  158  can be removed from the proximal end  104 ′ of the body  156 . In the latter case, the tissue trap  158  can be removed from inside the tissue trap housing  160 . Then, the excised tissue can be removed from the tissue trap  158 . 
     While in this embodiment, the pressure differentials are achieved by changing the pressure in the vacuum generation chamber  138 ′, in other embodiments the pressure differentials can also be achieved by changing the pressure in the specimen collection chamber  142 ′ (e.g., using an external vacuum source). In embodiments where the distal and proximal one-way valves  140 ′,  144 ′ are duck-billed valves, the “bills” are facing proximally to allow severed tissue and fluid to travel from the inner tubular member lumen  150 ′ into the vacuum generation chamber  138 ′, and then into the specimen collection chamber  142 ′ and the tissue trap  158 . This valve configuration also minimizes backflow of allow severed tissue and fluid from the specimen collection chamber  142 ′ and the tissue trap  158  into the vacuum generation chamber  138 ′, and then into the inner tubular member lumen  150 ′. 
     This valve configuration also allows fluid pressure from within the uterus to open both the distal and proximal one-way valves to allow a slow continuous flow of distension fluid out of the uterus through the tissue removal device. In one embodiment, the cracking pressure to open the distal and proximal one-way valves is about 40 mm Hg (difference between distal pressure and proximal pressure). With a 3 L bag of saline hung at an elevation of at least about 0.67 m (about 26.5″) to distend a uterus, the distension pressure in the uterus is about 50 mm Hg to 60 mm Hg. Accordingly, the distension pressure is greater than the cracking pressure of the distal and proximal one-way valves, and there is a slow continuous flow of distension fluid through the tissue removal device. The continuous flow of distension fluid eliminates the need to prime the tissue removal device with saline (flush out air bubbles and other material from the flow path), because the pressure differential will automatically cause distension fluid flow and thereby prime the tissue removal device. Further, the continuous flow of distension fluid will draw uterine tissue (e.g., hanging polyps) into the tissue receiving window in the outer tubular member. This drawing of uterine tissue into the tissue receiving window allows the entire cutting stroke of the inner tubular member across the tissue receiving window to be effective to resect tissue at a higher rate (e.g., g/min). Without the continuous fluid flow, vacuum may not be generated until the inner tubular member begins to move across the tissue receiving window, thereby rendering a portion of the cutting stroke ineffective. 
     The proximal end  120 ′ of the inner tubular member  118 ′ is either physically coupled to or forms part of the piston/plunger  136 ′. Accordingly, actuating the trigger  126 ′ also moves the inner tubular member  118 ′ longitudinally/axially within the outer tubular member  108 ′. The distance covered by the inner tubular member  118 ′ during actuating the trigger  126 ′ is greater than the length of the tissue receiving window  114 ′ in the outer tubular member  108 ′. Actuating the trigger  126 ′ rotates the trigger  126 ′ about the pinned connection  130 ′, and moves the inner tubular member  118 ′ relative to the outer tubular member  108 ′. In particular, actuating the second end  134 ′ of the trigger  126 ′ toward the handle  152  causes the inner tubular member  118 ′ to be pushed distally within the outer tubular member  108 ′, as shown in  FIGS. 9 and 14 . Distal movement of the inner tubular member  118 ′ within the outer tubular member  108 ′ moves the cutting edge  124 ′ at the distal end  122 ′ of the inner tubular member  118 ′ across the tissue receiving window  114 ′, thereby severing any tissue prolapsing through the tissue receiving window  114 ′, as shown in  FIG. 14  (without the tissue). The tissue removal device  100 ′ is configured such that the vacuum generated in the vacuum generation chamber  138 ′ by actuating the trigger  126 ′ draws tissue into the tissue receiving window  114 ′ before the cutting edge  124 ′ severs the tissue. The device  100 ′ is also configured such that the vacuum generated in the vacuum generation chamber  138 ′ by actuating the trigger  126 ′ also draws severed tissue from the inner tubular member lumen  150 ′ into the vacuum generation chamber  138 ′ through the open distal one-way valve  140 ′ (when there is low pressure in the vacuum generation chamber  138 ′). The device  100 ′ is further configured such that sufficient vacuum to pull tissue into the tissue receiving window and to pull severed tissue into the vacuum generation chamber  138 ′ is created within the vacuum generation chamber  138 ′ with a single squeeze of the trigger  126 ′. 
     Releasing the trigger  126 ′ allows the spring  128 ′ to restore the trigger  126 ′ to its un-actuated position with the second end  134 ′ away from the handle  152 . When the trigger  126 ′ is restored to its un-actuated position, the inner tubular member  118 ′ is pulled proximally within the outer tubular member  108 ′, as shown in  FIGS. 7 and 13 . Proximal movement of the inner tubular member  118 ′ within the outer tubular member  108 ′ opens the tissue receiving opening as shown in  FIG. 13 . The tissue removal device  100 ′ is configured such that the pressure generated in the vacuum generation chamber  138 ′ by (e.g., the spring  128 ′) restoring the trigger  126 ′ to its un-actuated position pushes severed tissue from the vacuum generation chamber  138 ′ into the specimen collection chamber  142 ′ and the tissue trap  158  before the proximally traveling piston/plunger  136 ′ reduces volume of the vacuum generation chamber  138 ′ to less than the volume of the severed tissue. The device  100 ′ is also configured such that sufficient pressure to push severed tissue into the specimen collection chamber  142 ′ and the tissue trap  158  is created within the vacuum generation chamber  138 ′ with a single restoration of the trigger  126 ′ (e.g., by the spring  128 ′). 
     As described above, each time the trigger  126 ′ is actuated/squeezed, vacuum is created by the distally moving piston  136 ′ in the vacuum generation chamber  138 ′ and immediately applied to the tissue through the inner tubular member  118 ′, pulling the tissue into the tissue receiving window  114 ′ (see  FIG. 14 ). Further, each time the trigger  126 ′ is actuated/squeezed, the cutting edge  124 ′ travels distally over the tissue receiving window  114 ′, severing tissue prolapsing therethrough. Moreover, the vacuum generated by each trigger  126 ′ actuation/squeeze also opens the distal one-way valve  140 ′ and draws severed tissue (either from the current or a previous stroke) from the inner tubular member lumen  150 ′ into the vacuum generation chamber  138 ′. 
     Similarly, each time the spring  128 ′ restores the trigger  126 ′ to its un-actuated position, pressure is created by the proximally moving piston  136 ′ in the vacuum generation chamber  138 ′. The pressure in the vacuum generation chamber  138 ′ closes the distal one-way valve  140 ′ and opens the proximal one-way valve  144 ′ due to the respective pressure differentials as described above. The pressure in the vacuum generation chamber  138 ′ also pushes the severed tissue (if any) and fluid therein through the open proximal one-way valve  144 ′, and into the specimen collection chamber  142 ′ and the tissue trap  158 . As a result, any tissue or fluid (including air) drawn into the device  100 ′ by the vacuum during trigger  126 ′ actuation is off-set by an equal volume of tissue and/or fluid that is ejected into the specimen collection chamber  142 ′ and the tissue trap  158  (which may have a pressure relief valve to prevent build-up of pressure in the device  100 ′ during restoration of trigger ′ 126 ). Alternatively or additionally, the specimen collection chamber  142 ′ may be coupled by the external connector  166  to atmosphere outside of the tissue removal device  100 ′. In some embodiments, the external connector  166  may be coupled to an external vacuum source (not shown). In such embodiments, a valve (not shown) may selectively couple the external connection  166  to the external vacuum source such as a pump or a syringe. An example of such a valve may be a pinch valve with the external connector  166  passing therethrough. The external vacuum may generate a pressure differential that overrides and opens both the proximal and distal one-way valves  140 ′,  144 ′. 
     Further, each time the trigger  126 ′ is restored, the cutting edge  124 ′ travels proximally over the tissue receiving window  114 ′, opening the tissue receiving window  114 ′ by moving the inner tubular member  118 ′ previously blocking the window  114 ′ proximally away from the window  114 ′ (see  FIG. 13 ). As such, repeatedly actuating the trigger  126 ′ of the tissue removal device  100 ′ efficiently severs tissue, and moves the severed tissue, using vacuum and pressure from the vacuum generation chamber  138 ′, through the device  100 ′ and into the specimen collection chamber  142 ′ and the tissue trap  158 . At the completion of a tissue removal procedure, the specimen collection chamber  142 ′ and the tissue trap  158  with the severed tissue therein, can be removed from the device  100 ′. In other embodiments, each time the trigger  126 ′ is actuated/squeezed, the inner tubular member  118 ′ and its cutting edge  124 ′ are also rotated to facilitate tissue cutting along with the axial reciprocation. For instance, the tissue removal device can include a cam and cam follower (neither shown in  FIGS. 5-14 ) or other components to transfer the actuation motion to rotation of the cutting edge  124 ′ of the inner tubular member  118 ′. An embodiment with a rotating inner tubular member is described below in  FIGS. 17-19  and described below. 
       FIGS. 15 and 16  depict two embodiments of distal ends  112 A,  112 B of respective outer tubular members  108 A,  108 B that are configured to acquire tissue (e.g., endometrial tissue) using the respective tissue removal devices connected thereto. The distal ends  112 A,  112 B depicted in  FIGS. 15 and 16  can form parts of the tissue removal devices  100 ,  100 ′ depicted in  FIGS. 1-4 and 5-14 , respectively, or other tissue removal devices having features similar to features of the tissue removal devices  100 ,  100 ′. 
     Each of the distal ends  112 A,  112 B includes an edge  178 A,  178 B at respective distal ends of respective tissue receiving windows  114 A,  114 B. The edges  178 A,  178 B are substantially orthogonal to the longitudinal axes of the respective outer tubular members  108 A,  108 B. Accordingly, when the outer tubular members  108 A,  108 B are dragged across a tissue surface (e.g., the endometrium), tissue can enter the respective tissue receiving windows  114 A,  114 B and collect therein as the tissue is scraped by the respective edges  178 A,  178 B. After the tissue enters the respective tissue receiving windows  114 A,  114 B, it can be prolapsed by the vacuum generated by the respective tissue removal devices as described above. In some procedures, it may be suitable to collect the tissue using the vacuum with or without cutting by a reciprocating inner tubular member. 
     In some embodiments, like those described in U.S. Pat. No. 9,060,760, the tissue removal device can operate in a “vacuum mode” and a “cutting mode.” The foregoing patent is hereby incorporated by reference into the present application in its entirety as though set forth in full. In such embodiments, like the embodiments described above, the trigger is operatively coupled to the piston/plunger. However, in such embodiments, the trigger may be selectively operatively coupled to the inner tubular member via a yoke, which can be manipulated to select whether the trigger is operatively coupled to or uncoupled from the inner tubular member. For instance, in the cutting mode, the yoke may be placed in a configuration such that the trigger is operatively coupled to the inner tubular member. Consequently, in the cutting mode, actuating the trigger will move both the inner tubular member (to cut tissue prolapsing through the tissue receiving window) and the piston/plunger to deliver vacuum. In the vacuum mode, the yoke may be placed in a configuration such that the tissue is prolapsing through the tissue receiving window while the trigger is operatively uncoupled from the inner tubular member. Consequently, in the vacuum mode, actuating the trigger will move the piston/plunger to generate vacuum, without moving the inner tubular member. In the vacuum mode, the outer tubular member of the tissue removal device can be used as a pipelle (e.g., an endometrial pipelle) to remove tissue (e.g., endometrial tissue) by scraping across a tissue surface. In such embodiments, the distal ends  112 A,  112 B depicted in  FIGS. 15 and 16  can help to remove tissue by scraping. 
       FIGS. 17-19  depict a tissue removal device  100 ″ according to still another embodiment. In particular,  FIGS. 17-19  illustrate a motion conversion system  180  configured to convert linear (e.g., longitudinal/axial) motion of the inner tubular member  118 ″ relative to the housing  102 ″ and the outer tubular member into rotational motion of the inner tubular member  118 ″ relative to the housing  102 ″ and the outer tubular member. The motion conversion system  180  includes an inner tubular member holder  182  physically coupled to the inner tubular member  118 ″ such that the inner tubular member holder  182  and the inner tubular member  118 ″ move both longitudinally and rotationally together. The inner tubular member holder  182  includes a helical groove  184  (i.e., a cam) that spirals around the longitudinal axes of both the inner tubular member holder  182  and the inner tubular member  118 ″. The motion conversion system  180  also includes a cam follower  186  ( FIG. 19 ) physically coupled on an inner surface of the housing  102 ″ such that it is stationary relative to the housing  102 ″. In some embodiments, the cam follower  186  may be formed on the inner surface of the housing  102 ″. 
     As shown in  FIG. 19 , the cam follower  186  is disposed in the helical groove  184  and sized and shaped to travel back and forth along the spiral/helix therein. Accordingly, when the inner tubular member  118 ″ moves distally (driven by the trigger to cut tissue prolapsing through the tissue receiving window), the interaction between the helical groove  184  in the inner tubular member holder  182  and the cam follower  186  causes the inner tubular member holder  182  and the inner tubular member  118 ″ coupled thereto to rotate relative to the housing  102 ″ and the outer tubular member. The inner tubular member  118 ″ may be rotatably supported by a barrel  188  portion of the housing  102 ″. Rotation of the inner tubular member  118 ″ also rotates the cutting edge  124  located at a distal end thereof (see  FIGS. 3, 4, 13 and 14 ). Rotating the cutting edge  124  while advancing same over prolapsing tissue increases the efficiency with which the cutting edge  124  severs the tissue. This increased cutting efficiency particularly benefits cutting of more fibrous tissue using a cutting instead of a shearing mechanism. In some embodiments, the 
     In the embodiment depicted in  FIG. 19 , translating the inner tubular member holder  182  from a proximal most position to a distal most position will rotate the inner tubular member  118 ″ approximately twice. Other embodiments may have different helical grooves that result in different numbers of rotations per stroke. For instance, if the inner tubular member holder is configured to translate only a portion of its length per stroke, the motion conversion system may generate half a rotation per stroke. 
     In some embodiments, the piston may rotate along with the inner tubular member. In other embodiments, the inner tubular member may be longitudinally coupled to the piston, but free to rotate relative to the piston. 
     The motion conversion system  180  depicted in  FIGS. 17-19  and described above can be used with many embodiments of tissue removal devices including, but not limited to, those depicted in  FIGS. 1-4 and 5-14 . While the motion conversion system  180  depicted in  FIGS. 17-19  include a helical groove  184  coupled to an inner tubular member  118 ″ and a cam follower  186  coupled to a housing  102 ″, other motion conversion systems may have alternative mechanisms for converting linear motion to rotation. For instance, an alternative motion conversion system may include a helical groove coupled to a housing and a cam following coupled to an inner tubular member. 
     *Although this disclosure has been provided in the context of certain embodiments and examples, it will be understood by those skilled in the art that the disclosure extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the embodiments and obvious modifications and equivalents thereof. Additionally, the skilled artisan will recognize that any of the above-described methods can be carried out using any appropriate apparatus. Further, the disclosure herein of any particular feature, aspect, method, property, characteristic, quality, attribute, element, or the like in connection with an embodiment can be used in all other embodiments set forth herein. Thus, it is intended that the scope of the present inventions disclosed herein should not be limited to the illustrated and/or described embodiments. It will be understood by those skilled in the art that various changes and modifications may be made (e.g., the dimensions of various parts) without departing from the scope of the disclosed inventions, which is to be defined only by the following claims and their equivalents. The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense.