Abstract:
Systems, methods and apparatus are provided through which, in some embodiments, an extending column is comprised of a plurality of stacked slides that are mounted to each other through linear bearing assemblies that allow the extending column to telescope inward and outward. Some embodiments of the extending column have a synchronization mechanism between each slide to extend each slide in equal distances relative to each other.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates generally to equipment extending columns, and more particularly to X-ray tube and collimator extending columns.  
       BACKGROUND OF THE INVENTION  
       [0002]     In conventional medical diagnostic X-ray radiography, an X-ray source and a collimator are suspended from a ceiling by an extending column. The extending column is often referred to as an overhead tube suspension system. The X-ray source sends a beam of X-rays from the X-ray source behind the patient, through the patient&#39;s chest, to the recording medium (e.g. film or digital recording means). A collimator is a diaphragm or system of diaphragms made of an absorbing material, designed to define and restrict the dimensions and direction of a beam of radiation from the X-ray source.  
         [0003]     The extending column is mounted to carriages to provide freedom of motion that allows general positioning of the X-ray source at the desired location and orientation within an X-ray examination room. In conventional extending columns, the extending column consists of a series of concentric cylinders, either circular or prismatic (e.g. octagonal), with ball bearing assemblies running in channels or on tracks in at least two planes to provide smooth motion with as little free play as possible. In one embodiment, the ball bearing assemblies are on opposing sides of the concentric cylinder. The amount of free play in the extending column is minimized by closely controlling tolerances, and also by providing adjustment means to reduce the clearance for the bearings as much as possible. Conventional extending columns are approximately symmetrical, with guiding and synchronizing means being distributed approximately equally in 2, 3, or 4 sides of the columns.  
         [0004]     One problem with conventional extending columns is that the precision of motion is poor, since it is very difficult to manufacture the telescoping sections precisely enough to maintain the parallelism and straightness required among the various column sections thus employed.  
         [0005]     Another problem is that that adjustment of the bearings is difficult, and this leads to inconsistencies in moving efforts and stiffness, as well as lost motion in the assemblies.  
         [0006]     Yet another problem is that synchronized motion of the column sections is achieved through the use of “J-bars” and the like, which are long bars extending from one section into the next. These J-bars often rub against the sections, which increases friction in movement, which in turn increases wear of the extending column and requires a greater manual force by an operator of the X-ray equipment to position the X-ray source and the collimator mounted on the extending column.  
         [0007]     Still yet another problem is that the length of travel permissible for a given column length is limited, because the bearings are not stiff enough if spaced close together. As a result, clinical usage is somewhat restricted, and extensions are sometimes employed to achieve the desired anatomical coverage range.  
         [0008]     A further problem is the size of the conventional extending columns. The area close to an X-ray examination table has rather close quarters for the operators of the X-ray equipment. Reducing the size of the extending column would provide more room for the operators.  
         [0009]     For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for an extending column for medical diagnostic that has improved precision of motion. There is also a need for reducing inconsistencies in moving efforts and stiffness, as well as reducing lost motion in the assemblies. There is an additional need to reduce the rubbing of J-bars against sections. There is a further need increase rigidity in order to improve clinical usage without the need for extensions to achieve the desired anatomical coverage range. There is also a need to reduce the size of the extending column.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0010]     The above-mentioned shortcomings, disadvantages and problems are addressed herein, which will be understood by reading and studying the following specification.  
         [0011]     In one aspect, and improved means for providing the extension motion for the column by an extending column that includes a plurality of stacked slides that are mounted to each other through linear bearing assemblies that allow the extending column to telescope inward and outward. Some embodiments of the extending column have a synchronization mechanism between each slide to extend each slide in equal distances relative to each other.  
         [0012]     In one aspect, an asymmetrical apparatus includes an outer section that is mountable to a supporting structure for the apparatus, a first linear bearing assembly coupled to the outer section, a first moveable linear slide base that is operably coupled to first linear bearing assembly, a second linear bearing assembly that is operably coupled to the first moveable linear slide base, and a second moveable linear slide base that is operably coupled to the second linear bearing assembly.  
         [0013]     In another aspect, an apparatus includes an outer section, mountable to a supporting structure for the apparatus, a plurality of linear slide bases, a first linear slide base of the plurality of linear slide bases being mounted on the outer section, the plurality of linear slide bases being constrained to move in a rectilinear motion with respect to each other by linear bearings, and at least one medical diagnostic apparatus mounted on the last of the plurality of linear slide bases.  
         [0014]     In yet another aspect, a system includes an outer section that is mountable to a supporting structure for the system, and a plurality of concave linear slide bases in which a first linear slide base of the plurality of linear slide bases being mounted on the outer section, each concave linear slide bases is successively smaller than an immediately previous concave linear slide bases to the extent that each concave linear slide bases fits into the immediately previous concave linear slide base and the plurality of linear slide bases are constrained to move in a rectilinear motion with respect to each other by linear bearings.  
         [0015]     Apparatus, systems, and methods of varying scope are described herein. In addition to the aspects and advantages described in this summary, further aspects and advantages will become apparent by reference to the drawings and by reading the detailed description that follows. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1  is a block diagram that provides a system level overview of an asymmetrical extending column that includes linear bearings to provide freedom of motion for general positioning of imaging apparatus at a desired location and orientation.  
         [0017]      FIG. 2  is a block diagram that provides a system level overview of an asymmetrical extending column that includes a synchronization mechanism to provide freedom of motion for general positioning of imaging apparatus at a desired location and orientation.  
         [0018]      FIG. 3  is a block diagram that provides a system level overview of a three-tiered extending column that includes synchronization mechanisms and linear bearings to provide freedom of motion for general positioning of imaging apparatus at a desired location and orientation.  
         [0019]      FIG. 4  is an end cross section diagram of apparatus according to an embodiment.  
         [0020]      FIG. 5  is an end cross section diagram of apparatus that includes synchronization mechanisms according to an embodiment.  
         [0021]      FIG. 6  is a cross section block diagram of a five-tiered extending column with covers on each section that includes gear, rack, and chain and sprocket synchronization mechanisms and linear bearings, according to an embodiment.  
         [0022]      FIG. 7  is a longitudinal cross section block diagram of a five-tiered extending column in a retracted position with covers on each section that includes gear, rack, chain and sprocket synchronization mechanisms and linear bearings, according to an embodiment.  
         [0023]      FIG. 8  is an azimuthal cross section block diagram of a five-tiered extending column  800  in a fully retracted position without covers showing gear, rack, chain and sprocket synchronization mechanisms, according to an embodiment.  
         [0024]      FIG. 9  is an azimuthal cross section block diagram of a five-tiered extending column in an extended position without covers showing gear, rack, chain and sprocket synchronization mechanisms, according to an embodiment.  
         [0025]      FIG. 10  is a cross section block diagram of a five-tiered extending column in a partly extended position without covers showing gear, rack, chain and sprocket synchronization mechanisms, according to an embodiment.  
         [0026]      FIG. 11  is a side view of fifth open section of an extending column with a drive, and X-ray source and a collimator mounted to the last open section, according to an embodiment. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0027]     In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical and other changes may be made without departing from the scope of the embodiments. The following detailed description is, therefore, not to be taken in a limiting sense.  
         [0028]     The detailed description is divided into five sections. In the first section, a system level overview is described. In the second section, apparatus of embodiments are described. In the third section, a conclusion of the detailed description is provided.  
       System Level Overviews  
       [0029]      FIG. 1  is a block diagram that provides a system level overview of an asymmetrical extending column that includes linear bearings to provide freedom of motion for general positioning of imaging apparatus at a desired location and orientation. System  100  solves the need in the art for an extending column that has improved precision of motion, reduced lost motion in the extending column, increased rigidity, as well as reduced size of the extending column.  
         [0030]     System  100  includes an outer section  102 . The outer section  102  is operably coupled to a first linear slide base  104  through linear bearings  106 . In some embodiments, the first linear slide is one of a plurality of linear slide bases. The one or more linear slide bases are constrained to move in a rectilinear motion with respect to each other by linear bearings  106 .  
         [0031]     In some embodiments one or more medical diagnostic apparatus  108  is mounted on the last of the plurality of linear slide bases. The “last” of the linear slide bases is the linear slide base that is mounted furthest away from the outer section  102 . For example, in System  100 , the last linear slide base is linear slide base  104 .  
         [0032]     In some embodiments, the outer section  102  is mountable to a supporting structure (not shown) of the apparatus, such as a ceiling. In those embodiments, the system  100  is suspended from a ceiling over an object that is to be imaged. The supporting structure includes a rotational mount and a carriage attached to the rotational mount. The carriage is mounted or mountable to two stages of overhead ceiling rails. The system  100  allows the medical apparatus  108  to be extended in the direction of the object, and positioned to image the object.  
         [0033]     In particular, the linear bearings  106  provide more precise constraint on movement; there is less play and sloppy movement in linear bearings than other forms of moveable attachments. The improved precision of constraint improves rigidity in system  100 , which in turn improves precision of motion in system  100 . The improved constraint reduces inconsistencies in moving efforts and stiffness, as well as reduces lost motion in the system. Furthermore, the rigidity and improved precision of motion of the linear bearings also improves clinical usage without the need for extensions to achieve a desired anatomical coverage range. In addition, consistency of assembly is also improved because the linear bearings require no adjustments in manufacturing of system  100 .  
         [0034]     The system level overview of the operation of an embodiment has been described in this section of the detailed description. A system to extend the position of imaging apparatus that implements sections connected by linear bearings has been described. System  100  is described as being asymmetrical because all of the linear motion means are on one side or one plane relative to a center line, the center line being line which pass thru and is surrounded by all the sections. For example, linear slide base  104  extends from outer section  102 .  
         [0035]     While the system  100  is not limited to any particular outer section  102 , linear slide base  104 , linear bearings  106  and medical diagnostic apparatus  108 , for sake of clarity simplified outer section  102 , linear slide base  104 , linear bearings  106  and medical diagnostic apparatus  108  has been described.  
         [0036]      FIG. 2  is a block diagram that provides a system level overview of an asymmetrical extending column that includes a synchronization mechanism to provide freedom of motion for general positioning of imaging apparatus at a desired location and orientation. System  200  solves the need in the art to reduce rubbing of J-bars against sections.  
         [0037]     System  200  includes an outer section  102 . The outer section  102  is operably coupled to a first linear slide base  104  through a synchronization mechanism  202 . Furthermore, a second linear slide base  206  is operably coupled to the first linear slide base  104  through a second synchronization mechanism  204 . In addition, the first synchronization mechanism  202  is operably coupled to the second synchronization mechanism  204  so that the linear slide bases  104  and  206  each slide in equal distances relative to each other. More specifically, when the first linear slide base  104  moves a distance in a direction relative to outer section  102 , the second linear slide base  206  will move the same distance in the same direction relative to the first linear slide base  104 . For example, when the first linear slide base  104  moves 1 centimeter forward relative to outer section  102 , the second linear slide base  206  will move 1 centimeter forward relative to the first linear slide base  104 , and second linear slide base  206  will move 2 centimeters forward relative to the outer section  102 .  
         [0038]     Synchronization mechanisms  202  and  204  eliminate the rubbing of J-bars against sections because the use of J-bars is eliminated in system  200 . The system level overview of the operation of an embodiment has been described in this section of the detailed description. A system to extend the position of imaging apparatus that implements sections connected by synchronization mechanisms has been described.  
         [0039]     While the system  200  is not limited to any particular outer section  102 , linear slide base  104  and  206 , synchronization mechanisms  202  and  204 , and medical diagnostic apparatus  108 , for sake of clarity simplified outer section  102 , linear slide base  104  and  206 , synchronization mechanisms  202  and  204  and medical diagnostic apparatus  108  has been described.  
         [0040]      FIG. 3  is a block diagram that provides a system level overview of a three-tiered extending column that includes synchronization mechanisms and linear bearings to provide freedom of motion for general positioning of imaging apparatus at a desired location and orientation. System  300  combines the components of system  100  and  200 , and solves problems that system  100  or system  200  solve.  
         [0041]     System  300  includes a liner bearing  302  that operably couples linear slide base  206  and linear slide base  104 .  
         [0042]     In system  300 , rubbing of J-bars against sections is eliminated because J-bars are not implemented in system  300 . The linear bearings  106  and  302  provide more precise constraint on movement because linear bearings have less play and sloppy movement than other forms of moveable attachments, which in turn improves rigidity in system  300 , which in turn improves precision of motion in system  300 . The more precise constraint reduces inconsistencies in moving efforts and stiffness, as well as reduces lost motion in the five-tiered extending column. Furthermore, consistency of assembly is also improved because the linear bearings require no adjustments in manufacturing of system  300 .  
       Apparatus of Embodiments  
       [0043]     In the previous section, a system level overview of the operation of an embodiment was described. In this section, the particular apparatus of such an embodiment are described by reference to a series of diagrams.  
         [0044]      FIG. 4  is an end cross section diagram of apparatus  400  according to an embodiment.  
         [0045]     In apparatus  400 , the outer section  102  in  FIG. 1  is implemented as a first open section  402  of the apparatus  400 . The first open section  402  has three sides  404 ,  406  and  408 . Side  406  is the middle side of first open section  402  because side  406  is located between sides  404  and  408 . Sides  404 ,  406  and  408  have inner faces  410 ,  412 ,  414  and outer faces  416 ,  418  and  420 , respectively. The first open section also includes a side  422  that is open. The open side  422  lacks closure, thus providing a concave, “U” shape to the first open section  402 . The open side  422  is opposite side  406 . The first open section  402  also has two ends that are not shown in this cross section diagram  400 , each end having an inner face and an outer face. First open section  402  and apparatus  400  also have a longitudinal axis, which is also not shown in  FIG. 4 . In apparatus  400 , the first linear slide base  104  is implemented as a second open section  424 . The second open section  424  is similar to the first open section  402  in that the second open section  424  is concave, but with one notable difference: The second open section  424  is smaller than the first open section  402  to the extent that second open section  424  fits into the first open section  402 . More specifically, the second open section  424  has outer dimensions that are smaller than the inner dimensions of the first open section  402 . The second open section  424  is an embodiment of the linear slide base  104  in  FIG. 1 .  
         [0046]     The second open section  424  has three sides  426 ,  428  and  430 . Side  428  is the middle side of second open section  424  because side  428  is located between sides  426  and  430 . Sides  426 ,  428  and  430  have inner faces  432 ,  434 ,  436  and outer faces  438 ,  440  and  442 , respectively. The second open section also includes a side  444  that is open. The open side  444  lacks closure, thus providing a concave, “U” shape to the second open section  424 . The open side  444  is opposite side  428 . The second open section  424  also has two ends that are not shown in this cross section diagram  400 , each end having an inner face and an outer face. Second open section  424  and apparatus  400  also have a longitudinal axis, which is also not shown in  FIG. 4 . The longitudinal axis of the second open section  424  is aligned in parallel with the longitudinal axis of the first open section  402 .  
         [0047]     The apparatus  400  also includes a first linear bearing assembly  446 . The first linear assembly  446  has a first side  448  and a second side  450 . Both sides  448  and  450  are parallel to a motion of the at least one first linear bearing assembly  446 . The first side  448  of the first linear bearing assembly  446  is mounted to the first open section  402  on the inner face  412  of the side  406  that is opposite the open side  422  of the first open section  402 . The second side  450  of the first linear bearing assembly  446  is mounted to the second open section  424  on the outer face  440  of the side  428  of the second open section  428  that is opposite the open side  444  of the second open section  424 .  
         [0048]     Implementing one linear bearing assembly in between each section, as in apparatus  400 , provides an apparatus that is easier to manufacture than other embodiments of apparatus  400  that include two linear bearing assemblies. Manufacturing the apparatus  400  with one linear bearing assembly  446  easier to manufacture because the one linear bearing assembly  446  does not require adjustments. Manufacturing the apparatus  400  with two or more linear bearing assemblies requires adjustment of the linear bearing assemblies to within about 20 micrometers over a 600 millimeter rail length to provide flatness, parallelism and straightness with sufficient freedom of movement of the sections. Apparatus  400  with two or more linear bearing assemblies is also more torsionally rigid. An apparatus  400  with one linear bearing assembly  446  does have slightly lower torsional rigidity than two linear bearing assemblies, and thus an apparatus  400  with one linear bearing assembly  446  requires a somewhat wider linear bearing assembly  446  than the width of the two linear bearing assemblies in order to provide a higher moment that will be more stable from side-to-side. The support structure of the linear slide base must be sufficiently massive to support the larger torsion moment from the single bearing assembly. Thus, apparatus  400  with two or more linear bearing assemblies is also lighter in weight.  
         [0049]      FIG. 5  is an end cross section diagram of apparatus  500  that includes synchronization mechanisms according to an embodiment. The gear, rack, and chain and sprocket synchronization mechanisms of apparatus  500  coordinate the motion of the sections, so that the sections extend in a proportional manner.  
         [0050]     Apparatus  500  also includes a first transportation mechanism  502 . The first transportation mechanism  502  has a first side  504  and a second side  506 . The first side  504  of the first transportation mechanism  502  is mounted to the first open section  402  on the inner face  412  of the side  406  that is opposite the open side  422  of the first open section  402 . The second side  506  of the first transportation mechanism  502  is mounted to the second open section  424  on the outer face  440  of the side  428  of the second open section  428  that is opposite the open side  444  of the second open section  424 .  
         [0051]     A third open section  508  has three sides  510 ,  512  and  514 . Side  512  is the middle side of third open section  508  because side  512  is located between sides  510  and  514 . Sides  510 ,  512  and  514  have inner faces  516 ,  518 ,  520  and outer faces  522 ,  524  and  526 , respectively. The second open section also includes a side  528  that is open. The open side  528  lacks closure, thus providing a concave, “U” shape to the second open section  446 . The open side  528  is opposite side  512 . The third open section  508  also has two ends that are not shown in this cross section diagram  500 , each end having an inner face and an outer face. Third open section  508  and apparatus  500  also have a longitudinal axis, which is also not shown in  FIG. 5 . The longitudinal axis of the third open section  508  is aligned in parallel with the longitudinal axis of the second open section  424 .  
         [0052]     Apparatus  500  also includes a second transportation mechanism  530 . The second transportation mechanism  530  has a first side  532  and a second side  534 . The first side  532  of the second transportation mechanism  530  is mounted to the second open section  424  on the inner face  434  of the side  428  that is opposite the open side  444  of the second open section  424 . The second side  534  of the second transportation mechanism  530  is mounted to the third open section  508  on the outer face  524  of the side  512  of the third open section  508  that is opposite the open side  528  of the third open section  508 .  
         [0053]     As the third open section  508  is extended a distance relative to the first open section  402 , the second open section  424  extends approximately ½ of the distance. By this means, complete and equal synchronization of the column sections  508 ,  424  and  402  is accomplished.  
         [0054]      FIG. 6  is a cross section block diagram of a five-tiered extending column  600  with covers on each section that includes gear, rack, and chain and sprocket synchronization mechanisms and linear bearings, according to an embodiment. Apparatus  600  solves the need in the art for an extending column that has improved precision of motion, reduced lost motion in the extending column, reduced rubbing of J-bars against sections, increased rigidity, as well as reduced size of the extending column.  
         [0055]     Five-tiered extending column  600  also includes a linear bearing assembly  448  that includes a linear bearing rail  602  and one or more linear bearing blocks  604 . The linear bearing rail  602  is attached to outer section  102  (e.g. first open section  402 ). The linear bearing rail  602  is operable to engage with the one or more linear bearing blocks  604 .  
         [0056]     The first moveable section  606  (e.g. second open section  424 ) is attached to the one or more linear bearing blocks  604 . The first moveable section  606  is attached to a linear bearing rail  608  that is in turn engaged to a linear bearing block  610 , that is in turn attached to a second moveable section  612  (e.g. third open section  508 ).  
         [0057]     The second moveable section  612  is attached to a linear bearing rail  614  that is in turn operable to engage a linear bearing block  616 , that is in turn attached to a third moveable section  618 .  
         [0058]     The third moveable section  618  is attached to a linear bearing rail  620  that is in turn engaged to a linear bearing block  622 , that is in turn attached to a fourth moveable section  624 . In some embodiments, the fourth moveable section  624  is attached to medical diagnostic apparatus  108  (not shown) such as an X-ray source and collimator.  
         [0059]     Attached to the first open section  402  is a gear rack  626  that is aligned approximately in parallel to linear bearing rail  602 . The gear rack  626  is engaged by a circular gear  628  mounted to a shaft  630 . The shaft  630  is rotatably mounted to the first movable section  606 .  
         [0060]     Attached to the shaft  640  is a sprocket  632  which is selected to have a pitch line diameter approximately equal to the pitch line diameter of the gear rack  626 . The sprocket  632  engage a chain  634  which forms a loop about an idler (not shown) wherein at least one side of the chain loop is constrained to move in a direction approximately parallel to linear bearing rail  608 . Note that the pitch line diameters can be slightly different, with the effect that the motions of the sections are not in the exact proportions. For small deviations, this is not objectionable.  
         [0061]     Attached to the chain  634  is a block  636 , which is also attached to the second movable section  612 .  
         [0062]     When the first movable section  606  is moved, the circular gear  628  rotatably engages the rack  626 , imparting rotational motion to the shaft  630  and thus to the sprocket  632 . The sprocket  632  drives the chain  634  which drives the block  636 , which in turn drives the second movable section  612 . With the pitchline diameter of the circular gear  628  approximately equal to the pitchline diameter of the sprocket  632 , the motion imparted to the second movable section  612  will be twice that motion which was imparted to the first movable section  402 . It should be noted that exact equality of pitchline diameters is not required.  
         [0063]     The synchronization apparatus is implemented twice more, with a gear rack  638  mounted to the second movable section  606  engaging a circular gear  640  on a shaft  642  mounted to the second movable section  606 , driving a sprocket  644  that in turn drives a chain  646  with a block  648  attached to the third movable section  612 , and again with a gear rack  650  mounted to the third movable section  612  engaging a circular gear  652  on a shaft  654  mounted to the third movable section  618 , driving a chain  656  with a block  658  attached to the fourth movable section  624 .  
         [0064]     As the fourth movable section is extended a distance, the third movable section extends approximately ¾ of the distance, the second movable section extends approximately ½ of the distance, and the first movable section extends approximately ¼ of the distance. Thus five-tiered extending column  600  provides complete synchronization of the column sections  402 ,  606 ,  612 ,  618  and  624  is accomplished.  
         [0065]     The shafts and gears of five-tiered extending column  600  can be of one piece, or the shaft and sprocket can be of one piece, and other variations can be implemented, such as a block being part of the section, as opposed to being a separate piece without departing from the spirit of the five-tiered extending column  600 .  
         [0066]     Furthermore, other components which perform the same function(s) as a gear, rack, and chain and sprockets are implemented without departing from the spirit of the five-tiered extending column  600 , for example, in some embodiments, the chain and sprockets replaced by a timing belt and timing belt sprockets, the gear and rack are replaced by a stationary chain with an ascending sprocket, etc.  
         [0067]     Sections  402 ,  606 ,  612 ,  618  and  624  have sufficient stiffness to provide torsional and bending rigidity for the five-tiered extending column  600 . In some embodiments, in which the sections  402 ,  606 ,  612 ,  618  and  624  are made from aluminum, the weight of the first open section  402  is at least 3.8 and not more than 15.2 pounds per lineal foot of extrusion. In the aluminum embodiment, fifth open section  624  has weight of at least 2.35 and not more than 9.4 pounds per lineal foot of extrusion. For intermediate sections  606 ,  612  and  618 , the weight is between a lower and upper limit, in proportion to the section location, according to the Formula 1 below: 
 
 Wn=W   1 +( n− 1)/( N− 1)*( WN−W   1 )   Formula 1 
 
         [0068]     In formula, n represents a section number counting from the innermost section, the fifth open section  624  and towards the outermost section, the first open section  402 , with the innermost section being equal to n=1. Furthermore, W represents a weight per foot of the section n. In addition, W 1  represents a weight per foot of the innermost section, the fifth open section  624 . In Formula 1, N represents account of the sections, which five in the five-tiered extending column  600 . WN represents a weight per foot of the outermost section, the first open section  402 .  
         [0069]     Applying Formula 1 to determine the lower limit of the weight per lineal foot of extrusion measured in pounds for the fifth open section  624  is shown in Formula 2 below: 
 
 W   2 =(2.35)+(1)/(4)*(3.8−2.35)=2.71 lbs/foot   Formula 2 
 
         [0070]     In Formula 2, where the weight per foot of the innermost section, the fifth open section  624 , W 1  is 2.35 lbs; and the weight per foot of the outermost section, the first open section  402 , WN is 3.8 lbs, the calculation indicates that the lower limit of the fourth open section  618  is 2.71 lbs/foot.  
         [0071]     Applying Formula 1 to determine the upper limit of the weight per lineal foot of extrusion measured in pounds for the fourth open section  618  is shown in Formula 3 below: 
 
 W   2 =(9.4)+(1)/(4)*(15.2−9.4)=10.85 lbs/foot   Formula 3 
 
         [0072]     In Formula 3, where the weight per foot of the innermost section, the fifth open section  624 , W 1  is 9.4 lbs; and the weight per foot of the outermost section, the first open section  402 , WN is 15.2 lbs, the calculation indicates that the lower limit of the fourth open section  618  is 10.85 lbs/foot.  
         [0073]     Applying Formula 1 to determine the lower limit of the weight per lineal foot of extrusion measured in pounds for the third open section  612  is shown in Formula 4 below: 
 
 W   3 =(2.35)+(2)/(4)*(3.8−2.35)=3.07 lbs/foot   Formula 4 
 
         [0074]     In Formula 4, where the weight per foot of the innermost section, the fifth open section  624 , W 1  is 2.35 lbs; and the weight per foot of the outermost section, the first open section  402 , WN is 3.8 lbs, the calculation indicates that the lower limit of the third open section  612  is 2.71 lbs/foot.  
         [0075]     Applying Formula 1 to determine the upper limit of the weight per lineal foot of extrusion measured in pounds for the third open section  612  is shown in Formula 5 below: 
 
 W   3 =(9.4)+(2)/(4)*(15.2−9.4)=12.3 lbs/foot   Formula 5 
 
         [0076]     In Formula 5, where the weight per foot of the innermost section, the fifth open section  624 , W 1  is 9.4 lbs; and the weight per foot of the outermost section, the first open section  402 , WN is 15.2 lbs, the calculation indicates that the upper limit of the third open section  618  is 12.3 lbs/foot.  
         [0077]     Applying Formula 1 to determine the lower limit of the weight per lineal foot of extrusion measured in pounds for the second open section  608  is shown in Formula 6 below: 
 
 W   4 =(2.35)+(3)/(4)*(3.8−2.35)=3.44 lbs/foot   Formula 6 
 
         [0078]     In Formula 6, where the weight per foot of the innermost section, the fifth open section  624 , W 1  is 2.35 lbs; and the weight per foot of the outermost section, the first open section  402 , WN is 3.8 lbs, the calculation indicates that the lower limit of the second open section  608  is 3.44 lbs/foot.  
         [0079]     Applying Formula 1 to determine the upper limit of the weight per lineal foot of extrusion measured in pounds for the second open section  608  is shown in Formula 7 below: 
 
 W   4 =(9.4)+(3)/(4)*(15.2−9.4)=13.7 lbs/foot   Formula 7 
 
         [0080]     In Formula 7, where the weight per foot of the innermost section, the fifth open section  624 , W 1  is 9.4 lbs; and the weight per foot of the outermost section, the second open section  608 , WN is 15.2 lbs, the calculation indicates that the upper limit of the second open section  608  is 13.7 lbs/foot.  
         [0081]     These lower and upper weights per foot for the sections refer to the average weight, which is the weight of the section, divided by the length of the section.  
         [0082]     Formula 1 is applicable to five-tiered extending column  600  as shown above, and to intermediate sections of a similar column design having a number of sections that is greater or less than five.  
         [0083]     In some embodiments, the sections are enclosed by covers. For example, the outer section  102  is attached to a cover  660 , the second open section  606  is attached to a cover  662 , the third open section  612  is attached to a cover  664 , the fourth open section  618  is attached to a cover  666 , and the fifth open section  624  is attached to a cover  668 . The covers improve stiffness of the five-tiered extending column  600  and protect the components and improves the aesthetics of the five-tiered extending column  600 .  
         [0084]     The linear bearings  106  provide more precise constraint on movement because linear bearings have less play and sloppy movement than other forms of moveable attachments. The improved precision of constraint improves rigidity in five-tiered extending column  600 , which in turn improves precision of motion in five-tiered extending column  600 . The improved constraint reduces inconsistencies in moving efforts and stiffness, as well as reduces lost motion in the five-tiered extending column. The rubbing of J-bars against sections is also eliminated because the use of J-bars is eliminated in five-tiered extending column  600 . Furthermore, the rigidity and improved precision of motion of the linear bearings also improves clinical usage without the need for extensions to achieve a desired anatomical coverage range. In addition, consistency of assembly is also improved because the linear bearings require no adjustments in manufacturing of five-tiered extending column  600 . Yet, the five-tiered extending column  600  also displaces a relatively small volume.  
         [0085]      FIG. 7  is a longitudinal cross section block diagram of a five-tiered extending column  700  in a retracted position with covers on each section that includes gear, rack, chain and sprocket synchronization mechanisms and linear bearings, according to an embodiment.  
         [0086]      FIG. 8  is an azimuthal cross section block diagram of a five-tiered extending column  800  in a fully retracted position without covers showing gear, rack, chain and sprocket synchronization mechanisms, according to an embodiment. The five-tiered extending column  800  includes a chain idler  802 .  
         [0087]      FIG. 9  is an azimuthal cross section block diagram of a five-tiered extending column  900  in an extended position without covers showing gear, rack, chain and sprocket synchronization mechanisms, according to an embodiment.  
         [0088]      FIG. 10  is a cross section block diagram of a five-tiered extending column  1000  in a partly extended position without covers showing gear, rack, chain and sprocket synchronization mechanisms, according to an embodiment. The first open section  402  is positioned closest in perspective, while the fifth open section  624  is extended away from the first open section and is furthest away in perspective.  
         [0089]      FIG. 11  is a side view of fifth open section of five-tiered extending column in an extended position with a drive, and X-ray source and a collimator mounted to the fifth open section, according to an embodiment.  
         [0090]     Apparatus  1100  includes an extending column  1102 . The extending column  1102  may be embodied as any one of the embodiments describe by systems  100 ,  200  and  300 ; apparatus  400  and  500 , extending columns  600 ,  700 ,  800 ,  900  and  1000 .  
         [0091]     A drive  1104  is mounted to the extending column  1102 , such as an electric drive, that positions an X-ray source  1106  and a collimator in one or more axis of movement, relative to the extending column  1100 . Apparatus  1100  provides a mechanized means of positioning the X-Ray source  1106  and the collimator  1108  that is faster and more precise than manual means of positioning the equipment.  
       Conclusion  
       [0092]     An extending column has been described. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations.  
         [0093]     In particular, one of skill in the art will readily appreciate that the names of the methods and apparatus are not intended to limit embodiments. Furthermore, additional methods and apparatus can be added to the components, functions can be rearranged among the components, and new components to correspond to future enhancements and physical devices used in embodiments can be introduced without departing from the scope of embodiments. One of skill in the art will readily recognize that embodiments are applicable to future medical diagnostic equipment, different materials, and new sprockets, gears, shafts, chains and bearings.  
         [0094]     The terminology used in this application with respect to linear bearing assemblies and synchronization mechanisms is meant to include all linear bearing assemblies and synchronization mechanisms and alternate technologies which provide the same functionality as described herein.