Patent Abstract:
a heading positioning apparatus and the method of use for cone - beam computed tomography , and single photon emission computed tomography .

Detailed Description:
vertical position of the head : the position of the head in a direction in line with the body , related to raising or lowering the head within the cone beam ct apparatus longitudinal position of the head : the anterior - posterior positioning of the head , related to the movement forward and backward medial / lateral movement : movement of the head toward the center or away from the center of the normal head positions , related to the turning of the head toward or away from the center of the bite position . an illustration of an embodiment of the head positioning device of this invention is shown in fig1 , with isometric and exploded views shown in fig2 . an inventive head positioning device comprises a biteplate attachment ( a ), an adjustable vertical positioning post ( b ) adapted to engage and hold the biteplate attachment and a base adapter ( c ) that is adapted to engage and hold the vertical post , and can be attached to a cbct machine . the head positioning of this invention is an improvement over the existing head positioning apparatuses because the use of a biteplate , which prevents the deformation of soft tissue of the face due to the use of a chin cup or strap during scanning , particularly around the jaw . the bite plate also allows a separation of upper and lower teeth by a predefined vertical distance of the thickness of the biteplate . the inventive device allows small precise vertical and longitudinal ( anterior / posterior ) adjustment of the head position by moving the vertical positioning post up and down through the base adapter using a thumbwheel ( d ) and screws ( b ) on the base adapter . it also helps the subject to maintain a fixed facial expression immediately before and after the cbct scan for photograph or 3 - d scan . the head positioning device of this invention is intended to align and localize the position of a human subject &# 39 ; s head in a cone beam ct ( cbct ) scanner , relative to the scanner &# 39 ; s field of view , without impinging on the soft tissue of the face and neck , while helping the subject to maintain a constant facial expression ( fig1 ). the inventive head positioning device also provides a means to adjust the vertical and longitudinal ( anterior / posterior ) positions of the subject &# 39 ; s head relative to the cbct scanner &# 39 ; s field of view , while restricting medial / lateral movements , and any rotations of the head . restricted head motion ensures high quality scan images and reduces motion artifacts , so that the intended anatomy appears within the field of view clearly . lastly , the biteplate attachment provides a means to maintain constant distance between the teeth , and assist in fixing the subject &# 39 ; s facial expression . fixed facial expression is necessary for registration of post - cbct photographs , or three dimensional scans , with the volume captured by the cbct scanner in order to make an accurate registration of the two images . changes in facial expression between the cbct and three dimensional surfaces reconstructed from photographs will adversely affect the accuracy of image registration . the photographs need to be precisely registered to soft tissue boundaries within the reconstructed cbct data . the biteplate attachment ( a ) is a removable component of the inventive device , providing a mechanical interface with the subject , and fixture of the subject &# 39 ; s head position . an embodiment of a biteplate attachment comprises a dental biteplate ( l ), and a position tab ( g ) projecting outward from the middle of the dental plate ( see fig2 ). the dental plate ( l ) is adapted for insertion into the mouth of a subject ( see fig1 ). dental biteplate designs may be varied in shape and size to accommodate different mouth dimensions , arch - forms , and malocclusions . type indicators may be engraved in a conspicuous location on the biteplate ( e . g . “ m ” for medium , fig4 ). thickness of the dental plate sets a precise gap between the subject &# 39 ; s upper and lower teeth , which may be in the range of approximately 0 . 2 - 5 mm and preferably in the range of approximately 1 - 3 mm . the position tab ( g ) is adapted to be inserted into a keyslot located on the top end of the adjustable vertical position post , and may move freely within the keyway or locked down to at a desired position . in one embodiment , the positioning tab ( g ) has notches in equal interval , which allowing precious readings of the distance between the dental biteplate and the vertical positioning post . the notches are also part of the locking mechanism allowing it to be locked to the vertical positioning post . while engaged in the vertical post , stiffness of the biteplate tab needs to resist head motions . the cross - section of the tab is designed to maximize bending stiffness and minimize motion when engaged in the keyed slot ( f ) on the vertical position post ( c ). the oral biteplate may be made of any radiolucent , sanitary ( usp class i - vi ) polymer material possessing sufficient elastic modulus to provide necessary structural stiffness , adequate yield strength to insure head position is maintained under normal forces , and low enough friction coefficient ( in interface with the linear bearing surface and thumbwheel treads ) to provide smooth insertion into the key slot . an example of such material is abs polymer . the position tab and the dental biteplate may be made of different or the same material , but are both intended to be disposable . the vertical positioning post ( b ) features a specially designed cross - section intended to maximize bending and torsional stiffness , while minimizing linear bearing . a cross - section shape ( j ) is shown in fig5 . helical thread may be cut into the medial and lateral surfaces of the vertical positioning post ( b ). this thread is matched to the internal thread ( i ) of the captive thumbwheel ( d ), which is engaged on the thread notches of the vertical positioning post ( b ). a linear bearing journal ( h ), which is integral to the base adapter , holds the vertical post with a single degree of freedom . mechanical tolerances between the vertical post , linear bearing surface , and thumbwheel internal threads are set to provide smooth vertical post height adjustment with minimal slip , hysteresis , or torsional play . the vertical positioning post may be fabricated from the same radiolucent abs material as the biteplate attachment or other materials such as resin , photopolymers , injection molded plastics or other materials with the same physical characteristics . some examples include polycarbonate , nylon , ptfe , peek , pekk , fiber - reinforced composite , or ceramics . the base adapter ( c ) is adapted directly from the specifications of an original positioning device supplied by the different cbct scanners . a base adapter normally comprises a chin rest affixing a patient &# 39 ; s head position vertically . the major improvements to the base adapter include : integration of the special cross - section ( j ), linear bearing journal ( h ), the height adjustment thumbwheel ( d ), and incorporation of a gusset ( k ) to improve structural stiffness . fig6 shows head positioning using a device of the present invention and a base adapter for the kodak k9500 cbct scanner . the subject &# 39 ; s chin is slightly above the base adapter , insuring that the inferior mandible to be within the cbct &# 39 ; s field of view . the vertical post and base adapter can be fabricated using any material with similar radiolucency , elastic modulus , yield strength and friction coefficient as abs . base and vertical post specifications can be varied to adapt to other cbct scanners . in an exemplary use of the inventive device , a subject first places the dental biteplate ( l ) of a biteplate attachment ( a ) in the mouth , and is then asked to clench his / her teeth onto the dental biteplate ( l ) as illustrated in fig1 . the positioning tab ( g ) of the biteplate attachment ( a ) is then locked into the vertical positioning post ( b ) as illustrated in fig4 to ensure correct alignment in the scanner &# 39 ; s field of view . in one embodiment , the positioning tab ( g ) extending from the dental biteplate is inserted into a key slot ( f ) located on the top of the vertical positioning post ( b ). to engage the biteplate attachment into the vertical positioning post , a cbct operator pulls back spring tab ( e ) within the key slot ( f ) with a thumb and forefinger , allowing the positioning tab to slide freely though the key slot ( f ). once the subject &# 39 ; s head is in the desired longitudinal ( anterior / posterior ) position , the spring tab ( e ) is released , allowing a pin to engage the notches on the biteplate ( g ), and locking the dental biteplate in position . longitudinal position can be locked to any one of the discrete positions of the notches on the biteplate tab ( g ). the vertical position of the biteplate may be adjusted by raising or lowering the vertical positioning post as shown in fig4 . in one embodiment , the cbct operator turns a thumbwheel ( d ) to move the vertical post to a desired height , and lock it in position . fig5 shows the details of the vertical post ( b ) interface with the base adapter ( c ) when a subject is correctly positioned using the inventive device . a linear bearing journal ( h ), integral to the base adapter , holds the vertical post with a single degree of freedom . threads on the sides of the vertical post ( b ) engage the internal thread ( i ) of a captive thumbwheel ( d ). rotation of the thumbwheel ( d ) slides the vertical post along its only degree of freedom ( up and down ), while friction in the threads hold the desired position . the cbct operator can gauge precise height adjustment by the number of turns of the thumbwheel multiplied by the pitch of the thread . when the cbct scan is completed , the biteplate is released from the vertical adjustment post by lifting the spring tap with a thumb and fore finger , backing out the position tab of the biteplate attachment out of the key slot ( f ) as the subject continues to clench the biteplate in their teeth . while the subject retains the biteplate in this manner , the same facial expression is maintained , and captured for post - cbct photographs . using a variety of available cameras and techniques , a set of photographs can be reconstructed into an accurate three dimensional surface containing additional information not captured in the cbct scan , ion particular skin color , eye color , and hair color cranial anatomy outside of the cbct field of view ( fov ). 1 . nizam a , gopal l , hakim a , samsudin a : dimensional accuracy of the skull models produced by rapid prototyping technology using steriolithography appartatus . arch oro sciences 2006 ; 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