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 examples that may be practiced . these examples are described in sufficient detail to enable one skilled in the art to practice the subject matter , and it is to be understood that other examples may be utilized and that logical , mechanical , electrical and other changes may be made without departing from the scope of the subject matter of this disclosure . the following detailed description is , therefore , provided to describe an exemplary implementation and not to be taken as limiting on the scope of the subject matter described in this disclosure . certain features from different aspects of the following description may be combined to form yet new aspects of the subject matter discussed below . when introducing elements of various embodiments of the present disclosure , the articles “ a ,” “ an ,” “ the ,” and “ said ” are intended to mean that there are one or more of the elements . the terms “ comprising ,” “ including ,” and “ having ” are intended to be inclusive and mean that there may be additional elements other than the listed elements . spinal images may be annotated and / or labeled to assist in analyzing such images and / or diagnosing various spine diseases . however , correctly annotating and / or labeling these images is sometimes difficult because , depending on the image being viewed , the number of visible vertebrae and / or disc vary . this can be especially difficult in the case of axial spine images . to overcome some of the deficiencies encountered with some known manual or automatic annotating and / or labeling methods , aspects of the present disclosure disclosed and described herein enable the standalone , automatic labeling of axial spine images using a comprehensive set of geometric measurements of the human spine as input parameters , ( e . g ., vertebra height and axial area ). in addition , aspects disclosed may also annotate axial spine images without the need for : 1 ) referring to sagittal view annotations , 2 ) referring to cross - reference features , and 3 ) requiring external training while being applicable to different imaging modalities and acquisition protocols . other aspects , such as those discussed below and others as can be appreciated by one having ordinary skill in the art upon reading the enclosed description , are also possible . fig1 depicts an example system 100 for annotating images such , as spinal images , according to one aspect of the present disclosure . system 100 includes a computer 102 and an annotator 104 communicatively coupled to computer 102 . in this example , computer 102 includes a user interface 106 and a data input ( e . g ., a keyboard , mouse , microphone , etc .) 108 and annotator 104 includes a processor 110 and a database 112 . in certain aspects , user interface 106 displays data such as images ( e . g ., spinal images , radiology images , etc .) and / or annotated images received from annotator 104 . in certain aspects , user interface 106 receives commands and / or input from a user 114 via data input 108 . in aspects where system 100 is used to annotate spinal images , user interface 106 displays a spinal image ( s ) and / or annotated spinal image ( s ) and user 114 provides an initial input identifying , for example , a location of a vertebra on the spinal image ( s ) and / or provides subsequent input identifying the location of a vertebra based on offline , a priori external training . fig2 illustrates a flow diagram of annotator 104 according to one aspect of the present disclosure . while annotator 104 may generate annotations using any suitable labeling algorithm , in some aspects , annotator 104 generates annotations based on a hierarchy of feature levels , where pixel classifications 202 via non - linear probability product kernels ( ppk ) are followed by classifications of 2d slices 204 , 3d single vertebra structures 206 , and 3d multiple vertebrae structures 208 . in some aspects , annotator 104 embeds robust geometric priors based on anatomical measurements that are well known to those skilled in the relevant art ( s ) ( e . g ., vertebra height and axial area ). in certain aspects , efficient pixel - level classifications 202 via integral kernels are used . in one aspect , a non - linear classifier is used , which determines whether the neighborhood of each pixel p matches a target distribution denoted p l . certain aspects can use offline , external training to set an initial vertebrae pixel location to provide initial classifications . in another aspect , user 114 can select a single point p 0 =( x 0 , y 0 ) within the vertebral region in a single 2d axial slice in the series via data input 108 to provide initial training . then , the target distribution p l is learned from a window of size w × h centered at p 0 . in one aspect , neighborhood distributions contain contextual information , which provides much richer inputs to the classifier than individual - pixel intensities . for example , let d j : ω ⊂ 2 → , j ∈[ 1 . . . n ], be a set of input images , which correspond to the axial slices of a given spine series . ω is the image domain and nis the number of slices in the series . for each d ∈{ d j , j = 1 . . . n } and each pixel p :( x , y )∈ ω , a non - linear kernel based classifier is created using the following : where p l , is the a priori learned distribution , ρ is a constant and p p , w , d is the kernel density estimate ( kde ) of the distribution of the data d within window w centered at pixel p =( x , y )∈ ω : [ w ] is the number of pixels within w and z is a finite set of bins encoding the space of image variables . k z d is a dirac kernel : k z d = δ ( z − d ( p )), where δ ( t )= 1 if t = 0 , and 0 elsewhere . in certain aspects , a gaussian kernel can be used instead of δ . φ is a probability product kernel which measures the degree of similarity between two distributions : φ ( p p , w , d , p l )= σ z ∈ z [ p p , w , d ( z ) p l ( z )] bγ , γ ∈[ 0 , 1 ] equation 2 : in certain aspects , an efficient method to determine kernel density estimates and ppk evaluations for large images and arbitrary window sizes via integral kernels can be computed as integral images as follows : given an image , the corresponding integral image is defined as the sum of all pixel intensities to the left and above the current pixel : ℑ d ( x , y )= σ u ≦ x σ v ≦ y d ( u , v ). the sum of intensities of all pixels within an arbitrary rectangular can be computed from ℑ d using only the corners of the rectangle : σ u = x 1 x 2 σ v = y 1 y 2 d ( u , v )= ℑ d ( x 1 , y 1 )+ ℑ d ( x 2 , y 2 )− ℑ d ( x 1 , y 2 )− ℑ d ( x 2 , y 1 ) equation 3 : where ( x 1 , y 1 ) are the coordinates of the upper left corner of the rectangle and ( x 2 , y 2 ) are those of the lower right corner . in certain aspects , integral images can be treated as integral kernels to enable the computation of the ppk in equation 2 as follows : for each slice a set of separate kernel images defined over ω : , , . . . , , z ∈ , ( with the dirac kernel defined earlier ) are created . next , an integral kernel image is computed based on each k z : ( x , y )= σ u ≦ x σ v ≦ y ( u , v ). can be computed from the integral kernel images using five operations for each p =( x , y )∈ ω : where with w and h being the width and height of . in certain aspects , 2d slice - level features 204 are derived from the area of pixels classified as vertebra in a given 2d slice and from geometric priors . vertebra pixels are grouped into sets of 4 - connected regions : s i , i = 1 , 2 , . . . . these regions are then filtered , building a set s as follows : s ={ s i | area ( s i & gt ; a min and ∥ c i , p 0 ∥& lt ; d max }, where a min and d max are pre - specified geometric priors , which for example , can be defined so as to reflect human spine measurements that are well known in the clinical literature . if s ≠ ø , the area of the largest region in s is used as a 2d slice - level feature for the next step . otherwise , a value of 0 is assigned to this feature . this feature is denoted as a k for slice . in certain aspects , 3d single - vertebra classifications 206 are identified . an input set of adjacent slices , k ⊂[ 1 , n ], in the neighborhood of a vertebrae are used . these slices are all the slices within a geometric prior height h s , either centered on the initial point or starting at the uppermost ( or lowermost ) slice of a previously identified vertebra . the slices are then classified ( labeled ) as either being vertebra or intervertebral disk . the input of this step uses the 2d slice - level feature computed at the previous step ( a k ). a one - dimensional smoothing filter is then applied to the features of the adjacent slices a k 2 = a k * k , where a k s is the smoothed data and k is a one - dimensional convolution kernel . a slice is classified as vertebra if a k s & gt ; t area , where t area is a threshold given by t area = c a μ area , with c a a user defined factor , for example , and μ area the average of areas a k s . if the set of adjacent slices classified as vertebrae results in a vertebral height larger than a geometric prior h min , then the 3d set of adjacent slices is classified as vertebra . in certain aspects , the geometric priors h s and h min can be defined from well - known anatomical measurements from the literature . in certain aspects , an iterative model using 3d multiple vertebrae classification 208 updating is employed to improve classification accuracy . using the previously found vertebra , the distribution p l and search region are updated as necessary for finding the next vertebra . the classification or labeling then proceeds in both vertical directions of the spine . for the first vertebra , the initial search height , which is denoted as h s 0 can be defined to be twice the height of a vertebra ( which may be obtained from the literature , for example ), and centered at the input point , for example . for finding subsequent vertebrae , the search range h s can begin at the boundary of the previous vertebra and extends for the height of a vertebra plus two inter - vertebral disc spaces ( which may also be obtained from the literature ), for example . a flowchart representative of example machine readable instructions for implementing the axial image annotation process 300 of the example system 100 is shown in fig3 . in these examples , the machine readable instructions comprise a program for execution by a processor such as processor 412 shown in the example processor platform 400 discussed below in connection with fig4 . the program can be embodied in software stored on a tangible computer readable storage medium such as a cd - rom , a floppy disk , a hard drive , a digital versatile disk ( dvd ), a blu - ray ™ disk , or a memory associated with processor 412 , but the entire program and / or parts thereof could alternatively be executed by a device other than processor 412 and / or embodied in firmware or dedicated hardware . further , although the example program is described with reference to the flowchart illustrated in fig3 , many other methods of implementing the example annotator can alternatively be used . for example , the order of execution of the blocks can be changed , and / or some of the blocks described can be changed , eliminated , or combined . as mentioned above , process 300 may be implemented using coded instructions ( e . g ., computer and / or machine readable instructions ) stored on a tangible computer readable storage medium such as a hard disk drive , a flash memory , a read - only memory ( rom ), a compact disk ( cd ), a digital versatile disk ( dvd ), a cache , a random - access memory ( ram ) and / or any other storage device or storage disk in which information is stored for any duration ( e . g ., for extended time periods , permanently , for brief instances , for temporarily buffering , and / or for caching of the information ). as used herein , the term tangible computer readable storage medium is expressly defined to include any type of computer readable storage device and / or storage disk and to exclude propagating signals and to exclude transmission media . as used herein , “ tangible computer readable storage medium ” and “ tangible machine readable storage medium ” are used interchangeably . additionally or alternatively , process 300 may be implemented using coded instructions ( e . g ., computer and / or machine readable instructions ) stored on a non - transitory computer and / or machine readable medium such as a hard disk drive , a flash memory , a read - only memory , a compact disk , a digital versatile disk , a cache , a random - access memory and / or any other storage device or storage disk in which information is stored for any duration ( e . g ., for extended time periods , permanently , for brief instances , for temporarily buffering , and / or for caching of the information ). as used herein , the term non - transitory computer readable medium is expressly defined to include any type of computer readable storage device and / or storage disk and to exclude propagating signals and to exclude transmission media . as used herein , when the phrase “ at least ” is used as the transition term in a preamble of a claim , it is open - ended in the same manner as the term “ comprising ” is open ended . process 300 begins at block 302 where computer 102 receives , via data input 108 , initial input on a spine image displayed at user interface 106 and / or stored in database 112 ( block 302 ). in certain aspects of the present disclosure , to provide the initial training , the initial input is associated with a user 114 clicking on a point p =( x 0 , y 0 ) within the vertebral region in a single 2d axial slice of the spinal image series . in certain aspects , the initial training input is provided by previous , off - line , external training from another data set . at block 304 , annotator 104 generates a target distribution p l which is learned from a window of size w × h centered at p 0 . at block 306 , annotator 104 sets the initial search height h s 0 , which is defined to be twice the height of an average vertebra ( as defined in the clinical literature ). for each slice d j in the set of slices within the search height h s , the annotator 104 performs a pixel classification and a 2d slice classification . at block 308 , the pixel classification is performed by using sign ( φ ( p l )− ρ ) to classify each pixel p via integral kernels as described above . at block 310 , the slice classification is performed by computing the 2d slice - level feature a j . at block 312 , annotator 104 determines if all of the slices within the search height h s have been completed . if not , the pixel and slice classification is performed on the next slice in the series . at block 314 , once all the slices have been classified at the pixel and slice levels , the vertebra classification is performed by computing the smoothed features a j s for each d j within the search height h s . in addition , at block 316 , the annotator then determines the uppermost and lowermost slices for the current vertebra by using the equation sign ( a j 2 − t area ). at block 318 , annotator 104 updates the vertical search height h s and target distribution p l . at block 320 , annotator 104 determines if all the vertebrae have been completed . if not , at block 322 , annotator 104 determines if the current vertebra being examined , v n , is lower than the top - most vertebra v max . if so , the vertebra is incremented at block 324 ( v n = v n + 1 ) and the process of classifying the vertebra begins again at block 308 . if the vertebra v n is already at v max then the current vertebra being examined is reset at block 326 ( v n = v 0 ) and annotator 104 determines if the vertebra being examined is higher than the lower - most vertebra at block 328 ( v n & gt ; v min ). if so , the vertebra being examined is decremented at block 330 ( v n = v n − 1 ) and the process of classifying the vertebra continues at block 308 . once annotator 104 determines that all the vertebra have been completed , annotator 104 assigns labels to the disks . in certain aspects , annotator 104 also labels the intervertebral discs in between the vertebrae . in certain aspects , the annotated spine including vertebrae and disc labels is displayed to user 114 using user interface 106 and / or saved in database 112 . the subject matter of this description may be implemented as stand - alone system or for execution as an application capable of execution by one or more computing devices 102 . the application ( e . g ., webpage , downloadable applet or other mobile executable ) can generate the various displays or graphic / visual representations described herein as graphic user interfaces ( guis ) or other visual illustrations , which may be generated as webpages or the like , in a manner to facilitate interfacing ( receiving input / instructions , generating graphic illustrations ) with users via the computing device ( s ). memory and processor 110 as referred to herein can be stand - alone or integrally constructed as part of various programmable devices , including for example a desktop computer , tablet , mobile device or laptop computer hard - drive , field - programmable gate arrays ( fpgas ), application - specific integrated circuits ( asics ), application - specific standard products ( assps ), system - on - a - chip systems ( socs ), programmable logic devices ( plds ), etc . or the like or as part of a computing device , and any combination thereof operable to execute the instructions associated with implementing the method of the subject matter described herein . computing device as referenced herein may include : a mobile telephone ; a computer such as a desktop or laptop type ; a personal digital assistant ( pda ) or mobile phone ; a notebook , tablet or other mobile computing device ; or the like and any combination thereof . computer readable storage medium or computer program product as referenced herein is tangible ( and alternatively as non - transitory , defined above ) and may include volatile and non - volatile , removable and non - removable media for storage of electronic - formatted information such as computer readable program instructions or modules of instructions , data , etc . that may be stand - alone or as part of a computing device . examples of computer readable storage medium or computer program products may include , but are not limited to , ram , rom , eeprom , flash memory , cd - rom , dvd - rom or other optical storage , magnetic cassettes , magnetic tape , magnetic disk storage or other magnetic storage devices , or any other medium which can be used to store the desired electronic format of information and which can be accessed by the processor or at least a portion of the computing device . the terms module and component as referenced herein generally represent program code or instructions that causes specified tasks when executed on a processor . the program code can be stored in one or more computer readable mediums . network as referenced herein may include , but is not limited to , a wide area network ( wan ); a local area network ( lan ); the internet ; wired or wireless ( e . g ., optical , bluetooth , radio frequency ( rf )) network ; a cloud - based computing infrastructure of computers , routers , servers , gateways , etc . ; or any combination thereof associated therewith that allows the system or portion thereof to communicate with one or more computing devices . the term user and / or the plural form of this term is used to generally refer to those persons capable of accessing , using , or benefiting from the present disclosure . fig4 is a block diagram of an example processor platform 400 capable of executing process 300 for annotating images such as spinal images . processor platform 400 may be , for example , a server , a personal computer , a mobile device ( e . g ., a cell phone , a smart phone , a tablet such as an ipad ™), a personal digital assistant ( pda ), an internet appliance , or any other type of computing device . processor platform 400 includes a processor 412 . processor 412 of the illustrated example is hardware . for example , processor 412 may be implemented by one or more integrated circuits , logic circuits , microprocessors or controllers from any desired family or manufacturer . processor 412 includes a local memory 413 ( e . g ., a cache ). processor 412 of the illustrated example is in communication with a main memory including a volatile memory 414 and a non - volatile memory 416 via a bus 418 . volatile memory 414 can be implemented by synchronous dynamic random access memory ( sdram ), dynamic random access memory ( dram ), rambus dynamic random access memory ( rdram ) and / or any other type of random access memory device . the non - volatile memory 416 can be implemented by flash memory and / or any other desired type of memory device . access to main memory 414 , 416 is controlled by a memory controller . processor platform 400 also includes an interface circuit 420 . interface circuit 420 can be implemented by any type of interface standard , such as an ethernet interface , a universal serial bus ( usb ), and / or a pci express interface . one or more input devices 422 are connected to the interface circuit 420 . input device ( s ) 422 permit ( s ) a user to enter data and commands into processor 412 . the input device ( s ) can be implemented by , for example , an audio sensor , a microphone , a camera ( still or video ), a keyboard , a button , a mouse , a touchscreen , a track - pad , a trackball , isopoint and / or a voice recognition system . one or more output devices 424 are also connected to interface circuit 420 of the illustrated example . output devices 424 can be implemented , for example , by display devices ( e . g ., a light emitting diode ( led ), an organic light emitting diode ( oled ), a liquid crystal display , a cathode ray tube display ( crt ), a touchscreen , a tactile output device , a light emitting diode ( led ), a printer and / or speakers ). interface circuit 420 of the illustrated example , thus , typically includes a graphics driver card , a graphics driver chip or a graphics driver processor . interface circuit 420 of the illustrated example also includes a communication device such as a transmitter , a receiver , a transceiver , a modem and / or network interface card to facilitate exchange of data with external machines ( e . g ., computing devices of any kind ) via a network 426 ( e . g ., an ethernet connection , a digital subscriber line ( dsl ), a telephone line , coaxial cable , a cellular telephone system , etc .). processor platform 400 of the illustrated example also includes one or more mass storage devices 428 for storing software and / or data . examples of such mass storage devices 428 include floppy disk drives , hard drive disks , compact disk drives , blu - ray disk drives , raid systems , and digital versatile disk ( dvd ) drives . coded instructions 432 may be stored in mass storage device 428 , in volatile memory 414 , in the non - volatile memory 416 , and / or on a removable tangible computer readable storage medium such as a cd or dvd . this written description uses examples to disclose the subject matter , and to enable one skilled in the art to make and use the invention . the above disclosed methods and apparatus disclosed and described herein enable the standalone automatic labeling of axial spine images . from the foregoing , it will be appreciated that the above disclosed methods and apparatus provide a protocol the enables fast and user - friendly visualizations of spine annotations and / or substantially guarantees correct results in substantially all clinical scenarios . the patentable scope of the subject matter is defined by the following claims , and may include other examples that occur to those skilled in the art . such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims , or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims .