Anatomical Orientation Type Attribute
| Tag | (0010,2210) |
|---|---|
| Type | Conditionally Required (1C) |
| Keyword | AnatomicalOrientationType |
| Value Multiplicity | 1 |
| Value Representation | Code String (CS) |
The anatomical orientation type used in Instances generated by this equipment.
Enumerated Values:
- BIPED
-
- QUADRUPED
-
Required if the Patient is a non-human organism and the anatomical Frame of Reference is not bipedal. May be present otherwise. See Section C.7.6.1.1.1 and Section C.7.6.2.1.1.
Note
If this Attribute is not present, the default human standard anatomical position is used to define the patient orientation of projection images and the Patient-Based Coordinate System of cross-sectional images.
Section C.7.6.1.1.1
C.7.6.1.1.1 Patient Orientation
Patient Orientation (0020,0020) relative to the image plane shall be specified by two values that designate the anatomical direction of the positive row axis (left to right) and the positive column axis (top to bottom). The first entry is the direction of the rows, given by the direction of the last pixel in the first row from the first pixel in that row. The second entry is the direction of the columns, given by the direction of the last pixel in the first column from the first pixel in that column. Shall be consistent with Image Orientation (Patient) (0020,0037), if both Attributes are present and Patient Orientation (0020,0020) is not zero length.
If Anatomical Orientation Type (0010,2210) is absent or has a value of BIPED, anatomical direction shall be designated by abbreviations using the capital letters:
-
A (anterior)
-
P (posterior)
-
R (right)
-
L (left)
-
H (head)
-
F (foot)
If Anatomical Orientation Type (0010,2210) has a value of QUADRUPED, anatomical direction shall be designated by the abbreviations using capital letters:
-
LE (Le or Left)
-
RT (Rt or Right)
-
D (Dorsal)
-
V (Ventral)
-
CR (Cr or Cranial)
-
CD (Cd or Caudal)
-
R (Rostral)
-
M (Medial)
-
L (Lateral)
-
PR (Pr or Proximal)
-
DI (Di or Distal)
-
PA (Pa or Palmar)
-
PL (Pl or Plantar)
Note
-
These abbreviations are capitalized versions of those defined in Smallwood et al for describing radiographic projections. Because of the Code String (CS) Value Representation of Patient Orientation (0020,0020), lowercase letters cannot be used.
-
It is unfortunate that the conventional veterinary abbreviations (e.g., R for rostral and Rt for right) differ from those chosen for humans for DICOM usage (e.g., R for right), but confusion with in the respective human and non-human organism domains will be reduced. Hanging protocols may need to account for the difference by checking for the correct species.
-
Smallwood et al define an O (Oblique) abbreviation, which is useful for describing radiographic projections, but do not specify its use for directional terms, and hence it is not included here for describing the row and column directions.
-
The terms "anterior" and "posterior" are commonly used in vertebrate zoology to describe the cranial and caudal directions respectively, the veterinary terms are used in preference here, also in order to avoid confusion with the contradictory human use of anterior and posterior to mean ventral and dorsal.
-
For non-human organisms other than quadrupeds, for example, birds and fish, it is anticipated that the same nomenclature can be logically extended to describe, for example, wings and fins.
Each value of the orientation Attribute shall contain at least one of these abbreviations. If refinements in the orientation descriptions are to be specified, then they shall be designated by one or two additional abbreviations in each value. Within each value, the abbreviations shall be ordered with the principal orientation designated in the first abbreviations.
Note
-
For bipeds, since each abbreviation is a single character, no delimiter is required within a single value and none is used. For quadrupeds, though lowercase letters cannot be used, delimiters are not necessary within a single value to eliminate ambiguity, since the abbreviations used are sufficiently distinct, and can be parsed from left to right with a single character of lookahead.
-
E.g., a medio-lateral oblique projection of the left breast of a human might be encoded with Patient Orientation values of "A\FR" rather than "A\F", since the plane is obliquely inclined such that the columns are directed both downwards and medially, which for a left breast is towards the right, though the downwards direction is the principal column orientation.
-
E.g., a right dorsal-left ventral oblique view of a quadruped's abdomen might be encoded with Patient Orientation values of "LEV\CD", rather than "LE\CD", since the plane is obliquely inclined such that the rows are directed both to the left and ventrally, though the left direction is the principal row orientation. The abbreviations "LEV", "LE" and "CD", correspond to the designations in Smallwood et al of "LeV", "Le" and "Cd", respectively
Section C.7.6.2.1.1
C.7.6.2.1.1 Image Position and Image Orientation
Image Position (Patient) (0020,0032) specifies the x, y, and z coordinates of the upper left hand corner of the image; it is the center of the first voxel transmitted. Image Orientation (Patient) (0020,0037) specifies the direction cosines of the first row and the first column with respect to the patient. These Attributes shall be provide as a pair. Row value for the x, y, and z axes respectively followed by the Column value for the x, y, and z axes respectively.
The direction of the axes is defined fully by the patient's orientation.
If Anatomical Orientation Type (0010,2210) is absent or has a value of BIPED, the x-axis is increasing to the left hand side of the patient. The y-axis is increasing to the posterior side of the patient. The z-axis is increasing toward the head of the patient.
If Anatomical Orientation Type (0010,2210) has a value of QUADRUPED, the
-
x-axis is increasing to the left (as opposed to right) side of the patient
-
the y-axis is increasing towards
-
the dorsal (as opposed to ventral) side of the patient for the neck, trunk and tail,
-
the dorsal (as opposed to ventral) side of the patient for the head,
-
the dorsal (as opposed to plantar or palmar) side of the distal limbs,
-
the cranial (as opposed caudal) side of the proximal limbs, and
-
-
the z-axis is increasing towards
-
the cranial (as opposed to caudal) end of the patient for the neck, trunk and tail,
-
the rostral (as opposed to caudal) end of the patient for the head, and
-
the proximal (as opposed to distal) end of the limbs
-
Note
-
The axes for quadrupeds are those defined and illustrated in Smallwood et al for proper anatomic directional terms as they apply to various parts of the body.
-
It should be anticipated that when quadrupeds are imaged on human equipment, and particularly when they are position in a manner different from the traditional human prone and supine head or feet first longitudinal position, then the equipment may well not indicate the correct orientation, though it will remain an orthogonal Cartesian right-handed system that could be corrected subsequently.
The Patient-Based Coordinate System is a right handed system, i.e., the vector cross product of a unit vector along the positive x-axis and a unit vector along the positive y-axis is equal to a unit vector along the positive z-axis.
Note
If a patient is positioned parallel to the ground, in dorsal recumbency (i.e., for humans, face-up on the table), with the caudo-cranial (i.e., for humans, feet-to-head) direction the same as the front-to-back direction of the imaging equipment, the direction of the axes of this Patient-Based Coordinate System and the Equipment-Based Coordinate System in previous versions of this Standard will coincide.
The Image Plane Attributes, in conjunction with the Pixel Spacing Attribute, describe the position and orientation of the image slices relative to the Patient-Based Coordinate System. In each image frame Image Position (Patient) (0020,0032) specifies the origin of the image with respect to the Patient-Based Coordinate System. RCS and Image Orientation (Patient) (0020,0037) values specify the orientation of the image frame rows and columns. The mapping of an integer (entire) pixel location (i,j) to the RCS is calculated as follows:
Equation C.7.6.2.1-1.
Where:
-
Pxyz The coordinates of the voxel (i,j) in the frame's image plane in units of mm.
-
Sxyz The three values of Image Position (Patient) (0020,0032). It is the location in mm from the origin of the RCS.
-
Xxyz The values from the row (X) direction cosine of Image Orientation (Patient) (0020,0037).
-
Yxyz The values from the column (Y) direction cosine of Image Orientation (Patient) (0020,0037).
-
i Column integer index to the image plane. The first (entire) column is index zero.
-
Δi Column pixel resolution of Pixel Spacing (0028,0030) in units of mm.
-
j Row integer index to the image plane. The first (entire) row index is zero.
-
Δj Row pixel resolution of Pixel Spacing (0028,0030) in units of mm.
Note
The integer entire row and column indices (i,j) that are the input to this equation start from zero, which is a common mathematical convention. Many DICOM Attributes define such indices as starting from one, e.g., those affected by Bounding Box Annotation Units (0070,0003) for PIXEL and MATRIX in Section C.10.5 Graphic Annotation Module. This needs to be accounted for when applying this equation literally.
The mapping of a sub-pixel resolution image or total pixel matrix relative location (c,r), such as used in Spatial Coordinates Macro, to the RCS is calculated as follows
Equation C.7.6.2.1-2.
Where:
-
Pxyz The coordinates of the voxel (c,r) in the frame's image plane in units of mm.
-
Sxyz The three values of Image Position (Patient) (0020,0032). It is the location in mm from the origin of the RCS.
-
Xxyz The values from the row (X) direction cosine of Image Orientation (Patient) (0020,0037).
-
Yxyz The values from the column (Y) direction cosine of Image Orientation (Patient) (0020,0037).
-
c Column sub-pixel resolution index to the image plane. The left pixel edge of the first column of the frame or total pixel matrix is index zero.
-
Δc Column pixel resolution of Pixel Spacing (0028,0030) in units of mm.
-
r Row sub-pixel resolution index to the image plane. The top pixel edge of the first row of the frame or total pixel matrix index is zero.
-
Δr Row pixel resolution of Pixel Spacing (0028,0030) in units of mm.
Additional constraints apply:
-
The row and column direction cosine vectors shall be orthogonal, i.e., their dot product shall be zero.
-
The row and column direction cosine vectors shall be normal, i.e., the dot product of each direction cosine vector with itself shall be unity.