Object Pixel Spacing in Center of Beam Attribute
| Tag | (0018,9404) |
|---|---|
| Type | Conditionally Required (1C) |
| Keyword | ObjectPixelSpacingInCenterOfBeam |
| Value Multiplicity | 2 |
| Value Representation | Single (FL) |
Physical distance within the anatomic region of interest in the center of the beam and perpendicular to the beam between the center of each pixel, specified by a numeric pair adjacent row spacing (delimiter) adjacent column spacing in mm. See Section C.8.19.6.9.2. See Section 10.7.1.3 for further explanation of the value order.
Required if Distance Object to Table Top (0018,9403) is not empty.
Note
This value is provided besides the values that are the input parameters of the calibration algorithm.
Note
Part of the X-Ray Projection Pixel Calibration Functional Group Macro with usage: C
Required if C-arm Positioner Tabletop Relationship (0018,9474) is present and equals YES.
Section C.8.19.6.9.2
C.8.19.6.9.2 Object Pixel Spacing in Center of Beam
The value provided for Beam Angle (0018,9449) shall correspond to the other Attribute values within this Module and according to the mathematic terms listed in Section C.8.19.6.9.1.
The terms listed will result in infinite result when used with 90-degree beam angles.
It is outside the scope of this Standard to define reasonable limits for single input values in the above-mentioned terms, or to define the mathematical accuracy of applications using those terms.
Note
It may be reasonable to limit automatic calculations to a narrow range of +/- 60 degrees for Beam Angle and inform users about possible deviations in the calibration result when exceeding such range limits.
Section 10.7.1.3
10.7.1.3 Pixel Spacing Value Order and Valid Values
All pixel spacing related Attributes are encoded as the physical distance between the centers of each two-dimensional pixel, specified by two numeric values.
The first value is the row spacing in mm, that is the spacing between the centers of adjacent rows, or vertical spacing.
The second value is the column spacing in mm, that is the spacing between the centers of adjacent columns, or horizontal spacing.
To illustrate, consider the example shown in Figure 10.7.1.3-1.
Figure 10.7.1.3-1. Example of Pixel Spacing Value Order
Pixel Spacing = Row Spacing \ Column Spacing = 0.30\0.25.
All pixel spacing related Attributes shall have positive non-zero values, except when there is only a single row or column or pixel of data present, in which case the corresponding value may be zero.
Note
A single row or column or "pixel" may occur in MR Spectroscopy Instances.
This description applies to:
-
Pixel Spacing (0028,0030)
-
Imager Pixel Spacing (0018,1164)
-
Nominal Scanned Pixel Spacing (0018,2010)
-
Image Plane Pixel Spacing (3002,0011)
-
Compensator Pixel Spacing (300A,00E9)
-
Detector Element Spacing (0018,7022)
-
Presentation Pixel Spacing (0070,0101)
-
Printer Pixel Spacing (2010,0376)
-
Object Pixel Spacing in Center of Beam (0018,9404)