Table 10-10 specifies the Attributes of the Basic Pixel Spacing Calibration Macro.
Table 10-10. Basic Pixel Spacing Calibration Macro Attributes
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Physical distance in the Patient between the center of each pixel, specified by a numeric pair - adjacent row spacing (delimiter) adjacent column spacing in mm. See Section 10.7.1.1 and Section 10.7.1.3. Required if the image has been calibrated. May be present otherwise. |
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The type of correction for the effect of geometric magnification or calibration against an object of known size, if any. See Section 10.7.1.2. |
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A free text description of the type of correction or calibration performed. Note
Required if Pixel Spacing Calibration Type (0028,0A02) is present. |
Pixel Spacing (0028,0030) specifies the physical distance in the Patient between the center of each pixel.
If Pixel Spacing (0028,0030) is present and the image has not been calibrated to correct for the effect of geometric magnification, the values of this Attribute shall be the same as in Imager Pixel Spacing (0018,1164) or Nominal Scanned Pixel Spacing (0018,2010), if either of those Attributes are present.
If Pixel Spacing (0028,0030) is present and the values are different from those in Imager Pixel Spacing (0018,1164) or Nominal Scanned Pixel Spacing (0018,2010), then the image has been corrected for known or assumed geometric magnification or calibrated with respect to some object of known size at known depth within the Patient.
If Pixel Spacing Calibration Type (0028,0A02) and Imager Pixel Spacing (0018,1164) and Nominal Scanned Pixel Spacing (0018,2010) are absent, then it cannot be determined whether or not correction or calibration have been performed.
The Pixel Spacing Calibration Type (0028,0A02) Attribute specifies the type of correction for the effect of geometric magnification or calibration against an object of known size, if any.
Enumerated Values:
- GEOMETRY
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The Pixel Spacing (0028,0030) values account for assumed or known geometric magnification effects and correspond to some unspecified depth within the Patient; the Pixel Spacing (0028,0030) values may thus be used for measurements of objects located close to the central ray and at the same depth.
- FIDUCIAL
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The Pixel Spacing (0028,0030) values have been calibrated by the operator or image processing software by measurement of an object (fiducial) that is visible in the pixel data and is of known size and is located close to the central ray; the Pixel Spacing (0028,0030) values may thus be used for measurements of objects located close to the central ray and located at the same depth within the Patient as the fiducial.
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.
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. If the value is non-zero, its purpose may be to convey the dimensions of a single row or column or pixel, such as in single voxel MR Spectroscopy; there is no other mechanism for conveying this.