DICOM PS3.3 2018c - Information Object Definitions

10.7 Basic Pixel Spacing Calibration Macro

Table 10-10 defines the Attributes for the Basic Pixel Spacing Calibration Macro.

Table 10-10. Basic Pixel Spacing Calibration Macro Attributes

Attribute Name

Tag

Type

Attribute Description

Pixel Spacing

(0028,0030)

1C

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.

Pixel Spacing Calibration Type

(0028,0A02)

3

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.

Pixel Spacing Calibration Description

(0028,0A04)

1C

A free text description of the type of correction or calibration performed.

Note

  1. In the case of correction, the text might include description of the assumptions made about the body part and geometry and depth within the Patient.

  2. in the case of calibration, the text might include a description of the fiducial and where it is located (e.g., "XYZ device applied to the skin over the greater trochanter").

  3. Though it is not required, the Device Module may be used to describe the specific characteristics and size of the calibration device.

Required if Pixel Spacing Calibration Type (0028,0A02) is present.


10.7.1 Basic Pixel Spacing Calibration Macro Attribute Descriptions

10.7.1.1 Pixel Spacing

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.

Note

  1. Imager Pixel Spacing (0018,1164) is a required Attribute in DX family IODs.

  2. Nominal Scanned Pixel Spacing (0018,2010) is a required Attribute in Multi-frame SC family IODs

10.7.1.2 Pixel Spacing Calibration Type

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

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

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.

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.

Example of Pixel Spacing Value Order

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)

DICOM PS3.3 2018c - Information Object Definitions