Sort-by Category Attribute
| Tag | (0072,0602) |
|---|---|
| Type | Conditionally Required (1C) |
| Keyword | SortByCategory |
| Value Multiplicity | 1 |
| Value Representation | Code String (CS) |
Category of the sorting operation. See Section C.23.3.1.2.
Defined Terms:
- ALONG_AXIS
-
for CT, MR, other cross-sectional image sets
- BY_ACQ_TIME
-
Required if Selector Attribute (0072,0026) is not present.
Section C.23.3.1.2
C.23.3.1.2 Sorting Operations Sequence
The Items in the Sorting Operations Sequence (0072,0600) define the order in which the images resulting from the filter and reformat operations on the Image Set are to be displayed in the associated Image Boxes of the Display Set. The sorting criteria may include the value of a numeric, date, or time Attribute that is expected to be present in each of the image objects in the filtered Image Set, and/or an abstract sorting category. A sorting direction shall be associated with each sorting criterion. If a textual Attribute is used for sorting, then the INCREASING sorting direction indicates alphabetical order, and DECREASING indicates reverse alphabetical order.
If a Code Sequence Attribute is used for sorting, then Code Meaning (0008,0104) shall be sorted alphabetically. If a string numeric Attribute is used for sorting (VR of IS or DS), then sorting shall be on the numeric value, and padding shall be ignored. When sorting by date or time Attribute, then sorting shall be on the temporal value, not the alphabetic string.
If there are multiple Items in the Sorting Operations Sequence (0072,0600), then the sorting operations shall be applied in Item order. The least rapidly varying Attribute for the sorting operation shall be the first Item in the Sequence.
Note
For example, a Sorting Operations Sequence (0072,0600) with two Items:
-
Item #1: (0018,5101) View Position, INCREASING
-
Item #2: (0008,0020) Study Date, INCREASING
results in the following order, based on these Attribute values in the image objects:
|
View Position (0018,5101) |
Study Date (0008,0020) |
|---|---|
|
AP |
20030201 |
|
AP |
20030501 |
|
LL |
20020705 |
|
LL |
20030102 |
|
RL |
20030101 |
|
RL |
20030201 |
When the Sort-by Category (0072,0602) is used with a value of ALONG_AXIS, such as for CT, MR or other cross-sectional image sets, the sorting operation is computed from the values Image Position (Patient) (0020,0032) and Image Orientation (Patient) (0020,0037) in the image objects.
For the image set to be displayed, a "dominant axis" of the set shall be determined. The dominant axis is the normal to Image Orientation (Patient) (0020,0037) (assuming all selected images are parallel), computed as the dot product in a right-handed coordinate system (see Section C.7.6.2.1.1). The INCREASING direction for ALONG_AXIS of the image set shall be in the positive direction along the dominant axis. The DECREASING direction shall be in the negative direction along that axis.
When the Sort-by Category (0072,0602) is used with a value of BY_ACQ_TIME, the sorting operation is computed from appropriate values in the image objects (e.g., Frame Acquisition DateTime, Acquisition Time, Content Time, Acquisition DateTime), since the specific Attribute used may vary from one Image Instance or SOP Class to another, yet the Hanging Protocol Instance may be generally applicable.
An application that is applying a Hanging Protocol Instance shall support any value for Selector Attribute (0072,0026), provided that it is present in the referenced Image Set. The Attributes of the Hanging Protocol Selector Attribute Context Macro specify whether Selector Attribute (0072,0026) is contained in a Sequence, Functional Group Sequence or Private Group.
Note
-
The following Attributes from image IODs are examples of some possible values for Selector Attribute (0072,0026) of Sorting Operations Sequence (0072,0600). This is not a complete list:
-
Acquisition DateTime (0008,002A)
-
Acquisition Time (0008,0032)
-
Echo Time (0018,0081)
-
Echo Number(s) (0018,0086)
-
Trigger Time (0018,1060)
-
View Position (0018,5101)
-
Effective Echo Time (0018,9082)
-
Acquisition Number (0020,0012)
-
Instance Number (0020,0013)
-
Slice Location (0020,1041), although Sort-by Category (0072,0602) with value ALONG_AXIS may be more reliable
-
Trigger Delay Time (0020,9153)
-
Stage Number (0008,2122)
-
View Number (0008,2128)
-
-
For a multi-frame image set, it is the responsibility of the application to apply the sorting operations to individual frames within a multi-frame Image Instance in the image set, versus multiple single-frame Image Instances in the image set that represent individual frames.