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CAR '97 DICOM Demonstration CD


The Image Validation Process
 



Image Sources


The images found on this CAR'97 DICOM Demonstration CD have not been modified by OFFIS in any way. Most of the images supplied by the participating vendors have been obtained from actual products and have not been manually edited to make them cleaner.

The images have been evaluated by a variety of validation and testing tools. OFFIS used its DCMCHECK image validation and testing package and the participating vendors used their own validation tools.

 


Known Image Problems


Some known problems remain with the images on the CAR'97 DICOM Demonstration CD and these are documented below. Many of the problems encountered result from differences in interpretation, lack of clarity or inconsistencies. One of the side-effects of the production of this CD will be to propose a number of Correction Proposals to clarify and correct these issues. It should be stressed that the remaining problems are minor in nature and should not affect image display. We recommend that DICOM implementations be as lenient as possible when reading and as strict as possible when writing.
 


Attribute value out of range


The value of an attribute is outside a specified or reasonable range.
  • The attribute Series Number (0020,1011) uses the Value Representation IS (Integer String) which can contain an integer in the range -(231 - 1) <= n <= (231 - 1).
    Images Affected: All Philips SC Images
    DICOM\PHILIPS\INTEGRIS\*

  • The attribute Pixel Spacing (0028,0030) describes the physical distance in the patient between the center of each pixel. A value of zero makes no sense in this context.
    Images Affected:
    DICOM\PHILIPS\THORA3_3\CASE_*
    DICOM\SIEMENS\PAT*DS\*\*

 


Missing conditional attributes


Conditional attributes (Type 1C and 2C) must be present in the image if the associated condition is met.
  • The attribute Rescale Type (0028,1054) from the Modality LUT Module is of type 1C and has the condition Required Rescale Intercept is Present (Correction Proposal 15).
    Images Affected: All Siemens Images
    DICOM\SIEMENS\*\*

 


Conditional attributes which should not be present


Currently, DICOM forbids the presence of conditional attributes (Type 1C and 2C) if the defined condition is not met. This problem has illustrated a possible conflict in DICOM between the concept of a Standard Extended SOP Class (where additional attributes have been added to an images) and the rules for conditional attributes (cf. DICOM Part 5, 7.4.4). This issue will require clarification in a Correction Proposal.
  • The attribute Inversion Time (0018,0082) from the MR Image Module is of type 2C and has the condition Required if Scanning Sequence (0018,0020) has values of IR. However, if the attribute Scanning Sequence (0018,0020) does not have a value of IR then attribute Inversion Time (0018,0082) should not be present in the images.
    Images Affected: All GE MR Images
    DICOM\GE\PA1\*\*
    DICOM\GE\PA11\*\*
    DICOM\GE\PA7\*\*
    DICOM\GE\PA8\*\*

  • The attribute Patient Orientation (0020,0020) from the General Image Module is of type 2C and has the condition Required if image does not require Image Orientation (0020,0037) and Image Position (0020,0032). However, if the image does require the attributes Image Orientation (0020,0037) and Image Position (0020,0032) then attribute Patient Orientation (0020,0020) should not be present in the images.
    Images Affected: All Philips CT Images
    DICOM\PHILIPS\CT_SR\*

 


Empty Defined Terms in Multi-Valued Attributes


A required attribute (Type 1) which is specificed to contain one of an extendable set of defined terms (constant values) contains an empty value for one of its components. It is unclear if an empty string is a valid defined term and if all components of a Type 1 attribute be present. This issue will require clarification in a Correction Proposal.
  • The attribute (0008,0008) Image Type uses an empty value for its third component
    Images Affected: All GE MR Images
    DICOM\GE\PA1\*\*
    DICOM\GE\PA11\*\*
    DICOM\GE\PA7\*\*
    DICOM\GE\PA8\*\*

 


Inconsistant Attribute Values


Attributes which are expected to be the same are different.
  • Images with the same Patient ID use different Patient Names.
    Images Affected:
    DICOM\PHILIPS\THORA3_3\*
    DICOM\PHILIPS\CT_SR\KNE
    DICOM\PHILIPS\CT_SR\VOLSCANS\KNE\*
    DICOM\PHILIPS\DSI4_2_1\*

  • Images from the same Study have different Study Dates.
    Images Affected:
    DICOM\SIEMENS\PAT9MR\P9ST1S1\*
    DICOM\SIEMENS\PATAMR\P10ST1S1\*

  • Images from the same Study have different Study Times.
    Images Affected:
    DICOM\PHILIPS\CT_SR\*
    DICOM\PHILIPS\CT_SR\VOLSCANS\*
    DICOM\SIEMENS\PAT9MR\P9ST1S1\*
    DICOM\SIEMENS\PATAMR\P10ST1S1\*

  • Images from the same Series have different Series Numbers.
    Images Affected:
    DICOM\SIEMENS\PAT1DS\P1ST1S1\*
    DICOM\SIEMENS\PAT2DS\P2ST1S1\*

 


Known DICOMDIR Problems


A second type of problem results from the process of building the DICOMDIR file (Medical Directory) which contains summary information and references to all the images on the CD.
 


Unknown values for required DICOMDIR attributes


When constructing a DICOMDIR from a set of image files it is possible for required attributes (Type 1) in the DICOMDIR to be unknown. This is not a violation of DICOM but rather an issue which applications writing DICOM media must face. The required information might not have been available at the time when the image was created by a modality (e.g. the patient's identity was unknown). For the purposes of this CD, while constructing the DICOMDIR, we have chosen to introduce dummy values whenever necessary (e.g. DCMTKPAT000001 for a missing Patient ID). More sophisticated software would obtain the required information from other sources (e.g. via manual operator intervention or automatically via a RIS interface).
  • The attribute Patient ID (0010,0020) from the Patient Module is type 2 for images but type 1 in a DICOMDIR.
    Images Affected:
    DICOM\PHILIPS\INTEGRIS\*

  • The attribute Study ID (0020,0010) from the General Study Module is type 2 for images but type 1 in a DICOMDIR.
    Images Affected:
    DICOM\GE\PA10\ST2\SE1\*
    DICOM\PHILIPS\DSI4_2_1\*

  • The attribute Study Time (0008,0030) from the General Study Module is type 2 for images but type 1 in a DICOMDIR.
    Images Affected:
    DICOM\GE\PA10\ST2\SE1\*

 
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