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Application cases using the Enhanced XA SOP Class

Explore the application cases and benefits of using the Enhanced XA SOP Class in X-Ray imaging, including cine review, pixel data display, and image subtraction. Learn about enhanced attributes and guidelines for implementers.

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Application cases using the Enhanced XA SOP Class

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  1. Application cases using the Enhanced XA SOP Class Tim Becker Heinz Blendinger Bas Revet Francisco Sureda Rainer Thieme European Society of Cardiology Siemens Healthcare Philips Medical Systems GE Healthcare Siemens Healthcare (Chair DICOM WG-02) Working Group 02 – Projection Radiography and Angiography

  2. Enhanced XA SOP Class • Defined in Supplement 83, in Standard 2006 • New SOP Class for Multi-frame X-Ray Projection Angiography • Re-use of encoding mechanisms of Enhanced CT and MR • Enhanced with new attributes to support new applications • Inter-operability is improved in multiple domains • New supplement in progress for DICOM Part 17 (informative): • Describes use cases where the Enhanced XA provides better solutions • Provides encoding guidelines for implementers, both creators and users of the Enhanced XA SOP Class

  3. X-Ray Acquisition Modality Applications Application Domains X-Ray 2D Projection • Examples of application domains that are improved by using the Enhanced XA SOP Class • Review: Variable review settings per groups of frames • Display: Standard pipeline, per-frame pixel shift • Processing, Measurements: Projection pixel calibration • Quality Control:X-Ray parameters per-frame • Acquisition: Mechanical Movement • Image Registration: 3D structures projected on 2D image Enhanced XA SOP CLASS

  4. Cine Review • Application case #1 • The acquisition settingsvary during the image acquisition. • The frames are grouped by common settings • Viewing applications need to know how to review the groups of frames based on their settings (e.g. frame rate, duration, subtraction, anatomical background degree…). • Solution with Enhanced XA • Allows to describe the review settings of each group of frames of the multi-frame image, in terms of: • whether or not the group shall be displayed. • frame rate and duration, • subtracted or not, and anatomical background degree, • edge enhancement filter percentage.

  5. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Acq. Frame rate: 15.0 Purpose: Contrast Media Acq. Frame rate: 8.0 Purpose: Contrast Media Acq. Frame rate: 4.0 Purpose: X-Ray control Item 1 >Start Trim (0008,2142) = 14 = 1 = 6 >Stop Trim (0008,2143) = 5 = 13 = 19 = SKIP = DISPLAY = DISPLAY >Skip Frame Range Flag (0008,9460) = 8.0 = 0.0 = 15.0 >Recom. Disp Frame Rate (0008,9459) Item 2 >Start Trim (0008,2142) >Stop Trim (0008,2143) >Skip Frame Range Flag (0008,9460) >Recom. Disp Frame Rate (0008,9459) Item 3 >Start Trim (0008,2142) >Stop Trim (0008,2143) >Skip Frame Range Flag (0008,9460) >Recom. Disp Frame Rate (0008,9459) Cine Review FRAME ACQUISITION Frame Display Sequence (0018,7022) DICOM ENCODING: XA/XRF Multi-frame Presentation Module

  6. Image Display and Processing • Application case #2 • Viewing applications need to display the pixel data consistently as in the acquisition system, by applying basic processing. • Post-processing applications need to know the relationship between the pixel data and the X-Ray, to optimize advanced image processing and quantitative measurements of density. • Solution with Enhanced XA • Allows to describe the standard display pipeline separately from the description of the relationship between pixel value and X-Ray intensity.

  7. Shape = “IDENTITY” if (0028,0004) = MONOCHROME2 Shape = “INVERSE” if (0028,0004) = MONOCHROME1 X Display VOI LUT P LUT Modality LUT Stored Values Pixel values transformed for specific application (if TO_LINEAR, then pixel values proportional to the X-ray beam intensity) Pixel Intensity Relationship LUT Application Pixel Intensity Relationship LUT Sequence (0028,9422) 1 to N “TO_LINEAR” is required if Pixel Intensity Relationship (0028,1040) = LOG Pixel values transformed for specific application Application Pixel Intensity Relationship LUT Pixel Intensity Relationship LUT Sequence (0028,9422) Image Display and Processing

  8. Complex Pixel Shift • Application case #3 • The image acquisition contains mask and contrast frames to be subtracted during the display. Two or more background organs have moved independently to each other between the mask and contrast acquisition. • The acquisition system has determined different pixel shift values to be applied to each organ. • Viewing applications need to know the various pixel shift values to be applied sequentially to the subtracted image. • Solution with Enhanced XA • Allows to describe several subtraction items, each one having an associated pixel shift value

  9. Item 1 >Mask Operation (0028,6101) = AVG_SUB = AVG_SUB >Subtraction Item ID (0028,9416) = 101 = 100 Left Leg Right Leg >Applicable Frame Range (0028,6102) = 2\3 = 2\3 = 1 = 1 >Mask Frame Numbers (0028,6110) = Right leg = Left leg >Mask Operation Expl. (0028,6190) Sub ID 100 Sub ID 101 Item 2 >Mask Operation (0028,6101) >Subtraction Item ID (0028,9416) >Applicable Frame Range (0028,6102) >Mask Frame Numbers (0028,6110) >Mask Operation Expl. (0028,6190) Complex Pixel Shift FRAME ACQUISITION and PROCESSING: DICOM ENCODING: Mask Module Frames Mask Subtraction Sequence (0028,6100) #1 #2 #3

  10. Left Leg Right Leg mask mask Item 1 = 101 = 101 = 100 = 100 >>Subtraction Item ID (0028,9416) = 1.0\9.0 = 0.0\8.0 = 0.0\0.0 = 1.0\2.0 >>Mask Sub-pix Shift (0028,6114) Pixel Shift 0.0 \ 0.0 Pixel Shift 0.0 \ 8.0 Item 2 >>Subtraction Item ID (0028,9416) >>Mask Sub-pix Shift (0028,6114) Pixel Shift 1.0 \ 2.0 Pixel Shift 1.0 \ 9.0 Item 1 >>Subtraction Item ID (0028,9416) >>Mask Sub-pix Shift (0028,6114) Item 2 >>Subtraction Item ID (0028,9416) >>Mask Sub-pix Shift (0028,6114) Complex Pixel Shift FRAME ACQUISITION and PROCESSING: DICOM ENCODING: Frame Pixel Shift Per-Frame Frames Item 2 Frame #2 >Frame Pixel Shift Seq (0028,9415) #1 #2 Item 3 Frame #3 #3 >Frame Pixel Shift Seq (0028,9415)

  11. Projection Pixel Size Calibration • Application case #4 • Post-processing applications need to know the pixel size in the patient, in order to measure the size of the objects projected on the image. • To optimize the workflow, it shall avoid theusage of external calibration objects such as catheter or ruler. • Solution with Enhanced XA • Allows to describe the conic projection geometry of the image acquisition, including: • the position of the table in the trajectory of the X-Ray beam, • the distance from the object in the patient to the table top plane.

  12. D D = # Px * Px * SOD / SID #Px SOD = ISO - (TH - TO) / cos°(Beam Angle) Isocenter Beam Angle SID ISO D TH TO Table X - R ay Source Projection Pixel Size Calibration How to convert from “pixels on image” to “mm in patient”: #Px = Object size in “image” pixels D = Object size in mm TH = Table Height (0018,1130) TO = Dist. Table to Object (0018,9403) Beam Angle (0018,9449) SID = Dist. Source-Detector (0018,1110) ISO = Dist. Source-ISO (0018,9402) DPx = Imager Pixel Spacing (0018,1164)

  13. Quality Control • Application case #5 • The image acquisition is performed with several settings and parameters varying during the acquisition. • The quality control applications need to determine the exact values of the X-Ray parameters for each frame, and to relate them to the X-Ray beam incidence on the frames. • Solution with Enhanced XA • Allows to describe the X-Ray acquisition parameters in a per-frame basis.

  14. Quality Control Values per frame are in the Per-frame Functional Groups Seq. (200,9230): In the Frame Content Sequence (0020,9111): • Frame Acquisition Duration (0018,9220) in ms of frame « i » = Dti In the Frame Acquisition Sequence (0018,9417): • KVP (0018,0060) of frame « i » = kVpi • X-Ray Tube Current in mA (0018,9330) of frame « i » = mAi

  15. Mechanical Movement • Application case #6 • One dynamic acquisition is performed with movement of the X-Ray positioner or the X-Ray table. • Orseveral static acquisitions are performed of the same organ or object of interest • Applications need to relate the projected objects to the 3D space for 3D reconstruction and/or 3D localization. • Solution with Enhanced XA • Allows to describe the Positioner and Table on an absolute reference (Isocenter) in addition to the patient reference. • Allows to describe the Detector Area and the Field of View transformations to relate each pixel to the fixed reference.

  16. Optimized 3D Reconstruction Rotational Movement Frame #5: X-ray settings 5 Geometry settings 5 Frame #4: X-ray settings 4 Geometry settings 4 Frame #3: X-ray settings 3 Geometry settings 3 Frame #2: X-ray settings 2 Geometry settings 2 Frame #1: X-ray settings 1 Geometry settings 1

  17. Table run #1 Table run #2 Positioner run #2 SID, ISO, FOV run #2 +Zp +Xp +Yp +X +X +X +Z +Z +Z O O O P1 (x,y,z) P1t (xt,yt,zt) fa(P1, Table1) P2 (x,y,z) fb(P1t, Table2) P2p (xp,yp,zp) fc(P2, Positioner2) P2(i,j) fd(P2, SID, ISO, FOV) +Y +Y +Y Image Registration

  18. Conclusion • The Enhanced XA SOP Class improves interoperability • It overcomes the known limitations of the current XA SOP Class and enables future applications • It is open for today’s and new applications and equipments • In DICOM Standard since 2006 • DICOM WG-02 currently prepares a new supplement for the Part 17 (Informative) • with practical scenarios on Enhanced XA usage

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