DICOM WG-02
Advances in X-Ray Angiography
Projection Imaging and 3D
SPIE Medical Imaging
2009, Orlando
Authors:
Tim Becker
Heinz Blendinger
Bas Revet
Francisco Sureda
Rainer Thieme
European Society of Cardiology
Siemens Healthcare
Philips Healthcare
GE Healthcare (Speaker)
Siemens Medical Solutions (Chair DICOM WG-02)
1
Presentation Outline
Introduction
Present and future of X-Ray Angiography in DICOM
2D Projection Images & Presentation
Application Cases of the Enhanced XA SOP Class
XA 2D Grayscale Softcopy Presentation State
3D Reconstruction from Projections & Presentation
X-Ray 3D SOP Class
N-Dimensional Grayscale Softcopy Presentation State
Conclusion
2
Overview of X-Ray Angiography in DICOM
Approved in the
Standard
X-Ray Acquisition
2D Projection Images
3D Reconstruction
Supp 94:
Radiation Dose
Reporting
Supp 83:
Enhanced
XA/XRF
Supp 116:
X-Ray 3D
Storage
Work in
Progress
Follow-up of PAS by
IEC MT38 – 62B
Follow-up of IHE
REM Profile
Supp 139-PC:
Enhanced XA
Informative Annex
Supp 140-PC:
Presentation State
Multi-Dimensional
Presentation State
3
Workflow 2D X-Ray Angiography
SOP
CLASS
X-Ray
Acquisition
Procedure
X-Ray 2D
Projection
SOP Class
2D Presentation
State SOP Class
SOP
CLASS
Presentation
Procedure
Visualization
X-Ray Acquisition
System
Visualization
2D Visualization
System
4
Enhanced XA: 2D projection images
Supplement 83 – Standard 2004
– 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
What can be done with this new SOP Class?
– Supplement 139 (Part 17 – Informative) – Public Comments
passed
• Describes use cases where the Enhanced XA provides better
solutions
• Provides encoding guidelines for implementors, both creators
and users of the Enhanced XA SOP Class
5
Enhanced XA: Supplement 139
X-Ray 2D
Projection
X-Ray Acquisition
Modality
Enhanced XA
SOP CLASS
Applications
– General Definitions:
• Time relationships, Acquisition Geometry, Pixel Size calibration
– Application Use Cases
• Acquisition: Waveform synch, Mechanical Movement, X-Ray controls…
• Image Registration: 3D structures projected on 2D images
• Display: Standard pipeline, multi-mask subtraction, per-frame pixel shift
• Review: Variable review settings per group of frames
• Processing: Projection pixel calibration
6
Enhanced XA – Time Relationships
Content Date
(0008,0023)
Content Time
(0008,0033)
Frame “i”
Acquisition
Datetime
Frame “1”
Acquisition
Datetime
(0018,9074)
Acquisition
Datetime
(0008,002A)
Frame “1”
Reference
Datetime
(0018,9151)
Frame “N”
Reference
Datetime
Frame “i”
Reference
Datetime
…
…
FRAME 1
Frame “N”
Acquisition
Datetime
time
FRAME i
Frame “1”
Acquisition
Duration
(0018,9220)
FRAME N
Frame “N”
Acquisition
Duration
Acquisition Duration (calculated)
If Acquisition is synchronized with
external time reference then
Acquisition Time Synchronized
(0018,1800) = YES
Exposure Time (0018,9328) = SUMi( Frame “i” Acquisition Duration )
Average Pulse Width (0018,1154) = SUMi(Frame “i” Acquisition Duration) / N
7
Enhanced XA – Time Relationships (one frame)
Frame
Reference
Datetime
(0018,9151)
Frame
Acquisition
Datetime
(0018,9074)
X-ray FRAME “i”
Frame Acquisition Number (0020,9156) = “i”
PRE-FRAME
X-ray
time
Detector Activation
Offset from Exposure
(0018,7016)
Frame Acquisition Duration (0018,9220)
R
Detector Active Time (0018,7014)
Cardiac Trigger Delay Time (0020,9153)
Last R-peak prior to the X-ray
FRAME “i”
T
Q
S
NOTE: Positioner angle values, table position values etc… are measured at
the Frame Reference Datetime
8
Enhanced XA – Acquisition Techniques
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 »
= ti
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
current
mA1
mA2
mA3
Average
mA
mA5
mA4
Frame
#1
Frame
#2
Frame
#3
Frame
#4
Frame
#5
time
t1 (ms)
t2 (ms)
t3 (ms)
t4 (ms)
t5 (ms)
9
Enhanced XA – Acquisition Geometry
System set up
Image Transformation
X-Ray
Acquisition
PATIENT
position
on the
Table
TABLE
movement
Patient
Position
Description
POSITIONER
movement
X-Ray
Table
Description
Pixel Data
Storage
Detector
Binning
Detector
Description
X-Ray
Positioner
Description
 X-Ray Isocenter Reference System Macro
 X-Ray Geometry Macro
FOV
Rotation
& Horiz
Flip




FOV
Description
X-Ray Field of View Macro
XA/XRF Acquisition Module
X-Ray Detector Module
Image Pixel Module
10
Enhanced XA – 3D/2D Registration
Acquisition #1
Acquisition #2
+Z
O
+X
+Y
+Z
O
+X
+Y
Table
Movement
+X
+Z
O
+Y
Positioner
Movement
SID, ISO, FOV
change
+X
+Z
+Zp
O
+Xp
+Y
+X
+Z
+Yp
O
+Y
P1 (x,y,z)
P1t (xt,yt,zt)
P2 (x,y,z)
P2p (xp,yp,zp)
P2(i,j)
fa(P1, Table1)
fb(P1t, Table2)
fc(P2, Positioner2)
fd(P2, SID, ISO, FOV)
11
Enhanced XA – Standard Display Pipeline
X
Modality
LUT
Stored
Values
Shape = “IDENTITY” if (0028,0004) = MONOCHROME2
Shape = “INVERSE” if (0028,0004) = MONOCHROME1
VOI LUT
Pixel Intensity
Relationship LUT
1 to N
Pixel Intensity Relationship
LUT Sequence (0028,9422)
Pixel Intensity
Relationship LUT
Pixel Intensity Relationship
LUT Sequence (0028,9422)
P LUT
Pixel values transformed for
specific application
(if TO_LINEAR, then pixel values
proportional to the X-ray beam
intensity)
Display
Application
“TO_LINEAR” is required if Pixel Intensity
Relationship (0028,1040) = LOG
Pixel values transformed for
specific application
Application
12
Enhanced XA – Variable Review Settings
FRAME ACQUISITION:
1
2
3
4
5
Acq. Frame rate: 4.0
Purpose: X-Ray control
6
7
8
9
10 11 12 13
Acq. Frame rate: 15.0
Purpose: Contrast Media
14 15 16 17 18 19
Acq. Frame rate: 8.0
Purpose: Contrast Media
Frame Display Sequence (0018,7022)
DICOM ENCODING:
XA/XRF Multi-frame
Presentation
Module
Item 1
>Start Trim (0008,2142)
>Stop Trim (0008,2143)
>Skip Frame Range Flag (0008,9460)
>Recom. Display Frame Rate (0008,9459)
=1
=5
= SKIP
= 4.0
Item 2
>Start Trim (0008,2142)
>Stop Trim (0008,2143)
>Skip Frame Range Flag (0008,9460)
> Recom. Display Frame Rate (0008,9459)
=6
= 13
= DISPLAY
= 15.0
Item 3
>Start Trim (0008,2142)
>Stop Trim (0008,2143)
>Skip Frame Range Flag (0008,9460)
> Recom. Display Frame Rate (0008,9459)
= 14
= 19
= DISPLAY
= 8.0
13
Enhanced XA – Pixel Shift per frame
FRAME ACQUISITION
and PROCESSING:
Frames
#1
#2
#3
Right
Leg
Left
Leg
Sub ID
101
Sub ID
100
DICOM ENCODING:
Mask Module
Mask Subtraction Sequence (0028,6100)
Item 1
>Mask Operation (0028,6101)
>Subtraction Item ID (0028,9416)
>Applicable Frame Range (0028,6102)
>Mask Frame Numbers (0028,6110)
>Mask Operation Expl. (0028,6190)
= AVG_SUB
= 100
= 2\3
=1
= Left leg
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)
= AVG_SUB
= 101
= 2\3
=1
= Right leg
14
Enhanced XA – Pixel Shift per frame
FRAME ACQUISITION
and PROCESSING:
Frames
DICOM ENCODING:
Frame Pixel Shift per frame
Item 2
>Frame Pixel Shift Seq (0028,9415)
Frame #2
#1
#2
Item 3
>Frame Pixel Shift Seq (0028,9415)
Frame #3
#3
15
Enhanced XA – Pixel Shift per frame
FRAME ACQUISITION
and PROCESSING:
Frames
Left
Leg
#1
mask
#2
Pixel Shift
0.0 \ 8.0
#3
Pixel Shift
2.0 \ 10.0
DICOM ENCODING:
Frame Pixel Shift per frame
Item 2
>Frame Pixel Shift Seq (0028,9415)
Item 1
>>Subtraction Item ID (0028,9416)
>>Mask Sub-pix Shift (0028,6114)
Item 3
>Frame Pixel Shift Seq (0028,9415)
Item 1
>>Subtraction Item ID (0028,9416)
>>Mask Sub-pix Shift (0028,6114)
Frame #2
= 100
= 0.0\8.0
Frame #3
= 100
= 2.0\10.0
16
Enhanced XA – Pixel Shift per frame
FRAME ACQUISITION
and PROCESSING:
Frames
#1
#2
#3
Right
Leg
Left
Leg
mask
mask
Pixel Shift Pixel Shift
0.0 \ 0.0
0.0 \ 8.0
Pixel Shift Pixel Shift
0.0 \ -7.0 2.0 \ 10.0
DICOM ENCODING:
Frame Pixel Shift per frame
Item 2
>Frame Pixel Shift Seq (0028,9415)
Frame #2
Item 1
>>Subtraction Item ID (0028,9416)
>>Mask Sub-pix Shift (0028,6114)
= 100
= 0.0\8.0
Item 2
>>Subtraction Item ID (0028,9416)
>>Mask Sub-pix Shift (0028,6114)
= 101
= 0.0\0.0
Item 3
>Frame Pixel Shift Seq (0028,9415)
Item 1
>>Subtraction Item ID (0028,9416)
>>Mask Sub-pix Shift (0028,6114)
= 100
= 2.0\10.0
Item 2
>>Subtraction Item ID (0028,9416)
>>Mask Sub-pix Shift (0028,6114)
= 101
= 0.0\-7.0
Frame #3
17
Enhanced XA - Projection Pixel Size Calibration
How to convert from “image pixels” to “object mm in patient”
#Px = Object size in “image” pixels
D
= Object size in mm
TH = Table Height
TO = Dist. Table to Object
Beam Angle
SID = Dist. Source-Detector
ISO = Dist. Source-ISO
Px = Imager Pixel Spacing
#Px
Isocenter
Beam
Angle
SID
D
(0018,1130)
(0018,9403)
(0018,9449)
(0018,1110)
(0018,9402)
(0018,1164)
ISO
TH
TO
Table
D = # Px *  Px * SOD / SID
SOD = ISO - (TH- TO) / cos°(Beam Angle)
X-Ray
Source
18
XA/XRF Projection
Presentation State
19
Supplement 140: new XA GSPS IOD (for 2D)
Information that may be used to present angiographic
projection images
It includes capabilities from the Grayscale Softcopy
Presentation IOD for specifying:
a. the output grayscale space in P-Values
b. grayscale contrast transformations including VOI LUT
c. selection of the area of the image to display , rotate, flip
d. image and display relative annotations, graphics, text and overlays
20
Supplement 140: new XA GSPS IOD (for 2D)
Specific capabilities are provided for the presentation
of angiographic projection images:
a. shutter specifications on a frame-by-frame base,
b. mask subtraction including regional pixel shift
c. presentation of sets of frames
Similar to the XA/XRF Multi-Frame Presentation Module
of the Enhanced XA/XRF
21
XA Grayscale Softcopy Presentation State
Grayscale Contrast Transformations
The sequence of transformations from stored pixel values into P-Values
is explicitly defined in a conceptual model
Shutter per frame
The shutter coordinates per-frame may be modified in post-review
Frame #1
Frame #2
Frame #3
Frame #4
Frame #5
22
XA Grayscale Softcopy Presentation State
 mask subtraction & regional pixel shift
If Pixel Intensity
Relationship is not LOG
Else
« TO_LOG »
LUT
SUB
VOI LUT
…
Contrast Frame(s)
Else
Pixel Shift
&
Anatomic Background
Visibility
If Pixel Intensity
Relationship is not LOG
« TO_LOG »
LUT
Mask Frame(s)
23
XA Grayscale Softcopy Presentation State
 Regional pixel shift
Applicable pixel shift in case of multiple pixel shift regions
24
Sup 140 – Example of Regional Pixel Shift
Mask frame: non-injected structures (bones,
soft-tissues…)
25
Sup 140 – Example of Regional Pixel Shift
Contrast frame: injected vessels – background
structures moved since the mask acquisition
26
Sup 140 – Example of Regional Pixel Shift
Subtraction without pixel shift: background
structures are visible
27
Sup 140 – Example of Regional Pixel Shift
Regional Pixel Shift: Select region 1
28
Sup 140 – Example of Regional Pixel Shift
Mask Pixel
Shift (Column)
Mask Pixel
Shift (Row)
Regional Pixel Shift: Apply shift to mask on region 1
29
Sup 140 – Example of Regional Pixel Shift
Mask Pixel
Shift (Column)
Mask Pixel
Shift (Row)
30
Sup 140 – Example of Regional Pixel Shift
Mask Pixel
Shift (Column)
Mask Pixel
Shift (Row)
31
Sup 140 – Example of Regional Pixel Shift
Mask Pixel
Shift (Column)
Mask Pixel
Shift (Row)
… until background structures are not visible anymore
32
Sup 140 – Example of Regional Pixel Shift
Regional Pixel Shift: Select region 2
33
Sup 140 – Example of Regional Pixel Shift
Mask Pixel
Shift (Column)
Regional Pixel Shift: Apply shift to mask on region 2
34
Sup 140 – Example of Regional Pixel Shift
Regional Pixel Shift: Select region 3
35
Sup 140 – Example of Regional Pixel Shift
Mask Pixel
Shift (Column)
Regional Pixel Shift: Apply shift to mask on region 3
36
Sup 140 – Example of Regional Pixel Shift
Subtraction with regional pixel shift: background
structures are not visible anymore
37
3D X-Ray Angiography
38
Workflow 3D X-Ray Angiography
X-Ray
Acquisition
Procedure
X-Ray 2D
Projection
SOP Class
SOP
CLASS
Reconstruction
Procedure
3D Storage
SOP Class
SOP
CLASS
In progress
3D Presentation
State SOP Class
X-Ray
Calibration
Procedure
Presentation
Procedure
Calibration
Data
Proprietary
Visualization
X-Ray Acquisition
System
3D Reconstruction
System
Visualization
3D Visualization
System
39
X-Ray 3D Angiography
Supplement 116 – In standard 2007
–
–
–
–
New SOP Class for Multi-frame X-Ray 3D from projections
Re-use of encoding mechanisms of Enhanced CT and MR
Re-use volumic descriptions of Enhanced CT and MR
Additional information of the reconstruction from projections
What can be done with this new SOP Class?
–
–
–
–
–
Basic 3D visualization (slices)
References to 2D projections
Description of the reconstruction application
Relationship to the Equipment Coordinate System
...
40
X-Ray 3D Angiography – Rotational Acquisition
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
Optimized 3D
Reconstruction
Frame #2:
X-ray settings 2
Geometry settings 2
Frame #1:
X-ray settings 1
Geometry settings 1
41
X-Ray 3D Angiography – Reference to 2D
2D Projection SOP Instance «A»
Mask
M1...
Contrast
...M2
Reconstruction
1
C1...
...C2
Reconstruction
2
Contributing Sources
Sequence (0018,9506)
Source #1: Contrib. SOP Inst = SOP Inst “A”
SOP Instance description
X-Ray 3D Acquisition
Sequence (0018,9507)
Acq #1: Source Img Seq
= A: M1 to M2
Acq #2: Source Img Seq
= A: C1 to C2
Acquisition description
X-Ray 3D Reconstruction
Sequence (0018,9530)
Mask
1...
SUB
...N
N+1...
X-Ray 3D SOP Instance
...N+k
Recon #1: Acquisition Index
Recon #2: Acquisition Index
Reconstruction description
Per-Frame Func Groups
Sequence (5200,9230)
Frames #1 to #N: Recon Index
=1
= 1\2
=1
Frames #N+1 to #N+k: Recon Index = 2
Frame description
42
X-Ray 3D Angiography - Relationship to Equipment
Image to Equipment Matrix (0028,9520)
 A x   M 11
A  
 y    M 21
 A z   M 31
  
 1   0
M 12
M 22
M 32
0
M 13 Tx   B x 
 
M 23 Ty   B y 
M 33 Tz   B z 
  
0
1   1 
Patient Oriented
Coordinate System of
the 3D slices
Equipment
Coordinate System of
the 2D projections
P (Ax, Ay, Az)
P (Bx, By, Bz)
H
+X
+Z
R
O
+Y
L
F
Enhanced XA:
Isocenter Reference System
43
X-Ray 3D Angiography
Presentation State
44
X-Ray 3D Angiography – Presentation State
Needs for 3D Angiography Presentation
– Presentation features common to all 3D
– Speficic presentation of X-Ray 3D Angiography:
• Acquisition 3D shutter for collimation
• Volume Subtraction and voxel shift
• Stabilized point in all volumes (e.g. cardiac wall motion, stent stabilized)
• Catheter tracking trajectory in one volume
• 2D-3D blending presentation (3D conic projection on 2D fluoroscopy)
N-Dimensional Presentation State
• Work Item 2008-04-C. Addresses needs of multi-modalities
• Led by Working Group 11, participation of Web3D and other working groups
• Supplement in progress...
45
Conclusion
Supplement 139 – Enhanced XA application cases
In Public Comments. Informative (DICOM Part 17)
Will facilitate the adoption of the Enhanced XA (Sup 83)
Supplement 140 – XA/XRF Presentation State
In Public Comments. Enables:
shutter on a frame-by-frame base,
mask subtraction including regional pixel shift
presentation of set of frames
X-Ray 3D Angiography
New IOD approved in Standard 2007 (Sup 116)
3D Presentation State on-going...
Contact WG-02 chairman:
francisco.sureda@med.ge.com
46