The slides were presented on 2015 KSMP, Spring

1. New Quality Assurance Method
Using Motion Tracking for 6D
Robotic Couches
Wonjoong Cheon1, Junsang Cho2, Sungwhan Ahn2,
Youngyih Han*2 , Dohoo Choi2
`
1. Department of Health Sciences and Technology, Sungkyunkwan University
2. Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of
Medicine

2. CONTENTS
[1] Introduction
[2] Material and Method
[3] 6DoF Robotic couch QA Program
[4] QA report
[5] Result and Conclusion

3. Fig 3.stereotactic
radiosurgery (SRS)
Fig 4. Proton Therapy
Introduction
High accuracy radiotherapy
Fig 1. Intensity modulated
radiation therapy (IMRT)
Fig 2. Volumetric modulated
arc therapy (VMAT)

4. Introduction
6DoF robotic couch
+y

5. Geometry calibration
between different coordinate
systems
Motion capture camera
- Visual Tracking System (VTS)
Concept of 6DoF robotic couch QA Program

6. Visual Tracking System (VTS)

7. Visual Tracking System
(Bonita10, Vicon, UK).
NAME OF FACILITY
Bonita B10 Camera (Infrared camera)
RANGE
1000~8000 [mm]
FRAME RATE
~250 [frame per second]
RESOLUTION
1024 x 1024 [pixel]
CAM LATENCY
2.0 [ms]
MAXIMUM SHUTTER TIME
0.5 [ms]
ACCURACY OF TRACKING
Sub-millimeter (20mm, 4sec)
Fig 6. Avatar, the movie, was made
using Visual Tracking System
Fig 8. NEXUS,
the Program provided
from Vicon
Fig 7. Visual Tracking System
(Bonita10, Vicon, UK)

8. Geometry calibration
between different coordinate
systems
Motion capture camera
- Visual Tracking System (VTS)
Concept of 6DoF robotic couch QA Program

9. Geometry calibration
Coordinates from VTS is transferred
to Room coordinate system.

10. Fig 9. The concept of geometry calibration between different coordinate systems
Concept: Different perspectives

11. Coordinate matching
Fig 10. 6DoF robotic couch which was
installed in Proton therapy Center,
Samsung medical Center
Fig 11. the coordinates system
of 6DoF robotic couch
Fig 13. the coordinates system of Visual
Tracking System
(Bonita B10, Vicon, UK)
Fig 12. Visual Tracking System
(Bonita10, Vicon, UK)
y-
z-
x+ y+
z-
x+

12. Fig 14. QUASAR cube phantom
QUASAR cube phantom
(MODUS medical device, London, Canada).
NAME OF FACILITY
QUASAR cube phantom
SPECIFICATION
5.7 X 5.7 X 5.7 [mm]

13. Fig 16. Cube phantom on Nexus, VTS viewer.
Fig 17. QUASAR cube phantom
Coordinate matching
VTS View
Fig 15. Experiment environment

14. Fig 18. QUASAR cube phantom.
Fig 19. Cube phantom was set on the 6DoF
robotic couch.
Fig 20. Cube phantom was set on the 6DoF
robotic couch along the laser.
Coordinate matching
6DoF robotic couch
x+
x+

15. 𝑹 =
𝑹 𝟏 𝑹 𝟐 𝑹 𝟑 𝑹 𝟒
𝟏 𝟏 𝟏 𝟏
𝑹 𝟓 𝑹 𝟔 𝑹 𝟕 𝑹 𝟖
𝟏 𝟏 𝟏 𝟏
𝑽 =
𝑽 𝟏 𝑽 𝟐 𝑽 𝟑 𝑽 𝟒
𝟏 𝟏 𝟏 𝟏
𝑽 𝟓 𝑽 𝟔 𝑽 𝟕 𝑽 𝟖
𝟏 𝟏 𝟏 𝟏
𝑹 = 𝑻 𝑽𝑹 ∙ 𝑽
𝑻 𝑽𝑹 = 𝑹 ∙ 𝑽−𝟏
𝑵𝒆𝒘_𝑪𝒐𝒐𝒓𝒊𝒅𝒊𝒏𝒂𝒕𝒆𝒔_𝑹𝒐𝒐𝒎𝑪𝒐𝒐𝒓𝒅𝒊𝑺𝒚𝒔𝒕𝒆𝒎
= 𝑻𝑽𝑹 ∙ 𝑵𝒆𝒘_𝑪𝒐𝒐𝒓𝒊𝒅𝒊𝒏𝒂𝒕𝒆𝒔_𝑽𝑻𝑺𝑪𝒐𝒐𝒓𝒅𝒊𝑺𝒚𝒔𝒕𝒆𝒎
V1(i1, j1, k1)
V2(i2, j2, k2)
V3(i3, j3, k3)
V4(i4, j4, k4)
V6(i6, j6, k6)
V7(i7, j7, k7)
V8(i8, j8, k8)
Room Coordinate system
R1(x1, y1, z1) R2(x2, y2, z2)
R3(x3, y3, z3)
R4(x4, y4, z4)
R5(x5, y5, z5) R6(x6, y6, z6)
R7(x7, y7, z7)
R8(x8, y8, z8)
V5(i5, j5, k5)
Geometry calibration method
VTS Coordinate system

16. Room = TVR * VTS
Procedure of Geometry calibration

17. 6DoF Robotic couch
QA
Program

18. Magnitude Base :
Linear position & Rotation angle

19. Geometry calibration Base:
Linear position + Sag

20. QA report

21. Magnitude Base :
Linear position
+y
+z
+x
MOTION TYPE
Linear position
RANGE OF MOTION
From initial position to 250 [mm]
STEP-SIZE
25 [mm]
DIRECTION OF MOTION
X
Table 1. the result of linear position accuracy QA

22. +y
+z
+x
MOTION TYPE
Couch Top Rotation
RANGE OF MOTION
From initial position to +90 [degree]
STEP-SIZE
10 [degree]
Magnitude Base :
Rotation angle
Table 2. the result of rotation accuracy QA

23. +y
+z
+x
Geometry calibration Base:
Linear position + Sag
MOTION TYPE
Linear position
RANGE OF MOTION
From initial position to 10 [mm]
STEP-SIZE
1 [mm]
DIRECTION OF MOTION
X, Y, and Z
Table 3. the result of linear position accuracy and sagging QA

24. Result & Conclusion
- RESULT & CONCLUSION
VTS system could track couch motion accurately and measured position in room-
coordinates. The VTS measurements and Laser tracker data agreed within 1% of difference
for linear and rotational motions. Also because the program analyzes motion in 3-Dimension,
it can compute couch sagging.
Developed QA system provides sub-millimeter/degree accuracy which fulfills the high-end
couch QA.
-ACKNOWLEDGEMENT
This work was supported by the National Research Foundation of Korea funded by Ministry
of Science, ICT & Future Planning. (2013M2A2A7043507 and 2012M3A9B6055201).