1. Digital image self-adaptive acquisition in medical x-ray imaging
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Bao Jie, Gao Jun et.al.
Lab on Image Information Processing
Hefei University of Technology , China
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

2. What is X-ray fluoroscopy system and digital acquisition system
Content
What is X-ray fluoroscopy system and digital acquisition system
The principle and implementation of self-adaptive digital acquisition
Experiment and Conclusions
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

3. 1. What is X-ray fluoroscopy system and digital acquisition system?
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

4. What’s X-ray fluoroscopy system?
X-ray fluoroscopy system is a system for medical diagnosing that can render image of the body of patient by convert X-ray which pass through and attenuated by the body into visible light and record it on film or other media. It’s a very common method for examination in hospitals.
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

5. Construction of X-ray fluoroscopy system
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

6. Why study the digital acquisition of X-ray fluoroscopy system?(1)
The digitalization of x-ray imaging is very important for PACS (Picture Archiving and Communication system); high-quality digital X-ray medical images are indispensable for PACS data source.
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

7. Why study the digital acquisition of X-ray fluoroscopy system?(2)
There are three ways to digitalize x-ray imaging
Computed Radiography (CR)
Digital Radiography (DR)
Video digital acquisition.
Advantages of video digital acquisition : ability to see dynamic change of organs, device simplicity, operating convenience, and low-cost
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

8. The main difficulties in video digital acquisition
x-ray fluoroscopy image detection noise and digital quantum noise
Adjusting imaging contrast and resolution
Device background signal
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

9. Improve hardware quality of x-ray imaging system
How to deal with them?
choose a appropriate working point automatically and suppressed background signal by software
Improve hardware quality of x-ray imaging system
Choose grabber board with high quantization precision
Voltage stabilization and electromagnetic shielding
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

10. Digital video processing system(1)
Enhancement
Annotation
Display
Diagnose
manual
x-ray video
Information
navigation
NSP
grabber board
Host
Report
Aided
diagnose
Aided
treat
ment
Control
Archiving and backup
Query and management
PACS
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

11. Digital video processing system(2)
Host should analyze the input signal while sampling and quantization to adjust grabber board setting for valid signal to utilize the dynamic range sufficiently, and to make device working in linear range.
The grabber board we used is NSP (Native Signal Process) frame-grabber board DT3153-LS, it can adjust reference, offset, gain, black level and white level by software, which make it possible for self-adaptive acquisition by software.
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

12. Jie BAO , ImageInfoLab , Hefei University of Technology
2. The principle and implementation of self-adaptive digital acquisition
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

13. Self-adaptive digital acquisition
To resolve problems brought forward in section 1, we use digital subtraction technique to realize background removing for self-adaptive acquisition, and monitor the dynamic range of image valid region to search for the best acquisition working point automatically.
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

14. Self-adaptive digital acquisition system
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

15. 3.1Valid region recognition
The acquired image is not entirely valid. Generally speaking, the valid region is a circle.
We should only count on valid region while removing background and analyzing the image feature to adjust acquisition parameters, so we must recognize the valid region at first.
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

16. Jie BAO , ImageInfoLab , Hefei University of Technology
Valid observe region
(a) Whole valid observe region. White line is detected region edge by improved seed algorithm.
(b) Valid observe region with occlusion
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

17. Valid region detection algorithm (1)
1．Compute the histogram of left and right narrow edges of the image, the gray-level corresponding to histogram peak value is the gray-level of invalid region.
2. Perform median filtering to remove noise.
3. Grow region using classical seed growing algorithm starting from any invalid point.
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

18. Valid region detection algorithm (2)
4. Generate initial mask(bilevel ) image of valid region. Perform Sobel operator to this image to extract its edge.
5. Detect circle by general Hough transform; get the radius and the center of the circle.
6. Generate valid region mask using result of step 5.
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

19. Jie BAO , ImageInfoLab , Hefei University of Technology
3.2 Background removing
Nonuniform background will affect image quality and the computing of image characteristic to adjust acquisition parameters.
So a digital subtraction will remove background signal while keep the validity of information.
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

20. Background removing algorithm
Acquire and save device background signal (I1) when device is idle.
Acquire images to be observed (I2).
Perform image operation in valid region : I3=I1-I2 ; I4=NOT I3;
I4 is the image signal removed of background.
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

21. 3.3 Setting acquisition working point
After above-mentioned pre-processing, we will adjust black level, white level, gain, reference and offset automatically based on histogram analysis of image valid region to obtain best acquisition quality.
Black level = - offset
White level = reference / gain -offset
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

22. Meaning of offset, gain and reference
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

23. Meaning of black level and white level
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

24. Working point setting rule
Decreasing offset will shift image to light zone, increasing offset will shift image to dark zone, namely offset behaves as brightness adjusting; decreasing reference will compress image to light zone, increasing reference will compress image to dark zone, namely reference behaves as contrast adjusting.
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

25. Dynamic range analysis of valid region
Analyze the proportion of dark zone and light zone in the histogram of image valid region, the aim of adjusting is to keep proper proportion of dark zone and light zone for best image acquisition performance.
Setting brightness at first to ensure dark zone isn't too much then setting contrast( that is, properly setting white level by adjusting reference).
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

26. Self-adaptive acquisition parameters setting
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

27. Universal acquisition parameters choosing
It's very inefficient and unnecessary to setting best working point every time we take fluoroscopy.
In practice, expert judgment and adjusting is used to choose universal acquisition parameters.
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

28. 3. Experiment and Conclusions
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

29. Run interface of self-adaptive acquisition module
Run interface of self-adaptive acquisition module in ImagePro™ implemented by Visual C++6.0
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

30. Valid region detection
Original Image
Valid region mask image
Sobel edge-detect image
integrated valid region
Rim of Valid Region by improved algorithm
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

31. Jie BAO , ImageInfoLab , Hefei University of Technology
Background removing
acquired image with nonuniform background
device background signal
image after removing device background
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

32. self-adaptive adjusting(1):
Acquired image before self-adaptive adjusting. Black level=0V, white level =0.7V, offset=0V, gain=1, reference =0.7V
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

33. self-adaptive adjusting(2):
Histogram of valid region in (1). mean = 70.48, median value=54. Image is too dark.
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

34. self-adaptive adjusting(3):
Acquired image after self-adaptive adjusting. Black level =-0.042V, white level =0.258V, offset=0.042V, gain=2, reference= 0.6V
scapula
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

35. self-adaptive adjusting(4):
Histogram of valid region in (3). mean = ，median value = 113.
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

36. Jie BAO , ImageInfoLab , Hefei University of Technology
Conclusions
It's possible to implement self-adaptive acquisition of medical video image automatically by integrating various images processing method. The proposed method has recognized the valid region of image and removed the background, then adjusted acquisition parameters by analyzing image dynamic range to obtain best acquisition quality. But there still some problem remained to be resolved.
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology

37. Jie BAO , ImageInfoLab , Hefei University of Technology
Thank you!
Aug.22,2000,WCC2000
Jie BAO , ImageInfoLab , Hefei University of Technology