8.2- Main Image Processing Boards(1).pdf

SECTION 8.2.1 IMS2760 - VIP2000 VIDEO IMAGE PROCESSOR BOARD

IMS2760 VIDEO IMAGE PROCESSOR ASSEMBLY INTRODUCTION

The EMS2000 digital image processing system is designed to extend the advantages of Digital Image Technology to C-Arm Fluoroscopy. The IMS2000 has image enhancement and processing capabilities that answer specific needs for a variety of clinical C-Arm applications performed during fluoroscopy. The IMS2000 Digital Image System is an integral part of the C-Arm system, designed to work hand in hand with the C-Arm control. The IMS2000 Digital Image System was designed for easy and efficient repair. Modular design and simple operation make the IMS2000 a service-friendly system. High-reliability parts were used in its design and affords a long service life. The IMS2000 Digital Image System is a combination of several modular board sets. The following will describe the board set and its functions. VIP2000

The VIP2000 (Video Image Processor) has two boards connected together and requires two 16 bit PC/AT I/O bus slots. This two-board set digitizer the image, performs image noise reduction, controls the bus timing, and image capture and transfer of images on the video image bus. The analog front end and image digitizer are discussed in the following overview of the VIP2000 board set. The digital portion of the board controls all the image transfer, image bus, real-time image noise reduction, and supplies the digital clock for the system. REAL-TIME VIDEO FRAME ACQUISITION The VIP can digitize an input signal, RS-170 monochrome input in real time. The board supports external input and can also provide its own internal sync signals when needed. The design incorporates a Phase-Locked Loop (PLL) circuit which reduces pixel jitter to 1 /4 of a pixel and provides precise tracking. A precision 10 bit converter provides up to 1024 intensities for gray-scale applications. Supported Video Standards Standard

Application

RS-170

North American TV (monochrome)

Supported Video Standards INPUT CALIBRATION Set-up and gain controls are used to ensure that the incoming video signal accurately reflects the original picture, without losses and distortions produced by the camera or transmission line. These controls allow the service technician to calibrate individual system response independent of interference.

Exposcop 7000 / IMS2760 International Medical Systems, Inc.

Section 8.2.1 VIP2000 Board

09/23/97 Rev. 2 1

IMS2000/VIP2000 BOARD SET FRONT END OVERVIEW The front end of the VIP2000 Baseboard accepts one of three possible NTSC RS-170 video sources, passes the video through a series of gain and offset stages, then digitizer the video at 21.477 MHz sampling rate with 10-bits of resolution. The video path is shown in the diagram below. VIDEO MUX

VARIABLE GAIN AMP (Av-0-5)

DC OFFSET AMP

VIDEO MUX WITH FIXED GAIN Av-2

10-BIT A/D

G-

0 0-


ADJUTT VOUACE

WHITE COMPRESSION GAIN DAC

OFFSET DAC

VIDEO MUX The video mux is set up to accept three composite RS-170 video sources at 0.714 Vp-p video levels, but can accommodate a signal as large as 2V p-p. Each input is terminated with 75ohms which should be considered when choosing a driving source. VARIABLE GAIN STAGE The video out of the variable gain stage can be fully attenuated (Av = 0) or gained by 5. In order for the gain stage to operate over this range, the gain control voltage must swing between -IV and IV where -IV corresponds to full attenuation and IV to a gain of 5. The swing of the gain control voltage can be adjusted to alter the gain range of the amplifier via adjustment pot R112. This pot sets the reference voltage of the DAC which varies the gain control voltage. The DAC is set up so that a full scale control word will output a voltage equal to the reference voltage while a control word of zero will output a voltage equal the negative of the reference voltage. Pot R112 can be adjusted by measuring the voltage at test point W22. DC OFFSET STAGE The video out of this stage can be DC offset in both the positive and negative directions. The DC offset value is much the same as the above gain control voltage. The reference voltage of an offset DAC is adjusted via Pot R97 so that a full-scale control word will result in a positive offset while a control word of zero will result in a negative offset. The offset value is related to the DAC voltage reference with this equation - 4.02*Vref*(ll/4096) *(control word value) 3.09*Vref. With a Vref of IV, the full-scale output will be 0.93V and the output with control word equal to zero would be - 3.09V. Pot R97 can be adjusted by measuring the voltage at test point W19.

Exposcop 7000 / IMS2760 International Medical Systems, Inc.

Section 8.2.1 VIP2000 Board

09/23/97 Rev. 2 2

VIDEO MUX WITH FIXED GAIN The mux stage allows the selection of normal video or while compressed (similar to gamma function) video to be passed to the digitizer stage. This stage has a fixed gain of 2 which, in conjunction with full-scale output at the variable gain stage, allows the DC offset to be as low as -6V and still have output video fit within the digitizing window. ANALOG TO DIGITAL CONVERTER STAGE The A / D stage accepts the gained and offset video and digitizer at 21.4777MHz*with 10-bit resolution. The digitizing window, that is the range over which the A / D input is digitized, is 0 to 3.6V. Video levels above 3.6V are converted as full-scale values which levels below OV are converted as zero values. SUMMARY It can be seen from the discussions of the previous sections that the video input into the VLP2000 Baseboard can be manipulated to produce a wide range of effects by adjusting the combination of gain and offset values. The default setting for the gain reference pot and the offset reference pot are both IV. These values give full gain swing from 0 to 5 and DC offsets of -3.09V to 0.93V. These settings provide for a wide enough range of video manipulation to accommodate various video input ranges and still digitize a usable image. The analysis of the image is, however, purely subjective and thus the settings may be altered to give the best image for a particular application. The IMS2000 Video Image Processor is a unique concept in imaging. Its sophisticated design incorporates such innovations as Area of Interest processing; real-time ALU image operations; interlaced display output; and a 32-bit plane image buffer. These features allow you to combine extensive text, graphics, and overlay capabilities with the most advanced real-time image processing functions available. An IBM PC AT equipped with the VIP2000 two-board set creates an extremely powerful medical image processor which can be used for a wide range of clinical studies. The VLP2000 is equipped with image enhancement applications for postprocessing of medical images. The V1P2000 performs histograms, averaging, and many other operations. The VIP2000 image processing two-board set offers image buffering capability, real-time video frame acquisition plus a wide variety of image processing techniques in conjunction with CPU processor. REAL-TIME IMAGING The VIP2000 can perform a wide variety of image processing operations for image enhancement. The on-board ALU performs real-time, single-image operations such as frame averaging, real-time and last image hold. Noise reduction is used to enhance an incoming image for human viewing by eliminating random noise in the final digitized image. A picture is digitized a number of times (up to 16), the images are added together at video frame rates (l/30th of a second) and divided in one frame time. Since the noise in each incoming image will never be in the same place, an averaged picture of many mcoming images will produce one clear image. This technique is extremely useful for improving medical images acquired during fluoroscopy. Exposcop 7000 / IMS2760 International Medical Systems, Inc.

Section 8.2.1 VIP2000 Board

09/23/97 Rev. 2 3

VIP2000 REAL TIME NOISE REDUCTION SECTION INTRODUCTION Temporal filter section of the VLP2000 board filters image noise by factors of 2 - 16 images. The reduction of noise is approximately 50% for 2 frames to about 87% for 8 frames. PURPOSE The primary cause of the poor signal-to-noise ratio in fluoroscopic imaging is very low dose radiation used to produce the video image. With the VTP2000 board temporal filter section, the signal-to-noise ratio can be dramatically improved by averaging incoming video frames (noise tends to be a non-fixed pattern in the image where the video signal is more constant). FUNCTION The IMS2000 employs an averaging technique termed "exponential averaging", i.e., weighted frame average of the incoming video pixel (Pc) and the last or previous pixel value (Pi). The selected number value (N) of averaging sets the parameter by which the system assigns a value to a scale factor (Sf). This determines the relative weight attached to the mcoming and previous pixel values, as illustrated in Fig. 8.2.1-1. VIDEO C A M E R A

Camera Image Pixel Value (Pc)

Multinlied hvfc^ Scale Factor (Sf)

1 [Pc(Sf)+Pi(l-Sf)]

Previous Image Pixel Value (Pi)

Multiplied bv ».

P

Figure 8.2.1 - 1

1- Sf

Normalize Video Pixel Values

1

IMS2760 Image Averaging Technique.

When N=l, the incoming camera pixel value will represent 100% of the averaged image. Thus no averaging will be performed. When N=2, the incoming camera pixel value and the previous image pixel value are assigned the same weighted value reducing the noise by 50%. The effect of increasing the value N is to decrease the noise value found in each pixel. If N is selected at too high a value, the signal-to-noise ratio is very good, but the system will respond very slowly to real pixel values. This can result in blurring of the fluoroscopic image due to natural body organ movements. Thus, caution should be used in setting too high of a weighted N value for some exams. Exposcop 7000 / IMS2760 International Medical Systems, Inc.

Section 8.2.1 VIP2000 Board

09/23/97 Rev. 2 4

INPUT LOOK-UP TABLES Input look-up tables allow you to modify input gray-scale values before they enter the frame buffer. Real-time modifications include multiplication by a constant, logarithmic conversion, and multiple-level thresholding.

©1997 by International Medical Systems, Inc.. A l l rights reserved. Reproduction or issue to third parties in any form is not permitted without express written authority of International Medical Systems, Inc.

Exposcop 7000 / LMS2760 International Medical Systems, Inc.

Section 8.2.1 VIP2000 Board

09/23/97 Rev. 2 5

SECTION 8.2.2 IMS2000 - UPS2000 UPSCAN DISPLA Y BOARD

I

IMS2760 HIGH LINE RATE UPS2000 DISPLAY BOARD INTRODUCTION

The UPS2000 board performs four functions. It converts 525V X 1365H interlaced video to 1049V X 1287H interlaced video, provides graphics overlay, displays captured video on reference monitor, and process monitor. The board set requires one 16 bit ISA PC I/O slot for system operation and image transfer to ISa bus for image storage. *

PURPOSE

Provide sharp clear display of medical images with nearflickerfree data overlays for text, and graphic information, i.e., Patient name, Patient ID#, Dr. name, Images to store to disk, Graphical displays of functions and menus for operator use. The board also provides the image system with a reference display output for the right hand display monitor, complete with text and graphic overlays when needed. SCAN

CONVERSION

The UPS2000 board converts 525 lines of 30 Hz interlaced video into 1049 lines of 30 Hz interlaced video. See figure 8.2-3. The conversion is done using dual ported video RAMs (VRAM). The 525 line vertical interlaced digital video is written to VRAM one field at a time. The 1st interlaced field writes the even lines and the 2nd interlaced fields writes the odd lines. Since the VRAM is dual ported, the video can also be read from the VRAM at the same time that the interlaced video is being written to the VRAM. See Fig. 8.2 -3. For each line of video that is written to the VRAM two lines of video are read from the VRAM. By reading the lines sequentially at twice the input rate, the video is converted to a 60 Hz video output. For each 256 line field of interlaced input video there is a 525 line field of video output video. The output video is converted to a 1049 interlaced output by shifting every other frame down 1/2 line as shown in Fig. 8.2-3, Video output timing is shown in Fig. 8.2-4 CAPTURE VIDEO FOR REFERENCE MONITOR

The Process of converting the 525 line interlace video into 1049 line interlaced video requires that the video pass through a VRAM buffer. When the system stops writing video to the VRAM buffer, the last two fields are still held and the VRAM buffer can be displayed. Capturing an image on the reference monitor is done by writing two fields of video into the VRAM buffer for the reference monitor as shown in Fig. 8.2-3 GRAPHICS

OVERLAYS

The UPS2000 board set has the capability to overlay a processed image with non-destructive text and graphics. The graphics overlay is mapped as a 64k byte region of memory at paragraph address DOOOh in the PC's memory space. This allows the overlays to be accessed directly by the PC processor. Each overlay is 4 bits deep, which means it can support 16 shades of gray. All the graphics operations are performed by the PC in a similar manner to the way the PC would write to the computers display when set to graphics mode. The graphics overlay is combined with the image in a 14 bit LUT. For each pixel the graphic overlay selects the LUT for modifying the image intensity for that graphic value. See Fig. 8.2 - 5 For each video input to LUT there is a video output. The 16 bit LUT'S are selected pixel by pixel in the graphic overlay providing the system with extended capabilities in performing text and graphic displays without effecting the video image quality. Some of theflexibilityof the graphic overlays are shown in the following: 1) Invert video functions with text and graphic displays. 2) Text overlays with values of text display keyed to video level. This makes text always visible despite video background levels, i.e., white text on black background and black text on white background or half white and half gray text due to video level of blk to white gray scale. 3) Graphic blanking of video output. Example IMAGE CROP function or electronic shutters. Exposcop 7000 / 2760 International Medical Systems

Section 8.2.2 UPS2000 Board

09/24/97 Rev. 2 -1

PAN, SCROLL, AND ZOOM

(AREA OF INTEREST PROCESSING)

For those applications where you are concerned with only a portion of an image, the TJPS2000 provides and Area of Interest bit plane. The Area Of Interest allows the operator to select a rectangular area for processing. Since only the pixels within the AOI are scanned out of the image frame buffer, execution speed is proportional to the size of the area being processed. The object of interest window selects which pixels within the specified area are to be processed, thereby increasing the precision. The LMS2760 - UPS2000 board set has a 2X, 4X hardware zoom which allows the operator to expand 1/4 or 1/16 of the image so that it fills the entire display of the reference monitor. Increasing and decreasing the zoom will not destroy any data stored in the frame buffer. The UPS2000 board incorporates a special snap image buffer and a complex video bus data path to PAN and Scroll the Area Of Interest "AOI" with single-pixel precision. The relative position of the display origin can be positioned anywhere within the video memory. This makes it possible to shift the image memory by one pixel or more in any direction right ,left, up, or down. The process monitor will display a rectangular box corresponding in size to the size of zoom selected. The box will move its relative position in response to the PAN, and SCROLL direction to provide a reference for the operator of that portion of the image displayed on the reference monitor magnified. IBM PC, PC, A T are registered trademarks of International Business Machine Corp.

1

Interlaced Odd Field

3 5

VIDEO MEMORY

Upscan Odd Field

7 9

2

Interlaced Even Field

4 6

VIDEO MEMORY

Upscan Even Field

§

Figure 8.2 - 3

Exposcop 7000 / 2760 International Medical Systems

Section 8.2.2 UPS2000 Board

09/24/97 Rev. 2 - 2

Odd Field

1 Even Field

g

Time 60th of 3 a sec. 4 5 6 7 8 9

ZzEsE y

~

-

N

2 3

T i m e

4

6 0 t n

o f

a

sec.

5 6 7 8 9

10

10

I n the t i m e a n o r m a l s y s t e m reads o u t o n e v i d e o f i e l d the I M S 2 7 6 0 / U P S 2 0 0 0 d i s p l a y b o a r d r e a d s o u t the same f i e l d t w i c e a n d shifts the s e c o n d f i l e d b y 1/2 a l i n e . T h e r e b y r e d u c i n g i m a g e f l i c k e r a n d i n c r e a s i n g i m a g e q u a l i t y . T h e results are a 1049V x l 2 8 7 H d i s p l a y rate.

HORIZONTAL TIMING u

H CSYNC

525LINE a) b) c) d)

63.566 U.S 1.50 lis 4.70 lis 4.70 |is

Line Time Horizontal Front Porch Horizontal Sync Pluse Horizontal Back Porch

1049LINE 32.0 [is 0.75 us 2.50 |is 2.87 |is

V E R T I C A L TIMING

1 ^ <

g

e ^

•

525LINE e) Field Time f) Vertical Sync Pluse Width g) Blanking Interval

16.683 ms 572.10 us 1.27 ms

1049LINE 16.784 ms 576.0 pis 1.28 ms

FIGURE 8.2-4 Exposcop 7000 / 2760 International Medical Systems

Section 8.2.2 UPS2000 Board

09/24/97 Rev. 2 - 3

iw4

T E X T / G R A P H I C O V E R L A Y IMS2760- U P S 2 0 0 0 B O A R D

GRAPHIC BUFFER

10 BIT V I D E O DATA RS170 TIMING

VIDEO IMAGE BUFFER UPSCAN

GRAPHIC BUFFER

4 BIT

14 BIT LOOK UP TABLE ( LUT)

WITH GRPAHIC OVERLAY

10 BIT 1049V 1287H

4 BIT

10 B I T 1 0 4 9 X 1 2 8 7

VIDEO 1

14 B I T LOOK UP TABLE ( LUT)

10 B I T 1 0 4 9 X 1 2 8 7 :

10 BIT V I D E O DATA RS170 TIMING

VIDEO IMAGE BUFFER UPSCAN

GRAPHIC BUFFER

10 BIT V I D E O DATA RS170 T I M I N G

VIDEO IMAGE BUFFER RS170

WITH GRPAHIC OVERLAY

10 BIT 1 049V 1287H

4 BIT

10 BIT 525V 1287H

•

VIDEO 2

14 B I T LOOKUP TABLE (LUT)

10 BIT 5 2 5 V X 1 2 8 7 H W I T H GRPAHIC OVERLAY

VIDEO 3 F I G U R E 8.2-5

Exposcop 7000 / 2760 International Medical Systems

Section 8.2.2 UPS2000 Board

09/24/97 Rev. 2 - 4

SECTION 8.2.3 REAL TIME EDGE ENHANCEMENT RTE2000 BOARD

IMS2760 RTE2000 REAL TIME ENHANCEMENT

PURPOSE:

The RTE board provides the system with the ability to enhance the edge detail in an image during live fluoroscopic procedures. OPERATION:

The RTE board uses a high speed integrated circuit to perform convolutions. Convolutions are a class of neighborhood operations which enhance a particular feature of an image at the expense of others, less important features. The edge detection of the RTE board picks out the edges of objects so that the operator can more easily determine their location and shapes. The convolutions are performed by computing a new value for a pixel based on the value of its surrounding pixels. The RTE board performs standard 3x3 convolution on a 1024x525 image at 30 f/sec. LOCATION:

The RTE board is a single board Option and requires a single 16 bit ISA PC 1/O bus slot and is connected to the UPS2000 and VIP200 boards by two video bus cable connectors. The video bus data enters the RTE board from the VIP board on the VB3 video bus then is routed to the UPS2000 board for image upscan display over the VB3 video bus. The board must be connected to the VIP2000 and UPS2000 boards for proper operation. See schematics in section 8.3 NOTE:

The RTE single board is used with systems not having the DSA, and Dynamic Disk Drive options, The RDC2000 board for DSA,CINE option incorporates the RTE 2000 operation as an optional feature on the RDC2000 board. See section 8.4 .

Exposcop 7000 / 2760 International Medical Systems

Section 8.2.3 IMS2760/RTE2000 Board

04/15/96 Rev. 1 -1