Design and Implementation of a Mobile Medical Information System
Ying-Wen Bai
Department of Electronic Engineering
Fu Jen Catholic University
Taiwan, R.O.C.
e-mail: bai@ee.fju.edu.tw
ABSTRACT
In this paper, we design and implement a mobile medical information system that integrates the remote medical videoconference, the real-time electronic medical records and the wireless communication network, which provides users with accessing the system through wireless channel and hand-held devices such as, Tablet PC and PDA. Our design use the videoconference system compress technology using the MPEG-4 standard, a large amount of shortens video stream data at 1/24 sizes. Each picture or frame is compressed from 153.6 K bytes to 6.21 K bytes, with effective error detection, which balances the quality of the medical pictures and transmission efficiency of the wireless communication network. In addition, our design provides integration of the medical records with images, text, and waveform of the medical information obtained by the database mechanism that is easily stored, searched, transmitting and shared with the authorized medical persons.
KEY WORDS
Electronic Medical Record, Video Stream, Error Correction
1. Introduction
Recently,videoconferencing used the ISDN (Integrated Services Digital Network), which uses H.320 of CCITT to compress the information. The general users can accept H.320 image quality, but cannot accept the sound quality. Hence, some software methods compress the sound by an individual specification. In order to preserve the quality of H.320 and compatibility, every manufacturer may have different H.320 selections for receiving and decoding. But the selections can cause compatibility problems, such as control of cine-camera, form sharing, and conveying materials. Basically, H.320 only can provide the image and the sound transmission compatibility, but representation compatibility may not be preserved. Unless we use the same selections, otherwise the compatibility may be a problem [1], [2], [3].
Moreover, previous designs only provided text and still pictures of the medical record. Our design provides the dynamic images that are needed in many medical applications such as, ultrasonic images, when the doctor needs to look around over patient's bodies. Otherwise, the
Yung-Sung Huang
Department of Electronic Engineering
Fu Jen Catholic University
Taiwan, R.O.C.
e-mail: a9250615@st2.fju.edu.tw
doctor can only see a certain picture that is shot at a specific angle. The single picture is not able to see that ultrasonic pictures appearing on the original medical information. This helps the doctor lacking omni-directional reference material while judging the medical condition. Our prototype system provides the video information functions, which use the compression technology by MPEG-4, within a limited bandwidth to obtain a high elasticity and efficiency to exchange the patient's image through the wireless communication network and hand-held devices. We also enhance the electronic medical records, so the patient's instant quantity the physiological data can be stored in one’s medical record in the database, enabling one to read them from a distant place through the wireless networks. There are communication channels, client platform, database and servers that are developed by the platform as shown in Fig. 1 [9], [10]. The users at client side use PDA with embedded operating system, Tablet PC with Windows, and other hand devices. The communication channels of the system can be from outdoor wireless WAN and in hospitals through wire LAN.
Medical management development
platform
IBM PCNotebookPDAMobileInterfacePhoneLayerCustomerPlatformPatient RecordOrder RecordPhysiological RecordExamine RecordApplicationmanagementmanagementmanagementmanagementLayerPatientOrderPhysiologicalExamineRecordRecordRecordRecordComponetDatabase Access ComponentLayerDevelopSQL DatabasePlatformServerStreaming ServerDatebase ServerMobile ServerLayerDICOMGatewayHL7MessageGatewayGatewayGatewayProtocolImageMedicalLayerPlatformInformationInformationLegacy SystemSystemSystemFig. 1 Development platform for medical information system
2. The Technological Discussion for Video Systems
Our video system needs a streaming server and proxy server both using MPEG-4 in respect to the video
broadcast equipments. The video stream server is located the far-end to offer the stream of video service, and responsible to transmit the video stream file to the proxy server at the near-end. The client side uses 802.11b or cell-phone, such as PHS to obtain MPEG-4 compress stream by wireless transmission technology. After MPEG-4 decompressing and decoding at the client site, the user can watch the video stream. In our prototype system, the video stream server uses a general PC to perform the video stream to a proxy server, as well as provide “MPEG-4 Encoder & Metadata Generator”, “MPEG-4 Bit stream Transponder”, “MPEG-4 Key Frame Generator” to offer better functions. In the prototype, the proxy server also uses a general PC to offer wireless stream services.
2.1 The Key Modules of the Video Stream Server （a） When there are clients on line, the system can set
up two carry out threads to each client, which includes the control channel thread and the data channel thread.
（b） The server can tabulate and manage the clients to
access database through control channel.
（c） When the client requests a video streaming, the
server starts the service and controls the hybrid ARQ mechanism module, and turn on the packetizer and bitstream modules.
（d） In order to meet the user selection for the
transmission mode, the server carries out the data channel thread, check each data of the package in order to convey with transmission mode.
2.1.1 Hybrid ARQ Mechanism
Because the wireless communication environment has noise interference, the video stream may have more restriction. We must adopt UDP protocol in order to maintain the transmitting efficiency even in unreliable operations which are obtained by the mechanism of correcting errors during the transmitting and processing. In addition, by using the hybrid ARQ mechanism, we adopt Reed-Solomon code, which has the ability to read the “n” firsthand information pieces of packets, after which the FEC yard will produce “m” (m> n) convey and send out pieces of package via server. After the client receives “n” pieces of the packet, it can reduce firsthand information, composite method of ARQ (Hybrid ARQ Mechanism). The server end sends “n” packet data first, begin and convey parity packets, once recipient accept get “n” pieces of packets, the server will send out an acknowledge, and the server begin and convey next materials section at once promptly (n pieces of packets). Like this, even if the server does not receive acknowledge, it can continue the processing to accomplish ARQ. 2.1.2 MPEG-4 Bitstream Transcoder Module
Fig. 2 shows the transformation of the encoder for the prime field series connection and shape of the frame
composition. In each block “I” represents a reversed direction, “Q” represents quantilization, “DCT” represents discrete cosine transform, “F” represents frame memory, “MC” represents motion compensation, “MV” represents motion vector quantity and “DS” represents down sampling.
MPEG-4 DecoderMPEG-4 EncoderInputMPEG 2/4DSDCTQ2Output MPEG 4simple profileIQ1IDCT1IQ2FIDCT2MCMVMCF Fig. 2 Transformation of the encoder
Decode and encode can use different standard (such as MPEG-2 and MPEG-4), such as with different bit-rate, frame-rate, sport vector and MB (Macro block) code attitude. To increase the processing speed of the picture elements, we adopt sport vector and MB code that provide the adjusting ability of the processing speed of the code. By using the picture element to simplify the picture characteristic, the shape controls of the encoding method are described as follows：
(1) Reduce the speed of processing picture
Because the MPEG-2 standard has a structure of I-B-P (GOP) and picture speed 30 frames per second (fps), but MPEG-4 use B-frame forms, the picture (or frame) speed is 10Hz; therefore the system needs to reduce the picture speed. By using each frame head information, we learn whether the decode frame will be B-frame. The system will jump over downward frame information, until finding an I-frame to continue decoding. There are two advantages. First, B-frame does not refer to other pictures, and does not affect other frame and degrade the picture quality. Second, in order to increase processing efficiency, the MPEG-2 B-frame movement vector is the bidirectional forecast and compensates the operation of P-frame two times, if there is a jump over the next frame, we can reduce large amount of the computation complexity.
(2) Spatial downscaling
By using the spatial downscaling, we can reduce the video stream by 1/4 or 1/16. For YUV, within the neighboring we take 4 or 16 values and average in Y, U, and V. In the movement vector aspect, we use a vector median filter. For some N movement
vectors V={V1,V2,…….,VN}, the mathematical formula is shown as Eq. (1). Vmed∈V
the Video packet utilize VLC to judge the VP block to be solved by using the MPEG-4 specification. Errors in the blocks are detected by calculating the average of the
NNblock, and then find out the first block error.
∑Vmed−Vl|≤∑
Vi−Vl|,i=1,2,...,N..........(1)L=1
K=1
After Vmed as shown in Eq. (1) is obtained, this
value is used to replace the synthesis in the MB movement vector.
2.2 The Key Modules of the Client End
The client end establishes the connection for each user's running the system, which has three main functions: (1) Control Channel Thread by use of the TCP protocol
and the Streaming Video Server. The channel provides a segment channel, picks up the program table which the server provides, as well as the request broadcast movement and feedback to the server hypothesis as well as the network transmission condition.
(2) Data Channel Thread and Packet Assembler provide
the data channel used for receiving the video stream, the system offer the client the order of the video stream, with a multiple broadcast and transmit bit by bit only. After receiving the video stream, the system must use the packet assembler and make up a package frame, and then the frame can be decompressed for broadcasting. (3) The modules of the Control Playing, Decoding,
Error Detection and Concealment provides broadcast smoothly and avoids the problems of the buffer underflow. Client can monitor the buffer capacity when it receives the data; it takes the control of MPEG-4 decoding. Because the error rate of the wireless network is higher than that of the wired network, we use application layers to control and avoid the packet loss in the Video Coding Layer (VCL) state. Because the package must be checked via CRC and Check sum in the transmission course, when the Application Layer receives the packages that have been corrected. Some of packages might have losses, but the Application Layer can reduce the packet error in wireless network by the error correction mechanism. In the control part of picture playing, we will check every frame is full, or judge whether this frame can be decoded successfully. In addition, the decoder can detect the error, and then fix the packet error or loss. 2.3 Error Detection
The different compression standards before MPEG-4 are relied mainly on code structure that contains the Video Objects. There is a lot of Video Object under Video Object Layer. There are 4 small blocks under MB. The mainstream decodes the Video Object Plane. It appears
3. Data Flow Diagram
Fig. 3 shows the database of the medical information system [8]. Four kinds of professionals, such as doctor, nursing staff, patient and information system manager will access the database. The doctors use the system to access medical records for reading and updating. The nurses need to treat patients according to the medical record daily form for required prescriptions. The system manager will maintain the movements of the medical records based on every user's authority. The system manager will set up information subsystem, which includes medical record subsystem, medicines subsystem and nurse's database subsystem. PTpatient3.04.0MedicalMDSrecordmedicinesystemmedicaldatabasehistory recordsymptomsystemremedySelect medicinesMedicial history0Medical SADTinformation Jurisdiction setupsystemdoctorDiagnosis recordsystemanalysis LoginDiagnosis medicine commandPhysiologicalBasic document input2.0recordNSS1.0nursePISdatabaseperson inputsystemsystemNSnurse Fig. 3 The flow diagram of the medical database
4. Error Correction Simulation
4.1 MPEG 4 video transmission simulation under the wireless communication
The error detection simulation is realized by using Matlab based on the wireless communication environment establishing, MPEG-4 parameter establishing and “I” picture error detection and simulation results.
4.1.1 The Wireless Communication Environment Establishing
Our prototype system uses FEC (Forward Error Correction) in the wireless environment for the SNR (Signal Noise Ratio) = 0~16dB. The error rate of SNR at 16dB may be too high, therefore unsuitable to transfer MPEG-4 video-stream. In order to simulate the feasible channel, we select several kinds of SNR to do the simulation, and the results are shown in Fig. 4 and Table 1.
Table 1 Bit error rate with respect to different SNR
SNR(dB) FEC(BER) SNR(dB) FEC(BER) 0 4.07E-01 16 7.72E-03 8 1.35E-01 18 2.07E-04 12 4.32E-02 20 4.10E-04
1.00E+00FEC1.00E-0102468101214161820REB1.00E-021.00E-031.00E-04SNR(dB)
Fig. 4 Bit error rate with respect to different SNR
4.1.2 MPEG4 Parameter Establishing
The system simulation provides four segments of the video-information (Claire, Salesman, Grandma, Container), picture form QCIF in MPEG-4 with 30-frame and different video-information of each one in simulation of “I” picture.
4.1.3 “I” Picture Error Detection and Simulation Results
4.1.3.1 Simulation Techniques
The video stream is formatted by MPEG-4 code, transmitted the code via 802.11. The receiving end after decoding through 802.11, passing the MPEG-4 decoding, and improves the efficiency of the video stream.
4.1.3.2 Simulation Results and Discussion
MPEG-4 format are transmitted in the wireless environment, the error of the channel can be spread over space and time. The index of the error detection has defined the examining data rate (DR), and the frame data rate (FDR). The DR shows the error detection accuracy of examining. The FDR is used for detecting the errors of the frame data. Because “I” picture including a large amount of picture information behind for “P” picture, the system will imitate an “I” picture error and can be hidden by inserting the latency inside. The quantity under each picture and different SNR examines the results as shown in Table 2 and 3, or Fig. 5 and 6, include two kinds of No FEC of PSNR (1) on average without the error and hidden the latent picture, (2) totally detection and hide latently.
Table 2 The average error detection accuracy for No FEC protection of “I” picture
Pictures
Clairs Salesman GrandmaContainerSNRAverage
DR87.95% 84.39% 84.17%88.07%(16dB)
Average FDR11.01%
13.23%
9.89%
8.01%SNRAverage
DR89.32% 86.09% 89.45%89.71%(18dB)Average FDR
7.71%
8.98%
5.05%
6.06%
No 2/3FEC90.00%89.00%Claire)%88.00%Salesman(R87.00%D86.00%Grandma85.00%Container84.00%16.0018.00SNR(dB)
Fig. 5 FEC protection picture EC under access （a）Claire（b）
Salesman （c）Grandma（d）Container
Table 3 The average error detection accuracy for FEC protection of “I” picture
Pictures
Clairs Salesman GrandmaContainerSNR
Average DR91.22% 86.34% 92.11%92.67%(16dB)Average FDR6.66%
7.10%
5.09%4.01%SNRAverage DR94.89% 91.99% 95.82%92.98%(18dB)
Average FDR
1.96% 1.98%
1.88%
3.01%
2/3FEC96.00%94.00%)%92.00%Claire(RD90.00%SalesmanGrandma88.00%Container86.00%16.00SNR(dB)18.00
Fig. 6 “I” picture has 2/3FEC under the protection the EC simulation by（a）Claire,（b）Salesman,（c）Grandma, and（d）Container
4.1.4 Wireless Access to Packet Loss Network
For the case of packet loss network, we choose the packet size Lb= 47 bytes, the same as ATM payload with one byte for sequence. If we use the Internet packet size, the proposed video streaming can be adopted for Internet video stream. The average packet loss rate (P1) of testing packet is from 0 to 10%, and the average burst length is
fixed to 5 packets. We use the Reed-Solomon codes with channel block size =128 bytes and the allowed redundancy for error protection is fixed to 10% of the total bandwidth. Fig. 7 shows the average PSNR results and average throughput over 30 simulations under different packet loss rates. The simulation shows the system performance with pre-interleaving is much better than that of the system without pre-interleaving. For the case of P1=0.1, the system with pre-interleaving achieves more than 2dB gain in PSNR and about 40% improvement in throughput comparing with the system without pre-leaving. When the average packet loss rate P1 decreases, the difference between the system with and without pre-interleaving becomes smaller. This is because more lost packet can be recovered via channel coding in a low packet loss rate. Therefore, the proposed pre-interleaving is more efficient when the network experiences moderate and high loss rate.
2927)B25with pre-d(R23interleavingNS21without pre-P19interleaving17150.000.010.020.050.080.10Packet Loss Rate（a）
)100(%90 80with pre-utp70interleavinghguo60without pre-rhT50interleaving400125810000.....00000Packet Loss Rate（b）
Fig. 7 The comparison of pre-interleaving system under different packet loss rates (a) PSNR (b) Throughput
5. Experimental Results
The prototype system includes two sets of client ends. The first one as shown in Fig. 8 is developed on Tablet PC; the instant system picture of video-stream can be launched larger to 640X480, transfer 24 pictures or frames per second for electronic medical record, including X-Ray images and supersonic waveform files. The second one is developed on PDA as shown in Fig. 9 that the user accesses the ultrasonic file of a patient's belly. Because the operation ability of PDA is different from PC, so we will broadcast the pictures ahead. To broadcast smoothly,
we should fine- tune the storing devices, set up the video-information system in PDA with the quality of 320X240, transferring 6 frames per second.
The X-Ray image for the electronic medical record
Video Conference
System
Administration
Fig. 8 Medical information appear at a Tablet PC
Supersonic waveforms of the dynamic images
Fig. 9 Medical information appear at a PDA
6. Conclusion
In this paper, we design and implement the mobile medical information system by the integration of the software and hardware from the wireless communication, PDA, Tablet PC, and the wire networks. Due to the consideration of the power consumption, we choose the PHS system as the wireless communication. The power consumption of the PHS system is lower than that of the GSM. In addition, the bandwidth of the PHS is larger than that of GSM by 6 times. Overall, the PHS system may not interfere with the medical apparatus signals; therefore it can be accepted by many medical units. The electronic medical record has simplified the management of patient's information, as well as maintaining the use of the static image, already unable to meet the requirement of the pathology need. The related wireless networks can provide a certain bandwidth of a limited quality of the dynamic images. However, by using the compression technology of MPEG-4, our design can provide the electronic medical record at 24 frames per second for
receiving the video stream for Tablet PC. In addition, due to the performance difference of the CPU in PDA and Tablet PC, our prototype system can present different performances as shown in Table 4.Because CPU operation ability institute of PDA is smaller than Tablet PC, so there will be a lot of differences in carrying out error rate,transmission frames and resolution
Table 4 The performance measurements of the dynamic image of Tablet PC and PDA
Symposium on System Theory, 18-19 March 2002, Page(s): 406-411.
[10] Morales, M.A.; Dalmiani, S.; Carpeggiani, C.; Macerata, A.; Ghione, S., Electronic medical records in a cardiological outpatient clinic, 2002 Proceedings of the Thirty-Fourth Southeastern Symposium on System Theory, 18-19 March 2002, Page(s): 381-384.
Picture (or Average image
frame) transmission resolution rate
Tablet 640x480 54 K bps PC PDA 320x240 37.7K bps Error rate Transmission
frames per second
5.3% 24 fps 8.98% 6~8 fps
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