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635
Perspective .
:‘
.
,
,:
Planning H. K. Huang,1
a Totally Hooshang
Digital Radiology
Kangarloo,
Paul
S. Cho, Ricky K. Taira,
A recent survey in July i 989 [1 indicates that there are approximately 50 picture archiving and communication systems (PACS) installed in Japan and about 30 installed or to be delivered in the United States and Europe. These systems are of various degrees of complexity and each tries to address a small portion of the management and processing requirements of a given radiology subspecialty. Because of the complexity of a total PACS, there is yet to be described in the literature a comprehensive plan for an entire radiology department. Two hospitals have plans for a total PACS project: the Madigan Army Hospital in Washington and Hokkaido University Hospital in Japan. At UCLA, we still believe that PACS should be implemented in a modular fashion. At a recent departmental retreat meeting on the topic of “Future Practice of Radiology,” our department endorsed a plan for total PACS implementation during the next 5 years. This paper presents the perspective of this plan. ]
::,
.
I
-.
‘-“‘-
Department Bruce K. T. Ho, and K. K. Chan
send images from the pediatric radiology host computer to the coronary care unit. Both systems have been in clinical use for over 2 years. Our 2 years of clinical experience show that clinicians are extremely pleased with the display stations and are enthusiastic about using them. The disadvantage of these two systems are the low-resolution display monitors, both of which are Si 2 x Si 2 pixels. The detailed clinical results for these two systems are documented elsewhere [2, 3]. In April 1989, we upgraded both display stations to 1 K x 1 K pixel resolution. In the pediatric radiology section, six i K x i K pixel noninterlaced display monitors are used, and in the coronary care unit, two i K x 1 K pixel noninterlaced display monitors are used. There are two other PACS modules being implemented in our department, an image network consisting of MR, CT, and sonographic images, and a PACS module for the thoracic radiology section. Descriptions of these two modules are given in the PACS Handbook ‘89 [4]. This paper describes the future development of PACS in our department.
Background
During the past 3 years we have developed two PACS modules, one in the pediatric radiology section and the other in the coronary care unit. The pediatric PACS module has six 512 x 51 2 pixel display monitors and is used for case review and daily conferences. The PACS module in the coronary care unit consists of three Si 2 x Si 2 pixel display monitors and uses an analog broadband communication system to
Received September Presented Communication
The
Center
This work was supported
Japan,
Sciences
and
the
Medical
Plaza
A new UCLA Medical Plaza across the street from the present hospital (the Center for Health Sciences) will be opened in the third quarter of 1990. The purpose of the Medical Plaza is to provide ambulatory care. When it is fully occupied, the radiology department will perform approxi-
13, 1989; accepted after revision November 1 , 1989. on Japanese Medical Imaging and Technology
at the Eighth Symposium Systems (JPACS). Osaka,
for Health
(JAMIT)/Sixth
Intemational
Symposium
on Picture
Archiving
and
July 1989.
in part by U.S. Public Health Service grant numbers AOl CA 39063 and AOl CA 404565 awarded by the National Cancer Institute,
Department of Health and Human Services. Konica Photo Ltd., Philips Medical Systems of North America, Mitsubishi Electric Corp. , Kodak, and Hitachi Maxell, Ltd. are also providing support for this research. ‘ All authors: Department of Radiological Sciences, UCLA School of Medicine, Los Angeles. CA 90024. Address reprint requests to H. K. Huang. AJR 154:635-639,
March
1990 0361-803X/90/1
543-0635
© American
Roentgen
Ray Society
HUANG
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636
mately 80,000 procedures per year. Currently the department of radiology in the Center for Health Sciences performs approximately i 90,000 procedures per year. These include both inpatients and outpatients. When the ambulatory care center opens in the Medical Plaza, all the outpatient services will be conducted in the new facility. The radiology department will occupy approximately 30,000 square feet spanning two 1evels. The new facility will have two CT scanners, two MR scanners, three gamma cameras, three sonography units, three mammography units, and about i 0 radiographic and fluorographic rooms. In addition, one computed radiography system will be installed in the pediatric radiology area. An additional two new computed radiography units may be installed, depending on the available image quality for general chest and bone radiographic studies. The radiology department in the Medical Plaza and the current radiology department in the Center for Health Sciences will be under a single administration. The question was raised whether or not to plan the implementation of a totally digital radiology department for both the Medical Plaza and the Center for Health Sciences. Our current thought is that implementing a totally digital radiology operation is easier in the Medical Plaza than in the current radiology department in the Center for Health Sciences for two reasons. First, it is easier to design a totally digital department when the building floor plan is still flexible. Second, the current radiology department is organized according to radiology subspecialties which makes the department fragmented and therefore difficult for PACS implementation. After careful consideration we devised the following plan. In the Center for Health Sciences, we will implement a 2K x 2K pixel display station in pediatric radiology for primary diagnosis. In addition, we will complete the integration of the CT, MR, and sonography subsystems and implement the thoracic chest PACS module. In the Medical Plaza, we will implement a CT/MR network and a pediatric PACS module that are similar to the network and the module in the Center for Health Sciences. We will develop a central archiving station and review stations for CT, MR, bone, chest, and other specialties. An image-communication network will be established between the Center for Health Sciences and the Medical Plaza.
Communication
Between
and the Medical
Plaza
the Center
for Health
Sciences
The distance between the Center for Health Sciences and the Medical Plaza is less than 2000 feet. However, if we lay a fiber-optic cable between a PACS host computer in the Department of Radiological Sciences in the Center for Health Sciences and a host computer in the Medical Plaza, the actual cable requirement is 4700 feet, or a little less than i .5 km. We have installed 64 optical fibers with specifications satisfying the FDDI (Fiber Distributed Data Interface) requirement. The fiber is run through a tunnel under the street separating the two buildings. The fiber’s outer diameter is 1 25.0 ± 2.0 m, and the inner diameter is 62.5 ± 3.0 Mm. The price of the fiber is approximately 40 cents per fiber per foot. One end of the cable at the Center for Health Sciences will be connected
ET
AL.
AJA:154,
March
1990
to a second fiber-optic-cable system dedicated to the medical school by the UCLA campus network authority. This cable will run throughout the radiology department. The other end of the cable will be connected to a third fiber-cable system in the Medical Plaza. This cable system will span the entire radiology department. The method of connecting these three sets of cable system has not been finalized. We are contemplating three possible network connections between the two buildings. The first is a i gigabit per second network (UltraNetwork, San Jose, CA). The second is a i 00 megabit per second rooted-tree network (Canstar, Toronto, Canada). The concentrator (or the hub) of the Canstar network can connect to various acquisition nodes through an EIU (Ethernet Interface Unit) with a maximum speed of 10 megabits per second, or to a display station through a HIU (host interface unit) with a maximum speed of i 00 megabits per second. The third is a standard FDDI network with a maximum speed of i 00 megabits per second. All three types of network are now in our department for testing. Within the next 6 months, we will derive an efficient architecture to link these three networks [5]. Within the Center for Health Sciences, and within the Medical Plaza, we will use Ethernet for transmitting images between the image acquisition devices and the computer of a PACS module and from the computer to one of several optical storage devices. For image transmission between the computer and a display station, we will use the FDDI and the Ultranet. We think that it is not necessary to use FDDI for connecting the image acquisition devices and the optical storage devices because they have relatively slower transfer rates. On the other hand, image transmission between the host computer and display stations requires a high transfer rate because workstation usage is demanding during clinical hours. In this case, FDDI or the faster network is necessary.
PACS Clusters
and Image Data Base
As we are implementing the PACS in a modular fashion, we have decided to adopt a hierarchical file directory system [6]. In this architecture, a master directory contains image descriptive data of all inpatients registered in the Center for Health Sciences and all outpatients registered in the Medical Plaza. The PACS module (or modules) forms a cluster and each cluster maintains a cluster directory (Fig. i). The cluster directory Contains only image descriptive data of patients belonging to the cluster. The optical storage device in a cluster contains images of patients belonging to the cluster. The master directory will be connected to the radiology information system to obtain demographic data and report information on patients. A cluster directory as well as the master directory is updated when a new patient’s image is acquired. Each cluster maintains a data management system responsible for image management of that particular cluster and can communicate with other clusters. Of the PACS modules, earlier modules will consist of older components and newer modules will use the latest technology. For economic reasons, we cannot upgrade older modules whenever a new module is implemented. However, a
AJA:154,
March
DIGITAL
1990
RADIOLOGY
cluster directory of images.
Acquisition
:
Devices
.
t
(1)
Downloaded from www.ajronline.org by 59.124.38.73 on 10/20/15 from IP address 59.124.38.73. Copyright ARRS. For personal use only; all rights reserved
Clusters
‘\Concentrator
HOST()
L3)
)
Other
;;z_:;:
Clusters
Concentrator
//
/7
(
ri
Fig. 1.-Architecture ages to concentrator
-
-.--.
..
-
(L b
(Memory)
y)
Transfer (3)\\ i
:
\\St
-
I
Clusters
CACHE
,,H-
FDD1 EIU HiU
J;
Rate :l5OMbs : lOMbs 15.lO5Mbs
:
of a cluster. (1) Acquisition devices transmit rn(hub) and host computer. (2) Images are reformatted
to American College of Radiology/National Electrical Manufacturers Association logical standard, stored temporarily in cache memory and archived onto optical disk library. (3) Reformatted images are selectively sent to proper display stations where they are stored in local storage for up to 2 weeks. FDDI = Fiber Distributed Data Interface; EIU = Ethernet interface unit; HIU = host interface unit.
component incompatible
Clusters
in a module will be replaced with other modules.
in the Center
for Health
when
637
and is updated
immediately
upon
acquisition
-:
.
1
.
Other
DEPARTMENT
it becomes
Sciences
In the Center for Health Sciences, the pediatric radiology module and the coronary care unit module form a cluster, using the VAX-i i/750 computer (Digital Equipment Corporation, Maynard, MA) as the host (an older technology). This cluster acquires images from a computed radiography system, MR, CT, and sonography. Images are sent to a file server, which is composed of both magnetic and optical storage devices. The optical storage consists of a 64-platter Filenet (Costa Mesa, CA) optical library with two Hitachi 30i (Tokyo, Japan) optical disk drives. Each platter can store 2.6 gigabytes of data. The file server is connected to a display station with six 1 K x 1 K pixel monitors and a display station with two 2K x 2K pixel monitors in pediatric radiology and a two-monitor 1 K display station in the coronary care unit. The magnetic disks in the file server also can store images transferred from other clusters on a temporary basis. This cluster remains unchanged operationally regardless of any other future PACS development except that hardware and software will be upgraded periodically. This upgrading should not affect the operation of other clusters. The second cluster in the Center for Health Sciences is the CT, MR, and sonography network. Images are sent from acquisition devices to a hub of the network (equivalent to a telephone switch circuit) connected to a file server consisting of a Kodak 6800 optical library (Rochester, NY) and a set of magnetic disk drives. The library contains i 00 platters with 6.8 gigabytes storage capacity per platter. The server is connected to a second hub, which in turn is connected to different display stations through a network with a i 00 megabits per second transfer rate. The cluster also has its own
in the Medical
Plaza
The PACS operation in the Medical Plaza will initially consist of two clusters: one handles all the MR, CT, and sonographic images and the second, all pediatric radiology images. Other new clusters will be added when it becomes necessary. The operation of this cluster is similar to that of any cluster in the Center for Health Sciences. The optical disk library in this cluster will store images of patients originating from the Medical Plaza. .
Communication Between Sciences and the Medical
Clusters Plaza
in the Center
for Health
The cluster directories in the Center for Health Sciences and the cluster directories in the Medical Plaza will be linked by the master directory (Fig. 2). As an example, when a pediatric patient is transferred from outpatient to inpatient, a patient status change will trigger transfer of this patient’s images from the optical storage in the Medical Plaza to the pediatric radiology cluster in the Center for Health Sciences. Both cluster directories and the master directory will be updated and show that this particular patient has been transferred to the pediatric radiology cluster in the Centerfor Health Sciences as an inpatient. Images of this patient originally stored in the Medical Plaza optical library will be transferred through the fiber-optic link and stored in the pediatric radiology file server in the Center for Health Sciences. The images are then transmitted from the file server to the pediatric viewing station’s local storage. However, this set of images will not be stored in the optical library in the Center for Health Sciences because permanent records are already in the Medical Plaza optical library. This patient’s images will remain in
CENTER FOR HEALTH SCIENCES Cluster
I
MEDICAL
PLAZA
...
1
(4) A
Data Managers Server
Fig. 2.-Architecture of a total picture archiving and communication system with many clusters. (1) Many clusters in Center for Health Sciences are connected to a hub. (2) Many clusters in Medical Plaza are connected to a second hub. (3) Two hubs are connected with a high-speed communication network. (4) Data management server controls data and image flow through network.
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638
HUANG
the temporary magnetic storage assigned to the display station until the patient is discharged. All new images of this patient acquired in the Center for Health Sciences as an inpatient will be appended to the same patient’s file in the local storage. These newly acquired images also will be transmitted to the Medical Plaza optical library for long-term archiving. Similar operational procedures can be derived if an inpatient from the Center for Health Sciences is transferred to the Medical Plaza as an outpatient. Thus, it does not matter whether the patient is originally registered as an outpatient in the Medical Plaza or as an inpatient in the Center for Health Sciences, because both locations can access images via the master directory of the data management system and the PACS network. The only difference is that if the patient is originally registered as an outpatient, the patient’s images will be permanently stored in the optical library of the Medical Plaza. On the other hand, if the patient is originally registered in the Center for Health Sciences as an inpatient then the images of this patient will be stored permanently in the optical library of the pediatric cluster in the Center for Health Sciences. As far as system operations are concerned, this permanent storage arrangement is transparent to the user. From a departmental point of view, only one image management system exists; the master directory keeps track of where the images are stored. This method of management will allow functional unity in a physically divided department. We anticipate that about 20% of the images will be transferred between the Center for Health Sciences and the Medical Plaza. As the data management system is independent of the hardware configuration, a change in any piece of hardware will not affect the operation of the file directory system. Currently, the two working PACS modules in pediatric radiology and in the coronary care unit in the Center for Health Sciences use custom-built data-base-management software. Images of different format and sources are first converted to a UCLA standard image format [7], which has description headers that are logically compatible with the American College of Radiology/National Electrical Manufacturers Association standard [8] before they are stored in the data bases. However, when we integrate many PACS modules throughout the department, we will use a commercial data-basemanagement system because of the complexity in the datamanagement requirements. For this reason we have installed the SYBASE (SYBASE, Emeryville, CA) data-base-management system. This data-base system is a true relational database system and can perform all the functions described previously. We will gradually convert the current data bases in pediatric radiology and in the coronary care unit to this new data-base system. Once it is implemented, the manufacturer will continue upgrading the data-base-management system. However, regardless of the upgrading, the image data will remain intact. The approach we are taking will minimize the chances of our hardware and software becoming obsolete. In dealing with the hardware, we can upgrade any piece of equipment within a cluster without affecting the total PACS operation, and the manufacturer will maintain and upgrade the data-base functionality of the software. At the same time,
ET AL.
AJA:154,
March
1990
the integrity of the image data will remain intact in the data base. We also can replace any cluster in the PACS with a commercial module when it becomes apparent that the commercial system outperforms the laboratory module.
Pitfalls
in Implementation
of PACS
Modules
During our past 3 years of experience with the PACS systems, we have identified a few operational difficulties that should be circumvented in a successful PACS implementation. To begin with, a prototype PACS system is difficult to upgrade in a clinical environment. Although we have implemented two PACS modules and they have been in operation for 2 years, we find that the day-to-day operation, service maintenance, and maintaining the integrity of the system can be very tedious and time consuming. There are two reasons for this. First, once a system is released for clinical operation it is difficult to service the system because it is used 24 hr a day and 7 days a week. As it is a prototype system, it is one of a kind. It is difficult for a research team to upgrade a system and test it in clinical environment unless a second similar system is also available in the research laboratory. As a result, the research team always plays a catch-up game once the system is in clinical use. Second, a successful operation of PACS relies on consistent uptime of image acquisition devices including CT, MR, and computed radiography. An image acquisition device does go down from time to time because of preventive maintenance, operator errors, and so forth. If one imaging acquisition device is not functioning properly, images from this device will not be transmitted to the PACS host computer during the time of image generation. As a result, the image data base is not up to date and requires an operator to retrieve images from other stations or digitize a piece of film. This will cause the arrival of images at a workstation to be delayed. In the worst case, the communication protocol in the network, if not supervised properly, can even fail to transmit the images. Another difficulty is that when a major component upgrade is performed in a cluster it will affect the clinical perspective. For example, in pediatric radiology, we upgraded the system from Si 2 x Si 2 pixel monitors to i K x 1 K pixel monitors. As a result, image quality improves but the display time increases from 2 sec to 5 sec. Many explanations have to be made to the clinicians for them to accept this compromise. This psychological factor was not anticipated when we upgraded the pediatric system from Si 2 x Si 2 pixel to i K x 1 K pixel monitors. Operating the PACS smoothly requires a special operator’s attention to the system. We had to train a person with some knowledge of digital image processing, image acquisition, and display stations, as well as X-ray technology for maintaining the operational integrity of the system. This requirement was not anticipated when we implemented the system. We now have a new category of profession in our department called the PACS coordinator. We plan to continue to recruit from the existing technologist pool in the department. Along with these difficulties, we also have made the following observations.
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AJR:1 54,
March
1990
DIGITAL
RADIOLOGY
First, we believe that PACS should be implemented in a modular fashion. There are many aspects in a given operating condition and environment that make one module quite different from another. Each module should have its own specifications and the module will require a period of refinement before it is clinically useful. As the learning process improves, the acceptance of the newer modules by clinical users will become faster and easier. Second, we believe all technologies required to implement PACS are available. The only two exceptions might be digital image acquisition of conventional radiographs and image communication. As of today, we are still not convinced that computed radiography images can completely replace conventional analog films for all types of procedures because of various requirements. However, we do expect that computed radiography manufacturers can improve the image quality to equal that of conventional analog images in the near future. In image transmission, faster hardware and smarter protocols still need to be developed for efficient communication. Lastly, we do not recommend that every radiology department or hospital implement its own PACS system in-house, as it does require substantial financial and manpower commitment. With clinical data of PACS generated by other research centers and our department, we hope the manufacturers will be able to adapt and use this information, and come up with turnkey PACS systems with specifications suitable for different hospitals or departments. In summary, we believe that the implementation of PACS in a radiology department or a hospital is inevitable. All the
DEPARTMENT
639
technology is available. The question concerning PACS implementation is not why, but when. With cooperation from the radiology community and the manufacturers, we believe PACS can be implemented successfully [9]. PACS will serve as a powerful tool for better health care delivery and for facilitating research and teaching.
REFERENCES 1 . Huang HK, Cho PS, Taira
communication
systems
AK, Ho BK, Chan in Japan-three
KK. Picture
years
later.
archiving AiR
and
1990;154:
415-417
2. Taira AK, Mankovich NJ, Boechat MI, Kangarloo H, Huang and implementation of a picture archiving and communication pediatric radiology. AJR 1988;150: 1117-1121 3. Cho PS, Huang HK, Tillisch J, Kangarloo radiologic picture archiving and communication unit. AiR 1988;151 :823-827 4. Huang HK. Experience in the use of PACS:
plans. In: Tsujiuchi J. PACShandbook
HK. Design system for
H. Clinical evaluation of a system for a coronary care present
problems
and future
‘89. Tokyo: Japanese PACS Society,
1989: 33-43 5. Templeton AW, Cox GG, Dwyer SJ III. Digit& image management networks: current status. Radiology 1988;169: 193-199 6. Chu WW. Performance of the file directory system for data bases in star and distributed network. AFIPS Coot Proc 1976;45:3-13 7. Aatib 0. Image file structure and data communication format, IPL Note
23.01 Los Angeles: UCLA, 1988 .
8. 9.
AcR-NEMA digital imaging and communication standard, 85. Washington, D.C.: NEMA, 1985 Meznch AS. The imp1ation of PACS for radiology 1988;151 :828
Publication
300-
practice.
AiR
635
Perspective .
:‘
.
,
,:
Planning H. K. Huang,1
a Totally Hooshang
Digital Radiology
Kangarloo,
Paul
S. Cho, Ricky K. Taira,
A recent survey in July i 989 [1 indicates that there are approximately 50 picture archiving and communication systems (PACS) installed in Japan and about 30 installed or to be delivered in the United States and Europe. These systems are of various degrees of complexity and each tries to address a small portion of the management and processing requirements of a given radiology subspecialty. Because of the complexity of a total PACS, there is yet to be described in the literature a comprehensive plan for an entire radiology department. Two hospitals have plans for a total PACS project: the Madigan Army Hospital in Washington and Hokkaido University Hospital in Japan. At UCLA, we still believe that PACS should be implemented in a modular fashion. At a recent departmental retreat meeting on the topic of “Future Practice of Radiology,” our department endorsed a plan for total PACS implementation during the next 5 years. This paper presents the perspective of this plan. ]
::,
.
I
-.
‘-“‘-
Department Bruce K. T. Ho, and K. K. Chan
send images from the pediatric radiology host computer to the coronary care unit. Both systems have been in clinical use for over 2 years. Our 2 years of clinical experience show that clinicians are extremely pleased with the display stations and are enthusiastic about using them. The disadvantage of these two systems are the low-resolution display monitors, both of which are Si 2 x Si 2 pixels. The detailed clinical results for these two systems are documented elsewhere [2, 3]. In April 1989, we upgraded both display stations to 1 K x 1 K pixel resolution. In the pediatric radiology section, six i K x i K pixel noninterlaced display monitors are used, and in the coronary care unit, two i K x 1 K pixel noninterlaced display monitors are used. There are two other PACS modules being implemented in our department, an image network consisting of MR, CT, and sonographic images, and a PACS module for the thoracic radiology section. Descriptions of these two modules are given in the PACS Handbook ‘89 [4]. This paper describes the future development of PACS in our department.
Background
During the past 3 years we have developed two PACS modules, one in the pediatric radiology section and the other in the coronary care unit. The pediatric PACS module has six 512 x 51 2 pixel display monitors and is used for case review and daily conferences. The PACS module in the coronary care unit consists of three Si 2 x Si 2 pixel display monitors and uses an analog broadband communication system to
Received September Presented Communication
The
Center
This work was supported
Japan,
Sciences
and
the
Medical
Plaza
A new UCLA Medical Plaza across the street from the present hospital (the Center for Health Sciences) will be opened in the third quarter of 1990. The purpose of the Medical Plaza is to provide ambulatory care. When it is fully occupied, the radiology department will perform approxi-
13, 1989; accepted after revision November 1 , 1989. on Japanese Medical Imaging and Technology
at the Eighth Symposium Systems (JPACS). Osaka,
for Health
(JAMIT)/Sixth
Intemational
Symposium
on Picture
Archiving
and
July 1989.
in part by U.S. Public Health Service grant numbers AOl CA 39063 and AOl CA 404565 awarded by the National Cancer Institute,
Department of Health and Human Services. Konica Photo Ltd., Philips Medical Systems of North America, Mitsubishi Electric Corp. , Kodak, and Hitachi Maxell, Ltd. are also providing support for this research. ‘ All authors: Department of Radiological Sciences, UCLA School of Medicine, Los Angeles. CA 90024. Address reprint requests to H. K. Huang. AJR 154:635-639,
March
1990 0361-803X/90/1
543-0635
© American
Roentgen
Ray Society
HUANG
Downloaded from www.ajronline.org by 59.124.38.73 on 10/20/15 from IP address 59.124.38.73. Copyright ARRS. For personal use only; all rights reserved
636
mately 80,000 procedures per year. Currently the department of radiology in the Center for Health Sciences performs approximately i 90,000 procedures per year. These include both inpatients and outpatients. When the ambulatory care center opens in the Medical Plaza, all the outpatient services will be conducted in the new facility. The radiology department will occupy approximately 30,000 square feet spanning two 1evels. The new facility will have two CT scanners, two MR scanners, three gamma cameras, three sonography units, three mammography units, and about i 0 radiographic and fluorographic rooms. In addition, one computed radiography system will be installed in the pediatric radiology area. An additional two new computed radiography units may be installed, depending on the available image quality for general chest and bone radiographic studies. The radiology department in the Medical Plaza and the current radiology department in the Center for Health Sciences will be under a single administration. The question was raised whether or not to plan the implementation of a totally digital radiology department for both the Medical Plaza and the Center for Health Sciences. Our current thought is that implementing a totally digital radiology operation is easier in the Medical Plaza than in the current radiology department in the Center for Health Sciences for two reasons. First, it is easier to design a totally digital department when the building floor plan is still flexible. Second, the current radiology department is organized according to radiology subspecialties which makes the department fragmented and therefore difficult for PACS implementation. After careful consideration we devised the following plan. In the Center for Health Sciences, we will implement a 2K x 2K pixel display station in pediatric radiology for primary diagnosis. In addition, we will complete the integration of the CT, MR, and sonography subsystems and implement the thoracic chest PACS module. In the Medical Plaza, we will implement a CT/MR network and a pediatric PACS module that are similar to the network and the module in the Center for Health Sciences. We will develop a central archiving station and review stations for CT, MR, bone, chest, and other specialties. An image-communication network will be established between the Center for Health Sciences and the Medical Plaza.
Communication
Between
and the Medical
Plaza
the Center
for Health
Sciences
The distance between the Center for Health Sciences and the Medical Plaza is less than 2000 feet. However, if we lay a fiber-optic cable between a PACS host computer in the Department of Radiological Sciences in the Center for Health Sciences and a host computer in the Medical Plaza, the actual cable requirement is 4700 feet, or a little less than i .5 km. We have installed 64 optical fibers with specifications satisfying the FDDI (Fiber Distributed Data Interface) requirement. The fiber is run through a tunnel under the street separating the two buildings. The fiber’s outer diameter is 1 25.0 ± 2.0 m, and the inner diameter is 62.5 ± 3.0 Mm. The price of the fiber is approximately 40 cents per fiber per foot. One end of the cable at the Center for Health Sciences will be connected
ET
AL.
AJA:154,
March
1990
to a second fiber-optic-cable system dedicated to the medical school by the UCLA campus network authority. This cable will run throughout the radiology department. The other end of the cable will be connected to a third fiber-cable system in the Medical Plaza. This cable system will span the entire radiology department. The method of connecting these three sets of cable system has not been finalized. We are contemplating three possible network connections between the two buildings. The first is a i gigabit per second network (UltraNetwork, San Jose, CA). The second is a i 00 megabit per second rooted-tree network (Canstar, Toronto, Canada). The concentrator (or the hub) of the Canstar network can connect to various acquisition nodes through an EIU (Ethernet Interface Unit) with a maximum speed of 10 megabits per second, or to a display station through a HIU (host interface unit) with a maximum speed of i 00 megabits per second. The third is a standard FDDI network with a maximum speed of i 00 megabits per second. All three types of network are now in our department for testing. Within the next 6 months, we will derive an efficient architecture to link these three networks [5]. Within the Center for Health Sciences, and within the Medical Plaza, we will use Ethernet for transmitting images between the image acquisition devices and the computer of a PACS module and from the computer to one of several optical storage devices. For image transmission between the computer and a display station, we will use the FDDI and the Ultranet. We think that it is not necessary to use FDDI for connecting the image acquisition devices and the optical storage devices because they have relatively slower transfer rates. On the other hand, image transmission between the host computer and display stations requires a high transfer rate because workstation usage is demanding during clinical hours. In this case, FDDI or the faster network is necessary.
PACS Clusters
and Image Data Base
As we are implementing the PACS in a modular fashion, we have decided to adopt a hierarchical file directory system [6]. In this architecture, a master directory contains image descriptive data of all inpatients registered in the Center for Health Sciences and all outpatients registered in the Medical Plaza. The PACS module (or modules) forms a cluster and each cluster maintains a cluster directory (Fig. i). The cluster directory Contains only image descriptive data of patients belonging to the cluster. The optical storage device in a cluster contains images of patients belonging to the cluster. The master directory will be connected to the radiology information system to obtain demographic data and report information on patients. A cluster directory as well as the master directory is updated when a new patient’s image is acquired. Each cluster maintains a data management system responsible for image management of that particular cluster and can communicate with other clusters. Of the PACS modules, earlier modules will consist of older components and newer modules will use the latest technology. For economic reasons, we cannot upgrade older modules whenever a new module is implemented. However, a
AJA:154,
March
DIGITAL
1990
RADIOLOGY
cluster directory of images.
Acquisition
:
Devices
.
t
(1)
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Clusters
‘\Concentrator
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Concentrator
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Fig. 1.-Architecture ages to concentrator
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Clusters
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of a cluster. (1) Acquisition devices transmit rn(hub) and host computer. (2) Images are reformatted
to American College of Radiology/National Electrical Manufacturers Association logical standard, stored temporarily in cache memory and archived onto optical disk library. (3) Reformatted images are selectively sent to proper display stations where they are stored in local storage for up to 2 weeks. FDDI = Fiber Distributed Data Interface; EIU = Ethernet interface unit; HIU = host interface unit.
component incompatible
Clusters
in a module will be replaced with other modules.
in the Center
for Health
when
637
and is updated
immediately
upon
acquisition
-:
.
1
.
Other
DEPARTMENT
it becomes
Sciences
In the Center for Health Sciences, the pediatric radiology module and the coronary care unit module form a cluster, using the VAX-i i/750 computer (Digital Equipment Corporation, Maynard, MA) as the host (an older technology). This cluster acquires images from a computed radiography system, MR, CT, and sonography. Images are sent to a file server, which is composed of both magnetic and optical storage devices. The optical storage consists of a 64-platter Filenet (Costa Mesa, CA) optical library with two Hitachi 30i (Tokyo, Japan) optical disk drives. Each platter can store 2.6 gigabytes of data. The file server is connected to a display station with six 1 K x 1 K pixel monitors and a display station with two 2K x 2K pixel monitors in pediatric radiology and a two-monitor 1 K display station in the coronary care unit. The magnetic disks in the file server also can store images transferred from other clusters on a temporary basis. This cluster remains unchanged operationally regardless of any other future PACS development except that hardware and software will be upgraded periodically. This upgrading should not affect the operation of other clusters. The second cluster in the Center for Health Sciences is the CT, MR, and sonography network. Images are sent from acquisition devices to a hub of the network (equivalent to a telephone switch circuit) connected to a file server consisting of a Kodak 6800 optical library (Rochester, NY) and a set of magnetic disk drives. The library contains i 00 platters with 6.8 gigabytes storage capacity per platter. The server is connected to a second hub, which in turn is connected to different display stations through a network with a i 00 megabits per second transfer rate. The cluster also has its own
in the Medical
Plaza
The PACS operation in the Medical Plaza will initially consist of two clusters: one handles all the MR, CT, and sonographic images and the second, all pediatric radiology images. Other new clusters will be added when it becomes necessary. The operation of this cluster is similar to that of any cluster in the Center for Health Sciences. The optical disk library in this cluster will store images of patients originating from the Medical Plaza. .
Communication Between Sciences and the Medical
Clusters Plaza
in the Center
for Health
The cluster directories in the Center for Health Sciences and the cluster directories in the Medical Plaza will be linked by the master directory (Fig. 2). As an example, when a pediatric patient is transferred from outpatient to inpatient, a patient status change will trigger transfer of this patient’s images from the optical storage in the Medical Plaza to the pediatric radiology cluster in the Center for Health Sciences. Both cluster directories and the master directory will be updated and show that this particular patient has been transferred to the pediatric radiology cluster in the Centerfor Health Sciences as an inpatient. Images of this patient originally stored in the Medical Plaza optical library will be transferred through the fiber-optic link and stored in the pediatric radiology file server in the Center for Health Sciences. The images are then transmitted from the file server to the pediatric viewing station’s local storage. However, this set of images will not be stored in the optical library in the Center for Health Sciences because permanent records are already in the Medical Plaza optical library. This patient’s images will remain in
CENTER FOR HEALTH SCIENCES Cluster
I
MEDICAL
PLAZA
...
1
(4) A
Data Managers Server
Fig. 2.-Architecture of a total picture archiving and communication system with many clusters. (1) Many clusters in Center for Health Sciences are connected to a hub. (2) Many clusters in Medical Plaza are connected to a second hub. (3) Two hubs are connected with a high-speed communication network. (4) Data management server controls data and image flow through network.
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638
HUANG
the temporary magnetic storage assigned to the display station until the patient is discharged. All new images of this patient acquired in the Center for Health Sciences as an inpatient will be appended to the same patient’s file in the local storage. These newly acquired images also will be transmitted to the Medical Plaza optical library for long-term archiving. Similar operational procedures can be derived if an inpatient from the Center for Health Sciences is transferred to the Medical Plaza as an outpatient. Thus, it does not matter whether the patient is originally registered as an outpatient in the Medical Plaza or as an inpatient in the Center for Health Sciences, because both locations can access images via the master directory of the data management system and the PACS network. The only difference is that if the patient is originally registered as an outpatient, the patient’s images will be permanently stored in the optical library of the Medical Plaza. On the other hand, if the patient is originally registered in the Center for Health Sciences as an inpatient then the images of this patient will be stored permanently in the optical library of the pediatric cluster in the Center for Health Sciences. As far as system operations are concerned, this permanent storage arrangement is transparent to the user. From a departmental point of view, only one image management system exists; the master directory keeps track of where the images are stored. This method of management will allow functional unity in a physically divided department. We anticipate that about 20% of the images will be transferred between the Center for Health Sciences and the Medical Plaza. As the data management system is independent of the hardware configuration, a change in any piece of hardware will not affect the operation of the file directory system. Currently, the two working PACS modules in pediatric radiology and in the coronary care unit in the Center for Health Sciences use custom-built data-base-management software. Images of different format and sources are first converted to a UCLA standard image format [7], which has description headers that are logically compatible with the American College of Radiology/National Electrical Manufacturers Association standard [8] before they are stored in the data bases. However, when we integrate many PACS modules throughout the department, we will use a commercial data-basemanagement system because of the complexity in the datamanagement requirements. For this reason we have installed the SYBASE (SYBASE, Emeryville, CA) data-base-management system. This data-base system is a true relational database system and can perform all the functions described previously. We will gradually convert the current data bases in pediatric radiology and in the coronary care unit to this new data-base system. Once it is implemented, the manufacturer will continue upgrading the data-base-management system. However, regardless of the upgrading, the image data will remain intact. The approach we are taking will minimize the chances of our hardware and software becoming obsolete. In dealing with the hardware, we can upgrade any piece of equipment within a cluster without affecting the total PACS operation, and the manufacturer will maintain and upgrade the data-base functionality of the software. At the same time,
ET AL.
AJA:154,
March
1990
the integrity of the image data will remain intact in the data base. We also can replace any cluster in the PACS with a commercial module when it becomes apparent that the commercial system outperforms the laboratory module.
Pitfalls
in Implementation
of PACS
Modules
During our past 3 years of experience with the PACS systems, we have identified a few operational difficulties that should be circumvented in a successful PACS implementation. To begin with, a prototype PACS system is difficult to upgrade in a clinical environment. Although we have implemented two PACS modules and they have been in operation for 2 years, we find that the day-to-day operation, service maintenance, and maintaining the integrity of the system can be very tedious and time consuming. There are two reasons for this. First, once a system is released for clinical operation it is difficult to service the system because it is used 24 hr a day and 7 days a week. As it is a prototype system, it is one of a kind. It is difficult for a research team to upgrade a system and test it in clinical environment unless a second similar system is also available in the research laboratory. As a result, the research team always plays a catch-up game once the system is in clinical use. Second, a successful operation of PACS relies on consistent uptime of image acquisition devices including CT, MR, and computed radiography. An image acquisition device does go down from time to time because of preventive maintenance, operator errors, and so forth. If one imaging acquisition device is not functioning properly, images from this device will not be transmitted to the PACS host computer during the time of image generation. As a result, the image data base is not up to date and requires an operator to retrieve images from other stations or digitize a piece of film. This will cause the arrival of images at a workstation to be delayed. In the worst case, the communication protocol in the network, if not supervised properly, can even fail to transmit the images. Another difficulty is that when a major component upgrade is performed in a cluster it will affect the clinical perspective. For example, in pediatric radiology, we upgraded the system from Si 2 x Si 2 pixel monitors to i K x 1 K pixel monitors. As a result, image quality improves but the display time increases from 2 sec to 5 sec. Many explanations have to be made to the clinicians for them to accept this compromise. This psychological factor was not anticipated when we upgraded the pediatric system from Si 2 x Si 2 pixel to i K x 1 K pixel monitors. Operating the PACS smoothly requires a special operator’s attention to the system. We had to train a person with some knowledge of digital image processing, image acquisition, and display stations, as well as X-ray technology for maintaining the operational integrity of the system. This requirement was not anticipated when we implemented the system. We now have a new category of profession in our department called the PACS coordinator. We plan to continue to recruit from the existing technologist pool in the department. Along with these difficulties, we also have made the following observations.
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AJR:1 54,
March
1990
DIGITAL
RADIOLOGY
First, we believe that PACS should be implemented in a modular fashion. There are many aspects in a given operating condition and environment that make one module quite different from another. Each module should have its own specifications and the module will require a period of refinement before it is clinically useful. As the learning process improves, the acceptance of the newer modules by clinical users will become faster and easier. Second, we believe all technologies required to implement PACS are available. The only two exceptions might be digital image acquisition of conventional radiographs and image communication. As of today, we are still not convinced that computed radiography images can completely replace conventional analog films for all types of procedures because of various requirements. However, we do expect that computed radiography manufacturers can improve the image quality to equal that of conventional analog images in the near future. In image transmission, faster hardware and smarter protocols still need to be developed for efficient communication. Lastly, we do not recommend that every radiology department or hospital implement its own PACS system in-house, as it does require substantial financial and manpower commitment. With clinical data of PACS generated by other research centers and our department, we hope the manufacturers will be able to adapt and use this information, and come up with turnkey PACS systems with specifications suitable for different hospitals or departments. In summary, we believe that the implementation of PACS in a radiology department or a hospital is inevitable. All the
DEPARTMENT
639
technology is available. The question concerning PACS implementation is not why, but when. With cooperation from the radiology community and the manufacturers, we believe PACS can be implemented successfully [9]. PACS will serve as a powerful tool for better health care delivery and for facilitating research and teaching.
REFERENCES 1 . Huang HK, Cho PS, Taira
communication
systems
AK, Ho BK, Chan in Japan-three
KK. Picture
years
later.
archiving AiR
and
1990;154:
415-417
2. Taira AK, Mankovich NJ, Boechat MI, Kangarloo H, Huang and implementation of a picture archiving and communication pediatric radiology. AJR 1988;150: 1117-1121 3. Cho PS, Huang HK, Tillisch J, Kangarloo radiologic picture archiving and communication unit. AiR 1988;151 :823-827 4. Huang HK. Experience in the use of PACS:
plans. In: Tsujiuchi J. PACShandbook
HK. Design system for
H. Clinical evaluation of a system for a coronary care present
problems
and future
‘89. Tokyo: Japanese PACS Society,
1989: 33-43 5. Templeton AW, Cox GG, Dwyer SJ III. Digit& image management networks: current status. Radiology 1988;169: 193-199 6. Chu WW. Performance of the file directory system for data bases in star and distributed network. AFIPS Coot Proc 1976;45:3-13 7. Aatib 0. Image file structure and data communication format, IPL Note
23.01 Los Angeles: UCLA, 1988 .
8. 9.
AcR-NEMA digital imaging and communication standard, 85. Washington, D.C.: NEMA, 1985 Meznch AS. The imp1ation of PACS for radiology 1988;151 :828
Publication
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AiR
