Development of an integrated radiotherapy network system

Int. J. Radiation

Biol.

Phys., Vol. 34. No. 5. pp. 110% Ii I I, 1996 Copyright 0 1996 Elsevier Science Inc. Printed in the USA. All rights reserved 0360.3016/96 Sl5.00 + .OO

0360-3016( 95)02206-6

ELSEVIER

l

Oncology

Physics Original Contribution DEVELOPMENT

OF AN INTEGRATED

RADIOTHERAPY

NETWORK

SYSTEM

YASUSHI NAGATA, M.D., * KAORU OKAJIMA, M.D., * RUMI MURATA, M.D., * MICHIHIDE MITSUMORI, M.D., * TAKASHI MIZOWAKI, M.D., * MASASHI YAMAMOTO, M.D., * MASAHIRO HIRAOKA, M.D., * TAJLEHIRO NISHIDAI, PH.D., * MANABU NAKATA, R.T., * MITSUYUKI ABE, M.D., * KOICHIROU SUGAHARA, B.S.,’ HIDETAKA ARIMURA, M.S.,” MINORU HOSOBA, PH .D., * HIRAKU MORISAWA, M.S., * CHUDO KAZUSA, PH .D., $’ DAVID AI, M.S.” AND MASAKI KOKUBO *Department of Radiology, Kyoto University Hospital, Kyoto, Japan, ’ NEC Corporation, Tokyo, Japan, “Shimadzu Corporation, Kyoto, Japan, “Cyber-Nisty Corporation, Tokyo, Japan, nVarian Associates, Palo Alto, CA Purpose: To introduce the process of developing an integrated radiotherapy network. Methods and Materials: We developed a new radiotherapy treatment-planning system in 1987 that we named the Computed Tomography (CT) simulator. CT images were immediately transported to multiimage monitors and to a planning computer, and treatment planning could be performed with the patient lying on the CT couch. The results of planning were used to guide a laser projector, and radiation fields were projected onto the skin of the patient. Since 1991, an integrated radiotherapy network system has been developed, which consists of a picture archiving and communicating system (PACS), a radiotherapy information database, a CT simulator, and a linear accelerator with a multileaf collimator. Results: Clinical experience has been accumulated in more than 1,100 patients. Based on our 7 years of experience, we have modified several components of our original CT simulator and have developed a second generation CT simulator. A standard protocol has been developed for communication between the CT scanner, treatment planning computer, and radiotherapy apparatus using the Ethernet network. As a result, treatment planning data can be transported to the linear accelerator within 1 min after completion of treatment planning. Conclusion: This system enables us to make optimal use of CT information and to devise accurate threedimensional (3D) treatment-planning programs. Our network also allows for the performance of fully computer-controlled dynamic arc conformal therapy. Three dimensional treatment planning, Network,

PACS, Conformal

INTRODUCTION

therapy.

Computed tomography (CT) scanners were mainly developed for diagnostic use and, thus, were separate from treatment planning machines. However, CT is a very important and is useful modality for radiotherapy as well. Since 1987, we have developed a CT simulator that is dedicated to radiotherapy (6, 7, 9, 10). The CT simulator is defined here as a CT system that has the following functions: it performs rapid CT scanning in the treatment position, three-dimensional ( 3D) treatment planning, and field projection onto the patient’s skin for marking. Every component of the CT simulator has been modified and

updated, and the process of development is discussed in this article. Since 1991, we have been developing a network for transmitting text information and all types of images used in radiotherapy. This network is composed of a picture archiving and communicating system (PACS) , a radiotherapy information database, a CT simulator, and a linear accelerator. This system enables us to perform fully computerized conformal therapy, because it controls a multileaf collimator (MLC) based on the results of treatment planning with the CT simulator. The hardware and configuration of the network are also described in this article.

This work was presented at the International Congress on Radiation Oncology ‘93, June 21-25, 1993, Kyoto, Japan. Reprint requests to: Yasushi Nagata, M.D., Department of Radiology. Kyoto Univ. Hospital, Sakyo Kyoto 606-01 Japan.

aid for CancerResearchfrom the Japanese Ministry of Education (01480273 and 05857095). The authors gratefully acknowledgeMs. Peggy Evans for her secretarialassistance. Accepted for publication 2 November 1995.

Acknowled
work was supported

by a grant-in1105

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METHODS

Volume 34. Number 5, 1996

AND MATERIALS

Hardware and s$tware qf the CT simulator The current CT simulator (Fig. 1) consists of a CT scanner’ (Fig. 1a), two multiimage monitors (Fig. lb), a 3D treatment-planning computer’ (Fig. lc), and a laser beam field projector3 (Fig. la). The CT scanner has been modified for radiotherapy use. The CT couch is flat, the gantry has a diameter of 65 cm (wide enough for most Japanese patients), and the x-ray tube has a power of 2,000 KHU. Computed tomography data can be immediately transfered to the treatment-planning computer at a speed of 6 s per slice. The treatment results established at the planning computer can be transferred back and displayed on the multiimage CT monitors. Using two color, 20-inch, multiimage monitors, up to nine CT slices with target outlines can be viewed at the sametime. The radiation fields for multiple CT images can also be checked with beam indicators. Using a laser projector, the beam center and a radiation field of any shapeas long as 40 cm at the isocenter can be projected automatically over a radius of 190” onto a patient lying on the CT couch. The 3D radiotherapy treatment planning computer uses a fast dose calculation method (4). We have installed a practical 3D dose calculation program, which uses the modified equivalent tissue maximum ratio method (8). Digitally reconstructed radiographs (DRR) and other special 3D reconstructed images (sagittal and coronal images) with dose distribution curves can also be viewed on the 20-inch color monitors. The treatment-planning program has been modified to allow for the performance of dynamic conformal therapy, for instance, an arc therapy with dynamic MLC shape changes. In an arc plan, we can automatically establish the MLC field for every 2” of gantry movement based on the outline of the clinical target volume and the planning target volume. The network between the CT scanner and the treatment planning computer is a general purpose interface bus (GPIB). It is important to transfer CT images rapidly from the CT scanner to the planning computer. It is also important to rapidly transfer planning data from the computer to the laser projector on the CT scanner. With this network, the speed of data transfer is 200 mega bits per s. Treatment planning from CT scanning to the completion of field projection onto the patient can be carried out in 60 min while the patient remains on the CT couch. Configuration of the integrated radiotherapy network Network. Currently we are focused on developing an integrated radiotherapy network system. We have devised a preliminary system incorporating a PACS, a radiother-

’ CTS-20, Shimadzu Corp., Kyoto, Japan. ’ NEC-RTP, NEC Corp., Tokyo, Japan.

a

b

Fig. 1. The new CT simulator: (a) The scanningroom, CT

scanner,and laserfield projector. (b) The operatingroom, CT control system,andmulti-imagemonitors.(c) The 3D treatment planningcomputer.

3 CTS-20.

Shimadzu

Corp., Kyoto. Japan.

An

Fig. 2. Configuration

integrated radiotherapy network l Y. NAGATA et al.

of our new integrated

system.

apy information database,a CT simulator, and a radiotherapy machine with an MLC. Figure 2 shows the configuration of our system. To transfer the field outline and treatment parameters from the planning computer to the MLC and radiotherapy information database, a method of data communication among equipment from three companies was developed using Ethernet and the TCP/IP protocol. Information for the MLC from the treatment-planning computer is directly placed on the file server4, and through the network file system (NFS ) facility such information is immediately available to the MLC workstation. Other treatment parameters from the planning computer are transmitted via a gateway protocol with the help of a trigger workstation. A network incorporating an x-ray simulator is also under development. PACS. The PACS is an image filing system5originally developed for diagnostic use (3), which is equipped with four 20-inch monitors ( 1,024 X 1,024 pixel resolution), an image network, a film digitizer. and a 90 GB capacity optical disk (Fig. 3). The system has a large random access memory (RAM), which can be considered as a light box made of semiconductors. Any area of the RAM spacecan be displayed on the four 20-inch monitors with 1,024 x 1,024 resolution at an arbitrary magnification by a high-speed image processor (IP, 30 MFLOPS). A specially designed super high speedimage bus (QP bus) can transfer data from the RAM to the display memory of each monitor at the maximum rate of 160 mega bytes per s. The monitors can be used for diagnosis, treatment planning, and clinical conferencing. Any x-ray film can be digitized within 20 s by the digitizer. A 2,000 X 2,000 X 12 bit image from film digitizer can be sent to the PACS by a specially designed parallel interface within 8 s. The CT images are transferred from the CT scanner to the PACS through an opti’ RMS 2000, Varian Associates, Palo Alto, CA. 5 Shimadzu Artificial Intelligence PACS (SAIPACS madzu Corp., Kyoto, Japan.

), Shi-

Fig. 3. The PACS system for radiotherapy. Four 20-inch monitors (left), a film digitizer (center). and a 90 GR memory (right).

cal fiber network at the physical rate of 6 megabits per s. All CT images are stored on the RAM disk ( 1.2 GB) and later on the optical disk (90 GB ) . Radiotherapy information database. The radiotherapy databaseis also very important. All text information, including patient data and treatment data, are stored in the network computer. Our database computer is a workstation6 with a 24 MB memory, 18 MIPS, 2.3 MFLOPS. Currently, all patient data, including tumor stage, histology, and past history, are stored in this computer. At present, the CT scarier storespatient data, CT image data, and field projecfion data, while the treatment-planning computer stores patient data, CT image data, and treatment-planning data. The treatment machine stores patient data, and treatment data, while the PACS storesradiotherapy image data and CT image data. Thus, the database is currently dispersed among various computers. Multileaf collimator. The MLC’ consists of 26 pairs of opposing leaves positioned directly below the standard adjustable collimators ( 1) . Each of the 52 leaves is driven individually under computer control and its position is confirmed by a redundant read-out mechanism. The leaves travel in a plane perpendicular to the central axis and are 10 mm wide at the isocenter. They can travel 16 cm beyond the central axis and can be used to shape a 40 cm treatment field in the direction of leaf motion. The 26 pairs of leaves provide a maximum treatment field of 26 X 40 cm. The field shape can be changed for every 2” of gantry movement and the maximum speed is 20 mm/s. The MLC workstation can accessthe file server, where MLC conformation data from the planning system are stored. 6 S-P302-GCY, Sumitomo Electronics, Tokyo. Japan. 7 CLINAC 2100 C/D, Varian Associates, Palo Alto. CA.

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Table 1. Comparison between CT simulators Original Established

CT Simulator (1987)

CTS-10

(1989)

New CT Simuiator

(CTS-20) (1993)

CT scanner scanning time detectors x-ray tube Image processor

CPU Matrix

Laser-beamfield projector Method

4.5 s 512 channels 1500 KHU

3.0 s 5 14 channels 1500KHU

2.0 5 8 12channels 2000 KHU

16 bits 340 x 340

16 bits

32 bits

340 x 340

512 x 512

Rasterscan

Liquid crystal

Liquid

300 x 300

375 x 375 2mrn

crystal

Matrix Accuracy

3mm

375 x 375 1 mm

KHU = Kilo Heat Unit Radiotherupy machine. The linear accelerator’ is capable of setting up and delivering a sequence of fixed fields under computer control. It can deliver dual photon energy (6 MV and 1.5 MV) and also has a dynamic wedge function. Treatment parameters that can be set under computer control include the gantry angle, collimator angle, couch position (longitudinal, lateral, vertical, and angle of rotation) , beam energy, wedge (open, 15”, 30”, 45”)) collimator leaf position, beam type, dose, and dose rate. All these parametersare transmitted on line from the planning system to the radiotherapy machine through the file server. The protocol was written to establish a two-way communication between the planning computer and the treatment machine with the MLC. The treatment machine and MLC were regulated cooperatively to establish a dynamic arc therapy.

RESULTS Development of the CT simulator system The original CT simulator was developed in 1987 and was in clinical use at Kyoto University and Hokkaido University in Japan. In 1988, a voice-gated intermittent irradiation system9for a linear accelerator was developed at Kyoto University. In 1989, a dose-volume histogram program was developed, and a new calculation algorithm for digitally reconstructed radiographs (DRR) was installed. In 1990, a new liquid crystal laser field projector was installed in the CT simulator. In 1991, the network between the CT simulator and the PACS was developed, and the treatment-planning computer was changed to a second-generationcomputer.” In 1993, a new CT scanner (CTS-20) and the latest computer *’ were installed. Some

* CLINAC 2100 C/D, Varian Associates,Palo Alto, CA. ’ This system was developed in cooperation Electronics Co.. Tokyo, Japan.

with Mitsubishi

portions of the treatment-planning program were developed at the Aichi Cancer Center in Nagoya, Japan, headed by Kozo Morita, M.D. The network connecting the MLC and linear accelerator to the planning computer was developed. Thus, the major components of the original CT simulator have been completely replaced. The development process for the CT scanner and laser projector is outlined in Table 1. High-resolution CT images are obtained with the CTS-20, the unit has a capacity of 2,000 KHU and can scan a single slice within 2 s. The multiimage monitors were changed to colored ones that allow up to nine CT slices with target outlines superimposed on dose distributions to be displayed simultaneously. The laser beam field projector can accurately project a radiation field onto the skin of the patient. It is attached to a C-shaped arm, and the accuracy of movement of this arm is also important. After the power of the motors that rotate the projector was increased, the accuracy improved from 3 to 1 mm. The development processfor the computers is outlined in Table 2. The new computer” is an advanced computer with a high calculating speed of 95 MIPS and 17.6 MFLOPS as well as 48 MB memory. Using the new computer, 3D radiation scatter can be calculated, as shown in the table. Compared with our previous system, the time from the beginning of CT scanningto the end of treatment planning has been shortened and data transfer errors have shown a marked decrease. Fully computer-controlled dynamic arc conformal therapy A new treatment-planning program for dynamic arc conformal therapy has been developed. The user simply

loEWS 4800/60, NEC Corp., Tokyo, Japan. ” EWS 4800/350,

NEC Corp., Tokyo, Japan.

An

integrated radiotherapy network 0 Y. NAGATA et ~1.

Table 2. Comparisonbetweenplanning computers Original CT simulator (CT-THERAC) CPU Memory Hard disk Precisionin floating Point data Data transferfrom CT Speed Image Matrix Display Monitor size Display matrix Calculationspeed

New CT simulator (EWS480l 350)

64 KB 40 MB 20 bits

48 MB 852 MB 32 bits

30 s/l CT slice 340 x 340

6 s/l CT slice 512 x 512

14 inch 512 x 512

20 inch 1280 x 1024

40 s/slice

3.1 s/slice

(151 s/slice)*

43 s/slice

Tissue peak ratio

(TPR) method Single portal Multileaf conformal Equivalent-tissue maximumratio (TMR) method Single portal Multileaf conformal Display speed

I109

CT slices, beam’s eye view (BEV) calculation, calculation of the position of each leaf of the MLC, 3D dose calculation, and field projection onto the patient. Data transfer from the CT simulator to the treatment apparatus can be complete within 1 min, while the previous manual method took 1 h. Conformal treatment can be finished within 15 min, including patient setup. Therefore, from the beginning of CT scanning to the end of treatment, it takes only 45-75 min. The time is 5-10 min for patient setup, lo-15 min for CT scanning, lo-15 min for target and organs at risk drawing, lo- 15 min for treatment planning, 5- 10 min for field projection, 1 min for data transfer, and 5 - 15 min for conformal treatment. Previously, it took more than 240 min to plan such therapy. With the development of our local area network, conformal therapy can be planned as a routine treatment, and it is currently used to treat head and neck cancer, prostate cancer, and pancreatic cancer.

DISCUSSION 90 s/slice

45 s/slice

(1051 s)* 33 s/slice

609 s 0.5 s/slice

Becausethe multileaf conformalcalculationcapability is not supportedfor CT-THERAC, the valuesenclosedby the asterisk (*) show the calculation speedwhen the rectangular field is rotated 90 degrees. outlines the clinical target volume and the safety margin for setup error, after which the computer immediately calculates the most appropriate position of each leaf of the MLC for every 2” of gantry movement ( 180 portals). With the development of the network, the radiotherapy plan established by the treatment computer can be transported within 1 min to the treatment machine, thereby allowing fully computer-controlled conformal therapy to be performed. Such a system allows us to save a great deal of time in planning dynamic conformal therapy, in which patients receive continuous radiation with dynamic changes of the MLC shapeduring an arc. The data established by the treatment planning computer include the gantry angle, collimator angle, couch position (longitudinal, lateral, vertical, and angle), beam energy, wedge (open, 15”, 30”, 45”)) collimator leaf position, beam type, dose, and dose rate. Data are transferred to the MLC and treatment machine through an Ethernet network using the TCP/IP protocol. The time required for conformal radiotherapy can be divided into three major parts. One is that taken up by treatment planning including CT scanning, another is the time for data transfer from the planning computer to the treatment apparatus, and the third is the time needed for the radiotherapy itself. With our system, CT simulation can be completed within 60 min including as many as 30

Clinical experience hasbeen accumulated in more than I, 100 patients (2, 8). The problems with the original CT simulator system have been solved over the past 7 years. The CT data and field data are transferred between the CT scanner and the treatment-planning computer. With our primary CT simulator, errors in data tranfer were not rare. For our new system, however, we have established a precise protocol for data transfer between the CT scanner and the planning computer, and have developed an excellent communication network. The time from CT scanning to the end of treatment planning has also been shortened. To achieve this purpose, we used a new CT scanner with short scanning time and a new treatment planning computer with rapid calculation capability. We also used a GP-IB protocol for rapid data communication and simplified the data transfer procedure. Compared with other CT simulator systems, our distinguishing feature is the laser beam field projector attached

Fig. 4. CombinedCT and x-ray simulatorwith a singlecouch.

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to a C-shaped arm ( 1 I, 12). Ragan questioned the accuracy of the movement of this arm ( 12). However, the accuracy of the projector was mechanically maintained within 1 mm. Moreover, the field shape projected onto the skin of the patients instantly showes us the shape of the target and oragans at risk. Sometimes, the involuntary movement or respiration of the patient during CT scanning makes a large geographic error. Projection of isocenters, field shape, and shape of organs at risk shows us such geographic discord. With our system, it can be instantly corrected in the CT simulator room. Other systems with only projection of field isocenters may evoke a large geographic error. The accuracy of tangential beams especially are questionable. The number of CT simulator systemsl* in Japan is on the increase and the system is now available at 29 institutes. We believe that this CT simulator is the most practical treatment-planning system currently available. A system that combines two different simulators, with an xray simulator and a CT simulator sharing the same couch, is another option” (Fig. 4). This allows for patient setup by using the x-ray simulator and taking an x-ray verification film after CT simulation, thus compensating for the weak points of the CT simulator. Also, while an x-ray simulator is useful for overall planning in the treatment planning of regional lymph node irradiation, obtaining a few CT slices with dose distribution curves by using a CT simulator can be very helpful. Such a system may be ideal for small hospitals where both CT and x-ray simulators cannot be installed due to limited space. Our network was established by the following procedures. One was the standardization of the data transfer protocol. Through the Ethernet network, the TCP/IP protocol could be used as a common interface between different machines produced by different companies. The treatment planning part of the CT simulator and the radiotherapy machine were connected on line through the Ethernet. All data, including that for the regulation of MLC position, gantry rotation, and dose rate, could thus be transferred together to the linear accerelator with a MLC. to

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perform fully computer-controlled conformal dynamic arc therapy. One of the serious problems with our previous CT simulator was that all the interfaces of the network had to be redeveloped when any component was upgraded. However, adoption of the standard data transfer protocol has minimized the changes necessary when a component is exchanged for a new machine. Previously we tried to store all image data in the PACS and all text information in the radiotherapy information database.All the image data could be successfully stored in the PACS, but the text information exceeded the capacity of the database. Therefore. we adopted a distributed databaseinto the present system. Patient details are stored in the radiotherapy information database,projection data in the CT scanner, treatment-planning results in the planning computer, and treatment data in the radiotherapy machine. This distributed database functions effectively in our department. Conformal radiotherapy has been reported to be effective in treating prostate and nasopharyngeal cancer (5 ) The dose distribution achieved with this technique is superior to that obtained with conventional treatment techniques. Previously, most 3D treatment planning systems have been developed separately from the radiotherapy machine, and the conformal treatment machines were designed separately from the new treatment planning systems. With the CT simulator. we combined a CT scanner and a treatment planning computer. With our integrated network, we then combined the treatment planning computer with a radiotherapy machine. Streamlining the two systems on line has shortened the time required for all procedures and decreased the frequency of errors. Our future goal is to combine multiple imaging modalities, (PACS, CT simulator, x-ray simulator, Magnetic Resonance Imaging (MRI), and a portal imaging device), and to devise a network for communication between the different treatment planning computers and treatment machines. In conclusion, our system is a practical 3D radiotherapy network that provides accurate treatment delivery with little operator assistance.

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applicationof equivalentTAR methodto fast reconsruction of three dimensionaldose distribution. Proc. 8th ICCR 456-460;

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5. Losasso,T.; Chui, C. S.; Kutcher, G. J.; Leibel, S. A.: Fuks, Z.; Ling, C. C. The useof a multileaf collimator for conformal radiotherapy of carcinomasof the prostateand nasopharynx. Int. J. Radiat. Oncol. Biol. Phys. 25:161170; 1993. 6. Nagata,Y.: Nishidai,T.; Abe, M.; Hiraoka, M.; Takahashi. M.; Fujiwara, K.; Okajima, K. Laserprojection systemfor radiotherapyandCT-guidedbiopsy. J. Comput.Assist.Tomogr. 14:1046-1048; 1990. 7. Nagata,Y.; Nishidai,T.; Abe, M.; Takahashi,M.; Okajima, ” CTS-specialoption, ShimadzuCorp., Kyoto, Japan.

An integrated radiotherapy network 0 Y. NAGATA et ul. K.; Yamaoka, N.; Ishihara, H.; Kubo, Y.; Ohta, H.; Kazusa, C. CT simulator: A new 3D treatment planning and simulating system for radiotherapy. Part 2. Clinical application. Int. J. Radiat. Oncol. Biol. Phys. 18505-513; 1990. 8. Nagata, Y.; Okajima, K.; Murata, R.; Mitsumori, M.; Mizowaki, N.; Tsutsui, K.; Ono, K.; Nisimura, Y.; Hiraoka, M.; Nishidai, T.; Takahashi, M.; Abe, M. Three dimensional treatment planning for maxillary cancer using a CT simulator. Int. J. Radiat. Oncol. Biol. Phys. 30:979-983; 1994. 9. Nakata, M.; Nishidai, T.; Nohara, H.; Okada, T.; Nagata, Y.; Abe, M. New 3-D dose calculation using modified equivalent tissue-maximum ratio method: Dose computation along the off-central axis. Jpn. J. Radiol. Technol. 10:23-34; 1992.

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