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Do we need a computer?
Clin. RadioL (1974) 25, 19-25
DO WE NEED A COMPUTER? A REVIEW OF D A T A PROCESSING APPLICATIONS IN NUCLEAR MEDICINE AND RADIOTHERAPY
D. N. EDWARDS From the Liverpool Regional Radiotherapy Centre
A policy for the use of computers has been suggested by the Department of Health. Guidance in the application of this policy must come from clinicians, based upon informed opinion. A brief review of the current situation and of development work is presented in the belief that the majority of clinicians are unaware of the potential influence of the computer on nuclear medicine and radiotherapy.
IY 1972 the Department of Health published a document entitled 'Using Computers to Improve Health Services' which is a review of the current situation and a proposal for a policy in this field. It contains recommendations about the use of the computer in radiotherapy, radio-diagnosis, cancer registries etc., but very little comment is made about nuclear medicine. Clinicians will be asked to co-operate with other disciplines in implementing this policy. Undoubtedly modifications will be necessary and it is important that these should be based upon informed opinion. Yet many clinicians are unaware of this document and of the recent work in this field. The purpose of this paper is to present a brief review of the use of the computer in radiotherapy and nuclear medicine. A notable feature in this field has been the very free exchange of ideas between workers in this country and abroad, facilitated by the biennial international conference on computers in radiotherapy and by special symposia such as that in Brussels in 1969. It is upon the opinions expressed at such meetings, the informal discussions and visits to workers elsewhere and upon personal experience in the Liverpool Centre that the author's comments are based. Most of the hard work of experimentation with the computer has been done by hospital physicists working either in radiotherapy departments or in nuclear medicine units. In 1971 some of them realised that with the recent advances in technology, it would be possible to introduce into radiotherapy
planning as a routine the developments that previously were considered to be research. Whether or not the introduction of these developments would improve the quality of the care of the patient is one of the reasons for asking the question 'do we need a computer?' They did realise that any judgement must be solidly based on information. Therefore the Hospital Physicists' Association and the British Institute of Radiology jointly set up a working party. The need for this survey of past work and current trends was recognised by the Department of Health by the provision of financial help to the working party to commission for a short period the services of a consultant in computer technology. NUCLEAR MEDICINE In this speciality computation plays a vital part in the correct interpretation of the distribution and activity of the isotope. In the past, an allowance for the physical half-life of radionuclide, background activity, counter dead-time, biological half-life and for the statistical laws that show, for example, that errors can be introduced due to insufficient total counts, have been made with paper and pencil, a slide rule or an electric calculating machine. Twenty years ago the work-load of a radio-isotope unit consisted of simple methods of static in vivo or in vitro counting. Crude rectilinear scanning was introduced and experiments were started with simple dynamic in vivo counting. Then the gamma camera allowed the development of dynamic studies on a routine basis. At the same time the first small computer systems became available and during the past decade tentative experiments have been performed to explore the potential of the gamma camera linked
Based on a paper defivered to the Therapy Section, Faculty of Radiologists at the Spring meeting in Liverpool, 10thMarch, 1973. 19
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CLINICAL R A D I O L O G Y
to a data storage and processing system, but only for other similar errors may disappear with the recently have data processing techniques been used routine production of the third generation gamma to any extent. Perhaps this reflects not only the cameras. relative smallness of nuclear medicine units comThe use of double isotope techniques for subpared with other potential users of computers but traction studies is apparently feasible with an also the lack of the ideal processing system for electronics 'black box' but data processing with nuclear medicine - the small dedicated computer - a computer is probably more rapid. Perhaps the which has not been available economically until main advantage of the use of the computer for recently. 'static' displays will prove to be the rapidity of The work of a nuclear medicine unit can be processing. The average department of nuclear divided into studies which are in vivo or in vitro. medicine today provides a service function similar In Vivo. - A further division can be made into to that of diagnostic radiology. Already reporting either static studies or dynamic studies (fast or is sometimes unable to keep up with the throughput. slow). Two types of equipment are available for Any method which is capable of providing a perthese studies, i.e. the rectilinear scanner and the manent record of the test, either as a tabulation gamma camera. Each has advantages and dis- or as a picture together with the report and the advantages relevant to the type of study and to the diagnosis, which can then accompany the patient as presentation of the result of the test. he leaves the department, should be encouraged. The raw data, whatever the technique, are the It is probable that this can be done only with the counts. The original concept was to convert the aid of computer techniques. This could be the real detected count rate to a symbol printed on paper justification for their use. or on film, so that an image of the distribution of For 'dynamic' studies the rate and quantity of radio-activity was built up sequentially. This two- data acquisition may be so great that a computer dimensional image was the sole record of the system is required. However, many investigations investigation available subsequently. This method can be conducted using simple storage media such of working imposed a severe limitation on further as film, punched tape or magnetic tape. Again the processing of the acquired data. In order to allow critical factor would appear to be time. What is an subsequent manipulation of the raw data it was acceptable interval between the acquisition of data, realised that a storage medium was required which making deductions, and reaching a diagnosis? could be either paper tape or magnetic tape. From There is little doubt that the use of the computer the stored data it would then be possible to present does shorten the overall time. Another factor to be considered when assessing the basic information in any way which would improve the diagnostic process that was used by the the function of a computer in a department of clinician. This manipulation could be done with nuclear medicine is the work load. The average fairly simple electronic methods, but of course the annual increase in tests performed is 30 ~ . With limited trained staff available computer technology digital computer system has advantages. Recently much work has been done with com- may be the only method of maintaining a service puter programmes to produce isocount contours. to meet this rapid increase, yet at the moment the An alternative is the profile contour, a number of proportion of patients in whom a radionuclide which together can be used to produce an isometric study will contribute to the diagnosis is very small. display which can then be apparently rotated To what extent should the limited resources to 'view behind the hill'. The effect of smoothing available to us be devoted to this small group of can be shown and also the effect of filtering. patients? Within nuclear medicine, the computer can be Sophisticated statistical techniques can be applied to enhance the significant abnormalities. Colour used with benefit to activities not concerned displays have been used for some years for dot directly with the patient. The program used can scans, and a similar use of colour has been applied be considered as 'administrative' in type, derived from standard commercial software. For example, to displays upon the oscilloscope. It is alleged that the use of these sophisticated departments inevitably will be using several isocomputer techniques has helped very little in the topes, each of which has a different physical halfDependent upon the throughput of the process of reaching a diagnosis and that the rate of life. false deductions is no less than that obtained by department, a stock of the more frequently used simpler methods. Even the argument that the com- isotopes will have to be kept and replenished at puter can be programmed to correct for the more or less frequent intervals. The quantity non-uniformity inherent in the gamma camera and required will depend on a number of variables such
DO WE NEED A COMP UT E R~
as the physical half-life, the time taken for transport from origin to unit, the frequency of use, etc. Data processing technology can be used to maintain a 'stock record' and to warn the department when a fresh replacement is required and a similar programme can be used for arranging appointments for tests. The nuclear medicine department, in common with other departments concerned with the investigation or treatment of patients, keeps accurate records of patients together with the results of the tests performed. These must be indexed and easily accessible. The advantage of a computer-based filing system has been demonstrated in other spheres, but for this field it is likely that the access time will have to be within hours rather than a day or two. In Vitro. - Data processing with a computer would appear to give no specific advantages. However, if a computer is used for other types of studies then administratively it may be convenient for 'in vitro' work to be brought into the general system. To summarise the present position the consultant in nuclear medicine is faced now with pressure salesmanship from manufacturers who are promoting complete systems for the nuclear medicine department. There is little doubt that such systems offer a definite reduction in the time required to see the effect upon the basic data of such manipulations as smoothing or changing contrast. It is probable that for dynamic studies there is a real need for computer technology. However, some workers doubt whether dynamic studies give information not otherwise obtainable. If thisis true, can the cost of the computer application be justified? In static studies considerable effort has been expended in computer techniques which will process the basic raw data to give alternative displays. Again there is argument about whether such displays really help the clinician in interpreting the information obtained during the isotope study. RADIOTHERAPY Almost twenty years ago megavoltage treatment units became available for routine use. This quality of radiation did not deposit more energy in calcified tissues than in soft tissues, as lower energies had done. Thus the clinician was given greater freedom in planning the position of external beams. The shielding effect of bone was no longer a hazard that had to be considered in placing fields as it had been with lower energies. In addition the increased output of the megavoltage generators allowed the use of increased focus-skin distances and this enhanced further the dose at depth.
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A resurgence of interest in the effects of radiation at macroscopic and microscopic level was generated by the availability of these megavoltage machines. Some clinicians became part-time radiobiologists and the number of research workers interested in radiobiology increased. Thus it was necessary and was now practical to establish a unit of absorbed radiation, the rad. Clinicians developed an interest in relating the early and late reactions seen in patients to the level of absorbed dose. This required art accurate estimation of the dose distribution. It is true that this had been possible using techniques pioneered by Parker (1934), Mayneord (1939), Howard Flanders (1943) and many others, but these were time consuming and available to only a few clinicians. The burden of calculating the distribution of dose in the patient fell upon the physics department of most radiotherapy centres, although a few clinicians still felt that they were capable and also had the time to do it. It was natural therefore, with the increased interest in the distribution of absorbed dose, for radiation physicists to look for methods of reducing the time consumed in calculation while maintaining or improving accuracy. At this time, in the early 1950% digital computers were becoming available in universitites and in the biggest commercial organisations. Physicists such as Tsien (1955) in New York and Woods (1962) in this country started projects concerned with the application of computer technology to dose computation. In the early 1960's the potential of the computer was being recognised and some radiotherapists attended courses offered by the manufacturers which were intended to give a general background only, and of interest mainly in the application of electronic data processing to clinical records and the statistical evaluation of treatment regimes. At this time a tentative policy was being developed in the Department of Health concerning the use of computers in the Health Services. The manufacturers were at the same time realising that the introduction of the maxi-computer often created more problems than could be solved technically, and that there was a growing market for the mini-computer in commerce and the microcomputer in the armed services. One of the mini-computers was used to develop a system to provide radiation physicists or radiotherapists with a rapid, flexible, on-the-spot computation service for external beam dose distribution. This work took place in St. Louis and the mark of the British School of Radiotherapy Physics was stamped on this project by the active
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CLINICAL RADIOLOGY
contribution of Clifton and Bentley (Holmes, 1970). The Programmed Console was the pioneer effort that has led to the concept of the dedicated computer in the radiotherapy centre, fostered by the Physics Department at the Royal Marsden Hospital. It is marketed as the ' R a d 8' system by one manufacturer and a similar concept is the 'PC-12' system. In parallel to the experiment with the concept of the 'dedicated computer' an alternative method has been developed at University College Hospital, the Middlesex Hospital and elsewhere. This uses a maxi-computer, so designed that it can work through many interfaces at effectively the same time. Any interface can be remote from the computer, with communication maintained by means of cables, the telephone exchange, the telex system or even by satellite. For the user at the peripheral terminal the computer would appear to be working for him alone, responding within seconds to the given instructions. Alternatively, if there is no need for this apparent dedication of the computer to a task immediately, then real-time working can be changed for delayed working, which costs less. Then the instructions which have been entered will be obeyed when the system is not working to capacity. However although this may be within the next few minutes, it may be several hours before the task can be completed by the computer. The third concept believes that a limited delay is acceptable. Basic information is sent by post or messenger to a distant computer system where it is processed. The result of the computation, usually printout on paper, is returned by the same method. F o r this method an interval of up to 24 hours is usually accepted (Hope, 1965). The choice of one of these concepts will be determined usually by local circumstances and available money. The technique of loading the system with the basic data, the physics underlying the method of computation and the physical format in which the result is presented exist as several alternatives and are available to any of the systems used by each of these concepts. Thus input is commonly either by teletypewriter, punched paper tape, punched cards or an analogue - to - digital device. There are at least five different methods of using radiation physics to compute the dose distribution from external beams. Some of these methods sacrifice accuracy for speed. -The result can appear on paper from the teletypewriter, the line printer, the incremental plotter, or on a large television or small storage screen. The format can be numbers, either a full matrix or selected in a particular way; as isodose curves; or as a grey scale
distribution. The 'scope display can be monochrome or coloured. RADIATION DOSE COMPUTATION This computation is usually for the co-axial plane but there are programmes that produce the distribution in any plane (Van de Geijn, 1965). Although as far as is known no radiotherapy centre in this country routinely uses such a programme for external beam calculation, several centres abroad assert that they would not be without this facility and have come to depend upon it for the competent planning of treatment, especially around the head and neck, (Kok (1971), personal communication). The computer has been used also to calculate the dose distribution from intracavitary and interstitial sealed radionuclides. Two main types of programme are used. F r o m one, a tabulation of dose rates is produced for selected points. F r o m the other, isodose rate curves or a full matrix of dose rates is produced. As with external beam programmes the output medium will depend on the computer configuration. Of the several parameters needed for calculation of dose or dose-rate those concerned with the patient are the least accurate. The skin outline, or tissue-air interface, in the body cross-section of interest has always proved difficult to translate for input. This was realised before the use of computers but even so most clinicians appear to be content with the inaccurate outline produced by a lead strip. Methods of producing an accurate contour are available but not in routine use. They may be optical (Clayton and Thompson 1970) or mechanical, or use x-rays or laser beams. This apparent lack of interest in accuracy may be due to the assumption that the physical data for absorption of radiation are of greater inaccuracy. But this is no longer true. N o r is it true that allowance cannot be made for tissue inhomogeneity. The most recent R.D.C. programmes allow computation for any area of inhomogeneity and any factor may be inserted uniquely for that area to modify the absorbed dose. Thus it is now the responsibility of the clinician to determine the position within the body cross-section of these areas. This can be done, of course, with tomograms. Trans-axial tomograms (T.A.T.S.) will give in addition an accurate tissue-air interface. The situation now exists by which a dose computation can be produced in about a minute on a visual display unit (V.D.U.) or between five and
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A COMPUTER?
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ten minutes on a plotter or line printer. It is more distribution is to confirm the position of the beams accurate than when done manually and the process on the patient using the simulator. Some current will be repeated without fatigue. It is true that a models use image intensification systems that prophysicist in training could and should do the same duce a display on a television screen remotely. work and, as salaries stand at the moment, probably Therefore controls are motorised and it does not at less cost. With increasing shortage of staff in take much imagination to realise that a digital hospitals is this the correct use of physicists? And read-out of each parameter at the console would how many physicists will prepare routinely alter- be useful. Taken a step further, at the completion native dose distributions so that the best position of of the simulation, the final readings of the parathe field can be determined? The selection from meters should be printed out. The real indication several beam positions of that which gives the best for doing this is to prevent inaccuracy in reading distribution - and another paper would be required linear or angular scales, a subject in its own right to consider the parameters of the 'best' distribution which will be discussed briefly below. - involves the concept of individualisation of At the Institut Gustave-Roussy work is in treatment planning. By this is meant the fitting of progress in this field. There are twelve variates beams to the patient, rather than the alternative, possible on a treatment machine or simulator. It that of fitting the patient into a standard beam has been estimated that for any one treatment configuration of known dose distribution. For machine during any one year the radiographer will this method of planning treatment, an 'atlas' has have to set accurately 80,000 readings. Not only been proposed which has been prepared with is this time consuming but there is the possibility of computer aid. It is believed that such an atlas to error. be useful must contain several hundred distriBomford (1970) pointed out the variation in the butions in order to match accurately the changing method of scaling on treatment machines. Unless parameters of body cross-section, which are the necessary changes have been made by the dependent upon sex, anatomical level and patient physicist, most radiotherapy departments will be size; of the target volume, which will be related to using treatment machines and simulators upon whether or not lymph drainage is to be included; which the rotational and linear scales of some of and of the position of critical organs. these movements will differ from one machine to the The argument for this concept is that of cheap- other. A working party at the recent conference in ness and speed. The reduction in the cost of one Uppsala studied this problem and has made recomaspect of treatment would allow more money to mendations, which it is believed manufacturers be spent on another. However, the facility of will adopt. The construction of programmes to calculating accurately the dose distribution for the monitor treatment parameters or to link simulator individual patient must not be lightly discarded. and treatment machines has focussed attention There is no doubt that the dose distribution from upon the need for an accepted standard for scales. external beams, from interstitial radio-nuclides or The logical development beyond a simple printintracavitary sources can be adequatelycalculated by out of the parameters obtained during planning on hand. But due to lack of time it is usual to restrict the simulator is to feed them back into the comthe calculation to a handful of point doses in one puter. The programme will then carry out a plane only, or isodose curves with values, for comparison with those used to produce the original example greater than 80 ~ of the target volume dose distribution, and if there are differences a new dose. It is not practicable to produce routinely the distribution will be calculated. distribution away from the coaxial plane, to calculate the effect of air-spaces, or to estimate the MONITORING. -- Comment has been made volume of tissue that is receiving, for example, already about the possibility of error, not only by less than 5 0 ~ of the target volume dose. Do the radiotherapist or physicist during his calculation we need the facilities of the computer to give this of the dose distribution, but also by the radioadditional information? And how should it be grapher in the translation from the prescription to presented - as a grid, as density gradients, as the parameters set on the machine. isodose curves with printed values or as curves for Recently manufacturers have motorised field-size which the value is determined by reference to a diaphragms and other variables. This has been table? done in order to preset treatment parameters so that the time of setting up the patient will be reduced. S I M U L A T O R S . -- The logical step in the planning As with the simulator it is logical to have a read-out process that follows calculation of the best overall mechanism.
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CLINICAL
So far those physicists and clinicians who have considered this development have been more interested in the facilities for monitoring that this allows rather than in any time-saving. Initially the read-out of parameters set is only a record of the conditions under which treatment has been given, which, it is always hoped, is the same as the treatment intended. It would be better for the patient if an error could be prevented. This could be done by comparing the read-out with a control. This could be achieved by punched cards or any other record and read-out medium. The difficulty arises in deciding the range of disagreement acceptable for each of the parameters. Work has already begun on this at Uppsala Hospital, the Royal Marsden Hospital, the Institut Gustave-Roussy and no doubt at other centres. During the next few years development will be taking place upon the linking - which is entirely logical - of the dose computation, the simulator and the treatment machine with a view to ensuring the accurate fulfilment of the planned course of treatment. The logical method of linking is through a computer exercising the function of calculating machine and process controller. A good principle of management is to obtain the best return for the chosen outlay of resources, a principle which in the N.H.S. is frequently debased to obtaining a service at the cheapest cost. The effect is that salaries of, for instance, radiographers, cannot compare with those for occupations otherwise available to the young girl, and fewer radiographers will be trained therefore in the future. In order to maintain good standards of patient care, less time will be available for such chores as manuscript recording of the treatment given. It is suggested that the computer will be needed in this sphere in order to allow these fewer radiographers to continue to devote time to reassuring the patient, maintaining the liaison between patient and radiotherapist, and helping the nursing staff. Further, used intelligently the computer can prevent the disasters which, due to the fallibility of the human, particularly if under pressure, have happened in the past. EVALUATION OF TREATMENT.-- We all, from time to time, fall into the trap of remembering the occasional patient who unexpectedly responded well to a particular form of therapy to the exclusion of the majority who did not. A person's outlook may also be biased by such factors in his clinical environment as degree of specialisation and individual experience, which may be grossly misleading as a
RADIOLOGY
basis for judgement. Realisation of the fact over the past decade has led to the present interest in clinical trials. Unfortunately a clinical trial is based firmly upon numbers. The larger the number of patients observed the smaller is the chance that the observations are fortuitous. Not all clinicians see enough patients to allow conduct of a clinical trial - and for some rare types of disease there will never be enough patients. However, much useful clinical information can be obtained by keeping good records and this has always been a feature of radiotherapy departments. Frequently however, access to the mass of information recorded in clinical records has been difficult, relying at the worst on the memory of names or registration numbers and at the best upon a card index or punch card system. Either method resulted in considerable effort to recover facts and often the quality and quantity of information was severely limited by the recording medium. Data processing using the computer, applied to clinical records of malignant disease, has been used in Liverpool since January 1970. The system has been described elsewhere (Edwards, 1972) but it is appropriate to review in the context of this paper the advantages and disadvantages of such a system. The disadvantages could be listed as :I) Computer not on site. Initially there are problems of liaison with the members of the computer centre team. 2) Batch processing operation. This is acceptable for input, but for output of analysis is a change from previous working. 3) Involvement of another unit. Some control of the process is relinquished to the computer centre staff. Significant advantages are :1) The quantity of data held is solely dependent on the system chosen. 2) The system acts, not only as a file, but also as a sorting mechanism, a calculating machine, and a printer or graph producer. 3) The system to a large extent becomes capable of automatically updating the information, e.g. calling for follow-up reports and sending out follow-up letters. The overall process of acquiring, processing and analysing information on malignancy is cheaper. The clinician who wishes to assess frequently whether the patients treated by him have benefited or not has the alternative of continuing with the
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D O WE N E E D A C O M P U T E R . 9
manual methods or o f using some f o r m o f electronic data processing. The small dedicated computer systems have recently included in their software packages a simple file-handling p r o g r a m m e orientated toward the clinician w h o alternatively can make arrangements to use the Regional Board's H.A.A. system, but this, for the moment, is very limited in its capabilities for storing clinical data. He can develop, with the co-operation o f the Board's computer centre staff, a dedicated programme for handling his clinical records, or he can encourage the regional cancer registry to include the information in which he is interested. If the registry is not based u p o n an E.D.P. system he can encourage interest in the use o f the computer for the case records. I n particular he can give expert advice on the data to be recorded for radiotherapy. This advice, it is to be hoped, would involve the inclusion o f the ' R e c o m m e n d e d List o f Variates' which is now finding acceptance, not only in this country, but also in Europe. CONCLUSION An outline has been given o f the present use o f the computer in nuclear medicine and radiotherapy with an indication o f probable trends for the near future. The Faculty, the British Institute o f Radiology and the Hospital Physicists' Association have different levels o f interest in the application o f computers. However, it is the clinicians responsible for the care o f patients who should determine the use to be made o f this new technology. 'Management' is the 'in' w o r d in the National Health Service today. This is a useful concept if the definition o f management is accepted as 'the best use o f available resources'. However, the tendency at the m o m e n t is for administrators to decide what is 'best' because the general b o d y o f clinicians do not appear to have the inclination or the time to do the h o m e w o r k and give advice based on the homework. At a recent meeting o f a committee concerned with computing it was shown that on average a dedicated computer might be used on R.D.C. w o r k for only 25 ~ o f the time, and deduced that R.D.C. on a dedicated c o m p u t e r was not cost-effective. This argument is spurious: m a n y items of equipment n o w regarded as essential to a radiotherapy
department - the simulator for example - are idle for over half the working time. To establish the most sensible and economic usage the opinions o f clinicians must be available, k n o w n to be available, and indeed proferred. It is hoped that this paper m a y stimulate clinicians in radiotherapeutics and nuclear medicine to evaluate the application of computers to their discipline.
Acknowledgements. --I wish to express my gratitude to the many radiotherapists and physicists in this country and abroad who have given freely of their time to discuss or demonstrate their concept of the application of the computer.
REFERENCES USING COMPUTERS TO IMPROVE HEALTH SERVICES (1972).
pub. Department of Health and Social Security reference 8488/908914. BENTLEY, R. E. t~, MILAN, J. (1971). An interactive digital computer system for radiotherapy treatment planning. British Journal of Radiology, 44, 826-833. BOMFORD,C. K. (1970). Letter to tile Editor "Do simulators simulate". British Journal of Radiology 43, 583. CLAYTON, C. B. • THOMPSON, D. J. (1973). An optical apparatus for reproducing surface outlines of body crosssections. British Journal of Radiology, 43, 489-492. EDWARDS,D. N. (1972). Clinical records and electronic data processing. Clinical radiology, 23, 117-216. FLANDERS,P. H. (1943). A dose contour finder for symmetrical and unsymmetrical radiation beams. British Journal of Radiology, 16, 314-316. HOLMES, W. F. (1970). External treatment planning with the Programmed Console. Radiology, 94, 391-400. HOPE, C. S. & ORR, J. S. (1965). Computer optimisation of 4MV treatment planning. Physics in Medicine & Biology, 10, 365-373. MAYNEORD, W. V. (1939). A dose contour projector and its application to three-dimensional radiation distributions. British Journal of Radiology, 12, 262-268. PATERSON,R. & PARKER,H. M. (1934). A dosage system for gamma ray therapy. British Journal of Radiology, 7, 592-632. TSlEN, K. C. (1955). The application of automatic computing machines to radiation treatment plamaing. British Journal of Radiology, 28, 432-439. VAN DE GE1JN,J. (1965). The computation of two and daree dimensional dose distributions in Cobalt 60 teletherapy. British Journal of Radiology, 38, 369-377. WOOD, R. G. (1962). The computation of dose distributions in Cobalt rotational therapy. British Journal of Radiology, 35, 482-484.
DO WE NEED A COMPUTER? A REVIEW OF D A T A PROCESSING APPLICATIONS IN NUCLEAR MEDICINE AND RADIOTHERAPY
D. N. EDWARDS From the Liverpool Regional Radiotherapy Centre
A policy for the use of computers has been suggested by the Department of Health. Guidance in the application of this policy must come from clinicians, based upon informed opinion. A brief review of the current situation and of development work is presented in the belief that the majority of clinicians are unaware of the potential influence of the computer on nuclear medicine and radiotherapy.
IY 1972 the Department of Health published a document entitled 'Using Computers to Improve Health Services' which is a review of the current situation and a proposal for a policy in this field. It contains recommendations about the use of the computer in radiotherapy, radio-diagnosis, cancer registries etc., but very little comment is made about nuclear medicine. Clinicians will be asked to co-operate with other disciplines in implementing this policy. Undoubtedly modifications will be necessary and it is important that these should be based upon informed opinion. Yet many clinicians are unaware of this document and of the recent work in this field. The purpose of this paper is to present a brief review of the use of the computer in radiotherapy and nuclear medicine. A notable feature in this field has been the very free exchange of ideas between workers in this country and abroad, facilitated by the biennial international conference on computers in radiotherapy and by special symposia such as that in Brussels in 1969. It is upon the opinions expressed at such meetings, the informal discussions and visits to workers elsewhere and upon personal experience in the Liverpool Centre that the author's comments are based. Most of the hard work of experimentation with the computer has been done by hospital physicists working either in radiotherapy departments or in nuclear medicine units. In 1971 some of them realised that with the recent advances in technology, it would be possible to introduce into radiotherapy
planning as a routine the developments that previously were considered to be research. Whether or not the introduction of these developments would improve the quality of the care of the patient is one of the reasons for asking the question 'do we need a computer?' They did realise that any judgement must be solidly based on information. Therefore the Hospital Physicists' Association and the British Institute of Radiology jointly set up a working party. The need for this survey of past work and current trends was recognised by the Department of Health by the provision of financial help to the working party to commission for a short period the services of a consultant in computer technology. NUCLEAR MEDICINE In this speciality computation plays a vital part in the correct interpretation of the distribution and activity of the isotope. In the past, an allowance for the physical half-life of radionuclide, background activity, counter dead-time, biological half-life and for the statistical laws that show, for example, that errors can be introduced due to insufficient total counts, have been made with paper and pencil, a slide rule or an electric calculating machine. Twenty years ago the work-load of a radio-isotope unit consisted of simple methods of static in vivo or in vitro counting. Crude rectilinear scanning was introduced and experiments were started with simple dynamic in vivo counting. Then the gamma camera allowed the development of dynamic studies on a routine basis. At the same time the first small computer systems became available and during the past decade tentative experiments have been performed to explore the potential of the gamma camera linked
Based on a paper defivered to the Therapy Section, Faculty of Radiologists at the Spring meeting in Liverpool, 10thMarch, 1973. 19
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to a data storage and processing system, but only for other similar errors may disappear with the recently have data processing techniques been used routine production of the third generation gamma to any extent. Perhaps this reflects not only the cameras. relative smallness of nuclear medicine units comThe use of double isotope techniques for subpared with other potential users of computers but traction studies is apparently feasible with an also the lack of the ideal processing system for electronics 'black box' but data processing with nuclear medicine - the small dedicated computer - a computer is probably more rapid. Perhaps the which has not been available economically until main advantage of the use of the computer for recently. 'static' displays will prove to be the rapidity of The work of a nuclear medicine unit can be processing. The average department of nuclear divided into studies which are in vivo or in vitro. medicine today provides a service function similar In Vivo. - A further division can be made into to that of diagnostic radiology. Already reporting either static studies or dynamic studies (fast or is sometimes unable to keep up with the throughput. slow). Two types of equipment are available for Any method which is capable of providing a perthese studies, i.e. the rectilinear scanner and the manent record of the test, either as a tabulation gamma camera. Each has advantages and dis- or as a picture together with the report and the advantages relevant to the type of study and to the diagnosis, which can then accompany the patient as presentation of the result of the test. he leaves the department, should be encouraged. The raw data, whatever the technique, are the It is probable that this can be done only with the counts. The original concept was to convert the aid of computer techniques. This could be the real detected count rate to a symbol printed on paper justification for their use. or on film, so that an image of the distribution of For 'dynamic' studies the rate and quantity of radio-activity was built up sequentially. This two- data acquisition may be so great that a computer dimensional image was the sole record of the system is required. However, many investigations investigation available subsequently. This method can be conducted using simple storage media such of working imposed a severe limitation on further as film, punched tape or magnetic tape. Again the processing of the acquired data. In order to allow critical factor would appear to be time. What is an subsequent manipulation of the raw data it was acceptable interval between the acquisition of data, realised that a storage medium was required which making deductions, and reaching a diagnosis? could be either paper tape or magnetic tape. From There is little doubt that the use of the computer the stored data it would then be possible to present does shorten the overall time. Another factor to be considered when assessing the basic information in any way which would improve the diagnostic process that was used by the the function of a computer in a department of clinician. This manipulation could be done with nuclear medicine is the work load. The average fairly simple electronic methods, but of course the annual increase in tests performed is 30 ~ . With limited trained staff available computer technology digital computer system has advantages. Recently much work has been done with com- may be the only method of maintaining a service puter programmes to produce isocount contours. to meet this rapid increase, yet at the moment the An alternative is the profile contour, a number of proportion of patients in whom a radionuclide which together can be used to produce an isometric study will contribute to the diagnosis is very small. display which can then be apparently rotated To what extent should the limited resources to 'view behind the hill'. The effect of smoothing available to us be devoted to this small group of can be shown and also the effect of filtering. patients? Within nuclear medicine, the computer can be Sophisticated statistical techniques can be applied to enhance the significant abnormalities. Colour used with benefit to activities not concerned displays have been used for some years for dot directly with the patient. The program used can scans, and a similar use of colour has been applied be considered as 'administrative' in type, derived from standard commercial software. For example, to displays upon the oscilloscope. It is alleged that the use of these sophisticated departments inevitably will be using several isocomputer techniques has helped very little in the topes, each of which has a different physical halfDependent upon the throughput of the process of reaching a diagnosis and that the rate of life. false deductions is no less than that obtained by department, a stock of the more frequently used simpler methods. Even the argument that the com- isotopes will have to be kept and replenished at puter can be programmed to correct for the more or less frequent intervals. The quantity non-uniformity inherent in the gamma camera and required will depend on a number of variables such
DO WE NEED A COMP UT E R~
as the physical half-life, the time taken for transport from origin to unit, the frequency of use, etc. Data processing technology can be used to maintain a 'stock record' and to warn the department when a fresh replacement is required and a similar programme can be used for arranging appointments for tests. The nuclear medicine department, in common with other departments concerned with the investigation or treatment of patients, keeps accurate records of patients together with the results of the tests performed. These must be indexed and easily accessible. The advantage of a computer-based filing system has been demonstrated in other spheres, but for this field it is likely that the access time will have to be within hours rather than a day or two. In Vitro. - Data processing with a computer would appear to give no specific advantages. However, if a computer is used for other types of studies then administratively it may be convenient for 'in vitro' work to be brought into the general system. To summarise the present position the consultant in nuclear medicine is faced now with pressure salesmanship from manufacturers who are promoting complete systems for the nuclear medicine department. There is little doubt that such systems offer a definite reduction in the time required to see the effect upon the basic data of such manipulations as smoothing or changing contrast. It is probable that for dynamic studies there is a real need for computer technology. However, some workers doubt whether dynamic studies give information not otherwise obtainable. If thisis true, can the cost of the computer application be justified? In static studies considerable effort has been expended in computer techniques which will process the basic raw data to give alternative displays. Again there is argument about whether such displays really help the clinician in interpreting the information obtained during the isotope study. RADIOTHERAPY Almost twenty years ago megavoltage treatment units became available for routine use. This quality of radiation did not deposit more energy in calcified tissues than in soft tissues, as lower energies had done. Thus the clinician was given greater freedom in planning the position of external beams. The shielding effect of bone was no longer a hazard that had to be considered in placing fields as it had been with lower energies. In addition the increased output of the megavoltage generators allowed the use of increased focus-skin distances and this enhanced further the dose at depth.
21
A resurgence of interest in the effects of radiation at macroscopic and microscopic level was generated by the availability of these megavoltage machines. Some clinicians became part-time radiobiologists and the number of research workers interested in radiobiology increased. Thus it was necessary and was now practical to establish a unit of absorbed radiation, the rad. Clinicians developed an interest in relating the early and late reactions seen in patients to the level of absorbed dose. This required art accurate estimation of the dose distribution. It is true that this had been possible using techniques pioneered by Parker (1934), Mayneord (1939), Howard Flanders (1943) and many others, but these were time consuming and available to only a few clinicians. The burden of calculating the distribution of dose in the patient fell upon the physics department of most radiotherapy centres, although a few clinicians still felt that they were capable and also had the time to do it. It was natural therefore, with the increased interest in the distribution of absorbed dose, for radiation physicists to look for methods of reducing the time consumed in calculation while maintaining or improving accuracy. At this time, in the early 1950% digital computers were becoming available in universitites and in the biggest commercial organisations. Physicists such as Tsien (1955) in New York and Woods (1962) in this country started projects concerned with the application of computer technology to dose computation. In the early 1960's the potential of the computer was being recognised and some radiotherapists attended courses offered by the manufacturers which were intended to give a general background only, and of interest mainly in the application of electronic data processing to clinical records and the statistical evaluation of treatment regimes. At this time a tentative policy was being developed in the Department of Health concerning the use of computers in the Health Services. The manufacturers were at the same time realising that the introduction of the maxi-computer often created more problems than could be solved technically, and that there was a growing market for the mini-computer in commerce and the microcomputer in the armed services. One of the mini-computers was used to develop a system to provide radiation physicists or radiotherapists with a rapid, flexible, on-the-spot computation service for external beam dose distribution. This work took place in St. Louis and the mark of the British School of Radiotherapy Physics was stamped on this project by the active
22
CLINICAL RADIOLOGY
contribution of Clifton and Bentley (Holmes, 1970). The Programmed Console was the pioneer effort that has led to the concept of the dedicated computer in the radiotherapy centre, fostered by the Physics Department at the Royal Marsden Hospital. It is marketed as the ' R a d 8' system by one manufacturer and a similar concept is the 'PC-12' system. In parallel to the experiment with the concept of the 'dedicated computer' an alternative method has been developed at University College Hospital, the Middlesex Hospital and elsewhere. This uses a maxi-computer, so designed that it can work through many interfaces at effectively the same time. Any interface can be remote from the computer, with communication maintained by means of cables, the telephone exchange, the telex system or even by satellite. For the user at the peripheral terminal the computer would appear to be working for him alone, responding within seconds to the given instructions. Alternatively, if there is no need for this apparent dedication of the computer to a task immediately, then real-time working can be changed for delayed working, which costs less. Then the instructions which have been entered will be obeyed when the system is not working to capacity. However although this may be within the next few minutes, it may be several hours before the task can be completed by the computer. The third concept believes that a limited delay is acceptable. Basic information is sent by post or messenger to a distant computer system where it is processed. The result of the computation, usually printout on paper, is returned by the same method. F o r this method an interval of up to 24 hours is usually accepted (Hope, 1965). The choice of one of these concepts will be determined usually by local circumstances and available money. The technique of loading the system with the basic data, the physics underlying the method of computation and the physical format in which the result is presented exist as several alternatives and are available to any of the systems used by each of these concepts. Thus input is commonly either by teletypewriter, punched paper tape, punched cards or an analogue - to - digital device. There are at least five different methods of using radiation physics to compute the dose distribution from external beams. Some of these methods sacrifice accuracy for speed. -The result can appear on paper from the teletypewriter, the line printer, the incremental plotter, or on a large television or small storage screen. The format can be numbers, either a full matrix or selected in a particular way; as isodose curves; or as a grey scale
distribution. The 'scope display can be monochrome or coloured. RADIATION DOSE COMPUTATION This computation is usually for the co-axial plane but there are programmes that produce the distribution in any plane (Van de Geijn, 1965). Although as far as is known no radiotherapy centre in this country routinely uses such a programme for external beam calculation, several centres abroad assert that they would not be without this facility and have come to depend upon it for the competent planning of treatment, especially around the head and neck, (Kok (1971), personal communication). The computer has been used also to calculate the dose distribution from intracavitary and interstitial sealed radionuclides. Two main types of programme are used. F r o m one, a tabulation of dose rates is produced for selected points. F r o m the other, isodose rate curves or a full matrix of dose rates is produced. As with external beam programmes the output medium will depend on the computer configuration. Of the several parameters needed for calculation of dose or dose-rate those concerned with the patient are the least accurate. The skin outline, or tissue-air interface, in the body cross-section of interest has always proved difficult to translate for input. This was realised before the use of computers but even so most clinicians appear to be content with the inaccurate outline produced by a lead strip. Methods of producing an accurate contour are available but not in routine use. They may be optical (Clayton and Thompson 1970) or mechanical, or use x-rays or laser beams. This apparent lack of interest in accuracy may be due to the assumption that the physical data for absorption of radiation are of greater inaccuracy. But this is no longer true. N o r is it true that allowance cannot be made for tissue inhomogeneity. The most recent R.D.C. programmes allow computation for any area of inhomogeneity and any factor may be inserted uniquely for that area to modify the absorbed dose. Thus it is now the responsibility of the clinician to determine the position within the body cross-section of these areas. This can be done, of course, with tomograms. Trans-axial tomograms (T.A.T.S.) will give in addition an accurate tissue-air interface. The situation now exists by which a dose computation can be produced in about a minute on a visual display unit (V.D.U.) or between five and
DO
WE
NEED
A COMPUTER?
23
ten minutes on a plotter or line printer. It is more distribution is to confirm the position of the beams accurate than when done manually and the process on the patient using the simulator. Some current will be repeated without fatigue. It is true that a models use image intensification systems that prophysicist in training could and should do the same duce a display on a television screen remotely. work and, as salaries stand at the moment, probably Therefore controls are motorised and it does not at less cost. With increasing shortage of staff in take much imagination to realise that a digital hospitals is this the correct use of physicists? And read-out of each parameter at the console would how many physicists will prepare routinely alter- be useful. Taken a step further, at the completion native dose distributions so that the best position of of the simulation, the final readings of the parathe field can be determined? The selection from meters should be printed out. The real indication several beam positions of that which gives the best for doing this is to prevent inaccuracy in reading distribution - and another paper would be required linear or angular scales, a subject in its own right to consider the parameters of the 'best' distribution which will be discussed briefly below. - involves the concept of individualisation of At the Institut Gustave-Roussy work is in treatment planning. By this is meant the fitting of progress in this field. There are twelve variates beams to the patient, rather than the alternative, possible on a treatment machine or simulator. It that of fitting the patient into a standard beam has been estimated that for any one treatment configuration of known dose distribution. For machine during any one year the radiographer will this method of planning treatment, an 'atlas' has have to set accurately 80,000 readings. Not only been proposed which has been prepared with is this time consuming but there is the possibility of computer aid. It is believed that such an atlas to error. be useful must contain several hundred distriBomford (1970) pointed out the variation in the butions in order to match accurately the changing method of scaling on treatment machines. Unless parameters of body cross-section, which are the necessary changes have been made by the dependent upon sex, anatomical level and patient physicist, most radiotherapy departments will be size; of the target volume, which will be related to using treatment machines and simulators upon whether or not lymph drainage is to be included; which the rotational and linear scales of some of and of the position of critical organs. these movements will differ from one machine to the The argument for this concept is that of cheap- other. A working party at the recent conference in ness and speed. The reduction in the cost of one Uppsala studied this problem and has made recomaspect of treatment would allow more money to mendations, which it is believed manufacturers be spent on another. However, the facility of will adopt. The construction of programmes to calculating accurately the dose distribution for the monitor treatment parameters or to link simulator individual patient must not be lightly discarded. and treatment machines has focussed attention There is no doubt that the dose distribution from upon the need for an accepted standard for scales. external beams, from interstitial radio-nuclides or The logical development beyond a simple printintracavitary sources can be adequatelycalculated by out of the parameters obtained during planning on hand. But due to lack of time it is usual to restrict the simulator is to feed them back into the comthe calculation to a handful of point doses in one puter. The programme will then carry out a plane only, or isodose curves with values, for comparison with those used to produce the original example greater than 80 ~ of the target volume dose distribution, and if there are differences a new dose. It is not practicable to produce routinely the distribution will be calculated. distribution away from the coaxial plane, to calculate the effect of air-spaces, or to estimate the MONITORING. -- Comment has been made volume of tissue that is receiving, for example, already about the possibility of error, not only by less than 5 0 ~ of the target volume dose. Do the radiotherapist or physicist during his calculation we need the facilities of the computer to give this of the dose distribution, but also by the radioadditional information? And how should it be grapher in the translation from the prescription to presented - as a grid, as density gradients, as the parameters set on the machine. isodose curves with printed values or as curves for Recently manufacturers have motorised field-size which the value is determined by reference to a diaphragms and other variables. This has been table? done in order to preset treatment parameters so that the time of setting up the patient will be reduced. S I M U L A T O R S . -- The logical step in the planning As with the simulator it is logical to have a read-out process that follows calculation of the best overall mechanism.
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CLINICAL
So far those physicists and clinicians who have considered this development have been more interested in the facilities for monitoring that this allows rather than in any time-saving. Initially the read-out of parameters set is only a record of the conditions under which treatment has been given, which, it is always hoped, is the same as the treatment intended. It would be better for the patient if an error could be prevented. This could be done by comparing the read-out with a control. This could be achieved by punched cards or any other record and read-out medium. The difficulty arises in deciding the range of disagreement acceptable for each of the parameters. Work has already begun on this at Uppsala Hospital, the Royal Marsden Hospital, the Institut Gustave-Roussy and no doubt at other centres. During the next few years development will be taking place upon the linking - which is entirely logical - of the dose computation, the simulator and the treatment machine with a view to ensuring the accurate fulfilment of the planned course of treatment. The logical method of linking is through a computer exercising the function of calculating machine and process controller. A good principle of management is to obtain the best return for the chosen outlay of resources, a principle which in the N.H.S. is frequently debased to obtaining a service at the cheapest cost. The effect is that salaries of, for instance, radiographers, cannot compare with those for occupations otherwise available to the young girl, and fewer radiographers will be trained therefore in the future. In order to maintain good standards of patient care, less time will be available for such chores as manuscript recording of the treatment given. It is suggested that the computer will be needed in this sphere in order to allow these fewer radiographers to continue to devote time to reassuring the patient, maintaining the liaison between patient and radiotherapist, and helping the nursing staff. Further, used intelligently the computer can prevent the disasters which, due to the fallibility of the human, particularly if under pressure, have happened in the past. EVALUATION OF TREATMENT.-- We all, from time to time, fall into the trap of remembering the occasional patient who unexpectedly responded well to a particular form of therapy to the exclusion of the majority who did not. A person's outlook may also be biased by such factors in his clinical environment as degree of specialisation and individual experience, which may be grossly misleading as a
RADIOLOGY
basis for judgement. Realisation of the fact over the past decade has led to the present interest in clinical trials. Unfortunately a clinical trial is based firmly upon numbers. The larger the number of patients observed the smaller is the chance that the observations are fortuitous. Not all clinicians see enough patients to allow conduct of a clinical trial - and for some rare types of disease there will never be enough patients. However, much useful clinical information can be obtained by keeping good records and this has always been a feature of radiotherapy departments. Frequently however, access to the mass of information recorded in clinical records has been difficult, relying at the worst on the memory of names or registration numbers and at the best upon a card index or punch card system. Either method resulted in considerable effort to recover facts and often the quality and quantity of information was severely limited by the recording medium. Data processing using the computer, applied to clinical records of malignant disease, has been used in Liverpool since January 1970. The system has been described elsewhere (Edwards, 1972) but it is appropriate to review in the context of this paper the advantages and disadvantages of such a system. The disadvantages could be listed as :I) Computer not on site. Initially there are problems of liaison with the members of the computer centre team. 2) Batch processing operation. This is acceptable for input, but for output of analysis is a change from previous working. 3) Involvement of another unit. Some control of the process is relinquished to the computer centre staff. Significant advantages are :1) The quantity of data held is solely dependent on the system chosen. 2) The system acts, not only as a file, but also as a sorting mechanism, a calculating machine, and a printer or graph producer. 3) The system to a large extent becomes capable of automatically updating the information, e.g. calling for follow-up reports and sending out follow-up letters. The overall process of acquiring, processing and analysing information on malignancy is cheaper. The clinician who wishes to assess frequently whether the patients treated by him have benefited or not has the alternative of continuing with the
25
D O WE N E E D A C O M P U T E R . 9
manual methods or o f using some f o r m o f electronic data processing. The small dedicated computer systems have recently included in their software packages a simple file-handling p r o g r a m m e orientated toward the clinician w h o alternatively can make arrangements to use the Regional Board's H.A.A. system, but this, for the moment, is very limited in its capabilities for storing clinical data. He can develop, with the co-operation o f the Board's computer centre staff, a dedicated programme for handling his clinical records, or he can encourage the regional cancer registry to include the information in which he is interested. If the registry is not based u p o n an E.D.P. system he can encourage interest in the use o f the computer for the case records. I n particular he can give expert advice on the data to be recorded for radiotherapy. This advice, it is to be hoped, would involve the inclusion o f the ' R e c o m m e n d e d List o f Variates' which is now finding acceptance, not only in this country, but also in Europe. CONCLUSION An outline has been given o f the present use o f the computer in nuclear medicine and radiotherapy with an indication o f probable trends for the near future. The Faculty, the British Institute o f Radiology and the Hospital Physicists' Association have different levels o f interest in the application o f computers. However, it is the clinicians responsible for the care o f patients who should determine the use to be made o f this new technology. 'Management' is the 'in' w o r d in the National Health Service today. This is a useful concept if the definition o f management is accepted as 'the best use o f available resources'. However, the tendency at the m o m e n t is for administrators to decide what is 'best' because the general b o d y o f clinicians do not appear to have the inclination or the time to do the h o m e w o r k and give advice based on the homework. At a recent meeting o f a committee concerned with computing it was shown that on average a dedicated computer might be used on R.D.C. w o r k for only 25 ~ o f the time, and deduced that R.D.C. on a dedicated c o m p u t e r was not cost-effective. This argument is spurious: m a n y items of equipment n o w regarded as essential to a radiotherapy
department - the simulator for example - are idle for over half the working time. To establish the most sensible and economic usage the opinions o f clinicians must be available, k n o w n to be available, and indeed proferred. It is hoped that this paper m a y stimulate clinicians in radiotherapeutics and nuclear medicine to evaluate the application of computers to their discipline.
Acknowledgements. --I wish to express my gratitude to the many radiotherapists and physicists in this country and abroad who have given freely of their time to discuss or demonstrate their concept of the application of the computer.
REFERENCES USING COMPUTERS TO IMPROVE HEALTH SERVICES (1972).
pub. Department of Health and Social Security reference 8488/908914. BENTLEY, R. E. t~, MILAN, J. (1971). An interactive digital computer system for radiotherapy treatment planning. British Journal of Radiology, 44, 826-833. BOMFORD,C. K. (1970). Letter to tile Editor "Do simulators simulate". British Journal of Radiology 43, 583. CLAYTON, C. B. • THOMPSON, D. J. (1973). An optical apparatus for reproducing surface outlines of body crosssections. British Journal of Radiology, 43, 489-492. EDWARDS,D. N. (1972). Clinical records and electronic data processing. Clinical radiology, 23, 117-216. FLANDERS,P. H. (1943). A dose contour finder for symmetrical and unsymmetrical radiation beams. British Journal of Radiology, 16, 314-316. HOLMES, W. F. (1970). External treatment planning with the Programmed Console. Radiology, 94, 391-400. HOPE, C. S. & ORR, J. S. (1965). Computer optimisation of 4MV treatment planning. Physics in Medicine & Biology, 10, 365-373. MAYNEORD, W. V. (1939). A dose contour projector and its application to three-dimensional radiation distributions. British Journal of Radiology, 12, 262-268. PATERSON,R. & PARKER,H. M. (1934). A dosage system for gamma ray therapy. British Journal of Radiology, 7, 592-632. TSlEN, K. C. (1955). The application of automatic computing machines to radiation treatment plamaing. British Journal of Radiology, 28, 432-439. VAN DE GE1JN,J. (1965). The computation of two and daree dimensional dose distributions in Cobalt 60 teletherapy. British Journal of Radiology, 38, 369-377. WOOD, R. G. (1962). The computation of dose distributions in Cobalt rotational therapy. British Journal of Radiology, 35, 482-484.