754 Pr oc. roy. Soc. Med. Volume 68 December 1975
Research into time effects will undoubtedly be helped forward by computers which, guided aright, will uncover hitherto unknown but significant correlations from the data available even today. The fifth dimension relates to mind. It was not many years ago that orthodox medicine completely dismissed psychosomatic causes. That has now changed in some areas of medicine. It is now possible to predict the degree of ill health a person may on average expect in the near future from a close study of his style of living in the recent past. Major and minor domestic and professional crises operate on an additive debit account basis as far as future health is concerned. So far it has not been possible to predict the type of illness, but some observers feel that analysis of enough cases, no doubt helped by computer, may lead to a better understanding of these matters. How long will it be before psychological counselling and conventional treatment planning join hands ? It would be prudent to end on a note of caution. Computers can be of inestimable help in many spheres, radiotherapy included, but they should always be used as willing servants rather than be allowed to become dictators. They are logical not intelligent. Hence the wise phrase 'Garbage in - Garbage out' which ought to hang over every computer terminal in the world.
28
in radiotherapy departments, usually by radiotherapists. Part of the intention is to save time on the X-ray therapy machines, though the cost of purpose-built, commercially available simulators makes this consideration questionable. Another aspect is that the films taken on high energy machines, whether accelerators or telecobalt machines, are seldom of the diagnostic quality which is preferred for checking of treatment prescriptions. The process of treatment planning includes all steps leading up to the preparation of the prescription giving detailed instructions to the therapy radiographers, but there still remains to be discussed the question of the degree of sophistication of the demonstration of dose distribution which is required or justified in individual patients. The process starts with the patient and the establishment of a diagnosis, from the pathological and, even more important, from the anatomical point of view. The first step is to define the treatment volume, that is, the volume of tissue which the radiotherapist wishes to be irradiated. The definition of this volume may require extensive investigations including clinical examinations, endoscopy where appropriate, and, very often, X-ray diagnostic examinations. There are, of course, occasions when the definition of treatment volume is very easy, as, for example, in the patient with a small rodent ulcer on the skin or, say, a Stage 1 carcinoma of the tongue, and REFERENCES others where the boundaries of the treatment Dombal F T de, Leaper D J, Staniland J R, McCann A P volume are defined by arbitrary anatomical & Horrocks J C (1972) British MedicalJournal ii, 9-13 Ellis F (1969) Clinical Radiology 20, 1 landmarks, as in postoperative treatment for Harker J E (1964) The Physiology ofDiurnal Rhythms. carcinoma of the breast, or so-called 'upper Cambridge University Press, London Kirk J. Grey W M & Watson E R mantle' technique for limited Hodgkin's disease. (1971) Clinical Radiology 22, 145 More often than not, however, the edges of the Luce G G (1972) Body Time. Temple Smith, London tumour are difficult to define exactly, particularly Pizzarello D J & Isak D (1964) Science 145, 286-291 where it is situated deeply and is not palpable. In Thompson D J (1972) Digest of the III International Conference this situation, the process may be aided by radioon Medical Physics, including Medical Engineering, Goteborg, Sweden. Contribution 18.8 graphy, including the use of contrast media, and the possible use of radio-opaque markers inserted into the tumour. When the margins of the tumour have been defined, an arbitrary decision must be made as to the margin of apparently normal tissue to be included in the treatment Dr W M Ross volume, and this will vary considerably according (Newcastle General Hospital, to the pathological nature and expected natural Newcastle upon Tyne, NE4 6BE) history of the tumour. For example, the mode of spread of many carcinomas of the cesophagus in the submucosal layer leads to the generally Planning in Radiotherapy Departments: Techniques and Problems - General Aspects accepted convention that the treatment volume must be at least 5 cm from the macroscopic All radiotherapy is planned but I will confine my edge of the tumour. remarks to external beam therapy, with particular After defining the treatment volume in this way, reference to the detailed preparation for treat- the body surface in the relevant segment of the ment which is being carried out in a majority of body must then be defined and committed to patients. In general, the process involves the paper. It is unfortunately true that the body use of diagnostic X-ray techniques and equipment section is seldom one of the recognized geo-
755
29'
Section ofRadiology
metrical shapes, though the X-ray beams used for the treatment of patients do follow geometrical outlines. Furthermore, there may be significant changes in the relevant body outline at different phases of respiration, or associated with movements of the body, such as elevation of the arm in relation to the shape of the chest or neck. A decision is, therefore, required as to how many planes should be considered in defining the relevant body surface. The desired treatment volume and the relevant body surface must now be related to one another. In addition, the treatment volume must be related to a fixed point on the body surface or outside it. This fixed point may be a readily identified anatomical feature, such as the external auditory meatus or the anterior superior iliac spine; or may be a mark on a shell made to fit closely over the affected part of the body; or possibly a point on the treatment table top. At this stage in the overall process, cognisance must be taken of the movement of some organs relative to the body surface, as the position of the body moves from, say, prone to supine, or physiological processes, such as the filling and emptying of the urinary bladder. Within the map or maps of the various planes through the relevant body sections into which the treatment volume has been located, further information must now be inserted to take account of the inhomogeneity of the tissues, with of course particular reference to the less dense features such as air-containing cavities, or the lung, and the more dense tissues such as bone, particularly in relation to treatment with X-rays generated at less than megavoltage energies, or with electrons. In connexion with tissue inhomogeneity and allowance for it, a decision must be made as to the likely magnitude of the effect. Also into the map of the section must be inserted the size and position of any tissues particularly sensitive to radiation such as the kidneys or the central nervous system. It will already have been recognized that approximations are being introduced into what should ideally be an exact exercise. It has been seen that the exact definition of tumour volume or body surface may be difficult, and that allowance for tissue inhomogeneities may not be exact. It is, of course, also possible that the relatively small errors resulting from each of these factors may be additive. It would seem, therefore, that having made these approximations, limited or reasonable use of exact accuracy of the physical and mathematical data involved in the later processes of planning is indicated, rather than an attempt at arithmetic perfection. We now have on one or more sheets of paper, perhaps on a television monitor screen, a map
relevant to the particular patient and his disease, and we have reached the stage which in a more limited sense is called 'planning of the treatment'. At this stage, the radiotherapist must define the desired tumour dose and any variation of this dose which is acceptable within the defined treatment volume. He must also define the ratio of the tumour dose to the dose received by other tissues, such as the skin or critical organs, or, if more appropriate, define an absolute maximum dose which may be received by the critical tissues, and in some large field treatments, where relevant, he should indicate a maximum overall or integral dose. At this stage, the application to the map of physical data relating to the various beams of radiation available will permit the demonstration of the possible radiation distribution, and by changing various physical factors, such as the quality of the radiation used, angle and size of the fields, the presence or absence of additional filters, a wide range of distributions may be obtained. A process of optimization of dose distribution must then be followed. When it is done by eye or manually, the patience or time available to the planner makes an effective brake, but if it is being done by the computer, there may in theory be an infinite number of possibilities to compare and of parameters by which to compare them and, therefore, some guidelines such as the maximum number of fields should be fed into the computer before optimization. At this stage, a radiological check of the proposed plan must be carried out to ascertain that the treatment volume is completely included within the treatment plan and that the critical tissues are excluded or sufficiently protected. The final stage of treatment planning can be divided into two parts. The first is to present to the radiotherapy radiographers a complete prescription of the desired treatment, including an accurate diagram, and all necessary details as to the X-ray apparatus to be used, the energy, the size, shape and position of any external filters applied and tumour dose per exposure, &c. The second step at this stage is the preparation of a permanent record of the treatment which includes a radiographic presentation of the treatment fields and possibly skin markers to identify the edges or corners of the field, perhaps by tattooing. This is particularly important in reference toY megavoltage treatment where skin changes may be slight and scarcely identifiable in later years. The permanent record is also important if there should be any subsequent question as to the late effects of the treatment, including possible legal action, and more frequently when the necessity or desirability of repeat treatment arises. The patient carries on with the prescribed treatment, which may last for several weeks,
756 Proc. roy. Soc. Med. Volume 68 December 1975
during which time he may lose a considerable amount of weight, or there may be a significant change in the outline of a tumour. Consideration must be given to the necessity or desirability of repeating the whole planning process. This really depends on a statement of the degree of error which is allowable, thus: is a 1 cm change in the amount of tissue between the skin surface and the tumour volume permissible or is replanning required ? Two aspects of the planning process bear consideration from the point of view of cost-benefit analysis. The first relates to the question as to how many patients are managed in this way and, perhaps, why not all patients who are referred for external beam therapy. It is generally agreed that most patients undergoing radical treatment should have planning of a reasonable degree of accuracy, though the question arises as to what extent standard arrangements such as those commonly employed in postoperative treatment of carcinoma of the breast require individual planning. In relation to patients undergoing palliative treatment, however, there is considerable doubt, with particular reference to singlefield or simple opposed-pair forms of treatment, as to whether the process contributes to the patient's well-being. Furthermore, for some patients with a very poor prognosis, the time required in planning may actually exceed the time they spend on the treatment machines, which may not be desirable. A further consideration here is the question of whether the planning and field verification should be done on a simulator or on the therapy apparatus, taking into account the relative cost of the two machines and the staff required to run them. The second aspect of the possible cost-effective analysis relates to the 'who does what' problem, among the potential staff involved in the planning section of the radiotherapy centre; the three groups of people concerned are the doctors, the radiographers and the physicists. The radiotherapist must, of course, give all the initial basic information about the patient, including diagnosis and the required dose distribution. It will generally be accepted that he cannot, if only for reasons of time, undertake all the treatment planning himself, but he should have sufficient experience of planning procedures to be able to discuss the plans with all those concerned and to comment critically and sensibly on them. His also is the responsibility for checking and accepting the final prescription. Treatment planning is a field of interest to some radiographers, particularly those who have a knowledge of both radio-
30
diagnosis and radiotherapy, and I think that this is the correct and probably the best group of people to do most of the treatment planning in a major centre, supported of course by the other groups concerned. This aspect of radiography can make a career for the appropriate radiographer, who will provide valuable continuity. She will normally relate well to patients, doctors and scientists, as well as to her radiographer colleagues, but she should be supported by all the available aids and, where practicable, should have access to a dedicated computer. The physicist's expertise and advice is essential in the development of treatment planning services and the provision of the necessary underlying data. His advice should always be available on practical points, such as those referring to the therapy or simulator apparatus, construction of filters and design of compensators. It is unlikely that a physicist would wish to dedicate most of his time for even a period of one or two years to routine treatment planning and, therefore, unlikely that he will give as satisfactory a degree of continuity as would a radiographer. He will also be required to advise about the appropriate computer programs and back-up services. In this necessarily rather brief survey, I have mentioned some of the many processes involved in treatment planning and some of the problems which I think are not yet satisfactorily solved.
Meeting 13 December 1974
The following papers were read: The Radiology of Paintings Mr S Rees Jones (Courtauld Institute of Art, 20 Portman Square, London WI)
The Radiology of Saxon and Medieval Remains from Winchester Cathedral Green Dr John L Price (Milford Chest Hospital, Godalming; King Edward VII Hospital, Midhurst) REFERENCE Price J L (1975) Clinical Radiology (in press)
The Earth in Space Mr Douglas Arnold (Space Frontiers Ltd, 30 Fifth Avenue, Havant, Hampshire)
Research into time effects will undoubtedly be helped forward by computers which, guided aright, will uncover hitherto unknown but significant correlations from the data available even today. The fifth dimension relates to mind. It was not many years ago that orthodox medicine completely dismissed psychosomatic causes. That has now changed in some areas of medicine. It is now possible to predict the degree of ill health a person may on average expect in the near future from a close study of his style of living in the recent past. Major and minor domestic and professional crises operate on an additive debit account basis as far as future health is concerned. So far it has not been possible to predict the type of illness, but some observers feel that analysis of enough cases, no doubt helped by computer, may lead to a better understanding of these matters. How long will it be before psychological counselling and conventional treatment planning join hands ? It would be prudent to end on a note of caution. Computers can be of inestimable help in many spheres, radiotherapy included, but they should always be used as willing servants rather than be allowed to become dictators. They are logical not intelligent. Hence the wise phrase 'Garbage in - Garbage out' which ought to hang over every computer terminal in the world.
28
in radiotherapy departments, usually by radiotherapists. Part of the intention is to save time on the X-ray therapy machines, though the cost of purpose-built, commercially available simulators makes this consideration questionable. Another aspect is that the films taken on high energy machines, whether accelerators or telecobalt machines, are seldom of the diagnostic quality which is preferred for checking of treatment prescriptions. The process of treatment planning includes all steps leading up to the preparation of the prescription giving detailed instructions to the therapy radiographers, but there still remains to be discussed the question of the degree of sophistication of the demonstration of dose distribution which is required or justified in individual patients. The process starts with the patient and the establishment of a diagnosis, from the pathological and, even more important, from the anatomical point of view. The first step is to define the treatment volume, that is, the volume of tissue which the radiotherapist wishes to be irradiated. The definition of this volume may require extensive investigations including clinical examinations, endoscopy where appropriate, and, very often, X-ray diagnostic examinations. There are, of course, occasions when the definition of treatment volume is very easy, as, for example, in the patient with a small rodent ulcer on the skin or, say, a Stage 1 carcinoma of the tongue, and REFERENCES others where the boundaries of the treatment Dombal F T de, Leaper D J, Staniland J R, McCann A P volume are defined by arbitrary anatomical & Horrocks J C (1972) British MedicalJournal ii, 9-13 Ellis F (1969) Clinical Radiology 20, 1 landmarks, as in postoperative treatment for Harker J E (1964) The Physiology ofDiurnal Rhythms. carcinoma of the breast, or so-called 'upper Cambridge University Press, London Kirk J. Grey W M & Watson E R mantle' technique for limited Hodgkin's disease. (1971) Clinical Radiology 22, 145 More often than not, however, the edges of the Luce G G (1972) Body Time. Temple Smith, London tumour are difficult to define exactly, particularly Pizzarello D J & Isak D (1964) Science 145, 286-291 where it is situated deeply and is not palpable. In Thompson D J (1972) Digest of the III International Conference this situation, the process may be aided by radioon Medical Physics, including Medical Engineering, Goteborg, Sweden. Contribution 18.8 graphy, including the use of contrast media, and the possible use of radio-opaque markers inserted into the tumour. When the margins of the tumour have been defined, an arbitrary decision must be made as to the margin of apparently normal tissue to be included in the treatment Dr W M Ross volume, and this will vary considerably according (Newcastle General Hospital, to the pathological nature and expected natural Newcastle upon Tyne, NE4 6BE) history of the tumour. For example, the mode of spread of many carcinomas of the cesophagus in the submucosal layer leads to the generally Planning in Radiotherapy Departments: Techniques and Problems - General Aspects accepted convention that the treatment volume must be at least 5 cm from the macroscopic All radiotherapy is planned but I will confine my edge of the tumour. remarks to external beam therapy, with particular After defining the treatment volume in this way, reference to the detailed preparation for treat- the body surface in the relevant segment of the ment which is being carried out in a majority of body must then be defined and committed to patients. In general, the process involves the paper. It is unfortunately true that the body use of diagnostic X-ray techniques and equipment section is seldom one of the recognized geo-
755
29'
Section ofRadiology
metrical shapes, though the X-ray beams used for the treatment of patients do follow geometrical outlines. Furthermore, there may be significant changes in the relevant body outline at different phases of respiration, or associated with movements of the body, such as elevation of the arm in relation to the shape of the chest or neck. A decision is, therefore, required as to how many planes should be considered in defining the relevant body surface. The desired treatment volume and the relevant body surface must now be related to one another. In addition, the treatment volume must be related to a fixed point on the body surface or outside it. This fixed point may be a readily identified anatomical feature, such as the external auditory meatus or the anterior superior iliac spine; or may be a mark on a shell made to fit closely over the affected part of the body; or possibly a point on the treatment table top. At this stage in the overall process, cognisance must be taken of the movement of some organs relative to the body surface, as the position of the body moves from, say, prone to supine, or physiological processes, such as the filling and emptying of the urinary bladder. Within the map or maps of the various planes through the relevant body sections into which the treatment volume has been located, further information must now be inserted to take account of the inhomogeneity of the tissues, with of course particular reference to the less dense features such as air-containing cavities, or the lung, and the more dense tissues such as bone, particularly in relation to treatment with X-rays generated at less than megavoltage energies, or with electrons. In connexion with tissue inhomogeneity and allowance for it, a decision must be made as to the likely magnitude of the effect. Also into the map of the section must be inserted the size and position of any tissues particularly sensitive to radiation such as the kidneys or the central nervous system. It will already have been recognized that approximations are being introduced into what should ideally be an exact exercise. It has been seen that the exact definition of tumour volume or body surface may be difficult, and that allowance for tissue inhomogeneities may not be exact. It is, of course, also possible that the relatively small errors resulting from each of these factors may be additive. It would seem, therefore, that having made these approximations, limited or reasonable use of exact accuracy of the physical and mathematical data involved in the later processes of planning is indicated, rather than an attempt at arithmetic perfection. We now have on one or more sheets of paper, perhaps on a television monitor screen, a map
relevant to the particular patient and his disease, and we have reached the stage which in a more limited sense is called 'planning of the treatment'. At this stage, the radiotherapist must define the desired tumour dose and any variation of this dose which is acceptable within the defined treatment volume. He must also define the ratio of the tumour dose to the dose received by other tissues, such as the skin or critical organs, or, if more appropriate, define an absolute maximum dose which may be received by the critical tissues, and in some large field treatments, where relevant, he should indicate a maximum overall or integral dose. At this stage, the application to the map of physical data relating to the various beams of radiation available will permit the demonstration of the possible radiation distribution, and by changing various physical factors, such as the quality of the radiation used, angle and size of the fields, the presence or absence of additional filters, a wide range of distributions may be obtained. A process of optimization of dose distribution must then be followed. When it is done by eye or manually, the patience or time available to the planner makes an effective brake, but if it is being done by the computer, there may in theory be an infinite number of possibilities to compare and of parameters by which to compare them and, therefore, some guidelines such as the maximum number of fields should be fed into the computer before optimization. At this stage, a radiological check of the proposed plan must be carried out to ascertain that the treatment volume is completely included within the treatment plan and that the critical tissues are excluded or sufficiently protected. The final stage of treatment planning can be divided into two parts. The first is to present to the radiotherapy radiographers a complete prescription of the desired treatment, including an accurate diagram, and all necessary details as to the X-ray apparatus to be used, the energy, the size, shape and position of any external filters applied and tumour dose per exposure, &c. The second step at this stage is the preparation of a permanent record of the treatment which includes a radiographic presentation of the treatment fields and possibly skin markers to identify the edges or corners of the field, perhaps by tattooing. This is particularly important in reference toY megavoltage treatment where skin changes may be slight and scarcely identifiable in later years. The permanent record is also important if there should be any subsequent question as to the late effects of the treatment, including possible legal action, and more frequently when the necessity or desirability of repeat treatment arises. The patient carries on with the prescribed treatment, which may last for several weeks,
756 Proc. roy. Soc. Med. Volume 68 December 1975
during which time he may lose a considerable amount of weight, or there may be a significant change in the outline of a tumour. Consideration must be given to the necessity or desirability of repeating the whole planning process. This really depends on a statement of the degree of error which is allowable, thus: is a 1 cm change in the amount of tissue between the skin surface and the tumour volume permissible or is replanning required ? Two aspects of the planning process bear consideration from the point of view of cost-benefit analysis. The first relates to the question as to how many patients are managed in this way and, perhaps, why not all patients who are referred for external beam therapy. It is generally agreed that most patients undergoing radical treatment should have planning of a reasonable degree of accuracy, though the question arises as to what extent standard arrangements such as those commonly employed in postoperative treatment of carcinoma of the breast require individual planning. In relation to patients undergoing palliative treatment, however, there is considerable doubt, with particular reference to singlefield or simple opposed-pair forms of treatment, as to whether the process contributes to the patient's well-being. Furthermore, for some patients with a very poor prognosis, the time required in planning may actually exceed the time they spend on the treatment machines, which may not be desirable. A further consideration here is the question of whether the planning and field verification should be done on a simulator or on the therapy apparatus, taking into account the relative cost of the two machines and the staff required to run them. The second aspect of the possible cost-effective analysis relates to the 'who does what' problem, among the potential staff involved in the planning section of the radiotherapy centre; the three groups of people concerned are the doctors, the radiographers and the physicists. The radiotherapist must, of course, give all the initial basic information about the patient, including diagnosis and the required dose distribution. It will generally be accepted that he cannot, if only for reasons of time, undertake all the treatment planning himself, but he should have sufficient experience of planning procedures to be able to discuss the plans with all those concerned and to comment critically and sensibly on them. His also is the responsibility for checking and accepting the final prescription. Treatment planning is a field of interest to some radiographers, particularly those who have a knowledge of both radio-
30
diagnosis and radiotherapy, and I think that this is the correct and probably the best group of people to do most of the treatment planning in a major centre, supported of course by the other groups concerned. This aspect of radiography can make a career for the appropriate radiographer, who will provide valuable continuity. She will normally relate well to patients, doctors and scientists, as well as to her radiographer colleagues, but she should be supported by all the available aids and, where practicable, should have access to a dedicated computer. The physicist's expertise and advice is essential in the development of treatment planning services and the provision of the necessary underlying data. His advice should always be available on practical points, such as those referring to the therapy or simulator apparatus, construction of filters and design of compensators. It is unlikely that a physicist would wish to dedicate most of his time for even a period of one or two years to routine treatment planning and, therefore, unlikely that he will give as satisfactory a degree of continuity as would a radiographer. He will also be required to advise about the appropriate computer programs and back-up services. In this necessarily rather brief survey, I have mentioned some of the many processes involved in treatment planning and some of the problems which I think are not yet satisfactorily solved.
Meeting 13 December 1974
The following papers were read: The Radiology of Paintings Mr S Rees Jones (Courtauld Institute of Art, 20 Portman Square, London WI)
The Radiology of Saxon and Medieval Remains from Winchester Cathedral Green Dr John L Price (Milford Chest Hospital, Godalming; King Edward VII Hospital, Midhurst) REFERENCE Price J L (1975) Clinical Radiology (in press)
The Earth in Space Mr Douglas Arnold (Space Frontiers Ltd, 30 Fifth Avenue, Havant, Hampshire)
