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Resume Trente-quatre patients qui avaient consulte leur medecin generaliste cinq fois ou plus pendant une periode de trois mois ont ete compares avec trente-quatre personnes qui ne l'avaient consulte qu'une fois pendant la meme periode. On les a compares selon l'âge et le sexe en utilisant des criteres psychosomatiques. Les tests utilises pour cette etude etaient le Questionnaire sur la Sante Generale, l'Inventaire de la Personnalite d'Eysenck (EPI) et le Differenciateur Semantique. Les sujets a consultations frequentes obtenaient le plus de points avec le Questionnaire sur la Sante Generale et avec l'EPI et le differenciateur semantique revelait des differences majeures dans l'attitude a l'egard de la sante, de l'aide, de soi et des medecins. Ces differences pouvaient etre la cause de la frequence des consultations ou, aussi, etre causees par elle.

Previous work (see ibid., vol.16, 577) has been continued to determine the practical capabilities of the system. A higher resolution Ge(Li) detector has been used to portray the scattering along the lines of passage of a 137Cs gamma -ray beam, and from these results it is possible to construct density cross-sections of the body. The limitations are shown to be due to (a) signal/noise arising from multiple scattering in the body and (b) resolution, which is governed by the finite beam width and finite aperture needed in front of the crystal. A suggested design of a twin-headed machine for clinical use is given.

The problem of viewing the emergent ray image from a Treatment Planning Simulator is met by the use of xeroradiography. With this a finished picture is obtained within 10 seconds of completion of the X-ray exposure, which may be studied as a basis of further beam adjustment, or photographed if desired. This technique has the advantage over film, not only of speed in processing, but of showing soft tissue detail, bone detail, air passages and skin outline, all within the same X-ray exposure range. The Simulator at Newcastle on Tyne is described and illustrations of its use in relation to the 4 MeV linear accelerator are given.

Attention has recently been directed to the measurement of the relative amplitudes of wireless echoes from the ionosphere, and some interesting methods of automatic registration have been devised (1, 2). For vertical incidence, and for wave-lengths shorter than 200 metres, visual observation shows that a single echo, even when separated from its accompanying oppositely polarized magneto-ionic component, shows considerable rapid fading (3). This fading is evident on the records published by White (1), and it is clear from these that it is not easy to determine the relative amplitudes of two echoes. This paper is an account of an apparatus which automatically integrates the amplitude of an echo over a time long compared with the period of the fading, and at the end of the period registers the integrated value on a recording galvanometer. The process is then repeated so that the final galvanometer trace represents the average value of the intensity throughout successive equal periods of time. It is further described how by using a double thread recording galvanometer, it is possible to record the averaged amplitudes of two different echoes (e.g. ordinary and extraordinary, or E and F) during alternate integrating periods.

A condenser ionization chamber small enough for comfortable insertion in body cavities, and capable of measuring doses up to 200 r in deep X-ray treatments, is described. The large range accentuates the physical problems in design, and several sources of inaccuracy, common in some degree to all condenser chambers, are investigated. They include ionization in the cap of the chamber, conductivity of the dielectric on exposure to X rays, and frictional and surface charges on the insulator. With suitable modifications in construction these are eliminated, and a chamber is derived which is capable of the required accuracy of measurement under practical conditions of treatment.

Current methods of determining anatomical cross-sections of the body for cancer treatment planning including transaxial tomography have severe limitations and a new method is described depending on the change of wavelength of gamma -rays in Compton scattering. A narrow beam of 137Cs gamma -rays is passed through the body, and the scattered radiation is picked up and analysed by a Ge(Li) detector so that the intensity is portrayed against distance through the body. The primary beam is moved slowly to traverse the whole cross-sectional area and the density pattern so obtained displayed on a cathode ray screen. Problems including limitations of resolution and attenuation of the primary and secondary radiation are studied, and an experimental arrangement, which it is hoped will lead to a practical working system, is described.

A circuit is described for producing in a cathode-ray oscillograph a time base suitable for the investigation of wireless pulses reflected from the ionosphere when no ground wave is present. The time base is locked to the received groups of echoes and gives a stationary pattern on the oscillograph even when all the echoes are fading considerably. The whole group of echoes, including the first, is delineated on a portion of the time base which is not obscured by end effects in the trace, so that accurate measurements of time intervals can be made.

1. Three patients with myelomatosis were given intravenous 177Lu. 2. The 177Lu was shown to be taken up by the bones and concentrated around the lesions. 3. None of the patients was clinically improved by treatment with this isotope.

Many investigations of Region E of the ionosphere have been described, in the more detailed of which the critical-frequency technique of Appleton has been used to determine the penetration frequency of the region. In the latest work this has generally involved continuous variation of frequency and photographic recording so that the finer details of the P'-f curve, relating equivalent path ( P' ) to frequency ( f ), could be obtained. It has usually happened, however, that these records have been obtained at considerable time intervals, such as half an hour or an hour, so that the finer details of the temporal variations in the behaviour of the region could not be followed. The present paper describes observations made in such a way as to exhibit the finer details of the temporal variations. The Breit and Tuve pulse method was used, in conjunction with a cathode-ray oscillograph employing a timesweep in the usual way at the receiver. The oscillograph, was, however, observed visually, and the observer could alter the frequency of the transmitter (situated about 1 mile away) by means of a remote control. In this way it was possible to keep a continuous detailed watch on the temporal variations of any particular feature of the P'-f curve. The observations were made in Cambridge during the second half of 1936.

The waves emitted by a pulse transmitter at Cambridge were simultaneously received at a point distant I km. and at Edinburgh distant 464 km. in a direction 15° west of magnetic north. The variation of equivalent path with emitted frequency was studied for waves of such a frequency that they nearly penetrated the F region. The results agreed qualitatively with a simplified theory, and under certain conditions showed the possibility of two transmission paths to the distant point. A quantitative discrepancy between the simple theory and experiment was noticed and its possible explanations are discussed. It is shown that by comparing the frequencies which just penetrate the E region at normal and oblique incidence it might be possible to decide whether the Lorentz polarization term should be included in calculating the force on an electron in the ionosphere. Experiments made for this purpose provided only a statistical result on account of the variable nature of the E region. Measurement of the sunrise increase of absorption for waves received at the two points indicated that the day-time absorption takes place in a region below the main deviating portion of the E region, for echoes both from the E and from the F region.

A brief review is given of the factors limiting the accuracy of routine measurement of X rays used for deep therapy. The methods considered are the integrating dosemeter technique, and the method of tube output calibration, both of which are in common use. A third type of measuring system which has been tried experimentally is also discussed. This comprises an ionisation chamber in the output aperture of the tube, and an integrating mechanism similar to that of the Mekapion on the operator's desk, so that the integrated dosage can be measured without the need for placing an instrument at the base of the applicator. Some inaccuracies in the other techniques are avoided in this way, and its relative advantages and disadvantages are discussed.

Experiments are described which compare the F-region skip frequency, for transmission between two distant stations, with that calculated from the normal-incidence characteristics on a simple ray theory. The greatest possible accuracy was aimed at so that the results might resolve an uncertainty left in previous measurements, in which the forms of the oblique and normal incidence P'f curves were compared. This involved using a pulse-transmitter at each end of the oblique trajectory to correct for horizontal variations of ionization, and developing a special rapid technique. Measurements were confined to days when the ionosphere was in a completely undisturbed state, as shown by the clean splitting of echoes at normal incidence. The results showed that the theory, which neglects the earth's magnetic field, is very nearly correct for the ordinary wave over a transmission distance of about 500 km. The precise disagreement is determined, and it is believed that if an accurate theory be developed the results will indicate whether or not the Lorentz term should be included in the analysis.

A technique is described for the measurement of the rate of travel of high-frequency impulses over the ground. Two transmitters 60 km. apart and operated off a common A.C. supply provided the signals, and the time intervals between the arrival of the local and distant impulses were measured at each station. From these the mean rate of travel could be determined. The measurements were made on a cathoderay tube in a manner similar to that used in ionospheric work, and the precautions necessary to secure accurate results are described. Results are given which show that the velocity of propagation is within a few per cent of that of light; and it is concluded that the experiments of other workers which yielded a much smaller value for the velocity are subject to some error.

An investigation of the accuracy of general practitioner and Executive Council files was approached by a comparison of the two. High error rates were found, including both file errors and record errors. On analysis it emerged that file error rates could not be satisfactorily expressed except in a time-dimensioned way, and we were unable to do this within the context of our study. Record error rates and field error rates were expressible as proportions of the number of records on both the lists; 79·2% of all records exhibited non-congruencies and particular information fields had error rates ranging from 0·8% (assignation of sex) to 68·6% (assignation of civil state). Many of the errors, both field errors and record errors, were attributable to delayed updating of mutable information. It is concluded that the simple transfer of Executive Council lists to a computer filing system would not solve all the inaccuracies and would not in itself permit Executive Council registers to be used for any health care applications requiring high accuracy. For this it would be necessary to design and implement a purpose designed health care record system which would include, rather than depend upon, the general practitioner remuneration system.

A new experimental technique is described for studying the directional and polarization characteristics of wireless echoes. The method makes use of an ordinary spaced frame direction-finding system, combined with a twin channel amplifier and cathode-ray tube, so that by observations of an ellipse on the screen the phases and amplitudes of the e. m. f. s in the aerial system may be determined. By appropriate connexions of the aerials either of the two characteristics mentioned may be studied. The equipment is made applicable to pulse transmissions by means of an 'echo selecting’ device, which has the function of desensitizing the apparatus for all but a small element of the time-base cycle. The duration of the active period is of the order of 15 μ sec., and by means of suitable phasing circuits it may be made to coincide with the arrival of any echo of the pulse pattern, causing the ellipses appropriate to that element to appear alone on the cathode-ray tube screen. In polarization measurements a single ellipse is produced on the screen corresponding to the e. m. f. s in two loops at right angles. In directional measurements, the aerials are switched at 25 cyc./sec. by relays so that two ellipses are produced, one representing the phase difference in one pair of spaced frames, and the other that in the other pair. These are separated laterally on the tube by a synchronized magnetic deflecting circuit. The figures are photographed on a moving film, and the ellipses due to each pulse from the transmitte rare thus recorded separately. In this way rapid changes in polarization and direction can be studied. The method has been applied to the various types of ionospheric echo, and records are shown to illustrate their behaviour. In particular it has been used to study the short-lived scatter echoes obtained on high power transmissions, whose characteristics change too rapidly to be followed by manual methods. The results of both polarization and directional measurements are considered in relation to the general problem of ionospheric irregularities.

A comprehensive series of measurements in water phantoms has been made for arc therapy at 250 kV. The dosage distributions have been critically compared with established fixed-field techniques at 250 kV and at supervoltage. The integral doses and skin doses given by these methods are summarised for comparable treatments of the bladder. It is shown to be difficult to obtain such good physical distributions with arc methods as with well-planned fixed fields, and flattening filters and “overlap” of the anterior and posterior arcs are necessary. Where integral dose is a limiting factor, arc methods are generally inferior to fixed fields. Further, the physical distributions of corresponding supervoltage treatments are shown to be greatly superior to stationary or moving fields at 250 kV.

In most of the investigation which have been made on wireless waves reflected from the ionosphere the experiments have been so designed as to provide information concerning the ionization density at different levels. The experimental data sought in such cases are usually critical penetration frequencies and equivalent heights of reflection. If, however, the amplitude of the downcoming waves is also observed, and the total absorption measured, it is possible to obtain information about the frequency of collision between electrons and molecules at different heights in the ionosphere. The measurements described in the present paper have been made so as to provide the latter type of information, and in particular to give evidence concerning the location of that part of the ionosphere which is of importance in producing absorption. For this purpose it is necessary to measure the absolute value of the absorption suffered by the wave, so that results on different wave-lengths may be compared. The methods which we have employed in making these measurements are described in § 2 and the results are discussed in § 4. The theoretical results which are used in § 4 are reviewed shortly in § 3. Most of the measurements discussed in this paper have been made on wave-lengths less than 200 m; a few measurements made with longer waves are discussed in § 6.

An instrument is described which keeps the output of an X-ray therapy tube constant within 1 or 2 per cent. over long periods. The current from an ionization chamber in the tube aperture is amplified and used to operate a relay which controls a regulating transformer in the main power supply line and so corrects variations of output in either direction. Automatic return of the transformer tapping to its mid point, on switching off the X-ray unit, is incorporated.

The instrument described below has been in use at a number of hospitals for the past four years.* It was designed as a sub-standard for calibration of X-ray therapy sets. It has, however, found use in other directions, such as the checking of dosage to points on patients and the measurement of H.V.L. and the plotting of depth dose curves. Its accuracy compares favourably with that of other instruments used for dosage measurements, such as the Victoreen dose meter, and it forms a convenient alternative to this instrument for general use in radiotherapy. The dose meter consists essentially of a thimble ionization chamber on the end of a polythene-insulated cable with the inner electrode of the chamber joined directly to the cable core. The other end of the cable is connected to an electrometer valve with the high insulation core joined to the grid, and the anode current of this valve is observed on a microammeter. The valve is contained in a hermetically sealed box to preserve insulation and an “earthing” s...

For some years the two principal integrating dosemeters used for deep therapy have been the Mekapion and the Hammer. These have a similar design structurally, each comprising a thimble-type ionization chamber which is attached to the instrument head, and which may be placed on the skin of the patient as desired for treatment. Electrical connections from the head to the dial of the instrument serve to operate this latter, which indicates the total dose received. The two dosemeters differ in that the Mekapion incorporates an electrometer valve in the instrument head to operate a relay when a certain charge has been dissipated in the chamber; the Hammer uses an electrostatic relay connected to the central electrode of the chamber which likewise operates the recording mechanism when the charge has dropped to a certain value. Both these instruments have proved themselves capable of reliable working over long periods. An alternative system is therefore put forward only after careful consideration of two factors...

An account is given of investigations into the dosage distribution over an average child's head in the treatment of ringworm by X rays, using a five-field technique. Fair agreement is obtained between experimental and theoretical results, and they indicate that the dose given to some areas of the scalp is about twice that given to other areas. Isodose curves representing the experimental results are drawn on the model head, and have been photographed; a line reproduction of this picture is given. A means whereby such wide variations of dosage might be reduced is suggested.

The general practitioner through his contract with the local Executive Council is responsible for the medical care of a named group of people. Additionally he may from time to time accept responsibility for temporary residents. The average general practitioner has 2,500 to 3,000 patients on his list, and any one of these may consult him at any time. Thus in any general practitioner records system it is necessary to maintain an 'active file' of records available at short notice for all persons registered. This presents a different problem from that of a hospital where most transactions are covered by a relatively small file with very high activity and a large file from which records may be retrieved over a period of hours or days, rather than seconds or minutes. During the course of one year between 8 and 12% of patients registered with the general prac titioner would be expected to leave his list and a similar number will register. Additionally some people who remain registered with the general practitioner will change their addresses, or their names on marriage, so that it is necessary to make these and other amendments to the basic patient record. This paper describes the methodology of setting up a computer-based practice file and of its con tinuous updating. This is the first phase of a feasi bility study to establish an automated computer based records system for administrative and research purposes. Some of the potential rewards of the system are discussed later. No attempt is being made to include records for clinical management in this system, since, as Marinker (1969) has pointed out, the unstructured nature of clinical notes presents the greatest obstacle to the application of electronic methods to data collection.

The sub-standard x-ray dosemeter originally described by Farmer has been improved and modified so that doses may be measured over a range of 1: 105 with the same ionization chamber. Details of circuit modification and the performance of the instrument are described.

X-ray calibrations with ionization chambers are subject to the well-known temperature and pressure corrections which, if not allowed for, can lead to dosage errors of up to 5 per cent. A rise in temperature, lowering the air density, leads to the correction factor (273 + T)/(273 + 22) assuming the instrument has been calibrated at 22°C (T = temperature in °C). Similarly a variation in atmospheric pressure gives the additional factor 760/P (P = pressure in mm Hg). The instrument described here measures directly the combined effect of these two variables.

Conductivity Induced by X-Rays in Polyethylene Terephthalate: A Possible Insulator for Radiological Apparatus

By substituting pure graphite and pure aluminium for the present chamber materials a response curve is achieved which is flat over the therapy range and constant from one instrument to another. The response depends critically on dimensions of the inner electrode and this dependence is studied and illustrated. The insulator (amber) is replaced by PTCFE which has a low induced conductivity under radiation and is chemically pure; it is necessary, however, to reduce the area exposed to the air volume on account of its higher atomic number. This reduction also improves precision of the instrument. Dimensions of the final chamber, which is identical externally to the original chamber, are given.

A critical review is given of the principal machines used for high energy therapy, namely the Resonant Transformer, the 2 MeV Van de Graaff, the Cobalt-60 apparatus, the Linear Accelerator and the main types of Betatron. The latter include the Siemens 15-17 MeV, the Allis Chalmers 24 MeV and the Brown Boveri 31-35 MeV machines. An attempt is made to compare the performance and therapeutic value of the various types of machine and, within approximate limits, arrive at some estimate of their relative cost in treating, for example, an average patient to a tumour dose of 5000 r. This relative cost depends not only on the initial cost of the machine and building but also on the dose rate and ease of setting up, both of which determine the number of patients that can be treated in a day. Broadly, the cost per patient is about the same for the Linear Accelerator and Cobalt Units while that for the Betatron (using x-rays) appears to be considerably higher: this is largely due to its relatively low output of x-rays. Electron therapy, for which the Betatron is admirably suited, has attractive features and the physical characteristics of this form of treatment are discussed. References are given to the principal works on the physical aspects of supervoltage therapy.

Similar observations to those of Bewley (above) have been made with B.D.11 chambers at the Radiotherapy Department, Royal Victoria Infirmary, Newcastle upon Tyne. An electrically driven device was constructed which subjected chambers to repeated shocks of adjustable magnitude and of frequency about 1 per sec. Although chambers differed greatly in their “sensitivity” to shaking, a fairly well defined relationship was observed between charge loss and number of shocks (Fig. 1). The chambers used had polystyrene insulators.

An account, based on four years operation, is given of the first of the 4 MeV linear accelerators (Mullard) installed for medical use. Its “isocentric” mounting in conjunction with the specially designed single-pillar couch makes for rapid and accurate setting up of patients and it may be used for fixed or moving field therapy. The X-ray output is up to 250 r/minute at 100 cm F.S.D. and 400 p.p.s.; the H.V.L. 15·9 mm Cu. A sharp penumbra is obtained through the small focal spot and the use of beam defining diaphragms pivoted at target level. Central axis dosage measurements give a build-up peak at 1 cm depth in water and the dose at 10 cm depth for a 10 × 10 cm field is 62·8 per cent. The surface dose for this same size field is 17 per cent, largely due to secondary electrons from the air. Isodose curves were obtained by direct measurement and also by calculation from the central axis data and some typical curves for oblique fields, fields applied to curved surfaces and wedge fields are also given. The lo...

It is well known that above about 500 kV, the acceleration of electrons by steady d. c. voltages becomes extremely difficult, and the generation of electron beams or X-rays at higher energies has depended largely on the use of multiple acceleration techniques. Of these the Betatron provides the best known example and this has been used very successfully in Germany and elsewhere as a therapeutic instrument. Voltages as high as 20–30 MeV are now readily obtainable.

The problem of eliminating induced conductivity from insulators used in ionization chambers has been recognised for a long time (Farmer, 1945), and it is one of the limiting factors in the accurate measurement of X and γ rays. Hitherto it has been general practice to use amber for the parts of an ionization chamber most heavily exposed to radiation. This induced conductivity has a twofold effect. First, it causes a “leakage” current, during the irradiation, in parallel with the ionization current. This leakage current rises to an equilibrium value in a few seconds or minutes. Secondly, after the end of irradiation the recovery of the insulator is slow and this after-effect may give rise to further serious leakage before the conductivity returns to its normal (static) low value. The “recovery time” for polystyrene is of the order of 100 hours, but depends upon the dose-rate and duration of the irradiation and of course on the level below which the leakage conductivity can be considered negligible. It appea...

A dual purpose laboratory for handling radium containers on the one side and high activity isotopes on the other is described. Master-slave manipulators mounted on an overhead track with motor drive serve most of the radium bench. Sphere units are used only over the sink for washing. A Pantasafe is installed behind the protective wall, and storage drawers for made-up radium are built into the back of the bench. Sterilising by autoclave is carried out before the radium leaves the bench. For this purpose the items are sealed into nylon bags which are finally transferred by a lifting device into a shielded trolley for carriage to the theatre. On the other side provision is made for dispensing of the commonly used isotopes, both sterile and non-sterile, with the minimum of exposure. Calibrations are made with an ionisation chamber behind the protective wall, and solutions are ampouled or bottled and sterilised as required.

Measurements of the primary beam doses have been made with the water phantom at points corresponding to the maternal and foetal gonads and the centre of the foetus in a patient of average thickness in late pregnancy in each of the standard obstetric radiographic projections. Diagrams are provided to show the depth of the gonads from the relevant skin surface so as to provide data by which a direct comparison can be made in departments using a different combination of technical factors.

The technique of measuring the intensity of a beam of X rays at the aperture of a tube has been utilised in some therapy equipments, and a few commercial instruments have been made for this purpose. An instrument of this type has the merit that it allows the tube output to be controlled and maintained constant regardless of changes in mains voltage or in parts of the apparatus such as rectifying valves, which affect critically the X-ray generation. Such instruments have as a rule been somewhat delicate, and do not in general seem to have proved as reliable as is required for clinical work. In view of this and their high cost, their use has been very limited. It seemed, therefore, that some more robust form of meter which was at the same time relatively inexpensive would have a useful application, and would assist considerably in the control of dosage in therapeutic work. Some attempt has been made to meet this need, and it has been found that the instrument described below satisfies the requirements to a ...

Various types of instrument for measuring the strength of γ-ray sources have been developed. In most of these, attention has been given mainly to accuracy of measurement, since, where radium is concerned, the high cost alone necessitates an accurate knowledge of quantities distributed. The fact, also, that the radioactivity is constant and can be marked permanently on any tube (with very slight allowance for decay), gives good reason for measuring, precisely, the strength of any such source. With the increasing use of radon for medical purposes, somewhat different considerations come to the fore. Each “seed” can be used at the most on two or three patients before it degenerates, and a great many more measurements, therefore, are required in relation to a given number of patients treated. The essential need is thus, rather, for a means of determining quickly and simply the content of the tubes to a degree of accuracy appropriate to clinical work, and in a form, preferably, that can be operated by the radil...

THE conductivity induced in unplasticized ‘Perspex’ (polymethylmethacrylate) by X-rays differs markedly from that induced in ordinary plasticized ‘Perspex’. First, the time-constant of recovery after irradiation is very long (several hours) for the unplasticized material, whereas for ordinary ‘Perspex’ it is much shorter1. Secondly, the equilibrium induced current i x is related to the dose-rate R by the general formula: where Δ = 0.55 ± 0.05 for unplasticized ‘Perspex’, but Δ is nearly unity for plasticized ‘Perspex’. These properties place unplasticized ‘Perspex’ in the same class of behaviour as polyethylene1,2, polytetrafluorothene3, and polystyrene4,5.

IN the course of further measurements of conductivity induced in insulating materials by X–rays1,2, we have investigated polytetrafluoroethylene, and find a relatively large induced current with a very long time constant. A small cylindrical condenser 2.5 cm. long with polytetrafluoroethylene as the dielectric medium was used in a vacuum chamber for the measurements during irradiation. The current (down to 10−13 amp.) was measured with a Baldwin ‘Ionex’ Mk3 d.c. amplifier. The X-rays were generated at 220 kVp., with a half-value layer of 1.7 mm. of copper.

MEASUREMENTS of the conductivity induced in insulating materials by X- and γ-rays have shown the existence of a long period decay1, and more recent investigations2–4 have shown that the electron-trapping mechanisms which apply to photoconductivity also apply to these materials. This general picture may enable the energy-level distribution of the material to be elucidated. The present experiments have been concerned with polythene and “Perspex”, and have used a d.c. amplifier to measure the current induced by X-rays of 220 kVP (half-valuelayer = 2.5 mm. copper) both during and after irradiation.

STUDIES of the induced conductivity in insulators due to X-rays1 are difficult owing to the extremely low values to be measured, and hitherto have been made primarily with condenser chambers2. These allow only the after-effect of the radiation to be determined. If measurements of conductivity during exposure are to be made, the apparatus must admit no air gap at any point between the insulator under test and the electrometer, and in addition the volume of insulator irradiated must be as large as possible, so as to give sufficient current for measurement.

THE Van de Graaff high-voltage generator is limited as to its current output by the electrostatic charges which can be carried on moving belts. If a belt could be made to carry charged condensers instead of such surface charges, the current output would become much greater.