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Department of Radiolow Robert 5. Stone, M.D. Director Glil D. Adams, Ph. 0. Assoc. Mrector
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C. Power Supply and Control I. Animal Breeding and Care 5 A. Theory and man c B. Four Standardized RBE Tests .-c 11. RBE Tests and Biological callbration of Synchrotron g C. Other BBE Tests 111. Reaction as a Function of Total Dose, Dose-Rote, and IV.- Antagonists and Synergists
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Spem Collections Llbrary. San Francisco CA FILE CODE NO Blood Platelet Counting i n the Hemacytometer Investigation of New Equipat f o r Direct Platelet Review of Studies With 20-Micron Chamber Calibration of t h e %Micron Shallow Chamber Investigation of Effects of Surface Conditions Investigation of Probable Causes of Variability The Effect of IID on t h e Bone Marrow Grading of Marrow and Blood A. Cellularity of Bone Mamow B. Differential Counts of Bone Marrow Grouping of Bone Marrow Specimens by Differential Count and Cellularity Correlation Between PeripherPl Blood and Bone Correlation Between Amount of 1131 Administered and Bone Marrow Findings Progressive Changes in Blood and Bone Marrow I. Cancer of t h e Thyroid Thyroid Physiology and 1131Metabolism Histolo i c Changes in the Thpoid Due t o Radiatian Follow-Up of Patients Treated with Radioiodine B. Hypothyroidism After Radioiodine Therapy Recurrence of Hyperthyroidism m e r Radioiodine Smary of lkperience with Radioiodine Treatment
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The Radiological Laboratory is the name which been 8PpBed. t o the coalition of research activities deemed necessary for the physical, biological, and cU.nicrl evaluation of the radiations obt-able from a 70 Nev synchrotron. activities of a radioiodine project and a total-body-irradiation h a building constructed and equipped by the University of Calif d. with funds provided by the U. 5. Atomic Energy Commission, which agency a l s o supports most of the research program. The work I s unclasaifled and relates to the bprwemsnt O f radiation therapy of cancer. Uhile the study of the value of the synchrotron aa a t o o l for the treatment of cancer is the main objective, the theoretical and practical value of chauging other treatment factors such as doae-rate and fractionation i s being current experimental program. It rlso includes the ted th g The major part of them activities are housed This annual report cw ers all aspects of the laboratory's
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Special Coiiectmns L:brary. San Francisco CA A Fhysics Section vas established in the Radiological Laboratory for t h e physical evaluation of the radiations produced by the 70 MeV synckotron. Its duties are: develop means for making the synchrotron usable for the programs of the Biology Section and the Clinical Section; (3) t o evaluate &nd to interpret doses of radiation delivered by the synchrotron, particularly in rel a tim t o doses of x-radiation delivered at conventional voltages. The synchrotron was accepted from the manufacturer on July 1, 1952 as meeting factory operating specifications, although it was clearly not capable of clinical use. Three major development problems have consumed and continue t o consume a large amount of time, resulting i n considerable delay in the experimental program. These problems are: (1)devising means t o support the vacuum tube andfor ways t o build the electron injector structure t o pennit the continuous use of one injector fora substantial number of operating hours; ( 2 ) engineering of the vacuum pumping system; and (3) devising means for supporting a field-flattening filter which will permit the natural variations of the x-ray beam t o be conpensated f o r all angulations available t o the x-ray beam. by this section during 1953. (1)t o operate and maiqtain the synchrotron; (2) t o Sane experimental work has been dovetailed i n t o the synchrotron The following is an accounting by category of progress I. Synchrotron Magnet and Related Equipment. A. Vibration. As reported for 1952 and by steps sketched i n t h e report for that year, a sufficient degree of protection seems now t o have been provided, largely by rugged design of injector structure. jectors were consumed during 1953, but the machine was not in operation during eight months of the year. impression me vacuum system supplied with the synchrotron. The basic, underlying principles of operation and control are good but the engineering reduction t o practice is poor, haphazard, and not at a l l well thought out. Revisions in 1953 worthy of note are: (1) The hydraulic vacuum valves functicrn erratically. The General Electric Company installed a water pressure booster pump hoping to palliate this situation, without too much SUCCBSS. development by this section of a rotating O-ring seal as replacement. i s capable of satisfactory operation. engineer in our laboratory for some weeks t o employ their recammended techniques, no discernible improvement Over o u r standard methods was demonstrable. annoyance of component malfunction, i s submarginal pumping speed. 300 liter per second diffusion pump is connected tothe donut by a pipe B. Vacuum System. The test of. time leaves one with the followbg (2)A long sylphon vas provided to flex as the x-ray beam i s mguFatigue-failure of the wall material of this sylphon ledto the (3) The General Electric Company maintains that the qv&em supplied Although they supported a field
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Speclai Co~:ec:~onsLibrary. San Francisco CA exceed 10 U tera per secoaa, inadequacy can be jaiged on the follcrving scores: ed at the donut c m m + o be inadequate. Tho (1) hr i uga single run, pressure rise is seen and s-taneously ht gassing the cathode of a new injector requims 8eVerol The in it lit pmp-down t o an operating vacuum satisfactory the x-ray output decreases by perhaps 30 der cent. hours) tbanty minutes should be sufficient. for therapy requires as least me night. down-time f o r replacing an injector should not exceed two hours. redesign the vacuum system so as t o obtain a considerably increased pwrplng speed atthe donut. I n this new design the diffusion p q vill be mounted on the nagnet and as close t o the donut as the mimet superstrusture will pemit. Huch of the material i s on hand and shop work Is proceeding. (3) It is felt that the total Considering a l l these points, the decision has been made t o C. Cowensation. The natural x-ray beam produced by t h e synchrotron is peaked so much that the full angular width a t halfmd mn intensity is only about two degrees of arc. Thus, if a 1s CP diameter field at two meters from the target uere t o be used, the x-ray intensity at the edge vould be about 20 per cent of the central t o be used should be unifonu i n intensity. approldmately conlcal in shape, which preferentially absorb t h e intense portions of the beam and which therefore provide x-ray f i e l d s which are unlforrn within a feu per cent. It has been decided that the first x-ray field Filters have been conetructsd, If the synchrotron were mounted so as t o produce a horizontal x-ray beam there would be no essential problem in mounting this f i e l d compensation filter. kt readily discernible field intensity chaqges occur for motions of a few thousandths of an inch of the filter reo - ti veto the x-ray beam, and for most mounting methods investigated the actual relative motion i S many times this. apparently induced by various portions of the massive magnet s t w c - ture sagging i n various directiona as the magnet i 8 angulated, changing the beam direction from horizontal to vertical. These notions are It has been found thata possible arrangement isto mount the filter directly on the donut and then t o secure the donut t o an existing central structure of the magnet system. remaining beam shift with angulation was finally traced t o motion of copper vires inthe main exciting coils of the synchrotron. coils were then remwed and completely rebuilt by the General Blectric Company. Upon re-installation of these coils, the evaluation vas continued Mth encouraging first results), but before it could be This has been tried, and
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ecrrring scheme broke and wed t o be a series of Alternate means for sapportcracks i n the porcelain wall of the donut. are currently under consideration b u t evaluation i s not possible yet. Simultaneously a system involving apair of s emo mecha ni ~i s being deelgned which will be able t o sense relative shifts between tbe beam and its compensating filter and to automatically and continuously odjast the filter position so as to ndr hl ze this shift. t h a t the camplicition of auch a device should not be added unless the only alternative solution seems t o involve too large a risk, aa in the cracking of the donut. ing procedures were started towards Pcquiring a spare x-ray donut from the General Electric Company t o cover the eventuality of loss of t h e existing donut. The cracks in the donut, mentioned above, appeared in May, and since the C o m p w was unable t o supply the spare tube, they elected t o attempt the repair of these cracks. Six months and several individual repair efforts later, including the final two at cisco, an operating vacuum was obtained. made vhile this interim solution i s the only one available. close of the year, t h e spare donut has not been delivered. the manufacturer, because of the great cost of purchasing from him, and because personnel of this laboratory possess skill and experience i n donut manufacture, this laboratory has decided t o process its own tubes t o assure a future supply. Towards this end a design has been made which should be useful whether producing x-rays or an external electron beam. A local miuiufacturer of porcelain products has been found who i s willing to cast some porcelain envelopes, and one such envelope has been delivered f o r inspection and vacuum testing. The result to date I s very prod sing and other necessary processing materials are being specified f o r purchase. It is recognized Some beam atudies are being Because of the great delay I n acquiring a replacement donut from A. Badiofreauencs Svstem. The large scale revision of t h i s unit completed l a s t year has not required further revision. a frequency drift vith operating time during a given day has been noted, and there is superficial appearance of a concamitant decrease B. X-Ray Monitor. A s mentioned i n previous reports, the time duration (width) of t h e x-ray pulse fran the synchrotron depends on the phase of x-ray production and may be -here In the range 10 to LOO ps. It has been reported also that t h e apparent yield, as judged by t h e monitor ionization chamber supplied, was a function of pulee width. Following t h e work of Boag (1, 2) t h e response of this chamber was found t o be limited by the inefficiency of collection of the ions formed i n the chamber. Thus, for a typical pulse width of 150 ps and
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tion efficiency is only esigned into the same external geometry a s that originally supplied which has a minimum collection efficisncy of about 98 po,r cent. It is essentially a multi-plate ionzzation chanter with yard ring technique and vith2 categsry, one of which has been resolved. for powering the synchrotron was 50 h a . t o factory specifications but, in fact, vas inadequate. A new transfomer, new and h e a d e r wire, and neu swcltchgear have been installed, largely by the General Electric Company. Testing of this monitor has iust started. C. Power Supply aad Control. Two problems ef is ted this The installed capacity This was correct according The other problem relates to maintaidng the synchrotron in a particular operating condition when once attained. x-ray run, magnet heating changes the electrical inductance monotonically and requires cltimately a change i n the associated capacitance i n order t o maintain resonance. The capacitance steps provided were found adequate from the viewpoint of electrical practice but are too large by perhapa a factor of three for t h e more stringent operational requirments of therapy. designed into the resonant circuit with smaller capacitance steps and most of the material needed for incorporation of t h i s revision has An additional switching arrangement has been 111. Experiments Involving X-Radiati on. A. gxDosure Intepration. The monitor chamber mentioned above i s expected t o be the first step i n an ionization method for integrating total exposures in spite of the pulsed nature of the x-rays produced and of amplitude variations of t h e many pulses fonuing the vity induced i n metallic foils continues t o be the available method for evaluating total exposure. Until this development can be completed, radioactiI n the past, the amount of induced actiVity has been read by large end-window Geiger counters, but there has been suspicion of nonuniform sensitivity throughout a day's operation. Counting a longlived source with a typical time schedule f o r a day's operation repeatedly showed decrease insensitivity of 5 per cent or so for these counters with almost complete recovery overnight, t h e morningto-morning decrease averaglng about 0.5 per cent. photomultiplier with an anthracene crystal attached was evaluated under the same circumstances. A continuous &day run with autmp recording of the counting rate showed a variation not exceeding - 1 This system will be used for future biological irradiations. B. Use of Photomaphic Films. It has been houn for some time that, under favorable conditions, certain types of x-ray films atre
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particularly useful f o r diff ry. A standard exposure of the film (Eastman Industrial, Tppe M) , using 250 h constant potential x-rays and a copper stepwedge, was used to test various aspects of the emulsion response and development procedure, Having chosen 10 minutes aa the standard dsvelopmant the a t 65' F in D19b, it was found that under or overexposure by a factor of two could be compensated within 10 per cent by over or underdevelqment by the reciprocal factor. It was a l s o found that, after constmcting an automatic, motor-driven device t o circulate the developing solution and simultaneously create turbulence in the tank, densities developed for a given exposure were practically independent of position of the film in the tank, b u t were in any case sensitive t o changes i n developer temperature. In fact, density changes of 5to 10 per cent were found per degree Fahrenheit change f o r a given exposure. In spite of thep precautions, there remain variations i n density of the order of - 5 per cent, part of uhich is between films and part of which …
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