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In x-ray phototherapy of brain tumours, the tumour is loaded with iodine and exposed to kilovoltage x-rays. Due to the high photoelectric cross sections of iodine, substantial photoelectric interactions occur. The flux of photoelectrons, characteristic x-rays and Auger electrons produce a localized dose enhancement. A modified computed tomography scanner, CTRx, can be used both for tumour localization and delivery of the dose enhancement therapy. Monte Carlo methods were employed to simulate the treatment of iodinated brain tumours with a CTRx. The calculated results reveal the effect of tumour iodine concentration on dose distribution, the degree of skull bone sparing with the application of multiple arcs, and the homogeneity of tumour dose distribution versus iodine concentration. A comparison with 10 MV stereotactic radiosurgery treatment shows the potential of CTRx treatment relative to conventional treatment modalities.

Brain masses diagnosed in 47 pet dogs as tumors by CT scans, and confirmed in 12 dogs by necropsies, were injected with iodinated contrast media and treated by a modified CT scanner, the CTRx. Twenty-six dogs that received six or more weekly treatments of about 5.6 Gy per fraction, of which about 25% was contributed by radiation from the iodine, for a median total dose of 39 Gy, had a median survival of 230 days. This compares well with the 150 days reported for 25 dogs given 46-48 Gy of cobalt-60 radiation to the whole brain, and is significantly greater than the 6 to 13 days in untreated historic controls.

Introduction To determine the tobacco industry's policy and action with respect to radioactive polonium 210 ((210)Po) in cigarette smoke and to assess the long-term risk of lung cancer caused by alpha particle deposits in the lungs of regular smokers. Methods Analysis of major tobacco industries' internal secret documents on cigarette radioactivity made available online by the Master Settlement Agreement in 1998. Results The documents show that the industry was well aware of the presence of a radioactive substance in tobacco as early as 1959. Furthermore, the industry was not only cognizant of the potential "cancerous growth" in the lungs of regular smokers but also did quantitative radiobiological calculations to estimate the long-term (25 years) lung radiation absorption dose (rad) of ionizing alpha particles emitted from the cigarette smoke. Our own calculations of lung rad of alpha particles match closely the rad estimated by the industry. According to the Environmental Protection Agency, the industry's and our estimate of long-term lung rad of alpha particles causes 120-138 lung cancer deaths per year per 1,000 regular smokers. Acid wash was discovered in 1980 to be highly effectively in removing (210)Po from the tobacco leaves; however, the industry avoided its use for concerns that acid media would ionize nicotine converting it into a poorly absorbable form into the brain of smokers thus depriving them of the much sought after instant "nicotine kick" sensation. Conclusions The evidence of lung cancer risk caused by cigarette smoke radioactivity is compelling enough to warrant its removal.

Ataxia-telangiectasia is a syndrome with many facets, involving a progressive cerebellar ataxia, immunodeficiency, cancer susceptibility, radiosensitivity, defects in DNA repair/processing, chromosomal breakage and rearrangements, elevated serum alphafetoprotein, and premature aging. Ataxia-telangiectasia is an autosomal recessive disorder, rare in outbred populations; carriers of the ataxia-telangiectasia gene may be as common as 1 in 60 and have subclinical radiosensitivity and cancer susceptibility. One estimate suggests that 8.8% of patients with breast cancer could be carriers of ataxia-telangiectasia. These carriers may be responsible for underestimating normal tolerance doses for radiation therapy by 15% to 20%; thus by preselecting and excluding carriers of ataxia-telangiectasia from cohorts of patients with cancer, conventional radiation doses might be increased so as to improve greatly the efficacy of radiotherapy. The genes for the 3 most common ataxia-telangiectasia complementation groups, which include 97% of tested families, have recently been localized to the long arm of chromosome 11.

RATIONALE AND OBJECTIVES The hypothesis that nonionic contrast medium administered during excretory urography may cause cytogenetic damage was tested. METHODS Micronuclei were scored in peripheral blood lymphocytes obtained from 33 patients before and after excretory urography with ioversol, a nonionic contrast medium. RESULTS The examination resulted in a highly significant (sign test, P = .005) increase in the median (range) counts of micronuclei per 1,000 binucleate from 18 (0 to 31) before to 24 (5 to 40) after excretory urography. CONCLUSIONS Nonionic ioversol produces a statistically significant increase in the chromosome damage of lymphocytes from patients undergoing excretory urography. This increase is similar to that reported for the ionic contrast media, ioxaglate and iothalamate, and equal to that produced by 6 to 7 cGy of 100-kilovolt x-rays.

Spontaneous brain tumors in 25 pet dogs were diagnosed and treated with a modified Cr scanner. Five or more weekly 9-Gy fractions resulted in marked clinical improvement in most dogs and a significant decrease in tumor size in many dogs without adverse effects from the radiotherapy.

Norman, A., Cochran, S. T. and Sayre, J. W. Meta-analysis of Increases in Micronuclei in Peripheral Blood Lymphocytes after Angiography or Excretory Urography. Radiat. Res. 155, 740-743 (2001). Meta-analysis of 10 studies confirms a significant increase in the frequency of micronuclei in peripheral blood lymphocytes after angiography or excretory urography; the weighted average increase is 4.2 (95% confidence interval 2.8-5.6) per 1000 binucleate lymphocytes, about the same increase in micronuclei as that produced in vitro by a diagnostic X-ray dose of 4 cGy. The analysis failed to reveal a significant effect of the specific contrast medium used in the X-ray examinations on the increased frequency of micronuclei. These results are consistent with the hypothesis that the effect of the contrast media is limited to the enhancement, by the photoelectric effect, of the X-ray dose absorbed by the lymphocytes irradiated while suspended in the contrast medium. Therefore, an estimate of increased cancer risk based on elevated frequencies of micronuclei or chromosome aberrations in peripheral blood lymphocytes may be greatly exaggerated whenever the radiation damage is largely confined to the cells circulating in the blood, as it is in people who have recently had X-ray examinations that use intravenous injections of contrast medium. Such examinations include angiography, excretory urography and CT scans, which are received annually by millions of people.

Purpose: This Phase I study was designed to evaluate the computed tomography (CT) scanner as a device for radiation therapy of human brain tumors (CTRx). This first use in humans of a modified CT for treatment was founded on extensive research experience with canine tumors. An additional objective was to increase the therapeutic radiation dose to tumors compared to normal tissue by concentration of infused contrast material in tumors, an effect available at diagnostic x-ray energies but not at megavoltage energies. Methods and Materials: A small metastatic brain tumor in each of eight patients received 3–5-weekly fractions of 5 Gy equivalent per fraction from a CT scanner modified to deliver radiation therapy. In each patient, one additional tumor, lying completely outside the volume treated by CTRx, served as a control. The tumor receiving CTRx was treated after infusion of iodinated x-ray contrast media (CM) for dose enhancement. Many of these patients also received conventional 40 Gy whole brain radiation, before, during, or after CTRx treatment. Results: None of the patients showed adverse reactions to the CM or necrosis of the normal brain from the CTRx boost radiation. Monte Carlo calculations of the radiation dose distributions in a model tumor showed that the CTRx irradiation of tumors carrying 10 mg or more of iodine per gram of tumor was as good or better than the dose distribution from conventional 10-MV X-rays. The treated tumor in two of the patients vanished after four treatments, whereas a control tumor in one patient remained constant and grew 4-fold in another patient. Conclusion: The CTRx concept effectively combines a modified CT scanner as a diagnostic device, as a simulator dedicated to radiotherapy, and as a treatment machine. Thus, CTRx could be very useful for radiation oncologists in controlling CM-enhanced and other small brain tumors.

Linoleic acid (LA) administered orally as safflower oil (SFO), which is 76% LA, produced remission in 6 out of 8 dogs with mycosis fungoides (MF). Following each feeding of SFO on 5 successive days to a normal dog peak plasma levels of non-esterified (free) LA in excess of 200 microM were observed. No clinical toxicity was observed from the SFO feedings in the normal or MF animals at the levels of SFO (3 ml/kg) used in these studies. However, a marked rise in white blood cells (WBC) and lymphocytes and a marked transient drop in the serum glutamine transaminases SGOT and SGPT was noted both in the normal and MF animals. These effects of LA may be significant for the remission of MF.

When brain tumours are loaded with iodinated contrast media (CM) and exposed to x-rays, the photoelectrons, Auger electrons and fluorescent x-rays from the iodine enhance the radiation dose absorbed by the tumour. A modified CT scanner, the CTX, can be used to localize the tumour and to deliver the dose enhancement therapy. Monte Carlo calculations are presented here of the central-axis radiation depth dose in a brain containing a tumour loaded with an iodine concentration of 5 mg ml-1 and irradiated with the CTX operated at various kV settings. The dose enhancement factor (DEF) is also calculated for various field sizes and for 5 mg ml-1 of gadolinium in the tumour when the CTX is operated at 140 kV. The calculated values of the DEF are close to published experimental results.

We tested three radiobiologic models, the nominal standard dose (NSD), the biologic index of reaction (BIR), and the linear quadratic (LQ) models to determine which best predicts normal tissue injury in radiation therapy. Clinical data for radiation myelopathy, rib fracture and pericardial effusion were used for all three models to predict injury. We assumed that on the average injuries occurred at higher equivalent doses of radiation than were received by patients who were not injured. We used a t-test to determine whether there were in fact significant differences in the mean values of the equivalent doses among the injured and non-injured. The means were calculated for the four sets of injury by the three models. For the LQ model it was necessary to choose a value for the parameter α β ; the results were not sensitive to the choice over the range of 1 2 to 12 Gy. None of these models showed a significant difference between injured and non-injured patients for all four sets of data. The BIR model showed significant differences in three sets, the LQ model was significant in two and marginally significant in one set, and the NSD was significant in two sets. This analysis illustrates therefore, that the linear quadratic model can be adopted for analysis of clinical data with results that are no worse and possibly better than the NSD model.

Many tumors in the brain and in other tissues can be delineated precisely in images obtained with a CT scanner. After the scan is obtained the patient is taken to another room for radiation therapy and is positioned in the beam with the aid of external markers, simulators or stereotactic devices. This procedure is time consuming and subject to error when precise localization of the beam is desired. The CT scanner itself, with the addition of a collimator, is capable of delivering radiation therapy with great precision without the need for external markers. The patient can be scanned and treated on the same table, the isocenter of the beam can be placed precisely in the center of the lesion, the beam can be restricted to just those planes in which the lesion appears several arcs can be obtained by simply tilting the gantry, and the position of the patient in the beam can be monitored continuously during therapy. We describe here the properties of the CTX, the CT scanner modified for therapy.

Positive lymph modes are a direct demonstration that a specific tumor has been able to metastasize in a specific patient, and the ability to metastasize determines the probability of relapse

The age dependence of poor cosmesis from breast irradiation and the frequency of micronuclei (MN) in buccal cells provide indirect evidence for the presence of a relatively radiosensitive subpopulation of ataxia telangiectasia (AT) heterozygotes in breast cancer patients

We have examined the metabolic behavior of several triiodobenzoic acid derivatives because of the observed mutagenicity and cytotoxicity of 3-amino-5-acetamido-2,4,6-triiodobenzoate (I) and 3,5-diamino-2,4,6-triiodobenzoate (II). Measurements were facilitated using iodine-131 (131I)-labeled compounds. Drug retention in rabbits was monitored with a gamma camera. Metabolic products were studied by column and thin-layer chromatography. 3,5-Diacetamido-2,4,6-triiodobenzoate (diatrizoate) was partially deacetylated by liver microsomes to I and II. II was transformed in part to another substance whose structure remains undetermined. About 1% of nominal doses of I, II, and diatrizoate were retained for several days following intracardiac injection in rabbits. The rabbit did not appreciably acetylate I to diatrizoate and converted some of II to a urinary metabolite which was similar to that formed by liver microsomes. I was present in human urine following excretory urography with diatrizoate, but II was not detected. Manufacturers of diatrizoate should further reduce the level of free aromatic amines in preparations of diatrizoate. A method of doing so is reported.

The loading of tissue with iodine can result in the enhancement of the radiation dose absorbed from low-energy x-ray or gamma ray sources. We have explored the potential of this phenomenon for radiation therapy. We have demonstrated the effect of iodine concentration and radiation quality on this dose enhancement in lymphocytes, we have calculated the effect of such enhancement on depth dose distributions in the brain, we have estimated the iodine content in two human brain tumors during computerized tomography (CT) scans, we have studied the dispersion of the iodine contrast media after direct injection into rabbit tumors, and we have demonstrated that the combination of x-ray and contrast media injection is far more effective than either agent alone in causing the regression of mouse tumors. These results suggest that there may be a therapeutic advantage from loading tumors with iodine and treating them with low-energy photons.

Acentric chromosome fragments produced in cells by irradiation or other agents give rise to micronuclei in daughter cells. The micronuclei can be readily counted in large numbers of cells thereby providing a sensitive measure of chromosome aberrations. Previous studies have shown a consistent elevation of micronuclei count following the use of diatrizoate contrast materials. This study was undertaken to compare the micronuclei counts of patients receiving sodium iothalamate with those receiving sodium diatrizoate. Our results indicate that sodium diatrizoate produced significantly greater cytogenetic damage than the sodium iothalamate agents.

We have adapted a multiparameter cell sorter to measure the distribution of fluorescence polarization in cell populations. Measurements carried out on EL4 cells show that the percent polarization of fluorescein fluorescence decreases with increasing fluorescence intensity. This inverse relationship between polarization and intensity is shown both within the cell population and by the average values of the two quantities during both the increase and decrease of fluorescence intensity. The quantitative relation between intensity and polarization is different in hypertonic than in isotonic media. These results suggest that polarization measurements carried out at a fixed time after incubation of cells with fluorescein diacetate, which is converted to fluorescein within the cells, may depend in part on the rate of fluorescein accumulation, and that agents that have been reported to change the polarization of fluorescein in living cells may do so by changing the kinetics of fluorescein accumulation.

SummaryThe appearance of micronuclei (MN) is delayed with respect to cell division in populations of irradiated human lymphocytes, so that the length of time in culture, as well as the number of divisions, is a factor in MN assays. Using two assays that control for cell kinetics, we measured the yield of cells with MN exposed to graded doses of 60Co gamma rays and 90 KVP X-rays. The yields showed a non-linear increase with dose. They can be represented by two straight lines: the one in the range below 0·15 Gy has a slight slope, the other in the range above 0·15 Gy has a significantly greater slope. The radical scavengers cysteamine and glycerol, which reduced the MN yields sharply at 3 Gy, were less effective at 0·3 Gy, indicating that terminal deletions arising from the direct ionization of DNA are a major source of the MN induced by low radiation doses. It is likely that the non-linear dose response is due to the saturation of a DNA repair process.

Summary Loading tissue with iodine enhances the radiation dose absorbed from low energy X-rays. In order to test whether this is a useful procedure for treating brain tumors, we infused radiographic contrast media into rabbits carrying VX-2 brain tumors and delivered 15 Gy of 120 kVp X-rays in 3 fractions to the tumor. From CT scans we estimated that the dose enhancement was approximately 30%. The median survival times, after tumor detection on CT, of untreated rabbits, treated with radiation alone, and treated with radiation plus contrast media were 3, 25.5, 38.5 days, respectively. The repeated infusion of contrast media, 3.5 g of iodine per kg of body weight, did not affect kidney function as measured by serum creatinine levels. This method of enhancing radiation dose in brain tumors therefore appears promising.

The frequency of micronuclei assayed in lymphocytes obtained from 73 young adults increases significantly with the age, but not the sex, of the donor. The dose of medical X-rays absorbed by the lymphocytes in the 2 years before the examination has no significant effect on micronucleus frequency, provided the data are adjusted for age. However, a small significant increase in frequency is associated with X-ray examinations that involve the injection of contrast media into the blood.

Summary The RBE for 125 I relative to 30 keV X-rays, 4 MeV X-rays and 137 Cs gamma rays was determined using the induction of micronuclei in human lymphocytes as the biological test system. The 125 I photons were as effective as the 30 keV X-rays. If a micronuclei count of 50 per 1500 cells is used as the endpoint, the RBE for 125 I was found to be about 1.8 and 1.6 when 4 MeV X-rays and 137 Cs gamma rays were used as the reference radiation, respectively.

We have found that by increasing the bromodeoxyuridine (BUdR) concentration to 4 × 10−4 M in cultures and using the conventional harlequin staining procedure we can distinguish the proliferating lymphocytes by their blue color from the non-proliferating cells which have red nuclei. The micronuclei (MN) are also blue and are associated with the proliferating cells. The high BUdR concentration does not appear to affect the yield of MN. By scoring the MN only in the (blue) proliferating cells the MN assay is made less sensitive to perturbations in the lymphocyte cultures caused by radiation or by variations in the culture time on PHA concentration. Moreover, the frequency of cells with MN approximately doubles and thus comes into better agreement with the frequency of cells with chromosome aberrations. A better agreement yet can be achieved by correcting the assay for the effect of cell division.

Measurements of the intensity and polarization distributions of fluorescein fluorescence in human lymphocyte populations show changes within minutes after exposure of the cells to the mitogens phytohemagglutinin and Concanavalin A. The distributions of polarization, which before mitogen exposure show essentially a single peak, after exposure develop a second peak at a lower value of polarization. Simultaneously, the intensity distributions show a shift to higher levels of intensity. These shifts can be modeled on the basis of a subpopulation of lymphocytes responding to mitogen. Interpretation of the results is complicated by many factors that may influence the shape of the polarization distributions. In particular we show that the measurements are sensitive to the concentrations of phytohemagglutinin, Concanavalin A, Ca++, K+, fluorescein diacetate, the incubation time and the specific donor. Nevertheless, fluorescein fluorescence measurements provide a rapid and sensitive method for studying the physiology of lymphocytes and for identifying responding lymphocyte subpopulations.

B-mode scans of castor oil in a wedge-shaped container provide gray level maps. The relation between the gray levels and the amounts of absorbing medium can be used to measure the effects of electronic gain, transducer characteristics, and the overall gray level performance of different ultrasound systems. We report results from four units and ten transducers for varying scanning depths.

A new and practical test for evaluating the fertility of a male subject has been developed. Twenty-eight donors whose semen had induced at least one pregnancy resulting in a normal delivery and 61 patients attending our infertility clinic were studied. Semen smears stained with acridine orange were read on a fluorescence microscope; sperm heads appeared either green (fertile) or red ( nonfertile ). We introduce the concept of an "effective sperm count" which is obtained by multiplying the percentage of green-fluorescing sperm by the actual sperm count. Of our fertile subjects, 27 of 28 (96.4%) exhibited an effective sperm count of greater than or equal to 50 million/ml, while 60 of 61 (98.3%) infertile patients fell below this value. The percent green correlates with neither actual sperm count nor motility, indicating that this test measures a new parameter of male fertility.

Polymorphonuclear leucocytes have been induced to synthesize new DNA by exposure to UV light. Preliminary observations (not included) also indicate that 6-MeV electrons and incubation with the radiomimetic agent methyl methanesulfonate (MMS) are effective agents for inducing unscheduled DNA synthesis (UDS). A study of the kinetics of UV-induced DNA synthesis suggests that there are at least two processes operating, one fast and essentially complete within the first 1–2 h and the second lasting at least 8 h. The rapid process can be described by a simple enzyme model using [ 3 H]-thymidine and induced lesions as substrates. A kinetic study of the rapid process, following exposure to UV, yielded values for the maximum velocity of 5.1·10 −21 moles/cell-h and 5.5·10 −20 moles/cell-h for the granulocytes and lymphocytes respectively. The rate constants for the rate-limiting steps were 1.4·10 −1 (min) −1 and 1.1·10 −1 (min) −1 for granulocytes and lymphocytes respectively. Using these values, the concentration of enzyme molecules are estimated to be 4·10 3 molecules/cell for polymorphonuclear leucocytes and 5·10 4 molecules/cell for lymphocytes.

Two strains of TMV that differ markedly in electrophoretic mobility also differ in the magnitude of their electric birefringence. The difference in electric birefringence is due to a difference in the refractive index of the two strains, not to a difference in their electric polarizability. The magnitude of the electric birefringence is dependent on pH, but not in the same way as the mobility. By contrast, the electric birefringence of DNA is independent of pH over the pH range of 5–9.

1. 1. The molecular weight of Escherichia coli freundii hyaluronidase has been determined to be 2.2 × 105 and that of bovine testicular hyaluronidase 7.1 × 104. 2. 2. The x-ray sensitivity of the bacterial enzyme was not altered during its isolation from the cell and subsequent purification. 3. 3. Both the bacterial and the testicular hyaluronidase behave as a single enzyme; i.e., there is no evidence of polydispersity in the inactivation curves.

The kinetics of repair of single-strand breaks induced by 6-MeV electrons in DNA of human lymphocytes was studied using sedimentation-velocity analysis of molecular weights. The rate of repair was found to be rapid initially and essentially constant for the first 20–30 min of incubation at 37°; it then declined markedly. For the rapid initial process the activation energy over the temperature range of 22–37° was 19.1±0.4 kcal/mole, the temperature at maximum rate was about 40°, and the Michaelis-Menten constant, estimated from the rate at V max /2, was approx. 20 krad. These results are similar to those characterizing the rate-limiting step for unscheduled DNA synthesis stimulated by X-rays. Moreover, the number of breaks per rad and the maximum rate of rejoining of single-strand breaks found in this study are similar respectively to the number of lesions per rad and the maximum rate of incorporation of nucleotides per cell found in studies of unscheduled DNA synthesis. It seems likely, therefore, that the repair of single-strand breaks and the incorporation of nucleotides in unscheduled DNA synthesis share the same rate-limiting enzymatic step.

The inactivation of Neurospora conidia by ultraviolet radiation is a consequence of the inactivation of the nuclei. The nuclei exhibit a kinetics of inactivation which is first order with respect to the number of (viable) nuclei. Arguments based on the efficiency of inactivation indicate that only quanta absorbed within a nucleus can lead to its inactivation. There are at least two sets of inactivation processes. One involves the production of lethal mutations, the other is a non-genetic (not inheritable) process. The two processes are apparently intimately connected: they yield the same action spectrum and the effects of each are reduced by photo reactivation. The assumption that the two processes are independent leads to predictions which are at variance with the observed dependence of the frequency of lethal mutations on dose of ultraviolet radiation.

DNA molecules in dilute solution show a marked decrease both in birefringence and in relaxation time (length) when exposed to x-ray doses of a few thousand roentgens. But DNA given 10,000 r. in vivo shows no change in birefringence, length distribution, or kinetics of heat degradation. It appears that DNA in vivo is well protected against the indirect effects of x-rays.

SummaryThe probability of finding a given chromosome in a dicentric is directly proportional to the length of that chromosome at interphase, but not to the length of the early replicating portion of the interphase chromosome or to its length at metaphase. The number of dicentric chromosomes and centric rings per cell is limited primarily by the number of centromeres. These results are consistent with the assumption that every chromosome break is a site for chromosome-exchange.

The frequency of chromosome aberrations in the lymphocytes of 36 hematologically normal women who had received radiation therapy for cervical carcinoma was measured. The decrease with time in the frequency of cells with acentric fragments, of cells with a single dicentric, and of quasidiploid cells can each be represented by a single exponential with an average lifetime, respectively, of 530 ± 64 days, 788 ± 98 days, and 5.55 ± 1.23 x 103 days. Aneuploid cells fall into two classes: One contains no chromosomes with structural aberrations and shows a stable frequency of about 5.8 per cent; the other contains chromosomes with structural aberrations and is eliminated at the same rate as cells with acentric chromosome fragments. The distribution of dicentrics among the lymphocytes at the end of the radiation therapy period is similar to that shown by a population of lymphocytes exposed in vitro to a single dose of about 300 rads.

We have compared three representations of dose-time (or fraction number) relations in radiation therapy on published data for cancer of the breast, Hodgkin's disease, squamous cell carcinoma of the aerodigestive tract, and pericardial effusion. The comparison was on the basis of how well each representation separated the two groups of outcomes, success or failure, in each clinical series. As a measure of separation we have used a dimensionless coefficient and calculated its value as a function of the choice of recovery coefficient in the Strandqvist relations and for the Ellis formula. In general, the Strandqvist relations with an optimal value of the recovery coefficient—defined as that value which produces the maximum separation of the two groups of outcomes—give a better separation than the Ellis formula. Our method of analysis provides a unique procedure for estimating the best value for the recovery coefficient. More importantly, it shows whether the separation is sensitive to the choice of ...

A charged particle passing through water creates a thermal spike, a region of high temperature along the track. The thermal spike expands explosively, thus producing a pressure wave, and then breaks up because of surface tension into discrete regions of water vapor and hydrogen gas. These vapor-gas microbubbles can act as nucleation centers in superheated or gas supersaturated solutions. Calculations based on this thermal spike model are presented of the total energy and minimum linear energy transfer (LET) required to form nucleation centers of a given size, and the calculations are compared to published data on the radiation nucleation of superheated and supersaturated aqueous solutions. Calculations are also presented of the pressure created by the rapid expansion of the thermal spike, and of the lifetime of the vapor-gas microbubbles under conditions in which they collapse. The calculations cover an LET range of 0.1 to 10 Mev/ mu or, approximately, from the maximum LET of recoil protons in water to the maximum LET of fission fragments in water. The calculations are carried out for a liquid pressure of one atmosphere and two temperature conditions: the minimum temperature at which vapor nuclei of given size will grow and 0 deg C. Themore » effect of high pressures and temperatures on the radiation nucleation of vapor bubbles is discussed briefly in terms of the foam limit. (auth)« less

The authors present a comparison of the frequency of dicentrics in human leukocytes irradiated in whole blood in vitro and in vivo. The results indicate that the frequency induced in vivo can be a factor of two higher or lower than the frequency in vitro for the same radiation dose. Whole blood was heparinized and irradiated in plastic bottles at 37° C. immediately after drawing. The oxygen tension in the blood during irradiation was essentially that of normal venous blood. Irradiations were carried out with the x-ray beam from a 6 Mev Linac (effective photon energy about 1.9 Mev) at dose rates of 200 rad/min. and 10 rad/min. The leukocytes were separated from the whole blood and incubated for seventy-two or ninety hours; chromosome preparations were then made in standard fashion. Every metaphase figure was scanned for chromosome aberrations, but tetraploid cells were excluded from the scoring. Data are presented herein for the class of aberrations known as dicentrics only, because these can be readily de...

Chromosomes in the leukocytes from the peripheral blood constitute an almost ideal biological dosimeter: they are readily available for study, they show damage immediately following irradiation, and they also may show radiation changes years after the exposure of the person concerned. The immediate effects are exhibited by cells which were irradiated while circulating in the blood. Since the lifetime of the leukocytes in the blood stream is probably only a few days, the immediate effect should disappear rapidly as they are replaced by new leukocytes. This phenomenon is seen clearly in the work of Tough et al. (1), which showed the disappearance of cells exhibiting radiation damage in a matter of days from the peripheral blood of a patient who received a single dose of partial body irradiation. On the other hand, radiation injury to the precursors of the monocytes and large lymphocytes—the two kinds of leukocyte which can divide—persist probably for the lifetime of the individual. Thus irradiation to the l...

Lymphocytes cultured with 4 X 10(-4) M bromodeoxyuridine (BrdU) and stained by the harlequin procedure show wide variations in the colour and texture of their interphase nuclei. We demonstrate that we are able, by inspection, to identify four sets of nuclei: small dark nuclei (D) in cells that have not transformed in response to mitogenic stimulation; red nuclei (R) in transformed cells that have not synthesized DNA in culture; speckled nuclei (S)--red speckles on a bluish background--in cells that are synthesizing DNA for the first time in culture; blue nuclei (B) in cells that have completed one or more cycles of DNA synthesis. By using this modified harlequin stain to score the fraction of proliferating cells, and using the modified or conventional harlequin stain to determine the relative frequencies of mitotic cells in the first, second, or later divisions, we are able to estimate the fraction of lymphocytes in the original blood sample that can divide in culture. In addition, we show that the technique lends itself to automation. For this we have digitized black and white video images of the cells and extracted features based on the distribution of optical densities in the nuclei. Discriminant analysis carried out on these descriptors resulted in the correct classification of the three major groups R, S and B with an accuracy of 80.3%, 58.5% and 85.1%, respectively.