Pattern of Tubercular Uveitis in Active Pulmonary Tuberculosis.

Ocular tuberculosis is an extra-pulmonary form of systemic Tuberculosis (TB). It is rarely found concomitant with active pulmonary tuberculosis (PTB). The aim of this prospective observational study was to evaluate the pattern of tubercular uveitis (TBU) in the patients with active PTB who attended in our Uvea clinic at NIO&H from July 2018 to December 2020. Active PTB patients who had uveitis consistent with TBU and TBU patients who were confirmed as active lung lesion were included in the study. Chest X-ray, TST, IGRA (QuantiFERON-TB Gold Test), RT PCR of aqueous fluid for tubercular bacillus, Gene Xpert TB test of sputum were done to confirm the diagnosis of ocular and primary TB. If the induration is 15 mm of TST was considered patient in this study. Among 33 patients of active PTB, 4 had TBU (12.12%). Among 48 patients of TBU, 5 had active PTB (10.41%). 13 eyes of 9 patients were affected. Mean age at presentation was 41.8 years. There were anterior uveitis in 23.00% eyes, posterior uveitis in 69% eyes and panuveitis in 7.00% eyes. Choroidal granuloma was the most common presentation of posterior uveitis (46.00%). There were more than 4 times chance to develop choroidal granuloma in patients with active PTB than extrapulmonary TB (Χ²=4.53, <0.05), TBU patients with choroidal granuloma should be evaluated meticulously for active PTB and active PTB patients should be evaluated routinely by ophthalmologist for the search of TBU.

Radiological physics characteristics of the extracted heavy ion beams of the bevatron.

Studies of the depth-ionization properties and the biological effects of heavy ion beams produced at the bevatron have extended work previously done with less energetic beams from other sources. Results indicate that heavy ion beams are suitable for tumor therapy, studies relating to space biology, and fundamental radiobiology.

Ploidy and DNA distribution analysis of spontaneous dog tumors by flow cytometry.

Ploidy and DNA content distributions were measured for 68 biopsy specimens of spontaneous (solid) dog tumors using flow cytometry analysis of mithramycin-stained cells. The tumor ploidy (i.e., DNA index values) ranged from 1.0 to 4.0 (diploid = 1.0), with a mean of 1.4. More than 80% of the tumors had elevated G0-G1 peak DNA contents and were classified heteroploid, similar to human solid tumors. Six mammary carcinomas and osteosarcomas had bimodal G0-G1 peaks. Based on flow cytometric data and pathology criteria, it was observed that: (a) the percentage of tumor S-phase cells tended to increase with increasing DNA index; and (b) for a given DNA index, the percentage of S-phase cells was lower for well-differentiated tumors and higher for poorly differentiated tumors. The inherent scattering of the DNA content and DNA distribution data between different tumor types limited the usefulness of these data for classifying tumors. The results suggest that improved classification of cytologically different tumors and tumor subsets might be achieved by simultaneous flow measurement of DNA content and DNA distribution information with an additional parameter that detects the cytological differentiation state.

Radiobiology of pions at LAMPF.

Recent radiobiology data for pion beams used in therapy are presented. The biological systems used were cultured cells suspended in gelatin and intestinal crypt assay. The importance of fast neutrons from pion stars in large treatment volumes is discussed. The data for compensating the depth dose distribution to produce uniform cell killing across the peak region are presented. The changes in biological effectiveness with peak width for pion beams (unlike heavy ions) are small because of fast neutron contribution from pion stars. The need for innovative radiobiology programs to guide high-LET radiotherapy is discussed.

Biological response across a ridge filter carbon ion Bragg peak.

The dose distribution of carbon ion beams was modified to cover 14 cm peak width using a ridge filter suitable for clinical application. The results of cell survival as a function of depth of penetration of carbon ions and the mouse skin (foot) response at the proximal-, mid-, and distal-peak positions using four daily fractions are reported. The objective of these studies is to verify whether the dose distribution in the peak region is properly compensated to produce uniform biological effect. The implications of the shape of the dose distribution in the peak region to radiotherapy application are discussed.

Biological effects of pion therapy beams: I. Cultured cells.

The results of cell killing by pion beams of different peak widths, ranges and sizes used in therapy are reported. Cultured hamster cells (V79) suspended in gelatin were used. The results indicate that: 1) there are no significant differences in cell-killing between pion beams of different ranges but of the same peak width; 2) there is a slight decrease in biological effectiveness with increasing peak width; and 3) the range-modulation functions used to produce uniform cell-killing are satisfactory for intermediate-range pion beams, but slight corrections may be required for shorter- and longer-range pion beams.

Late effects of fractionated pi-mesons compared to X rays on mouse lung.

Early and late delayed effects of up to 20 fractions of pions and X rays were investigated in the mouse lung. The whole thorax of female CD-1 mice was irradiated under Ethrane/O2 anesthesia. Respiration rate was measured by whole body plethysmography at biweekly to monthly intervals. With signs of irreversible respiratory distress, animals were sacrificed and their lungs evaluated histologically. In addition to the effect of fractionation, the influence of dose-rate and anesthesia was studied as well. The degree of injury for the most predominant lesions (macrophage accumulation, fibrosis, vascular congestion) was scored, and the correlation with the relative change in respiratory rate and survival was analyzed. This analysis showed the primary lesion to be radiation pneumonitis at a median survival time of approximately 100 days. Focal fibrosis was observed to occur soon thereafter, and no evidence was obtained for an independent second wave of fibrotic injury. Fibrosis seemed primarily the result of pathological organization in areas with heavy concentration of macrophages. It was observed that the mice were unusually sensitive, with a single dose X ray ED50/180 of 8.8 Gy. A similar value was found for unanesthetized mice. This might have been the result of performing these studies at an altitude of 2100 m. The fractionation effect also seemed more pronounced, with alpha/beta values of 0.6 Gy for X rays and 4 Gy for pions, which is significantly lower compared to reported values. At the pion dose-rate of 0.25 Gy.min-1, RBE values for single doses were 0.9 when compared to high dose-rate X rays, and 1.36 at equivalent dose rates. This clearly shows that significant repair occurs during the relatively low dose-rate pion irradiations. With smaller doses per fraction, the dose-rate effect became less dominant, and for 20 fractions of pions the RBE was 1.4 compared to fractionated high dose-rate X rays. These RBE's are similar to values reported for acute effects in skin.

Radiobiology of pions in comparison with other heavy particles.

Our recent data on late effects of pions in spinal cord, lung and rectum in rodents is presented with reference to other high-LET radiations. Unlike high-LET radiations such as neutrons and neon ions, the RBE for late effects of pions (up to 1.5) is not found to be significantly different from acute effects. Because of the potential of matching treatment volume (especially by using dynamic treatments) to the target volume by using pions and heavy ions, it is of utmost importance to study the tolerance of normal tissues to late effects as a function of volume. Such knowledge combined with pion and heavy ion dynamic treatment could lead to a further step in heavy particle radiotherapy.

Radiation tolerance of the rat rectum to fractionated X-rays and pi-mesons.

A 2.5 cm segment of the rectum of female F344 rats was irradiated with up to 10 fractions of X-rays or pions. Transient signs of acute proctitis were followed by chronic rectal injury starting at about 2 months. Recto-vaginal fistulas were frequently observed in animals with severe chronic injury. Two patterns of chronic injury were observed, an early type consisting of deep ulcers and fistulas, and a late type characterized by vascular injury, fibrosis and mucosal cysts. In a 4-fraction X-ray experiment, the influence of a low-residue diet was compared with a regular diet, showing no significant differences in pathology or survival. Isoeffective doses were determined for the occurrence of severe rectal injury at 250 days. Fitting the data to an LQ-model yielded an alpha/beta ratio of 13 Gy for pions, and 6.5 Gy for X-rays. Increasing the overall treatment time from 9 days to one month gave a significant rise in isoeffective doses for chronic injury. This suggests that the more delayed types of injury did not develop independently from the acute mucosal changes. The RBE of pions for rectal injury at 250 days was 1.2 for single doses, increasing to about 1.4-1.5 at a dose per fraction of 4 Gy. These values are similar to those obtained in other acute and late responding tissues.

Particle radiotherapy: historical developments and current status.

The current status of particle radiotherapy from a historical perspective is presented. This is done with a personal view and contains personal references and memories during the development of particle radiotherapy. The particles covered are fast neutrons, neutron capture therapy, protons, helium ions, pions and heavy ions. International cooperation in the development of the field of particle therapy, its impact on radiobiology and conventional radiotherapy, and some personal reflections and conclusions are also presented briefly.

Radiobiology of alpha particles. II. Dosimetry of low-energy alpha particles using parallel-plate ionization chambers and a surface barrier detector.

Three small parallel-plate ionization chambers were developed for measuring dose rates, of primarily low-energy alpha particles in the energy range 0.4-3.5 MeV, at a defined cell-Mylar interface. Spectral energy distributions of these alpha particles were also measured at the same position using a specially designed small-area silicon surface barrier detector. Dose rates were derived from the spectral distributions and compared with those derived from the ionization chambers. Different alpha-particle energies were obtained using a 144-MBq 238Pu collimated source and a variety of Mylar moderator foils of different thicknesses. These measurements, extended to mean alpha-particle energies as low as 0.4 MeV, will enable us to correlate radiobiological data with effects of alpha particles terminating in different regions of cell nuclei.

Residual radiation damage in the mouse foot after exposure to argon ions and retreatment with X rays.

The results of radiation treatment as visible residual damage are reported for acute skin reaction and foot deformity in mice exposed to argon ions. Two groups of 40 mice each were exposed to argon ions at the plateau and peak center of a 10-cm-wide Bragg peak to a fixed dose of 1200 and 1300 rad, respectively. A third group of 40 mice was exposed to 1750 rad of 250-kVp X rays while the fourth group was kept as controls. The acute skin reactions were scored for 60 days and foot deformity at 8 months after exposure. These mice were reexposed 8 months after the first exposure to graded doses of X rays ranging from 1200 to 2500 rad. Acute skin reactions were scored again for 60 days and foot deformity 8 months after the second exposure to graded doses of X rays. The results showed that no significant visible residual damage of the first treatment of either argon ions or X rays was observed after a second irradiation with X rays for acute skin reaction. For the end point deformity, however, residual damage of the first treatment was observed. The residual damage for foot deformity for argon ions does not seem to be higher than for X rays when the doses of first treatment with argon ions and X rays were matched to produce nearly uniform effect. The results also suggest a threshold dose to show the residual damage of the first treatment.

Oxygen enhancement ratio as a function of dose and cell cycle phase for radiation-resistant and sensitive CHO cells.

There is still controversy over whether the oxygen enhancement ratio (OER) varies as a function of dose and cell cycle phase. In the present study, the OER has been measured as a function of survival level and cell cycle phase using volume flow cell sorting. This method allows both the separation of cells in different stages of the cycle from an asynchronously growing population, and the precise plating of cells for accurate measurements at high survival levels. We have developed a cell suspension gassing and sampling system which maintained an oxygen tension less than 20 ppm throughout a series of sequential radiation doses. For both radiation-resistant cells (CHO-K1) and a radiation-sensitive clone (CHO-xrs6), we could separate relatively pure populations of G1-phase, G1/S-boundary, S-, and G2-phase cells. Each cell line showed a typical age response, with cells at the G1/S-phase boundary being 4 (CHO-K1) to 12 (CHO-xrs6) times more sensitive than cells in the late S phase. For both cell lines, G1-phase cells had an OER of 2.3-2.4, compared to an OER of 2.8-2.9 for S-phase and 2.6-2.7 for G2-phase cells. None of these age fractions showed a dependence of OER on survival level. Asynchronously growing cells or cells at the G1/S-phase boundary had an OER similar to that of G1-phase cells at high survival levels, but the OER increased with decreasing survival level to a value near that of S-phase cells. These results suggest that the decrease in OER at high survival levels for asynchronous cells may be due to differences in the OERs of the inherent cell age subpopulations. For cells in one cell cycle stage, oxygen appears to have a purely dose-modifying effect.

Radiobiology of alpha particles. III. Cell inactivation by alpha-particle traversals of the cell nucleus.

Cell inactivation after exposure to collimated 3.5-MeV alpha particles in three hamster cell lines, V79, CHO-10B, and HS-23, one mouse cell line, C3H 10T1/2, and a human skin fibroblast cell line were studied. Several parameters were investigated for each cell line. Theoretical calculations were performed to find the distribution of energy deposited in the nuclear volume for each cell line. The mean number of alpha-particle traversals required to induce a lethal lesion varied between two for HS-23 cells and six for C3H 10T1/2 cells. The number of traversals per unit area and the total track length of alpha particles that inactivated a cell were found to be nearly constant for the hamster and mouse cell lines. These quantities were found to be lower for the human skin fibroblast cell line. The RBE values for all cell lines were found to be about 3.8 at 10% survival. Thus cell lines that are more sensitive to alpha radiation are also more sensitive to gamma radiation. The average number of alpha-particle traversals producing a single lethal lesion is greater than one. The passages of alpha particles through the cell nucleus that do not kill the cell may lead to carcinogenic effects.

Coulter volume cell sorting to improve the precision of radiation survival assays.

A new method for measuring cell survival at low doses of ionizing radiation has been developed through the use of flow cytometric cell sorting on the basis of Coulter volume signals. The cell sorter is capable of deflecting a precisely known number of cells directly into culture dishes, thus eliminating any errors associated with cell dilution and volume sampling. The use of Coulter volume signals as the sorting parameter is shown to be noncytotoxic for a variety of cell lines. Comparison of radiation survival curves measured above the 10% survival level by either the cell sorter or standard dilution assay demonstrates the increased precision of the cell sorter technique . Because of these advantages of cell sorting over conventional methods of plating cells, this technique has many applications in the field of radiation biology and other studies of cell survival.

Flow cytometric determination of radiation-induced chromosome damage and its correlation with cell survival.

Chinese hamster M3-1 cells were irradiated with several doses of X rays or alpha particles from 238Pu. Propidium iodide-stained chromosome suspensions were prepared at different times after irradiation; cells were also assayed for survival. The DNA histograms of these chromosomes showed increased background counts with increased doses of radiation. This increase in background was cell-cycle dependent and was correlated with cell survival. The correlation between radiation-induced chromosome damage and cell survival was the same for X rays and alpha particles. Data are presented which indicate that flow cytometric analysis of chromosomes of irradiated cell populations can be a useful adjunct to classical cytogenic analysis of irradiation-induced chromosomal damage by virtue of its ability to express and measure chromosomal damage not seen by classical cytogenic methods.

Radiobiology of alpha particles. IV. Cell inactivation by alpha particles of energies 0.4-3.5 MeV.

In this report the effectiveness of low-energy alpha particles in the range 0.4 to 3.5 MeV for cell killing is investigated. Four cell lines of different nuclear dimensions (AG1522, C3H 10T1/2, CHO-10B, and HS-23) are studied. Monte Carlo simulations are carried out to interpret the experimental results. They are presented as a function of dose to the nucleus, the total track length of alpha particles in the nucleus, and other parameters. It is found that the effectiveness of alpha particles for cell killing decreases with decreasing alpha-particle energy. The maximum RBE value is found to extend to LET values as high as 180 keV/microns. Although the LET might be the same, the effectiveness of alpha particles for cell killing is higher in the ascending part of the Bragg curve compared to descending part of the Bragg curve. The terminal tracks of alpha particles are observed to be less effective for cell killing.

Radiobiology of ultrasoft X rays. V. Modification of cell inactivation by dimethyl sulfoxide.

The effects of the radioprotector dimethyl sulfoxide (DMSO) were investigated for carbon-K (0.28 keV) and aluminum-K (1.47 keV) X rays compared with 60Co gamma rays for inactivation of mouse C3H 10T1/2 cells. The protection factor for 2 M DMSO was found to be 2.8 for both of the ultrasoft X-ray energies, which is not significantly different from the protection factor of 2.6 found for gamma rays. The results indicate that the proportion of scavengeable lethal damage from gamma and X rays does not depend on the proportion of the total energy that is deposited by low-energy electrons of relatively high ionization density.

Radiobiology of alpha particles. I. Exposure system and dosimetry.

A 238Pu alpha-particle exposure apparatus was designed and constructed for use in radiobiological studies with cultured cell systems. The system provides a wide dynamic range of absorbed doses and a uniform radiation field. Average dose rate in air was measured with a small-volume ionization chamber. Estimates of dose rate at the cell surface were obtained from measurements taken with a silicon surface barrier detector. Particle fluence uniformity and fluence rate were measured using track etch procedures. The design and dosimetric characterization of the apparatus are discussed.

Response of X-ray-sensitive CHO mutant cells (xrs-6c) to radiation. II. Relationship between cell survival and the induction of chromosomal damage with low doses of alpha particles.

The induction of cytotoxicity, chromosomal aberrations, and sister chromatid exchanges (SCEs) was measured in CHO K-1c cells and in isogenic X-ray-sensitive mutant xrs-6c cells that had been irradiated with X rays and alpha particles in isoleucine-deficient alpha-minimal essential medium in G1 phase of the cell cycle. There was a noticeable shoulder region on the survival curve for CHO K-1c cells irradiated with very low doses of alpha particles, whereas this feature was absent for xrs-6c cells with alpha-particle doses as low as 0.5 cGy. Higher frequencies of chromatid-type aberrations were induced in G1-phase xrs-6c cells than in G1-phase CHO K-1c cells by both gamma- and alpha-particle irradiation. Induction of nonlethal chromosomal aberrations was observed following exposure to 2-6 cGy of alpha particles, doses yielding 97-100% cell survival. Irradiation with 0.5 cGy of alpha particles induced SCE; nearly 60% of irradiated cells contained significantly increased levels of SCE. However, only 3% of the nuclei of cells exposed to 0.5 cGy of alpha-particle radiation were actually traversed by an alpha particle. The observation that a large fraction of cells apparently survive exposure to very low doses of alpha-particle radiation with persistent genetic damage manifested by both chromosomal aberrations and SCEs may have important implications for the carcinogenic hazards of high-LET radiation.