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At least 19 recordsLinked to original sources
PubMed1996

Micronucleus induction in human lymphocytes: comparative effects of X rays, alpha particles, beta particles and neutrons and implications for biological dosimetry.

The cytokinesis-block micronucleus assay in peripheral blood lymphocytes has the potential for being a simple and rapid method of biological dosimetry. This technique has been used to study the induction of micronuclei in the blood from 12 donors after exposure to a range of radiations with track-averaged LET values ranging from 0.26 to 44 keV microns -1. Data based on the average response of the 12 individuals for 250 kVp X rays were found to agree well with results published previously from other laboratories using similar techniques. Low dose-limiting RBE values relative to 250 kVp X rays for the radiations studied were found to be 0.50 for strontium/yttrium-90 beta particles, 6.9 for 20-23 keV microns -1 alpha particles and 17 for 24 keV neutrons. The pattern of the variation of individual radiosensitivity was found to be complex and dependent on dose, and the evaluation of individual radiosensitivity based on the response at one dose only can be misleading. It is concluded that, although the cytokinesis-block micronucleus assay in blood lymphocytes is a radiobiologically appropriate technique to use for biological dosimetry, its practical implementation may be limited by a need to perform individual pre-exposure calibrations.

Adult↗
PubMed1999

Comparative stochastic effects of inhaled alpha- and beta-particle-emitting radionuclides in beagle dogs.

The stochastic effects of inhaled, insoluble particles of alpha- or beta-particle-emitting radionuclides were compared in dogs. Male and female beagle dogs were exposed briefly by nasal inhalation to relatively insoluble aerosols of (239)PuO(2) or (144)Ce in fused aluminosilicate particles (FAP) and observed for cancer for their lifetimes. The initial lung burden and retention of each radionuclide was determined by whole-body counting of the emissions from (144)Ce-(144)Pr- or (169)Yb-labeled (239)PuO(2). Lung doses were calculated for each dog from these data. The lung doses ranged from 0.21 to 1200 Gy for (144)Ce FAP and 1.6 to 58 Gy for (239)PuO(2). Dogs with doses to the lung of about 60 Gy or greater from (144)Ce or about 2 Gy or greater from (239)PuO(2) had an increased incidence of lung carcinomas. In dogs exposed to (144)Ce FAP, three organs were targets for neoplasia: lung, tracheobronchial lymph nodes, and heart. The insoluble FAP carried to the lymph nodes draining the lung delivered high radiation doses to the nodes and adjacent heart, resulting in hemangiosarcomas of these organs. In the lung, high radiation doses induced hemangiosarcomas and carcinosarcomas. At lower doses, carcinomas of various histological patterns were induced in the lung. In dogs exposed to (239)PuO(2), the lung was the sole target organ for neoplasia. Nearly all of these neoplasms were carcinomas of various histological patterns. These results indicated that relatively low doses of alpha-particle radiation can induce pulmonary cancers, but relatively large doses of beta-particle radiation are required. In addition, inhaled beta-particle emitters can also induce cancers in lung-associated lymph nodes and heart at these larger absorbed radiation doses.

Administration, Inhalation↗
PubMedDate not supplied

Tumor dosimetry in radioimmunotherapy: methods of calculation for beta particles.

Calculational methods of beta-particle dosimetry in radioimmunotherapy (RIT) are reviewed for clinical and experimental studies and computer modeling of tumors. In clinical studies, absorbed-dose estimates are usually based on the in-vivo quantitation of the activity in tumors from gamma camera images. Because of the limited spatial resolution of gamma cameras, clinical dosimetry is necessarily limited to the macroscopic level (macrodosimetry) and the MIRD formalism for absorbed-dose calculations is appropriate. In experimental RIT, tumor dimensions are often comparable to or smaller than the beta-particle range of commonly used radionuclides (for example, 131I, 67Cu, 186Re, 188Re, 90Y) and deviations from the equilibrium dose must be taken into account in absorbed-dose calculations. Additionally, if small tumors are growing rapidly at the time of RIT, the effects of tumor growth will need to be included in absorbed-dose estimates. In computer modeling of absorbed-dose distributions, analytical, numerical, and Monte Carlo methods have been used to investigate the consequences of uniform and nonuniform activity distributions and the effects of inhomogeneous media. Measurements and calculations of the local absorbed dose at the multicellular level have shown that variations in this dose are large. Knowledge of the absorbed dose is essential for any form of radiotherapy. Therefore, it is important that clinical, experimental, and theoretical investigations continue to provide information on tumor dosimetry that is necessary for a better understanding of the radiobiological effects of RIT.

Beta Particles↗
PubMed1985

Effect of air-scattered beta particles on instrument and dosimeter response.

Air-scattered beta particles are responsible for many of the inaccuracies encountered when readings are obtained with many types of beta survey instruments and personnel dosimeters. The ratio of beta particles scattered at various angles to beta's coming directly from the source increases as the distance from the source increases. This ratio, at a given distance from the source, is also a function of the beta energy, becoming larger for lower-energy beta sources. Changes in this ratio cause the response of beta instruments to have an apparent change in the directional response. These air-scattered beta particles are also responsible, in many cases, for a part of the apparent decrease in the efficiency of beta survey instruments when detecting low-energy beta sources. Air-scattered beta's also cause personnel dosimeters, which are not properly designed to detect them, to have responses that are low. We give experimental results to confirms the above effects. Design changes to survey instruments and dosimeters are suggested that would eliminate the errors created by the failure of the instruments to detect these air-scattered beta particles.

Air↗
PubMed1997

Beta particle attenuation characteristics of CaSO4.

The beta particle mass attenuation coefficient for CaSO4 in a Teflon matrix has been estimated by two methods: an experiment using collimated sources and a collimated gas flow proportional counter and simulations using the EGS4 Monte Carlo code. The attenuation coefficient has been cast in the general form of mu/rho = aE(-b), where E is the maximum beta particle energy and a and b are fitting parameters. The a and b parameters are given as a function of the atomic number of the material.

Beta Particles↗
PubMed1994

A unified approach to photon and beta particle dosimetry.

UNLABELLED: The purpose of this investigation was to develop a unified and practical method for photon and beta particle dosimetry. METHODS: This was achieved by developing a point-source function that is equally valid for photons and beta particles. This function contains four fitting parameters. These were computed on the basis of Berger's tables for a wide range of photon and beta particle energies. Explicit formulas were derived for the absorbed fraction within and outside of spheres containing a uniform distribution of activity. For photons, calculations of the absorbed fraction at the center of spheres were compared with the results of Monte Carlo calculations. The two methods yielded essentially identical results, validating the approach used in this study. RESULTS: The results of this study show that there are absorbed-dose gradients as a function of distance from the center of a sphere. These should be taken into account in absorbed-dose calculations. For beta particles, it is shown explicitly that for spheres with a radius of 0.08 cm, absorbed-dose rates from 131I and 90Y beta particles are equal. CONCLUSION: An important feature of this work is that calculations can be made on the macroscopic, cellular and subcellular levels. The approach employed and results obtained in this work should be particularly useful for tumor dosimetry in radionuclide therapy and applicable radiobiological investigations.

Beta Particles↗
PubMed2002

On (3)H beta-particle and (60)Co gamma irradiation of aqueous systems.

The chemistry of water and aqueous solutions is very different after irradiation with (3)H beta particles and high-energy electrons or (60)Co gamma rays. The greater the linear energy transfer (LET) of the medium for (3)H beta particles compared to high-energy electrons or (60)Co gamma rays leads to an increased local concentration of reactants. There is an increased amount of intratrack chemistry, which reduces the escape yield of and OH by about 50%, but increases the yield of H(2) by about 50% and of H(2)O(2) by about 35%. Analysis of stochastic-diffusion kinetic calculations employing simulated track structures reveals that the yield of H(2) produced by diffusion-kinetic processes increases significantly for (3)H beta particles compared to (60)Co gamma radiation, while production of H(2) by sub-picosecond processes is essentially the same. In both (3)H beta-particle and (60)Co gamma radiolysis, the reactions + and are equally important in the production of H(2). In the former case, each reaction has a yield of approximately 0.18, and in the latter a yield of approximately 0.08. In neutral water, the reaction (H + H) is negligible. The yield of Fe(III) in (3)H beta-particle radiolysis of the Fricke dosimeter is much smaller than in radiolysis with more energetic electrons. Simulations show that this change is primarily due to the reduced escape yield of H, formed from the scavenging of by the bulk H(3)O(+) of the acid. The chemical differences observed in experiments, and in calculations, reflect the underlying structure of the electron tracks: Examination of the track structure simulations demonstrates that primary events are considerably more well-separated in high-energy electron tracks compared to (3)H beta-particle tracks.

Beta Particles↗
PubMed1996

Pulmonary carcinogenicity of relatively low doses of beta-particle radiation from inhaled 144CeO2 in rats.

This study was conducted to examine the carcinogenic effects of inhaled beta-particle-emitting radionuclides, particularly in lower dose regions in which there were substantial uncertainties associated with available information. A total of 2751 F344/N rats (1358 males and 1393 females) approximately 12 weeks of age at exposure were used. Of these, 1059 rats were exposed to aerosols of 144CeO2 to achieve mean desired initial lung burdens (ILBs) of 18 kBq (low level), 247 rats to achieve mean ILBs of 60 kBq (medium level) and 381 rats to achieve mean ILBs of 180 kBq (high level). Control rats (total of 1064) were exposed to aerosols of stable CeO2. Based on the 95% confidence intervals of the median survival times and the cumulative survival curves, there were no significant differences in the survival of groups of female and male exposed rats relative to controls. The mean lifetime beta-particle doses to the lungs of the rats in the four groups were: low level, 3.6 +/- 1.3 (+/-SD) Gy; medium level, 12 +/- 4.5 Gy; and high level, 37 +/- 5.9 Gy. The crude incidence of lung neoplasms increased linearly with increasing doses to the lungs (controls, 0.57%; low level, 2.0%; medium level, 6.1%; and high level, 19%). The estimated linear risk coefficients for lung neoplasms per unit of dose to the lung were not significantly different for the three dose levels studied. The risk coefficient at the lower level was 39 +/- 14 (+/-SE) excess lung neoplasms per 10(4) rat Gy; at the medium level the risk was 47 +/- 12; and at the higher level the risk was 50 +/- 9.0. The relationship of beta-particle dose to the lung and the crude incidence of lung neoplasms was described adequately by a linear function. We concluded that the risk of lung neoplasms in rats per unit of radiation dose did not increase with decreasing mean beta-particle dose to the lung over the range of 3.6 to 37 Gy. The weighted average of these three values was 47 +/- 6.4 (+/-SE) excess lung neoplasms per 10(4) rat Gy. To extend the risk coefficients for lung neoplasms to lower doses by experimentation will require much larger numbers of rats than used in this study.

Administration, Inhalation↗
PubMed1995

Beta-particle dosimetry in radiation synovectomy.

Beta-particle dosimetry of various radionuclides used in the treatment of rheumatoid arthritis was estimated using Monte Carlo radiation transport simulation coupled with experiments using reactor-produced radionuclides and radiachromic film dosimeters inserted into joint phantoms and the knees of cadavers. Results are presented as absorbed dose factors (cGy-cm2/MBq-s) versus depth in a mathematical model of the rheumatoid joint which includes regions of bone, articular cartilage, joint capsule, and tissue (synovium) found in all synovial joints. The factors can be used to estimate absorbed dose and dose rate distributions in treated joints. In particular, guidance is provided for those interested in (a) a given radionuclide's therapeutic range, (b) the amount of radioactivity to administer on a case-by-case basis, (c) the expected therapeutic dose to synovium, and (d) the radiation dose imparted to other, nontarget components in the joint, including bone and articular cartilage.

Arthritis, Rheumatoid↗
PubMed2001

A mouse model for calculating the absorbed beta-particle dose from (131)I- and (90)Y-labeled immunoconjugates, including a method for dealing with heterogeneity in kidney and tumor.

Flynn, A. A., Green, A. J., Pedley, R. B., Boxer, G. M., Boden, R. and Begent, R. H. J. A Mouse Model for Calculating the Absorbed Beta-Particle Dose from (131)I- and (90)Y-Labeled Immunoconjugates, Including a Method for Dealing with Heterogeneity in Kidney and Tumor. Radiat. Res. 156, 28-35 (2001). Conventional internal radiation dosimetry methods assume that the beta-particle energy is absorbed uniformly and completely in the source organ and that the radioactivity is distributed uniformly in the source. However, in mice, a considerable proportion of the beta-particle energy can escape the source organ, resulting in large cross-organ doses. Furthermore, the distribution of radioactivity is generally heterogeneous in kidney and tumor. Therefore, a model was developed to account for cross-organ doses and for the effects of heterogeneity in kidney and tumor in mice for two of the most important radionuclides used in therapy, (131)I and (90)Y. Most mouse organs were modeled as single-compartment ellipsoids or cylinders, while heterogeneity in kidney and in tumor was addressed by using two compartments to represent the cortex and the medulla and viable and necrotic cells, respectively. The dimensions of these models were taken from previous studies, with the exception of kidney and tumor, which were defined using radioluminography and mosaics of high-power microscopy images. The absorbed fractions in each compartment were calculated using beta-particle point dose kernels. The self-organ dose was significantly higher for (131)I compared to (90)Y in all compartments, but a considerable amount of beta-particle energy was shown to escape the source organ for both radionuclides, with as much as 85% and 36% escaping the marrow for (90)Y and (131)I, respectively. The cortex was found to occupy a greater proportion of the total kidney volume than the medulla, and consequently the self-dose was higher in the cortex. In addition, the thickness of the viable shell in the tumor increased with tumor size, as did the self-dose fractions in both necrotic and viable areas. This dosimetry model improves dose estimates in mice and gives a conceptual basis for considering dosimetry in humans.

Animals↗
PubMed2000

Endovascular irradiation from beta-particle-emitting gold stents results in increased neointima formation in a porcine restenosis model.

BACKGROUND: Recent studies have shown that ionizing radiation reduces neointima formation after balloon angioplasty and stent implantation in experimental models of restenosis and first clinical trials. The objective of this study was to determine the dose distribution of a new beta-particle-emitting radioactive gold stent and to evaluate the dose-dependent vascular response in the coronary overstretch pig model. METHODS AND RESULTS: Sixteen Göttinger minipigs underwent placement of 11 nonradioactive and 36 beta-particle-emitting stents with activity levels of 10.4+/-0.6, 14.9+/-2.4, 22.8+/-1.3, 35.8+/-2. 8, and 55.4+/-5.3 microCi of (198)Au. Three months after implantation, the percent area stenosis, neointimal thickness, neointimal area, and vessel injury were analyzed by quantitative histomorphometry. The lifetime radiation doses at a depth of 1 mm were 3.3+/-0.2, 4.7+/-0.5, 7.2+/-0.4, 11.4+/-0.9, and 17.6+/-1.7 Gy for the different activity groups. No dose-response relationship was observed in the radioactive stents with respect to percent area stenosis (P=0.297), mean neointimal thickness (P=0.82), or mean neointimal area (P=0.65). Significantly lower neointima formation and less luminal narrowing was seen in the control group than in the beta-particle-emitting stents (P<0.001). Multilinear regression analysis revealed that only radioactivity made a significant independent contribution to the degree of percent area stenosis (P<0. 001). CONCLUSIONS: Neointima formation in pigs is markedly increased by beta-particle-emitting stents with (198)Au as the radioisotope. This study provides evidence that dosages of 3 to 18 Gy of low-dose-rate beta-particle irradiation via endovascular stents cause pronounced luminal narrowing in the animal model at 3 months.

Animals↗
PubMed1999

Comparative deterministic effects of inhaled, insoluble alpha- and beta-particle-emitting radionuclides in dogs.

This report compares the deterministic effects from an alpha-particle-emitting radionuclide, (239)PuO(2), and a beta-particle emitter, (144)Ce in fused aluminosilicate particles (FAP). The studies were conducted in beagle dogs of both genders exposed by inhalation to aerosols of the radionuclides. The initial lung burdens of (239)Pu and (144)Ce were determined by whole-body counting of the (169)Yb added to the plutonium aerosol during its preparation or the (144)Ce and its progeny (144)Pr. In addition, organ retention data were obtained from parallel serial sacrifice studies with the same aerosols. After exposure, the dogs were observed for health effects over their lifetime. The deterministic effects observed for both of these relatively insoluble aerosols were lymphopenia, fibrosis, atrophy of the lung-associated lymph nodes, and radiation pneumonitis. Due to the longer half-life of plutonium, the lymphopenia was more prolonged and the clinical course of the radiation pneumonitis more chronic than that resulting from cerium. The greater tissue penetration of the beta-particle emissions from the cerium resulted in more uniform dose distribution over the lung and the atria of the heart than from the alpha-particle emissions from plutonium.

Administration, Inhalation↗
PubMed1999

Long-term coronary vascular response to (32)P beta-particle-emitting stents in a canine model.

BACKGROUND: The arterial placement of (32)P beta-particle-emitting stents in various experimental animal models results in discordant effects on neointimal formation. We studied the vascular effects of beta-particle-emitting stents in normal canine coronary arteries because compared with pigs and rabbits, the canine model may more closely mimic the vascular response of humans. METHODS AND RESULTS: Thirty stents (control nonradioactive, n=10; low-activity (32)P, 3.5 to 6.0 microCi, n=11; high-activity (32)P, 6.5 to 14.4 microCi, n=8) were implanted in normal canine coronary arteries through the use of a single balloon inflation at nominal pressure. Histological analysis after 15 weeks included the measurement of neointimal and adventitial area and thickness. Neointimal fibrin area was measured with the use of computer-assisted color segmentation on Movat pentachrome sections. Luminal stenosis was significantly increased in (32)P stents compared with control stents (44.6+/-16.8% versus 32.7+/-10.8%; P=0.05) and was highest in the high-activity group (45.5+/-24.3%). No evidence of an "edge effect" was seen in adjacent, nonstented coronary segments. All (32)P stents showed incomplete vascular healing as indicated by a dose-dependent increase in fibrin area with increasing stent activity. Arterial radiation resulted in a decrease in adventitial size, which was maximal for high-activity (32)P stents, indicating an inhibitory effect on the adventitial response to injury. CONCLUSIONS: (32)P beta-particle-emitting stents have adverse vascular effects at 15 weeks in the canine normal coronary artery model. Vascular brachytherapy with this device causes increased neointimal formation and prominent, dose-dependent lack of healing.

Animals↗
PubMed1996

Inhibition of neointimal proliferation with low-dose irradiation from a beta-particle-emitting stent.

BACKGROUND: Restenosis after successful percutaneous transluminal coronary angioplasty is the major factor limiting the long-term effectiveness of this procedure. Neointimal proliferation in response to arterial injury is an important contributor to restenosis. The use of radiation for the treatment of malignant and benign proliferative conditions has been well established. External beam irradiation and endovascular irradiation by use of an after-loading technique have been shown to inhibit neointimal proliferation in experimental models of restenosis. The objective of this study was to investigate whether low-dose irradiation from a beta-particle-emitting stent would inhibit neointimal proliferation after placement in porcine iliac arteries. METHODS AND RESULTS: Fourteen titanium-mesh stents were implanted in the iliac arteries of nine NIH miniature swine. There were seven beta-particle-emitting radioisotope stents (32P, activity level 0.14 microCi) and seven control stents (31P, nonradioactive). Treatment effect was assessed by angiography and histomorphological examination of the stented iliac segments 28 days after implantation. There was a significant reduction in neointimal area (1.76 +/- 0.37 mm2 versus 2.81 +/- 1.22 mm2, P = .05) and percent area stenosis (24.6 +/- 2.9% versus 36.0 +/- 10.7%, P = .02) within the beta-particle-emitting stents compared with the control stents. Neointimal thickness, which was assessed at each wire site, was also significantly less within the treatment stents (0.26 +/- 0.04 mm versus 0.38 +/- 0.10 mm, P = .012). Scanning electron microscopy was performed on sections from four stents. This demonstrated endothelialization of both the treatment and control stents. There was no excess inflammatory reaction or fibrosis in the media, adventitia, or perivascular space of vessels treated with the beta-particle-emitting stent compared with control vessels. At 28 days, there was no difference in smooth muscle cell proliferation as measured by the proliferating cell nuclear antigen index. CONCLUSIONS: A local, continuous source of low-dose endovascular irradiation via a beta-particle-emitting stent inhibits neointimal formation in porcine arteries. This low dose of local irradiation did not prevent endothelialization of the stents. This novel technique offers promise for the prevention of restenosis and warrants further investigation.

Animals↗
PubMed2000

Self absorption of alpha and beta particles in a fiberglass filter.

Environmental air sampling uses fiberglass filters to collect particulate matter from the air and then a gas flow detector to measure the alpha and beta activity on the filter. When counted, the filter is located close to the detector so the alpha and beta particles emerging from the filter travel toward the detector at angles ranging from zero to nearly 90 degrees to the normal to the filter surface. The particles at small angles can readily pass through the filter, but particles at large angles pass through a significant amount of filter material and can be totally absorbed. As a result, counting losses can be great. For 4 MeV alpha particles, the filter used in this experiment absorbs 43% of the alpha particles; for 7.5 MeV alphas, the absorption is 13%. The measured beta activities also can have significant counting losses. Beta particles with maximum energies of 0.2 and 2.0 MeV have absorptions of 44 and 2%, respectively.

Absorption↗
PubMed2006

Relative toxicity of chronic irradiation by 45Ca beta particles and 242Cm alpha particles with respect to the production of lung tumors in CBA/Ca mice.

Approximately 1800 female CBA/Ca mice were exposed by inhalation at three dose levels to beta particles from (45)Ca-labeled fused aluminosilicate particles (FAP), to alpha particles from (242)Cm-labeled FAP, or to carrier control FAP. Another group of mice inhaled no FAP and were designated as untreated cage controls. The FAP in combination with these radionuclides was used to achieve the same spatial and temporal distribution of alpha- and beta-particle dose within the irradiated mice. Some mice were killed to determine the clearance of radiolabeled FAP from their lungs, and the remainder were allocated to a life-span study. All animals were subjected to a detailed necropsy. To facilitate the identification of small tumors, the lungs were rendered transparent in methyl salicylate and examined under back illumination for the presence of lesions. Lung nodules and other microscopic lesions were excised for histological examination. The median survival of mice in all groups was approximately 910 days. The control animals lived longer than those that were irradiated, but it was difficult to determine a dose-response relationship for survival among the exposed mice. Benign adenomas and, less frequently, malignant adenocarcinomas were identified in all animal groups. The prevalence of these tumors was approximately 28.8% in the control mice, which is consistent with the results of other studies using the same strain of mouse. After exposure to radionuclide-labeled FAP, there was a significant dose-related increase in the prevalence of lung tumors in (242)Cm- (peak prevalence 55%) and (45)Ca-exposed (peak prevalence 48.6%) mice. The prevalence of tumors in the mice that received (242)Cm-labeled FAP was approximately twice that in the mice that inhaled (45)Ca-labeled FAP within the range of doses employed (0.55-4.69 Gy). Using the ratio of the slope of the linear component of the dose-response curves, the toxicity of the alpha particles relative to the beta particles was 1.5 (90% CI: 0.7, 9.0) for all adenomas and 9.4 (90% CI: 5.0, 23.0) for the less frequent adenocarcinomas. The relative toxicity for adenocarcinomas was found to decrease with increasing dose.

Adenocarcinoma↗
PubMedDate not supplied

Considerations on the calibration of small thermoluminescent dosimeters used for measurement of beta particle absorbed doses in liquid environments.

An investigation has been carried out on the factors which affect the absolute calibration of thermoluminescent dosimeters (TLDs) used in beta particle absorbed dose evaluations. Four effects on light output (LO) were considered: decay of detector sensitivity with time, finite TLD volume, dose linearity, and energy dependence. Most important of these was the decay of LO with time in culture medium, muscle tissue, and gels. This permanent loss of sensitivity was as large as an order of magnitude over a 21-day interval for the nominally 20-microns-thick disc-shaped CaSO4(Dy) TLDs in gel. Associated leaching of the dosimeter crystals out of the Teflon matrix was observed using scanning electron microscopy. Large channels leading from the outside environment into the TLDs were identified using SEM images. A possibility of batch dependence of fading was indicated. The second most important effect was the apparent reduction of light output due to finite size and increased specific gravity of the dosimeter (volume effect). We estimated this term by calculations as 10% in standard "mini" rods for beta particles from 90Y, but nearly a factor of 3 for 131I beta particles in the same geometry. No significant nonlinearity of the log (light output) with log (absorbed dose) over the range 0.05-20.00 Gy was discovered. Energy dependence of the LO was found to be not detectable, within measurement errors, over the range of 0.60-6.0 MeV mean energy electrons. With careful understanding of these effects, calibration via gel phantom would appear to be an acceptable strategy for mini TLDs used in beta absorbed dose evaluations in media.(ABSTRACT TRUNCATED AT 250 WORDS)

Beta Particles↗