Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Beta Particles”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 973 records · Page 54Linked to original sources
PubMed1998

Short-term implantation effects of a DCPD-based calcium phosphate cement.

Calcium phosphate cements can be handled in paste form and set in a wet medium after precipitation of calcium phosphate crystals in the implantation site. Depending on the products entering into the chemical reaction leading to the precipitation of calcium phosphates, different phases can be obtained with different mechanical properties, setting times and injectability. We tested a cement composed of a powder, containing beta-tricalcium phosphate (beta-TCP) and sodium pyrophosphate mixed with a solution of phosphoric and sulphuric acids. The cement set under a dicalcium phosphate dihydrate (DCPD)-based matrix containing beta-TCP particles. This was injected with a syringe into a defect drilled in rabbit condyles, the control being an identical defect left empty in the opposite condyle. The condyles were analysed histologically 2, 6 and 18 weeks after implantation. After injection into the bone defect the cement set and formed a porous calcium phosphate structure. Two different calcium phosphate phases with different solubility rates could be identified by scanning electron microscopy (SEM) observation. The less-soluble fragments could be degraded by cell phagocytosis in cell compartments of low pH or integrated in the newly formed bone matrix. The degradation rate of the material was relatively high but compatible with the ingrowth of bone trabeculae within the resorbing material. The ossification process was different from the creeping substitution occurring at the ceramic contact. Bone did not form directly at the cement surface following the differentiation of osteoblasts at the material surface. The trabeculae came to the material surface from the edges of the implantation site. Bone formation in the implantation site was significantly higher than in the control region during the first week of implantation. In conclusion, this material set in situ was well tolerated, inducing a mild foreign-body reaction, which did not impair its replacement by newly formed bone within a few weeks.

Animals↗
PubMed1999

Effects of PVC bags sterilization process on the 5-fluorouracil stability.

The stability and compatibility of 5-fluorouracil (5-FU) in undiluted or diluted admixtures stored in beta-radiation sterilized portable poly(vinyl chloride) (PVC) infusion bags were investigated. Admixtures containing 5-FU 50 mg ml(-1) not diluted or 25 mg ml(-1) diluted in 0.9% sodium chloride injection were placed in 100 or 250 ml empty PVC reservoirs sterilized initially by beta-irradiation. They were protected from light and placed at 37 degrees C. Two ml quantities were withdrawn immediately after preparation and after storage for 1, 2, 3, 4, 5, 6, 7 and 14 days. For each condition, samples from each admixture were tested for drug concentration by stability-indicating high-performance liquid chromatography. The admixtures were also monitored for precipitation, color change and pH. Evaporative water loss from the containers was also measured. 5-FU was compatible with PVC containers in all tested conditions for 14 days. No loss of drug and no color change were detected throughout the storage period. pH values were stable and neither precipitation nor loss of water through the reservoirs was observed when drug 50 or 25 mg ml(-1) (diluted using 0.9% sodium chloride) was stored in 100 ml capacity polyvinyl PVC bags. However, when stored in 250 ml capacity PVC bags, the 5-FU solution showed precipitation after 13 and 14 days of storage, but no drug loss was detected due to a substantial loss of water. The precipitation of the drug was due to the decrease of pH induced by the dehydrochlorination of PVC during beta-irradiation leading to the formation of hydrochloric acid in solution. Differences observed between 100 and 250 ml capacity bags can be explained by the greater area of PVC present in 250 ml reservoirs, and consequently more HCl formed. Finally, more plasticizer, di-(2-ethylhexyl) phthalate (DEHP), was then detected in drug solutions stored in 250 ml PVC bags. So, we recommend the use of 100 ml bags to store 5-FU at longer storage times and higher temperatures.

Antimetabolites, Antineoplastic↗
PubMed2003

Trabeculectomy with beta radiation: long-term follow-up.

PURPOSE: To evaluate the long-term outcome and complications of trabeculectomy with beta radiation. DESIGN: Retrospective noncomparative case series. PARTICIPANTS: Forty-three patients with confirmed primary open-angle glaucoma (POAG), who received trabeculectomy with adjunctive beta radiation at the Prince of Wales Hospital between June 1991 and November 1994. METHODS: Patients fulfilling the preceding criteria were followed up longitudinally. The visual acuity, intraocular pressure (IOP), bleb morphology, and complications were evaluated. MAIN OUTCOME MEASURES: Visual acuity, IOP, bleb morphology, complications. RESULTS: Forty-three eyes of 43 consecutive Chinese patients were recruited and successfully followed up for a minimum of 7 years. The mean age +/- 1 standard deviation (SD) was 60.9 +/- 13.0 years. There were 29 males and 14 females. The mean baseline IOP +/- 1 SD was 28.3 +/- 5.8 mmHg. The mean postoperative IOP +/- 1 SD after the initial trabeculectomy was 11.9 +/- 4.3 mmHg, and the mean number of preoperative IOP-lowering eyedrops +/- 1 SD was reduced from 2.8 +/- 0.5 to 0.7 +/- 1.0 at 7 years follow-up. The qualified success rate at 7 years follow-up, defined as IOP <or=21 mmHg with and without medication(s), was 88.4%. The complete success rate at 7 years defined as IOP <or=21 mmHg without medication was 60.7%. Two eyes developed blebitis, and one of them progressed to corneal decompensation after the infection. One eye had hypotony, and one eye had a traumatic ruptured bleb. Twelve eyes (27.9%) developed significant cataract. No corneal ulceration or scleral necrosis was encountered. CONCLUSIONS: From this noncomparative study, trabeculectomy with a single dose of 1000 rad beta radiation used as an adjunctive measure for POAG in Chinese eyes had achieved a qualified success rate of 88.4% at 7 years.

Adult↗
PubMed1991

Recurrence rate and complications after beta irradiation for pterygia.

Of 1102 consecutive patients treated with beta irradiation after pterygium removal at the Queensland Radium Institute from 1973 through 1978, 503 had a follow-up ophthalmologic examination in 1989, while a further 82 had at least a 10-year follow-up from ophthalmologic records. One hundred forty-two patients were lost to follow-up because of death, lack of cooperation, and geographical inaccessibility. A further 375 patients could not be located. Of those not followed for at least 10 years, 162 had a follow-up, recorded from ophthalmologic records, of at least 3 months. After an average dose of 22 Gray, there was a recurrence rate of 12%. A further 13% showed some sign of scleromalacia, which included 4.5% of the study group who had severe thinning.

Adult↗
PubMed2002

Determination and application of the reference isodose length (RIL) for commercial endovascular brachytherapy devices.

BACKGROUND AND PURPOSE: During the last years endovascular brachytherapy has been established as a new field in radiotherapy. In a recent recommendation of the EndoVAscular, Groupe Européen de Curiethérapie, European Society for Therapeutic Radiation Oncology, Working Group the reference isodose length (RIL) has been introduced as a central parameter for treatment planning. It is defined as the vessel length at the reference depth enclosed by the 90% isodose. The dose is normalized to 100% at the reference depth (i.e. lumen radius plus 1 mm into the vessel wall) at the central plane. In order to avoid a geographic miss the clinical target length has to be encompassed by the RIL. MATERIAL AND METHODS: RILs are determined by Monte Carlo calculations and GafChromic film dosimetry for three endovascular brachytherapy devices currently in clinical use (192Ir seed ribbon, 32P wire source, 90Sr seed train). For all measurements, phantoms and devices the sensitive layer of GafChromic film is located in a plane at 2+/-0.1 mm parallel to the axis of the source delivery catheter. The EGSnrc code system is applied to calculate the dose profile at 2 and 3 mm distance from the source axis. RESULTS: For the ten seed 192Ir source calculated RIL at 2 mm radial distance is 30.2 mm whereas the measured RIL is 33.5 mm. In case of a 20 mm 32P wire source with two steps the calculated RIL of 36.6 mm shows excellent agreement compared with the measured value of 36.2 mm. The calculated RIL of a 40 mm 90Sr seed train was 35.8 mm compared to a measured value of 34.8 mm. CONCLUSION: As a compromise between calculated and measured RIL values at 2 and 3 mm radial distances we propose to use a RIL of 30 mm for the 192Ir ten seed ribbon, 36 mm for the32P wire source with two steps and 35 mm for the 40 mm 90Sr seed train. These parameter values can be used to define the maximum intervention length for endovascular sources.

Beta Particles↗
PubMed2000

Development of a poly(ortho ester) prototype with a latent acid in the polymer backbone for 5-fluorouracil delivery.

A study has been carried out to determine whether the latest family of poly(ortho esters) can be converted into a practical delivery system. This polymer differs from the previously described polymers in that it incorporates a short segment of a latent acid in the polymer backbone. The following issues were specifically addressed: (a) can the erosion and drug release be reproducibly controlled to yield the desired drug release kinetics and erosion rates? (b) Is the polymer stable during radiation sterilization, on storage and on fabrication? (c) Can the polymer be prepared reproducibly at the desired molecular weights and molecular weight distribution? (d) Is the polymer safe for its intended application and does the in vivo erosion proceed to completion? (e) Can the polymer be easily fabricated into desired configurations? Studies have shown that if the synthesis is carefully controlled, the desired molecular weights can be reproducibly prepared, that the polymer is reasonably stable after irradiation at 24 kGy and during storage at room temperature under anhydrous conditions, and that it can be safely thermally fabricated at temperatures in the neighborhood of 120 degrees C. When polymer devices were implanted intraperitoneally in rats the polymer eroded to completion without any overt toxicity as determined by the measured parameters.

Acids↗
PubMed1989

Are topical corticosteroids useful in phototherapy for psoriasis?

A prospective, randomized, double-blind, placebo-controlled trial was performed to assess the effect of a potent topical corticosteroid cream used in conjunction with ultraviolet B (UVB) phototherapy on psoriasis with respect to time to clearing and duration of remission after clearing. Of the 53 outpatients who received suberythemogenic UVB phototherapy three times per week, 24 applied the topical corticosteroid and 29 applied the placebo cream twice daily until clearing was achieved. Nine patients in each group failed to comply with the protocol. Although there was a trend toward a slightly more rapid response in the topical corticosteroid-treated group, there was no significant difference in patients' early response to therapy, number of treatments, and UVB dose required to achieve clearing. Patients in the topical corticosteroid-treated group remained in remission longer than did patients in the control group (183 vs 116 days). Life-table analysis predicts that 62% of emollient-treated patients flare within 6 months of clearing compared with only 42% of topical corticosteroid-treated patients (p less than 0.1). For most patients with psoriasis who receive UVB therapy in an outpatient setting, the use of potent topical corticosteroids appears to produce, at most, a modest beneficial effect.

Administration, Topical↗
PubMed2003

A multicentre European registry of intraluminal coronary beta brachytherapy.

AIMS: To assess the feasibility, safety and effectiveness of intravascular brachytherapy (VBT) in routine clinical practice. METHODS AND RESULTS: Between April 1999 and September 2000, 1098 consecutive patients treated in 46 European centres by intraluminal irradiation using a Sr/Y(90)source train (BetaCath, Novoste, GA) were included in a registry, and follow-up data were obtained for 98.8% of them after 6.3+/-2.4 months. Eight hundred and forty (76.5%) patients were males, and mean age was 62.0+/-10.2 years. Two hundred and seventy-one (26.9%) had unstable angina, and 256 (23.5%) were diabetics. Nine hundred and thirteen lesions (77.7%) were the result of in-stent restenosis, 208 (17.7%) were de novo lesions and 48 (4.1%) non-stented restenotic lesions. Mean estimated reference diameter was 3.2+/-0.5mm and mean estimated lesion length was 19.0+/-11.8mm. The prescribed radiation dose was 18.8+/-3.2Gy. Multivessel irradiation was done in 6.2% of cases, and a new stent was implanted in 29.6% of cases. Most patients received 6 or 12 months of combined aspirin and thienopyridin treatment after the procedure. Technical success was obtained in 95.9% of treated lesions, and the in-hospital major adverse cardiac event (MACE) rate was 1.8%. At follow-up, the MACE rate was 18.7% (1.9% deaths from any cause, 2.6% AMI, 13.3% TVR by PCI and 3.3% TVR by CABG). CONCLUSION: The major current application of VBT is the treatment of in-stent restenosis. The good results of VBT observed in recent randomized controlled trials can be reproduced in clinical practice.

Aged↗
PubMed2002

Terrestrial isopods congregate under a low-level beta-emitter source.

Ionizing radiation is ubiquitous, but very few experiments have investigated the biological effects of the natural background radiation at very low doses (>10 mGy/yr). We examined whether the background radiation, or radiation of a slightly higher level, has a role in evoking changes in behaviors of terrestrial isopods (woodlice). Upon exposure to a source giving 15 times the background level placed at one end of a box, a significant increase in the number of woodlice gathering under the beta-source was observed with time, as compared with the sham control. Terrestrial isopods have chemoreceptors (the olfactory system) on the terminal segment of their antennae. An additional experiment confirmed the involvement of these antennae in the radiation effect on behavior. After the excision of the antennae, no beta-taxis response was observed. The behavior of the group exposed to the source giving 30 times the background tended to decrease gradually in the area of the source, and the individuals aggregated in the area away from the source. Thus, the olfactory sensor in the antennae may be an important organ involved in the prompt response to radiation exposure, and the discrimination of the radiation field strengths of radioisotopes.

Animals↗
PubMed2003

Genetic consequences of radioactive contamination by the Chernobyl fallout to agricultural crops.

The genetic consequences of radioactive contamination by the fallout to agricultural crops after the accident at the Chernobyl NPP in 1986 have been studied. In the first, acute, period of this accident, when the absorbed dose was primarily due to external beta- and gamma-irradiation, the radiation injury of agricultural crops, according to the basic cytogenetic tests, resembled the effect produced by acute gamma-irradiation at comparable doses. The yield of cytogenetic damage in leaf meristem of plants grown in the 10-km zone of the ChNPP in 1987-1989 (the period of chronic, lower level radiation exposure) was shown to be enhanced and dependent on the level of radioactive contamination. The rate of decline with time in cytogenetic damage induced by chronic exposure lagged considerably behind that of the radiation exposure. Analysis of genetic variability in three sequential generations of rye and wheat revealed increased cytogenetic damage in plants exposed to chronic irradiation during the 2nd and 3rd years.

Avena↗
PubMed1997

[An epidemic of asthma caused by soybean in L'Hospitalet de Llobregat (Barcelona)].

Twenty-six epidemics of asthma occurred in Barcelona between 1981 and 1987 in relation to inhalation of soy dust from grain silo unloading in the harbor. No further epidemics occurred after filters were installed, until a 1994 outbreak of asthma due to soy was detected in L'Hospitalet de Llobregat, a city on the outskirts of Barcelona. We describe 9 patients who presented with acute asthma attacks of sudden onset within a time span of 135 minutes. Counts of total IgE and IgE specific to soy extract were analyzed in all patients. Skin prick tests confirmed exposure to soy in all cases. Atmospheric levels of alcoholic fractions of soy particles (beta-sitosterol and stigmasterol) registered in L'Hospitalet de Llobregat were higher than those detected in Barcelona. We confirmed that soy had been unloaded in the harbor the same day, and that climatic conditions favored the movement of air from the port toward the city of L'Hospitalet. We postulate the need to periodically review preventive measures given the potential severity of the such epidemics.

Acute Disease↗
PubMed2001

[Current status of intracoronary brachytherapy].

Intracoronary radiation therapy or intracoronary brachytherapy has been developed as an attempt to decrease restenosis after percutaneous coronary interventions. Two parallel technologies, one employing radioactive stents, the other catheter-based radiation (using either beta- or gamma- emitters), have been the subject of numerous animal and human studies. In vivo intravascular ultrasound imaging studies have played a major role in determining the possible mechanism of action of intracoronary radiation therapy and the pathogeny of many of the complications related to the use of this technique. This manuscript is aimed at revising the potential and limitations of intracoronary brachytherapy, as well as at summarizing the results of the currently reported clinical trials.

Angioplasty, Balloon, Coronary↗
PubMed2001

Low-dose-rate ionizing irradiation for inhibition of secondary cataract formation.

INTRODUCTION: Secondary cataract formation limits visual function after cataract surgery. Various experimental methods utilizing the pharmacologic inhibition of lens epithelial cell proliferation have been proposed. However, diffusion into the anterior chamber may lead to damage of corneal endothelial cells. This study evaluated the inhibition of lens epithelial cell proliferation with a capsular bag ring, labeled with a beta-emitting radioisotope. METHODS AND MATERIALS: In vitro studies using rabbit lens epithelial cells were performed to investigate the dose-dependent effect of irradiation. Based on these results, P-32-labeled PMMA rings were implanted into the capsular bag of NZW rabbits in vivo after phacoemulsification. Animals were examined for development of posterior capsule opacification over a period of 12 weeks following surgery. Radiation damage to the surrounding ocular tissue was subsequently analyzed in histologic sections using TUNEL assay and proliferation marker. RESULTS: Irradiation of lens epithelial cells in vitro with >5 Gy resulted in a dose-dependent decrease in the number of cells. BrdU testing demonstrated a near complete inhibition of cell proliferation. In vivo, implantation of P-32-labeled PMMA rings led to inhibition of epithelial cell proliferation and secondary cataract formation but was not able to fully inhibit aberrant differentiation of some remaining cells. Histologic examination showed no evidence of radiation damage of the ciliary body or the corneal endothelium. CONCLUSIONS: Low-dose beta irradiation exhibits the potential for inhibition of lens epithelial cell proliferation both in vitro and in vivo. Further investigation of various nuclides and their radiation profiles is needed to optimize the prevention of posterior capsule opacification due to epithelial cell proliferation.

Animals↗
PubMed2001

Effect of ionizing radiation on thymidine uptake, differentiation, and VEGFR2 receptor expression in endothelial cells: the role of VEGF(165).

PURPOSE: Late thrombosis of irradiated vascular segments may be the consequence of endothelial cell (EC) dysfunction after radiation therapy. We investigated the effects of beta ionizing radiation on human EC viability, thymidine uptake, and differentiation. METHODS AND MATERIALS: Endothelial cells were exposed to (32)P-labeled DNA oligonucleotides in incremental doses of 2, 6, and 10 Gy. The modulation of the VEGFR2 receptor expression after irradiation and the overall potential radioprotective effect of VEGF(165) on these functions were assayed. RESULTS: A dose-dependent inhibitory effect of beta irradiation on ECs' thymidine uptake and differentiation was observed. EC viability, however, was not affected at levels of radiation up to 10 Gy. VEGF(165) proved to have a radioprotective effect as ECs' thymidine uptake, after radiation doses of 2, 6, and 10 Gy, was increased by 1.5-, 2-, and 4-fold, respectively, in the presence of 10 ng/ml of VEGF(165) (p < 0.05 vs. LacZ). This concentration of VEGF(165) also proved beneficial in maintaining cell differentiation at 16 h postirradiation when compared to controls. These biologic effects were in direct correlation with the upregulation of VEGFR2 receptor expression in irradiated ECs. CONCLUSIONS: beta irradiation interacts directly with EC functions by significantly reducing their ability to differentiate and proliferate, associated with upregulation of VEGFR2. These effects can be prevented in part by pretreating cells with VEGF(165), an effect potentially favored by the upregulation of VEGFR2 receptor expression after irradiation.

Adenoviruses, Human↗
PubMed2001

The use of cylindrical coordinates for treatment planning parameters of an elongated 192Ir source.

PURPOSE: The doses given to the intima, media, and adventitia are very crucial quantities in intravascular brachytherapy. To facilitate accurate computerized treatment planning calculations, we have determined dose distributions in away-and-along table format around an 192Ir wire source and developed pertinent dosimetric parameters in cylindrical coordinates. METHODS AND MATERIALS: The Monte Carlo method (MCNP4C code) was used to calculate the dose distributions for the AngioRad 192Ir wire source (model SL-77HS, Interventional Therapies). The calculations were carried out for photon, beta, and electron (conversion and Auger) contributions for radial distances from 0.03 to 2.0 cm with 0.01-cm increments, and up to 2.24 cm from the source center in the longitudinal direction with 0.04-cm resolution. Dose rate values are determined in away-and-along format (cylindrical coordinates) and then converted to spherical coordinate format. Dosimetric parameters, such as the geometry factor, G(r, theta), and anisotropy function, F(r, theta), are generated in both cylindrical (R, Z, phi) and spherical (r, theta, phi) coordinates. The use of a cylindrical coordinate system for treatment planning parameters is proposed as a more suitable approach for accurate calculations. RESULTS: The photon contribution to dose varies nearly inversely with radial distance (from the source center) along the perpendicular bisector with 0.199 x 10(-3) cGy U(-1) s(-1) (0.802 cGy Ci(-1) s(-1)) at 1 cm. The beta and electron contributions start at very high values of about 35.5 x 10(-3) cGy U(-1) s(-1) and 11.0 x 10(-3) cGy U(-1) s(-1), respectively, at 0.03 cm and fall off exponentially to negligible amount near 0.2 cm. The total dose rate at 0.2 cm is 1.428 x 10(-3) cGy U(-1) s(-1) (5.754 cGy Ci(-1) s(-1)). The radial dose function, g(R), is nearly unity between 0.2 cm and 2 cm. Due to the beta and electron dose contributions, g(R) increases steeply to 5.5 as radial distance decreases from 0.2 cm down to 0.03 cm. The F(R, Z) values are close to unity for the majority of the region of interest. In contrast, F(r, theta) experiences a steep rise as shallow angles are approached (closer to the source), related to the beta dose contributions. Accurate treatment planning calculations would be possible with linear interpolation of F(R, Z), but difficult with F(r, theta) in the spherical coordinate system and the original normalization point as recommended in the American Association of Physicists in Medicine Task Group 60 (AAPM TG-60) formalism. CONCLUSION: The AngioRad 192Ir wire source, model SL-77HS, was completely characterized dosimetrically using Monte Carlo methods. The use of cylindrical coordinates and a modified anisotropy function normalization point for dosimetric parameters of an elongated 192Ir source is more suitable for accurate computerized treatment planning calculations in intravascular brachytherapy.

Algorithms↗