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At least 109 records · Page 6Linked to original sources
PubMed1982

Radiation effects of iridium-192 implants in the cat brain.

The radiation effects of 192Ir permanent implants into the cat brain were studied with respect to morphological changes, blood flow, brain water and electrolytes. 192Ir wires (10 animals) and non-radioactive silver wires (5 control animals) were placed stereotactically into the left internal capsule. Activity of 192Ir was 0.31 mCi, and accumulated dose at 5 mm distance was 3060 rad after 21 days and 4680 rad after 35 days, respectively. None of the animals presented a neurological deficit, and the EEG recording was without significant changes. Histological damage which could be attributed to the radiation was not observed. Serum proteins, however, were detected immunohistochemically in reactive astrocytes (3x), in macrophages (2x) and as diffuse perivascular accumulation. Brain water in the white matter near the implantation site increased from 68.6 to 73.2%, corresponding to a volume increase of about 17%. There was no change in the grey matter or the opposite hemisphere. Cerebral blood flow decreased slightly but there was no relationship with the development of edema. The findings suggest that low dose rate topical irradiation of the brain produces primarily membrane dependent changes, resulting in local brain edema.

Animals↗
PubMed1994

[Principles of curietherapy].

Brachytherapy, the use of radioactive sources implanted into the tumor or placed in proximity to the tumor, makes it possible to obtain well defined, localized distributions of the irradiation dose. The word "brachytherapy" includes various techniques which are practiced most frequently with cesium-137 or iridium-192. Whether used alone or in conjunction with surgery and (or) external irradiation, brachytherapy has contributed to the development of organ conserving treatment for cancer, notably and more recently, for carcinoma of the breast, bladder and buccal cavity, in addition to its traditional applications in gynecological and cutaneous cancers. Refinements of brachytherapy techniques have been made possible by recent advances in 3-D imaging and by the development of highly active radioactive sources which are used to obtain very precise dose distributions and very short treatment times.

Brachytherapy↗
PubMed1993

Radium needle used to calibrate germanium gamma-ray detector.

A standard platinum-iridium needle that contains 374 MBq 226Ra was tested as a source for calibrating a portable germanium detector used with a gamma-ray spectrometer for environmental radioactivity measurements. The counting efficiencies of the 11 most intense gamma rays emitted by 226Ra and its short-lived radioactive progeny at energies between 186 and 2,448 keV were determined, at the full energy peaks, to construct a curve of counting efficiency vs. energy. The curve was compared to another curve between 43 and 1,596 keV obtained with a NIST mixed-radionuclide standard. It was also compared to the results of a Monte Carlo simulation. The 226Ra source results were consistent with the NIST standard between 248 and 1,596 keV. The Monte Carlo simulation gave a curve parallel to the curve for the combined radium and NIST standard data between 250 and 2,000 keV, but at higher efficiency.

Calibration↗
PubMed2005

Evaluation of novel whole-body high-resolution rodent SPECT (Linoview) based on direct acquisition of linogram projections.

UNLABELLED: Studies of the biodistribution of radiolabeled compounds in rodents frequently are performed during the process of development of new pharmaceutical drugs. This article presents the evaluation of a new whole-body animal SPECT system, called the Linoview SPECT system. METHODS: Linoview SPECT is based on the linear orbit acquisition technique associated with slit-aperture collimators mounted on 4 pixelated CsI(Na) detectors composed of an array of small, individual crystal elements. Sliding iridium rods allow variation of the collimator aperture. Hot-rod and cold-rod phantoms filled with (99m)Tc were imaged. Mice were imaged, and kidney radioactivity was measured after injection of (99m)Tc-dimercaptosuccinic acid and (111)In-diethylenetriaminepentaacetic acid-d-Phe(1)-octreotide ((111)In-pentetreotide; Octreo-Scan(111)). RESULTS: Phantom studies showed that hot rods separated by 0.35 mm can be distinguished and that 0.65-mm-diameter cold rods can be visualized, both at low-counting-rate acquisitions (111 and 59 MBq x h, respectively). In both mouse studies, the SPECT images allowed a clear delineation of the radioactivity concentrated over the cortex area of the kidneys, whereas the pelvis and the pelviureteral junction (1 mm) appeared as cold areas. The quantitative data derived from SPECT were in good agreement with the radioactivity counting obtained with a gamma-counter after isolation of the kidneys. In addition, in the mouse injected with (111)In-pentetreotide, the kidney radioactivity distribution seen with SPECT was in agreement with the ex vivo autoradiograms of the isolated kidneys. CONCLUSION: The phantom studies showed a clear improvement of the spatial resolution over the results reported in the literature with other dedicated small-animal SPECT systems, especially in cold-rod phantom studies. The increased performance can be ascribed to the high stability of the system with regard to the statistical noise present in the acquired data. The mouse studies showed that this system will be most useful for in vivo high-resolution SPECT and quantitative biodistribution studies in rodents, even with medium-energy radioisotopes that are difficult to image, such as (111)In.

Animals↗
PubMed1978

[Present day development of the Paris System. First part: coplanar patterns and those called "in squares" (author's transl)].

The Paris System is a previsional dosimetric system which facilitates the work of curietherapists working with iridium 192 wires. Introduced about twelve years ago for radio-active implantations in one linear plane, this system has now become more generalized for implantations in two or more linear planes. After a brief review of the principles on which the Paris System is based, and introducing the new definitions arising from its development, the authors present the results of a systematic computerized study. The results obtained were used to establish, among others, the simple relationships between the geometric implantation data (disposition, length, number, separation... of the radioactive lines) and the dimensions of the volume treated, for the coplanar patterns and those called "in squares",

Humans↗
PubMed2005

Application of the MAX/EGS4 exposure model to the dosimetry of the Yanango radiation accident.

According to the International Atomic Energy Agency (IAEA), industrial radiography accounts for approximately half of all reported accidents for the nuclear related industry. Detailed information about these accidents have been published by the IAEA in its Safety Report Series, one of which describes the radiological accident which happened in 1999 in Yanango/Peru. Under unsettled circumstances an 192Ir source was lost from an industrial radiographic camera and later picked up by a welder, who normally had nothing to do with the radiographic work. The man put the source into the right back pocket of his jeans and continued working for at least another 6.5 h. This study uses the MAX/EGS4 exposure model in order to determine absorbed dose distributions in the right thigh of the MAX phantom, as well as average absorbed doses to radiosensitive organs and tissues. For this purpose, the Monte Carlo code for standard exposure situations has been modified in order to match the irradiation conditions of the accident as closely as possible. The results present the maximum voxel absorbed dose, voxel depth absorbed dose and voxel surface absorbed dose distributions, average organ and tissue doses and a maximum surface absorbed dose for zero depth.

Adipose Tissue↗
PubMed1985

Problems associated with iridium-192 wire implants.

Three incidents are reported, from different radiotherapy centres, in which an implanted iridium-192 wire remained in the tissues of a patient after withdrawal of the plastic tubing in which it was contained. In each case the instrument used to cut the wire had probably formed a hook on the end of the wire which caused it to catch in the tissues. Detailed recommendations are made for avoiding such incidents in the future, the most important of which is that the patient should be effectively monitored after the supposed removal of all radioactive sources.

Aged↗
PubMed1993

The air-kerma rate constant of 192Ir.

The air-kerma rate constant gamma delta (and its precursors), as one of the basic radiation characteristics of 192Ir, was determined by many authors. Analysis of accessible data on this quantity led us to the conclusion that published data strongly disagree. That is the reason we calculated this quantity on the basis of our and many other authors' gamma-ray spectral data and the latest data for mass energy-transfer coefficients for air. In this way, a value was obtained for gamma delta of 30.0 +/- 0.9 a Gy m2 s-1 Bq-1 for an unshielded 192Ir source and 27.8 +/- 0.9 a Gy m2s -1Bq-1 for a standard packaged radioactive source taking into account attenuation of gamma rays in the platinum source wall.

Iridium Radioisotopes↗
PubMed2000

Radiation safety of personnel during catheter-based Ir-192 coronary brachytherapy.

Catheter-based brachytherapy using Ir-192 seed sources has shown significant reduction in the rate of restenosis among patients with coronary in-stent restenosis. High-energy gamma rays from Ir-192 raise some radiation safety issues of personnel. The aim of this study was to fully analyze the radiation safety issues associated with Ir-192 brachytherapy in the cardiac cath lab environment. Measurements were made to assess the penetrating ability of Ir-192 gamma rays through tissues, concrete and lead. Radiation exposure levels were measured around a large number of patients undergoing Ir-192 brachytherapy. Personnel were carefully monitored for any additional dose received from brachytherapy for the last five years covering > 500 cases. Our results showed that with a proper radiation safety program in place, the dose to cath lab staff was negligible. It was concluded that radiation safety of personnel was easy to maintain during catheter-based coronary brachytherapy using Ir-192 seed sources.

Air Pollution, Radioactive↗
PubMed1994

[Brachytherapy in choroid tumors].

Even though brachytherapy has been used for many years to treat choroidal tumors, it is not a widespread technique because it requires much organization and operators skills. The most common methods use 60Cobalt and 106Rutenium plaques, or custom-made plaques with 125Iodine loaded seeds. Another, less common, technique uses 192Iridium wires loaded on custom-made plaques. The technique we used to treat 4 retinoblastomas and 2 choroidal melanomas uses 192Iridium wires loaded on custom-made plaques. The applicator is made of a quick drying paste poured over a sphere the same size as the eye-ball: plastic tubes are inserted, according to preliminary dosimetric measurements, to house the Iridium wires. The applicator is positioned on the eye-ball corresponding to tumor site by surgery. The Iridium sources are inserted into the plastic tubes at the end of surgical placement: this afterloading technique guarantees maximal staff protection. 192Iridium (320 keV gamma emitter) allows the dose to be transmitted deeper than with 125Iodine (30 keV gamma-emitter) and 106Rutenium (3540 keV beta-emitter). Therefore, with Iridium, the dose delivered is lower on the eye-ball surface for the same tumor dose. On the other hand, the use of 60Cobalt (1250 keV gamma-emitter) gives the healthy surrounding tissues higher doses. To conclude, this method allows us to customize the application to every single case, to reach posterior sites, to ensure radioactive protection to staff thanks to afterloading and to obtain a good depth to surface dose ratio.

Brachytherapy↗
PubMed2001

[Brachytherapy of local prostatic carcinoma].

Brachytherapy of prostate cancer has become attractive in recent years in Germany. There are several radioactive sources available, which are physically different. Some of them are used as permanent or temporary implants. The permanent sources most frequently used are iodine 125, palladium 103, and gold 198. Iridium is a temporary implant. The techniques used in Germany are low-dose rate (LDR) and high-dose rate brachytherapy, which differ in dose distribution and patient population. The success of prostate cancer brachytherapy depends on patient selection and choosing the right source for the technique used. Best suited for LDR monotherapy is the low-risk patient with a prostate-specific antigen (PSA) level below 10 ng/ml, maximal tumor stage T2b, and a Gleason score of less than 7.

Brachytherapy↗
PubMed2004

Long-term clearance kinetics of inhaled ultrafine insoluble iridium particles from the rat lung, including transient translocation into secondary organs.

Recently it was speculated that ultrafine particles (UFP) may translocate from deposition sites in the lungs to systemic circulation and whether long-term clearance differs between ultrafine and micrometer-sized particles. We have studied lung retention and clearance kinetics in 12 healthy male adult WKY rats up to 6 mo after an inhalation of (192)Ir-radiolabeled, insoluble, ultrafine 15- to 20-nm iridium particles. Whole-body retention was followed by external gamma counting, and particle clearance kinetics were determined by excretion radioanalysis. Four rats each were sacrificed after 3 wk and 2 and 6 mo; all organs as well as tissues and the carcass were radioanalyzed to balance the entire deposited radioactivity of the particles. The most prominent fraction was retained in the lungs at each time point of sacrifice (26%, 15%, 6%, respectively), and clearance out of the body was solely via excretion. Extrapulmonary particle uptake did not continue to increase but decreased with time in liver, spleen, heart, and brain when compared to previous data obtained during the first 7 days after inhalation (Kreyling et al., 2002). UFP long-term lung retention derived from whole-body measurements was comparable to previously reported data using insoluble micrometer-sized particles (Bellmann et al., 1994; Lehnert et al., 1989). In addition, differential analysis including daily excretion data revealed a pattern of fractional particle clearance rate of the ultrafine iridium particles similar to that of micrometer-sized particles reported by Snipes et al. (1983) and Bailey et al. (1985).

Administration, Inhalation↗