SEARCH · PubMed Health

Results for “IRIDIUM, RADIOACTIVE”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 181 records · Page 10Linked to original sources

PubMed1987

Removable, adjustable and reusable implants for stereotactic interstitial radiosurgery of brain tumors.

Sixty primary brain tumors (gliomas) were treated by interstitial radiosurgery using 192Ir according to a protocol based on the size of the tumor. In all cases, the radioactive wires were left in place for periods ranging from 5 to 10 days, according to dosimetry calculations, and then removed, which was made possible by the use of removable implants. The stainless steel tubes are occluded on their inner side and adjustable in length depending on the depth of the tumor, and are introduced through screws inserted into the skull in an array depending on the preliminary dosimetry. The tubes were afterloaded with 192Ir and removed at the end of the calculated time. Forty-six patients (18 low-grade and 28 malignant gliomas) were treated using this method. One small hematoma was evacuated and no sepsis occurred.

Brachytherapy↗

PubMed1995

Implantation guidelines for 169 Yb seed interstitial treatments.

The adequacy of an interstitial implant carried out with a new radioactive source, the 169 Yb seed model X1267, has been examined by computing volumetric indices based on dose-volume histograms. The comparison of these indices with the ones computed for 125I seed implantations shows that the use of ytterbium seeds presents an improvement of the dose homogeneity in interstitial implants. This is due to the significant build-up associated with 169 Yb photons that reduces the rapid dose fall-off with the distance from the source. Moreover, relative to 192Ir, the lower photon energy gives 169 Yb the advantage in clinical use of reduced radiation exposure (i) to health care workers, (ii) to relatives of treated patients and (iii) to healthy neighbouring tissues of the patients if appropriate thin shielding is used.

Biophysical Phenomena↗

PubMedDate not supplied

New perspectives in brachycurietherapy of malignant brain tumors. Preliminary report.

Between 1980 and 1988, 16 patients (9 females, 7 males) with malignant neuroepithelial tumors of the brain were treated by brachycurietherapy (BCT) and external radiation therapy (ERT) in a phase II nonrandomized study. There were 13 grade III and 3 grade IV tumors according to the WHO classification. Five patients in the grade III group who showed anaplastic foci in a generally grade II background were separately examined. Six patients received only BCT whereas 10 patients were treated by a combination of BCT and ERT, according to the tumor volume. We utilized as radioactive sources 192Ir in 14 cases and 125I in 2. Thirteen patients underwent permanent implant, 3 others received temporary irradiation with removable afterloaded catheters. The target volume was less than 50 cc in 8 cases, between 50 and 100 cc in 7, and larger than 100 cc in 1 patient. The total dose at the periphery of these volume ranged between 70 and 144 Gy. The result were analyzed referring to the following aspects: performance status, survival, side effects, grading. The impact of BCT was analyzed especially in a grade III with anaplastic foci group which showed a median survival of 6 years compared with only 2 years median survival of the pure grade III group.

Brachytherapy↗

PubMed2004

Distortions induced by radioactive seeds into interstitial brachytherapy dose distributions.

In a previous article, we presented development and verification of an integral transport equation-based deterministic algorithm for computing three-dimensional brachytherapy dose distributions. Recently, we have included fluorescence radiation physics and parallel computation to the standing algorithms so that we can compute dose distributions for a large set of seeds without resorting to the superposition methods. The introduction of parallel computing capability provided a means to compute the dose distribution for multiple seeds in a simultaneous manner. This provided a way to study strong heterogeneity and shadow effects induced by the presence of multiple seeds in an interstitial brachytherapy implant. This article presents the algorithm for computing fluorescence radiation, algorithm for parallel computing, and display results for an 81-seed implant that has a perfect and imperfect lattice. The dosimetry data for a single model 6711 seeds is presented for verification and heterogeneity factor computations using simultaneous and superposition techniques are presented.

Artifacts↗

PubMed1981

Irradiation with external beam and interstitial radioactive implant as primary treatment for early carcinoma of the breast.

The locoregional control of 60 to 61 patients supports the results published by other centers and compares favorably with results of any surgical series. The cosmetic results are excellent with only three of 61 patients having severe fibrosis of the breast develop. No rib fractures, skin ulcerations, symptomatic radiation pneumonitis, edema of the arm or limitation of arm movement have been observed as complications. Ten of the 28 patients who have had axillary dissection had transient edema of the breast develop. Results of numerous studies suggest that primary radiotherapy without mastectomy is appropriate treatment for early carcinoma of the breast. The accessibility of the breast makes it relatively easy to deliver curative doses of radiation with minimal damage to surrounding normal tissues. The cumulative radiotherapy experience has demonstrated the gratifying results of not only maintaining a rather normal breast but also avoiding the negative physical and psychologic repercussions of the mastectomy. Radiation therapy is an alternative to Halsted's radical mastectomy.

Brachytherapy↗

PubMed1985

Physical optimization of afterloading techniques.

Physical optimization in brachytherapy refers to the process of determining the radioactive-source configuration which yields a desired dose distribution. In manually afterloaded intracavitary therapy for cervix cancer, discrete source strengths are selected iteratively to minimize the sum of squares of differences between trial and target doses. For remote afterloading with a stepping-source device, optimized (continuously variable) dwell times are obtained, either iteratively or analytically, to give least squares approximations to dose at an arbitrary number of points; in vaginal irradiation for endometrial cancer, the objective has included dose uniformity at applicator surface points in addition to a tapered contour of target dose at depth. For template-guided interstitial implants, seed placement at rectangular-grid mesh points may be least squares optimized within target volumes defined by computerized tomography; effective optimization is possible only for (uniform) seed strength high enough that the desired average peripheral dose is achieved with a significant fraction of empty seed locations.

Brachytherapy↗

PubMed1993

Extending the limits of lung cancer resection.

Patients with locally advanced bronchogenic carcinoma are often considered to have unresectable disease because of invasion into vital structures, or they undergo resection with questionable or involved margins, which results in local recurrence later. Brachytherapy (direct application of radioactive sources to the tumor bed) offers the potential to provide tumoricidal doses of radiation to the target area with minimal toxicity to surrounding structures. In this study, one of two different techniques of brachytherapy was utilized to treat 15 highly selected patients with histologically positive (n = 8) or suspicious (n = 7) margins after resection. The techniques were easy to apply and were not associated with any complications directly related to their use. One postoperative death resulted from a perforated peptic ulcer. In the remaining 14 patients, at a mean follow-up of 38 months, local control was complete in 12 (86%) patients, and 8 patients are alive, with 7 free of disease. Thoracic brachytherapy may offer the potential for cure to patients whose disease would otherwise be considered inoperable.

Brachytherapy↗

PubMed2006

Reported events of stolen radioactive sources in Texas from 1956 to 2000.

Incident reports describing stolen source events in Texas from the years 1956 to 2000 were obtained from the Texas Department of Health-Bureau of Radiation Control and recorded into a computerized database using a pre-established set of codes. The data were then analyzed for the identification and characterization of trends. Over the 45-y period of analysis, 113 sources were reported as stolen. The radionuclides most commonly reported in theft events were Am, Cs, and Ir. The proportion of sources including Am as the sole source or Am combined with Be, or as a companion source with Cs, represented 56% of the total reported as stolen. Key risk factors identified as associated with source theft appear to include portability status, transportation status, transporter status, and radionuclide type. Based on the observations noted, suggested improved security measures are postulated including additional permitting controls, enhanced inspections, improved locking and storage procedures, and steps for communication to the public to enhance the prospects for recovery. Suggested enhancements to further improve data collection are proposed so that crime prevention information can be derived in future research.

Americium↗

PubMed1998

An examination of radiation exposure to clinical staff from patients implanted with 137Cs and 192Ir for the treatment of gynecologic malignancies.

The treatment of cancers by placement of radioactive materials within or adjacent to a tumor is clinically known as brachytherapy. Although the intracavitary treatment of gynecologic cancers using 137Cs has been in widespread use for nearly a century, interstitial techniques using 192Ir have developed within the last decade. Both procedures are performed as temporary implants and typically require a hospital stay of approximately 48 h. Significant differences in source strengths, loading conditions, and patient care requirements are visible between the intracavitary and interstitial techniques. Facilities that are experienced in the use of intracavitary techniques may lack clinical experience in the use of newer interstitial procedures. An examination of radiation exposure to the radiation oncology staff administering the treatment, exposure rate at frequently occupied points in the patient room, and exposure to the nursing staff will be of value to those institutions considering integration of interstitial brachytherapy techniques into their department.

Body Burden↗

PubMed2003

[Brachytherapy for coronary restenosis: state of art in 2003].

Based on therapeutic approach for benign diseases, vascular brachytherapy decreases smooth vascular muscle cells proliferation and multiplication which lead to the formation of the neo-intima. The radioactive positive action affects arterial recoil due to post angioplasty vessel injury. Randomised studies has shown good angiographic results up to 6 months of follow-up, with 50% in-stent restenosis rate decrease and on the analysed segment as well. Decrease on Mace and TLR show statistically significance. Results don't correlate with emitter and bêta emitters had been introduced in France recently. Vascular brachytherapy is actually indicated for in-stent restenosis, there is no evidence to perform this treatment for de novo lesion. Geographic miss, source centering, late thrombosis and pullback procedure may interfere with treatment quality. IVUS allows best target volume determination to a higher quality level. Internationals guidelines such as Eva-Gec-Estro recommendations could increase treatment safety and enable development of an optimal technique.

Angioplasty, Balloon, Coronary↗

PubMed1992

192iridium brachytherapy, using an intracavitary afterload device, for treatment of intranasal neoplasms in dogs.

After surgical removal of a primary intranasal neoplasm, an implant device, designed to deliver 192iridium (192Ir) brachytherapy, was positioned in the nasal cavity of 8 dogs. Ribbons containing 192Ir seeds were placed in the device, using an afterloading technique. Dosimetry, to a dose of 7,000 to 10,000 centiGray (cGy), was calculated to encompass the site previously occupied by the tumor and a 1-cm margin of surrounding normal tissue. The quantity of 192Ir implanted varied between 16.69 and 100.80 mg of radium equivalent. The duration of implantation ranged from 90 to 168 hours. All dogs tolerated the implant well, but had a mucoid nasal discharge after radiotherapy. The implant device allowed rapid application and removal of the radioactive ribbons. Mean (+/- SD) radiation exposure to each radiotherapist during seed loading and unloading was 14.4 (+/- 5.3) and 4.5 (+/- 0.9) mrem, respectively. A uniform dose distribution around the intranasal implant device was achieved; however, dogs that received doses in excess of 9,400 cGy at the dorsolateral surface of the nose and/or hard palate had bone and soft tissue necrosis between 70 and 120 days after treatment. One dog was euthanatized 50 days after treatment because of metastatic disease, and 2 dogs were euthanatized because of local tumor recurrence at 125 and 212 days. Death, considered unrelated to treatment, occurred in 1 dog that was euthanatized 27 days after treatment and in 3 dogs that died 30, 93, and 456 days after treatment. Necropsy was performed on 3 of these dogs and evidence of intranasal neoplasia was not observed. One dog remained disease-free at 587 days after treatment.

Adenocarcinoma↗

PubMed2006

High-dose-rate brachytherapy for small-sized peripherally located lung cancer.

BACKGROUND: The demand for minimally invasive therapies is increasing in the treatment of small peripheral non-small cell lung cancer (NSCLC). PATIENTS AND METHODS: Twelve patients with T1-2 N0 M0 peripheral NSCLC were treated by high-dose-rate brachytherapy with (192)Ir radioactive source. RESULTS: A (192)Ir source was introduced into the tumors percutaneously in five patients (percutaneous brachytherapy) or transbronchially in seven patients (transbronchial brachytherapy). Whereas irradiation was performed with a single fraction of 20 Gy in percutaneous brachytherapy, it was hypofractionated from 5 x 5 Gy to 2 x 12.5 Gy in transbronchial brachytherapy. Complications were generally mild in all patients, although focal radiation pneumonitis was observed in most patients. Primary recurrence occurred in three patients, including one with a T2 tumor and one treated by brachytherapy as a salvage treatment for recurrence after conformal radiotherapy. When brachytherapy is evaluated as a primary treatment for T1 N0 M0 NSCLC, local control rate is 88.9% and estimated 5-year survival rate is between 60% and 70%. CONCLUSION: Brachytherapy has a potential to be a method to treat peripheral T1 N0 M0 NSCLC.

Aged↗

PubMed1984

Shielding hospital rooms for brachytherapy patients: design, regulatory and cost/benefit factors.

The current regulations of the U.S. Nuclear Regulatory Commission (NRC) normally require limitation of radiation exposure in any part of unrestricted occupied areas to 2 mrem in any one hour and to 100 mrem in 7 days. To meet these limits when patients are treated therapeutically with radioactive materials, it is advisable to designate specific rooms in a hospital and often necessary to incorporate substantial costly shielding into one or more walls and the room door. Plans have been formulated for shielding existing hospital rooms housing brachytherapy patients receiving 192Ir and 137Cs therapy in order to meet the above NRC requirements for adjacent corridors and rooms. Typical shielding thicknesses required are 4-6 in. of concrete for certain walls and 1/4 in. of lead in the doors. Shielding costs are approx. $6000 per room for one shielded wall and a shielded door. Applying recent estimates of the cancer risk from low-level gamma radiation, the cost of shielding per cancer fatality averted has been estimated to range from $1.8 million to $10.9 million. Cost/benefit comparisons with many other life-saving activities suggest that these costs and the application of the 2 mrem/hr limit which necessitated them are not justified.

Brachytherapy↗

PubMed1991

[Interstitial Ir-192 afterloading therapy with sequential warm-water hyperthermia].

For selective heating of superficially located or easily accessible tumors interstitial hyperthermia has become an increasing popular method in combination with interstitial radioactive implants. At our institution the hyperthermia treatment is performed utilizing the warm water system KHS-9, which is adapted to our Ir-192 high-dose-rate afterloading device, so that the same hollow needles for the interstitial radiation can be used for the heating procedure. So far, this technique has been applied for the treatment of primary and carcinomas, gynecological recurrences, and metastases of malignant melanomas after preceding in vitro measurements of temperature distribution. As a result both, in vitro and in vivo investigations showed good homogeneity of the temperature throughout the heated volume. Analysing the temperature data of in vivo measurements the maximum deviation of temperature was found to be 1.5 degrees C. When using a needle spacing of 8 mm, the temperature required for clinical application (42.5 degrees C) could be maintained in all heat treatments with a preselected water temperature of 46 degrees C to 49.5 degrees C.

Anus Neoplasms↗

PubMed2006

The optimization of dose delivery for intraoperative high-dose-rate radiation therapy using curved HAM applicators.

BACKGROUND AND PURPOSE: To determine the effect of the curvature of Harrison-Anderson-Mick applicators on the dose distribution in high-dose-rate intraoperative radiation therapy (HDR-IORT). MATERIAL AND METHODS: Treatment planning was performed with flat applicators using (192)Ir as the radioactive source, and dwell times were optimized using dose-point optimization techniques. These optimized dwell times were then used for the curved applicators, and the dose distributions that would actually be delivered to patients were determined. RESULTS: The dose directly below the central catheter was strongly dependent on the curvature of the applicator. Steep parabolic curves caused underdoses of as much as 19% at a point 1cm from the convex side of the applicator. The rate of dose reduction with increasing distance from the applicator surface was also a function of the curvature of the applicator. CONCLUSIONS: The curvature of the applicator profoundly affects dosimetry and can be exploited to optimize coverage of the target during HDR-IORT procedures. To ensure accurate dose delivery, these dose perturbations must be accounted for in the planning process. We recommend maintaining a dosimetry atlas of various applicator sizes and curvatures in addition to one for flat applicators.

Brachytherapy↗

PubMed1983

Permanent Iodine-125 implants in head and neck cancer.

One hundred twenty-four patients were treated with advanced recurrent head and neck cancer for palliation with radioactive permanent Iodine-125 (125I) implants. Complete regression occurred in 71% of the 118 lesions for which evaluation was possible and greater than 50% regression occurred in 18%; no meaningful regression occurred in 11%. Local recurrence of cancer was subsequently seen in 21% of the lesions which had regressed completely, in 55% of those which had regressed incompletely, and in 100% of those which had not regressed. The incidence of serious complications was 5.5%. Overall, in 64% of the instances the implanted lesions remained controlled until the patient's death, usually due to progression of cancer elsewhere in the body. It is concluded that permanent 125I implants offer useful palliation to the patient with recurrent head and neck cancer with a minimum of toxicity and inconvenience. Because of their low toxicity even after prior full-course external radiation therapy, the authors are currently investigating their use as planned adjunct to external radiation therapy and chemotherapy in the initial definitive management of patients with locally advanced head and neck cancer.

Brachytherapy↗

PubMed1991

Interstitial IR-192 implants of the oral cavity: the planning and construction of volume implants.

The success of radioactive implant therapy for head and neck carcinomas depends critically on careful planning and execution of the implant procedure. In this paper we discuss our experience with oral tongue and floor of mouth implants, and some innovations introduced to facilitate these procedures. Implants were carried out using standard angiocatheters modified with magnetic caps at the open end and terminated with Teflon spacers and lead shot at the closed end. The importance of accurate source placement and careful determination of the target dose rate is discussed with numerical examples. Differential hot-loading of sources is clearly indicated in cases of extension of the lesion to the dorsal or lateral tongue surface. For dorsal surface extension the use of Teflon spacers at the closed ends of the catheters helps to ensure adequate coverage of the target volume with the higher dose region enclosing the demonstrable tumor. All 10 patients implanted with this technique are controlled without recurrence at a median follow-up of 38 months. The two complications observed appeared to be associated with excessive hot-loading of edge plane sources.

Brachytherapy↗

PubMedDate not supplied

Evaluation of the buildup effect of an 192Ir high dose-rate brachytherapy source.

The buildup effect of the 192Ir radioactive source employed as a gamma emitter of the Selectron high dose-rate (HDR) afterloader was evaluated by studying the ratio of exposure in water to exposure in air as a function of distance. In 1968, Meisberger et al. [Radiology 90, 953-957 (1968)] calculated a third-order polynomial fit to a selected average between measured and calculated values. The objective of this investigation, however, is to evaluate the factor for the 192Ir source configuration used in the HDR system, which was different from the source design used by Meisberger et al. This paper presents the measured ratio using an ionization chamber and the calculated ratio using a Monte Carlo simulation code. The experimental and theoretical results show only minor disagreement with the data of Meisberger et al. However, the results show significant disagreement when they are compared to the model developed by van Kleffens and Star [Int. J. Radiat. Oncol. Biol. Phys. 5 557-563 (1979)], which may indicate the need to reevaluate the algorithm presently employed in HDR treatment planning system. The comparison with other published data will be discussed.

Algorithms↗