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At least 307 records · Page 17Linked to original sources
PubMed1994

Breast cancer: primary treatment with external-beam radiation therapy and high-dose-rate iridium implantation.

PURPOSE: To evaluate a treatment for breast cancer and to demonstrate the safe use of iridium-192 high-dose-rate (HDR) implantations. MATERIALS AND METHODS: In December 1984, the authors began to use HDR Ir-192 brachytherapy to deliver an interstitial boost to the primary site in conservative breast cancer treatment. By December 1989, 212 patients with 216 tumors were treated with external-beam irradiation of 45-50 Gy to the whole breast, which was followed by an interstitial 10-Gy boost. Median follow-up was 62 months (range, 36-101 months). RESULTS: Ten patients (10 of 216 breasts, 4.6%) developed local tumor recurrences, and 36 (17.0%) had distant metastases. At 5 years, overall survival was 88%, local tumor control was 96%, and disease-free survival was 81%. There were no serious complications. CONCLUSION: The use of an HDR source as a boost to the primary tumor site after external-beam radiation therapy with a dose of 10 Gy in one fraction is a safe procedure and does not negatively affect cosmetic appearance.

Adult↗
PubMed2000

Brachytherapy with iridium-192 for bladder cancer.

OBJECTIVE: Patients with invasive bladder cancer often need radical cystectomy with its implications on quality of life. Bladder preservation combining surgery and radiotherapy could maintain quality of life without compromising tumor control. STUDY DESIGN: Twenty-eight selected patients with different stages of invasive bladder cancer were treated with preoperative external beam radiotherapy in a dosage depending on the tumor stage. Subsequently they underwent surgical exploration with or without partial cystectomy and insertion of source carrier tubes for afterloading with iridium-192. A close follow-up consisted of 3-monthly urine cytology, cystoscopy and yearly CT scan. RESULTS: Sixteen patients (57%) are alive with no evidence of disease. Five patients (18%) have died of non-cancer-related causes without evidence of recurrent tumor. Tumor progression was seen in 7 patients (25%). CONCLUSIONS: Interstitial radiation can result in long-term complete remission in patients with small solitary invasive bladder tumors. The afterloading technique is safe and effective. The selection of patients is the most relevant key to success.

Adult↗
PubMed1976

Production of weanling rat ventromedial and dorsomedial hypothalamic syndromes by electrolytic lesions with platinum-iridium electrodes.

Weanling Sprague-Dawley rats received bilateral anodic electrolytic lesions with platinum-iridium (PtIr) electrodes in the ventromedial (VMN) and dorsomedial (DMN) hypothalamic areas. Sham-operated rats served as controls. The rats were maintained for 48 days (experiment 1) and 33 days (experiment 2) and food intake, body weight (b.w.), nose-tail length and obesity index were recorded. The data of both experiments indicate that all parameters change in the same direction, as they do when lesions are produced with anodic stainless steel electrodes: in the VMN-P-lesioned animals, b.w. gains and overall mean food intake were normal, carcass fat increased and linear growth was reduced. In experiment 2, however, there was a temporary hyperphagia during the 1st 2 weeks of the study. In the DMN-lesioned rats, both ponderal and linear growth and food intake were decreased but body composition was normal. Plasma obtained at sacrifice in experiment 2 showed slight but significant hyperinsulinemia in the VMN rats (p less than 0.02 vs control and p less than 0.05 vs DMN rats). Prolactin (PRL) levels, on the other hand, were higher in the DMN-lesioned rats (p less than 0.05 vs control and p less than 0.02 vs VMN rats). The data indicate that the changes characteristic of the weanling rat VMN and DMN syndrmes are due to 'true' tissue destruction rather than to artifactitious side effects of the lesions. They also suggest, therefore, than an 'irritative focus' hypothesis is not required to account for the observed alterations. They further suggest that the DMN may play role in the control of PRL release.

Animals↗
PubMed1984

[Complications of preoperative high-dose-rate iridium-192 irradiation in cervix uteri carcinoma].

A report is given about the experience in preoperative, nonfractionated high-dose iridium-192 irradiation in cases of carcinoma of the cervix uteri. A few days prior to radical hysterectomy a dose of 20 Gy (in 2 cm distance) was applied locally by means of a loop-applicator (afterloading technique, Buchler). In cases without postoperative irradiation severe vaginal necroses, in cases with postoperative irradiation severe local and peripheral lesions were observed. In 8 of 10 cases irradiated pre- and postoperatively, another surgical intervention was necessary because of complications in the urinary or intestinal tract. This publication is presented as a warning for preoperative high-dose irradiation with 20 Gy applied locally in cases of carcinoma of the cervix uteri.

Brachytherapy↗
PubMed1997

Postoperative interstitial radiotherapy of keloids by iridium 192: a retrospective study of 46 treated scars.

BACKGROUND: Keloids are clinically vexacious scars characterized by a high recurrence rate after excision alone (50-100%). Many adjuvant techniques have been used with more or less convincing results. OBJECTIVE: The aim of this study is to show the efficiency of keloidectomy and postoperative interstitial radiotherapy by an iridium 192 wire. METHODS: During a 14-year period, 39 patients with keloids (46 keloids) were treated by this regimen. Seven patients had been previously treated by intralesional corticosteroids, surgery alone or postoperative interstitial radiotherapy, without improvement. A dose of 12 Gy (7 keloids) to 15 Gy (22 keloids) was delivered at a point 2.5 mm from the axis of the wire. For 17 keloids the dose schedule was 15 Gy at a point 5 mm to the wire. The median follow-up was 7 months. RESULTS: The overall success rate is close to 63%. A recurrence occurred in 14 cases without relation to the method used, the age or the localization of the lesions. There were no side effects observed. CONCLUSIONS: Postoperative interstitial radiotherapy represents an effective, unconstraining and safe treatment for keloids if the contraindications are respected.

Adolescent↗
PubMed1976

Angiocardiography with iridium-191m: an ultrashort-lived radionuclide (T1/2 4.9 sec).

Iridium-191m is a potential tracer for angiocardiography and may be of particular value in the evaluation of heart disease in children. It possesses a short half-life (4.9 sec), suitable photon energy (129 keV) and may be obtained as a generator product by decay of its long lived (15.3 day) parent 191 Os. An 191Os leads to 191mIr generator capable of providing 15 mCi of 191mIr in 1.5 ml of eluant is described. The separation of 191mIr from 191Os is achieved by absorbing 191OsC16-2 on an anion exchange resin. The generator employs an additional resin column which is replaced to prevent 191Os breakthrough to become excessive. By this procedure, the breakthrough may be kept below 0.001% over a period of at least one month and after multiple elutions.

Angiocardiography↗
PubMed1997

Iridium oxide-coated defibrillation electrode: reduced shock polarization and improved defibrillation efficacy.

BACKGROUND: Transvenous implantable cardioverter-defibrillator (ICD) leads are designed to deliver electric shocks to the heart for termination of ventricular dysrhythmias. However, the efficiency of different lead materials has not been well studied. This study compares an ICD lead coated with iridium oxide (IROX), a material that reduces shock-induced polarization, with an otherwise identical, uncoated lead. METHODS AND RESULTS: The defibrillation threshold (DFT) was determined in 13 swine with both IROX-coated and uncoated ICD leads paired with an uncoated "can" electrode. The leads were exchanged through a Teflon sheath to reproduce the intracardiac position. The delivered energy DFT of the IROX-coated lead was 15.9+/-5.4 J and was significantly lower than the delivered energy DFT of the uncoated lead (19.1+/-5.1 J; P<.006). The initial lead impedance was equivalent in both leads (IROX, 41.7+/-5.8 omega; uncoated, 41.3+/-4.7 omega; P=NS) at DFT. However, the impedance rose by 7.3+/-2.0 omega during the first phase and by 3.7+/-2 omega during the second phase with the uncoated lead, whereas the corresponding impedance change was 1.0+/-0.3 omega during phase 1 and 1.6+/-0.5 omega during phase 2 (P<.01 each phase) when the IROX-coated lead was used. CONCLUSIONS: This study shows that an IROX coating of this lead system significantly lowers the DFT energy in the swine model. The blunting of the impedance rise by the IROX coating that is seen is consistent with a reduction in electrode polarization.

Animals↗
PubMed2005

Randomized trial comparing iridium implant plus external-beam radiation therapy with external-beam radiation therapy alone in node-negative locally advanced cancer of the prostate.

PURPOSE: To determine if iridium implant (IM) and external-beam radiation therapy (EBRT) is better than standard EBRT in locally advanced prostate cancer. METHODS: Patients with T2 and T3 prostate cancer with no evidence of metastatic disease were randomly assigned to EBRT of 66 Gy in 33 fractions during 6.5 weeks or to IM of 35 Gy delivered to the prostate during 48 hours plus EBRT of 40 Gy in 20 fractions during 4 weeks. The primary outcome consisted of biochemical or clinical failure (BCF). BCF was defined by biochemical failure, clinical failure, or death as a result of prostate cancer. Secondary outcomes included 2-year postradiation biopsy positivity, toxicity, and survival. RESULTS: Between 1992 and 1997, 51 patients were randomly assigned to receive IM plus EBRT, and 53 patients were randomly assigned to receive EBRT alone. The median follow-up was 8.2 years. In the IM plus EBRT arm, 17 patients (29%) experienced BCF compared with 33 patients (61%) in the EBRT arm (hazard ratio, 0.42; P = .0024). Eighty-seven patients (84%) had a postradiation biopsy; 10 (24%) of 42 in the IM plus EBRT arm had biopsy positivity compared with 23 (51%) of 45 in the EBRT arm (odds ratio, 0.30; P = .015). Overall survival was 94% in the IM plus EBRT arm versus 92% in the EBRT arm. CONCLUSION: The combination of IM plus EBRT was superior to EBRT alone for BCF and postradiation biopsy. This trial provides evidence that higher doses of radiation delivered in a shorter duration result in better local as well as biochemical control in locally advanced prostrate cancer.

Adenocarcinoma↗
PubMed1987

Radiation control in the intensive care unit for high intensity iridium-192 brain implants.

A bedside lead cubicle was designed to minimize the radiation exposure of intensive care unit staff during routine interstitial brain irradiation by removable, high intensity iridium-192. The cubicle shields the patient without restricting intensive care routines. The design specifications were confirmed by exposure measurements around the shield with an implanted anthropomorphic phantom simulating the patient situation. The cubicle reduces the exposure rate around an implant patient by as much as 90%, with the exposure level not exceeding 0.1 mR/hour/mg of radium-equivalent 192Ir. Evaluation of data accumulated for the past 3 years has shown that the exposure levels of individual attending nurses are 0.12 to 0.36 mR/mg of radium-equivalent 192Ir per 12-hour shift. The corresponding range for entire nursing teams varies between 0.18 and 0.26. A radiation control index (exposure per mg of radium-equivalent 192Ir per nurse-hour) is thus defined for individual nurses and nursing teams; this index is a significant guide to the planning of nurse rotations for brain implant patients with various 192Ir loads. The bedside shield reduces exposure from 192Ir implants by a factor of about 20, as expected, and the exposure from the lower energy radioisotope iodine-125 is barely detectable.

Brachytherapy↗
PubMed1989

Interstitial iridium-192 implantation for malignant brain tumours. Part II: Clinical experience.

The treatment results of 37 patients with malignant brain neoplasms treated with a computed-tomography-guided stereotactic iridium-192 implant are reviewed. Of these, 29 patients with high-grade gliomas (20 with glioblastoma multiforme (GBM), nine with anaplastic astrocytoma (AA] received an implant as part of their initial management. The median survival was 14.5 and 15.5 months in the patients with previously untreated GBM and AA, respectively. In those patients with recurrent tumour after external-beam irradiation, durable local control over a year was achieved with implantation. Increasing the total tumour dose from 120 to 160 Gy did not improve survival or local control. Karnofsky Performance Status (KPS) was used as an indicator of quality of life and was seen to decrease with a median interval of 8.5 months following treatment. No severe complications were noted in the entire group of patients treated with this implant procedure.

Adult↗
PubMed1991

Calibration of a Microselectron HDR iridium 192 source.

A method for the calibration of the output, in terms of an air kerma rate, of the high activity miniature iridium 192 sources used in the Microselectron HDR afterloading unit is described. An air kerma rate is measured using a calibrated thimble chamber in an "in-air" calibration jig. The results are compared with an air kerma rate derived from the manufacturer's test certificate. In some cases, the ionization chamber measurements have been followed by a further calibration check using thermoluminescent dosimetry. Other checks carried out when a new source is received are also briefly described.

Brachytherapy↗
PubMed2000

Calibration of pre-cut iridium-192 wires for low dose rate interstitial brachytherapy using a Farmer-type ionization chamber.

A technique, originally developed for calibrating small low activity caesium sources, which uses a Farmer-type ionization chamber, has been further developed for use with iridium wires. Correction factors have been generated to account for the finite source and detector sizes, and attenuation in the source carriers. The air kerma calibration factor for heavily filtered 280 kV X-rays was used for reference back to the National Standard. The results of this calibration method have been compared with the calibration figures given by the manufacturers over a 5 year period for the emissions from 50 batches of wires of varying strengths. Agreement to within +/- 3.2% was achieved in all cases, establishing that the method is satisfactory for acceptance testing purposes. The mean agreement was good to within 0.2%, but the possibility of a systematic error of between 1% and 3% existing both in this method and in the method used by the manufacturer is discussed.

Brachytherapy↗
PubMed2000

Single dose irradiation response of pig skin: a comparison of brachytherapy using a single, high dose rate iridium-192 stepping source with 200 kV X-rays.

An experimental brachytherapy model has been developed to study acute and late normal tissue reactions as a tool to examine the effects of clinically relevant multifractionation schedules. Pig skin was used as a model since its morphology, structure, cell kinetics and radiation-induced responses are similar to human skin. Brachytherapy was performed using a microSelectron high dose rate (HDR) afterloading machine with a single stepping source and a custom-made template. In this study the acute epidermal reactions of erythema and moist desquamation and the late dermal reactions of dusky mauve erythema and necrosis were evaluated after single doses of irradiation over a follow-up period of 16 weeks. The major aims of this work were: (a) to compare the effects of iridium-192 (192Ir) irradiation with effects after X-irradiation; (b) to compare the skin reactions in Yorkshire and Large White pigs; and (c) to standardize the methodology. For 192Ir irradiation with 100% isodose at the skin surface, the 95% isodose was estimated at the basal membrane, while the 80% isodose covered the dermal fat layers. After HDR 192Ir irradiation of Yorkshire pig skin the ED50 values (95% isodose) for moderate/severe erythema and moist desquamation were 24.8 Gy and 31.9 Gy, respectively. The associated mean latent period (+/- SD) was 39 +/- 7 days for both skin reactions. Late skin responses of dusky mauve erythema and dermal necrosis were characterized by ED50 values (80% isodose) of 16.3 Gy and 19.5 Gy, with latent periods of 58 +/- 7 days and 76 +/- 12 days, respectively. After X-irradiation, the incidence of the various skin reactions and their latent periods were similar. Acute and late reactions were well separated in time. The occurrence of skin reactions and the incidence of effects were comparable in Yorkshire and Large White pigs for both X-irradiation and HDR 192Ir brachytherapy. This pig skin model is feasible for future studies on clinically relevant multifractionation schedules in a brachytherapy setting.

Animals↗
PubMed1986

Interstitial hyperthermia and iridium brachytherapy in treatment of malignant glioma. A phase I clinical trial.

An oncolytic effect of hyperthermia in the 42 degrees to 43 degrees C range has been previously demonstrated in cell culture and animal models. To apply this modality clinically, an interstitial microwave antenna array system has been developed for the delivery of controlled hyperthermia to an intracranial tumor volume, and a Phase I clinical trial involving six patients with malignant gliomas was undertaken. The protocol to study technical feasibility and patient tolerance combined interstitial iridium-192 irradiation and interstitial hyperthermia with 60-minute hyperthermia sessions immediately before and after brachytherapy. After-loading catheters suitable for both treatment modalities were implanted using a computerized tomography-assisted technique. Thermometry data confirmed the ability of a microwave antenna system to achieve reliable temperature distributions, and reasonable patient tolerance was documented.

Adult↗
PubMed2006

High dose-rate brachytherapy of prostate cancer utilising Iridium-192 after-loading technique: technical and methodological aspects.

The aim of this study was to focus on certain characteristic problems associated with Iridium-192 high dose-rate brachytherapy (Ir-192 HDR-BT) in combination with external beam radiation therapy (EBRT) in the treatment of patients with localised prostate cancer. Over a period of 16 years, >2,000 patients with prostate cancer have been treated in Sweden with a combination of two fractions of 10 Gy Ir-192 HDR-BT and 50 Gy of fractionated EBRT. Although this treatment is usually well tolerated, there are biological and technical factors to be considered before and during the treatment of the patient to avoid side effects or under-treatment of the target volume. Some of the problems facing the doctors are transducer stability, needle deviation, target definition, target motion, pubic arch interference, concomitant diseases and tolerance doses for different organs at risk. These problems are discussed and possible solutions are presented in this study.

Brachytherapy↗
PubMedDate not supplied

Iridium-192 interstitial brachytherapy as adjunctive treatment for canine cutaneous mast cell tumors.

Eleven dogs with cutaneous mast cell tumors (MCTs) were treated with surgery and iridium-192 ((192)Ir) interstitial brachytherapy. Minimum tumor doses ranged from 47.2 to 63.3 Gy. Treated tumors were classified as grade II (n=7) or III (n=4). Five dogs had recurrences with a median progression-free interval of 1391 days, and six dogs had no recurrence at a median follow-up time of 942 days. Acute adverse effects were well tolerated, and late effects were mild. One dog developed a second tumor of a different cell type in the radiation treatment field.

Animals↗
PubMed2001

[High-dose rate iridium-192 brachytherapy combined with external beam radiotherapy for localized prostate cancer].

PURPOSE: We report our technique and also preliminary results in the cases with localized prostate cancer treated by the combination of high-dose rate Iridium-192 (HDR-Ir192) brachytherapy and external irradiation. MATERIALS AND METHODS: From June 1999 to August 2000, 17 patients were treated by the combination of HDR-Ir 192 and external beam. The mean age of patients was 72 years (range, 48-81 years). The clinical stage was B1 in 5, B2 in 7 and C (no cancer with seminal vesicle) in 5 cases. Of 10 patients without neoadjuvant hormonal therapy, the median initial pretreatment PSA was 15.3 ng/ml (6.93-222.32 ng/ml). The treatment was given by HDR-Ir 192 brachytherapy (6 Gy x 3 times/2 days) and external beam irradiation (40 or 45 Gy). The brachytherapy was given using TRUS guided percutaneously inserted temporary needles with a high dose rate remote afterloading control. Local control was evaluated by digital rectal examination. TRUS-guided biopsies and serum PSA evaluations. Follow-up ranged from 2 to 14 months, with a median of 8 months. RESULTS: In 4 (40.0%) of 10 patients without neoadjuvant hormonal therapy the level of serum PSA was decreased to less than 4.0 ng/ml within 3 months after the therapy. The effective grade in the biopsy specimens of 8 patients without neoadjuvant hormonal therapy was Grade Ob in 4, Grade 1 in 1, Grade 3 in 3 cases at 3 months after the therapy. No severe intra- or peri-operative complications occurred. CONCLUSION: The combined radiotherapy treatment is safe and effective for use in the patients with localized prostate cancer. However, more comprehensive studies involving long-term follow-up and great numbers of the cases with localized prostate cancer treated by the combination of HDR-Ir 192 brachytherapy and external irradiation will be necessary to determine whether this therapy contributes to better prognosis.

Aged↗