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B Thomadsen

Publications and source records attributed to B Thomadsen.

8 recordsLinked to original sources
PubMed2000

The American Brachytherapy Society recommendations for high-dose-rate brachytherapy for carcinoma of the cervix.

PURPOSE: This report presents guidelines for using high-dose-rate (HDR) brachytherapy in the management of patients with cervical cancer, taking into consideration the current availability of resources in most institutions. METHODS: Members of the American Brachytherapy Society (ABS) with expertise in HDR brachytherapy for cervical cancer performed a literature review, supplemented their clinical experience to formulate guidelines for HDR brachytherapy of cervical cancer. RESULTS: The ABS strongly recommends that definitive irradiation for cervical carcinoma must include brachytherapy as a component. Each institution should follow a consistent treatment policy when performing HDR brachytherapy, including complete documentation of treatment parameters and correlation with clinical outcome, such as pelvic control, survival, and complications. The goals are to treat Point A to at least a total low-dose-rate (LDR) equivalent of 80-85 Gy for early stage disease and 85-90 Gy for advanced stage. The pelvic sidewall dose recommendations are 50-55 Gy for early lesions and 55-65 Gy for advanced ones. The relative doses given by external beam radiation therapy (EBRT) vs. brachytherapy depend upon the initial volume of disease, the ability to displace the bladder and rectum, the degree of tumor regression during pelvic irradiation, and institutional preference. As with LDR brachytherapy, every attempt should be made to keep the bladder and rectal doses below 80 Gy and 75 Gy LDR equivalent doses, respectively. Interstitial brachytherapy should be considered for patients with disease that cannot be optimally encompassed by intracavitary brachytherapy. While recognizing that many efficacious HDR fractionation schedules exist, some suggested dose and fractionation schemes for combining the EBRT with HDR brachytherapy for each stage of disease are presented. These recommendations are intended only as guidelines, and the suggested fractionation schemes have not been thoroughly tested. The responsibility for the medical decisions ultimately rests with the treating radiation oncologist. CONCLUSION: Guidelines are established for HDR brachytherapy for cervical cancer. Practitioners and cooperative groups are encouraged to use these guidelines to formulate their treatment and dose-reporting policies. These guidelines will be modified, as image-based treatment becomes more widely available.

Antineoplastic Agents↗
PubMed1999

Assessment of the strength of individual 192Ir seeds in ribbons.

Assessing the strength of individual seed-type sources in ribbon assembles remains a challenge in brachytherapy quality assurance. Geometries to measure a single source in the ribbon usually fail because of low signals if using very thick shielding to block the radiation from the other sources, or contributions from all the other sources if they are not shielded well. A normal well-type chamber with partial lead shielding forming a small slot provides a differential response along the chamber axis that, through a deconvolution/simultaneous-equations technique, sorts the contributions from each source, allowing the derivation of each source's strength.

Brachytherapy↗
PubMed1995

Evaluation of water-equivalent plastics as phantom material for electron-beam dosimetry.

This investigation evaluated samples of three phantom materials designed as substitutes for water for electron beam calibration and depth ionization measurements. Two of the materials are commercially available (photon-electron Solid Water and Plastic Water), while the third (Homat) is not. Applying the values for water for all factors used in the calibration protocol of the American Association of Physicists in Medicine [Task Group 21, Med. Phys. 10, 741-771 (1983)] results in a discrepancy in calculated peak dose rates. Eliminating this discrepancy requires the additional inclusion of a multiplicative correction factor of approximately 1.015 for beam energies below 10 MeV, 1.01 for beam energies between 10 and 12 MeV, and 1.005 for beam energies above 12 MeV. Measurements for R50 and extrapolated range may be made in these materials with no corrections. Some improvement can be made in the performance of the phantom material by optimizing the match to water specifically for electron beams without regard for photon beam response. As with all radiation oncology apparatus, calibration phantoms need acceptance testing before routine use.

Electrons↗
PubMed1992

Sequential comparison of low dose rate and hyperfractionated high dose rate endobronchial radiation for malignant airway occlusion.

A pilot trial (S2) was conducted at the University of Wisconsin to determine the feasibility, efficacy, and toxicity of hyperfractionated high dose rate endobronchial radiation. To avoid multiple bronchoscopies, an optimized hyperfractionated schema was derived from the linear-quadratic model. Utilizing a single bronchoscopy, 31 patients with malignant airway occlusion received 4 Gy x 4 fractions over 2 days at 2 cm from source center using a high dose rate remote afterloader. Response and morbidity were compared to a previous trial (S1) in which 66 patients were treated with conventional low dose rate endobronchial radiation. Response was assessed by change in performance status, symptom resolution, percent of lifetime rendered symptom-free or improved, and radiographic reaeration. These parameters were highly comparable between the two groups. The mean ECOG performance status improved from 2.2 to 1.8 for S1 and 2.1 to 1.6 for S2; symptom improvement or resolution was noted in 78% for S1 and 79% for S2; lifetime rendered symptom-free or improved was 54% for S1 and 57% for S2; and the overall radiographic response rate was 78% for S1 and 85% for S2. The overall incidence of fistulae was 7/101. We conclude that endobronchial radiation is an effective and safe modality for palliation, and hyperfractionated high dose rate endobronchial radiation achieves responses similar to low dose rate endobronchial radiation with a similar complication rate.

Airway Obstruction↗
PubMed1983

Fortification of existing rooms used for brachytherapy patients.

Often, the radiation exposure levels around brachytherapy patient rooms exceed the limits allowed by Nuclear Regulatory Commission (NRC) regulations and National Council on Radiation Protection (NCRP) recommendations. Since a neighboring patient may be present in the radiation field from a brachytherapy patient, or patients, continuously for 7 days, the dose equivalent rate must not exceed 6 muSv/hr (0.6 mrem/hr). Several boundary conditions constrain solutions to the problem of excessive radiation levels: (1) the cost should not be recurring, (2) the rooms used for brachytherapy patients must be compatible with use for nonbrachytherapy patients, (3) free access through halls must be maintained, (4) all brachytherapy rooms must be compatible with independent use, (5) shielding must not eliminate space required for a resuscitation cart, (6) shielding should not require storage, (7) the weight of shielding must remain within the tolerance of the floor, and (8) the location of beds must match utility outlets in the wall. Possible solutions to the problem include leaving rooms empty around the patient, use of portable shields, or the addition of substantial amounts of shielding material in the walls of the brachytherapy rooms, as well as changing the radionuclides routinely used. The optimum solution for a given institution depends on the frequency of brachytherapy procedures, bed occupancy rate, and available empty space.

Brachytherapy↗