International journal of radiation oncology, biology, physics
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Int. J. Radiat. Oncol. Biol. Phys. · Jan 1997
Pulsed brachytherapy as a substitute for continuous low dose rate: an in vitro study with human carcinoma cells.
Pulsed dose rate (PDR) brachytherapy as a substitute for continuous low dose rate (CLDR) has the potential to be a useful option in brachytherapy. However, the frequency and duration of pulses that will produce results practically equivalent to CLDR is still an open and important question. This study was designed to compare the survival of human tumor cells, cultured in vitro, and exposed to continuous or pulsed irradiation where the pulse frequency was varied. ⋯ This study provides some evidence to support the suggestion that a 10-min pulse, repeated every 1 to 2 h, would be functionally equivalent to a continuous low dose rate irradiation, at least in terms of early responding endpoints. Longer intervals between pulses might result in loss of equivalence in some cases.
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Int. J. Radiat. Oncol. Biol. Phys. · Jan 1997
A retrospective quality of life analysis using the Lung Cancer Symptom Scale in patients treated with palliative radiotherapy for advanced nonsmall cell lung cancer.
To measure symptom palliation in patients treated with radiation therapy for advanced nonsmall cell lung cancer (NSCLC). ⋯ These results suggest symptomatic benefit from radiotherapy even in those NSCLC patients with advanced disease and a limited life expectancy. Treatment should be given to patients whose symptoms are most amenable to palliation. A site-specific quality of life instrument such as the LCSS should be included within any future clinical trial of NSCLC management so that symptom control may be scored as a treatment outcome in addition to disease-free survival.
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Int. J. Radiat. Oncol. Biol. Phys. · Jan 1997
A numerical simulation of organ motion and daily setup uncertainties: implications for radiation therapy.
In radiotherapy planning, the clinical target volume (CTV) is typically enlarged to create a planning target volume (PTV) that accounts for uncertainties due to internal organ and patient motion as well as setup error. Margin size clearly determines the volume of normal tissue irradiated, yet in practice it is often given a set value in accordance with a clinical precedent from which variations are rare. The (CTV/PTV) formalism does not account for critical structure dose. We present a numerical simulation to assess (CTV) coverage and critical organ dose as a function of treatment margins in the presence of organ motion and physical setup errors. An application of the model to the treatment of prostate cancer is presented, but the method is applicable to any site where normal tissue tolerance is a dose-limiting factor. ⋯ Monte Carlo-based treatment simulation is an effective means of assessing the impact of organ motion and daily setup error on dose delivery via external beam radiation therapy. Probability of Prescription Dose (PoPD) isosurfaces are a useful tool for the determination of nonuniform beam margins that reduce dose delivered to critical organs while preserving CTV dose coverage. Nonuniform fluence profiles can further alter critical organ dose with potential therapeutic benefits. Clinical consequences of this latter approach can only be assessed via clinical trials.