International journal of radiation oncology, biology, physics
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Int. J. Radiat. Oncol. Biol. Phys. · Jun 2000
Dosimetric evaluation of abutted fields using asymmetric collimators for treatment of head and neck.
The objective of this study was to reevaluate the dose nonuniformity of abutted fields defined using asymmetric collimators and one isocenter for treatment of the head and neck region. ⋯ Imperfect abutment of split fields due to digital display tolerance (+/-1 mm) of asymmetric collimator can cause an underdose or overdose of 15% of the delivered dose.
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Int. J. Radiat. Oncol. Biol. Phys. · Jun 2000
Defining the appropriate radiation dose for pretreatment PSA < or = 10 ng/mL prostate cancer.
To investigate whether a dose response exists for biochemical no evidence of disease (bNED) control in prostate cancer patients with pretreatment prostate-specific antigen (PSA) < or = 10 ng/mL and to identify the patient subgroups affected. ⋯ The poor prognosis subset of PSA < or =10 ng/mL prostate cancer patients benefit from dose escalation. A dose response is not demonstrated for prostate cancer patients with pretreatment PSA < or =10 ng/mL and other favorable features.
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To evaluate prognostic factors for medulloblastoma. ⋯ Stage M0 + M1 was the most powerful favorable prognostic factor. In Saudi Arabia more patients present with advanced disseminated disease, 41% M2 + M3, than in the West, and this impacts adversely on overall survival. Total resection and standard radiation treatment were not sensitive prognostic factors in a treatment environment in which 78% of patients underwent at least 90% tumor resection and 60% received standard radiation treatment. In order to improve the proportion of patients able to complete radiation treatment, consideration should be given to limiting resection when the attainment of total resection is likely to be morbid, and to delaying rather than omitting radiation treatment in the patient severely compromised postoperatively.
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Int. J. Radiat. Oncol. Biol. Phys. · Jun 2000
Setup error in radiotherapy: on-line correction using electronic kilovoltage and megavoltage radiographs.
We hypothesize that the difference in image quality between the traditional kilovoltage (kV) prescription radiographs and megavoltage (MV) treatment radiographs is a major factor hindering our ability to accurately measure, thus correct, setup error in radiation therapy. The objective of this work is to study the accuracy of on-line correction of setup errors achievable using either kV- or MV-localization (i.e., open-field) radiographs. ⋯ In our anatomic template alignment study, interobserver variability was smaller using kV images than MV images. Intraobserver variability was smaller for alignments on kV images