International journal of radiation oncology, biology, physics
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Int. J. Radiat. Oncol. Biol. Phys. · Mar 2003
Procedures for high precision setup verification and correction of lung cancer patients using CT-simulation and digitally reconstructed radiographs (DRR).
In a recent study, large systematic setup errors were detected in patients with lung cancer when a conventional simulation procedure was used to define and mark the treatment isocenter. In the present study, we describe a procedure to omit the session at a conventional simulator to remove simulation errors entirely. Isocenter definition and verification was performed at a computed tomography (CT) simulator, and digitally reconstructed radiographs (DRRs) were used for setup verification and correction at the treatment unit. ⋯ Because the distributions of treatment setup errors measured against DRRs obtained in our CT simulation were equal to previously obtained distributions measured against simulator films, conventional simulation can be omitted and DRRs are well-suited for setup verification. By adopting our CT simulation procedure, the large systematic simulation setup errors, which remain hidden if a conventional simulation is performed, can be avoided.
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Int. J. Radiat. Oncol. Biol. Phys. · Mar 2003
Intensity-modulated radiation therapy (IMRT) for locally advanced paranasal sinus tumors: incorporating clinical decisions in the optimization process.
Intensity-modulated radiotherapy (IMRT) plans require decisions about priorities and tradeoffs among competing goals. This study evaluates the incorporation of various clinical decisions into the optimization system, using locally advanced paranasal sinus tumors as a model. ⋯ In IMRT plans for paranasal sinus tumors, tradeoff values between OP toxicity and PTV coverage can be compared for different clinical decisions. The information derived can then be used to individualize the parameters within the optimization system. This process of determining clinical tradeoffs associated with different clinical decisions may be a useful tool in other sites.
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Int. J. Radiat. Oncol. Biol. Phys. · Mar 2003
Radiotherapy alone in the treatment of uterine cervix cancer with telecobalt and low-dose-rate brachytherapy: retrospective analysis of results and variables.
This retrospective analysis aims to report results and variables from patients with cervix cancer treated by radiation therapy alone with telecobalt and low-dose-rate brachytherapy (LDRB). ⋯ Results of this series suggest that the use of telecobalt equipment for EBR with doses up to 50 Gy at whole pelvis, prior to brachytherapy, is an acceptable technique for radiation therapy alone in the treatment of cervix cancer, especially in developing countries, including Brazil, where telecobalt machines still prevail.
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Int. J. Radiat. Oncol. Biol. Phys. · Mar 2003
Development of a semi-automatic alignment tool for accelerated localization of the prostate.
Delivering high dose to prostate with external beam radiation has been shown to improve local tumor control. However, it has to be carefully performed to avoid partial target miss and delivering excessive dose to surrounding normal tissues. One way to achieve safe dose escalation is to precisely localize prostate immediately before daily treatment. Therefore, the radiation can be accurately delivered to the target. Once the prostate position is determined with high confidence, planning target volume (PTV) safety margin might be reduced for further reduction of rectal toxicity. A rapid computed tomography (CT)-based online prostate localization method is presented for this purpose. ⋯ Results show that daily CT extent fitting provides a precise correction of prostate position in terms of CoG. Identifying prostate extents on five axial CT slices at the CT console is less time-consuming compared with daily contouring of the prostate on many slices. Taking advantage of the prostate curvature in the longitudinal direction, this method also eliminates the necessity of identifying prostate base and apex. Therefore, it is clinically feasible and should provide an accelerated localization of the prostate immediately before daily treatment.
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Int. J. Radiat. Oncol. Biol. Phys. · Mar 2003
Megavoltage cone-beam computed tomography using a high-efficiency image receptor.
To develop an image receptor capable of forming high-quality megavoltage CT images using modest radiation doses. ⋯ The acquisition of megavoltage CT images with soft-tissue contrast is possible with irradiations as small as 16 cGy.