International journal of radiation oncology, biology, physics
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Int. J. Radiat. Oncol. Biol. Phys. · Apr 2002
Is uniform target dose possible in IMRT plans in the head and neck?
Various published reports involving intensity-modulated radiotherapy (IMRT) plans developed using automated optimization (inverse planning) have demonstrated highly conformal plans. These reported conformal IMRT plans involve significant target dose inhomogeneity, including both overdosage and underdosage within the target volume. In this study, we demonstrate the development of optimized beamlet IMRT plans that satisfy rigorous dose homogeneity requirements for all target volumes (e.g., +/-5%), while also sparing the parotids and other normal structures. ⋯ Sparing of both parotids in patients receiving bilateral neck radiation can be achieved without compromising strict target dose homogeneity criteria. The geometry of the normal tissue and target anatomy are shown to be the major factor necessary to predict the parotid sparing that will be possible for any particular case.
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Int. J. Radiat. Oncol. Biol. Phys. · Apr 2002
Dose optimization of fractionated external radiation and high-dose-rate intracavitary brachytherapy for FIGO stage IB uterine cervical carcinoma.
To determine the optimal dose combination scheme of external beam radiotherapy (EBRT) and high-dose-rate (HDR) intracavitary radiation (ICR) for maximizing tumor control while conferring an acceptable late complication rate in the treatment of Stage IB uterine cervical cancer. ⋯ In treating Stage IB carcinoma of the uterine cervix with HDR-ICR, using fractions of 3 Gy, it is crucial to keep the point A BED at
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Int. J. Radiat. Oncol. Biol. Phys. · Apr 2002
Dose-effect relationship for cataract induction after single-dose total body irradiation and bone marrow transplantation for acute leukemia.
To determine a dose-effect relationship for cataract induction, the tissue-specific parameter, alpha/beta, and the rate of repair of sublethal damage, mu value, in the linear-quadratic formula have to be known. To obtain these parameters for the human eye lens, a large series of patients treated with different doses and dose rates is required. The data of patients with acute leukemia treated with single-dose total body irradiation (STBI) and bone marrow transplantation (BMT) collected by the European Group for Blood and Marrow Transplantation were analyzed. ⋯ The alpha/beta value of 0.75 Gy and mu value of 0.65 h(-1) found for the eye lens are characteristic for late-responding tissues. The incidence of cataract formation can now be quantified, taking into account the values calculated for alpha/beta and mu, TBI dose, and dose rate. Also, the reduction in cataract incidence as a result of lens dose reduction by eye shielding can be estimated.
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Int. J. Radiat. Oncol. Biol. Phys. · Mar 2002
Performance evaluation of an 85-cm-bore X-ray computed tomography scanner designed for radiation oncology and comparison with current diagnostic CT scanners.
The demand for computed tomography (CT) virtual simulation is constantly increasing with the wider adoption of three-dimensional conformal and intensity-modulated radiation therapy. Virtual simulation CT studies are typically acquired on conventional diagnostic scanners equipped with an external patient positioning laser system and specialized planning and visualization software. Virtual simulation technology has matured to a point where conventional simulators may be replaced with CT scanners. However, diagnostic CT scanner gantry bores (typically 65-70 cm) can present an obstacle to the CT simulation process by limiting patient positions, compared to those that can be attained in a conventional simulator. For example, breast cancer patients cannot always be scanned in the treatment position without compromising reproducibility and appropriateness of setup. Extremely large patients or patients requiring special immobilization or large setup devices are often unable to enter the limited-bore gantry. A dedicated 85-cm-bore radiation oncology CT scanner has the potential to eliminate these problems. The scanner should provide diagnostic-quality images at diagnostic-comparable dose levels. The purpose of this study was to independently evaluate the performance of a novel 85-cm-bore CT X-ray scanner designed specifically for radiation oncology and compare it against diagnostic-type, 70-cm-bore scanners that may be used in the same setting. ⋯ The overall imaging performance and mechanical integrity of the 85-cm-bore scanner are comparable to those of conventional diagnostic scanners that may be employed in a radiation oncology setting.
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Int. J. Radiat. Oncol. Biol. Phys. · Mar 2002
Locoregional failure of postmastectomy patients with 1-3 positive axillary lymph nodes without adjuvant radiotherapy.
To analyze the incidence and risk factors for locoregional recurrence (LRR) in patients with breast cancer who had T1 or T2 primary tumor and 1-3 histologically involved axillary lymph nodes treated with modified radical mastectomy without adjuvant radiotherapy (RT). ⋯ LRR after mastectomy is not only a substantial clinical problem, but has a significant impact on the outcome of patients with T1 or T2 primary tumor and 1-3 positive axillary nodes. Patients with risk factors for LRR may need adjuvant RT. Randomized trials are warranted to determine the potential benefit of postmastectomy RT on the survival of patients with a T1 or T2 primary tumor and 1-3 positive nodes.