International journal of radiation oncology, biology, physics
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Int. J. Radiat. Oncol. Biol. Phys. · Oct 1999
Dose, volume, and function relationships in parotid salivary glands following conformal and intensity-modulated irradiation of head and neck cancer.
To determine the relationships between the three-dimensional dose distributions in parotid glands and their saliva production, and to find the doses and irradiated volumes that permit preservation of the salivary flow following irradiation (RT). ⋯ Dose/volume/function relationships in the parotid glands are characterized by dose and volume thresholds, steep dose/response relationships when the thresholds are reached, and a maximal volume dependence parameter in the NTCP model. A parotid gland mean dose of < or =26 Gy should be a planning goal if substantial sparing of the gland function is desired.
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Int. J. Radiat. Oncol. Biol. Phys. · Oct 1999
Effect of post-implant edema on the rectal dose in prostate brachytherapy.
To characterize the effect of prostate edema on the determination of the dose delivered to the rectum following the implantation of 125I or 103Pd seeds into the prostate. ⋯ The rectal surface dose determined by analysis of a post-implant CT scan of an 125I or 103Pd prostate seed implant depends upon the timing of the CT scan. The dose indicated by the CT scan on day 30 is typically at least 50% greater than that indicated by the CT scan on day 0. Because of this difference, it is important to keep the timing of the post-implant CT in mind when specifying dose thresholds for rectal morbidity.
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Int. J. Radiat. Oncol. Biol. Phys. · Sep 1999
Comparative StudyIsotope selection for patients undergoing prostate brachytherapy.
Ultrasound-guided transperineal interstitial permanent prostate brachytherapy (TIPPB) is generally performed with either 103Pd or 125I. The use of 125I for low Gleason score tumors and 103Pd for higher Gleason scores has been suggested based on isotope dose rate and cell doubling time observed in in vitro studies. While many centers follow these isotope selection criteria, other centers have elected to use only a single isotope, regardless of Gleason score. No clinical data have been published comparing these isotopes. This study was undertaken to compare outcomes between 125I and 103Pd in a matched pair analysis for patients undergoing prostate brachytherapy. ⋯ This matched pair analysis failed to demonstrate a difference for 125I and 103Pd in PSA-RFS for patients undergoing TIPPB. In addition, there were no observed advantages for either 125I or 103Pd in either the low or high Gleason score groups. This data indicates that the role of isotope selection for patients undergoing TIPPB requires further clarification.
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Int. J. Radiat. Oncol. Biol. Phys. · Sep 1999
The effect of patient position and treatment technique in conformal treatment of prostate cancer.
The relative value of prone versus supine positioning and axial versus nonaxial beam arrangements in the treatment of prostate cancer remains controversial. Two critical issues in comparing techniques are: 1) dose to critical normal tissues, and 2) prostate stabilization. ⋯ Prone flat positioning was advantageous over other positions and beam arrangements in rectal sparing. This study suggests that patient position is a more critical a factor in conformal therapy than beam arrangement, and may improve the safety of dose escalation.
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Int. J. Radiat. Oncol. Biol. Phys. · Sep 1999
Comparative StudyComparison of intensity-modulated tomotherapy with stereotactically guided conformal radiotherapy for brain tumors.
Intensity-modulated radiotherapy (IMRT) offers the potential to more closely conform dose distributions to the target, and spare organs at risk (OAR). Its clinical value is still being defined. The present study aims to compare IMRT with stereotactically guided conformal radiotherapy (SCRT) for patients with medium size convex-shaped brain tumors. ⋯ The Peacock method provided improved PTV coverage, albeit small, in this group of convex tumors. Although the OAR doses were higher using the Peacock plans, all doses remained within the clinically defined threshold and were clinically acceptable. Further improvements may be expected using other methods of IMRT planning that do not limit the treatment delivery to transaxial arcs. Each IMRT system needs to be individually assessed as the paradigm utilized may provide different outcomes.