International journal of radiation oncology, biology, physics
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Int. J. Radiat. Oncol. Biol. Phys. · Apr 2004
Dose-volume conundrum for response of prostate cancer to brachytherapy: summary dosimetric measures and their relationship to tumor control probability.
Although it is known that brachytherapy dose distributions are highly heterogeneous, the effect of particular dose distribution patterns on tumor control probability (TCP) is unknown. It is unlikely that clinical results will throw light on the question in the near future, given the long follow-up and detailed dosimetry required for each patient. We used detailed dose distribution data from 50 patients combined with radiobiologic parameters consistent with what is known about TCP curves for prostate cancer to study the changes in TCP that accompany gross dosimetric measures and particular dosing irregularities (e.g., moderate underdosing of large volumes vs. extreme underdosing of small volumes). ⋯ The work described here was an hypothesis-generating study. Our results showed that even if the V100 and D90 are nearly identical for 2 patients, there can be (and frequently are) significant differences in the dose distributions in the subvolumes of the prostate. Under simulated dose-response conditions (i.e., with variations in the dose distribution), the D90 and minimal dose significantly affected the TCP but the V100 and the volumes moderately or severely underdosed did not. In general, one must consider the totality of the dose distribution to evaluate the dosimetric quality of a low-dose-rate prostate implant. TCP is not a monotonic function of extreme or moderate underdosing. In some instances, extreme underdosing of relatively small volumes may result in a greater TCP than moderate underdosing of relatively large volumes and vice versa.
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Int. J. Radiat. Oncol. Biol. Phys. · Apr 2004
Proton and hyperpolarized helium magnetic resonance imaging of radiation-induced lung injury in rats.
To assess the usefulness of hyperpolarized helium (3He) MRI, including apparent diffusion coefficient measurements, in the detection and evaluation of radiation-induced lung injury in rats. ⋯ This is the first study to show that hyperpolarized 3He MRI can detect radiation-induced lung injury noninvasively. Reduced hyperpolarized 3He ADC values postradiation likely reflect reduced alveolar volumes associated with fibrosis of the interstitium. Future studies at earlier time points may determine whether this noninvasive imaging technique can detect lung damage before clinical symptoms. Development of this new approach of magnetic resonance lung imaging in the rat model of radiation-induced lung injury will increase the ability to develop appropriate algorithms and more accurate models of the normal tissue complication probability.
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Int. J. Radiat. Oncol. Biol. Phys. · Mar 2004
Integration of functional brain information into stereotactic irradiation treatment planning using magnetoencephalography and magnetic resonance axonography.
To minimize the risk of neurologic deficit after stereotactic irradiation, functional brain information was integrated into treatment planning. ⋯ Integration of magnetoencephalography and magnetic resonance axonography in treatment planning has the potential to reduce the risk of radiation-induced functional dysfunction without deterioration of the dose distribution in the target volume.