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. · Apr 2004
A treatment planning comparison of intensity modulated photon and proton therapy for paraspinal sarcomas.
A comparative treatment planning study has been undertaken between intensity modulated (IM) photon therapy and IM proton therapy (IMPT) in paraspinal sarcomas, so as to assess the potential benefits and limitations of these treatment modalities. In the case of IM proton therapy, plans were compared also for two different sizes of the pencil beam. Finally, a 10% and 20% dose escalation with IM protons was planned, and the consequential organ at risk (OAR) irradiation was evaluated. ⋯ These results suggest that the use of IM photon therapy, when compared to IM protons, can result in similar levels of tumor conformation. IM proton therapy, however, reduces the OAR integral dose substantially, compared to IM photon radiation therapy. As a result, tumor dose escalation was always possible with IM proton planning, within the maximal OAR dose constraints. In IM proton planning, reducing the size of the proton pencil beam (using the "mini-beam") improved the dose homogeneity, but it did not have a significant effect on the dose conformity.
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Int. J. Radiat. Oncol. Biol. Phys. · Mar 2004
Multicenter StudyCentralized radiation oncologic review of cross-sectional imaging of Hodgkin's disease leads to significant changes in required involved field-results of a quality assurance program of the German Hodgkin Study Group.
To guarantee the treatment quality of involved-field radiotherapy (IF-RT) of patients in the Hodgkin's disease (HD)10 and HD11 trials of the German Hodgkin Study Group, with 460 participating study centers, a quality assurance program was conducted. It was based on a central prospective radiation oncologic review of all patients' entire diagnostic imaging and clinical findings. An individual RT prescription was provided for every study patient. The purpose of the present investigation was to assess the feasibility of such a procedure and its impact on the final definition of disease extension and patient treatment. ⋯ A central prospective review of patient data and consecutive prescription of individual RT treatment volume is feasible within large multicenter trials for HD. Such a procedure has a significant impact on the correctness of stage definition, allocation to treatment groups, and extent of the IF treatment volume.