International journal of radiation oncology, biology, physics
-
Int. J. Radiat. Oncol. Biol. Phys. · Mar 2005
Use of deformed intensity distributions for on-line modification of image-guided IMRT to account for interfractional anatomic changes.
Recent imaging studies have demonstrated that there can be significant changes in anatomy from day to day and over the course of radiotherapy as a result of daily positioning uncertainties and physiologic and clinical factors. There are a number of strategies to minimize such changes, reduce their impact, or correct for them. Measures to date have included improved immobilization of external and internal anatomy or adjustment of positions based on portal or ultrasound images. Perhaps the most accurate way is to use CT image-guided radiotherapy, for which the possibilities range from simple correction of setup based on daily CT images to on-line near real-time intensity modulated radiotherapy (IMRT) replanning. In addition, there are numerous intermediate possibilities. In this paper, we report the development of one such intermediate method that takes into account anatomic changes by deforming the intensity distributions of each beam based on deformations of anatomy as seen in the beam's-eye-view. ⋯ Our preliminary results encourage us to believe that deforming intensities taking into account deformation in the anatomy may be a rapid way to produce new treatment plans on-line in near real-time based on daily CT images. The methods we have developed need to be applied to a group of patients for both prostate and head-and-neck cases to confirm the validity of our approach.
-
Int. J. Radiat. Oncol. Biol. Phys. · Mar 2005
Randomized Controlled Trial Clinical TrialWhat pretreatment prostate-specific antigen level warrants long-term androgen deprivation?
Several large randomized prospective studies have demonstrated a survival benefit with the addition of long-term androgen deprivation to definitive radiotherapy for patients with Gleason score 8-10 or T3-T4 prostate cancer. However, these studies were performed before the routine use of prostate-specific antigen (PSA) measurement. The purpose of this study was to determine what pretreatment (initial) PSA (iPSA) level, if any, warrants the addition of long-term androgen deprivation in the PSA era. ⋯ Recursive partitioning techniques defined an iPSA cutpoint of 30 ng/mL for delineating intermediate vs. high risk. Patients with a PSA level >30 ng/mL in the absence of Gleason score >7 or T3 disease do poorly when treated with radiotherapy alone and should be considered for long-term androgen deprivation or other aggressive systemic therapy.
-
Int. J. Radiat. Oncol. Biol. Phys. · Mar 2005
Dosimetric advantages of IMRT simultaneous integrated boost for high-risk prostate cancer.
A sequential two-phase process, initial and boost irradiation, is the common practice for the radiotherapy management of high-risk prostate cancer. In this work, we explore the feasibility of using intensity modulated radiation therapy (IMRT) simultaneous integrated boost (SIB), a single-phase process, to simultaneously deliver high dose to the prostate and lower dose to the pelvic nodes. In addition, we introduce the concept of voxel-equivalent dose for the comparison of treatment plans. ⋯ A new IMRT simultaneous integrated boost strategy that irradiates prostate via hypofractionation while irradiating pelvic nodes with the conventional fractionation is proposed for high-risk prostate cancer. Compared to the conventional two-phase treatment, the proposed SIB technique offers potential advantages, including better sparing of critical structures, more efficient delivery, shorter treatment duration, and better biologic effectiveness.
-
Int. J. Radiat. Oncol. Biol. Phys. · Mar 2005
Application of the No Action Level (NAL) protocol to correct for prostate motion based on electronic portal imaging of implanted markers.
To evaluate the efficacy of the No Action Level (NAL) off-line correction protocol in the reduction of systematic prostate displacements as determined from electronic portal images (EPI) using implanted markers. ⋯ The NAL protocol based on marker positions in EPI halved the composite systematic displacements using only three imaged fractions per patient, and thus allowed for a significant reduction of planning margins. Although large rotations of the prostate, and time trends therein, were observed, the net impact on the measured displacements and on the accuracy obtained with NAL was small.
-
Int. J. Radiat. Oncol. Biol. Phys. · Mar 2005
Results of the 2003 Association of Residents in Radiation Oncology (ARRO) surveys of residents and chief residents in the United States.
To document demographic characteristics of current residents, career motivations and aspirations, and training program policies and resources. ⋯ Median program resources and numbers of outliers are documented to allow residents and program directors to assess the relative adequacy of experience in their own programs. Policy-making bodies and individual programs should consider these results when developing interventions to improve educational experiences of residents and to increase retention of radiation oncologists in academic practice.