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Title: SU-F-J-203: Retrospective Assessment of Delivered Proton Dose in Prostate Cancer Patients Based On Daily In-Room CT Imaging

Abstract

Purpose: Retrospective calculation of the delivered proton dose in prostate cancer patients based on a unique dataset of daily CT images. Methods: Inter-fractional motion in prostate cancer patients treated at our proton facility is counteracted by water-filled endorectal ballon and bladder filling protocol. Typical plans (XiO, Elekta Instruments AB, Stockholm) for 74 Gy(RBE) sequential boost treatment in 37 fractions include two series of opposing lateral double-scattered proton beams covering the respective iCTV. Stability of fiducial markers and anatomy were checked in 12 patients by daily scheduled in-room control CT (cCT) after immobilization and positioning according to bony anatomy utilizing orthogonal X-ray. In RayStation 4.6 (RaySearch Laboritories AB, Stockholm), all cCTs are delineated retrospectively and the treatment plans were recalculated on the planning CT and the registered cCTs. All fraction doses were accumulated on the planning CT after deformable registration. Parameters of delivered dose to iCTV (D98%>95%, D2%<107%), bladder (V75Gy<15%, V70Gy<25%, V65Gy<30%), rectum (V70Gy<10%, V50Gy<40%) and femoral heads (V50Gy<5%) are compared to those in the treatment plan. Intra-therapy variation is represented in DVH bands. Results: No alarming differences were observed between planned and retrospectively accumulated dose: iCTV constraints were met, except for one patient (D98%=94.6% in non-boosted iCTV). Considered bladder andmore » femoral head values were below the limits. Rectum V70Gy was slightly exceeded (<11.3%) in two patients. First intra-therapy variability analysis in 4 patients showed no timedependent parameter drift, revealed strongest variability for bladder dose. In some fractions, iCTV coverage (D98%) and rectum V70Gy was missed. Conclusion: Double scattered proton plans are accurately delivered to prostate cancer patients due to fractionation effects and the applied precise positioning and immobilization protocols. As a result of rare interventions after daily 3D imaging of the first 12 patients, in-room CT frequency for prostate cancer patients was reduced. The presented study supports this decision. The authors acknowledge the German Federal Ministry for Education and Research for funding the High Precision Radiotherapy Group at the OncoRay - National Center for Radiation Research in Oncology (BMBF- 03Z1N51).« less

Authors:
;  [1]; ; ;  [2];  [1];  [3]; ;  [1];  [3];  [3];  [4]
  1. OncoRay - National Center for Radiation Research in Oncology, Medical Faculty and University Hospital Carl Gustav Carus, Technische Universitaet Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany)
  2. Department of Radiation Oncology, University Hospital Carl Gustav Carus, Techenische Universitaet Dresden (Germany)
  3. (Germany)
  4. (DKTK), Dresden, Germany and German Cancer Research Center (DKFZ), Heidelberg (Germany)
Publication Date:
OSTI Identifier:
22642231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; ACCURACY; ANATOMY; BIOMEDICAL RADIOGRAPHY; BLADDER; COMPUTERIZED TOMOGRAPHY; DATASETS; FIDUCIAL MARKERS; HEAD; IMAGE PROCESSING; LIMITING VALUES; NEOPLASMS; PATIENTS; PLANNING; PROSTATE; PROTON BEAMS; RADIATION DOSES; RADIOTHERAPY; RECTUM; TIME DEPENDENCE

Citation Formats

Stuetzer, K, Paessler, T, Valentini, C, Thiele, J, Hoelscher, T, Exner, F, now with: University of Wuerzburg, Department of Radiation Oncology, Wuerzburg, Krause, M, Richter, C, Department of Radiation Oncology, University Hospital Carl Gustav Carus, Techenische Universitaet Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiooncology, Dresden, and German Cancer Consortium. SU-F-J-203: Retrospective Assessment of Delivered Proton Dose in Prostate Cancer Patients Based On Daily In-Room CT Imaging. United States: N. p., 2016. Web. doi:10.1118/1.4956111.
Stuetzer, K, Paessler, T, Valentini, C, Thiele, J, Hoelscher, T, Exner, F, now with: University of Wuerzburg, Department of Radiation Oncology, Wuerzburg, Krause, M, Richter, C, Department of Radiation Oncology, University Hospital Carl Gustav Carus, Techenische Universitaet Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiooncology, Dresden, & German Cancer Consortium. SU-F-J-203: Retrospective Assessment of Delivered Proton Dose in Prostate Cancer Patients Based On Daily In-Room CT Imaging. United States. doi:10.1118/1.4956111.
Stuetzer, K, Paessler, T, Valentini, C, Thiele, J, Hoelscher, T, Exner, F, now with: University of Wuerzburg, Department of Radiation Oncology, Wuerzburg, Krause, M, Richter, C, Department of Radiation Oncology, University Hospital Carl Gustav Carus, Techenische Universitaet Dresden, Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiooncology, Dresden, and German Cancer Consortium. 2016. "SU-F-J-203: Retrospective Assessment of Delivered Proton Dose in Prostate Cancer Patients Based On Daily In-Room CT Imaging". United States. doi:10.1118/1.4956111.
@article{osti_22642231,
title = {SU-F-J-203: Retrospective Assessment of Delivered Proton Dose in Prostate Cancer Patients Based On Daily In-Room CT Imaging},
author = {Stuetzer, K and Paessler, T and Valentini, C and Thiele, J and Hoelscher, T and Exner, F and now with: University of Wuerzburg, Department of Radiation Oncology, Wuerzburg and Krause, M and Richter, C and Department of Radiation Oncology, University Hospital Carl Gustav Carus, Techenische Universitaet Dresden and Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiooncology, Dresden and German Cancer Consortium},
abstractNote = {Purpose: Retrospective calculation of the delivered proton dose in prostate cancer patients based on a unique dataset of daily CT images. Methods: Inter-fractional motion in prostate cancer patients treated at our proton facility is counteracted by water-filled endorectal ballon and bladder filling protocol. Typical plans (XiO, Elekta Instruments AB, Stockholm) for 74 Gy(RBE) sequential boost treatment in 37 fractions include two series of opposing lateral double-scattered proton beams covering the respective iCTV. Stability of fiducial markers and anatomy were checked in 12 patients by daily scheduled in-room control CT (cCT) after immobilization and positioning according to bony anatomy utilizing orthogonal X-ray. In RayStation 4.6 (RaySearch Laboritories AB, Stockholm), all cCTs are delineated retrospectively and the treatment plans were recalculated on the planning CT and the registered cCTs. All fraction doses were accumulated on the planning CT after deformable registration. Parameters of delivered dose to iCTV (D98%>95%, D2%<107%), bladder (V75Gy<15%, V70Gy<25%, V65Gy<30%), rectum (V70Gy<10%, V50Gy<40%) and femoral heads (V50Gy<5%) are compared to those in the treatment plan. Intra-therapy variation is represented in DVH bands. Results: No alarming differences were observed between planned and retrospectively accumulated dose: iCTV constraints were met, except for one patient (D98%=94.6% in non-boosted iCTV). Considered bladder and femoral head values were below the limits. Rectum V70Gy was slightly exceeded (<11.3%) in two patients. First intra-therapy variability analysis in 4 patients showed no timedependent parameter drift, revealed strongest variability for bladder dose. In some fractions, iCTV coverage (D98%) and rectum V70Gy was missed. Conclusion: Double scattered proton plans are accurately delivered to prostate cancer patients due to fractionation effects and the applied precise positioning and immobilization protocols. As a result of rare interventions after daily 3D imaging of the first 12 patients, in-room CT frequency for prostate cancer patients was reduced. The presented study supports this decision. The authors acknowledge the German Federal Ministry for Education and Research for funding the High Precision Radiotherapy Group at the OncoRay - National Center for Radiation Research in Oncology (BMBF- 03Z1N51).},
doi = {10.1118/1.4956111},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = 2016,
month = 6
}
  • Introduction: We have assessed the planning target volume (PTV) margins required for adequate treatment of the prostate in the absence of daily localization imaging based on the statistical analysis of a large data set obtained from 5 years of use of a two-dimensional ultrasound pretreatment localization device. Methods and Materials: Data from 387 prostate patients were analyzed retrospectively. Every patient in the study received daily pretreatment localization resulting in a total of 10,327 localizations, each comprising an isocenter displacement in three directions: anteroposterior, right-left lateral, and superior-inferior. The mean displacement for each direction for each patient was computed from dailymore » treatment records, and a mean of the means was used in the analysis. Results: The mean displacements required to shift the target to the required position were 6.1 mm posterior (4.4 mm SD), 2.1 mm superior (4.5 mm SD), and 0.5 mm right (3.6 mm SD). The 6.1-mm shift posterior is indicative of a systematic uncertainty. Differences in planning conditions between the computed tomography simulation and the treatment room may account for this discrepancy. Conclusion: Our study has revealed systematic intertreatment uncertainties that would have required a nonuniform PTV margin ranging in dimensions between 2.7 mm anterior, 14.9 mm posterior, 7.7 mm right, 6.7 mm left, 11 mm superior, and 7 mm inferior to encompass the prostate for 95% of our sample if the ultrasound localization system were not used. In the absence of systematic uncertainties, a uniform PTV margin of 9 mm would suffice.« less
  • Purpose: The aim of this work was to study the variations in delivered doses to the prostate, rectum, and bladder during a full course of image-guided external beam radiotherapy. Methods and Materials: Ten patients with localized prostate cancer were treated with helical tomotherapy to 78 Gy at 2 Gy per fraction in 39 fractions. Daily target localization was performed using intraprostatic fiducials and daily megavoltage pelvic computed tomography (CT) scans, resulting in a total of 390 CT scans. The prostate, rectum, and bladder were manually contoured on each CT by a single physician. Daily dosimetric analysis was performed with dosemore » recalculation. The study endpoints were D95 (dose to 95% of the prostate), rV2 (absolute rectal volume receiving 2 Gy), and bV2 (absolute bladder volume receiving 2 Gy). Results: For the entire cohort, the average D95 ({+-}SD) was 2.02 {+-} 0.04 Gy (range, 1.79-2.20 Gy). The average rV2 ({+-}SD) was 7.0 {+-} 8.1 cc (range, 0.1-67.3 cc). The average bV2 ({+-}SD) was 8.7 {+-} 6.8 cc (range, 0.3-36.8 cc). Unlike doses for the prostate, there was significant daily variation in rectal and bladder doses, mostly because of variations in volume and shape of these organs. Conclusion: Large variations in delivered doses to the rectum and bladder can be documented with daily megavoltage CT scans. Image guidance for the targeting of the prostate, even with intraprostatic fiducials, does not take into account the variation in actual rectal and bladder doses. The clinical impact of techniques that take into account such dosimetric parameters in daily patient set-ups should be investigated.« less
  • Purpose: To compare the accuracy of imaging modalities, immobilization, localization, and positioning techniques in patients with prostate cancer. Methods and Materials: Thirty-five patients with prostate cancer had gold marker seeds implanted transrectally and were treated with fractionated radiotherapy. Twenty of the 35 patients had limited immobilization; the remaining had a vacuum-based immobilization. Patient positioning consisted of alignment with lasers to skin marks, ultrasound or kilovoltage X-ray imaging, optical guidance using infrared reflectors, and megavoltage electronic portal imaging (EPI). The variance of each positioning technique was compared to the patient position determined from the pretreatment EPI. Results: With limited immobilization, themore » average difference between the skin marks' laser position and EPI pretreatment position is 9.1 {+-} 5.3 mm, the average difference between the skin marks' infrared position and EPI pretreatment position is 11.8 {+-} 7.2 mm, the average difference between the ultrasound position and EPI pretreatment position is 7.0 {+-} 4.6 mm, the average difference between kV imaging and EPI pretreatment position is 3.5 {+-} 3.1 mm, and the average intrafraction movement during treatment is 3.4 {+-} 2.7 mm. For the patients with the vacuum-style immobilization, the average difference between the skin marks' laser position and EPI pretreatment position is 10.7 {+-} 4.6 mm, the average difference between kV imaging and EPI pretreatment position is 1.9 {+-} 1.5 mm, and the average intrafraction movement during treatment is 2.1 {+-} 1.5 mm. Conclusions: Compared with use of skin marks, ultrasound imaging for positioning provides an increased degree of agreement to EPI-based positioning, though not as favorable as kV imaging fiducial seeds. Intrafraction movement during treatment decreases with improved immobilization.« less
  • Purpose: To perform a comparison of the daily measured dose at depth in tissue with the predicted dose values from treatment plans for 29 prostate cancer patients involved in a clinical trial. Methods and Materials: Patients from three clinical sites were implanted with one or two dosimeters in or near the prostatic capsule. The implantable device, known as the DVS, is based on a metal-oxide-semiconductor field effect transistor (MOSFET) detector. A portable telemetric readout system couples to the dosimeter antenna (visible on kilovoltage, computed tomography, and ultrasonography) for data transfer. The predicted dose values were determined by the location ofmore » the MOSFET on the treatment planning computed tomography scan. Serial computed tomography images were taken every 2 weeks to evaluate any migration of the device. The clinical protocol did not permit alteration of the treatment parameters using the dosimeter readings. For some patients, one of several image-guided radiotherapy (RT) modalities was used for target localization. Results: The evaluation of dose discrepancy showed that in many patients the standard deviation exceeded the previous values obtained for the dosimeter in a phantom. In some patients, the cumulative dose disagreed with the planned dose by {>=}5%. The data presented suggest that an implantable dosimeter can help identify dose discrepancies (random or systematic) for patients treated with external beam RT and could be used as a daily treatment verification tool for image-guided RT and adaptive RT. Conclusion: The results of our study have shown that knowledge of the dose delivered per fraction can potentially prevent over- or under-dosage to the treatment area and increase the accuracy of RT. The implantable dosimeter could also be used as a localizer for image-guided RT.« less
  • Purpose: To determine whether image guidance can improve the dose delivered to target organs and organs at risk (OARs) for prostate cancer patients treated with intensity-modulated radiotherapy (IMRT). Methods and Materials: Eight prostate cancer patients were treated with IMRT to 76 Gy at 2 Gy per fraction. Daily target localization was performed via alignment of three intraprostatic fiducials and weekly kV-cone beam computed tomography (CBCT) scans. The prostate and OARs were manually contoured on each CBCT by a single physician. Daily patient setup shifts were obtained by comparing alignment of skin tattoos with the treatment position based on fiducials. Treatmentmore » fields were retrospectively applied to CBCT scans. The dose distributions were calculated using actual treatment plans (an 8-mm PTV margin everywhere except for 6-mm posteriorly) with and without image guidance shifts. Furthermore, the feasibility of margin reduction was evaluated by reducing planning margins to 4 mm everywhere except for 3 mm posteriorly. Results: For the eight treatment plans on the 56 CBCT scans, the average doses to 98% of the prostate (D98) were 102% (range, 99-104%) and 99% (range, 45-104%) with and without image guidance, respectively. Using margin reduction, the average D98s were 100% (range, 84-104%) and 92% (range, 40-104%) with and without image guidance, respectively. Conclusions: Currently, margins used in IMRT plans are adequate to deliver a dose to the prostate with conventional patient positioning using skin tattoos or bony anatomy. The use of image guidance may facilitate significant reduction of planning margins. Future studies to assess the efficacy of decreasing margins and improvement of treatment-related toxicities are warranted.« less