skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: SU-G-JeP3-03: Effect of Robot Pose On Beam Blocking for Ultrasound Guided SBRT of the Prostate

Abstract

Purpose: Ultrasound presents a fast, volumetric image modality for real-time tracking of abdominal organ motion. How-ever, ultrasound transducer placement during radiation therapy is challenging. Recently, approaches using robotic arms for intra-treatment ultrasound imaging have been proposed. Good and reliable imaging requires placing the transducer close to the PTV. We studied the effect of a seven degrees of freedom robot on the fea-sible beam directions. Methods: For five CyberKnife prostate treatment plans we established viewports for the transducer, i.e., points on the patient surface with a soft tissue view towards the PTV. Choosing a feasible transducer pose and using the kinematic redundancy of the KUKA LBR iiwa robot, we considered three robot poses. Poses 1 to 3 had the elbow point anterior, superior, and inferior, respectively. For each pose and each beam starting point, the pro-jections of robot and PTV were computed. We added a 20 mm margin accounting for organ / beam motion. The number of nodes for which the PTV was partially of fully blocked were established. Moreover, the cumula-tive overlap for each of the poses and the minimum overlap over all poses were computed. Results: The fully and partially blocked nodes ranged from 12% to 20% and 13%more » to 27%, respectively. Typically, pose 3 caused the fewest blocked nodes. The cumulative overlap ranged from 19% to 29%. Taking the minimum overlap, i.e., considering moving the robot’s elbow while maintaining the transducer pose, the cumulative over-lap was reduced to 16% to 18% and was 3% to 6% lower than for the best individual pose. Conclusion: Our results indicate that it is possible to identify feasible ultrasound transducer poses and to use the kinematic redundancy of a 7 DOF robot to minimize the impact of the imaging subsystem on the feasible beam directions for ultrasound guided and motion compensated SBRT. Research partially funded by DFG grants ER 817/1-1 and SCHL 1844/3-1.« less

Authors:
;  [1]; ;  [2];  [3]
  1. Hamburg University of Technology, Hamburg (Germany)
  2. Universitaet zu Luebeck, Luebeck (Germany)
  3. European Cyberknife Center Munich, Munich (Germany)
Publication Date:
OSTI Identifier:
22649410
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:
62 RADIOLOGY AND NUCLEAR MEDICINE; 60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; BEAMS; BIOMEDICAL RADIOGRAPHY; CHANNELING; DEGREES OF FREEDOM; IMAGES; PROSTATE; ROBOTS; TRANSDUCERS

Citation Formats

Gerlach, S, Schlaefer, A, Kuhlemann, I, Ernst, F, and Fuerweger, C. SU-G-JeP3-03: Effect of Robot Pose On Beam Blocking for Ultrasound Guided SBRT of the Prostate. United States: N. p., 2016. Web. doi:10.1118/1.4957068.
Gerlach, S, Schlaefer, A, Kuhlemann, I, Ernst, F, & Fuerweger, C. SU-G-JeP3-03: Effect of Robot Pose On Beam Blocking for Ultrasound Guided SBRT of the Prostate. United States. doi:10.1118/1.4957068.
Gerlach, S, Schlaefer, A, Kuhlemann, I, Ernst, F, and Fuerweger, C. 2016. "SU-G-JeP3-03: Effect of Robot Pose On Beam Blocking for Ultrasound Guided SBRT of the Prostate". United States. doi:10.1118/1.4957068.
@article{osti_22649410,
title = {SU-G-JeP3-03: Effect of Robot Pose On Beam Blocking for Ultrasound Guided SBRT of the Prostate},
author = {Gerlach, S and Schlaefer, A and Kuhlemann, I and Ernst, F and Fuerweger, C},
abstractNote = {Purpose: Ultrasound presents a fast, volumetric image modality for real-time tracking of abdominal organ motion. How-ever, ultrasound transducer placement during radiation therapy is challenging. Recently, approaches using robotic arms for intra-treatment ultrasound imaging have been proposed. Good and reliable imaging requires placing the transducer close to the PTV. We studied the effect of a seven degrees of freedom robot on the fea-sible beam directions. Methods: For five CyberKnife prostate treatment plans we established viewports for the transducer, i.e., points on the patient surface with a soft tissue view towards the PTV. Choosing a feasible transducer pose and using the kinematic redundancy of the KUKA LBR iiwa robot, we considered three robot poses. Poses 1 to 3 had the elbow point anterior, superior, and inferior, respectively. For each pose and each beam starting point, the pro-jections of robot and PTV were computed. We added a 20 mm margin accounting for organ / beam motion. The number of nodes for which the PTV was partially of fully blocked were established. Moreover, the cumula-tive overlap for each of the poses and the minimum overlap over all poses were computed. Results: The fully and partially blocked nodes ranged from 12% to 20% and 13% to 27%, respectively. Typically, pose 3 caused the fewest blocked nodes. The cumulative overlap ranged from 19% to 29%. Taking the minimum overlap, i.e., considering moving the robot’s elbow while maintaining the transducer pose, the cumulative over-lap was reduced to 16% to 18% and was 3% to 6% lower than for the best individual pose. Conclusion: Our results indicate that it is possible to identify feasible ultrasound transducer poses and to use the kinematic redundancy of a 7 DOF robot to minimize the impact of the imaging subsystem on the feasible beam directions for ultrasound guided and motion compensated SBRT. Research partially funded by DFG grants ER 817/1-1 and SCHL 1844/3-1.},
doi = {10.1118/1.4957068},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = 2016,
month = 6
}
  • Purpose: The use of ultrasound (US) imaging in radiotherapy is not widespread, primarily due to the need for skilled operators performing the scans. Automation of probe positioning has the potential to remove this need and minimize operator dependence. We introduce an algorithm for obtaining a US probe position that allows good anatomical structure visualization based on clinical requirements. The first application is on 4D transperineal US images of prostate cancer patients. Methods: The algorithm calculates the probe position and orientation using anatomical information provided by a reference CT scan, always available in radiotherapy workflows. As initial test, we apply themore » algorithm on a CIRS pelvic US phantom to obtain a set of possible probe positions. Subsequently, five of these positions are randomly chosen and used to acquire actual US volumes of the phantom. Visual inspection of these volumes reveal if the whole prostate, and adjacent edges of bladder and rectum are fully visualized, as clinically required. In addition, structure positions on the acquired US volumes are compared to predictions of the algorithm. Results: All acquired volumes fulfill the clinical requirements as specified in the previous section. Preliminary quantitative evaluation was performed on thirty consecutive slices of two volumes, on which the structures are easily recognizable. The mean absolute distances (MAD) between actual anatomical structure positions and positions predicted by the algorithm were calculated. This resulted in MAD of 2.4±0.4 mm for prostate, 3.2±0.9 mm for bladder and 3.3±1.3 mm for rectum. Conclusion: Visual inspection and quantitative evaluation show that the algorithm is able to propose probe positions that fulfill all clinical requirements. The obtained MAD is on average 2.9 mm. However, during evaluation we assumed no errors in structure segmentation and probe positioning. In future steps, accurate estimation of these errors will allow for better evaluation of the achieved accuracy.« less
  • Purpose: To compare two different ultrasound-based verification systems for prostate alignment during daily external beam radiation therapy (EBRT) for localized prostate cancer. Methods and Materials: Prostate displacements were measured prospectively in 40 patients undergoing daily EBRT. Comparison was made between a system based on the cross-modality verification method (CMVM), which uses two different imaging modalities to assess organ motion, and a system based on the intramodality verification method (IMVM), which uses only one imaging modality for such assessment. A total of 217 CMVM and 217 IMVM displacements were collected within a minute of each other. In 10 patients, IMVM displacementsmore » were also compared with those measured by sequential CT scans. Results: Analysis in the paired CMVM and IMVM displacements shows a significant mean difference of 0.9 {+-} 3.3 mm in the lateral and 6.0 {+-} 5.1 mm in the superoinferior directions (p < 0.0001), whereas no significant difference was detected in the anteroposterior direction between the two methods. Comparison of the computed tomography scan and IMVM measured displacements shows no significant difference between the two methods, with mean values of 0.2 {+-} 1.7 mm in the lateral, -0.3 {+-} 1.6 mm in the anteroposterior, and 0.1 {+-} 1.4 mm in the superoinferior directions. Conclusions: A significant systematic difference exists between cross-modality and intramodality methods when assessing prostate alignment during daily EBRT. Because displacements assessed by IMVM are consistent with those assessed by computed tomography scan, a more accurate prostate alignment appears to be obtained when the IMVM method is used.« less
  • Purpose: To report the complication rate and risk factors of transrectally implanted gold markers, used for prostate position verification and correction procedures. Methods and Materials: In 209 consecutive men with localized prostate cancer, four gold markers (1 x 7 mm) were inserted under ultrasound guidance in an outpatient setting, and the toxicity was analyzed. All patients received a questionnaire regarding complications after marker implantation. The complications and risk factors were further evaluated by reviewing the medical charts. Results: Of the 209 men, 13 (6.2%) had a moderate complication, consisting of pain and fever that resolved after treatment with oral medication.more » In 1.9% of the men, minor voiding complaints were observed. Other minor transient complications, defined as hematuria lasting >3 days, hematospermia, and rectal bleeding, occurred in 3.8%, 18.5%, and 9.1% of the patients, respectively. These complications were seen more often in patients with advanced tumor stage, younger age, and shorter duration of hormonal therapy. Conclusion: Transrectal gold marker implantation for high-precision prostate radiotherapy is a safe and well-tolerated procedure.« less
  • Purpose: Targeted magnetic resonance imaging (MRI)/ultrasound fusion prostate biopsy (MRI-Bx) has recently been compared with the standard of care extended sextant ultrasound-guided prostate biopsy (SOC-Bx), with the former associated with an increased rate of detection of clinically significant prostate cancer. The present study sought to determine the influence of MRI-Bx on radiation therapy and androgen deprivation therapy (ADT) recommendations. Methods and Materials: All patients who had received radiation treatment and had undergone SOC-Bx and MRI-Bx at our institution were included. Using the clinical T stage, pretreatment prostate-specific antigen, and Gleason score, patients were categorized into National Comprehensive Cancer Network riskmore » groups and radiation treatment or ADT recommendations assigned. Intensification of the recommended treatment after multiparametric MRI, SOC-Bx, and MRI-Bx was evaluated. Results: From January 2008 to January 2016, 73 patients received radiation therapy at our institution after undergoing a simultaneous SOC-Bx and MRI-Bx (n=47 with previous SOC-Bx). Repeat SOC-Bx and MRI-Bx resulted in frequent upgrading compared with previous SOC-Bx (Gleason score 7, 6.7% vs 44.6%; P<.001; Gleason score 8-10, 2.1% vs 38%; P<.001). MRI-Bx increased the proportion of patients classified as very high risk from 24.7% to 41.1% (P=.027). Compared with SOC-Bx alone, including the MRI-Bx findings resulted in a greater percentage of pathologically positive cores (mean 37% vs 44%). Incorporation of multiparametric MRI and MRI-Bx results increased the recommended use and duration of ADT (duration increased in 28 of 73 patients and ADT was added for 8 of 73 patients). Conclusions: In patients referred for radiation treatment, MRI-Bx resulted in an increase in the percentage of positive cores, Gleason score, and risk grouping. The benefit of treatment intensification in accordance with the MRI-Bx findings is unknown.« less
  • Purpose: Due to limited commissioning time, we previously only released our True beam non-FFF mode for prostate treatment. Clinical demand now pushes us to release the non-FFF mode for SRT/SBRT treatment. When re-planning on True beam previously treated SRT/SBRT cases on iX machine we found the patient specific QA pass rate was worse than iX’s, though the 2Gy/fx prostate Result had been as good. We hypothesize that in TPS the True beam DLG and MLC transmission values, of those measured during commissioning could not yet provide accurate SRS/SBRT dosimetry. Hence this work is to investigate how the TPS DLG andmore » transmission value affects Rapid Arc plans’ dosimetric accuracy. Methods: We increased DLG and transmission value of True beam in TPS such that their percentage differences against the measured matched those of iX’s. We re-calculated 2 SRT, 1 SBRT and 2 prostate plans, performed patient specific QA on these new plans and compared the results to the previous. Results: With DLG and transmission value set respectively 40 and 8% higher than the measured, the patient specific QA pass rate (at 3%/3mm) improved from 95.0 to 97.6% vs previous iX’s 97.8% in the case of SRT. In the case of SBRT, the pass rate improved from 75.2 to 93.9% vs previous iX’s 92.5%. In the case of prostate, the pass rate improved from 99.3 to 100%. The maximum dose difference in plans before and after adjusting DLG and transmission was approximately 1% of the prescription dose among all plans. Conclusion: The impact of adjusting DLG and transmission value on dosimetry might be the same among all Rapid Arc plans regardless hypofractionated or not. The large variation observed in patient specific QA pass rate might be due to the data analysis method in the QA software being more sensitive to hypofractionated plans.« less