Robotic ultrasound-guided SBRT of the prostate: feasibility with respect to plan quality
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Advances in radiation therapy delivery systems have enabled motion compensated SBRT of the prostate. A remaining challenge is the integration of fast, non-ionizing volumetric imaging. Recently, robotic ultrasound has been proposed as an intra-fraction image modality. We study the impact of integrating a light-weight robotic arm carrying an ultrasound probe with the CyberKnife system. Particularly, we analyze the effect of different robot poses on the plan quality.
A method to detect the collision of beams with the robot or the transducer was developed and integrated into our treatment planning system. A safety margin accounts for beam motion and uncertainties. Using strict dose bounds and the objective to maximize target coverage, we generated a total of 7650 treatment plans for five different prostate cases. For each case, ten different poses of the ultrasound robot and transducer were considered. The effect of different sets of beam source positions and different motion margins ranging from 5 to 50 mm was analyzed.
Compared to reference plans without the ultrasound robot, the coverage typically drops for all poses. Depending on the patient, the robot pose, and the motion margin, the reduction in coverage may be up to 50 % points. However, for all patient cases, there exist poses for which the loss in coverage was below 1 % point for motion margins of up to 20 mm. In general, there is a positive correlation between the number of treatment beams and the coverage.
While the blocking of beam directions has a negative effect on the plan quality, the results indicate that a careful choice of the ultrasound robot’s pose and a large solid angle covered by beam starting positions can offset this effect. Identifying robot poses that yield acceptable plan quality and allow for intra-fraction ultrasound image guidance, therefore, appears feasible.
KeywordsSBRT Image-guided radiation therapy CyberKnife Treatment planning Ultrasound Robotics
- 1.King CR, Freeman D, Kaplan I, Fuller D, Bolzicco G, Collins S, Meier R, Wang J, Kupelian P, Steinberg M, Katz A (2013) Stereotactic body radiotherapy for localized prostate cancer: pooled analysis from a multi-institutional consortium of prospective phase II trials. Radiother Oncol 109(2):217–221CrossRefPubMedGoogle Scholar
- 8.Depuydt T, Poels K, Verellen D, Engels B, Collen C, Haverbeke C, Gevaert T, Buls N, Van Gompel G, Reynders T, Duchateau M, Tournel K, Boussaer M, Steenbeke F, Vandenbroucke F, De Ridder M (2013) Initial assessment of tumor tracking with a gimbaled linac system in clinical circumstances: a patient simulation study. Radiother Oncol 106(2):236–240CrossRefPubMedGoogle Scholar
- 10.Kupelian P, Willoughby T, Mahadevan A, Djemil T, Weinstein G, Jani S, Enke C, Solberg T, Flores N, Liu D, Beyer D, Levine L (2007) Multi-institutional clinical experience with the Calypso system in localization and continuous, real-time monitoring of the prostate gland during external radiotherapy. Int J Radiat Oncol Biol Phys 67(4):1088–1098CrossRefPubMedGoogle Scholar
- 12.Keall PJ, Barton M, Crozier S (2014) On behalf of the Australian MRI-Linac Program, including contributors from the Ingham Institute, Illawarra Cancer Care Centre, Liverpool Hospital, Stanford University, Universities of Newcastle, Queensland, Sydney, Western Sydney, and Wollongong. The Australian magnetic resonance imaging-linac program. Semin Radiat Oncol 24(3):203–206Google Scholar
- 14.Bruder R, Ernst F, Schlaefer A, Schweikard A (2009) TH-C-304A-07: real-time tracking of the pulmonary veins in 3D ultrasound of the beating heart. 51st Annual meeting of the AAPM. Med Phys, vol 36, p 2804Google Scholar
- 15.Bruder R, Ernst F, Schlaefer A, Schweikard A (2011) A framework for real-time target tracking in radiosurgery using three-dimensional ultrasound. In: Proceedings of the 25th international congress and exhibition on computer assisted radiology and surgery (CARS’11), Int J CARS, vol 6, pp S306–S307Google Scholar
- 18.Cury FL, Shenouda G, Souhami L, Duclos M, Faria SL, David M, Verhaegen F, Corns R, Falco T (2006) Ultrasound-based image guided radiotherapy for prostate cancer: comparison of cross-modality and intramodality methods for daily localization during external beam radiotherapy. Int J Radiat Oncol Biol Phys 66(5):1562–1567CrossRefPubMedGoogle Scholar
- 19.Bruder R, Ernst F, Schweikard A (2011) SU-D-220-02: optimal transducer positions for 4D ultrasound guidance in cardiac IGRT. 53rd Annual meeting of the AAPM. Med Phys, vol 38, p 3390Google Scholar
- 20.Kuhlemann I, Bruder R, Ernst F, Schweikard A (2014) WEG-BRF-09: force-and image-adaptive strategies for robotised placement of 4D ultrasound probes. 56th Annual meeting of the AAPM. Med Phys, vol 41, p 523Google Scholar
- 21.Bortfeld T (2010) The number of beams in IMRT-theoretical investigations and implications for single-arc IMRT. Phys Med Biol 55(1):83–97Google Scholar
- 22.Stein J, Mohan R, Wang XH, Bortfeld T, Wu Q, Preiser K, Ling CC, Schlegel W (1997) Number and orientations of beams in intensity-modulated radiation treatments. Med Phys 24(2):149–160Google Scholar
- 28.Şen HT, Lediju BMA, Zhang Y, Ding K, Wong J, Iordachita I, Kazanzides P (2015) System integration and preliminary in-vivo experiments of a robot for ultrasound guidance and monitoring during radiotherapy. In: Proceedings of the international conference on advanced robotics, 2015, pp 53–59Google Scholar
- 30.Schlosser J, Hristov D (2016) Radiolucent 4D ultrasound imaging: system design and application to radiotherapy guidance. IEEE Trans Med Imaging. doi:10.1109/TMI.2016.2559499