Real-time opto-electronic verification of patient position in breast cancer radiotherapy.

OBJECTIVE The clinical application of an opto-electronic system for real-time three-dimensional (3D) control of patient position in breast cancer radiotherapy is described. The specific features of the motion analysis technology (shape recognition of passive markers) are detailed, and the outcomes of its clinical use for quantitative position control and immobility verification of the thoracic irradiation field during breast cancer treatment are reported. MATERIALS AND METHODS The position control system is based on the ELITEtrade mark opto-electronic motion analyzer, which provides in real time the 3D coordinates of a set of passive markers (plastic hemispheres 3 mm in diameter) previously placed on selected landmarks on the patient's skin. The system-dedicated hardware performs marker recognition by means of 2D correlation of shape with a predefined marker modeling mask. This feature ensures a high accuracy, even with small marker dimensions, and successful analysis in a noisy environment (due to room light, reflexes, etc.). The patient repositioning control was based on a comparison between the current positions of the markers and a corresponding reference configuration. The resulting marker displacements were graphically displayed in real time for immediate control. This information was not provided to the operator as a repositioning tool. Instead, the kinematic data was stored for subsequent off-line analysis aimed at quantifying the different factors contributing to patient mis-positioning (initial repositioning errors, patient's breathing, and random movements) when conventional means for patient alignment (laser centering) and immobilization (casting techniques) are used. RESULTS Clinical application of the system revealed median 3D localization errors for the directly controlled anatomical landmarks of around 4.5 mm. This value is proposed to represent the intrinsic accuracy of conventional laser-centering techniques in breast cancer radiotherapy, including the effects of patient body deformations. When the positional inaccuracies introduced by patients' respiration were also considered, the extent of the resulting 3D mis-positioning of the control points increased to median values of up to 8 mm. CONCLUSIONS The reported clinical trial confirms the significant role that real-time opto-electronic motion analysis based on passive markers can have in augmenting the accuracy of patient repositioning and immobility verification in the radiotherapy of a non-rigid body area while also accounting for physiological movements. Evaluation of the data collected during each irradiation session for five patients provided valuable information concerning the optimization of the efficacy of traditional methods for patient centering and immobilization.

[1]  L P Adams,et al.  Determining locations of intracerebral lesions for proton radiotherapy. , 1993, Physics in medicine and biology.

[2]  W Schlegel,et al.  Photogrammetric accuracy measurements of head holder systems used for fractionated radiotherapy. , 1994, International journal of radiation oncology, biology, physics.

[3]  G Ferrigno,et al.  Optoelectronic techniques for patient repositioning in radiotherapy. , 1996, Technology and health care : official journal of the European Society for Engineering and Medicine.

[4]  R Orecchia,et al.  [Assessment of the accuracy of position in breast irradiation with isocentric technique using an electronic system to acquire portal images]. , 1997, La Radiologia medica.

[5]  P. Munro,et al.  Portal Imaging Technology: Past, Present, and Future. , 1995, Seminars in radiation oncology.

[6]  N G Burnet,et al.  Accuracy of patient positioning during radiotherapy for bladder and brain tumours. , 1999, Clinical oncology (Royal College of Radiologists (Great Britain)).

[7]  Giancarlo Ferrigno,et al.  Pattern recognition in 3D automatic human motion analysis , 1990 .

[8]  N A Borghese,et al.  Statistical comparison of DLT versus ILSSC in the calibration of a photogrammetric stereo-system. , 1997, Journal of biomechanics.

[9]  A Pedotti,et al.  Complete calibration of a stereo photogrammetric system through control points of unknown coordinates. , 1998, Journal of biomechanics.

[10]  H. M. Karara,et al.  Direct Linear Transformation from Comparator Coordinates into Object Space Coordinates in Close-Range Photogrammetry , 2015 .

[11]  Giancarlo Ferrigno,et al.  Elite: A Digital Dedicated Hardware System for Movement Analysis Via Real-Time TV Signal Processing , 1985, IEEE Transactions on Biomedical Engineering.

[12]  T. Sarrazin,et al.  Utilisation d'un système d'imagerie en temps réel dans le contrôle quotidien de patients traités par irradiation pour un cancer thoracique , 1997 .

[13]  G Ferrigno,et al.  Three-dimensional optical analysis of chest wall motion. , 1994, Journal of applied physiology.

[14]  A. Dutreix When and how can we improve precision in radiotherapy? , 1984, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[15]  R. L. Harris,et al.  The use of an optical outlining system for weekly on-set verification of patients with carcinoma of the breast. , 1998, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[16]  G Ferrigno,et al.  Real-time three-dimensional motion analysis for patient positioning verification. , 2000, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[17]  Michael G. Herman,et al.  CLINICAL USE OF ON-LINE PORTAL IMAGING FOR DAILY PATIENT TREATMENT VERIFICATION , 1994 .

[18]  H D Kubo,et al.  Accuracy of a photogrammetry-based patient positioning and monitoring system for radiation therapy. , 1999, Medical physics.

[19]  L. Verhey,et al.  Immobilizing and Positioning Patients for Radiotherapy. , 1995, Seminars in radiation oncology.