An orthogonal moment-based method for automatic verification of radiation field shape.

The purpose of this paper is to develop a new method for automated on-line verification of the treatment field shape during radiotherapy. The treatment field boundary is extracted from the digital portal image and is then approximated by a polygon. The proposed procedure used one of the approved field shapes as the reference boundary for automated comparison with subsequent portal field boundaries. The orthogonal moment-based method was applied to align treatment field boundaries that include the translational shifts, scaling factor and rotation angle. Firstly, the moments of order up to one were used to adjust the magnification and translation of the test field boundary related to the reference one; this step created a common coordinate system for the two images. Then a quadratic least-square objective function based on the orthogonal moments (e.g. Legendre moments) of the two field shapes was employed to perform rotational correction. Since moment computation by a straightforward method required a large number of multiplication and addition operations, a fast method for computing Legendre moments was also developed to decrease the calculation time. Application of the method to some simulated cases showed that our alignment procedure has an accuracy of 0.5 mm in detecting translational shift, 0.004 in detecting magnification and less than 0.3 degrees in detecting rotation angle between the test shape and the reference shape. The alignment procedure using the proposed method can be done within 2 s on a Pentium II personal computer. Therefore, our method is potentially useful for automated real-time treatment field shape verification.

[1]  Rasika Rajapakshe,et al.  Pseudocorrelation: a fast, robust, absolute, grey-level image alignment algorithm. , 1994 .

[2]  文献委員会.  Use of digital fluoroscopy as an on-line verification device in radiation therapy., Leong J., Phys. Med. Biol., 31(9), 985-992, (1986). : [放射線治療] , 1987 .

[3]  K W Leszczynski,et al.  Verification of radiotherapy treatments: computerized analysis of the size and shape of radiation fields. , 1993, Medical physics.

[4]  P. Munro,et al.  A review of electronic portal imaging devices (EPIDs). , 1992, Medical physics.

[5]  Huazhong Shu,et al.  A new fast method for computing Legendre moments , 2000, Pattern Recognit..

[6]  S. Shalev,et al.  A ρ‐θ technique for treatment verification in radiotherapy and its clinical applications , 1993 .

[7]  YANG WANG,et al.  On parameter-dependent connected components of gray images , 1996, Pattern Recognit..

[8]  BIMAL KUMAR RAY,et al.  Determination of optimal polygon from digital curve using L1 norm , 1993, Pattern Recognit..

[9]  M van Herk,et al.  Automatic on-line inspection of patient setup in radiation therapy using digital portal images. , 1993, Medical physics.

[10]  K. R. Ramakrishnan,et al.  Fast computation of Legendre and Zernike moments , 1995, Pattern Recognit..

[11]  A G Visser,et al.  Accuracy in radiation field alignment in head and neck cancer: a prospective study. , 1988, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[12]  M Coghe,et al.  Routine clinical on-line portal imaging followed by immediate field adjustment using a tele-controlled patient couch. , 1992, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[13]  Fritz Albregtsen,et al.  Fast Computation of Three-Dimensional Geometric Moments Using a Discrete Divergence Theorem and a Generalization to Higher Dimensions , 1997, CVGIP Graph. Model. Image Process..

[14]  K. Eilertsen,et al.  Methods for fully automated verification of patient set-up in external beam radiotherapy with polygon shaped fields. , 1994, Physics in medicine and biology.

[15]  Huazhong Shu,et al.  An Efficient Method for Computation of Legendre Moments , 2000, Graph. Model..

[16]  Sugata Ghosal,et al.  Orthogonal moment operators for subpixel edge detection , 1993, Pattern Recognit..

[17]  J W Wong,et al.  Study of treatment variation in the radiotherapy of head and neck tumors using a fiber-optic on-line radiotherapy imaging system. , 1991, International journal of radiation oncology, biology, physics.

[18]  M van Herk,et al.  Automatic verification of radiation field shape using digital portal images. , 1992, Medical physics.

[19]  Horst Bunke,et al.  Simple and fast computation of moments , 1991, Pattern Recognit..

[21]  J. Leong,et al.  Use of digital fluoroscopy as an on-line verification device in radiation therapy. , 1986, Physics in medicine and biology.

[22]  J Moseley,et al.  A semiautomatic method for registration of portal images. , 1994, Medical physics.

[23]  Dinggang Shen,et al.  Discriminative wavelet shape descriptors for recognition of 2-D patterns , 1999, Pattern Recognit..

[24]  K. Leszczynski,et al.  The enhancement of radiotherapy verification images by an automated edge detection technique. , 1992, Medical physics.

[25]  M. Teague.  Image analysis via the general theory of moments , 1980 .

[26]  P. Dunscombe,et al.  A comparative study of methods for the registration of pairs of radiation fields , 1993 .

[27]  S M Zhou,et al.  A robust method of multileaf collimator (MLC) leaf-configuration verification. , 1994, Physics in medicine and biology.

[28]  Fritz Albregtsen,et al.  Fast and exact computation of Cartesian geometric moments using discrete Green's theorem , 1996, Pattern Recognit..

[29]  K S Lam,et al.  An on-line electronic portal imaging system for external beam radiotherapy. , 1986, The British journal of radiology.

[30]  M van Herk,et al.  Radiation field edge detection in portal images. , 1991, Physics in medicine and biology.

[31]  L Dong,et al.  A portal image alignment and patient setup verification procedure using moments and correlation techniques. , 1996, Physics in medicine and biology.

[32]  A L Boyer,et al.  Investigation of an FFT-based correlation technique for verification of radiation treatment setup. , 1991, Medical physics.

[33]  M. Goitein,et al.  Accuracy of radiation field alignment in clinical practice. , 1985, International journal of radiation oncology, biology, physics.

[34]  Jean-Louis Coatrieux,et al.  A moment-based three-dimensional edge operator , 1993 .