Development of a semi-automated superimposing image verification system using a template matching algorithm in radiotherapy.

To analyze shifts in the isocenter of images, we developed a semi-automated superimposing image-verification system that is capable of automatically quantifying shifts in the isocenter through image analysis with a personal computer (PC). The accuracy and usefulness of this software were examined through a comparison of nine portal images with a simulation image and by comparing nine portal images with a DRR image, using a human pelvic phantom. The difference between the known magnitude of shift and the magnitude of shift detected with this method was analyzed as detection error. When the portal images were compared with the simulation image, the 95% confidence interval (95% CI) of detection errors (mean+/-SD) was 0.57+/-0.36 mm (95% CI: 0.49-0.65 mm). When the portal images were compared with the DRR image, the respective figures were 0.68+/-0.38 mm (95% CI: 0.59-0.77 mm). No significant difference was noted between these two categories of comparison (N.S). The absolute detection error (mean+/-SD) in all directions was 0.34+/-0.34 mm for the comparison of portal images with the simulation image and 0.41+/-0.36 mm for the comparison of portal images with the DRR image. This system seems to be appropriate for verification of the treatment field by improving the accuracy of radiotherapy as a method of computer-assisted landmark recognition during image comparison.

[1]  B. Heijmen,et al.  Analysis and reduction of 3D systematic and random setup errors during the simulation and treatment of lung cancer patients with CT-based external beam radiotherapy dose planning. , 2001, International journal of radiation oncology, biology, physics.

[2]  Michael G Herman,et al.  Technical aspects of daily online positioning of the prostate for three-dimensional conformal radiotherapy using an electronic portal imaging device. , 2003, International journal of radiation oncology, biology, physics.

[3]  Robert J. Shalek,et al.  Physical Aspects of Quality Assurance in Radiation Therapy , 1984 .

[4]  Suresh Senan,et al.  Procedures for high precision setup verification and correction of lung cancer patients using CT-simulation and digitally reconstructed radiographs (DRR). , 2003, International journal of radiation oncology, biology, physics.

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

[6]  Mark Rose,et al.  Can digitally reconstructed radiographs (DRRS) replace simulation films in prostate cancer conformal radiotherapy? , 2003, International journal of radiation oncology, biology, physics.

[7]  J. Palta,et al.  Comprehensive QA for radiation oncology: report of AAPM Radiation Therapy Committee Task Group 40. , 1994, Medical physics.

[8]  G. Starkschall,et al.  American Association of Physicists in Medicine Radiation Therapy Committee Task Group 53: quality assurance for clinical radiotherapy treatment planning. , 1998, Medical physics.

[9]  Takashi Okada,et al.  [Development of automatic verification system for portal image in radiotherapy]. , 2004, Nihon Hoshasen Gijutsu Gakkai zasshi.

[10]  C Yang,et al.  Use of digitally reconstructed radiographs in radiotherapy treatment planning and verification. , 2000, Australasian radiology.

[11]  E H Baldini,et al.  A technique for optimization of digitally reconstructed radiographs of the chest in virtual simulation. , 2001, International journal of radiation oncology, biology, physics.

[12]  Yuzo Kikuchi,et al.  [Study of optimal imaging parameters for digitally reconstructed radiographs (DRR) in radiotherapy treatment planning using single-slice helical CT]. , 2004, Nihon Hoshasen Gijutsu Gakkai zasshi.

[13]  J. Palta,et al.  Comprehensive QA for Radiation Oncology , 1994 .

[14]  Jürgen Debus,et al.  Clinical results of retreatment of vertebral bone metastases by stereotactic conformal radiotherapy and intensity-modulated radiotherapy. , 2002, International journal of radiation oncology, biology, physics.