Study On The Technique Of Conventional Video Camera Optical Image-guided Heavy Ion Radiotherapy

Radiotherapy is one of the important methods of treating cancer,Imaged guided radiotherapy(IGRT)is a key technology for precise extra radiotherapy.The dose of heavy ion which has special biophysical properties can be delivered to the tumor tissue precisely,so the heavy ion radiotherapy technology can protect the normal tissue of the patient precisely.In modern times,the images of the IGRT technologies used are orthogonal digital X ray image / on rail CT image / CBCT image / gold markers implanted in to the patient body imaged by the X-ray / infrared markers and infrared camera /laser camera scanning images and so on.These images devices are so expensive and most of these devices can deliver extra doses to the normal tissue of the patient,some complications may occur surrounding the normal tissue caused by the extra doses,so these IGRT technologies cannot be used to verify and guide the patient positioning in real time for a long time.To avoid these disadvantages,firstly,simple hardware system and algorithm flows with conventional video cameras were designed in our laboratory.Secondly a novel simple method using conventional video camera was designed to guide and verify the patient positioning in this paper by us.Thirdly,a new method to achieved patient respiratory signal was developed with conventional video camera;we could get the signal of patient respiratory according to the surface skin of patient to guide the motioning tumor target treatment for heavy ion radiotherapy.A new image guided radiotherapy system was designed with three conventional video cameras according the heavy ion treatment room in our laboratory in this paper.Three conventional video cameras were installed around a patient treatment couch from three different directions;the real-time images of the three cameras were delivered to a graphic workstation with a multi-pass video capture card.A self-adaption background deleted algorithm were developed,this algorithm can deleted the background of the images which were used according the difference image of the real-time video camera images and the stand patient positioning reference image,a region of interest(ROI)which contains all the shifted regions and excludes the background of the image.We modified the Oriented FAST and Rotated BRIEF(ORB)algorithm which was used widely to achieve the corner points of the ROI of the real-time images and the reference image.The modified ORB algorithm can achieve the corner points only in the patient body and the treatment couch,the two images can be registered by the descriptors of every corner point calculated with the modified ORB algorithm.The shifting data of the patient body which is used to guide and verify the patient positioning in treatment time.The treatment should be stopped if the shifting data is bigger than the setting threshold data in real time,and the patient should be reposition guided by the patient positioning shifting data.In order to verify the feasibility and accuracy of the novel patient positioning monitoring method designed in this paper,a simulation treatment room and a image guided radiotherapy system with conventional video cameras were set up.In the simulation treatment room,a plastic patient model immobilized with thermoplastic shell on a simulation couch was used.We test our method when the plastic patient model was shifted and rotated at different data in different time.Testing results showed that the position and angle offset errors identified with our system were less than 1 mm and 1 degree,respectively.Moreover,the modified ORB algorithm was fast enough for real-time images comparison.A new method to get the respiratory signal with conventional video camera was designed in this paper too.A respirator signal achieved to analyze variation of thorax-abdomen surface skin by real-time conventional video camera image in real time.A simulation patient respiratory device was designed to verify the algorithm,the testing results shown the method is feasible and accurate.In all,the new image guided radiotherapy technology with conventional video cameras designed in this paper can be used in heavy ion radiotherapy treatment room.This IGRT technology will not deliver any extra dosage to the patient,and this method cannot do any psychological harm to the patient.The method is very cheap,and it can be used evasively and widely.We will test this method in clinical trial in the near future.