ABSTRACT
Objective:To propose a markerless beam's eye view (BEV) tumor tracking algorithm, which can be applied to megavolt (MV) images with poor image quality, multi-leaf collimator (MLC) occlusion and non-rigid deformation.Methods:Window template matching, image structure transformation and demons non-rigid registration method were used to solve the registration problem in MV images. The quality assurance (QA) plan was generated in the phantom and executed after manually setting the treatment offset on the accelerator, and 682 electronic portal imaging device (EPID) images in the treatment process were collected as fixed images. Meanwhile, the digitally reconstructured radiograph (DRR) images corresponding to the field angle in the planning system were collected as floating images to verify the accuracy of the algorithm. In addition, a total of 533 images were collected from 21 cases of lung tumor treatment data for tumor tracking study, providing quantitative results of tumor location changes during treatment. Image similarity was used for third-party verification of tracking results.Results:The algorithm could cope with different degrees (10%-80%) of image missing. In the phantom verification, 86.8% of the tracking errors were less than 3 mm, and 80% were less than 2 mm. Normalized mutual information (NMI) varied from 1.182±0.026 to 1.202±0.027 ( P<0.005) before and after registration and the change of Hausdorff distance (HD) was from 57.767±6.474 to 56.664±6.733 ( P<0.005). The case results were predominantly translational (-6.0 mm to 6.2 mm), but non-rigid deformation still existed. NMI varied from 1.216±0.031 to 1.225±0.031 ( P<0.005) before and after registration and the change of HD was from 46.384±7.698 to 45.691±8.089 ( P<0.005). Conclusions:The proposed algorithm can cope with different degrees of image missing and performs well in non-rigid registration with data missing images which can be applied in different radiotherapy technologies. It provides a reference idea for processing MV images with multi-modality, partial data and poor image quality.
ABSTRACT
Objective To study the morphology of normal liver and tumors by breathing motion of hepatocellular carcinoma patients,through comparing the modified demons algorithm and FFD algorithm based on B-spline,and combing four-dimensional computed tomography (4DCT).Methods The 4DCT images of 8 HCC patients were segmented into 10-series which were named CT0,CT10 … CT80,CT90 according to the respiratory phases,CT0 and CT50 are defined to be end-inhale and end-exhale respectively.CT50 was chosen as the reference image.We used the modified demons algorithm and FFD algorithm based on B-spline to deform the images.Linear interpolation was used in both mode 1 and mode 2.The normalized mutual information (NMI),Hausdorff distance (dH) and registration speed were used to verify the registration performance.Results The average NMI for the end-inhale and end-exhale images of 8 HCC patients after demons registration in mode 1 improved 4.75％ with FFD algorithm based on B-spline(P =0.002).And the difference of dH after demons reduced 15.2％ comparing with FFD model algorithm (P =0.02).In addition,demons algorithm has the absolute advantage in registration speed(P =0.036).Conclusions The breathing movement for deformation of normal liver and tumor targets is significant.These two algorithms can achieve the registration of 4DCT images and the modified demons registration can deform 4DCT images effectively.
ABSTRACT
En este artículo pretendo mostrar que: 1. Para los fundadores de la genética de poblaciones, Fisher y Wright, existía una relación muy estrecha entre la física y la biología. 2. El deseo de matematizar la genética de poblaciones buscaba darle al evolucionismo el estatus de -ciencia dura-, al mismo nivel que la física de Boltzmann y Maxwell. 3. Este esfuerzo estuvo orientado a mostrar que la evolución por selección natural no se opone a las leyes termodinámicas que rigen la evolución de los sistemas físicos. 4. La metáfora que paradójicamente presenta a los seres vivos como -demonios de Maxwell- anticipó aspectos de las teorías evolutivas modernas que recurren a las ciencias de la información y la termodinámica de sistemas complejos adaptativos desarrolladas por Prigogine en 1970 y Kauffman en 1993. 5. Para finalizar presento un contraste entre Darwin y Einstein que permite esclarecer mejor los puentes y conexiones bidireccionales que se establecen entre la biología y la física.
This paper aims to illustrate: 1. that for the founders of population genetics, Fisher and Wright, there was a close relationship between physics and biology. 2. The mathematics of population genetics aimed at placing evolutionary theory as a -hard science- at the same level as Boltzmann and Maxwells physics. 3. This effort showed that the concept of evolution by natural selection does not contradict the laws of thermodynamics that rule the evolution of physical systems. 4. The metaphor that paradoxically represents living beings as -Maxwellian demons- anticipated some aspects of the present day evolutionary theories that recur to the thermodynamic of complex adaptive systems as developed by Prigogine, 1970, and Kauffman, 1993. 5. To conclude, I contrast Darwin and Einstein in order to clarify, how can be understood today, the bridges and bidirectional connections between physics and biology.