In this paper, two new concepts of DR (Dose Repulsion) and DG (Dose Gravitation) are presented with their calculation formulas. For the problem of selecting beam arcs in x-knife radiotherapy Planning system, a mathematics model of constrained optimization has been built. Furthermore, we have produced a feasible project of automatic selecting optimized beam arcs plan using SA (Simulated Annealing) arithmetic based on the distribution of the fields of DR and DG in the reduced phase space.
Algorithms ; Brain Neoplasms ; radiotherapy ; Models, Theoretical ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted ; methods ; Radiotherapy, Conformal ; methods

Conformal radiation therapy using multi-leaf collimator (MLC) is considered as a conventional technology in the hospital nowadays. However the stepped leaf edge caused by the finite width of the leaves could influence the conformality that could be achievable. In this paper, the effect produced by rotating the collimator angle on the conformality was investigated. A method, in which multiple MLC fields of various rotation angles are applied, has been proposed to have the targets be more uniformly irradiated and thus to eliminate the cold spots on the targets and hot spots in normal tissues. By simulation, it has been shown that the multiple MLC field method can eliminate the stepped leaf edges and improve the conformality significantly, moreover, the PTV can receive a more uniform delivery with cold spot eliminated.
Humans ; Radiometry ; methods ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted ; instrumentation ; methods ; Radiotherapy, Conformal ; methods

OBJECTIVETo validate the efficiency of an improved Demons deformable registration algorithm and evaluate its application in registration of the treatment image and the planning image in image-guided radiotherapy (IGRT).

METHODSBased on Brox's gradient constancy assumption and Malis's efficient second-order minimization algorithm, a grey value gradient similarity term was added into the original energy function, and a formula was derived to calculate the update of transformation field. The limited Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) algorithm was used to optimize the energy function for automatic determination of the iteration number. The proposed algorithm was validated using mathematically deformed images, physically deformed phantom images and clinical tumor images.

RESULTSCompared with the original Additive Demons algorithm, the improved Demons algorithm achieved a higher precision and a faster convergence speed.

CONCLUSIONDue to the influence of different scanning conditions in fractionated radiation, the density range of the treatment image and the planning image may be different. The improved Demons algorithm can achieve faster and more accurate radiotherapy.

Algorithms ; Humans ; Liver Neoplasms ; radiotherapy ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted ; methods ; Radiotherapy, Conformal ; methods ; Radiotherapy, Image-Guided ; methods

OBJECTIVEThe study was to explore effort of planning parameters by analyzing the result of Gamma pass rates for IMRT verification for Pinnacle planning system.

METHODS5 Head Neck IMRT plans finished by Xio planning system were imported into Pinnacle planning system. Different algorithms and calculation grids were used to calculate the dose distributions for 3 orthogonal planes at isocenter which were exported in 3 kind grids. Mapcheck software was used to calculate the Gamma pass rate using the plane dose distributions from Xio system as the reference ones simulating the measurements.

RESULTThe difference of Gamma pass rates for 3 kinds of algorithm and calculation grids were of statistical significance.

CONCLUSIONThe parameters in Pinnacle planning system may have influence on Gamma pass rates. It needs further discussion to directly use the Gamma pass rates in documents during the establishing of IMRT QA protocol.

Algorithms ; Gamma Rays ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted ; methods ; Radiotherapy, Conformal ; methods ; Software

An intensity modulated method by scanning for the focusing therapy machine is introduced in this paper. At first, the 3-D model of the focus is delaminated through the treatment planning system, and the dose distributing of each lay is calculated by an inverse design method. Then, the exposure time of the focus at each position is determined and converted to a scanning parameter, such as position, speed and so on. Afterward, the focus continuously scans the tumor at different speeds along the planned track under the control of the computer. Consequently the point-by- point intensity modulation is achieved through the diversification of the scanning speed of the focus.
Humans ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted ; instrumentation ; methods ; Radiotherapy, Conformal ; instrumentation ; methods

Dose calculation plays a key role in treatment planning of radiotherapy. Algorithms for dose calculation require high accuracy and computational efficiency. Finite size pencil beam (FSPB) algorithm is a method commonly adopted in the treatment planning system for radiotherapy. However, improvement on its computational efficiency is still desirable for such purpose as real time treatment planning. In this paper, we present an implementation of the FSPB, by which the most time-consuming parts in the algorithm are parallelized and ported on graphic processing unit (GPU). Compared with the FSPB completely running on central processing unit (CPU), the GPU-implemented FSPB can speed up the dose calculation for 25-35 times on a low price GPU (Geforce GT320) and for 55-100 times on a Tesla C1060, indicating that the GPU-implemented FSPB can provide fast enough dose calculations for real-time treatment planning.
Algorithms ; Computer Graphics ; Humans ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted ; methods ; Radiotherapy, Conformal ; methods

As a powerful global optimization approach, genetic algorithms (GA) can solve a variety of optimization problems in which the objective function is discontinuous, non-differentiable, or highly non-linear, to produce high convergence speed and vast search space. In this thesis, GA is used to optimize the beam weights of intensity modulated radiation therapy (IMRT) inverse planning, and 2D and 3D isodose contour as well as dose volume histogram (DVH) are used to evaluate the treatment plan. Also presented in this thesis are the results of calculation with discussions.
Algorithms ; Humans ; Models, Theoretical ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted ; methods ; Radiotherapy, Conformal ; methods ; standards

OBJECTIVETo increase the accuracy of beam targeting and improve the dose distributions in radiotherapy using a robust image registration algorithm based on control volumes.

METHODSControl volume mapping and thin-plate spline deformable transformation were combined. The use of the control volumes increased the accuracy for the deformable registration. A bi-directional mapping method was also employed to correctly match the control volumes.

RESULTSThe clinical images were simulated using the proposed two-step image registration algorithm. The simulation results indicated that the registration algorithm was robust and universal, even in cases of obvious deformation.

CONCLUSIONSThe algorithm provides a more convenient and robust resolution as compared to manual landmark-based methods and single-step deformable transformations, and may help in automatic image registration in radiation therapy.

Algorithms ; Humans ; Image Processing, Computer-Assisted ; Radiotherapy Planning, Computer-Assisted ; methods ; Radiotherapy, Conformal ; methods

BACKGROUNDThe role of internal mammary nodes (IMN) irradiation for breast cancer patients after mastectomy remains controversial. This study aimed to compare different techniques for radiation of the chest wall (CW) and IMN post-mastectomy for left-breast cancer patients in terms of dose homogeneity within planning target volume (PTV) and dose to critical structures.

METHODSThirty patients underwent CT simulation, while CW, IMN, left lung, heart and contralateral breast were contoured. Three three-dimensional conformal radiotherapy (3D-CRT) techniques, namely, standard tangents, partially wide tangents (PWT), and modified PWT techniques plus intensity modulated radiotherapy (IMRT) technique have been used to radiate CW and IMN. In addition to the target coverage and dose homogeneity, we also evaluated the dose to the critical structures including heart, left lung and contralateral breast.

RESULTSAll three 3D-CRT techniques provided satisfactory coverage regarding total PTV. The PWT and the modified PWT gave better coverage of IMN PTV with V(47.5) of (96.83 ± 4.56)% and (95.19 ± 3.90)% compared to standard tangents ((88.16 ± 7.77)%), P < 0.05. The standard tangents also contributed the biggest IMN V(D105%), V(D110%), V(D115%) and V(D120%). The lowest mean dose of the heart was achieved by the modified PWT ((8.47 ± 2.30) Gy), compared with PWT ((11.97 ± 3.54) Gy) and standard tangents ((11.18 ± 2.53) Gy). The mean dose of lung and contralateral breast with the modified PWT was significantly lower than those with PWT. Comparing IMRT with the modified PWT, both techniques provided satisfactory coverage. The conformity indexes (CI) with IMRT (CI1: 0.71 ± 0.02; CI2: 0.64 ± 0.02) were better than those with the modified PWT (CI1: 0.50 ± 0.02; CI2: 0.45 ± 0.02). The mean dose, V(5), V(10) and V(5-10) of heart and left lung with the modified PWT were significantly lower than those with the IMRT. The mean dose and V(D2%) of contralateral breast with the modified PWT were not significantly different from the IMRT (P = 0.868 and P = 0.212).

CONCLUSIONSNo single technique provides both the best CW and IMN coverage with minimum lung and heart dose. The modified PWT technique can be used as a clinical tool for the treatment of the left-sided post-mastectomy breast cancer patients to provide homogeneous target coverage while maintaining low doses to normal tissue.

Breast Neoplasms ; radiotherapy ; surgery ; Combined Modality Therapy ; Female ; Humans ; Mastectomy ; Radiotherapy Dosage ; Radiotherapy, Conformal ; methods ; Radiotherapy, Intensity-Modulated ; methods

Simplified dose calculation model with high computation efficiency is often used to generate the dose matrices for beamlets in the inverse planning of the intensity modulate radiation therapy. It is likely that this simplification could degrade the quality of the final treatment plans. This paper is aimed at testing the influence of such simplification in dose calculations of beamlets and accordingly proposing methods to avoid severe degradation of the plans. Two simulation instances were adopted. The primary dose calculation model without involvment of scattering effect was used to generate the dose matrices of beamlets. The differential convolution superposition dose calculation model that well accounts for scattering effect was used to calculate the final dose distributions for given intensity profiles. It is found that the simplification in dose matrices of beamlets degrades the dose levels in the edge area of the targets, however, the degradation could be diminished or even avoided by adding a suitable margin around the targets or by using the multiple-shifted-beamlet-matrices (MSBM) method that was proposed in our previous paper.
Humans ; Radiometry ; methods ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted ; methods ; statistics & numerical data ; Radiotherapy, Conformal ; methods ; Scattering, Radiation