Feasibility of application of deformable image registration to the dosimetry assessment of fractionated brachytherapy for cervical cancer / 中华放射医学与防护杂志

Objective:To study the differences in the cumulative dose between deformable image registration (DIR) and simple dose-volume histogram (DVH) summation in the fractionated brachytherapy of cervical cancer, and to analyze the feasibility of the application of DIR in the dosimetry assessment of targets and organs-at-risk (OARs) in the brachytherapy.Methods:A retrospective analysis was conducted for 13 cases with primary cervical cancer treated with four fractions of interstitial brachytherapy guided by CT images. The four CT images of each cases were registered using an intensity-based DIR. Then, the cumulative doses (the D2 cm 3, D1 cm 3, and D0.1 cm 3 of the bladder, rectum, intestine, and colon and the D90for targets) after DIR were calculated and compared to those obtained using simple DVH summation. Afterward, the correlation between the dose difference and dice similarity coefficient (DSC) was analyzed. With the dose difference (the remaining dose of OARs caused by the DIR) as limits, a new plan was made for the latest CT to calculate the dose increase to targets. Results:Compared to simple DVH summation, DIR allowed the cumulative doses of the D2 cm 3 and D1 cm 3 of bladder to be decreased by (2.47±1.92) and (2.82±2.73) Gy, respectively on average ( t=-3.65, -2.93, P < 0.05), those of the D2 cm 3, D1 cm 3, and D0.1 cm 3 of rectum to be decreased by (2.05 ± 1.61) Gy, (1.51 ± 1.58), and (3.21 ± 2.50) Gy, respectively on average ( t=-4.02, -3.02, -4.06, P < 0.05), and those of the D2 cm 3, D1 cm 3, and D0.1 cm 3 to be decreased by (1.42 ± 0.99), (1.55 ± 1.28) Gy, and (2.43 ± 1.95) Gy, respectively on average ( t=-3.52, -2.96, -3.06, P < 0.05). There was no significant statistical difference in the D90 of targets, the D0.1 cm 3 of the bladder, and the D2 cm 3, D1 cm 3, D0.1 cm 3 of the colon ( P > 0.05) between both methods, and there was no distinct correlation between DSC and dose difference ( P > 0.05). The DIR increased the dose to targets, with a median value of 150 cGy. However, the accuracy of the DIR should be improved. Conclusions:In clinical practice of multiple fractions of brachytherapy for cervical cancer, it′s still recommended to adopt the simple dose summation method to assess the doses to targets and OARs.

Study of the verification of the source positioning and dwelling time based on the well-chamber / 中华放射肿瘤学杂志

Objective:To establish a dosimetric method based on the well-chamber to verify the accuracy of the source positioning and dwelling time for the afterloading machine, aiming to provide a new method for the quality control of afterloading machine.Methods:The principle of this method was explained according to the hardware structure of the well-chamber. Then, the precision of this method was analyzed by the simulation test and data fitting. The feasibility test was also performed. And the advantages and disadvantages of this method were compared with those of the traditional method.Results:The precision of this method for detecting the source positioning was 0.07 mm and the dwelling time was 0.09 s, respectively. In the feasibility test, the standard deviation of the measure value was below 3%.Conclusions:The well-chamber method has high precision and convenient operation. It can be applied in the rapid verification of the relative accuracy of the source positioning and dwelling time of well-chamber.

Feasibility study of using two dimensional array ion-chamber to verifiy relative dose distribution calculated with Acuros BV / 中华放射医学与防护杂志

Objective To study the feasibility of using the PTW729 2D array ion-chamber to verify the relative dose distribution calculated with the Acuros BV algorithm.Both advantages and disadvantages of the method were analyzed to provide reference for practical clinical practices.Methods Based on self-built measurement phantoms,the dose distribution on the same slice of the phantom was measured with PTW729 and film,respectively,under the same measurement condition and plan.The dose distributions obtained by the two method were compared with the result calculated with Acuros BV,separately,by using γ analytical tool.And the stability of the PTW729 was tested.Results The γ comparison value was 95.9％ between the film and Acuros BV,98.9％ between the PTW729 and Acuros BV and 88.0％ between the film and PTW729,with 95.0％,i00.0％,and 100.0％,in their stability test respectively.Conclusions PTW729 2D array ion-chamber can be applied to the rapid verification of Acuros BV algorithm-calculated relative dose distribution.

Feasibility study of using two dimensional array ion-chamber to verifiy relative dose distribution calculated with Acuros BV / 中华放射医学与防护杂志

Objective@#To study the feasibility of using the PTW729 2D array ion-chamber to verify the relative dose distribution calculated with the Acuros BV algorithm. Both advantages and disadvantages of the method were analyzed to provide reference for practical clinical practices.@*Methods@#Based on self-built measurement phantoms, the dose distribution on the same slice of the phantom was measured with PTW729 and film, respectively, under the same measurement condition and plan. The dose distributions obtained by the two method were compared with the result calculated with Acuros BV, separately, by using γ analytical tool. And the stability of the PTW729 was tested.@*Results@#The γ comparison value was 95.9% between the film and Acuros BV, 98.9% between the PTW729 and Acuros BV and 88.0% between the film and PTW729, with 95.0%, 100.0%, and 100.0%, in their stability test respectively.@*Conclusions@#PTW729 2D array ion-chamber can be applied to the rapid verification of Acuros BV algorithm-calculated relative dose distribution.

Effects of magnetic resonance diffusion weighted image on the target volume delineation of advanced esophageal cancer / 西安交通大学学报(医学版)

Objective To investigate the value of DWI imaging combined with T2WI imaging and CT image fusion technology and explore the role of DWI imaging in the determination of target areas in radiotherapy for advanced esophageal cancer.Methods Twenty-three patients with locally advanced esophageal cancer were included in this study.All the patients were fixed by a heat plastic device.Each patient was examined by CT,T2WI and DWI scan in the same position as the radiotherapy treatment.Images obtained from the three sequences were transmitted to the Eclipse 11.0 treatment planning system.All images were registered at Eclipse workstation as to normalized mutual information registration.The target areas were delineated by the clinical radiation physicians in the CT imaging,and CT and DWI fusion images.The target areas of the two kinds of image were evaluated using fusion function and statistical function of the treatment planning system.Results Target parameters differed significantly between CT base and CT/MRI fusion base.The results of the target volume outline closer by CT and MRI fusion image base in the three groups of clinicians.Conclusion The target volume between the groups is closer by using CT and DWI fusion image.DWI image has a good assisting effect in determining the target area of locally advanced esophageal cancer.