Objective:To investigate the protection of Active Breathing Coordinator(ABC)technique for heart and its substructures in radiotherapy for left breast cancer.Methods:A total of 50 patients with left breast cancer who underwent radiotherapy in our department were retrospectively selected,and treatment plans with intensity modulated radiotherapy(IMRT)were designed on the images of ABC combined with deep inspiration breath hold(ABC-DIBH)computed tomography(CT)and free-breathing(FB)CT,respectively.The dose parameters of the organ at risks(OARs)of heart and its substructures,including left ventricle(LV),left atrium(LA),right ventricle(RV),right atrium(RA),left main coronary artery(LMCA),left anterior descending coronary artery(LAD),left circumflex coronary artery(LCX)and right coronary artery(RCA),were compared between the two conditions.Results:Compared with FB,the dose of 2%volume(D2),the mean dose(Dmean),the percent volumes covered by different doses(V30,V20,V10,V5)decreased respectively 32.91%(absolute reduction of 1279.11 cGy),36.12%(195.94cGy),58.95%(2.8%),54.32%(3.58%),50.14%(5.56%)and 46.22%(9.67%)of heart under ABC-DIBH condition,and the differences were significant(t=10.28,12.81,9.16,10.28,12.82,12.24,P＜0.01),respectively.In addition,the Dmean values of LV,LA,RV,RA,LMCA,LAD,LCX and RCA decreased by 37.64%(absolute reduction was 285.92 cGy),15.38%(23.68 cGy),34.12%(118.93cGy),9.72%(12.52 cGy),22.17%(47.99 cGy),31.81%(820.63 cGy),16.51%(34.72 cGy)and 14.86%(34.11cGy)under ABC-DIBH condition,respectively,the differences were significant(t=9.50,3.71,6.20,8.65,3.18,10.92,4.26,6.71,P＜0.05).Conclusion:ABC technique can greatly reduce the received doses of heart and its substructures by extending the distance between the heart and the target region with DIBH,thus can form a very effective protection for the heart and its substructures.In addition,it can eliminate the dynamic variation of target location of breast cancer caused by respiratory,and avoid a series of problems,such as target missing,overexposure on normal tissue,and dose deviation.

Objective:To compare the dosimetric differences between active breathing coordinator (ABC) and Catalyst for respiratory gating after breast conserving surgery for left breast cancer.Methods:Data of 48 female patients with left breast cancer after breast conserving surgery admitted to the Radiotherapy Department of Shenzhen People′s Hospital from November 2020 to August 2021 were retrospectively selected. They were randomized to receive dynamic intensity modulated radiotherapy (IMRT) plans with ABC or Catalyst. The dosimetric differences in targets and organs at risk between the two groups were analyzed.Results:Comparison of the two respiratory gating IMRT plans revealed no statistically significant differences ( P > 0.05) in D90%, D98%, Dmax, Dmean, conformity index (CI), homogeneity index (HI), and monitor unit parameters in the target volume, (i.e., chest wall), as well as the ipsilateral lung and heart under the deep inhalation breath hold (DIBH) mode. The Dmean, Dmax, and D2% of the left anterior descending coronary artery (LAD) in the Catalyst group were better than those in the ABC group [(1 047.72 ± 1 401.84) vs. (454.48 ± 206.26), (1 619.28 ± 809.05) vs.(1 068.53 ± 419.63), (1 405.85 ± 798.30) vs. (1 016.54 ± 592.00) cGy], with statistically significant differences ( t= -2.07, -3.18, -2.07, P<0.05). Conclusions:Both ABC and Catalyst respiratory gating systems meet the requirements for clinical treatment, with the latter more effective in reducing the exposure dose of LAD.

Objective:To compare translational and rotational setup errors between immobilization with open masks combined with positioning with the optical surface monitoring system (OSMS) and immobilization with full masks combined with positioning with laser lights and mask markers, find the advantages of open masks combined with OSMS in hypofractionated stereotactic radiotherapy (HSRT) for brain metastases, and calculate planning target volume (PTV) expansions with different immobilization and positioning method for patients with brain metastases.Methods:The setup data of 55 patients with brain metastases who received HSRT were analyzed retrospectively. According to immobilization and positioning method, the patients were divided into group A (OSMS + open masks), group B1 (full head-neck-shoulders masks + polyurethane foam cushions), and group B2 (full head-neck-shoulders masks + standard headrests). Positioning was directed by automatic couch motion in OSMS in group A and by laser lights and mask markers in groups B1 and B2. Cone beam computed tomography (CBCT) scans were registered using the bone registration method to obtain setup errors in six directions ( x, y, z, roll, pitch, yaw). PTV expansions were calculated according to the van Herk formula. Results:A total of 288 sets of CBCT registration data were acquired. Among three groups, group A showed the smallest mean setup errors and 3D vector error, which were (0.47±0.33) mm, (0.49±0.31) mm, (0.44±0.31) mm, (0.42±0.32)°, (0.48±0.31)°, (0.42±0.22)°, and (0.90±0.39) mm, respectively. Group A differed significantly from group B1 and group B2 in the errors at all directions ( P < 0.05) except for the yaw direction compared with group B1 ( P > 0.05). Group A had no setup error ≥2 mm in translational directions or ≥2° in rotational directions. Group B1 showed significantly smaller setup errors in the y, z, and yaw directions and 3D vector error than group B2 ( P < 0.05). In group A, PTV expansions in three directions ( x, y, and z) were 1.32, 1.19, and 1.22 mm, respectively, which were smaller than those of the other two groups. Conclusions:In HSRT for patient with brain metastases, compared with full head-neck-shoulders masks combined with laser lights and mask markers, open masks combined with OSMS can significantly improve setup precision in six directions and reduce repeated setup and PTV expansions, which shows promise for clinical application.

Objective:To study the impact of the Varian real-time position management (RPM) respiratory gating system on radiotherapy planning dosimetry.Methods:The radiotherapy plans of 40 cases with thoracic or abdominal tumors were retrospectively selected in this study. The motion phantom for quality control was adopted to generate respiratory gating signals, and the 30%-60% stable phase at the end of expiratory was selected as the respiratory gating window. The dose verification for the abovementioned radiotherapy plans was performed using the Portal Dosimetry (PD) system under RPM respiratory gating mode with the Edge accelerator. Afterwards, dose analysis was performed with different γ passing rate criteria and the distribution characteristics of γ values were analyzed. Finally, the verification results between the non-gating mode and the gating mode were compared.Results:Under the respiratory gating mode, the passing rates of all intensity-modulated radiation therapy/volumetric-modulated arc therapy (IMRT/VMAT) plans with or without flattening filters were over 95.5% by γ criteria of (3%, 3 mm) or (3%, 2 mm) and were over 90% by stricter γ criteria of (2%, 2 mm). All plans met the clinical requirements recommended by the American Association of Physicists in Medicine (AAPM). The passing rates of dose verification under non-gating mode were slightly better than those under respiratory gating mode, and the differences between the two modes were statistically significant (3%/3 mm, Z =-1.45; 3%/2 mm, Z =-2.86; 2%/2 mm, Z =-3.70; 1%/1 mm, Z =-4.52; P<0.05). There was no significant difference in the minimum and maximum values of γ and the share of γ > 1.5 of plan verification result under the two modes. However, the average value and standard deviation of the γ were generally smaller under the non-gating mode. Conclusions:The impact of the introduction of RPM respiratory gating technology on dose is clinically acceptable, and the execution of these plans in this gating mode is safe and reliable.

Objective: To apply GBZ/T298-2017 "Guidelines for occupational health risk assessment of chemicals in the workplace" to conduct an occupational health risk assessment of 2-butoxyethanol exposure in a printing enterprise, in order to protect the laborers' health. Methods: Conducted a worksite survey of occupational health include data collection, site investigation, determination 2-butoxyethanol in workplace air and raw and auxiliary material, determination 2-butoxyacetic acid in urine after shift from May 17 to 24, 2017, using the above results, conducting 2-butoxyethanol occupational health risk assessment. Results: Concentrations of 2-butoxyethanol in the workplace air ranged from 1.2-30.8 mg/m³. Concentrations of 2-butoxyaceticacid in urine ranged from 35.5 mg/L to 563.3 mg/L. The printing shop with the highest concentration of air in the workplace in the enterprise was a medium risk for 2-butoxyethanol occupational health risks, and the binding workshop printer was a low risk for 2-butoxyethanol occupational health risks. The occupational health risk of 2-butoxyethanol in the print shop was medium. Conclusion Occupational health risks of 2-butoxyethanol for companies is medium, which should be included in the evaluation of routine occupational hazards and provide more targeted recommendations based on the action levels.

10.3969/j.issn.1007-3969.2013.04.011