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Objective:To evaluate whether the decrease in peripheral blood monocyte count was a potential predictor for neutropenia in patients with nasopharyngeal carcinoma and cervical cancer.Methods:The medical records of 95 patients with nasopharyngeal carcinoma and cervical carcinoma who received intensity-modulated radiation therapy (IMRT) combined with paclitaxel liposomes and platinum (TP) synchronous chemotherapy and presented with neutropenia in the Second Affiliated Hospital of Soochow University from January 2017 to December 2018 were retrospectively analyzed. Paired sample t-test was used to assess whether the number of days when the monocytes initially dropped/decreased to lowest level/eventually increased to normal value was significantly less than those of the neutrophils. In addition, the chi-square test was performed to determine the correlation between the degree of reduction in the absolute neutrophil count (ANC) and baseline absolute monocyte count (AMC). Results:The change trend of AMC was consistent with that of ANC in the two cycles of concurrent chemotherapy. The number of days when AMC initially decreased/decreased to the lowest level/finally increased to normal value was significantly less than that of ANC (4 d vs. 6 d, 4 d vs. 10 d, P<0.001; 5 d vs. 6 d, 6 d vs. 9 d, 7 d vs. 12 d, P<0.001). However, no correlation was found between the baseline level of monocytes and the degree of subsequent neutropenia [(AMC<0.4×10 9) vs.( AMC≥0.4×10 9)=32 vs. 63, P=0.172]. Conclusions:Decreased monocyte count is an important potential predictor for neutropenia and a significant indicator for guiding the next monitoring of neutrophil count and treatment with granulocyte colony-stimulating factor.
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Objective:To explore the method of improving the accuracy of dose calculation of treatment plan in radiotherapy for patients with metal implants.Methods:A CT simulator with metal artifact reduction technique (MAR) was utilized to scan the CIRS intensity-modulated phantom with metal rods and 8 patients with steel nails implanted in the centrum for radiotherapy. Radiotherapy plans were designed using conventional CT images, MAR images and density-filled images. The dose calculation errors between single field and intensity-modulated radiotherapy (IMRT) plan were compared. The effect of mental implants and their artifacts on the irradiation dose of IMRT plan was evaluated.Results:In the conventional CT images of the phantom, when the incident path of the field failed to pass through the metal region, the dose calculation error for a single field was 3.85%, and the range of dose error for the field was 4.46%-74.11% when passing through the metal region. IMRT planning errors might exceed the clinically acceptable range when the incident path of the field passed through the metal region, and the errors tended to increase with the increase of dose weight of this field. After processing the images with density filling and artifact reduction techniques, the errors of the single field were 1.23% and 0.89%-4.73%, respectively, and the dose error of IMRT was 1.84%. The error of IMRT plan was 1.88% if density filling technique alone was employed to process the metal region. Due to the influence of metal implants and their artifacts, the minimum dose, average dose and prescription dose coverage actually received in the tumor target area were lower than IMRT plan results based on conventional CT images. The dosimetric difference of organs at risk was not statistically significant.Conclusions:In the radiotherapy plan based on conventional CT images, there may be a large dose calculation error when the incident path of field passes through the metal region. If the metal material is known, density filling of the metal region in the planning system can effectively improve the accuracy of dose calculation. Metal artifact reduction technique can significantly improve the image quality and further reduce dose calculation error, which should be a routine technique for CT machines equipped with this function to perform simulated localization of patients with metal implants.
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Objective To reduce the risk of radiation-induced cardiac injury in patients with left breast cancer after breast-conserving surgery by multileaf collimator (MLC) shielding technique.Methods A total of 18 patients with left breast cancer after breast conserving surgery were selected to obtain 3DCT and 4DCT images at free breathing state.The target area was identified on the 3DCT image by registration with 4DCT images and to develop a hybrid intensity-modulated treatment plan (H_IMRT) and a heart sparing hybrid intensity-modulated treatment plan (HSH_IMRT) to introduce MLC shielding technology to reduce the cardiac exposure dose,and to perform dosimetry verification of the treatment plan by using the Compass verification system.The prescription dose was 50 Gy in 25 fractions.The dosimetry parameters of the target area and the organs at risk were compared between the two treatment plans and the dose verification result.Results The result of the treatment plan showed that compared with H_IMRT,the dose uniformity of the target area of HSH_IMRT was better,and the difference of conformability was not statistically significant (P＞0.05).The mean dose of the whole heart decreased by 23.67％ (t =13.693,P＜0.05) compared with the former.Dmax and D of other substructures of the heart were lower than the former.The result of dose verification showed that there was no statistically significant difference in uniformity and conformity between the two planned target doses (P＞ 0.05).The mean dose of the whole heart of HSH_IMRT was 24.88％ (t =13.782,P＜0.05) lower than that of H_IMRT,and except for the left ventricle and right ventricle,the Dmax of other heart substructures and D of all heart substructures decreased.Both the planned and the dose verification result showed that the V20 and the D of the affected lung were lower in HSH_IMRT.Conclusions Reasonable introduction of MLC shielding technology in H_IMRT can reduce the exposure dose of cardiac and further reduce the risk of radiation damage in heart.