ABSTRACT
Objective:The purpose of current study was to evaluate the interplay effects in intensity-modulated proton therapy (IMPT) for lung cancer and compare the results of different Iso-energy layer repainting techniques in the mitigation of interplay effects.Methods:Eight patients with lung cancer who underwent 4DCT were retrospectively selected. A robust CTV-based IMPT plan was generated for each based on commercial TPS, considering patient setup errors ±5 mm, range uncertainties ±3.5%, and CTV time structure motion in 4DCT image. Monte Carlo dose engines were used for all IMPT plans in the final dose calculation. The 4D static dose (4DSD) and 4D dynamic dose (4DDD) were calculated using a hybrid deformable algorithm and simulated proton delivery system for interplay effects. An index[ΔI(ROI, DVH)] was developed to quantitatively evaluate the interplay effects. We applied Iso-energy layer repainting techniques with different numbers of repainting (3, 4, 5, 6, 7) to the robust IMPT plans and evaluated the difference in the mitigation of interplay effects based on the ΔI(ROI, DVH) index.Results:Due to interplay effects, the mean values of target coverage, conformity and homogeneity index reduced by 13.7%, 12.7% and 24.6%, respectively. The mean values of lung V 5Gy and V 20Gy improved by 0.8%, 3.4% and 2.6%. Compared to the IMPT plans without layer repainting, Multiple iso-energy layers repainting techniques improved the mean values of CTV coverage by 4.5%, 3.8%, 3.8%, 3.6% and 5.7%, respectively. The average values of lung V 20Gy reduced by 1.5%, 1.8%, 1.7%, 1.6% and 1.9%, respectively. Conclusions:In the robust CTV-based IMPT plans, the interplay effects degraded the target dose distribution but were mitigated using iso-energy layer repainting techniques. We recommended to use the layer repainting technique according to the characteristics of the patient.
ABSTRACT
Objective:To analyze the clinical features and imaging findings of chest computed tomography (CT) of patients with corona virus disease 2019 (COVID-19), and to provide imaging guidance for early diagnosis and clinical treatment.Methods:A total of 74 patients diagnosed with positive nucleic acid test of nasopharyngeal swab were retrospectively collected from January 23 to February 22, 2020 in the inpatient department of Rui′an People′s Hospital. Their clinical features were analyzed in combination with CT image characteristics.Results:Of the 74 patients, 62 (83.8%) had fever, 59 had abnormalities in CT examinations and 15 patients had no imaging abnormalities. The average interval from onset to CT examination was 4.6 days. Among 59 patients, 58 cases (98.3%) were mainly peripherally distributed, 53 cases (91.4%) had multiple lesions and five cases (8.6%) had single nodules. The main manifestation was ground glass opacities (45 cases, 76.3%). The lesions were mainly distributed in the middle and lower lobe of the lungs, accounting for 76.3% (45 cases). Air bronchogram was shown in 21 cases (35.6%), and reversed halo sign was shown in 10 cases (16.9%). Other rare abnormalities were small cavities in three cases (5.1%), tree-in-bud pattern in one case (1.7%). Intrathoracic lymph node enlargement was found in two cases (3.4%) by re-examination.Conclusion:The CT examination characteristics of COVID-19 patients could play an important role for early diagnosis and follow-up.