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Objective To analyze the dosimetric and delivery efficiency differences between IMRT plans based on Halcyon and Trilogy Accelerator for left side breast cancer.Methods A total of 10 patients with left side breast cancer based on the Trilogy platform were retrospectively analyzed.For each patient,plan based on Halcyon was redesigned using Eclipse Version 15.1 TPS.In order to evaluate plan quality,dose coverage of target and dose to organs at risk,monitor unit efficiency,segment size and delivery time were compared.Results Halcyon treatment platform could meet the clinical objective.Dose distribution of the target volume had no significant difference with the Trilogy plans (P＞0.05).Volumes receiving 10 Gy,20 Gy and D of the left lung were significantly reduced(Z=-2.22--1.78,P＜0.05).V5 of heart for Halcyon and Trilogy was(27.80±7.66)％ and (23.18±8.19)％,respectively(Z=-0.71,P＜0.05),while D was (7.03± 1.8)Gy and(7.11±2.40)Gy,respectively(P＞0.05).Halcyon increased the monitor unit from 1 526.2±227.7 by Trilogy to 1 770.5±383.9(Z=-0.71,P＜0.05),but decreased the delivery time from (12.38± 1.49) min by Trilogy to (3.01 ±0.28) min (Z =-3.42,P＜ 0.05).Conclusion Halcyon treatment platform can meet the clinical requirements,reduce dose to normal tissue with high delivery efficiency.
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Objective To compare the dosimetric and delivery efficiency between intensity-modulated radiation therapy (IMRT) plans based on Halcyon and Trilogy accelerator.Methods Clinical data of 12 patients with cervical cancer receiving Trilogy platform-based IMRT were retrospectively analyzed.The target area and organ at risk were introduced into the Eclipse version 15.1 TPS.The Halcyon-based IMRT was re-designed.The dose coverage of target area and organs at risk,monitor unit (MU) efficiency,delivery time and segment area and the differences between the proximal and distal segment area were statistically compared between two IMRT plans.Results The Halcyon treatment platform could meet the clinical objectives.Dose distribution of the target area was similar to that of the Trilogy plan (P＞O.05).The volumes in the bladder and rectum receiving 30 Gy and the volumes in the left femoral head receiving 20 Gy of Halcyon plan and the mean dose (D) of bladder,rectum and left femoral head were significantly lower compared with those of the Trilogy plan (P=0.001-0.043).The MUs of the Halcyon plan was 2 316.7± 209.7,significantly higher than 1 692.5± 259.5 of the Trilogy plan (P=0.000).The delivery time significantly differed between the Halcyon [(3.01±0.28) min] and Trilogy [(12.38± 1.49) min] (P=0.000).The average segment area of Halcyon plan for proximal and distal MLC was (43.7±32.5) cm2 and (28.8±25.4) cm2,the average segment area of Trilogy plan was (25.7±16.8) cm2,the ratio of the proximal and distal segment area was 1.73±0.43,ranging from 0.71 to 6.28.Conclusions Halcyon treatment platform can meet the clinical requirements and reduce the dosage coverage of normal tissues with better delivery efficiency.The ratio of proximal and distal segment areas should be considered during the plan design.
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Objective To introduce a finger leaf design that is applied to dual layer MLCs.Methods An optimization model was firstly constructed to describe the problem of determining leaf end shapes,and the corresponding problems were then solved by the simplex search method or the simulated annealing technique.Optimal parameters for arc shapes of leaf end projections were obtained,and a comparison was done between optimized MLCs and conventional MLCs in terms of field conformity.The optimization process was based on 634 target fields selected from the patient data base of a treatment planning system.Areas of these fields ranged from 20.0 to 602.7 cm with a mean and its standard deviation of (125.7 ±0.0) cm~2.Results The optimized leaf end shapes projected to the isocenter plane were semicircles.With the finger leaf design,the total area of discrepancy regions between MLC fields and target fields was reduced by 32.3% .Conclusions The finger leaf design improves the conformity of the MLC shaped fields to the desired target fields.