ABSTRACT
ObjectiveTo study the feasibility of RapidArc (RA) associated with active breath coordinator (ABC)for hepatocelluar carcinoma (HCC)radiotherapy comparing of three-dimensional conformal radiotherapy (3DCRT),intensity modulated radiotherapy (IMRT),RA treatment plans in different breath status.Methods12 HCC cases were selected.Three series CT scanning were completed in Free Breathing (FB),End Inspiration Hold (EIH) and End Expiration Hold (EEH) associated with ABC device.3DCRT,IMRT and RA (three 135° arcs) treatment plans were respectively designed on planning target volume (PTV) in different breath status.The dosimetric differences among 3 DCRT,IMRT and RA,among RA plans under different breath status were compared.ResultsThe PTV in FB was larger than in EEHand EIH (160.8 cm3,89.5 cm3,83.1 cm3,F=6.63,P=0.004). The conformity index and homogeneity index of RA plans were better than IMRT and 3DCRT ( 0.92,0.90,0.77,F =72.55,P =0.000 ;0.90,0.89,0.84,F =125.49,P =0.000 ) ;the V20,V30,V40 of normal liver in 3DCRT were higher than IMRT and RA (24％,20％,19％,F=3.56,P =0.032;13％,10％,10％,F=5.74,P =0.004;8％,5％,6％,F =3.72,P =0.027).The normal liver mean dose,V10,V20,V30,V40 of RA plans in FB were higher than in EEH and EIH ( 13.46 Gy,10.25 Gy,9.48 Gy,F =3.627,P =0.038 ;46％,35％,32％,F =2.96,P=0.066;24％,16％,16％,F=3.69,P=0.036;13％,8％,8％,F=4.28,P=0.022;8％,5％,5％,F =2.39,P =0.108 ).The duodenum D5 cm3 of RA in EEH was lower than in FB and EIH (8.78 Gy,19.35 Gy and 11.67 Gy,F =1.56,P =0.224 ).The mean monitor units for 3 DCRT,IMRT,RA was 254.06 MU,626.33 MU and 550.28 MU ( F =147.35,P =0.000 ),while the mean treatment time was 135 s,540 s and 130 s respectively (F =62.83,P =0.000).ConclusionsThe RapidArc applying three 135°arcs with ABC in HCC radiotherapy can achieve better PTV coverage than IMRT with fewer monitor units,shorter treatment time and sparing more normal liver.
ABSTRACT
Objective To compare the dosimetric difference of RapidArc and fixed gantry angle dynamic IMRT (dIMRT) for loco-regionally advanced nasopharyngeal carcinoma.Methods Ten previously treated patients with loco-regionally advanced nasopharyngeal carcinoma were replanned with RapidArc and dIMRT, respectively.The prescription dose was GTV 70 Gy/33 f and PTV 60 Gy/33 f.All plans met the requirement:95% of PTV was covered by 60 Gy.Dose-volume histogram data, isodose distribution, monitor units,and treatment time were compared.Results Dose distribution has no significant difference between the two techniques.RapidArc reduced the dose of the brainstem, mandible, and other normal tissues compared with dIMRT.Mean monitor units were 589.5 and 1381.0 for RapidArc and dIMRT (reduced by 57% relatively).Mean treatment time was 2.33 min and 7.82 min for RapidArc and dIMRT (reduced by 70% relatively).Conclusions Compared with dIMRT, RapidArc achieves equal target coverage and OAR sparing while using fewer monitor units and less time during radiotherapy for patient with loco-regionally advanced nasopharyngeal carcinoma.