A Comparative Dosimetric Study Of Conventional, Conformal And Intensity-modulated Radiotherapy In Postoperative Irradiation Of Cervical Cancer

Objective The purpose of the study was to evaluate target-volume coverage and organ at risk(OAR)protection achieved with conventional radiotherapy(CRT),three dimensional conformal radiotherapy(3DCRT),and intensity-modulated radiotherapy(IMRT) through dosimetric comparison in patients with cervical cancer underwent radical hysterectomy and pelvic lymphadenectomy.Methods 10 high-risk patients,who had cervical cancer after radical surgery were selected.After The images scaned by CT transferred to treatment planning system to generate CRT,3DCRT和IMRT plans for this study,contouring the clinical target volume(CTV) on the individual axial CT slices of every patient,The CTV was then uniformly expanded by 0.5cm to create the planning target volume(PTV).The small bowel,rectum,bladder,spine cord,bone were outlined for the organ at risk(OAR) evaluation.The plans of CRT(AP/PA),3DCRT(4 fields) and IMRT(7fields) for every patient were desiged by the same physicist.The plans were prescribed to deliver 46 Gy to above 90% of the PTV,Isodose line and dose volume histograms(DVH) were used to evaluate the dose distribution in target-volume and OAR.Results Among IMRT,3DCRT and CRT plans,The coformity index(CI) of IMRT plans were markedly superior than 3DCRT and CRT plans, The coformity index(CI) in the CRT plans were inferior than the 3DCRT plans.At the same prescribed dose of 46Gy,there were no significant differences on PTV (including dmax ,dmean and dmin)dose among IMRT ,3DCRT and CRT(AP/PA)plans(P>0.05). The maximum dose of the small bowl and spine cord in IMRT plans were lower than the CRT and 3DCRT plans(P﹤0.05),The spine cord maximum dose in 3DCRT plans were also lower than CRT plans(P﹤0.001),There were no significant differences on the small bowl maximum dose between the 3DCRT and CRT plans(P>0.05). There were no significant differences on OAR maximum dose (including the bone,rectum and bladder)among IMRT,3DCRT and CRT plans.Comparing with the CRT and 3DCRT plans the IMRT plans significantly spared rectum and bladder at 45 and 40Gy levels,At 30Gy level the volumes in the IMRT and 3DCRT plans were less than the CRT plans.The IMRT and 3DCRT plans notably reduced the volume of the small bowl at 30,40 and 45Gy levels comparing with the CRT plans.There have little spine cord above 40Gy in the IMRT and 3DCRT plans while 30.12% volume of spine cord in the CRT plans were above 40Gy .At 30Gy level the IMRT plans reduced about 43.50% volume of spine cord comparing with the 3DCRT and CRT plans.Conclusions The coformity index(CI) in the 3DCRT plans are superior than the CRT plans.while inferior than the IMRT plans;At high dose levels(≥40Gy) the IMRT and 3DCRT plans can protect the small bowl and spine cord.The radiation volume to organs at risk in 3DCRT and IMRT plans are smaller than the CRT plans at different dose levels.Among three kinds of plans there have least adiation volume to organs at risk in the IMRT plans.so,patients with cervical cancer after radical surgery received IMRT may be potentially diminish the Normal Tissue Complications Probability。...