A Preliminary Study On The Protection Of Bone Marrow In Craniospinal Irradiation

Objective:Analyze the relationship between the dose volume of bone marrow and acute hematologic toxicity in craniospinal irradiation(CSI),and explore the dosimetric differences in bone marrow between helical tomotherapy(HT)and volumetric modulated arc therapy(VMAT)preliminarily.Methods:Helical tomotherapy treatment plans of twenty patients treated with CSI were collected from the First Affiliated Hospital of Kumming Medical University from December 2011 to December 2015 and transferred back to MIM.We delineated the skull,mandible,clavicle,sternum,scapula,ribs,vertebrae,pelvis successively in the CT and then read the V2?V5?V10?V15?V20?V25?V30?V35?Dmax?Dmean of each aforementioned bones?Body and total bone(add each aforementioned bones together)from DVH,subsequently analyzed the correlation between those indexes above and grade?2 hematologic toxicity.After that we chose 6 patients'images and transferred them to Monaco TPS and completed volumetric modulated arc therapy plans,then compared the dosimetric difference of those indexes above between helical tomotherapy and volumetric modulated arc therapy plans.Results:1?In our study,there was a positive correlation between grade?2 leukopenia and indices including V25 of pelvis,maximum dose of vertebral(r=0.564?0.466,P=0.010?0.038);the V20 of pelvis showed a positive correlation with grade?2 thrombocytopenia(r=0.460,P=0.041);and a positive correlation was found between grade?2 neutropenia and V10 of vertebrae(r=0.471,P=0.036).2?There was a positive correlation between grade?2 leukopenia and V5 of total bones(r=0.449,P=0.025).3?There was a positive correlation between grade?2 leukopenia and V10?V15?V20?V25?Dmean of Body(r=0.499?0.607?0.520?0.488?0.520,P=0.025?0.005?0.019?0.029?0.019).4?There was no dosimetric difference of dose volume of vertebral and pelvis between helical tomotherapy and volumetric modulated arc therapy plans,P>0.05.Conclusions:1?There was a positive correlation between grade?2 leukopenia and indices including maximum dose of vertebral and V25 of pelvis,the V20 of pelvis showed a positive correlation with grade?2 thrombocytopenia;A positive correlation was found between grade?2 neutropenia and V10 of vertebrae.2?There was a positive correlation between grade?2 leukopenia and V5 of total bone,and dose volume of total bone showed no correlation with grade?2 thrombocytopenia/grade?2 neutropenia/grade?2 anemia;and there was a positive correlation between grade?2 leukopenia and V10?V15?V20?V25?Dmean of Body,while dose volume of Body showed no correlation with grade?2 thrombocytopenia/grade?2 neutropenia/grade?2 anemia.3?The indices of vertebral as well as pelvis between volumetric modulated arc therapy plans and helical tomotherapy pains showed no significant differences.