Objective To analyze the radiation doses to the head, body, and tail of the hippocampus in intensity-modulated radiotherapy(IMRT)for nasopharyngeal carcinoma(NPC). Methods Ten NPC patients treated with IMRT were selected,and the head, body, and tail of both hippocampi were delineated on T1-weighted images. The doses to the hippocampus were then analyzed. WAIS-CR speech test results were tested by paired sample t-test. Results The mean doses to left and right hippocampi were 1 147±976 cGy and 1 011±602 cGy, respectively. The mean doses to the head, body, and tail of the left hippocampus were 1 739± 1 317 cGy, 890± 982 cGy, and 547± 688 cGy, respectively(P=0.042);the mean doses to the head,body,and tail of the right hippocampus were 1 691±942 cGy,744±483 cGy,and 531±603 cGy,respectively(P=0.002).The dose to the hippocampus decreased from the head to the tail, and the irradiated volume also decreased as the dose varied. Conclusions The dose to hippocampus decreases from the head to the tail in NPC patients treated with IMRT,which is worthy of attention.

Objective To analyze the exposed dose of hippocampus(HC)of T3,T4nasopharyngeal carcinoma patients treated with intensity modulated radiotherapy(IMRT). Methods The bilateral HCs were delineated and were divided into head(HH),body(HB)and tail(HT)for 62 nasopharyngeal carcinoma patients treated with IMRT.The dose parameters of HC were then analyzed. Results The mean dose of left and right HC was(1 127±704)cGy,(1 173±762)cGy. The mean dose of left HH,HB and HT was(1 732±1029)cGy,(820±632)cGy,(423±366)cGy(P=0.000);while the mean dose of right HH, HB and HT was(1 985±1101)cGy,(837±531)cGy,(432±343)cGy(P=0.000).The exposed dose and the volume exposed in different dose of HH were obviously higher than those of HB and HT.The dose parameters of HH,HB and HT decreased in turn. The involvement of sphenoid sinus,ethmoid sinus and cavernous sinus correlated with high exposed dose of HC. Conclusions The exposed dose of HH,HB and HT was different in nasopharyngeal carcinoma patients treated with IMRT.The exposed dose of HH was the highest,which should be emphasized especially. The involvement of sphenoid sinus,ethmoid sinus and cavernous sinus suggest high exposed dose of HC.