Preliminary results of the exposed dose of head, body and tail of the hippocampus in nasopharyngeal carcinoma patients treated with intensity modulated radiotherapy

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 1147 ± 976 cGy and 1011 ± 602 cGy, respectively. The mean doses to the head, body, and tail of the left hippocampus were 1739 ± 1317 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 1691 ± 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. (authors)