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Objective To compare the dosimetric differences of four fluence smoothing (FS) levels of the Monaco system in intensity-modulated radiation therapy (IMRT) after rectal cancer surgery, and to provide a reference for FS selection in clinical practice. Methods A total of 15 postoperative patients with rectal cancer admitted in 2020 were selected. Under the same optimal conditions, FS was set to Off, Low, Medium, and High for IMRT planning. The data were analyzed by SPSS 20.0 software. The dosimetric parameters of planning target volume and organs at risk (OARs), the number of Segments, the number of monitor units (MUs), the estimated total delivery time (ETDT), and the gamma pass rate were compared between the four FS levels. Results The four FS levels resulted in clinically acceptable dosimetric parameters of the planning target volume and OARs, and there was no significant difference in dose distribution between FS levels. From FS-Off to FS-High, number of Segments, number of Mus, and ETDT decreased by 15.2%, 11.8%, and 6.7%, respectively, whereas gamma pass rate increased by 1.6%. Conclusion The IMRT plans at four FS levels can meet the clinical requirements. Considering the planning quality and execution efficiency, FS-High is recommended for postoperative IMRT of patients with rectal cancer.
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Objective:To analyze the feasibility of hippocampal-avoidance (HA) prophylactic cranial irradiation (PCI) in small cell lung cancer patients (SCLC)(limited stage) after chemotherapy and thoracic radiation.Methods:From June 2016 to March 2019, 40 eligible SCLC patients were recruited and randomly divided into the routine PCI ( n=22) and hippocampal-avoidance PCI (HA-PCI) groups ( n=18). The HA zone was contoured according to the criteria of RTOG 0933. Volumetric-modulated arc therapy (VMAT) was adopted in the HA-PCI group. After radiotherapy, Hopkins verbal learning test (HVLT) and MRI were performed. Results:The average hippocampus volume was (4.01±1.57) cm 3, the average HA volume was (20.13±4.14) cm 3, HA D 100% was (7.19±0.38) Gy and HA D max was (14.38±1.18) Gy. During HVLT, 1-month-after-PCI vs. before-PCI (trial3, trial4, learning, percent retained), 1-month-after-PCI vs. after-PCI (trial3, learning), HA-PCI cohort showed advantages over PCI in HVLT scores. The average follow-up time was (17.00±8.47) months. Two patients with brain metastases which were out of the HAZ received routine PCI. Conclusions:PCI using VMAT technology to protect hippocampus is feasible in dosimetry. The test results indicate that the protective effect of hippocampus protection on memory is worthy of further promotion in clinical practice.
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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.
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Objective To analyse the memory function and MRI changes in local-advanced nasopharyngeal carcinoma patients before-and after-radiation.Methods Clinical data,dosimetric data,digital span score and MRI of 14 cases with nasopharyngeal carcinom treated in Zhejiang Cancer Hospital from November 2015 to August 2016 were retrospectively analysed.There were 1 case at T2 stage,7 cases at T3 and 6 at T4.They received IMRT or TOMO therapy concurrent with 2 cycles Nedaplatin after 2-3 cycles PF/TP induction chemotherapy.Results The IMRT dosimetric data of 9 cases were available.For hippocampus and temporal lobe,the mean volume was (15.17 ± 2.17) and (95.07 ± 12.26) cm3,respectively,while the mean dose was (1 154.06 ±771.63) and (1 306.61 ±603.69) Gy,and the max dose (3 797.61 ± 1 450.98) and (5 394.17 ± 982.28) Gy,respectively.The equivalent uniform dose (EUD) was (2 233.28 ±872.73) Gy for hippocampus and (3 113.11 ±603.69) Gy for temporal lobe.10 patients received digit span score before-and 3 months after-radiotherapy.The mean score of forward digit span was 8.8 ± 1.8 before radiation and 8.1 ± 1.59 at 3 months after radiation(P ＞ 0.05),while thatof backward digit span decreased from 6.2 ± 1.04 before radiation to 5.3 ± 2.36 at 3 months after radiation (t =3.25,P ＜ 0.05).9 patients' MRI were available.Volume reduction of temporal lobe was observed (t =4.57,P ＜ 0.01) by voxel-based morphometry (VBM).Conclusions Radiation-induced injury to hippocampus and temporal lobe is inevitable in local-advanced nasopharyngeal carcinoma patients.There might be some connection between memory loss and temporal lobe volume atrophy after radiotherapy.Enrollment of larger sample analysis is expected.
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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.