ABSTRACT
Objective To measure and analyze the neutron dose equivalent rate produced by an IORT accelerator with 9 and 12 MeV electron energyies,and compare them with those from a Siemens Primus linear accelerator with the same electron energy,in order to provide data reference for the risk of secondary cancer induced by radiotherapy.Methods Using the neutron detector LB6411,the neutron dose equivalent rates produced by the IORT accelerator of 9 and 12 MeV were measured on some key locations,such as the head of the accelerator,cylinder bottom,patient plane with electron energies 9 and 12 MeV.The similar measurements were also performed on the same locations on a Siemens conventional accelerator.The data were collected and analyzed and the result wer compared between the two accelerators.Results Neutron dose equivalent rates from the IORT accelerator with 9 MeV energy were (51.8±3.1),(45.5 ±1.5),(70.5 ±4.9) and (68.2±3.3) μ Sv/h near the head of the accelerator,cylinder bottom,patient plane,with 5.9％,5.4％,17.8％ and 21.5％ lower than at 12 MeV,respectively.The dose equivalent rates at the similar locations from the Siemens Primus accelerator were (277.3 ±1.2),(285.1 ±1.6),(185.1 ±1.8) and (182.8 ±2.4) μSv/h at 9 MeV,with 48.8％,47.6％,48.7％,52.2％ lower than those at 12 MeV,respectively.At the energy of 12MeV,the neutron equivalent dose rate from the IORT was lower by a factor of about 10 than for Siemens Primus accelerator.Conclusions The neutron dose equivalent rates generaged by both the IORT and the Siemens Primus are higher at 12 MeV than at 9 MeV,which would lead to an increased risk of secondary cancer to patients.The traditional medical accelerator produces much higher neutron dose equivalent rates than the intraoperative electron accelerator,for which the appropriate shielding should be takn.
ABSTRACT
The latest progress of modern radiotherapy techniques in the management of breast cancer after breast-conserving surgery was introduced first.Then the clinical effect and the adverse effect of these advanced techniques were analyzed.Finally,in order to provide an up-to-date evidence based data on the role of modern radiotherapy techniques in the management of breast cancer,the importance of how to choose appropriate patients for these advanced techniques was discussed.
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Background and purpose: Currently, intraoperative radiation therapy (IORT) has become the adjuvant therapy of cancer. The study was to establish the daily quality assurance (QA) program and analyze dosimetric characteristics’ long-term stability for mobile IORT accelerator. Methods:The QA program of this study included two parts:safety and functionality and energy and output. The two years’ QA datasets were acquired and analyzed to investigate the stability of energy and output. Results:All safety and functionality tests passed on a daily basis. The energy index was (0.666±0.015)mm, (0.839±0.009)mm, (0.781±0.010)mm, (0.724±0.009)mm and the output dose error was (0.511 ± 0.671)%, (0.278 ± 0.516)%, (0.368 ± 0.532)%, (0.382 ± 0.912)%for all energy, respectively. There was no signiifcant time trend in the dosimetric characteristics. Conclusion:The daily QA program is suitable for mobile IORT accelerator. The long-term stability is acceptable for IORT in clinical use.
ABSTRACT
PURPOSE: Pancreatic cancer is a devastating disease and the complete resection is difficult due to its the aggressive histologic behavior. Among the possible treatments for the unresectable pancreatic cancer, intraoperative radiation therapy (IORT) has the several advantages. But the impacts of the IORT on survival and local control are not clear. We analyzed the effects of the IORT on pain control, survival duration and local control in patients with unresectable pancreatic cancer. METHODS: We reviewed 6 years of the medical records of 94 patients who had undergone operations involving the pancreatic adenocarcinoma (33 patient IORTs, 39 palliative surgerys only and 22 curative resections involving a curative resection). The clinicopathologic factors and outcomes of the 33 patients treated with the IORT were compared with those of the palliative surgery groups. RESULTS: The age and sex distribution and tumor stage were same for the two groups. The average tumor size in the IORT group was larger than those of the palliative surgery group. The preoperative serum CA19-9 level in the IORT group was higher than the other group. The most common reason for unresectability in the IORT group was local invasion to the adjacent organs including of the great vessels. On the contrary, distant metastasis was a more common cause unresectability in the palliative surgery group. The postoperative complications and operative times were similar in both groups. Pain relief after treatment was observed in 12 cases of the 26 patients in the IORT group, and 5 of 29 patients in the palliative surgery group (P<0.05). The cases of minor and partial remission were more common in the IORT group than the palliative surgery group. However, the survival rate of the IORT group was no better than the palliative surgery group. CONCLUSION: This study suggests that IORT may have an important palliative role especially in ameliorating visceral pain in patients with unresectable pancreatic cancer. However, IORT appears to have no significant effect on overall survival.