Dosimetry Study Of Left Breast Irradiation With Supine Technique

Objective: To study enter skin dose (ESD), lung dose and the dose of heart coronary left anterior descending coronary artery region (LAD), as well as dose changed when protection of contralateral breast in intensity modulated radiation therapy target volume outlined,when the left breast radiotherapy in supine position of the different techniques ;for preparation of breast cancer prone position radiotherapy dosimetry study.Methods: (1) The female breast phantom for conventional simulation / CT simulation after scanning through the planning system to develop breast of conventional radiation therapy (tangent file) program, MLC-IMRT plans and tomo-modulated treatment plan (NOMOS system) ; TLD were placed in the original experiment to determine the site of interest (treatment / non-therapeutic side of the breast phantom surface, heart LAD and treatment side and the contralateral lung), respectively, using three different simulation of radiotherapy treatment technology conditions of irradiation, after irradiation to collect TLD measurement components, which investigate the effects of different irradiation techniques arising in various parts of the physical dose; (2) the collection of clinical patients with breast cancer after the implementation of conventional radiation therapy, MLC-IMRT and NOMOS tomo-modulated radiation therapy of the five cases of female patients, for a total of 15 cases, using TLD measurements enter skin dose (ESD); (3). the use of phantom image data in the PLATO planning system and CORVUS3.0 system, comparing two different forms of IMRT to protect against contralateral breast and observing contralateral breast, heart, treatment side and the contralateral lung of the impact of the average dose.Results: (1) Chengdu dose Analog left breast phantom measured incident radiation skin dose and the measured data in the patient results are as follows:①CRT average ESD in left breast was 85.9cGy±4.1 cGy and 70.6 cGy±11.8 cGy, respectively, for the prescription dose of 42.9%±2.1% and 35.3%±5.9%; contralateral breast average ESD was 7.2cGy±2.6cGy and 6.8cGy±1.7 cGy, respectively, for the prescription dose of 3.6%±1.3 % and 3.4%±0.9%;②M-IMRT average ESD in left breast was 118.6cGy±10.6 cGy and 129.5cGy±17.8 cGy, respectively, for the prescription dose of 59.3%±5.3% and 64.8%±8.9%; contralateral breast average ESD was 15.1cGy±11.8 cGy and 13.5 cGy±8.4cGy, separately for the prescription dose of 7.6%±0.9% and 6.8%±5.9%;③N-IMRT average ESD in left breast was 115.4cGy±15.2 cGy and 107.9cGy±14.4 cGy, respectively, for the prescription dose of 57.7%±7.6% and 53.9%±7.2%; contralateral breast average ESD was 17.6cGy±5.6cGy and 17.0cGy±7.2cGy, for the prescription dose of 8.8%±2.8% and 8.5%±3.6%; phantom and clinical test results have shown that IMRT than CRT increased incidence of ESD (p <0.05), and ESD between two different forms IMRT was no significant difference (p>0.05); non-therapeutic regional dose of ESD with the distance from the inner edge side of the left breast increases rapidly falling, (2) when Chengdu dose phantom simulation left breast radiotherapy in supine position ,the maximum dose points of leaf lung are front side of the mid plane of leaf lung, CRT> M-IMRT> N-IMRT, respectively 121.1cGy, 98.8cGy and 60.0cGy, respectively, for the prescription dose of 60.5%, 49.4% and 30.0% ; contralateral lung dose was lower, but N-IMRT in the contralateral lung in the lower rear of the remaining points at relatively high doses; (3) when Chengdu dose phantom simulation left breast radiotherapy in supine position, LAD points dose separately 43.8cGy, 28.6cGy and 32.7cGy in CRT, M-IMRT and N-IMRT, separately for the prescription dose of 21.9%, 14.3% and 16.4%; (4) when contralateral breast as a organ in crisis, at PLATO planning system ( M-IMRT) and CORVUS3.0 planning system (N-IMRT), contralateral breast radiation average dose decrease was 35.1% and 37.5%; and other normal tissues dose, such as the heart, the treatment side and the contralateral lung ,had no significant changes.Conclusions: (1) IMRT technology enhance the bilateral breast ESD; (2) when left breast radiotherapy, the leading edge of lung dose and LAD dose of CRT is higher than the dose of IMRT; contralateral lung low radiation doses in CRT and M-IMRT; (3) to protect contralateral breast in IMRT treatment planning system can reduce the average radiation dose.