8.3.2 Partial Mammary Gland Irradiation Technique
The pathological analysis of breast conserving patients after segmental resection showed that only 9%of the patients had tumor residue outside the residual cavity of segmental resection.Therefore，PBI needs to irradiate the tumor bed and the area of 1-2cm outside the tumor bed.PBI can be realized by the following methods：multi-tube tissue implantation brachytherapy，single-tube balloon brachytherapy（Mammosite），three-dimensional conformal external radiotherapy and intraoperative radiotherapy.
（1）Interorganizational implantation
Intertissue implantation is a kind of multi-tube brachytherapy.One to several rows of catheterization can be performed during or after operation in the tumor bed and the area of 1-2cm.Then brachytherapy was performed according to the treatment plan.Radiotherapy can be irradiated with low dose rate（LDR）or high dose rate（HDR）.The prescription dose of low dose rate irradiation was 45-50Gy，4-5 day，and that of high dose rate irradiation was 32Gy/（8 times.4 days）or 34Gy/（10 times.5 days），twice a day.There are long follow-up results of PBI with intertissue implantation and brachytherapy：appropriate selection of patients，The radiotherapy side effects were small and the local recurrence rate was 1%～4.4%.However，the operation and treatment plan of interorganizational implantation is complex，which requires formal training and a long learning process，so it is difficult to be widely used.(https://www.daowen.com)
（2）MammoSite
Mammosite is a single tube balloon brachytherapy device approved by the Food and Drug Administration，also known as intracavitary radiotherapy.Before the incision was closed or under the guidance of B-ultrasound，the balloon was placed in the residual cavity of breast tumor through a small scar incision or lateral incision.The advantage of balloon implantation after operation is that it has definite pathological diagnosis and reduces the rate of balloon relocation caused by unsuitable Mammosite for pathological reasons.When making the treatment plan，normal saline is injected into the balloon to make the shape of the balloon suitable for the residual cavity of the operation.The prescription dose was given to 1cm outside the surface of the balloon，most of which were 34Gy/（10 times for 5 days），high dose rate irradiation.At the time of treatment，radioactive sources can be used to stay at a single point or multiple points.The results of 1403 breast cancer patients treated with Mammosite reported by the American Surgical Association showed that 9%of the patients had good breast cosmetic effect 12 months after radiotherapy［14］.The early cosmetic effect was related to the minimum distance between balloon surface and breast skin.The cosmetic effect of patients with distance≥7mm was better than that of patients with＜7mm.8.1%of the patients had breast infection.With the accumulation of experience.The incidence of infection is getting lower and lower.3.4%of the patients report 3 weeks after radiotherapy existing radioactive memories of the skin.The 5-year follow-up results showed that the recurrence rate of intrabreast tumor was 2.9%.