**4. IGABT procedure (Kobe University Hospital)**

#### **4.1. Anesthesia**

To perform more appropriate IGABT, appropriate anesthesia is very important. There are four types of anesthesia and combinations as follows: general anesthesia, lumbar subarachnoid spinal nerve block, sacral epidural block, and intravenous sedation. Intravenous sedation is inadequate to perform appropriate IGABT and therefore should only be performed in patients who cannot safely receive other anesthesia modalities. Lumber subarachnoid spinal nerve block seems to be better than sacral epidural block. However, sacral epidural block may be better for patients receiving anticoagulation therapy. In addition, anesthesia should be performed by an anesthetist for patient safety. Lumber subarachnoid spinal nerve block or sacral epidural block is performed most frequently. In our institution, the first choice for IGABT is a lumbar subarachnoid spinal nerve block. A sacral epidural block is the second choice for patients receiving anticoagulation therapy or those with severe medical complications.

#### **4.2. Flow of IGABT**

Applicator implantation should be performed using transrectal ultrasound. This is important for guidance during dilatation of the cervical canal and tandem implantation. X-ray is also useful. If available in the BT room, CT is very useful to verify the final position of the applicators, and also to perform needle implantation. Moreover, when CT-based planning is performed, the entire BT procedure (implant, imaging, planning, and irradiation) can be done in the same room. Therefore, if an institution is going to initiate IGABT, the most important thing is to place CT in the BT room.

When MRI-based IGABT is performed, patients must be transported to the MRI room. Transfer must be performed as quickly as possible for safety and the MRI protocol must be limited to that necessary for treatment. After acquisition of MR images, treatment planning, and irradiation is performed.

### **4.3. Imaging protocols**

For the acquisition of MR images, a 1.5 or 3.0 T machine is recommended. T2-weighted images (WI) with transverse sections are necessary for treatment planning. Sagittal sections are also important. Diffusion‐weighted images (DWI) are optional but are useful to define GTV. As an example, details of MRI performed at Kobe University Hospital are shown in **Table 1**.


**Table 1.** MR imaging protocol at Kobe University.
