Session Item

The prostate in the pelvis is severely affected by the surrounding internal organs, the rectum, bladder, etc., and is particularly affected by intestinal gas.
It is necessary to be able to take into account the movement according to the change of internal organs or the amount of gas.  For this purpose, IGRT using OBI or CBCT treats the prostate, The prostate is difficult to treat properly because of the large change of motion due to intestinal gas. Therefore, it is necessary to treat with MRI guided technique which can see the soft tissues well.
This study is to evaluate the appropriateness of treatment for each organ according to planned doses based on real - time imaging with MRI in the treatment of prostate.
We evaluate the proper treatment of organs in accordance with the treatment plan according to the treatment plan based on real-time MRI imaging using the Viewray MRIdian System (Viewray, Viewray Inc, OH.USA).

This study was a retrospective study that analyzed a total of 630 data from 18 patients who were treated from March to September, 2018.
The data were analyzed for age, age and treatment time.  In addition, to determine the effect on bowel movements, the subjects who are enema and those who do not enema are divided into two groups.
The treatment group was divided into 36.25 Gy, 5fx, 13 people and 70Gy, 28fx, 5 people.  The 36.25 Gy group was injected with a prescription drug each time, and the contents of the rectum before treatment were evacuated and the 70 Gy group was excreted only.

The 36.25 Gy group mean age was 74.9 years, treatment time was 555.1 seconds, dose was 100.7%, standard deviation was 2.7%.  The 70 Gy group average was 72.4 years old, the treatment time was 229.3 seconds, the dose was 100.3%, and the standard deviation was 1.4%. Errors were observed in Bowel 31%, Bladder 13.1% Rectum 15.9% in one treatment.
p value was Dmean, Dmax, age, treatment time was less than 0.01, and the difference between the two groups was reliable.
 The mean dose between the two groups was 0.9∼0.3%. The most significant difference was 0.9% in Rectum. CTV and Bowel were the sites with the minimum dose difference. Rectum was 0.7% where the standard deviation was high.
Especially, the standard deviations of Mean, Max, and Min dose were 4.7%, 4.7%, and 13.6%,  respectively, even though Adaptive RT was performed by MR-IGRT for one treatment.

IGRT enables highly accurate treatment at the treatment site. However, this treatment only considers anatomical position based on bone density. so it can cause side effects due to soft tissue movement.
It gives large doses to the rectum and small intestine or insufficient dose to the target area.Therefore Real-time MR images should be obtained to check for errors to reduce side effects. In addition, this study showed that treatment with enema every time can help to reduce dose to rectum and small intestine. Therefore, if possible, it may be appropriate to minimize bowel movements through the enema to reduce side effects during treatment.