About Proton Beam Therapy

The stages of pre-treatment preparation

Below is a general overview of the stages of proton therapy. It is necessary to ensure that treatment is suited to each individual patient, by devising treatment plans and creating immobilization and treatment devices to help you to remain still during treatment and ensure that the proton beam is administered accurately.

01. Initial visit and medical examination


A doctor carefully explains the medical condition and treatment methods so the patient can fully understand them.

We ascertain the condition of the tumor and your general condition by performing a physical examination and checking the referral and the medical image data which you bring to the first visit, and consider whether or not proton therapy is appropriate for you. On the day of your first visit, we arrange for medical examinations and tests as necessary. Doctors will clearly explain your medical condition and the treatment methods, and perform an evaluation in a comprehensive manner by also conducting interviews about your situation. Furthermore, depending on your medical condition, there are cases in which proton therapy is not recommended.

02. About seven to ten days of preparations before treatment is started

If proton therapy is to be performed, we start to prepare for it. You will be asked to visit about 2 times to help us during the preparation period.
2-1 Creating immobilization device

An immobilization device is custom made to fit the shape of your body, in order to help you to remain still during treatment and ensure that the proton beam is always targeting the correct area. It takes only 1 or 2 minutes to create such an immobilization device.

2-2 CT imaging of your body in the immobilization device

When the immobilization device is completed, you will fitted with the actual device, and we will take CT images to be used for planning therapy.


Preparation period before the start of treatment
2-3-1 Development of a treatment plan

The attending doctor and medical physicists will use a computer to calculate the suitable angle, depth, dose, and frequency at which to deliver a proton beam according to your medical condition, and make a concrete and detailed treatment plan.

2-3-2 Review of the treatment plan at a meeting

After a treatment plan has been developed, the attending doctor and other doctors, medical physicists, radiological technicians, and nurses hold a meeting and together discuss and check whether the treatment plan is the right one. In addition, information is shared on changes in the plans for patients undergoing treatment, as well as the medical conditions of new patients. This meeting is held every morning.



We hold a meeting every morning. The plans and courses of treatment for every patient are checked and shared by all doctors.


The attending doctor and medical physicists will develop a treatment plan based on the condition of the tumor. They determine the irradiation dose, frequency, etc. in detail.

2-4 Creating treatment devices

In order to ensure that a proton beam is accurately irradiated only to the target tumor, we make two treatment devices -called a collimator and a bolus- each with the same shape as your tumor in order to ensure that the shape and depth of a proton beam matches the tumor.

2-5 Measuring the proton beam dose


In the irradiation control room, radiological technicians adjust the proton beam dose and check whether it is irradiated normally.

We set-up the collimator and bolus in the dedicated equipment, emit a proton beam and measure its dose and distribution. We then confirm whether or not the dose measured matches the treatment plan, and move on to the actual therapy after thorough preparations.


To start of proton therapy treatment

During and after treatment

Once all of the preparatory stages have been completed, your treatment will begin. During the treatment period, you visit the Proton Beam Therapy Center to receive treatment every weekday.*1 The number of times and the period for which treatment is administered vary according to the medical condition of the patient.

*1Except for maintenance days and public holidays.

Checking the correct positioning of the proton-beam X-ray imaging

We take X-ray images of you in two directions to check the positioning of the proton-beam and ensure that it targets the tumor exactly.



Setting two important devices in the emission port to improve the precision of proton beam emission

We install two devices on the tip of the emission port: a collimator (right), which shapes the contours of the proton beam to fit the tumor and a bolus (left), which sets the beam at the depth of the tumor. These devices are remodeled each time the size of the tumor is reduced.


A bolus (left) and a collimator (right) are custom-made for each patient so as to fit the size and depth of his or her tumor. If a proton beam is administered from different angles, a bolus and a collimator are made to fit each angle.

The respiratory-gating system?pioneered by the University of Tsukuba?ensures that the proton beam accurately targets the tumor

As a person breathes, their diaphragm moves up and down three to four centimeters, moving the liver and lungs up and down. The University of Tsukuba has developed a method known as respiratory-gating which ensures that the proton beam equipment is not affected by such movement and targets the same point every time. A laser sensor placed on the abdomen of the patient senses the movement of the body and a proton beam is emitted only when it is in the correct position.

Each treatment session lasts 15-30 minutes

You will not feel pain while you are treated with the proton beam. The administration of the proton-beam only takes one to three minutes each time. However, a session of treatment takes 15-30 minutes in total as it includes other steps, such as checking the position of the beam.


The patient lies in an immobilization device which has been custom-made to the shape of the patient’s body to help him/her keep still while receiving proton therapy. (The patient may also have to wear an immobilization device for his or her head).


Follow-up after treatment

After proton therapy is complete, we provide a medical follow-up service in cooperation with the doctor who initially referred the patient to us. Patients visit our Outpatient section once every three months for consultations regarding the progress of their condition the results of medical examinations under the referring doctor’s medical care. We continue to observe the progress of a patient’s condition for five years after the proton therapy treatment, giving necessary advice to him or her from the viewpoint of a proton therapy specialist. We provide consultations or respond to inquiry any time after the treatment as requested.