**5. Radiotherapy data acquisition**

### **5.1. External beam radiotherapy**

#### *5.1.1. Immobilization*

Patient will lie supine with arms above head holding a T‐bar device and elbow supported laterally (**Figure 5**) to facilitate different beam angle entry for treatment. Knee support can be given to allow a more comfortable position when needed. Vacuum bag can be added to reduce movement if treatment time is long. For palliative setting using AP beams only, patients usu‐ ally lie supine with arms beside body.

**Figure 5.** Immobilization for thoracic radiotherapy with T‐bar and elbow support.

#### *5.1.2. Simulation*

For treatment with radical intent, computer‐tomography from cricoid to lower border of L1 is needed to cover the whole lung for calculation of lung dose. Slice thickness of 3–5 mm allows better quality of images for target volume delineation. Intravenous contrast is not essential but is preferred when mediastinal disease is present so as to allow better visualization of the extent.

For treatment of palliative intent, radiation field border can be defined by simple X‐ray simulation. Radio‐opaque markers (e.g. lead wire) can be used to mark any clinically palpable diseases that are going to be included for radiotherapy (e.g., chest wall mass, supraclavicular lymph nodes).

To aid set‐up, tattoos will be marked on beam center or isocenter, together with lateral refer‐ ence points over left and right side of the body.

### **5.2. Stereotactic body radiotherapy (SBRT)**

#### *5.2.1. Immobilization*

effect on overall survival from previous meta‐analyses that include trials using large radiation fields and nonconformal radiation techniques. However, its role with the use of modern radio‐ therapy machine and conformal radiotherapy are unclear and further research is warranted.

Patient will lie supine with arms above head holding a T‐bar device and elbow supported laterally (**Figure 5**) to facilitate different beam angle entry for treatment. Knee support can be given to allow a more comfortable position when needed. Vacuum bag can be added to reduce movement if treatment time is long. For palliative setting using AP beams only, patients usu‐

For treatment with radical intent, computer‐tomography from cricoid to lower border of L1 is needed to cover the whole lung for calculation of lung dose. Slice thickness of 3–5 mm allows better quality of images for target volume delineation. Intravenous contrast is not essential but is preferred when mediastinal disease is present so as to allow better visualization of the extent.

**Figure 5.** Immobilization for thoracic radiotherapy with T‐bar and elbow support.

**5. Radiotherapy data acquisition**

**5.1. External beam radiotherapy**

ally lie supine with arms beside body.

*5.1.1. Immobilization*

32 Radiotherapy

*5.1.2. Simulation*

Patient should be immobilized in a comfortable position to avoid movement during the lon‐ ger treatment length of each fraction. In this way, a supine position with arms above head immobilized by wing board and vacuum bag is commonly used (**Figure 6**).

**Figure 6.** Immobilization with wing board and vacuum bag for SBRT of lung cancer.

#### *5.2.2. Breathing motion assessment and correction*

Fluoroscopy can be used to visualize tumor motion. But it only allows tumor motion assess‐ ment in two dimensions and can be difficult if with indistinct border of tumors. Noncontrast four‐dimensional CT (4D CT) is a better option, which is a fast scanner that acquires multiset of CT images over consecutive phases of breathing cycle. Information about patients' breath‐ ing cycle and amplitude can be recorded by infrared reflecting marker and a coupled camera (**Figure 7**). And different CT images set will be sorted according to different phases in the respiratory cycle (**Figure 8**).

**Figure 7.** Infrared system including reflecting marker on patient's xiphsternum and coupled camera for tracking breathing cycle.

**Figure 8.** Sorting of 4D CT images by different phases in respiratory cycle.

Additional methods should be considered to reduce the tumor movement when it is ≥1cm, including abdominal compression, breath‐hold, respiratory gating, or active breathing con‐ trol. Both breath‐hold and active breathing control require sufficient lung reserve to allow holding each breath for at least 20 seconds, which may be difficult for most of patients with lung cancers. Respiratory gating allows free breathing and beam on in certain phase of respi‐ ration. But it requires the use of fiducial markers to track internal tumor motion and is time consuming. Abdominal compression is the most commonly used method but reproducibility can be difficult (**Figure 9**). So the best method to be used depends on the patient's condition, tolerance, and corporation.

*5.2.2. Breathing motion assessment and correction*

respiratory cycle (**Figure 8**).

34 Radiotherapy

breathing cycle.

Fluoroscopy can be used to visualize tumor motion. But it only allows tumor motion assess‐ ment in two dimensions and can be difficult if with indistinct border of tumors. Noncontrast four‐dimensional CT (4D CT) is a better option, which is a fast scanner that acquires multiset of CT images over consecutive phases of breathing cycle. Information about patients' breath‐ ing cycle and amplitude can be recorded by infrared reflecting marker and a coupled camera (**Figure 7**). And different CT images set will be sorted according to different phases in the

**Figure 7.** Infrared system including reflecting marker on patient's xiphsternum and coupled camera for tracking

**Figure 8.** Sorting of 4D CT images by different phases in respiratory cycle.

**Figure 9.** Abdominal compressor on patient's belly to reduce respiratory motion.
