Methodology of continuous extracranial radiosurgery for lung cancer using EXOMIO 3-D CT simulation

It is well known that precision can be achieved using radiosurgery for brain tumors. This method can be extended to treat localized lung tumors and lung metastases.

The conventional procedure of extracranial radiosurgery is contained in the following steps: adaptation of the vacuum mattress, planning CT, three-dimensional (3-D) treatment planning, CT repositioning, and irradiation. In the new procedure of continuous extracranial radiosurgery, a short treatment planning is often used for simple target shapes (spherical, rotation-symmetrical), and the irradiation follows directly after the planning procedure. During continuous extracranial radiosurgery, the patient has to lie still in the body frame from the planning CT to irradiation. Fast treatment planning is performed by using multileafs and EXOMIO (Medintec, Bochum, Germany), a software for CT simulation. The high quality of the digitally reconstructed radiographs (DRRs) of each field enables a high precision in dose application by the comparison with the verification radiograph and the DRR (Elekta iView, Hamburg, Germany).

In five lung cancer patients the average time for the complete procedure from planning CT to irradiation was 107 min (range: 91-124 min). The mean positioning accuracy of the patient in the vacuum bed (total shift) was 3.3 mm (range: 2.9-4.7 mm).

Continuous extracranial radiosurgery can be performed for small peripheral lung tumors or metastases and is optimizing the conventional procedure. It is of special interest to clinics with restricted CT capacity.