Dose Distribution of Body Gamma Rays Radiotherapy for Multiple Pulmonary Metastatic Tumor

Objective To investigate the dose distribution of OUR-QGD whole body γ rays radiotherapy for multiple pulmonary metastatic tumor and evaluate its safety and feasibility. Methods Twenty cases of lung metastatic tumor, with 9-12 foci and diameter≤2.3 cm,were treated with OUR-QGD whole body γ rays radiotherapy. Twelve cases were supine and eight cases were prone. Gross target volume(GTV) was delineated in lung window, and 5 mm was enlarged as planning target volume (PTV).50% isodose line was around PTV and 70% isodose line was around 90% of GTV.The reference dose was defi ned as 50% isodose line with 4 Gy per fraction, and the prescribed dose was 52 Gy with 13 fractions. The dose distribution was evaluated by dose volume histogram (DVH). Results 52 Gy of body γ rays radiotherapy to 90% of GTV was equivalent to 94 Gy of conventional radiotherapy to 90% of GTV. The average dose for total lung of the supine patients was 8.36 Gy, and V20, V10 and V5 for total lung were 12.6%, 24.60% and 37.40%, respectively. The average dose for total lung of the prone patients was 8.57 Gy, and V20, V10 and V5 were 12.67%, 25.10% and 40.40%, respectively. Conclusion As to physical dosage, OUR-QGD whole body γ rays radiotherapy is safe and feasible for patients with multiple pulmonary metastatic tumor.