Phase 1: Feasibility and safety of treating hospitalized patients with SARS-CoV-2 pneumonia with single or bilateral whole lung irradiation;Phase 2: Proportion with clinical improvement on a 7-point ordinal scale on day 4 after randomization

Phase 1: Feasibility and safety of treating hospitalized patients with SARS-CoV-2 pneumonia with single or bilateral whole lung irradiation;Phase 2: Proportion with clinical improvement on a 7-point ordinal scale on day 4 after randomization