作者单位:Vet Affairs Puget Sound Hlth Care Syst, Gen Med Serv, Seattle, WA 98108 USA[1]Vet Affairs Puget Sound Hlth Care Syst, Diagnost Imaging Serv, Seattle, WA 98108 USA[2]Vet Affairs Puget Sound Hlth Care Syst, Hlth Serv Res & Dev, Seattle, WA 98108 USA[3]