Roughly speaking, like the following (untested):

SELECT MTG_QCA = CASE WHEN ttss_avgeqcapointscore < 1 THEN 0

ELSE ROUND([LAT2011].[Gamma0] + [LAT2011].[Gamma1]

* [ttss_avgeqcapointscore]

+ [LAT2011].[Gamma2]

* POWER([ttss_avgeqcapointscore], 2)

+ [LAT2011].[Gamma3]

* POWER([ttss_avgeqcapointscore], 3)

+ [LAT2011].[Gamma4]

* POWER([ttss_avgeqcapointscore], 4), 2)

END

It's just a syntax difference