how to read img file in matlab

The img file I have is retrieved from arcgis.How can I open and read it?

Answer 1

[Thomas Koelen]

[Z,R] = arcgridread('Test.grd');
mapshow(Z,R,'DisplayType','surface');
xlabel('x (easting in meters)'); ylabel('y (northing in meters)')
demcmap(Z)

[Hana]

my image format is img and not grid