The lung x-rays of the JSRT database (www.jsrt.or.jp/jsrt-db/eng.php), have that format. I tested this code with them and it works:
fid = fopen('image.img','r','b');
oneSlice = fread(fid, [2048 2048], '*uint16','b');
img = mat2gray(oneSlice, [0,4096]);
fclose(fid);