I didn't find any plain attribute or css style to set the vertical alignment of radio buttons and by default they have middle alignment related to text. Some body here suggest to use the following style to align them top,
md-radio-button ._md-container {
top: 0px;
transform: translateY(0);
}
but I think it is good to provide something like "vertical-alignment" or "layout-align" to directly set the alignment.
Will not fix. A pull request is welcomed.