var imageParameters = new esri.layers.ImageParameters();
imageParameters.layerIds = [1];
imageParameters.layerOption = esri.layers.ImageParameters.LAYER_OPTION_SHOW;
polylineMLayer = new esri.layers.ArcGISDynamicMapServiceLayer("http://www.address_of_your_REST_service/MapServer", {
"imageParameters": imageParameters,
id: "polylineMLayer"
});
map.addLayer(polylineMLayer);