A method for reviewing medical study data by means of a viewing application running on a user's device, the method comprising the following steps: a. the viewing application creates a user interface including a drawable region on the user's device, and sends a request for a review session to a first server; b. at least one stateful helper is allocated to the viewing application, wherein a helper is a software application on the first or another server, and at least one communication channel is established between the viewing application and the helper; c. in response to requests from the viewing application, the helper retrieves medical study data from a data storage and utilizes at least part of said medical study data to maintain an hierarchical scene graph containing items to be displayed, such items including a texture including image data from the medical study data as well as a graphical overlay; and from such scene graph, the helper generates a stream of drawing commands, which is transferred to the viewing application through the communication channel, wherein the helper does not render and transfer entire images to be displayed on the user's device; d. wherein the stream of drawing commands contains instructions on how to render images to be displayed in the drawable region, and the viewing application interprets the drawing commands to thereby render a time series of frames (52, 54) displayed in the drawable region, wherein a frame is whatever is displayed within the drawable region at one time point; wherein at least part of the drawing commands are cached on the user's device, so that the helper will not transfer the cached drawing commands again, and will transfer a drawing command relating only to a difference between one frame and the next, wherein the medical study data includes a time series of medical images, which are displayed in the time series of frames in the drawable region in a loop, and wherein the viewing application caches drawing commands including data buffers containing image data to be displayed as well as time stamps relating to each medical image within the time series, and drawing commands relating to the difference between one frame and the next, so that the viewing application is able to display the loop without intervention of the helper. a. the viewing application creates a user interface including a drawable region on the user's device, and sends a request for a review session to a first server; b. at least one stateful helper is allocated to the viewing application, wherein a helper is a software application on the first or another server, and at least one communication channel is established between the viewing application and the helper; c. in response to requests from the viewing application, the helper retrieves medical study data from a data storage and utilizes at least part of said medical study data to maintain an hierarchical scene graph containing items to be displayed, such items including a texture including image data from the medical study data as well as a graphical overlay; and from such scene graph, the helper generates a stream of drawing commands, which is transferred to the viewing application through the communication channel, wherein the helper does not render and transfer entire images to be displayed on the user's device; d. wherein the stream of drawing commands contains instructions on how to render images to be displayed in the drawable region, and the viewing application interprets the drawing commands to thereby render a time series of frames (52, 54) displayed in the drawable region, wherein a frame is whatever is displayed within the drawable region at one time point;