> The page where all the waveforms will be there in form of thumbnails with
> the details of when was it posted, who posted it and its status (whether
> already commented or is still new) is to be designed. This page will be
> accessible only to valid users.
>
OK. This implies a database with all that information. Should pose no
problem.

> The thumbnails will be posted by the doctors having any difficulty or
> needing some expert comments on the waveform. The experts can log on to
> the page click on the thumbnail, which will enlarge to a real view with a
> provision to write the comments. These comments will
> automatically emailed
> to the respective doctor. The ECG that has been replied to has then to be
> shown status as replied or make it lighter (as in our emails)
>
You can either store the received images on disk (with a URL in the
database) or in the database itself. Given the short time, the first option
is probably faster to implement.
Generating thumbnails on the fly is tricky, you'll need some library for
this. Again, store thumbnails in the database or on disk with a link in the
database.
Javamail can be used to mail back the comments.