Drishti is described as 'open-source scientific visualisation software been developed with its end use in mind: ie. visualising volumetric data, such as tomography data, electron-microscopy data, etc' and is an app in the Education & Reference category. There are five alternatives to Drishti for Windows, Linux, Mac and Online / Web-based. The best alternative is ImageJ, which is both free and Open Source. Other great apps like Drishti are RadiAnt DICOM Viewer (Freemium), Fiji (Free, Open Source), Aeskulap (Free, Open Source) and postDICOM - Free DICOM Viewer (Free).
ImageJ is a public domain, Java-based image processing program developed at the National Institutes of Health. ImageJ was designed with an open architecture that provides extensibility via Java plugins and recordable macros.
Aeskulap is a medical image viewer capable to load a series of special images stored in the DICOM format for review, query and fetch DICOM images from archive nodes (also called PACS) over the network.
postDICOM is a cloud-based DICOM Viewer and clinical documents viewer. You can upload DICOM files and clinical documents using web browsers. You can upload and view your DICOM files from PCs(Windows, MacOS, Linux), tablets and phones(IOS and Android).