Internal dose assessment after radionuclide therapy is usually performed using home-made software packages. The dose assessment includes image registration, region-of-interest drawing, time-activity curve generation, and manual calculation of residence times followed by dose calculation with the OLINDA/MIRD software. The drawback of these methods is that several steps have to be performed using various software products possibly installed on different workstations. The aforementioned approaches are error-prone as well as difficult and time-consuming. In this article, we present a commercial software package that implements all the required dose calculation steps in 1 application, which greatly facilitates the internal dose assessment. The workflow of the newly developed software package "Hybrid Dosimetry" proceeds from automatic image registration to region-of-interest drawing, followed by time-activity curve fitting and dose calculation according to the MIRD method. The software is available online and can be run on independent computers using images in the common DICOM format. We used the package for internal dosimetry of 8 patients treated with Lu-DOTATATE and compared the results with manual dose calculation. The online software package presented is platform independent and allows fast dose calculations. The results obtained with the new package were in perfect agreement with manual methods.