Brachytherapy is a very successful treatment option for many different tumors. Consequently the quality assurance (QA) of afterloaders is of special interest. For many quality checks verification films are essential. Because currently in many clinics the film development units are replaced by computed radiography systems, the question arises of how to perform QA for afterloaders without conventional radiography films. In this note the use of a new designed multi-slit phantom demonstrates the possibility of performing QA checks with high sensitivity computed radiography systems. Because the presented phantom allows a method for imaging the radiation source it might be useful in the development of further QA techniques.