Our work discusses methods for real-time visualization of medical volumetric data sets, which can lead to faster and more reliable diagnostic processes. We have developed three visualization methods based on the ray casting algorithm: isosurface rendering, maximum intensity projection, and the emission-absorption model. We introduced two visual effects that enhance the final rendering: ambient occlusion and depth of field. We optimized the developed visualization methods for fast execution on graphics processing units and in the process introduced two novel methods: adaptive sampling and adaptive reconstruction, which contribute to faster rendering. We conducted a performance evaluation of the methods, which showed the efficiency of the implemented speed-ups and revealed the bottlenecks in the implementation. We also carried out a user evaluation study, where radiology specialists evaluated the practical suitability of the visualization methods.