Modalities of necessity and possibility are called "alethic" modalities. Research efforts are focused on new angiogenic treatment modalities and various (adult) stem-cell therapies. These techniques are reserved for the most difficult cases where other therapeutic modalities have failed. Hyperthermia is often applied in combination with established treatment modalities for tumor treatment. A definite diagnosis often requires confirmation by diagnostic imaging modalities. PDT has the most supporting evidence of all light therapy modalities. Continuing education in naturopathic modalities for health care professionals varies greatly. Sensory stimulation refers to regaining sensory perception through the use of modalities. The two primary modalities of rosacea treatment are topical and oral antibiotic agents. Some modalities of alternative medicine employ prayer. Vitrectomy is frequently combined with other modalities of treatment. Different types of potentials result from stimuli of different modalities and types. Radiography is a deeply diverse profession with many different modalities and specialities. MRI scans give the best soft tissue contrast of all the imaging modalities. Recent developments of intravascular OCT included the combination with other optical imaging modalities.