Which branch of medicine utilizes radiant energy for diagnosis and treatment?

Radiology is the branch of medicine that specifically focuses on the use of radiant energy for the purposes of diagnosis and treatment. This includes various imaging techniques such as X-rays, CT scans, MRI, and ultrasound, which utilize different forms of radiant energy to visualize the internal structures of the body. Radiology plays a crucial role in identifying diseases, injuries, and abnormalities through these imaging technologies.

In addition to diagnostic procedures, radiology encompasses therapeutic techniques as well, such as radiation therapy for cancer treatment. The interplay of diagnostic and therapeutic applications of radiant energy makes radiology a vital specialty in modern medicine.

The other disciplines listed, while important in their own right, do not primarily focus on the use of radiant energy. Oncology primarily deals with cancer treatment and research, pathology focuses on the study of diseases through tissue examination, and cardiology specializes in heart conditions. Therefore, the use of radiant energy is distinctly characteristic of radiology, which is why it is the correct choice.