Final answer:
Retrospective reconstruction allows the conversion of helical data into planar raw data, an essential process in CT scans for producing interpretable images for diagnostics.
Step-by-step explanation:
The process that allows helical data to be converted into planar raw data is B. Retrospective reconstruction. This technique is used in the field of medical imaging, particularly in computed tomography (CT) scans. When a CT scan is performed, the machine collects data in a helical or spiral path around the body. Retrospective reconstruction is then used to convert this helical data into planar images that can be easily interpreted by radiologists. This reconstruction plays a crucial role in modern medical diagnostics as it provides clear and detailed cross-sectional images of the body.