In spiral CT there is continuous acquisition by a rotating xray beam of a moving part.

When introduced back during good old days, the scan time was upto 80 sec, and it was revolutionary ( Comparable to AI revolution of today).

Seimens somatom plus was the first spiral CT .

Most of the modern CT scan machines are spiral CT aka helical CT aka Volumetric CT.

Advantages compared to conventional CT -
Spiral CT detects more lesions as conventional CT can miss the lesions in between slices.
Lesser dose to the patient ( Because of usage of lower tube current and higher table speed/pitch).

Applications of spiral CT -  Mainly because of faster acquistion
CT angiography - Because of faster acqusition, it became possible to image the blood vessels.
Multiphasic studies - Due to faster acquisition, it is possible to image organs in different phases.
Multiplanar imaging - 3 dimensional imaging aka multiplanar reformatting.
Imaging of uncoperative and psychiatric patient.
Imaging of pediatric patients - as it reduces radiation dose( due to high pitch)
Better spatial resolution - Due to volumetric acquisition.
Less motion artifacts.