MRA Study on Variation of the Circle of Willis in Healthy Chinese Male Adults

Table 6

The relationship between normal lateral and variation lateral and the formation of homolateral embryonal pattern of 634 cases with A1 segment variation.

Developmental situation of A1 segment	PCA type (side)					FTP ratio (%)
	Normal	I	II	III	IV
Normal	576	8	16	13	21	9.15
Mild variation	281	5	20	23	4	15.62
Hypoplasia	172	1	15	16	2	16.50
Absence	73	2	7	12	1	23.16

Note: = , ; linear-by-linear , .