The generator matrix

 1  0  1  1  1  1  1  1  1  0  1  1  1  0  1  1  1  X
 0  1  1  a a^2*X+a^2  0 a^2*X+1  a a^2*X+a^2  1  0 a^2*X+1 a^2*X+a^2  1  X a*X+a^2 a^2*X+1  1
 0  0 a^2*X  0  X  0  X a*X a*X a*X a*X a^2*X a^2*X a*X a*X  0  X  0
 0  0  0  X a*X a*X  0 a*X  X  X  0  X a*X a*X a*X  X  X a^2*X

generates a code of length 18 over F4[X]/(X^2) who´s minimum homogenous weight is 46.

Homogenous weight enumerator: w(x)=1x^0+192x^46+132x^48+576x^50+360x^52+1344x^54+480x^56+960x^58+27x^64+24x^68

The gray image is a linear code over GF(4) with n=72, k=6 and d=46.
This code was found by Heurico 1.16 in 2.36 seconds.