Is your feature request related to a problem? Please describe.
In monai/networks/nets/resnet.py, line 210, the get_conv1() produces the first convolutional layer in ResNet.
The convolutional kernel it produces is anisotropic, with
kernel_size=(conv1_t_size, 7, 7),
stride=(conv1_t_stride, 2, 2),
padding=(conv1_t_size // 2, 3, 3)

This might be a little adhoc.

Describe the solution you'd like
It would be great if the default convolutional kernel is isotropic or let the users decide these parameters in all three dimensions.