I'm looking to use Life Transference as a heal spell, but I don't want my resistance to necrotic damage to get in the way.

Wizard School of Necromancy, Inured to Undeath feature:

Beginning at 10th level, you have resistance to necrotic damage, and your hit point maximum can't be reduced. You have spent so much time dealing with undead and the forces that animate them that you have become inured to some of their worst effects.

Life Transference, 3rd level Necromancy spell:

You take 4d8 necrotic damage, and one creature you choose and can see regains hit points equal to twice the damage you take.

Life Transference is one of the very few ways that Wizards can heal.

Can I choose to shut off my resistance to necrotic damage to cast Life Transference at full power? Without doing so, it would heal a total profit of a 9 health average, and be great waste of a level 3 spell.

(Personally, I'd rather let the wizard take half damage and still heal for full, because why not, but I'd still like to know what the actual answer is. Mass Healing Word is a level 3 spell, uses a bonus action, and heals 39 average with a +4 mod)