MRI vs CT

I have a movable, palpable mass sitting just atop my left sternoclavicular head. The ultrasound indicates further CT testing. I'm 58 and concerned about pumping radiation into my neck if there's a reasonable alternative -- eg., an MRI w/ contrast. Is a CT that much better? Or is it just cheaper? Or should I go straight for a biopsy?

The Radcat 3 ultrasound report:

"IMPRESSION: Heterogeneous circumscribed isoechoic lesion within the subcutaneous soft tissues, which may represent an ill-defined lipoma or lobulated fat. However, consider CT of the neck with IV contrast for further evaluation.
FINDINGS:
Dedicated images at the patient's area of palpable concern within the left supraclavicular region reveal a circumscribed, lobulated isoechoic region, measuring 1.7 x 0.7 x 1.9 cm. No fluid collection."