In MRI, the specific absorption rate (SAR) is a measure of:
- A The energy deposited per unit mass of tissue by the radiofrequency pulses ✓
- B The rate of gadolinium contrast uptake by tissues
- C The rate of T1 relaxation of fat versus water
- D The magnetic field homogeneity across the imaging volume
Correct answer: A. The energy deposited per unit mass of tissue by the radiofrequency pulses
Explanation
SAR quantifies the power absorbed per kilogram of tissue (W/kg) from RF pulses. It is regulated by the FDA and IEC to prevent excessive tissue heating. SAR increases with field strength, flip angle, and TR. It limits the number of slices and sequence parameters, especially at 3 Tesla. It is unrelated to contrast uptake, T1 relaxation rates, or field homogeneity.
Reference: Westbrook, MRI in Practice, 5th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.