Assessment of parallel acquisition techniques in adrenal magnetic resonance imaging: does increased temporal resolution significantly improve visualization of adrenal lesions?

RATIONALE AND OBJECTIVES

To compare conventional radiofrequency coil reception techniques with parallel coil array acquisition methods in adrenal tissue visualization and to evaluate the dependence of temporal resolution on image quality in adrenal magnetic resonance magnetic resonance (MR) imaging.

MATERIAL AND METHODS

Using a 1.5 T MR imager, conventional and parallel sampled sequences were acquired in 10 healthy volunteers and 10 patients with adrenal lesions. The imaging protocol consisted of: conventional (TR/TE 4,730/125 ms; FA 150 degrees; NA 1; AT 25 s), and two parallel imaging SMASH techniques (TR/TE 4,090/125 ms; FA 150 degrees; NA 1 resulting in an AT of 12 s, as well as NA 2 resulting in an AT of 24 s) with generalized autocalibration T(2)-weighted turbo spin echo sequences with 5 mm slice thickness, 1.6 mm in-plane resolution, and an acceleration factor 2. Severity of breathing motion and aliasing artifact and overall image quality were rated on five-point scales and evaluated with student's t test; a differential receiver operating characteristic (DROC) analysis was performed.

RESULTS

Adrenal gland findings included adenomas, metastases, and hemorrhages. Acceleration of conventional turbo spin echo sequence with one signal average led to an increase in diagnostic power (DROC 0.362) as well as significant improvement in overall image quality (P(Volunteers) =.017; P(Patients) =.042) and reduction of breathing motion artifact in patients (P(Patients) =.012) while improving the temporal resolution. Parallel imaging with two signal averages resulted in further improvement of image quality over conventional imaging (DROC 0.303), (P(Volunteers) =.045; P(Patients) =.022), in the same acquisition time as the conventional method.

CONCLUSION

Parallel acceleration of sequences used for adrenal tissue visualization leads to a significant increase in diagnostic quality by significantly reducing breathing motion artifacts without sacrificing contrast indispensable for adrenal lesion characterization.