Additional MR contrast dosage for radiologists' diagnostic performance in detecting brain metastases: A systematic observer study at 3 T

Purpose: To evaluate the diagnostic performance of a double-dose administration of gadolinium for brain metastases at 3 T in a systematic observer test. Materials and Methods: Postcontrast MR images of 39 patients (total 104 metastases) were obtained by 3D T1-weighted sequences with both standard and cumulative double dose contrast administration. An observer test involving 9 radiologists (5 board-certified radiologists and 4 residents) was performed, and their diagnostic performance with the two doses was compared by means of sensitivity, false-positives, reading time, and a figure-of-merit. Results: Compared to the standard dose, the double dose showed higher sensitivity (P < 0.0001), higher false-positive/case (P < 0.05), longer reading time (P < 0.05), and higher figure-of-merit (P < 0.0001). Particularly in small lesions (<5 mm), sensitivity with the double dose (61.5 %, P < 0.0001) was approximately twice as high as that with the standard dose (29.5 %). Artifacts and blood vessels were the most common imaging findings resulting in false-positives. Conclusions: The double dose improved detection for metastases smaller than 5 mm at 3 T and thus resulted in better diagnostic performance of radiologists. However, a higher dose might result in prolonged reading time and increased false-positives, presumably due to increased vessel signals and frequency of flow-related artifacts.