Background: Lesion-to-brain contrast after gadolinium administration is significantly higher at 3.0 Tesla (T) compared to 1.5 T. The high in vivo relaxivity of gadobenate dimeglumine (Gd-BOPTA) may permit the use of lower-dose contrast agents.
Purpose: To investigate whether low-dose contrast-enhanced MRI at 3.0 T using a high-relaxivity contrast agent (Gd-BOPTA) can achieve a comparable or improved contrast-to-noise ratio (CNR) for the detection of brain metastases compared with examination of the same patient at 1.5 T using a standard dose of gadopentetate dimeglumine (Gd-DTPA).
Material and methods: A total of 18 patients with known brain metastases were first imaged at 1.5 T with 0.1 mmol/kg Gd-DTPA. Patients returned at least 24 hours later for imaging at 3.0 T with Gd-BOPTA at cumulative doses of 0.025 mmol/kg, 0.05 mmol/kg, 0.075 mmol/kg, and 0.1 mmol/kg (0.1 mmol/kg body weight overall). The CNR of enhancing brain lesions compared to the normal contralateral white matter was calculated. For the 3.0 T study using different cumulative doses of Gd-BOPTA, the CNR of lesions was compared with CNR of the same lesions imaged at 1.5 T using 0.1 mmol/kg Gd-DTPA, by using the Wilcoxon matched-pairs signed-rank test.
Results: At 1.5 T with 0.1 mmol/kg Gd-DTPA, the mean CNR between enhanced lesions and cerebral white matter was 12.01 +/- 2.53. With 3.0 T imaging using different cumulative doses of Gd-BOPTA, the mean CNRs were 7.19 +/- 4.06, 15.31 +/- 6.37, 25.44 +/- 11.02, and 31.88 +/- 13.21. At 3.0 T with 0.05 mmol/kg Gd-BOPTA, CNR was 1.34-fold higher compared to CNR at 1.5 T with 0.1 mmol/kg Gd-DTPA (P <0.01).
Conclusion: Comparable contrast enhancement of brain metastases can be achieved with a 0.05-mmol/kg dose of Gd-BOPTA at 3.0 T compared to imaging at 1.5 T using 0.1 mmol/kg Gd-DTPA.