Abstract:
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Purpose: As SNR/CNR increase with field strength, T1-shortening contrast agents may be more effective at higher magnetic field. To quantify these effects in-vivo, we performed an intra-individual comparative trial on patients with contrast enhancing brain lesions. The aim was to find out whether increased SNR/CNR at higher magnetic field permit to reduce the dose of contrast agent at a given lesion contrast.
Methods and Materials: This is an intra-individual comparative study on 12 patients (6 female, 6 male, mean age 58 years), eleven with primary brain tumors and one with cerebral metastases. All patients underwent contrast-enhanced MRI on 3 consecutive days: Once at 1.5T (standard protocol, full dose with 0.1 mmol/kg Gd-DTPA), once with full dose at 3T, and once with half-standard dose (0.05 mmol/kg) at 3T. The same postcontrast T1-weighted SE images (TR=500ms; 5mm; 256x206) were obtained. CNR was assessed by ROI-analysis of enhancing lesions and contralateral white matter.
Results: At 3T and full dose, CNR was 2.5-fold higher than at 1.5T and full dose. Half-standard dose at 3T still yielded higher CNR (1.3-fold) than full dose at 1.5T.
Conclusion: Owing to the inherently higher SNR/CNR at 3T, these data suggest that it is possible to halve the contrast dose and achieve at least an equivalent CNR of enhancing brain lesions compared to full dose at 1.5T. Additionally, we suppose that in selected cases (e.g. search for subtle blood-brain-barrier disruptions secondary to metastases or inflammation), the full dose at 3T may be used to increase sensitivity compared to full dose imaging at 1.5T.
Krautmacher MD, C,
Intra-individual Study Comparing Standard and Half-standard Contrast Medium Dose at 3T versus 1.5T in Contrast Enhancing Brain Tumors. Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL.
http://archive.rsna.org/2003/3102703.html
