CMR 2007: 3.04: Gadolinium chelate-enhanced imaging at 1.5 and 3 T in a rat brain glioma model, using matched gradients and receiver coils, comparing SE, 2D and 3D GRE, and 3D MP-RAGE techniques

✍ Scribed by V. M. Runge; S. A. Runge; B. Stieltjes; T. Patel; S. S. Baumann; J. Gendron; C. B. Jackson

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 78 KB
• Volume: 2
• Category: Article
• ISSN: 1555-4309
• DOI: 10.1002/cmmi.171

✦ Synopsis

the vesselwall cells are large enough. With respect to the brain the situation is even easier. Because of the presence of the blood-brain barrier (BBB), represented mainly by endothelial tight junctions, all current available MR contrast media do not leak into the brain tissue. The BBB blocks all molecules except those that cross cell membranes by means of lipid solubility (such as oxygen, carbon dioxide, ethanol and steroid hormones) and those that are allowed in by specific transport systems (such as sugars and some amino acids). Substances with a molecular weight higher than 180 Da, which include all available imaging contrast media, generally cannot cross the BBB. Therefore all MR contrast media are intravascular agents in the presence of an intact BBB. However, if the BBB is altered by circumstances which increase the permeabilty, contrast media can leak into the tissue. This is also true for the extracellular agents, as well as for blood-pool agents like Vasovist 1 .There has been a huge number of reports about the role of Vasovist 1 in MR angiography [1-4]; however, no reports exist about the extravascular behaviour of the agent and the potential in imaging tissue pathologies. In this report we present our first experience with the bloodpool agent Vasovist 1 for contrast-enhanced MR imaging of brain tumors. Methods: In a pilot study 10 consecutive patients with different intracerebral tumors were examined with a standard dose (0.03 mmol/ kg BW) of Vasovist 1 . Three patients with malignant glioma, one patient with cerebral metastases, one patient with acoustic schwannoma and five patients with meningeomas were scanned using the same sequence parameters as for an examination with standard contrast media. The imaging protocol included a T 1 -SE, T 2 -FSE and FLAIR prior contrast and contrast-enhanced T 1 -SE in axial and coronal orientation. In patients with skull base tumors, an additional fat suppression T 1 -SE was performed. The time between contrast media application and imaging was about the same for all patients at 3 min after application. All MR examinations were performed on standard clinical 1.5 T systems (Magnetom Avanto and Magneton Symphony, Siemens, Erlangen, Germany) using a circular polarized head coil or an eight-channel head coil. Eight patients were referred for follow-up MRI after radiotherapy, and two patients in the pretherapeutic work-up. In all patients previous MR examinations with a standard extracellular contrast agent (1.5 years to 2 weeks prior to the Vasovist 1 examination) were available and served as a reference. Results and Discussion: As shown in this intial report also intravascular agents like the protein binding blood-pool-agent Vasovist 1 are able to pass a disrupted BBB and allow a sufficient contrast enhancement (Fig. 1). Owing to the long intravascular half-life the contrast behavior increases over time (Fig. 2). Even if there is a smaller amount of contrast media leaking into the extracellular space, the high relaxivity of the complex might compensate for the smaller dosage of Gd, which gives a great potential also outside the brain. However, since Vasovist 1 is very different from conventional contrast agents owing to its properties, optimized acquisition patterns and especially optimized reconstruction strategies must be developed and verified clinically in a large number of cases.