Neuroimaging – Considerations for Daily Practice

Neuroradiologists face growing challenges.
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“The workload at my own department has increased by thirty percent over the last five years, mainly driven by CT and MRI,” said Marco Essig, University of Manitoba, Canada. Clinical questions have become more complex, so have imaging protocols. A shortage of staff intensifies these problems. “It is all about optimization – optimization of protocols and of contrast,” said Essig.

Contrast Media

Essig named his four aspects for choosing a particular contrast medium: stability, low rate of side effects, i.e. safety, relaxivity and concentration.

He put special emphasis on gadobutrol (Gadovist®), focusing on its properties.

Good Safety Profile

With regard to safety, he pointed out that gadobutrol was well tolerated in 42 clinical phase II-IV trials with more than 7,000 patients. The data also includes 184 children and adolescents below 18 years of age, including neonates. “The adverse event profile does not differ from other macrocyclic agents,” he said.

Postmarketing data support these findings: safety data on more than 50 million administrations is consistent with the safety profile of gadobutrol during clinical trials (Endrikat 2016, Tsushima 2018).

High Relaxivity

“From a clinical perspective, it is all about visibility and contrast,” said Essig referring to reading speed and quality. In MRI, this translates to high relaxivity and T1 shortening, he added. High relaxivity results in a better signal in less time. While the relaxivity values may differ from study to study (Rohrer 2005, Noebauer-Huhmann 2010, Shen 2015) due to different measurement conditions, Essig noted that gadobutrol offered consistently high relaxivity values in all these studies. The agent’s double concentration further adds to high signal intensity.

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Useful Clinical Effects

“This effect is of practical importance for neuroimaging,” underlined Essig.

One study (Saake 2016) shows significantly higher mean multiple sclerosis lesion enhancement for gadobutrol compared to gadoterate meglumine (Dotarem®). Stronger enhancement leads to better lesion delineation. Readers had a non-significant preference in favor of gadobutrol.

Cross over studies with gadobutrol and gadobenate dimeglumine (MultiHance®) have shown a better visualization of glioblastoma multiforme with gadobutrol, using half of the contrast volume due to the agent’s double concentration.

Another study has found enhanced sensitivity for gadobutrol in metastases detection (Anzalone 2009). “We may be treating up to twenty-five or thirty lesions with radiosurgery in a patient, so every lesion we get matters,” noted Essig.

Gadobutrol also improved visualization and delineation of enhancing lesions (Anzalone 2013): It provided better lesion contrast enhancement compared to gadoterate meglumine. It also resulted in higher lesion-to-brain signal with a 9% difference in relative enhancement.

“With gadobutrol you see lesions larger and enhancing more strongly – this allows for precise lesion target delineation, which is important for treatment planning,” commented Essig. He also noted that gadobutrol has substantial impact during follow-up after therapy.

As functional MRI continues to be used more frequently, Essig stressed the fact that gadobutrol may well be included in functional techniques. He specifically mentioned new low dose indications like blood to brain influx rate assessment, but also T2* Perfusion MRI, MR Spectroscopy, T1-dynamic MRI, Diffusion-MRI, BOLD (Blood Oxygenation Level Dependent Contrast) MRI, and susceptibility weighted MRI.

References

Anzalone N et al.Detection of cerebral metastases on magnetic resonance imaging: intraindividual comparison of gadobutrol with gadopentetate dimeglumine. Acta Radiol. 2009;50(8):933-40

Anzalone N et al. Cerebral neoplastic enhancing lesions: multicenter, randomized, crossover intraindividual comparison between gadobutrol (1.0M) and gadoterate meglumine (0.5M) at 0.1 mmol Gd/kg body weight in a clinical setting. Eur J Radiol. 2013;82(1):139-45.

Endrikat J et al. Safety of Gadobutrol: Results From 42 Clinical Phase II to IV Studies and Postmarketing Surveillance After 29 Million Applications. Invest Radiol. 016;51(9):537-43.

Noebauer-Huhmann IM et al. Gadolinium-based magnetic resonance contrast agents at 7 Tesla: in vitro T1 relaxivities in human blood plasma. Invest Radiol 2010;45(9):554-8.

Rohrer M et al. Comparison of magnetic properties of MRI contrast media solutions at different magnetic field strengths. Invest Radiol 2005;40(11):715-24.

Saake M et al. MRI in multiple sclerosis: an intra-individual, randomized and multicentric comparison of gadobutrol with gadoterate meglumine at 3 T. Eur Radiol. 2016;26(3):820-8.

Shen Y et al. T1 relaxivities of gadolinium-based magnetic resonance contrast agents in human whole blood at 1.5, 3, and 7 T. Invest Radiol 2015;50(5):330-8.

Tsushima Y et al. Post-marketing surveillance of gadobutrol for contrast-enhanced magnetic resonance imaging in Japan. Jpn J Radiol.. 2018;36(11):676-85

Presentation Title: Trust the Macrocyclics – Modern Neuroimaging Protocols
Speaker: Marco Essig, University of Manitoba, Canada
Date: Friday, 28th February 2019
Session Code: SY14