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Are All Gadolinium-based Contrast Agents Similar?
highly concentrated and compact bolus of gadobutrol can confer
Figure 4: Detection of Lesions with Gadobutrol,
substantial improvements in image quality, quantifiable through Undetectable by Gadopentetate, at Equal
significantly higher SNRs and CNRs.
Gadolinium Doses
Several studies have evaluated the effects of gadolinium chelates Gadobutrol Gadopentetate
on the shortening of relaxation times and contrast enhancement,
knowing that there is an influence on these outcomes by both
relaxivity and concentration. Data originating from a rat brain
tumour model show that the application of gadobutrol at the same
gadolinium dose per weight results in markedly higher SNR and
CNR values than gadopentetate and gadoterate at three Tesla (3T).
21
Superior enhancement was observed with the double-concentrated
gadobutrol at each post-contrast time-point assessed.
More recent studies have compared the use of 0.5 and 1.0M
contrast agents in the imaging of brain tumours. One study used
exogenous contrast-based, T
2
*-weighted, gradient-recalled echo-
planar imaging to determine intracranial perfusion characteristics in
Identical slices acquired from a 64-year-old male patient with lung cancer. An additional
11 patients (six with intra-axial and five with extra-axial tumours).
lesion (circled) was detected in the left thalamus with gadobutrol (left) compared with
Patients received either 5ml of 1.0M gadobutrol or 10ml of 0.5M
gadopentetate (right).
16
Source: Anzalone et al., 2009. Reprinted with permission.
gadopentetate.
22
The investigators assessed the maximal signal
change in the region of interest as the primary outcome measure for
perfusion-weighted imaging. They found that at 3T, the higher Figure 5: Improved Conspicuity with Gadobutrol and
concentration of 1.0M gadobutrol provided significantly better
Gadopentetate at Equal Gadolinium Doses
delineation between grey and white matter. It also better defined the
presence of highly vascularised brain tumour tissue than the Slice 1 Slice 2
standard 0.5M strength gadopentetate. Gadobutrol
Visualisation of brain metastases has also been reported to be
significantly improved with gadobutrol over gadopentetate and the
detected lesions were more conspicuous.
16
In this study, equal
gadolinium dosages of each contrast agent were injected in a fully
randomised sequence into 27 patients with at least one cerebral
metastasis, with 18 hours between examinations with contrast-
enhanced MRI. A total of 67 metastatic lesions were detected using
gadobutrol enhancement compared with 65 lesions detected
with gadopentetate; in two cases lesions were observed only with
gadobutrol (see Figure 4). A comparison of images on a qualitative
level by two fully blinded and experienced neuroradiologists revealed
improved lesion conspicuity with gadobutrol in 10/27 of cases
Gadopentetate
(p=0.002; see Figure 5). The comparison also revealed equivalent
conspicuity in 17/27 cases, with no reported improvements in
conspicuity for gadopentetate over gadobutrol.
The results from these small studies suggest that highly concentrated
GBCAs confer significant advantages in imaging enhancement.
Summary and Conclusions
The differences between the physicochemical properties of GBCAs
have an impact on the stability of the chelate. In vitro experiments
have shown that the macrocyclic compounds (gadoterate, gadoteridol
Identical slices acquired from a 70-year-old female patient with breast cancer. The left
and gadobutrol) are the most stable, with an undetectable release of
frontal F2 subcortical lesion is better defined, more conspicuous and more easily assessable
Gd
3+
ions under physiological conditions.
with gadobutrol (top) than with gadopentetate (bottom).
16
Source: Anzalone et al., 2009. Reprinted with permission.
High relaxivity, correlating to improved enhancement, has also been
associated with certain gadolinium chelates over others. Studies several studies now show that the higher-molar formulation of
suggest that highly concentrated formulations may be advantageous, gadobutrol appears to confer significant advantages in imaging with
with reduced injection volumes and potentially beneficial bolus respect to conspicuity in lesion visualisation and sensitivity in lesion
effects with a smaller bolus volume and increased intravascular detection compared with other commonly used gadolinium chelates
concentration for dynamic examinations. Indeed, emerging data from at the standard 0.5M. n
EUROPEAN NEUROLOGICAL REVIEW 101
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