Gadofosveset injection is a clear, colorless to slightly yellow solution in which the pH has been adjusted to 6. The density is 1.
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The viscosity of MS injection ranges from 2. Gadofosveset is administered either by a hand or power injector to deliver a dose of 0. Prior to approval in the European Union, gadofosveset underwent extensive evaluation of the safety and efficacy of the drug.
The clinical development program for efficacy included two phase II studies and four phase III studies. The optimal dose for MRA was found to be 0. The clinical effectiveness of gadofosveset was demonstrated through analysis of efficacy data of patients that were included in four adequate and well-controlled phase III studies. Vascular beds representative of areas of turbulent blood flow AIOD: aorto-iliac occlusive disease , flow to an organ renal artery disease , and slow flow pedal arterial disease were studied.
In all of these studies, the fundamental methodology was the same:. The efficacy evaluation of all studies included blinded reading and 3 independent blinded readers for each study were used.
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These blinded readers had no prior affiliation with the sponsor, and had not participated in other gadofosveset studies;. A total of 32 independent blinded readers 24 radiologists, 8 vascular surgeons were used in the four studies. Vascular surgeons were asked to evaluate the images for management decisions;. Images were randomized and no other clinical information was provided to the blinded readers;. No consensus reading was performed in determining the SOR. Gadofosveset reduced the rate of uninterpretability significantly and improved the diagnostic confidence Goyen et al ; Rapp et al Fewer than 2.
For comparison, 2. Safety data in patients males and females receiving 0. There were no clinically significant trends found in adverse events, laboratory assays, vital signs, ECGs, or oxygen saturation. Gadofosveset has a good safety profile and can be safely administered as an intravenous bolus injection. The overall rate and experience of adverse events was comparable to placebo and were similar to that reported in clinical trials for other Gd chelates. Considering the enormous success of extracellular gadolinium-based contrast agents for contrast-enhanced MRA, what is likely to be the role for an intravascular contrast agent such as gadofosveset?
The answer lies in the key question: can gadofosveset be used in first-pass arterial imaging with equal effect? The crucial advantage of gadofosveset, ie, the presence of persistent high intravascular enhancement significantly greater than with extracellular agents, can be exploited to acquire additional high-resolution images in the steady-state which lead to a better delineation of vessel pathology.
Steady-state imaging offers the possibility of depicting the entire vascular system without relevant extravasation of the contrast medium from the intravascular space. The extended diagnostic window of gadofosveset makes the examination more convenient because it is less dependent on the bolus dynamics.
Gadofosveset-enhanced MRA data of a year old healthy proband: after contrast agent injection and by using new multi-channel MR scanners, a MRA in dynamic or first-pass phase with purely arterial contrast can be realized for both the carotid arteries and the lower thigh arteries A , spatial resolution: 1. In the following acquisition performed during the equilibrium phase, very high spatial resolutions of below 0. Image: courtesy Konstantin Nikolaou, reproduced from Mathias Goyen ed. Vasovist — the first intravascular contrast agent for MR angiography.
ABW-Wissenschaftsverlag Berlin. Patient with symptomatic abdominal aortic aneurysm referred for peripheral MRA. The high grade stenosis of the left internal carotid artery was confirmed by 64 multi-slice CTA and the patient was discharged after successful thrombendarterectomy and aneurysm repair. After first-pass MRA of the abdomen and lower extremities A , an ultra-sonographically suspected stenosis of the left internal carotid artery is confirmed by the 0. This approach facilitates the pre-operative work-up of patients with systemic vascular disease without the need of a second contrast injection or a separate MR-examination.
Gadofosveset can be used in exactly the same way as extracellular agents with regard to first-pass imaging. The advantage of using gadofosveset for first-pass imaging lies in its much higher relaxivity Rohrer et al This means that a higher signal-to-noise ratio can be obtained when parameters are kept identical or, conversely, that spatial resolution can be increased while maintaining the same signal-to-noise ratio. The truly interesting property of gadofosveset, however, is its much longer intravascular residence time.
Equilibrium imaging is possible because, despite the fact that dilution of the injected contrast medium after first arterial passage leads to a T1 increase of the blood pool compared with the first pass, the value is still much lower than that of fat.summit.webcelebs.com/lessons-from-remand.php
First approved blood pool contrast agent
Hartmann et al estimated that T1 of blood in the equilibrium phase, 3—5 minutes after injection of 0. This prolonged T1 reduction offers the opportunity to obtain images of the vascular tree up to about 45—60 minutes after injection. The extended imaging window can be used to acquire images with much higher spatial resolution without a significant loss of vessel-to-background contrast Figure 1.
In clinical practice this means that scan duration is no longer determined by the transient T1 shortening, but by the capacity of the patient to sustain a breath-hold or to remain motionless. A possible drawback of using gadofosveset is the simultaneous enhancement of venous structures close to arteries.
This phenomenon is a well-known problem at first-pass imaging, often resulting in images that cannot be used for clinical decision-making. However, because equilibrium phase images can be acquired at much higher spatial resolution — often with a 5—fold decrease in voxel size compared with first-pass protocols — arteries can be readily separated from accompanying veins. The use of gadofosveset has reduced the deleterious consequences of missing the bolus in the first pass.
If, for whatever reason, acquisition in the first pass fails, images can always be obtained in the equilibrium phase because of the prolonged intravascular retention. Although prolonged intravascular retention is highly advantageous, it is not recommended to perform a test bolus when using gadofosveset because of this property.
If possible, it is better to acquire a dynamic series of acquisitions using a time-resolved MRA technique and to evaluate the data set with the best selective arterial opacification. Although MIP is an elegant way to collapse a 3-D volumetric data set into a 2-D projection, review of cross-sectional images remains an integral part of the evaluation, especially for data acquired in the equilibrium phase. The MIP algorithm works best when using thin-slab or curved subvolume selections.
In whole-volume MIPs, contrast-enhancing organs or other vascular structures may superimpose over smaller arteries when they have higher signal intensities along a particular viewing path. When working with equilibrium-phase images, the use of thin-slab sub-volume MIPs can be particularly useful. Another helpful technique for the precise evaluation of vessel morphology, especially when evaluating equilibrium phase data, is curved multiplanar reformation cMPR along the axis of the arterial segment of interest. Most post-processing workstations offer the ability to interactively generate a cMPR while scrolling through source images.
This technique is particularly useful to obtain views of eccentric stenoses, and as a basis to generate views perpendicular to the central axis of the vessel to measure cross-sectional area reduction in stenoses. For the diagnostic assessment of the abdominal vasculature, contrast-enhanced CE -MRA — together with computed tomography angiography CTA — has become the clinically accepted standard of reference and has replaced conventional digital subtraction angiography. In abdominal aortic aneurysm or dissection, CE-MRA allows a simultaneous assessment of the aneurysmal extent and involvement of the renal, visceral or iliac arteries.
With gadofosveset, the first pass of the compound can be used for time-resolved MRA, allowing a dynamic assessment of the perfusion of the visceral organs and visualization of blood-flow differences in the true and false lumen of aortic dissection Schoenberg et al In patients with endovascular repair of abdominal aortic aneurysm, blood-pool agent-enhanced MRA might be more accurate for the detection of endoleakage than contrast-enhanced CT Ersoy et al In patients with atherosclerotic disease, the potential to increase the spatial resolution during the steady state promises a higher accuracy for the detection of vascular stenoses than conventional MRA with extracellular contrast agents.
In patients with aortoiliac disease, Vogt et al reported a higher agreement regarding stenosis location and degree of stenosis of gadofosveset-enhanced MRA and DSA compared with a non-contrast, time-of-flight MRA.
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Due to the limited breath-hold capacity of the patients, imaging has to take place during suspended breath-hold, limiting acquisition time and thereby reducing the spatial resolution. Gadofosveset as a blood pool contrast agent may overcome this limitation of MRA by facilitating longer respiratory-gated MRA acquisitions. Due to the widespread use of 3-D post-processing tools, the venous signal does not interfere with diagnostic image reading. In addition, the first pass of the contrast agent can be used to measure renal perfusion Michaely et al Due to the high relaxivity of gadofosveset, only a fraction of the amount of gadolinium that would be required for extracellular contrast agents is needed.
Gadofosveset may also be valuable in patients who are being evaluated as potential renal donors, as the entire abdomino-pelvic arterial and venous system can be examined after a single injection of contrast agent. This eases workflow and should eventually be more cost-efficient. The assessment of the pulmonary arteries for pulmonary embolism is an interesting application for gadofosveset-enhanced MRA.
Although CT is nowadays the first-line imaging tool for the assessment of patients with suspected pulmonary embolism, contrast-enhanced MRI is very appealing as it allows for a comprehensive radiation-free assessment of pulmonary perfusion and direct visualization of embolic material in the pulmonary arteries using a single contrast agent injection.
Moreover, MR venography of the deep venous system can be added for the assessment of underlying deep venous thrombosis without an additional contrast agent Fink et al Recently, an animal study indicated that the higher relaxivity of a blood pool contrast agent together with the increased signal-to-noise ratio of 3 T effectively supports highly accelerated, parallel acquisition, time-resolved pulmonary MRA Nael et al For cardiac imaging, the direct visualization of coronary arteries is a major challenge for MRI.
Although multislice-CT coronary angiography is now the preferred non-invasive imaging technique for the assessment of coronary disease, blood-pool contrast agents may change the role of CE-MRA.
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Animal and volunteer studies of coronary MRA using blood-pool agents have been reported by different authors using different blood-pool contrast agents. Though heterogeneous in their set-up, all studies reported a significant advantage in coronary imaging compared with extracellular contrast agents Shoenberg et al ; Li et al ; Huber et al ; Sakuma et al ; Zheng et al A final assessment of the clinical value of this method is still pending. CE-MRA of the peripheral vasculature has evolved over the past few years from an experimental imaging modality to a technique that is now widely applied in clinical practice.
The recent introduction of gadofosveset expands the diagnostic armamentarium of the radiologist by opening up new opportunities in the field of peripheral MRA. The higher relaxivity and prolonged intravascular residence time of gadofosveset yield better first-pass image quality, as well as the possibility of obtaining additional steady-state MRA data. The latter property will lead to a fundamental paradigm shift in MR imaging of the vasculature, enabling the migration to equilibrium-phase ultra-high spatial resolution imaging sequences. Initially, there were concerns in regard to the presence of venous overlay on the steady-state 3D-CE-MRA data sets, particularly for arteries with small vessel calibre and close-by coursing veins such as in the distal calves.
Due to the absence of motion artefacts in the peripheral arteries, exquisite image quality can be achieved allowing already for visual artery-vein separation despite the close proximity of theses vessels. Artery-vein separation can be further enhanced by the use of semi-automated software, which is currently under preparation by different vendors.