Whole-body MR angiography with body coil acquisition at 3 T in patients with peripheral arterial disease using the contrast agent gadofosveset trisodium

Relative value of three whole-body MR approaches for PET-MR, including gadofosveset-enhanced MR, in comparison to PET-CT

PURPOSE

Evaluate MR protocol for PET-MR including coronal DWI (cDWI), fat-suppressed T2 (T2w), and gadofosveset-enhanced T1 (CE).

MATERIALS AND METHODS

18 patients underwent same-day PET-CT and PET-MR. Image quality and performance of each sequence, and combination of all three sequences, was evaluated with respect to PET-CT.

RESULTS

Lesion conspicuity was best on cDWI, while delineation was best on CE. Considering all three sequences combined, both readers showed good sensitivity and specificity (>80%). Relative sensitivity was highest on CE and lowest on T2w.

CONCLUSIONS

Whole-body MR performed well in detecting malignant lesions compared to PET-CT. CE showed overall highest performance.

Improved quality and diagnostic confidence achieved by use of dose-reduced gadolinium blood-pool agents for time-resolved intracranial MR angiography

BACKGROUND AND PURPOSE

Time-resolved MRA with the use of bolus injection of paramagnetic agents has proved valuable in neurovascular imaging. Standard contrast agents have limited blood-pool residence times, motivating the development of highly protein-bound blood-pool agents with greater relaxivity and longer intravascular residence, affording improved image quality at lesser doses. This study represents the first comparison of blood-pool agents to standard agents in time-resolved cerebral MRA.

MATERIALS AND METHODS

One hundred datasets were acquired at 1.5 T by use of a standardized, time-resolved MRA protocol. Patients received either unit dosing of a standard extracellular agent at 0.1 mmol/kg or a blood-pool agent at 0.03 mmol/kg. Peak arterial and venous enhancement phases were identified and subsequently scored qualitatively by use of a 4-point Likert scale, with attention to 6 vascular segments: 1) intracranial ICA; 2) MCA M1; 3) MCA M2; 4) MCA M3; 5) deep cerebral veins; and 6) dural venous sinuses.

RESULTS

Fifty MR angiographies were acquired with each agent. No significant differences were found between agents in generation of uncontaminated arteriograms. Blood-pool agents, at 67% dose reduction, were of significantly greater quality across most vascular segments, including ICA (P = .019), M2 (P = .003), and M3 (P < .01). Superiority in the M1 segment approached significance (P = .059). Significantly better venographic quality was noted for deep venous structures (P = .016) with the use of blood-pool agents.

CONCLUSIONS

Blood-pool agents provide superior demonstration of most intracranial vessels in time-resolved MRA compared with standard agents, at reduced doses. The greater relaxation enhancement and more favorable dosing profile make blood-pool agents superior to standard agents for use in cerebral time-resolved MRA.

Improved detection of in-stent restenosis by blood pool agent-enhanced, high-resolution, steady-state magnetic resonance angiography

OBJECTIVE

The aim of this study was to assess whether visualisation of in-stent changes can be improved with high-resolution, steady-state, blood pool contrast-enhanced MR angiography compared with first-pass MR angiography. Intra-arterial digital subtraction angiography (DSA) served as the reference standard.

METHODS

Twenty patients after stent placement in the superficial femoral artery (SFA) underwent MRA prior to reintervention. MRA of the SFA includes first-pass MRA as well as 3D high-resolution MRA in the steady state (SS-MRA) after injection of Gadofosveset trisodium. Sensitivity and specificity values for the detection of significant in-stent lesions by means of SS-MRA were calculated at the proximal, middle and distal stent segments in comparison to DSA. Kappa statistics were used to determine agreement between the two techniques.

RESULTS

Sensitivity and specificity values for the detection of significant stenosis with SS-MRA reached 95% in the proximal, 100% in the middle and 100% in the distal stent segment. Kappa coefficients between SS-MRA and DSA were 0.789, 0.797 and 0.859 for the proximal, middle and distal segments, whereas the Kappa coefficients for FP-MRA were 0,211, 0,200 and 0,594 in these segments, respectively.

CONCLUSION

Detection of in stent stenosis is significantly improved using SS MRA, in comparison to state-of-the-art FP-MRA.

MR angiography of collateral arteries in a hind limb ischemia model: comparison between blood pool agent Gadomer and small contrast agent Gd-DTPA

The objective of this study was to compare the blood pool agent Gadomer with a small contrast agent for the visualization of ultra-small, collateral arteries (diameter<1 mm) with high resolution steady-state MR angiography (SS-MRA) in a rabbit hind limb ischemia model. Ten rabbits underwent unilateral femoral artery ligation. On days 14 and 21, high resolution SS-MRA (voxel size 0.49×0.49×0.50 mm³) was performed on a 3 Tesla clinical system after administration of either Gadomer (dose: 0.10 mmol/kg) or a small contrast agent (gadopentetate dimeglumine (Gd-DTPA), dose: 0.20 mmol/kg). All animals received both contrast agents on separate days. Selective intra-arterial x-ray angiograms (XRAs) were obtained in the ligated limb as a reference. The number of collaterals was counted by two independent observers. Image quality was evaluated with the contrast-to-noise ratio (CNR) in the femoral artery and collateral arteries. CNR for Gadomer was higher in both the femoral artery (Gadomer: 73±5 (mean ± SE); Gd-DTPA: 40±3; p<0.01) and collateral arteries (Gadomer: 18±4; Gd-DTPA: 9±1; p = 0.04). Neither day of acquisition nor contrast agent used influenced the number of identified collateral arteries (p = 0.30 and p = 0.14, respectively). An average of 4.5±1.0 (day 14, mean ± SD) and 5.3±1.2 (day 21) collaterals was found, which was comparable to XRA (5.6±1.7, averaged over days 14 and 21; p>0.10). Inter-observer variation was 24% and 18% for Gadomer and Gd-DTPA, respectively. In conclusion, blood pool agent Gadomer improved vessel conspicuity compared to Gd-DTPA. Steady-state MRA can be considered as an excellent non-invasive alternative to intra-arterial XRA for the visualization of ultra-small collateral arteries.

Comparison of gadofosveset trisodium and gadobenate dimeglumine during time-resolved thoracic MR angiography at 3T

RATIONALE AND OBJECTIVES

Gadofosveset trisodium is a blood-pool contrast agent (BPA) that shows a less pronounced r1 relaxivity advantage over gadobenate dimeglumine at 3T than at 1.5T. However, there are few data on image quality during first-pass imaging of the thoracic vasculature with gadofosveset trisodium at 3 T. Therefore, it was the aim of this study to compare first-pass imaging characteristics of gadofosveset trisodium to gadobenate dimeglumine during time-resolved contrast-enhanced three-dimensional magnetic resonance angiography (CE MRA) at 3 T.

MATERIALS AND METHODS

Twenty volunteers underwent time-resolved CE MRA on a 3 T magnetic resonance (MR) system with a standard eight-channel phased-array surface coil, receiving either gadofosveset trisodium (blood pool agent [BPA], n = 10) or gadobenate dimeglumine (standard contrast agent, [SCA], n = 10). Image quality was assessed by two independent readers using a Likert scale ranging from 0 = poor quality to 3 = excellent quality, and relative signal-to-noise and contrast-to-noise ratios were calculated.

RESULTS

Equally good to excellent first-pass image quality was confirmed for time-resolved CE MRA using BPA and SCA (arteries, 2.8 ± 0.2 and 2.6 ± 0.4; veins, 2.5 ± 0.3 and 2.2 ± 0.4; artifacts, 2.4 ± 0.2 and 2.3 ± 0.1). Signal-to-noise and contrast-to-noise ratios showed nonsignificant differences, except for left subclavian artery values. There was an overall nonsignificant superiority in signal-to-noise and contrast-to-noise ratios for standard contrast agent in arterial values and BPA regarding venous values.

CONCLUSIONS

Despite a markedly decreased r1/r2 relaxivity ratio, first-pass imaging characteristics of gadofosveset trisodium and gadobenate dimeglumine are equally well suited for first pass time-resolved CE MRA at 3 T.