Multimodal magnetic resonance (MR) imaging, including MR angiography (MRA) and MR perfusion (MRP), plays a critical role in the diagnosis and surveillance of acute ischemic stroke. However, these techniques are hindered by the low T1 relaxivity, short circulation time, and high leakage rate from vessels of clinical Magnevist. To address these problems, nontoxic polyethylene glycol (PEG)ylated upconversion nanoprobes (PEG-UCNPs) are synthesized and first adopted for excellent MRA and MRP imaging, featuring high diagnostic sensitivity toward acute ischemic stroke in high-resolution imaging. The investigations show that the agent possesses superior advantages over clinical Magnevist, such as much higher relaxivity, longer circulation time, and lower leakage rate, which guarantee much better imaging efficiency. Remarkably, an extremely small dosage (5 mg Gd kg(-1) ) of PEG-UCNPs provides high-resolution MRA imaging with the vascular system delineated much clearer than the Magnevist with clinical dosage as high as 108 mg Gd kg(-1) . On the other hand, the long circulation time of PEG-UCNPs enables the surveillance of the progression of ischemic stroke using MRA or MRP. Once translated, these PEG-UCNPs are expected to be a promising candidate for substituting the clinical Magnevist in MRA and MRP, which will significantly lengthen the imaging time window and improve the overall diagnostic efficiency.

High-Performance Upconversion Nanoprobes for Multimodal MR Imaging of Acute Ischemic Stroke.

Two systems of core-shell superparamagnetic nanoparticles in the size range of 45–80 nm have been fabricated by the coating of bare magnetite particles with either mesoporous silica or liposomes and the loading/release of the anti-cancer drug Mitomycin C (MMC) from their surfaces has been investigated. The magnetic cores of size ∼10 nm were produced by a co-precipitation method in aqueous solution, with the silica coating containing an unstructured network of pores of size around 6 nm carried out using a surfactant-templating approach and the liposome coating achieved by an evaporation-immersion technique of the particles in a lipid solution. Stability measurements using a scanning column magnetometry technique indicated that the lipid-coating of the particles halts the sedimentation otherwise apparent in <1 h for the bare magnetite to produce an ultra-stable system and thereby overcome one of the main barriers to potential in-vivo applications. Whilst an increase in stability was also observed in the sil...

/pdf/the-fabrication-and-characterization-of-stable-core-shell-wro5wrt3gr.pdf

The fabrication and characterization of stable core-shell superparamagnetic nanocomposites for potential application in drug delivery

To compare the value of inversion recovery with on-resonant water suppression (IRON) to conventional T1-weighted (T1w) MRA and computed tomography angiography (CTA) for visualization of peripheral nitinol stents. We visualized 14 different peripheral nitinol stents in vitro both using Gadolinium (Gd) and ultrasmall superparamagnetic iron nanoparticles (USPIOs) for conventional T1w and IRON-MRA using clinical grade 1.5T MR scanner and iodinated contrast material for CTA using a 256-slice CT scanner. Parameter assessment included signal- and contrast-to-noise ratio (S/CNR), relative in-stent signal and artificial lumen narrowing. X-ray angiography served as gold standard for diameter assessment. Gd-enhanced IRON-MRA exhibited highest in-stent SNR and CNR values compared to conventional T1w MRA (IRON (Gd/USPIO): SNR = 30 ± 3/21 ± 2, CNR = 23 ± 2/14 ± 1; T1w: SNR = 16 ± 1/14 ± 2, CNR = 12 ± 1/10 ± 1, all p < 0.05). Furthermore, IRON-MRA achieved highest relative in-stent signal both using Gd and USPIO (IRON (Gd/USPIO): 121 ± 8 %/103 ± 6 %; T1w: 73 ± 2 %/66 ± 4 %; CTA: 84 ± 6 %, all p < 0.05). However, artificial lumen narrowing appeared similar in all imaging protocols (IRON (Gd/USPIO): 21 ± 3 %/21 ± 2 %; T1w: 16 ± 4 %/17 ± 3 %; CTA: 19 ± 2 %, all p = NS). Finally, IRON-MRA provided improvement of the in-stent lumen visualization with an 'open-close-open' design, which revealed a complete in-stent signal loss in T1w MRA. IRON-MRA improves in-stent visualization in vitro compared to conventional T1w MRA and CTA. In light of the in vitro results with Gd-enhanced IRON-MRA, the clinical implementation of such an approach appears promising.

Off-resonance magnetic resonance angiography improves visualization of in-stent lumen in peripheral nitinol stents compared to conventional T1-weighted acquisitions: an in vitro comparison study.

Mn0.25Fe2.75O4 nanoparticles have been successfully synthesized using a coprecipitation method. PEG 6000 polymer was added on the synthesis of Mn0.25Fe2.75O4 which aimed at decreasing and preventing the emergence of aggregation between particles. The characterization of the phase structure, absorption of functional groups, and distribution of Mn0.25Fe2.75O4-PEG 6000 nanoparticles have been successfully performed using the instruments of XRD, FTIR, and Small Angel X-Ray Scatterring (SAXS) respectively. XRD characterization results showed that the phase structure formed was in the form of magnetite and corresponded to the Inorganic Crystal Structure Database (ICSD) number 9013529. The bond of Fe-O and Mn-O consecutively on the wave numbers of 430 and 482 cm−1 which were the representation of Mn0.25Fe2.75O4 material have been successfully confirmed through the characterization using FTIR, meanwhile the stretching vibrating on the wave numbers of 1251, 1352, 1472, and 1629 cm−1 for functional groups C-H is the representation of PEG template which has the chemical structure of -OH[-CH2-CH2-]n OH. SAXS characterization showed that the primary and secondary particle sizes from the Mn0,25Fe2,75O4–PEG 6000 nanoparticle were 3.08 and 11.4 nm respectively. The value is the optimum results of the PEG 6000 template influence on the synthesize of Mn0.25Fe2.75O4-PEG 6000 nanoparticles which are potential to be a raw material of magnetic fluid and gel on hyperthermia therapy.

Effect of Polyethylene Glycol (PEG) on Particle Distribution of Mn 0.25 Fe 2.75 O 4 -PEG 6000 Nanoparticles

During different studies on 1.5 Tasla equipments it was possible to obtain proper images with different values for different parts of limb. To date no research of such kind has been done in Iran and angiography of lower limbs is not done at present. In this study, it was tried to proper images of lower limbs considering the capabilities of designed protocol system.1.5 Tasla MRI equipment with optimized parameters for different positions calculated on the volunteers, patients and phantom was used. SNR and CNR images were compared, and categorized by radiologist based on diagnostic values. First stage of recovery current, a lower, mobile pre saturated pulses, NSA=1, matrix size 128 to 180 at direct phase and 256 direct frequency were selected. The qualitative value of the images 3 at pelvis area; 3 at femoral and knee areas; and 4 for knee was obtained. Total time required for imaging of lower limb was 45 minutes. This techniques is useful particularly for the patients who can not go under conventional angiography. The value of the MR images using contrast drug is higher than the images obtained by this method, however this method is cheaper.

/pdf/optimization-of-lower-limbs-mr-for-angiography-with-contrast-227w149rla.pdf

Optimization of Lower Limbs MR for Angiography with Contrast Injection in 1.5 Tasla by Time of Flight Method

Purpose

To investigate the ability of inversion recovery ON-resonant water suppression (IRON) in conjunction with P904 (superparamagnetic nanoparticles which consisting of a maghemite core coated with a low-molecular-weight amino-alcohol derivative of glucose) to perform steady-state equilibrium phase MR angiography (MRA) over a wide dose range.



Materials and Methods

Experiments were approved by the institutional animal care committee. Rabbits (n = 12) were imaged at baseline and serially after the administration of 10 incremental dosages of 0.57–5.7 mgFe/Kg P904. Conventional T1-weighted and IRON MRA were obtained on a clinical 1.5 Tesla (T) scanner to image the thoracic and abdominal aorta, and peripheral vessels. Contrast-to-noise ratios (CNR) and vessel sharpness were quantified.



Results

Using IRON MRA, CNR and vessel sharpness progressively increased with incremental dosages of the contrast agent P904, exhibiting constantly higher contrast values than T1-weighted MRA over a very wide range of contrast agent doses (CNR of 18.8 ± 5.6 for IRON versus 11.1 ± 2.8 for T1-weighted MRA at 1.71 mgFe/kg, P = 0.02 and 19.8 ± 5.9 for IRON versus −0.8 ± 1.4 for T1-weighted MRA at 3.99 mgFe/kg, P = 0.0002). Similar results were obtained for vessel sharpness in peripheral vessels, (Vessel sharpness of 46.76 ± 6.48% for IRON versus 33.20 ± 3.53% for T1-weighted MRA at 1.71 mgFe/Kg, P = 0.002, and of 48.66 ± 5.50% for IRON versus 19.00 ± 7.41% for T1-weighted MRA at 3.99 mgFe/Kg, P = 0.003).



Conclusion

Our study suggests that quantitative CNR and vessel sharpness after the injection of P904 are consistently higher for IRON MRA when compared with conventional T1-weighted MRA. These findings apply for a wide range of contrast agent dosages. J. Magn. Reson. Imaging 2013;38:836–844. © 2013 Wiley Periodicals, Inc.

Steady‐state equilibrium phase inversion recovery ON‐resonant water suppression (IRON) MR angiography in conjunction with superparamagnetic nanoparticles. A robust technique for imaging within a wide range of contrast agent dosages

Conventional MR angiography (MRA) exploits the property of exogenous contrast agents to shorten the T1 relaxation time. However, undesirable signal from surrounding tissue due to T1 recovery remains. IRON MRA is a promising off-resonance imaging technique, and provides in conjunction with superparamagnetic nanoparticles high intravascular contrast between the blood-pool and background tissue without need for image subtraction while T1 recovery of the surrounding tissue is no longer a problem.

/pdf/iron-magnetic-resonance-a-robust-technique-for-angiography-uaa3es304l.pdf

IRON magnetic resonance: a robust technique for angiography providing high blood-to-tissue contrast within the clinically approved dosage of superparamagnetic nanoparticles.

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Steady‐state equilibrium phase inversion recovery ON‐resonant water suppression (IRON) MR angiography in conjunction with superparamagnetic nanoparticles. A robust technique for imaging within a wide range of contrast agent dosages

IRON magnetic resonance: a robust technique for angiography providing high blood-to-tissue contrast within the clinically approved dosage of superparamagnetic nanoparticles.