T1 Relaxation Values Research Articles

Synthesis and Characterization of DHA/ZnO/ZnFe2O4 Nanostructures for Biomedical Imaging Application

DHA/ZnO/ZnFe2O4 nanostructures having crystalline size below 20nm were synthesized by hydrothermal process in the presence of a small amount of biologically useful molecule (ascorbic acid, AA) and oxidized form of AA (dehydroscorbic acid, DHA) binds with nanostructures to modified their surface which provides them water dispersible property because of hydrophilic character of DHA. Crystalline phase and size of the synthesized nanostructures were analyzed by X-ray diffraction (XRD) and Transmission Electron Microscope (TEM). The formation of ZnO and ZnFe2O4 phases were further confirmed by means of their IR characteristic bands and the binding of DHA with ZnO/ZnFe2O4 nanostructures were confirmed by IR spectroscopy. MRI contrast behavior of nanostructures was studied by T1, T2 weighted MRI imaging of nanostructures dispersed water phantoms, its T1 and T2 relaxivity value were found to be 21.76 and 0.148 ppm-1mS-1 which reveals that these nanostructure has T2 contrast property and can generate contrast more effectively in T2 weighted MRI images. Optical property of ZnO, magnetic property of ZnF2O4, nontoxic metal constitutes and biologically important dehydroascorbic acid molecule binding with ZnO/ZnFe2O4 suggested their suitability for biomedical application.

Multifunctional pH-sensitive polymeric nanoparticles for theranostics evaluated experimentally in cancer

A multifunctional pH-sensitive polymeric nanoparticle system was developed for simultaneous tumor magnetic resonance imaging (MRI) and therapy. The nanoparticles were self-assembled using the multi-block polymer poly(lactic acid)-poly(ethylene glycol)-poly(l-lysine)-diethylenetriamine pentaacetic acid (PLA-PEG-PLL-DTPA) and the pH-sensitive material poly(l-histidine)-poly(ethylene glycol)-biotin (PLH-PEG-biotin). The anti-hepatocellular carcinoma (HCC) drug sorafenib was encapsulated inside the nanoparticles. Gd ions were chelated to the DTPA groups which were distributed on the nanoparticle surface. Biotinylated vascular endothelial growth factor receptor (VEGFR) antibodies were linked to the surface biotin groups of nanoparticles through the avidin linker to form the target pH-sensitive theranostic nanoparticles (TPTN). TPTN exhibited spherical or ellipsoidal shapes, uniform particle size distribution (181.4 ± 3.4 nm), positive zeta potential (14.95 ± 0.60 mV), high encapsulation efficiency (95.02 ± 1.47%) and drug loading (2.38 ± 0.04%). The pH-sensitive sorafenib release from TPTN was observed under different pH values (47.81% at pH = 7.4 and 99.32% at pH = 5.0, respectively). In cell cytotoxicity studies, TPTN showed similar antitumor effect against HepG2 cells compared to solubilized sorafenib solution after pre-incubation in acid PBS (pH = 5.0) for 1 h in vitro (P > 0.05). In in vivo anti-tumor studies, TPTN showed significantly higher antitumor effect in H22 tumor (VEGFR overexpressed cell line) bearing mice compared to the solubilized sorafenib solution (oral or i.v. administration) group (P < 0.05). In the MRI test, the T1 relaxivity value of TPTN was 17.300 mM(-1) s(-1) which was 3.6 times higher than Magnevist® (r1 = 4.8 mM(-1) s(-1)). As a positive contrast agent, TPTN exhibited higher resolution and longer imaging time (more than 90 min) in the MRI diagnosis of tumor-bearing mice compared to Magnevist® (more than 60 min). Furthermore, histological examination of TBN (blank TPTN, without sorafenib loaded) showed no visible tissue toxicity compared to normal saline. Thus, TPTN possessed dual-loading drugs and imaging agents, active targeting and pH-triggered drug release properties in one platform with good biocompatibility. All of these results indicated that TPTN was a promising theranostic carrier which could be a platform for the development of novel multifunctional theranostic agents.

T1 and T2 Metabolite Relaxation Times in Normal Brain at 3T and 7T

This study was designed to measure T1 and T2 relaxation times of the singlets in normal brain at 7T. Our results demonstrated that the T1 relaxation values of total creatine (tCr)-CH3 and N-acetyl aspartate (NAA) in the parietal white matter significantly increased at 7T compared to 3T, while the T1 of Choline-containing compounds (Cho) was similar between field strengths.

Improved accuracy of myocardial blood flow quantification by first pass perfusion MR when corrected for steady state T1 relaxation

Background Quantification of myocardial blood flow (MBF) on firstpass dynamic contrast enhanced (DCE ) MR perfusion imaging has been performed by several different methods. However MBF estimates are dependent on the analysis model used, as the absolute concentration of the contrast agent during first pass is not known. To improve the accuracy of the MBF estimates calibration is required. We propose a novel approach for the quantification of MBF based on patient-specific calibration using steady state T1 relaxation values (1) (figure 1).

Mn-citrate and Mn-HIDA: intermediate-affinity chelates for manganese-enhanced MRI

In this study we investigated two manganese chelates in order to improve the image enhancement of manganese-enhanced MRI and decrease the toxicity of free manganese ions. Since both MnCl₂ and a low-affinity chelate were associated with a slow continuous decrease of cardiac functions, we investigated intermediate-affinity chelates: manganese N-(2-hydroxyethyl)iminodiacetic acid (Mn-HIDA) and Mn-citrate. The T₁ relaxivity values for Mn-citrate (4.4 m m⁻¹ s⁻¹) and Mn-HIDA (3.3 m m⁻¹ s⁻¹) in artificial cerebrospinal fluid (CSF) were almost constant in a concentration range from 0.5 to 5 m m at 37 °C and 4.7 T. In human plasma, the relaxivity values increased when the concentrations of these Mn chelates were decreased, suggesting the presence of free Mn²⁺ bound with serum albumin. Mn-HIDA and Mn-citrate demonstrated a tendency for better contractility when employed with an isolated perfused frog heart, compared with MnCl₂. Only minimal changes were demonstrated after a venous infusion of 100 m m Mn-citrate or Mn-HIDA (8.3 µmol kg⁻¹ min⁻¹) in rats and a constant heart rate, arterial pressure and sympathetic nerve activity were maintained, even after breaking the blood-brain barrier (BBB). Mn-citrate and Mn-HIDA could not cross the intact BBB and appeared in the CSF, and then diffused into the brain parenchyma through the ependymal layer. The responses in the supraoptic nucleus induced by the hypertonic stimulation were detectable. Therefore, Mn-citrate and Mn-HIDA appear to be better choices for maintaining the vital conditions of experimental animals, and they may improve the reproducibility of manganese-enhanced MRI of the small nuclei in the hypothalamus and thalamus.

Magnetic Resonance Cholangiography in Living Donor Liver Transplantation: Comparison of Preenhanced and Post-Gadolinium-Enhanced Methods

The purpose of this study was to evaluate the image quality and diagnostic accuracy of postgadolinium complex of diethylenetriaminepentaacetic acid (GD-DTPA)-enhanced magnetic resonance cholangiography (MRC) in donor selection. Donors (n=228) with both preoperative MRC and intraoperative cholangiography (IOC) were enrolled in this study. MRC pre- and post-GD-DTPA enhancement were performed using 1.5-T magnetic resonance imaging. The signal-to-noise ratio (SNR) of liver parenchyma and contrast-to-noise ratio of bile duct, as well as the contrast between bile duct and liver parenchyma, were calculated. The biliary anatomy correlation with the IOC during hepatectomy and patient prognosis were also evaluated. Quantitative results of the SNR of the liver parenchyma post-GD-DTPA were statistically significantly lower than preenhanced MRC (2.69 times reduced from the preenhanced MRC). The contrast of the bile duct and liver parenchyma in post-GD-DTPA were significantly higher than the preenhancement MRC. The anatomic diagnostic accuracy rate of post-GD-DTPA MRC was 92.9%. The sensitivity and specificity of GD-PTPA MRC were 85% and 96%, respectively. GD-DTPA-enhanced MRC has higher accuracy than the preenhanced MRC (92.9% vs 75%). The concurrence between GD-DTPA-enhanced MRC and IOC were commendable (kappa=0.9). The posttransplant biliary complication rate was 5.5%, and the 3-year survival rate was 91.2% in the recipients. GD-DTPA, a paramagnetic metal, can shorten the T1 and T2 relaxation values of surrounding protons. This decreases the signal of the liver parenchyma and brightens the biliary anatomy. It can improve the image quality of MRC and increase the diagnostic accuracy of the biliary tract classification. It is mandatory in the "donor and recipient surgery during the LDLT".

Water dynamics in microwavable par-baked soy dough evaluated during frozen storage

Par-baked bread provides convenience and quality in bakery products. Soy, in combination with its nutritional benefits, was previously shown to improve the texture of microwave-baked flatbread and par-baked flatbread due to the high hygroscopic properties of soy protein and the plasticizing effects of the added lipids. It was hypothesized that soy addition would also mitigate the changes in texture and the properties of water within par-baked flatbread during frozen storage. Flatbread was formulated with 0, 10, 20, and 26% soy ingredients (by weight of added ingredients). The dough was (partially) baked to about 75% of completion and then stored at −18°C for 14days. The dough was then thawed and analyzed for moisture content, textural properties such as hardness, and proton T1 and T2 relaxation times. Freezing increased the hardness and chewiness and decreased the springiness of par-baked wheat bread, but 10% soy bread did not show a change in chewiness, hardness, or springiness upon freezing. Two distinct water populations, in an approximate 90%–10% proportion, were defined using solution state proton NMR relaxation techniques. Increasing soy concentrations led to decreased T1 relaxation values in the most populated water state. Data suggest that the water in this par-baked system is a non-rigid solid, and that soy addition therefore increases mobility of the water. Neither T1 nor T2 relaxation values changed during frozen storage time for any of the formulations. These results indicate that soy slightly altered the texture and water properties of par-baked flatbread but these formulations were more stable during frozen storage.

Copper Modulates Aβ42 Aggregation in Model Membranes

The amyloid-beta (Aβ) peptide is associated with Alzheimer's disease (AD). Evidence suggests that Aβ interaction with neuronal cell membranes correlates strongly with neurodegeneration but understanding the molecular mechanism remains a challenge. The role of heavy metals often found in amyloid plaques from AD brain patients is another path for investigation. Our recent findings support the role of lipid membrane composition as crucial in many biological mechanisms. We observed that different lipids promote different fibril morphologies and aggregation kinetics and are now facing the following conundrum: how does copper mediate Aβ42 aggregation and how do membranes interact with Aβ42-Cu complexes. ThT fluorescence and circular dichroism showed that increasing copper concentration above equimolar ratio stabilized Aβ42 into non-oligomeric beta-sheet structures with or without the presence of lipids. 31P and 2H solid-state NMR revealed that equimolar Aβ42-Cu complexes had some effect on lipid membrane structure and dynamics while the hydrophobic core remained unperturbed and that Aβ42 peptides did not scavenge copper from the lipid headgroup. However, copper-free samples showed a net reduction in the headgroup dynamics, with the chemical shift anisotropy, T1 and T2 relaxation values strongly reduced but lacked evidence of hydrophobic core perturbations. The data supports a peripheral interaction of Aβ42 and peptide-Cu complexes with phospholipid membranes.

In vivo detection of c‐Met expression in a rat C6 glioma model

The tyrosine kinase receptor, c-Met, and its substrate, the hepatocyte growth factor (HGF), are implicated in the malignant progression of glioblastomas. In vivo detection of c-Met expression may be helpful in the diagnosis of malignant tumours. The C6 rat glioma model is a widely used intracranial brain tumour model used to study gliomas experimentally. We used a magnetic resonance imaging (MRI) molecular targeting agent to specifically tag the cell surface receptor, c-Met, with an anti-c-Met antibody (Ab) linked to biotinylated Gd (gadolinium)-DTPA (diethylene triamine penta acetic acid)-albumin in rat gliomas to detect overexpression of this antigen in vivo. The anti-c-Met probe (anti-c-Met-Gd-DTPA-albumin) was administered intravenously, and as determined by an increase in MRI signal intensity and a corresponding decrease in regional T1 relaxation values, this probe was found to detect increased expression of c-Met protein levels in C6 gliomas. In addition, specificity for the binding of the anti-c-Met contrast agent was determined by using fluorescence microscopic imaging of the biotinylated portion of the targeting agent within neoplastic and ‘normal’brain tissues following in vivo administration of the anti-c-Met probe. Controls with no Ab or with a normal rat IgG attached to the contrast agent component indicated no non-specific binding to glioma tissue. This is the first successful visualization of in vivo overexpression of c-Met in gliomas.

MR angiography of the carotid arteries and intracranial circulation: advantage of a high relaxivity contrast agent

Several studies have shown the usefulness of contrast-enhanced MR angiography (CE-MRA) for imaging the supraortic vessels, and, as a consequence, it has rapidly become a routine imaging modality. The main advantage over unenhanced techniques is the possibility to acquire larger volumes, allowing demonstration of the carotid artery from its origin to the intracranial portion. Most published studies on CE-MRA of the carotid arteries have been performed with standard Gd-based chelates whose T1 relaxivity values are similar. Recently new gadolinium chelates such as gadobenate dimeglumine (Gd-BOP-TA, MultiHance; Bracco Imaging, Milan, Italy) have been developed which have markedly higher intravascular T1 relaxivity values. When administered at an equivalent dose to that of a standard agent, these newer contrast agents produce significantly greater intravascular signal enhancement. The availability of an appropriate high-relaxivity contrast agent might also help to overcome some of the intrinsic technical problems (e. g. those related to flow) that affect time-of-flight (TOF) and phase contrast (PC) MR angiography of the intracranial vasculature. To avoid the problem of superimposition of veins, ultrafast gradient echo MRA techniques with very short TR and TE have been developed. Although the precise sequence parameters vary between manufacturers, they are basically similar. The choice between performing a time-resolved or high spatial resolution CE-MRA examination depends upon the precise clinical application. The most common applications include the study of cerebral aneurysms, arteriovenous malformations, dural arteriovenous fistulas and dural venous diseases.

T1 and T2 relaxivity of intracellular and extracellular USPIO at 1.5T and 3T clinical MR scanning

In this study we evaluated the effects of intracellular compartmentalization of the ultrasmall superparamagnetic iron oxide (USPIO) ferumoxtran-10 on its proton T1 and T2 relaxivities at 1.5 and 3T. Monocytes were labeled with ferumoxtran-10 by simple incubation. Decreasing quantities of ferumoxtran-10-labeled cells (2.5x10(7)-0.3x10(7) cells/ml) and decreasing concentrations of free ferumoxtran-10 (without cells) in Ficoll solution were evaluated with 1.5 and 3T clinical magnetic resonance (MR) scanners. Pulse sequences comprised axial spin echo (SE) sequences with multiple TRs and fixed TE and SE sequences with fixed TR and increasing TEs. Signal intensity measurements were used to calculate T1 and T2 relaxation times of all samples, assuming a monoexponential signal decay. The iron content in all samples was determined by inductively coupled plasma atomic emission spectrometry and used for calculating relaxivities. Measurements at 1.5T and 3T showed higher T1 and T2 relaxivity values of free extracellular ferumoxtran-10 as opposed to intracellularly compartmentalized ferumoxtran-10, under the evaluated conditions of homogeneously dispersed contrast agents/cells in Ficoll solution and a cell density of up to 2.5x10(7) cells/ml. At 3T, differences in T1-relaxivities between intra- and extracellular USPIO were smaller, while differences in USPIO T2-relaxivities were similar compared with 1.5T. In conclusion, cellular compartmentalization of ferumoxtran-10 changes proton relaxivity.

Comparison of Magnetic Properties of MRI Contrast Media Solutions at Different Magnetic Field Strengths

To characterize and compare commercially available contrast media (CM) for magnetic resonance imaging (MRI) in terms of their relaxivity at magnetic field strengths ranging from 0.47 T to 4.7 T at physiological temperatures in water and in plasma. Relaxivities also were quantified in whole blood at 1.5 T. Relaxivities of MRI-CM were determined by nuclear magnetic resonance (NMR) spectroscopy at 0.47 T and MRI phantom measurements at 1.5 T, 3 T, and 4.7 T, respectively. Both longitudinal (T1) and transverse relaxation times (T2) were measured by appropriate spin-echo sequences. Nuclear magnetic resonance dispersion (NMRD) profiles were also determined for all agents in water and in plasma. Significant dependencies of relaxivities on the field strength and solvents were quantified. Protein binding leads to both increased field strength and solvent dependencies and hence to significantly altered T1 relaxivity values at higher magnetic field strengths. Awareness of the field strength and solvent associated with relaxivity data is crucial for the comparison and evaluation of relaxivity values. Data observed at 0.47 T can thus be misleading and should be replaced by relaxivities measured at 1.5 T and at 3 T in plasma at physiological temperature.

NMR T1‐Relaxation Measurements on Paramagnetic Organolanthanides:An Alternative Tool for Structure Determination in Solution

Abstract1H NMR investigations were conducted on four paramagnetic organolanthanides, all bearing the tetraisopropylcyclopentadienyl ligand Cp4i (HC5iPr4) in order to verify whether or not interactions observed in the solid state are maintained in solution. In some cases variable‐temperature experiments were necessary to enhance the resolution and determine the best conditions for the study. The 1D NMR spectrum could be interpreted in every case. Complementary 2D COSY experiments allowed the full attribution of the signals. T1 (1H) relaxation values were determined for all the paramagnetic complexes at the most suitable temperature, and compared with those of the diamagnetic KCp4i. The same tendency was observed, with particular features concerning the isopropyl groups. Among the four methyl groups, one exhibits a much higher T1 value and one a much lower value; the two others are intermediate. This was interpreted as the result of a privileged conformation of the Cp4i ligand: the two α‐isopropyl groups take up a spatial orientation with one methyl group in the exo position, opposite to the metal atom, whereas the methyl groups of the two β‐isopropyl groups are equidistant from the metal atom. Whatever the nature of the metal (Nd, Sm), the oxidation state (SmII, SmIII) or the temperature (298, 363 K), this conformation is retained. The structure in solution seems to be different from that previously determined in the solid state. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2005)

Poly(vinyl alcohol) cryogel phantoms for use in ultrasound and MR imaging

Poly(vinyl alcohol) cryogel, PVA-C, is presented as a tissue-mimicking material, suitable for application in magnetic resonance (MR) imaging and ultrasound imaging. A 10% by weight poly(vinyl alcohol) in water solution was used to form PVA-C, which is solidified through a freeze–thaw process. The number of freeze–thaw cycles affects the properties of the material. The ultrasound and MR imaging characteristics were investigated using cylindrical samples of PVA-C. The speed of sound was found to range from 1520 to 1540 m s−1, and the attenuation coefficients were in the range of 0.075–0.28 dB (cm MHz)−1. T1 and T2 relaxation values were found to be 718–1034 ms and 108–175 ms, respectively. We also present applications of this material in an anthropomorphic brain phantom, a multi-volume stenosed vessel phantom and breast biopsy phantoms. Some suggestions are made for how best to handle this material in the phantom design and development process.

Preparation and in vitro evaluation of GdDOTA-(BOM)4; a novel angiographic MRI contrast agent.

A novel Gd(III) complex, GdDOTA-(BOM)4, has been prepared by a simple three-step procedure. The complex showed high T1-relaxivity values in serum albumin solutions, blood and plasma, resulting from high affinity for serum albumin. The T1-relaxivity in plasma, 67.4 s-1 mM-1 (20 MHz, 37 degrees C), makes it a promising candidate for angiographic applications of MRI.

Intrathecal Gadolinium-Enhanced MR-Cisternography: Depiction of the Subarachnoidal Space and Evaluation of Gadobenat-Dimeglumin-(Gd-BOPTA, “Multihance®”) Toxicity in an Animal Model and a Clinical Case

As other gadolinium-based contrast medias (CM) intravenously administered, gadobenate dimeglumine has proved to be well tolerated and safe (1). The application of gadolinium within the subarachnoidal space has been tested in several studies with promising results (2,3). This technique has not entered routine clinical use. Because of its particular molecular structure, GdBOPTA showes T1 relaxivity values almost twice those seen with conventional CM due to its weak interactions with macromolecules (4). This characteristic leads to improved results in diagnostics and a lower required concentration. Encouraged by these results, Gd-BOPTA was used for this study to determine the best concentration of gadobenate dimeglumine in the cerebrospinal fluid and to evaluate the diagnostic value of MR-Myelography with intrathecal gadobenate dimeglumine. Additionally, the presence of toxic side effects to the CNS were investigated. Due to certain clinical circumstances, one patient received gadobenate dimeglumine by lumbar puncture to evaluate a spinal cyst. MATERIALS AND METHODS

Textural Stability of Intermediate‐Moisture Extrudates: Effects of Formulation

ABSTRACTEffects of formulation on the textural stability of intermediate‐moisture, flour‐based, “jerky”‐type extrudates were assessed. Potato‐based extrudates containing various particulate‐meat concentrations and different plasticizers (sucrose, fructose, glycerol, and glucose) were produced and subjected to accelerated storage for three weeks. The elastic modulus of the samples was measured before storage and then weekly. The relative fluidity and moisture mobility of the specimens were assessed by dynamic mechanical spectrometry (DMS), electron spin resonance (ESR), and nuclear magnetic resonance (NMR). Samples were also evaluated by fluorometry and X‐ray diffraction to determine the extent of browning reaction and degree of molecular ordering, respectively. While elastic modulus increased appreciably during storage, firming was progressively reduced by entrained meat content and also by plasticizers, especially glycerol; plasticized and meat‐containing samples had correspondingly lower tan δ peak temperatures as measured by DMS. Textural results were also in keeping with fluidity and local viscosity as assessed by ESR measurements. NMR T1 relaxation values, reflecting moisture mobility, increased during storage. Diffraction spectra were consistent with published observations of hydrated starch, suggesting that water may have been released due to increased association of proteinaceous constituents. Fluorescence measurements confirmed moderate Maillard browning in all samples and significant chlorogenic browning in glucose‐containing samples, although these effects were unrelated to degree of firming. It was concluded that textural stability was optimized by interruption of the matrix by dispersed meat or by plasticization by low molecular weight constituents.

Dysprosium-DOTA-PAMAM dendrimers as macromolecular T2 contrast agents. Preparation and relaxometry.

The authors have investigated dysprosium [Dy]-DOTA-PAMAM, generation 5 (G = 5) dendrimers as a possible new class of macromolecular T2 contrast agents. The use of DOTA provides a metal complex with greater stability than can be achieved using DTPA as ligand, an important factor in the design of blood pool agents with long half-lives. Generation 5 ammonia-core PAMAM dendrimers were linked to the bifunctional ligand p-SCN-Bz-DOTA. After determination of the number of conjugated DOTA molecules by 1H nuclear magnetic resonance, Dy3+ was titrated at a 90% molar ratio. For comparison, single ionic chelates of Dy-DTPA and Dy-DOTA also were prepared. Using a variable field relaxometer, T1 and T2 relaxation times were measured at 13 different field strengths from 0.05 to 1.5 T and temperatures of 3, 10, 20 and 37 degrees C. The synthesis resulted in a preparation with 76 DOTA and 68 Dy3+ ions per dendrimer molecule. The T1 relaxivity values for Dy-DTPA, Dy-DOTA, and the Dy-DOTA-based dendrimer all were independent of field strength, with values between 0.12 and 0.20 mM-1 sec-1. At lower fields (0.05-0.1 T), 1/T2 was identical to 1/T1. At higher fields, however, 1/T2 increased quadratically with field strength, with a strong dependence on temperature. The field-dependent component of 1/T2 was up to three times higher for the Dy-DOTA-based dendrimer compared with the single chelate molecules, with coefficients of 0.37 to 0.03 sec-1/Tesla2 for T = 3 to 37 degrees C. The results are interpreted with the "inner sphere" theory of susceptibility effects (Curie spin relaxation). The large temperature dependence suggests that the dominant mechanism of relaxation is the contact interaction effect, with the proton residence time as the primary time constant. This largely unexplored relaxation mechanism has the potential to create a new class of T2-selective contrast agents.

Multinuclear NMR Study of Cationic Binuclear Mono- and Trihydrido Platinum (II) Bisphosphine Complexes

Abstract Magnitude and signs of J(Pt,Pt), J(Pt,P), J(Pt,H) and J(P,P) scalar couplings and hydride T1 relaxation values characteristic for chelating systems are discussed.

Precise Determination of T1 Relaxation Values by a Method in Which Pairs of Nonequilibrium Magnetizations Are Measured across a Constant Relaxation Period

The constant-relaxation-period (CREPE) method for spin-lattice (T1) relaxation measurement presented here offers a significant improvement over other methods currently in use. The CREPE approach involves the measurement of both the initial and the final magnetizations flanking a constant relaxation period; the relaxation rates can be extracted from the data by linear regression without the necessity of additional parameters to correct for off-resonance effects or errors in pulse-width settings. Computer simulations used to compare the accuracy of T1 measurements made by the new method with those by the fast inversion-recovery (FIR) approach (generally considered to be the best general method for T1 measurements) showed that the CREPE method provides about a twofold reduction in errors over a wide range of signal-to-noise in the input data. Experimental data collected by the two approaches showed that the CREPE method provides the same precision in T1 values as the FIR method with one-fourth the data-collection time.