A modified signal intensity equation of carr-purcell-meiboom-gill pulse sequence for MR imaging.

Yamada, S.; Matsuzawa, Taiju; Yamada, Kenji; Yoshioka, Seiro; Ono, Sachiko; Hishinuma, T

doi:10.1620/tjem.158.203

Cited by 8 publications

(7 citation statements)

References 11 publications

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“…Having shown that compartmentalization affects T 1 as well as T 2 relaxation times, both parameters need to be taken into account. SI for an SE sequence is described by

normalS normalI = M_{z} ((), 1 - e^{prefix- T R true/ T 1}) e^{prefix- T E true/ T 2}

…”

Section: Resultsmentioning

confidence: 99%

Compartmentalization of Gd liposomes: the quenching effect explained

Guenoun

Doeswijk

Krestin

et al. 2015

Contrast Media & Molecular

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Cationic liposomes carrying high [Gd] can be used as efficient cell-labeling agents. In a compartmentalized state, Gd can cause signal loss (relaxivity quenching). The contributions of liposomal [Gd], size and compartmentalization state to relaxivity quenching were assessed. The dependency of signal intensity (SI) on intraliposomal [Gd] was assessed comparing three different [Gd] (0.3, 0.6 and 1.0 M Gd) in both small (80 nm) and large (120 nm) cationic liposomes. In addition, five compartmentalization states were compared: free Gd, intact Gd liposomes, ruptured Gd liposomes, Gd liposomes in intact cells and Gd liposomes in ruptured cells (simulating cell death). Gd also causes R2 effects, which is often overlooked. Therefore, both R1 and R2 relaxation rates of a dilution range were measured by T1 and T2 mapping on a 7 T clinical scanner. Less is more. As the unidirectional water efflux rate (outbound across the liposome membrane, κle) is proportional to the surface:volume ratio, smaller liposomes yielded a consistently higher R1 than larger liposomes. For equal voxel [Gd] less concentrated liposomes (0.3 M Gd) yielded higher R1/R2 ratio because of the higher extraliposomal water fraction (vl ). Gd exhibits a dualistic behavior: from hypointensity to hyperintensity to hypointensity, with decreasing [Gd]. Regarding compartmentalization, fewer membrane barriers means a higher R1 /R2 ratio. Gd liposomes exhibit a versatile contrast behavior, dependent on the compartmentalization state, liposomal size, intraliposomal [Gd] and liposome number. Both R1 and R2 effects contribute to this. The versatility allows one to tailor the optimal liposomal formulation to desired goals in cell labeling and tracking.

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“…Having shown that compartmentalization affects T 1 as well as T 2 relaxation times, both parameters need to be taken into account. SI for an SE sequence is described by

normalS normalI = M_{z} ((), 1 - e^{prefix- T R true/ T 1}) e^{prefix- T E true/ T 2}

…”

Section: Resultsmentioning

confidence: 99%

Compartmentalization of Gd liposomes: the quenching effect explained

Guenoun

Doeswijk

Krestin

et al. 2015

Contrast Media & Molecular

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“…The accuracy of T2 is very high in CPMG pulse sequence (Schneiders et al 1983; Lee and Riederer 1986;Yamada et al 1989), and the signal intensity equation for CPMG pulse sequence proves that T2 is not influenced by the length of recovery time (Yamada et al 1989). Therefore, T2 shortening in the timecour-se study seemed to reflect the dynamics of Gd-DTPA, although T2 was calculated from the images with different Trs.…”

Section: Discussionmentioning

confidence: 99%

“…Regions of interest (ROT) containing 4 pixels were settled at the tumor lesion whether it showed enhancement or not. T2 at each Tr was calculated by the methods of Schneiders et al (1983) and Lee and Riederer (1986), and T1 by the two-point method of Yamada et al (1989). Ten ROIs' data in each case were averaged and Student's t-test was used for the statistics.…”

Section: Methodsmentioning

confidence: 99%

T1 and T2 relaxation times on gadolinium-diethylenetriaminepentaacetic acid enhanced magnetic resonance images of brain tumors.

Yamada¹,

Kubota²,

Yamada³

et al. 1990

Tohoku J. Exp. Med.

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MRI of brain tumors was performed with CPMG pulse sequence, and T1 and T2 relaxation times were measured before and after the administration of 0.1 mmol/kg Gd-DTPA. T1 and T2 became significantly shorter than before with the T1 shortening being about twice the T2's. Three types of T2 shortening were classified by the difference in the intra-tumoral transport of Gd-DTPA in the time-course study after the administration. Transportal activity of Gd-DTPA seemed to be reflected by the physiologic viability of tumor suggested by pre-contrast T2. magnetic resonance imaging ; brain tumor ; gadolinium-DTPA ; Carr-Purcell-Meiboom-Gill pulse sequence ; relaxation time A paramagnetic contrast agent, gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA), has successfully increased the sensitivity for detection of cerebral abnormalities in magnetic resonance (MR) images, and given the characterization of pathologic conditions (Carr et al. 1984;Felix et al. 1985;Graif et al. 1985). According to the clinical use of the contrast agent for the enhancement in MR images, quantitative analysis is desirable to consider the relation between Gd-DTPA enhancement and patho-physiologic tissue characteristics (Graif et al. 1985). In this study, the contrast enhancement of brain tumors induced by Gd-DTPA was quantitatively evaluated by the changes of T1 and T2 relaxation times.

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“…After contrast, shortening of T1 relaxation time was noted in most of the tumors (17). Analyzing the percentage of T1 relaxation after contrast enhancement, it is evident that it is at a minimum in white matter (0.15 to 12.84%, mean-3.3%) and maximum (79%, mean) in case of tumors (23).…”

Section: Analysis Of T1 Relaxationmentioning

confidence: 92%

Simulation Of Contrast Enhancement Of Various Brain Lesions (Without Iv Gadolinium) By Using The Neural Network

2012

IJRA

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PURPOSE:To produce an enhancement-like effect of the brain lesions of MRI images mathematically, without intravenous injection of contrast.INTRODUCTION:To improve the visibility of internal body structures, MRI contrast agents are used. Gadolinium (Gd 3+), a paramagnetic substance, is the most commonly used compound for contrast enhancement. Gd is introduced into the blood stream for enhancement of brain tumors and various lesions depending upon the degradation of the blood-brain barrier. Due to their hydrophilic character, gadolinium chelates do not pass the blood-brain barrier. Contrast (Gd) mediated nephropathy (CMN) and systemic fibrosis are two notorious, irreversible complications.MATERIALS AND METHODS: A multi-slice EPI IR sequence was used to assess T1 relaxation times of various brain lesions and brain tumors before and after administration of gadolinium. T1 relaxation time and signal intensity with corresponding gray scale values (out of 256 shades) of various brain lesions before and after IV contrast were tabulated. A statistical relationship was determined for the magnitude of changes in the T1 values of brain tumors before and after the contrast material was added. Enhancement-like effects of the lesions could be reproduced mathematically with the help of neural networks without the IV contrast injection. With the help of Kmean clustering, the data were classified. A mapping function was generated that corresponded between these independent components and the cross-sectional data by using the neural network after training the network with a sample dataset. The training sample for the network was selected using K-mean clustering. A mapping of the lesion was done overlaid on the T1 weighted image.CONCLUSION: An attempt was successfully made to enhance various brain lesions statistically utilizing neural networks and without using IV contrast.

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A modified signal intensity equation of carr-purcell-meiboom-gill pulse sequence for MR imaging.

Cited by 8 publications

References 11 publications

Compartmentalization of Gd liposomes: the quenching effect explained

Compartmentalization of Gd liposomes: the quenching effect explained

T1 and T2 relaxation times on gadolinium-diethylenetriaminepentaacetic acid enhanced magnetic resonance images of brain tumors.

Simulation Of Contrast Enhancement Of Various Brain Lesions (Without Iv Gadolinium) By Using The Neural Network

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