Effects of inversion and saturation times on relationships between contrast agent concentrations and signal intensities of T 1-weighted magnetic resonance images

Abstract

The present study was an attempt to investigate the effect of variation of inversion time (T (I)) and saturation time (T (S)) on the linear relationship between contrast agent concentration and signal intensity (SI) on Turbo Fast Low Angle Shot (TurboFLASH) T (1)-weighted images in MRI. For this purpose, inversion recovery (IR) and saturation recovery (SR) sequences (Center out Phase-Encoding acquisition) were used. A phantom was designed to hold 25 vials which contained either different (between 0 and 19.77 mmol/L) or constant (1.20 mmol/L) concentrations of contrast agent. The vials of constant concentration were used for the measurement of coil non-uniformity, which was normalized to give a correction factor. The vials of different concentrations were used to measure the SI by using different sequences and different T (I) and T (S) values. To calculate the corrected SI for different concentrations, we multiplied the SI of each vial by its correction factor. The relationships between the corrected SI and the concentration [were evaluated], where the threshold of (R (2) = 0.95 and 0.99) was maintained. This study shows that different sequences and different T (I) and T (S) values can have an effect on the correlation between the SI and concentration. Regardless of the values of T (I), T (S), and the different IR and SR sequences chosen, the linear relationship between the SI and concentration was about twice that previously reported (i.e., 0.8 mmol/L, R (2) = 0.95).

Molecular Imaging in Cardiovascular Diseases

“…Thus these bonds belong to "positive" MRI contrast agents; their effect is expressed as an increase of signal intensity on T1-weighted images. It has been shown that for T1-weighted gradient echo sequences, signal intensity across a wide concentration range is proportional to the local contrast agent concentration [29,30]. If, however, the local contrast agent concentration is very high, a noticeably reduced T2 relaxation time additionally occurs, [29,30] together with a deviation from linear signal behavior.…”

“…It has been shown that for T1-weighted gradient echo sequences, signal intensity across a wide concentration range is proportional to the local contrast agent concentration [29,30]. If, however, the local contrast agent concentration is very high, a noticeably reduced T2 relaxation time additionally occurs, [29,30] together with a deviation from linear signal behavior. Depending upon the composition of the contrast medium or molecular probe, the relaxation effect additionally varies with the strength of the external magnetic field.…”

Effect of concentration of contrast agent on the inflow effect for measuring absolute perfusion by use of inversion recovery T1-weighted TurboFLASH images

“…The standard inversion recovery sequence, which is dependent on the inversion time (T I ) and repetition time (T R ), is described by the following equation [4,5]:…”

“…The first part is used for calibrating flow, which, in turn, is divided into three sections (V1, V2, and V3) to produce three flows in the ratio 1:2:4. The second part contains three branches (A, B, and C) of the main TYGON tube (D) which is dependent on the flow rate, can affect the SI, this effect should be considered for measuring the organ blood flow [4,9].…”

“…Previous investigators tried to solve this problem by changing the image parameters and finding the maximum concentration of contrast agent which leads to a maximum SI [3][4][5][6]. The SI at high concentration leads to a better signal-to-noise ratio on an image.…”