Simultaneous acquisition of high-contrast and quantitative liver T1 images using 3D phase-sensitive inversion recovery: a feasibility study

Quantitative evaluation of focal liver lesions with T1 mapping using a phase-sensitive inversion recovery sequence on gadoxetic acid-enhanced MRI

Purpose

To determine the usefulness of T1 values measured using a phase-sensitive inversion recovery (PSIR) sequence for the diagnosis of focal liver lesions.

Method

The study enrolled 87 patients who underwent gadoxetic acid-enhanced magnetic resonance imaging (MRI) for assessment of 38 hepatocellular carcinomas, 33 hepatic hemangiomas, 30 metastatic liver tumors, and 14 hepatic cysts. PSIR was performed before and 15 min after contrast agent administration, and then the respective T1 values were measured and the T1 reduction rate was calculated. Wilcoxon matched-pairs signed-rank test was used to compare T1 values pre- and post-contrast administration in each tumor. The Kruskal-Wallis test and Dunn's post-hoc test were used to compare T1 values among all tumors pre- and post-contrast administration and the T1 reduction rate among all tumors.

Results

The T1 values measured before and after contrast enhancement were 1056 ± 292 ms and 724 ± 199 ms for hepatocellular carcinoma, 1757 ± 723 ms and 1033 ± 406 ms for metastatic liver tumor, 2524 ± 908 ms and 1071 ± 390 ms for hepatic hemangioma, and 3793 ± 207 ms and 3671 ± 241 ms for liver cysts, respectively. The T1 values obtained before and after contrast administration showed significant differences for all tumors except liver cysts (P <  0.0001). T1 reduction rate was not significantly different between hepatocellular carcinoma and metastatic liver tumor, but was significantly different among other tumors (P <  0.05).

Conclusions

T1 mapping using the PSIR sequence is useful to differentiate focal liver lesions.

[Method for Quantitative Evaluation of the Substantia Nigra Using Phase-sensitive Inversion Recovery in 1.5 T Magnetic Resonance Imaging]

PURPOSE

Parkinson's disease is a neurodegenerative disease with movement disorders caused by degeneration of the substantia nigra (SN) in the midbrain. Magnetic resonance imaging (MRI) is used to exclude similar diseases. Recently, neuro-melanin imaging (NMI) has been proposed as an imaging method for evaluating the SN. However, the evaluation of the image using this is qualitative, and normal SN cannot be visualized at 1.5 T. This study aimed to investigate whether the SN can be quantitatively evaluated by using phase-sensitive inversion recovery (PSIR) at 1.5 T.

METHOD

The phantom was imaged by PSIR and the accuracy of T₁ value was verified. Next, the healthy volunteers were imaged by PSIR, and the T₁ value and area of the SN were measured.

RESULT

As a result of the phantom study, the difference of the T₁value between PSIR and inversion recovery spin-echo in the range of the T₁ value the SN and the cerebral peduncle (500 to 1000 ms) was lesser than ±10%. The difference between the average of T₁ values of the SN measured by PSIR and the previously reported T₁ values of the SN was about 1.1%. Furthermore, the average of the area of the SN measured by PSIR was measured independently of imaging parameters by using the T₁ value as a reference.

CONCLUSION

These results indicate the possibility of a quantitative evaluation of the SN by measuring its area and T₁ value by using PSIR at 1.5 T.

Utility of Stack-of-stars Acquisition for Hepatobiliary Phase Imaging without Breath-holding

Purpose:

Post-contrast liver magnetic resonance imaging is typically performed with breath-hold 3D gradient echo sequences. However, breath-holding for >10 s is difficult for some patients. In this study, we compared the quality of hepatobiliary phase (HBP) imaging without breath-holding using the prototype pulse sequences stack-of-stars liver acquisition with volume acceleration (LAVA) (LAVA Star) with or without navigator echoes (LAVA Star_navi+ and LAVA Star_navi−) and Cartesian LAVA with navigator echoes (Cartesian LAVA_navi+).

Methods:

Seventy-two patients were included in this single-center, retrospective, cross-sectional study. HBP imaging using the three LAVA sequences (Cartesian LAVA_navi+, LAVA Star_navi−, and LAVA Star_navi+) without breath-holding was performed for all patients using a 3T magnetic resonance system. Two independent radiologists qualitatively analyzed (overall image quality, liver edge sharpness, hepatic vein clarity, streak artifacts, and respiratory motion/pulsation artifacts) HBP images taken by the three sequences using a five-point scale. Quantitative evaluations were also performed by calculating the liver-to-spleen, -lesion, and -portal vein (PV) signal intensity ratios. The results were compared between the three sequences using the Friedman test.

Results:

LAVA Star_navi+ showed the best image quality and hepatic vein clarity (P < 0.0001). LAVA Star_navi− showed the lowest image quality (P < 0.0001–0.0106). LAVA Star_navi+ images showed fewer streak artifacts than LAVA Star_navi− images (P < 0.0001), while Cartesian LAVA_navi+ images showed no streak artifacts. Cartesian LAVA_navi+ images showed stronger respiratory motion/pulsation artifacts than the others (P < 0.0001). LAVA Star_navi− images showed the highest liver-to-spleen ratios (P < 0.0001–0.0005). Cartesian LAVA_navi+ images showed the lowest liver-to-lesion and -PV ratios (P < 0.0001–0.0108).

Conclusion:

In terms of image quality, the combination of stack-of-stars acquisition and navigator echoes is the best for HBP imaging without breath-holding.

Quantitative T1 and T2* carotid atherosclerotic plaque imaging using a three-dimensional multi-echo phase-sensitive inversion recovery sequence: a feasibility study

Magnetic resonance imaging (MRI) is widely used to detect carotid atherosclerotic plaques. Although it is important to evaluate vulnerable carotid plaques containing lipids and intra-plaque hemorrhages (IPHs) using T₁-weighted images, the image contrast changes depending on the imaging settings. Moreover, to distinguish between a thrombus and a hemorrhage, it is useful to evaluate the iron content of the plaque using both T₁-weighted and T₂*-weighted images. Therefore, a quantitative evaluation of carotid atherosclerotic plaques using T₁ and T₂* values may be necessary for the accurate evaluation of plaque components. The purpose of this study was to determine whether the multi-echo phase-sensitive inversion recovery (mPSIR) sequence can improve T₁ contrast while simultaneously providing accurate T₁ and T₂* values of an IPH. T₁ and T₂* values measured using mPSIR were compared to values from conventional methods in phantom and in vivo studies. In the phantom study, the T₁ and T₂* values estimated using mPSIR were linearly correlated with those of conventional methods. In the in vivo study, mPSIR demonstrated higher T₁ contrast between the IPH phantom and sternocleidomastoid muscle than the conventional method. Moreover, the T₁ and T₂* values of the blood vessel wall and sternocleidomastoid muscle estimated using mPSIR were correlated with values measured by conventional methods and with values reported previously. The mPSIR sequence improved T₁ contrast while simultaneously providing accurate T₁ and T₂* values of the neck region. Although further study is required to evaluate the clinical utility, mPSIR may improve carotid atherosclerotic plaque detection and provide detailed information about plaque components.