Synthetic MRI: an old concept becomes practical
Christina Andica1, Akifumi Hagiwara1,2, Misaki Nakazawa1,3, Masaaki Hori1, Saori Shiota1, Mariko Yoshida1, Kanako Sato1, Yuko Takahashi1, Kanako Kumamaru1, Michimasa Suzuki1, Atsushi Nakanishi1, Kouhei Tsuruta1,3, Ryo Ueda1,3, and Shigeki Aoki1

1Department of Radiology, Juntendo University School of Medicine, Tokyo, Japan, 2Department of Radiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan, 3Department of Radiological Sciences, Graduate School of Human Health Sciences, Tokyo Metropolitan University, Tokyo, Japan

Synopsis

Synthetic magnetic resonance imaging (MRI) is a technique which can be used to synthesize contrast-weighted images based on quantification of the longitudinal T1 relaxation, the transverse T2 relaxation, the proton density (PD), and the amplitude of the local radio frequency B1 field. Synthetic MRI images were useful in the evaluation of brain disorders. With Synthetic MRI, echo time (TE), repetition time (TR), and inversion time (TI) of the contrast-weighted image can be freely adjusted retrospectively to optimize image quality. Limitation of synthetic MRI is the partial volume effect.

Purpose

Synthetic magnetic resonance imaging (MRI) is a technique which can be used to synthesize contrast-weighted images based on quantification of the longitudinal T1 relaxation, the transverse T2 relaxation, the proton density (PD), and the amplitude of the local radio frequency B1 field.1 Echo time (TE), repetition time (TR), and inversion time (TI) of the contrast-weighted image can be freely adjusted retrospectively. The purpose of this poster is to show the basic principles of synthetic MRI and presents the clinical applications of synthetic MRI in the evaluation of brain disorders.

Outline of Content

The exhibit will consist of four sections:

1. The basic principles of synthetic MRI.1

2. Clinical settings of our institute.

3. Limitation of synthetic MRI: partial volume effect, especially for fluid inversion recovery (FLAIR) images.

4. The clinical applications of synthetic MRI on:

a. Meningeal enhancement:

- Using DIR to suppress the signals from brain parenchyma and fat in the bone marrow to show leptomeningeal and dural enhancement in a patient with Sturge-Weber syndrome.2

- Using contrast enhanced synthetic FLAIR image to show meningeal carcinomatosis.

b. Brain metastases: contribution of brain synthetic MRI to the detection of brain metastases, a comparation between contrast enhanced (CE) T1-weighted inversion-recovery (T1IR) image, CE synthetic T1-weighted image, and conventional T1IR image.

c. Pediatric brains: usefulness of synthetic MRI in showing increased myelination in an infant with Sturge-Weber syndrome.3-6

d. Other diseases: using double inversion recovery (DIR) and phase sensitive inversion recovery (PSIR) to detect cortical lesions in multiple sclerosis7 and etc.

Summary

Synthetic MRI images were useful in the evaluation of brain disorders. With Synthetic MRI, the contrast can be adjusted after the image has been acquired by manipulating TR, TE, and TI to optimize image quality. Limitation of synthetic MRI is the partial volume effect.

Acknowledgements

No acknowledgement found.

References

1.Warntjes JB, Leinhard OD, West J, Lundberg P. Rapid magnetic resonance quantification on the brain: Optimization for clinical usage. Magn Reson Med 2008;60:320-9.

2.Hagiwara A, Nakazawa M, Andica C, Tsuruta K, Takano N, Hori M, et al. Dural Enhancement in a Patient with Sturge-Weber Syndrome Revealed by Double Inversion Recovery Image Using Synthetic MRI. Magnetic Resonance in Medical Sciences (Epub ahead of print).

3.Barkovich AJ. Pediatric Neuroimaging. Philadelphia: Lippincott Williams & Wilkins; 2005.

4.Adamsbaum C, Pinton F, Rolland Y, Chiron C, Dulac O, Kalifa G. Accelerated myelination in early Sturge-Weber syndrome: MRI-SPECT correlations. Pediatr Radiol 1996;26(11):759-62.

5.George U, Rathore S, Nittala P. MR demonstration of accelerated myelination in early Sturge-Weber syndrome. Neurol India 2010;58:336-7.

6.Saunders DE, Thompson C, Gunny R, Jones R, Cox T, Chong WK. Magnetic resonance imaging protocols for paediatric neuroradiology. Pediatr Radiol 2007;37:789-797.

7.Nelson F, Poonawalla AH, Hou P, Huang F, Wolinsky JS, Narayana PA. Improved Identification of Intracortical Lesions in Multiple Sclerosis with Phase-Sensitive Inversion Recovery in Combination with Fast Double Inversion Recovery MR Imaging. AJNR Am J Neuroradiol 2007;28:1645-49.

Figures

Figure 1. Quantitative maps; (a) PD Map, (b) T1 Map, (c) T2 Map, (d) R1 Map, (e) R2 Map.

Figure 2. Synthetic MR; (a) PD-WI, (b) T1-WI, (c) T2-WI, (d) DIR image, (e) PSIR image, (f) T2-FLAIR image and conventional MR; (g) T2-FLAIR image.

Figure 3. A patient with SWS. (a) CE synthetic DIR image shows leptomeningeal and dural enhancement, (b) CE synthetic FLAIR image only shows leptomeningeal enhancement.

Figure 4. 4-months-old patients with SWS; (a) CE synthetic DIR images shows leptomeningeal angiomatosis on the right hemisphere. On this side “accelerated myelination” is well seen on (b) synthetic T2-WI with longer TR and TE and (c) synthetic DIR images compared to (d) conventional T2-WI.

Figure 5. The quantitative T2 map; T1, T2, and PD values (orange box) on the “accelerated myelination” side (right hemisphere) were decreased.

Figure 6. 43-year-old patient with multiple sclerosis; Synthetic (a) DIR image and (b) PSIR image are better than (c) synthetic T1-WI, (d) synthetic T2-FLAIR image, and (e) conventional T2-FLAIR image in showing a lesion (arrows) on right pons (1) and intra-cortical lesion in the right frontal lobe (2).



Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)
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