Hepatobiliary Imaging, An Issue of Magnetic Resonance Imaging Clinics of North America (eBook)

Peter S. Liu (Autor)

eBook Download: PDF | EPUB

2014 | 1. Auflage
348 Seiten
Elsevier Health Sciences (Verlag)
978-0-323-32036-8 (ISBN)

Infos

This issue, edited by Drs. Peter Liu and Richard Abramson, will comprehensively review imaging of the hepatobiliary system. Articles will include: Hepatic MRI Techniques, Optimization, and Artifacts, MR Contrast Agents for Liver Imaging, Focal Liver Lesion Characterization in Noncirrhotic Patients: An MR Approach, MRI in Cirrhosis and Hepatocellular Carcinoma, Understanding LI-RADS: A Primer for Practical Use, MRI of the Liver after Locoregional and Systemic Therapy, Diffusion Weighted Imaging of the Liver: Techniques and Applications, Hepatic Iron and Fat Quantification Techniques, Perfusion Imaging in Liver MRI, MR Elastography, Treatment Planning Before Hepatobiliary Surgery: Clinical and Imaging Considerations, MRI/MRCP of Benign and Malignant Biliary Conditions, and more!

Textauszug

Hepatic MR Imaging Techniques, Optimization, and Artifacts

Flavius F. Guglielmo, MDa∗[e-mail], Donald G. Mitchell, MDa, Christopher G. Roth, MDb and Sandeep Deshmukh, MDa,     aDepartment of Radiology, Thomas Jefferson University, 132 South 10th Street, Philadelphia, PA 19107, USA; bDepartment of Radiology, Methodist Hospital, Thomas Jefferson University, 2301 South Broad Street, Philadelphia, PA 19148, USA

∗Corresponding author.

This article describes a basic 1.5-T hepatic magnetic resonance (MR) imaging protocol, strategies for optimizing pulse sequences while managing artifacts, the proper timing of postgadolinium 3-dimensional gradient echo sequences, and an effective order of performing pulse sequences with the goal of creating an efficient and high-quality hepatic MR imaging examination. The authors have implemented this general approach on General Electric, Philips, and Siemens clinical scanners.

Keywords

Hepatic MRI protocol

Hepatic MRI sequence optimization

Minimizing hepatic MRI artifacts

Extracellular space contrast agents

Hepatocyte-specific contrast agents

Postgadolinium pulse sequences

Diffusion-weighted imaging

Parallel imaging techniques

Key points

• The foundation for hepatic magnetic resonance imaging (MRI) includes T1-weighted images (including chemical shift imaging), T2-weighted images, fat suppression, and in most cases, contrast-enhanced images. Complementary techniques include balanced steady-state free precession and diffusion-weighted imaging.

• To maximize the clinical utility of hepatic MRI exams, each pulse sequence must be optimized while minimizing artifacts that interfere with interpretation.

• An understanding of the different types of gadolinium-based contrast agents (GBCAs) and the most important characteristics of each agent is needed to improve the diagnostic yield of the hepatic MRI exam.

• T1-weighted fat-suppressed gradient echo (GRE) sequences must be properly timed to account for the type of GBCA used while adjusting imaging parameters to maximize image quality.

• Most pulse sequences can be effectively performed after administering gadolinium. Exceptions include dual GRE sequences, single-shot fast-spin echo heavily T2-weighted sequences, high-resolution 3-dimensional MR cholangiopancreatography sequences obtained after gadoxetate disodium administration, and short TI inversion recovery sequences obtained after administration of extracellular space contrast agents.

Introduction

Compared with other hepatic imaging modalities including ultrasonography, contrast-enhanced ultrasonography, computed tomography (CT), and positron emission tomography-CT, magnetic resonance imaging (MRI) offers more comprehensive evaluation of the liver, establishing in many cases an accurate tissue diagnosis. To fully harness the power of MRI, the techniques must be optimized while minimizing artifacts interfering with interpretation. The foundation for hepatic MRI includes T1-weighted images (including chemical shift imaging), T2-weighted images, fat suppression, and in most cases, contrast-enhanced images. Complementary imaging sequences include balanced steady state free precession (BSSFP) and diffusion weighted imaging (DWI). Pregadolinium and postgadolinium fat-suppressed T1-weighted 3D gradient echo (GRE) sequences are generally the workhorse of the examination and must be properly timed to account for the type of gadolinium based contrast agent (GBCA) while adjusting imaging parameters to maximize image quality. Finally, certain pulse sequences can be performed after gadolinium administration to improve examination efficiency while maximizing the diversity of pulse sequences.

This article describes a basic 1.5-T hepatic MRI protocol, strategies for optimizing pulse sequences while managing artifacts, the proper timing of postgadolinium 3D GRE sequences, and an effective order of performing pulse sequences with the goal of creating an efficient and high-quality hepatic MRI examination. The authors have implemented this general approach on Philips (Philips Medical Systems, Best, Netherlands), Siemens (Siemens Medical Solutions, Erlangen, Germany) and General Electric (GE Medical Systems, Milwaukee, Wisconsin, USA) clinical scanners.

The basic hepatic MR imaging examination

In clinical practice, the typical hepatic MR imaging examination (Table 1) includes comprehensive imaging of other abdominal viscera, although generally, the MR imaging protocol is optimized for evaluation of the liver. For gadolinium-enhanced studies, intravenous gadolinium should be administered as early as possible during the examination. Then, if the examination is prematurely terminated for any reason, gadolinium-enhanced images, which are often the most important sequences for lesion characterization, will have already been completed. This protocol is achievable because most sequences, except dual GRE (in and out of phase) sequences, single shot fast spin echo (SSFSE) heavily T2-weighted sequences, high-resolution 3D MR cholangiopancreatography (MRCP) sequences obtained after gadoxetate disodium administration, and short TI inversion recovery (STIR) sequences obtained after administration of extracellular space contrast agents (ECSAs), are not adversely affected by gadolinium and can be performed after gadolinium administration. A torso phased array coil should be used for all sequences, including localizer images.

Table 1

Hepatic MR imaging pulse sequences and parameters (1.5 T)

Protocol when using an extracellular space agent (ECSA):

SSFSE survey

3 plane

48

320 × 192

0

8/0

Min

80

90

No

SSFSE (Heavily T2WI)

Coronal

44

256 × 192

1.7

5/0

Min

180

90

No

SSFSE (heavily T2WI)

Axial

38

256 × 192

2

5/0

Min

180

90

No

Dual GRE in and out of phase

Axial

38

256 × 192

2

7/0.5

265

2.1/4.4

90

No

T1-weighted 3D spoiled GRE (pre-contrast double arterial, & portal venous phase)

Axial

42

320 × 224

1.8

4.4/2.2

Min

Min

12

Yes

Moderately T2W FS

Axial

40

256 × 192

2

7.5/0.5

2300

84

90

Yes

T1-weighted 3D spoiled GRE (delayed phasea)

Axial

42

320 × 224

1.8

4.4/2.2

Min

Min

15

Yes

BSSFP

Axial

38

192 × 288

2

5/0

Min

Min

70

Yes

Radial Slab 2D MRCPb

Coronal

26

288 × 256

0

40/0

2666

1096

90

Yes

Diffusion

Axial

36

128 × 160

2

6/1

7000

73

90

Yes

3D MRCPc

Coronal

38

320 × 320

2

1.4/0.7

3750

847

90

Yes

Additional postgadolinium pulse sequences and parameters when using gadoxetate disodium instead of an ECSA:

T1-weighted 3D spoiled GRE (hepatobiliary phase)

Axial

40

288 × 160

1.8

5/2.5

Min

Min

25–30d

Yes

T1-weighted 3D spoiled GRE (hepatobiliary phase)

Coronal

42

288 × 160

0

5/2.5

Min

Min

25–30d

Yes

Abbreviations: BH, breath-hold; FOV, field of view; FS, fat suppression; Min, minimum; PAF, parallel imaging acquisition factor; T2W, T2 weighted; T2WI, T2-wieghted imaging; TE, echo time; TR, repetition time; 2D, 2-dimensional.

aDelayed phase is called late dynamic phase when using gadoxetate disodium.

bRadial slab 2D MRCP can be performed if it is completed within 5 minutes of gadoxetate disodium injection.

c3D MRCP should be performed before gadoxetate disodium...

Produkt-Details

• Erscheint lt. Verlag: 28.8.2014
• Sprache: englisch
• Themenwelt: Medizin / Pharmazie ► Gesundheitsfachberufe
• Themenwelt: Medizinische Fachgebiete ► Radiologie / Bildgebende Verfahren ► Radiologie
• ISBN-10: 0-323-32036-8 / 0323320368
• ISBN-13: 978-0-323-32036-8 / 9780323320368