Adult Body MR, An Issue of Radiologic Clinics of North America, E-Book
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"I would strongly recommend this book to any radiologist or radiographer with an interest in abdomino-pelvic MRI. It will become a recommended text on the reading list of my Medical Magnetic Resonance Maters Programme." Reviewed by: Paul Bland, Senior Lecture and Postgraduate Diagnostic Radiography Programme Director, City University London, Nov 2014
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Content
2 - Adult Body MR [Seite 2]
3 - copyright [Seite copyright]
- 3 [Seite 3]
4 - Contributors [Seite 4]
5 - Contents [Seite 6]
6 - Radiologic Clinics Of North America [Seite Radiologic Clinics Of North America]
- 11 [Seite 11]
7 - Preface [Seite 12]
8 - Body MR Imaging [Seite 14]
8.1 - Key points [Seite 14]
8.2 - Introduction [Seite 14]
8.3 - Cooperative protocol [Seite 14]
8.3.1 - T1-Weighted Sequences [Seite 15]
8.3.1.1 - In-phase two-dimensional spoiled gradient echo sequence [Seite 15]
8.3.1.2 - Out-of-phase two-dimensional spoiled gradient echo sequence [Seite 15]
8.3.1.3 - Coronal two-dimensional spoiled gradient echo sequence [Seite 16]
8.3.1.4 - Fat-suppressed T1-weighted three-dimensional gradient recalled echo sequence [Seite 16]
8.3.2 - T2-weighted Sequences [Seite 17]
8.3.2.1 - Single-shot echo-train spin-echo sequence [Seite 17]
8.3.3 - Contrast-enhanced Fat-suppressed T1-weighted 3D GRE Sequence [Seite 19]
8.3.3.1 - Hepatic arterial dominant phase [Seite 19]
8.3.3.2 - Early hepatic venous phase [Seite 19]
8.3.3.3 - Interstitial phase [Seite 19]
8.4 - Motion-resistant protocols [Seite 20]
8.4.1 - T1-weighted Sequences [Seite 22]
8.4.1.1 - Two-dimensional MP-RAGE sequence [Seite 22]
8.4.1.2 - Two-dimensional WE-MP-RAGE [Seite 22]
8.4.1.3 - 3D radial GRE sequence [Seite 24]
8.4.2 - T2-weighted Sequences [Seite 26]
8.4.2.1 - SS-ETSE sequence [Seite 26]
8.5 - High-resolution images [Seite 26]
8.5.1 - Parallel MR Imaging [Seite 26]
8.5.2 - 3.0-T MR Imaging [Seite 26]
8.6 - Summary [Seite 26]
8.7 - References [Seite 26]
9 - Gadolinium Contrast Agent Selection and Optimal Use for Body MR Imaging [Seite 28]
9.1 - Key points [Seite 28]
9.2 - Introduction [Seite 28]
9.3 - Gadolinium general information [Seite 28]
9.3.1 - Gadolinium Mechanism of Action [Seite 28]
9.4 - Gadolinium-based contrast agents [Seite 29]
9.4.1 - Extracellular Space Agents (ECSAs) [Seite 29]
9.4.1.1 - Available agents [Seite 29]
9.4.1.2 - Mechanism of action [Seite 30]
9.4.1.3 - ECSA indications [Seite 30]
9.4.1.4 - ECSA indications for which gadobenate dimeglumine (ie, a high-relaxivity agent) is preferred [Seite 30]
9.4.2 - Hepatocyte-Specific Contrast Agents (HSCAs) [Seite 30]
9.4.2.1 - Available agents [Seite 30]
9.4.2.2 - Mechanism of action [Seite 31]
9.4.2.3 - Approved HSCA indications [Seite 31]
9.4.2.4 - Off-label HSCA indications [Seite 31]
9.4.2.5 - Gadoxetate disodium caveats and limitations [Seite 31]
9.4.3 - Blood Pool Agents (BPAs) [Seite 36]
9.4.3.1 - Available agents [Seite 36]
9.4.3.2 - Mechanism of action [Seite 36]
9.4.3.3 - BPA indications approved by the US Food and Drug Administration [Seite 37]
9.4.3.4 - Off-label BPA indications [Seite 38]
9.5 - Timing of postgadolinium contrast 3D gradient-echo sequences [Seite 38]
9.5.1 - Baseline Precontrast Images [Seite 38]
9.5.2 - Optimal Timing for 3D GRE Sequences Performed with ECSAs [Seite 38]
9.5.2.1 - Arterial phase [Seite 38]
9.5.2.2 - Blood pool phase [Seite 38]
9.5.2.3 - Extracellular phase [Seite 38]
9.5.3 - Optimal Timing for 3D GRE Sequences Performed with Gadoxetate Disodium [Seite 38]
9.5.3.1 - Arterial and blood pool phase [Seite 38]
9.5.3.2 - Late dynamic phase [Seite 38]
9.5.3.3 - Hepatobiliary phase [Seite 38]
9.5.4 - 3D GRE Sequences Specific for BPAs [Seite 38]
9.5.4.1 - Equilibrium (steady state) phase [Seite 38]
9.6 - Gadolinium chelate structure and stability [Seite 39]
9.7 - Gadolinium dosage [Seite 40]
9.8 - Gadolinium dose, concentration, and injection volume [Seite 40]
9.9 - Pulse sequences relative to the timing of intravenous gadolinium administration [Seite 40]
9.9.1 - Pulse Sequences that May Have Improved Diagnostic Quality After Intravenous Gadolinium [Seite 41]
9.9.2 - Pulse Sequences that Can Be Performed Either Before or After Administering Gadolinium [Seite 42]
9.9.3 - Pulse Sequences that Should Not Be Performed After Administering Gadolinium [Seite 42]
9.10 - High-relaxivity contrast agents [Seite 43]
9.11 - When to use gadoxetate disodium after hepatocellular carcinoma (or other neoplasm) is treated with chemoembolization or rad ... [Seite 43]
9.12 - What is the optimal flip angle for each GBCA? [Seite 44]
9.12.1 - Soft Tissue Evaluation Flip Angle [Seite 44]
9.12.2 - MR Angiography Flip Angle [Seite 44]
9.12.3 - Gadoxetate Disodium (Hepatobiliary Phase) Flip Angle [Seite 44]
9.12.4 - Gadofosveset Trisodium (Steady State/Equilibrium Phase) Flip Angle [Seite 45]
9.13 - Allergic reactions to GBCAs [Seite 45]
9.13.1 - General [Seite 45]
9.13.2 - Precautionary Measures that Can Be Taken in a Patient with Risk Factors for Allergic-Type Reactions [Seite 45]
9.14 - Strategies for adjusting body MR imaging protocols for patients with reduced estimated glomerular filtration rates [Seite 45]
9.14.1 - Liver MR Imaging [Seite 45]
9.14.2 - Renal MR Angiography [Seite 45]
9.15 - Summary [Seite 46]
9.16 - References [Seite 46]
10 - MR Imaging of Benign Focal Liver Lesions [Seite 48]
10.1 - Key points [Seite 48]
10.2 - Introduction [Seite 48]
10.3 - MR imaging technique [Seite 48]
10.3.1 - Protocol [Seite 48]
10.3.2 - Contrast Agents [Seite 49]
10.3.3 - Diffusion-Weighted Imaging [Seite 49]
10.4 - Focal liver lesions [Seite 50]
10.4.1 - Hemangioma [Seite 50]
10.4.2 - Focal Nodular Hyperplasia [Seite 52]
10.4.3 - Hepatocellular Adenoma [Seite 57]
10.5 - Pyogenic liver abscess [Seite 59]
10.6 - Hepatic cysts [Seite 63]
10.7 - Ciliated hepatic foregut cyst [Seite 64]
10.8 - Bile duct hamartomas [Seite 65]
10.9 - Biliary cystadenoma [Seite 67]
10.10 - Summary [Seite 69]
10.11 - References [Seite 69]
11 - Hepatocellular Carcinoma and Other Hepatic Malignancies [Seite 74]
11.1 - Key points [Seite 74]
11.2 - Introduction [Seite 74]
11.3 - Normal anatomy and imaging technique [Seite 75]
11.4 - Imaging findings and pathology [Seite 76]
11.4.1 - Primary Lesions [Seite 76]
11.4.1.1 - Hepatocellular carcinoma [Seite 76]
11.4.1.2 - Fibrolamellar carcinoma [Seite 81]
11.4.1.3 - Intrahepatic cholangiocarcinoma [Seite 82]
11.4.1.4 - Biliary cystadenocarcinoma [Seite 83]
11.4.1.5 - Hepatoblastoma [Seite 87]
11.4.1.6 - Epithelioid hemangioendothelioma [Seite 88]
11.4.1.7 - Sarcomas [Seite 88]
11.4.1.8 - Lymphoma [Seite 90]
11.4.1.9 - Metastases [Seite 91]
11.5 - Summary [Seite 94]
11.6 - References [Seite 95]
12 - MR Imaging of Diffuse Liver Disease [Seite 100]
12.1 - Key points [Seite 100]
12.2 - Introduction [Seite 100]
12.3 - Techniques [Seite 100]
12.3.1 - Iron Quantification [Seite 100]
12.3.1.1 - Signal intensity ratio [Seite 101]
12.3.1.2 - Relaxometry [Seite 101]
12.3.2 - Fat Quantification [Seite 102]
12.3.3 - Fat and Iron Quantification [Seite 102]
12.3.4 - Elastography [Seite 103]
12.4 - Fibrosis and cirrhosis [Seite 104]
12.5 - Metabolic/storage diseases [Seite 106]
12.5.1 - Hepatosteatosis [Seite 106]
12.5.2 - Iron Overload [Seite 107]
12.5.3 - Wilson Disease [Seite 107]
12.5.4 - Glycogen and Lipid Storage Diseases [Seite 109]
12.6 - Infectious and inflammatory/granulomatous [Seite 109]
12.6.1 - Amyloidosis [Seite 109]
12.6.2 - Sarcoidosis [Seite 111]
12.7 - Vascular [Seite 111]
12.7.1 - Budd-Chiari Syndrome [Seite 111]
12.7.2 - Passive Hepatic Congestion [Seite 113]
12.7.3 - Sinusoidal Obstruction Syndrome [Seite 113]
12.8 - Discussion [Seite 113]
12.9 - References [Seite 114]
13 - MR Imaging of the Biliary System [Seite 116]
13.1 - Key points [Seite 116]
13.2 - Introduction [Seite 116]
13.3 - MR technique [Seite 116]
13.4 - Hepatobiliary-specific contrast agents [Seite 117]
13.5 - Pitfalls and artifacts [Seite 117]
13.6 - Normal and variant biliary anatomy [Seite 118]
13.7 - Congenital biliary lesions [Seite 120]
13.8 - Bile [Seite 123]
13.9 - Cholelithiasis [Seite 123]
13.10 - Cholecystitis [Seite 127]
13.11 - Adenomyomatosis [Seite 128]
13.12 - Gallbladder carcinoma [Seite 129]
13.13 - Infectious cholangitis [Seite 131]
13.14 - Stricture [Seite 133]
13.15 - Primary sclerosing cholangitis [Seite 134]
13.16 - Primary biliary cirrhosis [Seite 137]
13.17 - Cholangiocarcinoma [Seite 137]
13.18 - Biliary cystadenoma and cystadenocarcinoma [Seite 139]
13.19 - Postsurgical evaluation [Seite 140]
13.20 - Summary [Seite 142]
13.21 - References [Seite 142]
14 - MR Imaging of the Pancreas [Seite 148]
14.1 - Key points [Seite 148]
14.2 - Introduction [Seite 148]
14.3 - Technique [Seite 148]
14.3.1 - Normal MR Appearance of the Pancreas [Seite 148]
14.4 - Pancreatitis [Seite 150]
14.4.1 - Acute Pancreatitis [Seite 150]
14.4.2 - Chronic Pancreatitis [Seite 152]
14.4.3 - Groove Pancreatitis [Seite 154]
14.4.4 - Autoimmune Pancreatitis [Seite 155]
14.5 - Anatomic variants [Seite 156]
14.5.1 - Pancreas Divisum [Seite 156]
14.5.2 - Annular Pancreas [Seite 156]
14.6 - Pancreatic neoplasms [Seite 157]
14.6.1 - Adenocarcinoma [Seite 157]
14.6.2 - Pancreatic Endocrine Tumors [Seite 159]
14.6.3 - Mucinous Cystic Neoplasms [Seite 160]
14.6.4 - Serous Cystadenomas [Seite 160]
14.6.5 - Intraductal Papillary Mucinous Neoplasms [Seite 161]
14.6.6 - Solid Pseudopapillary Tumor [Seite 163]
14.6.7 - Pancreatic Lymphoma [Seite 164]
14.6.8 - Pancreatic Metastases [Seite 165]
14.7 - Summary [Seite 166]
14.8 - References [Seite 166]
15 - MR Imaging of the Kidneys and Adrenal Glands [Seite 170]
15.1 - Key points [Seite 170]
15.2 - Introduction [Seite 170]
15.3 - MR imaging technique [Seite 170]
15.4 - Kidneys [Seite 171]
15.4.1 - Cystic Renal Lesions [Seite 172]
15.4.2 - Solid Renal Lesions [Seite 173]
15.4.2.1 - RCC [Seite 173]
15.4.2.2 - Angiomyolipoma [Seite 175]
15.4.2.3 - Oncocytoma [Seite 177]
15.4.3 - Infiltrative Renal Masses [Seite 177]
15.4.3.1 - Lymphoma [Seite 177]
15.4.3.2 - Metastases [Seite 178]
15.4.4 - Renal Mass Mimickers [Seite 178]
15.4.4.1 - Pyelonephritis [Seite 178]
15.4.4.2 - Vascular causes [Seite 178]
15.5 - Excretory system [Seite 179]
15.5.1 - Urothelial Neoplasms [Seite 179]
15.6 - Adrenal glands [Seite 180]
15.6.1 - Adrenal Adenoma [Seite 180]
15.6.2 - Myelolipoma [Seite 182]
15.6.3 - ACC [Seite 183]
15.6.4 - Pheochromocytoma [Seite 184]
15.6.5 - Metastases [Seite 185]
15.6.6 - Adrenal Cysts, Pseudocysts [Seite 185]
15.6.7 - Adrenal Hematoma [Seite 187]
15.7 - Summary [Seite 187]
15.8 - References [Seite 187]
16 - MR Enterography for Assessment and Management of Small Bowel Crohn Disease [Seite 190]
16.1 - Key points [Seite 190]
16.2 - Introduction [Seite 190]
16.3 - Imaging protocols [Seite 191]
16.4 - Normal anatomy and MR imaging appearance of small bowel [Seite 192]
16.5 - Imaging findings/pathology [Seite 193]
16.5.1 - Active Inflammation [Seite 194]
16.5.2 - Penetrating Disease [Seite 194]
16.5.3 - Fibrostenosing Disease [Seite 195]
16.5.4 - Crohn Colitis [Seite 196]
16.5.5 - Other Findings [Seite 196]
16.6 - Utility of MRE [Seite 196]
16.6.1 - MRE Versus CTE [Seite 197]
16.7 - Pitfalls [Seite 198]
16.8 - Summary [Seite 199]
16.9 - References [Seite 199]
17 - MR Imaging of the Prostate [Seite 202]
17.1 - Key points [Seite 202]
17.2 - Introduction [Seite 202]
17.3 - Treatment [Seite 203]
17.4 - Anatomy [Seite 203]
17.5 - Imaging protocol [Seite 204]
17.5.1 - Preparation [Seite 204]
17.5.2 - Choice of the Scanner and Coils [Seite 204]
17.5.3 - Multiparametric Sequences [Seite 204]
17.5.4 - T2-weighted Imaging Technique [Seite 204]
17.5.5 - DWI Technique [Seite 206]
17.5.6 - DCE-MR Imaging Technique [Seite 206]
17.5.7 - MR Spectroscopic Imaging [Seite 208]
17.5.8 - T1-weighted Imaging Technique [Seite 210]
17.6 - Interpretation of prostate MR imaging [Seite 210]
17.6.1 - Peripheral Zone Cancer [Seite 211]
17.6.2 - Evaluation for Extracapsular Extension and Neurovascular Bundle Invasion [Seite 213]
17.6.3 - Evaluation of Seminal Vesicle Invasion [Seite 213]
17.6.4 - CG Cancer [Seite 215]
17.6.5 - Quantitative Approach and Computer-aided Diagnosis [Seite 216]
17.7 - Clinical indications [Seite 217]
17.7.1 - Staging [Seite 217]
17.7.2 - Detection [Seite 217]
17.7.3 - Localization [Seite 218]
17.7.4 - Assessing Aggressiveness [Seite 219]
17.7.5 - Role of MR imaging in Active Surveillance [Seite 219]
17.7.6 - Image-guided Interventions [Seite 220]
17.7.7 - Posttreatment Evaluation [Seite 221]
17.8 - Summary [Seite 222]
17.9 - References [Seite 222]
18 - MR Angiography of the Abdomen and Pelvis [Seite 230]
18.1 - Key points [Seite 230]
18.2 - Introduction [Seite 230]
18.3 - MR angiographic techniques [Seite 231]
18.3.1 - Contrast-Enhanced MR Angiography [Seite 231]
18.3.2 - Noncontrast Techniques for Abdomen and Pelvis [Seite 232]
18.3.3 - Field-Strength Considerations [Seite 234]
18.3.4 - Contrast Agents [Seite 234]
18.4 - Clinical applications: arterial imaging [Seite 235]
18.4.1 - Renal Artery Stenosis [Seite 235]
18.4.2 - Mesenteric Artery Stenosis and Flow-Related Aneurysms [Seite 236]
18.4.2.1 - Median arcuate ligament syndrome [Seite 236]
18.4.2.2 - Flow-related aneurysms [Seite 237]
18.4.3 - Leriche Syndrome [Seite 239]
18.4.4 - Iliac Artery Aneurysms [Seite 239]
18.4.5 - Vasculitis [Seite 240]
18.5 - Clinical applications: venous imaging [Seite 240]
18.5.1 - Congenital Variants of the Inferior Vena Cava and Renal Veins [Seite 240]
18.5.2 - May-Thurner Syndrome [Seite 241]
18.6 - Clinical applications: vascular complications of transplantation [Seite 242]
18.6.1 - Pancreas Transplant Complications [Seite 242]
18.6.2 - Kidney Transplant Complications [Seite 244]
18.6.3 - Liver Transplant Complications [Seite 247]
18.7 - Summary [Seite 249]
18.8 - References [Seite 249]
19 - Dealing with Vascular Conundrums with MR Imaging [Seite 252]
19.1 - Key points [Seite 252]
19.2 - Introduction [Seite 252]
19.3 - Imaging techniques [Seite 253]
19.3.1 - Non-Contrast-Enhanced MR Angiography [Seite 253]
19.3.2 - Contrast-Enhanced MR Angiography and Postprocessing Techniques [Seite 253]
19.3.3 - Contrast-Enhanced Fat-Suppressed T1-Weighted Three-Dimensional-GE Sequences [Seite 255]
19.3.4 - Motion-Resistant Protocol in Noncooperative Patients [Seite 255]
19.4 - Abdominal vascular imaging [Seite 256]
19.4.1 - Problem Solving [Seite 256]
19.4.1.1 - Flow artifact versus thrombosis [Seite 256]
19.4.1.2 - Bland thrombosis versus tumor thrombosis [Seite 256]
19.4.1.3 - Vessel versus mass [Seite 258]
19.4.1.4 - Type of vessel [Seite 258]
19.4.2 - Clinical Considerations [Seite 258]
19.4.2.1 - Abdominal aortic aneurysm [Seite 258]
19.4.2.2 - Aortic dissection [Seite 261]
19.4.2.3 - Visceral artery aneurysm [Seite 261]
19.4.2.4 - Mesenteric arterial ischemia [Seite 261]
19.4.2.5 - Portal venous thrombosis [Seite 263]
19.4.2.6 - Budd-Chiari syndrome [Seite 264]
19.4.2.7 - Hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu syndrome) [Seite 265]
19.4.2.8 - IVC disease [Seite 266]
19.5 - Pelvic vascular imaging [Seite 268]
19.5.1 - Clinical Considerations [Seite 268]
19.5.1.1 - Pelvic veins [Seite 268]
19.6 - Thoracic vascular imaging [Seite 269]
19.6.1 - Clinical Considerations [Seite 271]
19.6.1.1 - Thoracic aorta [Seite 271]
19.6.1.2 - Pulmonary arteries and pulmonary thromboembolic disease [Seite 271]
19.7 - Summary [Seite 272]
19.8 - References [Seite 272]
20 - Functional MR Imaging of the Abdomen [Seite 274]
20.1 - Key points [Seite 274]
20.2 - Introduction [Seite 274]
20.3 - DWI [Seite 274]
20.3.1 - Basic Concepts [Seite 275]
20.3.2 - Optimizing Technique [Seite 275]
20.3.3 - Apparent Diffusion Coefficient [Seite 276]
20.3.4 - Qualitative and Quantitative Analysis of DWI [Seite 277]
20.3.5 - IVIM [Seite 277]
20.3.6 - Diffusion Tensor Imaging [Seite 277]
20.3.7 - Applications of DWI [Seite 277]
20.3.7.1 - Diffuse liver disease [Seite 278]
20.3.7.2 - Focal liver masses [Seite 278]
20.3.7.3 - Liver tumor response assessment [Seite 279]
20.3.7.4 - Pancreatic disease [Seite 280]
20.3.7.5 - Bowel disease [Seite 281]
20.3.7.6 - Renal disease [Seite 281]
20.3.7.7 - Prostate cancer [Seite 282]
20.3.8 - Summary of DWI [Seite 283]
20.4 - MR perfusion [Seite 283]
20.4.1 - DCE MR Imaging Technique [Seite 284]
20.4.2 - Challenges in DCE MR Imaging [Seite 284]
20.4.3 - Uses of DCE MR Imaging [Seite 284]
20.5 - MR elastography [Seite 284]
20.5.1 - Applications of MR Elastography [Seite 285]
20.6 - Summary [Seite 287]
20.7 - References [Seite 287]
21 - Index [Seite 296]
Gadolinium Contrast Agent Selection and Optimal Use for Body MR Imaging
Flavius F. Guglielmo, MDa∗flavius.guglielmo@jefferson.edu, Donald G. Mitchell, MDa and Shiva Gupta, MDb, aDepartment of Radiology, Thomas Jefferson University Hospital, 132 South 10th Street, Philadelphia, PA 19107, USA; bDepartment of Radiology, The University of Texas MD Anderson Cancer Center, 1400 Pressler Street, Unit 1473, FCT15.5013, Houston, TX 77030, USA
∗Corresponding author.
Proper selection of a gadolinium-based contrast agent (GBCA) for body magnetic resonance imaging (MRI) cases requires understanding the indication for the MRI exam, the key features of the different GBCAs, and the effect that the GBCA has on the selected imaging protocol. The different categories of GBCAs require timing optimization on postcontrast sequences and adjusting imaging parameters to obtain the highest T1 contrast. Gadoxetate disodium has many advantages when evaluating liver lesions, although there are caveats and limitations that need to be understood. Gadobenate dimeglumine, a high-relaxivity GBCA, can be used for indications when stronger T1 relaxivity is needed.
Keywords
Gadolinium-based contrast agents
Extracellular space agents
Hepatocyte-specific contrast agents
Blood pool agents
Postgadolinium pulse sequences
Gadolinium chelate structure and stability
Key points
• Proper selection of a gadolinium-based contrast agent requires understanding the indication for the magnetic resonance (MR) imaging examination, the key features of the different types of commercially available contrast agents, and the effect that the contrast agent has on the selected imaging protocol.
• The timing is different for each category of gadolinium contrast, and therefore, protocols must be created that optimize the timing based on the type of gadolinium contrast agent administered.
• Gadoxetate disodium has many advantages when evaluating liver lesions. However, there are important caveats and limitations that need to be understood before selecting this agent.
• A high-relaxivity contrast agent such as gadobenate dimeglumine can be used when stronger T1 relaxivity is needed, such as for MR angiography, MR enterography, MR venography, pelvis fistula MR imaging, and combined abdomen and pelvis MR imaging. Gadobenate dimeglumine, at reduced dose, is also ideal for MR urography, because of the high relaxivity in plasma versus urine.
Introduction
Choosing the optimal gadolinium contrast agent for body magnetic resonance (MR) imaging cases requires the following:
1. Knowing the patient's clinical information to determine the appropriate examination indication and whether intravenous gadolinium administration is needed
2. Knowing the relevant properties of the chosen gadolinium contrast agent
3. Understanding the effect that intravenous gadolinium has on body MR imaging pulse sequences
This article describes how to combine these factors when choosing an intravenous gadolinium contrast agent to perform efficient and high-quality body MR imaging examinations.
Gadolinium general information
Gadolinium Mechanism of Action
Gadolinium is highly paramagnetic because of its 7 unpaired electrons.1 Although the iodine molecule directly increases computed tomography (CT) attenuation, the effect of the gadolinium molecule is indirect. This leads to an amplification effect, because one gadolinium atom can facilitate relaxation of many adjacent water molecules. Gadolinium acts by shortening T1, T2, and T2* relaxation times of adjacent water protons.1–4 This relaxation primarily causes increased signal intensity (enhancement) on T1-weighted images (Fig. 1). However, T2 shortening can predominate and cause decreased signal intensity on T2-weighted images (Fig. 2) and, in high gadolinium concentrations, can cause decreased signal intensity on T1-weighted images, as a result of dominant T2 shortening if the echo time (TE) is high enough (Fig. 3). Examples in which particularly high gadolinium concentration can be found include urine or first-pass venous injection into the superior vena cava. In short tau inversion recovery (STIR) sequences, the T1 shortening from gadolinium results in a loss of signal intensity (Fig. 4).1,4
Fig. 1 Axial pregadolinium (A), arterial phase (B), portal venous phase (C), and delayed phase (D) fat-suppressed 3D gradient-echo (GRE) images showing an enhancing right-lobe liver lesion with discontinuous nodular peripheral and progressive centripetal enhancement consistent with a hemangioma (arrows) (A–C: repetition time [TR] = 4, echo time [TE] = 1.8, flip angle [FA] 12) (D: TR = 3.5, TE = 1.7, FA 15).
Fig. 2 Axial pregadolinium (A) and postgadolinium (B) heavily T2-weighted images. Shortened T2 relaxivity primarily causes decreased signal intensity in the renal collecting systems (arrows). There is little or no change in other tissues (repetition time 760, echo time 178).
Fig. 3 Coronal (A) pregadolinium and (B) postgadolinium T1-weighted images on 0.7-T MR imaging (repetition time 248, echo time 8, flip angle 70). The high gadolinium concentration in the proximal ureters leads to decreased signal intensity on T1-weighted images (arrows).
Fig. 4 Axial pregadolinium (A, B) and postgadolinium (C, D) STIR images obtained after the intravenous administration of gadoxetate disodium. In STIR sequences, the T1 shortening property of gadolinium results in a loss of signal intensity. Note the darkening of the liver (arrow in C, D) and renal collecting systems (arrowheads in D) on postcontrast images (repetition time 880, echo time 67, inversion time 80).
Gadolinium-based contrast agents
There are currently 9 different commercially available gadolinium-based contrast agents (GBCAs) that can be used for body MR imaging cases. The decision about which agent to use can be simplified by first considering which category of GBCA is needed for the examination indication. The 3 categories include extracellular space agents, hepatocyte-specific contrast agents, and blood pool agents.1,2,5 After selecting the proper category for the indicated body MR imaging examination, it is important to understand some of the characteristics of each of the agents. Although each agent has many differentiating characteristics the key features for selecting the optimal GBCA are highlighted in Table 1.4,6–12
Table 1
Characteristics of gadolinium-based contrast agents needed for protocoling body MR imaging cases
ECSA Gadoterate meglumine Dotarem Cyclic Ionic 3.4–3.8 0 0.5 0.1 Gadobutrol Gadavist/Gadovist Cyclic Nonionic 4.9–5.5 0 1 0.1 Gadopentetate dimeglumine Magnevist Linear Ionic 3.9–4.3 0 0.5 0.1 Gadodiamide Omniscan Linear Nonionic 4–4.6 0 0.5 0.1 Gadoversetamide Optimark Linear Nonionic 4.4–5 0 0.5 0.1 Gadoteridol ProHance Cyclic Nonionic 3.9–4.3 0 0.5 0.1 HSCA Gadoxetate disodium Eovist/Primovist Linear Ionic 6.5–7.3 50 0.25 0.025 Gadobenate dimeglumine MultiHance Linear Ionic 6–6.6 4–5 0.5 0.1 BPA Gadofosveset trisodium Ablavar/Vasovist Linear Ionic 18–20 5 0.25 0.03Abbreviation: BPA, blood pool agents; ECSA, extracellular space agents; HSCA, hepatocyte-specific contrast agents; mmol/kg, millimoles per kilogram; mmol/mL, millimoles per milliliter; T, tesla.
