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Abstract
Due to the development of dedicated receiver coils for 3 tesla (T) magnetic resonance (MR) imaging and increased gradient performance, 3T MR imaging of the abdomen is rapidly becoming a part of routine clinical practice. The most important advantage of 3T MR imaging is a higher signal-to-noise ratio and contrast-to-noise ratio compared with 1.5T systems, which can be used to improve spatial resolution and shorten image acquisition time. In the abdomen, the improved image quality of non-enhanced and enhanced solid organ imaging, MR angiography, MR cholangiopancreatography, and MR spectroscopy can be obtained at 3T due to the increased signal-to-noise ratio and contrast-to-noise ratio. However, 3T abdominal MR imaging also presents several technical challenges, such as increased energy deposition within the patient's body, standing wave artifacts, and increased susceptibility artifacts. Therefore, abdominal MR imaging at 3T requires adjustments in the sequence parameters of pulse sequences designed for 1.5T to optimize image quality. At present, 3T abdominal MR imaging is feasible with high image quality in an acceptable scan time, but 3T imaging is not significantly superior to 1.5T imaging in terms of cost-effectiveness. Future improvements in coil technology and new sequences suitable for 3T may enable wider clinical use of 3T for abdominal MR imaging.
Figures and Tables
Figure 1
Comparison of T2-weighted fast spin echo images obtained with 1.5 tesla (T) (A) and 3T (B) systems in the same patient. The image obtained at 3T shows an increased signal-to-noise ratio with increased conspicuity of a small hepatic cyst (arrow). Parameters at 1.5T were 5,500/88 (repetition time msec/echo time msec), 6-mm section thickness, 320×224 matrix, and 36-cm field of view. Parameters at 3T were 2,500/99, 6-mm section thickness, 512×255 matrix, and 36-cm field of view.
Figure 2
High-resolution isotropic 3D T2-weighted images of the female pelvis at 3 tesla (T). (A) 3D turbo spin echo T2-weighted image in a 58-year-old woman with cervical cancer shows slightly hyperintense endocervical mass (arrow). Sequence parameters were sampling perfection with application of optimized contrasts using different flip angle evolution (SPACE), 2,000/127, 1-mm section thickness, echo train of 89, 256×256 matrix, and 18-cm field of view. (B) Sagittal reconstructed image from 3D data set again shows hyperintense endocervical mass (arrow) and two nabothian cysts (arrowheads). B, bladder; R, rectum.
Figure 3
Increased conspicuity of hepatic metastasis at 3 tesla (T) magnetic resonance imaging using liver-specific contrast agent in a pa-tient with rectal cancer. (A) Contrast-enhanced computed tomography shows a subtle low density lesion (arrow) at the periphery of the right hepatic lobe. (B) Axial dynamic contrast-enhanced 3D gradient echo T1-weighted image with fat saturation after injection of gadoxetic acid shows a small low signal intensity lesion with peripheral rim enhancement on hepatic arterial phase. (C) On hepatobiliary phase obtained 20 minutes after contrast injection, the mass shows distinct low signal intensity (arrow) compared with background liver enhancement. Another unexpected small metastatic lesion (arrowhead) is also easily detected the segment 7 of the liver.
Figure 4
Maximum-intensity projection image from 3 tesla abdominal magnetic resonance angiographic data obtained from a 52-year-old woman with kidney transplantation demonstrates excellent contrast-to-noise ratio and detailed vascular anatomy.
Figure 5
Coronal maximum-intensity projection image from 3D magnetic resonance cholangiopancreatography at 3 tesla shows increased fluid conspicuity due to a high signal-to-noise ratio in a 42-year-old man with pancreas head adenocarcinoma. Abrupt cut-off of the distal common bile duct and pancreatic duct at the head portion (arrow) is well demonstrated.
Figure 6
Increased susceptibility artifacts at 3 tesla in a 64-year-old man with proximal rectal cancer. Pelvic magnetic resonance images were obtained after endoscopic biopsy and metallic clipping. Sagittal T2-weighted image (A) and diffusion-weighted image (B) (b=500 sec/mm2) show prominent susceptibility artifacts around the metallic clip (arrows). It is difficult to know the exact extent of the rectal cancer due to the severe artifacts.
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