Breath-hold MR Cholangiopancreatography with Three-dimensional, Segmented, Echo-planar Imaging and Volume Rendering

Abstract

End-expiration, 21-second breathhold, three-dimensional magnetic resonance (MR) cholangiopancreatography (MRCP) was developed with segmented echo-planar imaging. In 15 healthy subjects and 14 randomly selected patients undergoing liver studies, three-dimensional MRCP images were obtained and volume rendered. In 15 (100%) healthy subjects and 13 (93%) patients, clear depiction of biliary, hepatic, and pancreatic ducts (with lumen diameter of at least 2 mm) was possible with good signal-to-noise ratio.Fast magnetic resonance (MR) imaging techniques exploit the long T2 exhibited by biliary and hepatic fluids (Ͼ1.5 seconds) to produce high-quality, two-and three-dimensional (3D) MR cholangiopancreatographic (MRCP) images without the addition of contrast media. In initial attempts to visualize the entire biliary tree, steady-state free-precession imaging was used, with high contrast over several breath holds (1,2). However, steady-state free-precession sequences proved too sensitive to signal loss from magnetic susceptibility, fluid motion, and pulsation. More robustness is now possible with rapid acquisition with relaxation enhancement (RARE) (3) and fast spin-echo (SE) (4) sequences. With long effective echo times, only fluid-filled compartments are observed with nearly complete background suppression and minimal sensitivity to motion and signal loss due to magnetic susceptibility. Many techniques have been evaluated that differ in coverage, spatial resolution, signal-tonoise ratio (SNR), examination length, and patient cooperation. These techniques include breath-hold, two-dimensional, single-shot, single-projection, thick-section RARE (5); breath-hold, twodimensional, multisection, half-Fourier RARE (HASTE; Siemens Medical Systems, Erlangen, Germany) (6); and fast SE (7,8) and respiratory-gated 3D fast SE (9,10). The RARE and half-Fourier RARE techniques have been widely explored and accepted as techniques of choice for diagnostic MRCP.Nonetheless, the availability of a 3D fast SE technique would enable operatorindependent imaging, large-volume coverage, examinations with maximum patient comfort, and the possibility of data reformation and volume rendering. Unfortunately, imaging time can still be excessive and results hampered by blurring from remnant respiratory motion. By combining 3D fast SE and segmented echo-planar imaging (11), we attempted to increase SNR and resolution in shorter imaging time, equivalent to an increase in data density, to obtain breath-hold volume images of the entire hepatic, bile, and pancreatic duct systems with the advantages of 3D acquisitions. Therefore, we performed this study to illustrate the potential of this new acquisition technique. Materials and Methods Patient PopulationThe study population included 15 healthy volunteers (six men, nine women; age range, 21-34 years). In addition, 14

Magnetic resonance cholangiography: comparison of two- and three-dimensional sequences for assessment of malignant biliary obstruction

“…It is well-known that the 3D-RARE technique has an advantage over 2D imaging, enabling operator independent imaging, larger-volume coverage, thinner sections without interslice gaps, and a higher SNR [16][17][18][19]. Also, the possibility of data reformation and volume rendering allows the clarification of anatomic relationships.…”

Evaluation of the biliary and pancreatic system with 2D SSFSE, breathhold 3D FRFSE and respiratory-triggered 3D FRFSE sequences

“…The combination of 3D FSE sequences with echoplanar imaging techniques, according to Wielopolski et al [18], made it possible to reduce acquisition times and cover a sufficiently large anatomical volume to study the entire biliary system. In addition to reducing acquisition times, the introduction of echoplanar imaging in 3D sequences increased the SNR and spatial resolution [18].…”

Breath-holding 3D MRCP: the time is now?

“…For these reasons, many authors have advocated the use of three-dimensional (3D) MRCP sequences [2]. The theoretical main advantages of 3D MRCP compared to 2D MRCP sequences include: (1) acquisition of contiguous sections that may be used to reconstruct images in any projection, yielding the anatomical overview normally provided with thick-slab 2D images, (2) better spatial resolution with thinner imaging section and better signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) and (3) acquisition of all slices with a single coronal volume placed over the biliary tree and pancreatic ducts without need to obtain rotating oblique 2D SSFSE thick-slab planes [2,3].Interestingly, most initial publications focusing on 3D MRCP technique used breath-holding acquisition sequences [2,4]. However, these initial sequences suffered from decreased spatial resolution and acquired non-isotropic voxel datasets [2].…”

“…Interestingly, most initial publications focusing on 3D MRCP technique used breath-holding acquisition sequences [2,4]. However, these initial sequences suffered from decreased spatial resolution and acquired non-isotropic voxel datasets [2].…”