Magnetic resonnance cholangiography (MRC): comparaison of two and three-dimensional sequences for assessment of biliary anomalies A.Daghfous*, F. AbidI*, K. Bouzaid**, M. Maarouf*, L. Rezgui Marhoul* Radiology services in Trauma Center*, Tunisia and Taher Maamouri’s hospital**, Nabeul GI29

 Three-dimensional (3D) imaging has become a popular modality because of its ability to provide 3D views of the patient's anatomy. It also does not have many of the inherent shortcomings of two-dimensional (2D) imaging.  Two-dimensional images make interpretation more difficult by forcing the reader to restructure the 2D images mentally in order to appreciate the true form of the disease or organ. Three-dimensional images, on the other hand, provide easier-to-understand information, while being more efficient, accurate, objective, and reproducible

The purpose was to retrospectively compare two-dimensional (2D) magnetic resonnance cholangiography (MRC) including breath-hold single-shot rapid acquisition with relaxation enhancement (RARE) and multislice half-fourrier RARE versus 3D-RARE MRC in the evaluation of biliary anomalies.

 Retrospective study  20 adult patients who underwent MRC for pancreatic or bile duct abnormalities detected by ultra sound or CT-scan.  Our protocol includes conventionnal sequences and systematic sequences 2D and 3D-MRC thin sections.

 MRC findings including lithiasis (n=11), biliary malignancy (n=5), gallblader carcinoma (n=1), ampullary cancer (n=2), congenital abnormality of bilary duct (n=1).  All of these bile tract abnormalities were visible on the 2D sequences, however, with the 3D sequences, the picture quality was much higher with better spatial resolution

Cholangio-MRI: 2D (A and B) and 3D séquences (Cet D) Choledolithiasis ( ) and galdbladder calculi ( ) A CD B

Dilatation of intra hepatic bile duct secondary to hilar cholangiocarcinoma ( ) without dilatation of the wirsung ( ) and the main bile duct ( ) MRC 2D MRC 3D Ax T1 gado

AX T2 MRC 2D MRC 3D Cystic dilatation of pancreatic ducts( ) relevant to TIPMP

Hilar cholangiocarcinoma ( ) MR cholangiography demonstrates dilatation of intra hepatic bile ducts( ) Without visualization of the main bile duct T1G T2 MRC 2D MRC 3D MRC 2D

Ax T2 MRC 2D MRC 3D Caroli disease MRC demonstrates cystic dilatation of main bile duct and intra hepatic ducts relevant to Caroli disease

Ax T2 MRC 3D MRC 2D MRC demonstrates dilatation of main bile duct and intra hepatic ducts secondary to ampulloma vaterien ( )

*In our study, 2D-MRC and 3D-MRC showed Similar diagnostic accuracy in patients with biliary diseases. Although 3D-MRC had the tendency to show higher accuracy compared with 2D MRC: it did display superior image quality and ductal conspicuity compared with 2DMRC. * Magnetic resonnance (MR) cholangiography has emerged as an accurate, non invasive alternative to diagnostic endoscopic retrogradecholangiography (ERC) in the evaluation of disease of the biliary tract.

* Two-dimensional thick-section single-shot RARE and multislice thin-section half-Fourier RARE techniques are the most commonly used techniques for MRC. The 2D thick-section technique has the major advantage of allowing a quick acquisition of an image giving an overview of the ductal anatomy. * The limitation of the thick-section technique, however, is the lack of postprocessing, preventing the evaluation of individual tomographic sections. Therefore, thick-section technique alone is not suitable for the evaluation of complex anatomical structures like the hepatic hilum.

* Currently, most institutes perform MRC using a combination of thicksection imaging to provide an anatomical overview and thin-section imaging to provide finer detail. * The major advantage of 3D-MRC is that it provides isotropic MIP images without distortion allowing its usage as a complementary sequence tostandard 2D-MRC in the evaluation of the biliary tree. * Three-dimensional acquisition is appealing for MRC because it provides contiguous thin sections (approximately1 mm in all three dimensions) that may be used to reconstruct images in any plane.

* Volumetric acquisition of 3D-MRC has been used to improve the quality of MIP reconstruction using a variety of software to depict complex biliary ductal relationships * 3D-MRC has a higher technical and overall image quality than 2D-MRC,there is still a limitation in improving the diagnostic performance for evaluating all biliary diseases. Nevertheless, high quality MIP reconstructions are very useful because they improve the understanding of complex anatomical structures such as the hepatic hilum by selecting the optimal viewing angle. * Two major disadvantages of 3D-MRC are its long acquisition time and high level of background suppression which lead to low anatomical information regarding underlying parenchymal organs

 3D-MRC has superior image quality to 2D-MRC.  3D-MRC showed no difference in accuracy compared with 2D-MRC for evaluating the biliary diseases.  3D-MRC should be a complementary sequence to conventional 2D-MRC for the accurate evaluation of the biliary tree.