Indian Journal of Radiology Indian Journal of Radiology  

   Login   | Users online: 789

Home Bookmark this page Print this page Email this page Small font sizeDefault font size Increase font size     

 

GI RADIOLOGY Table of Contents   
Year : 2007  |  Volume : 17  |  Issue : 4  |  Page : 247-253
Review: Advances in magnetic resonance cholangiopancreatography: From morphology to functional imaging


Abdominal and Interventional Radiology, Massachusetts General Hospital, Boston, USA

Click here for correspondence address and email
 

How to cite this article:
Gulati K, Catalano OA, Sahani DV. Review: Advances in magnetic resonance cholangiopancreatography: From morphology to functional imaging. Indian J Radiol Imaging 2007;17:247-53

How to cite this URL:
Gulati K, Catalano OA, Sahani DV. Review: Advances in magnetic resonance cholangiopancreatography: From morphology to functional imaging. Indian J Radiol Imaging [serial online] 2007 [cited 2020 Jun 4];17:247-53. Available from: http://www.ijri.org/text.asp?2007/17/4/247/36869

   Introduction Top


Magnetic resonance cholangiopancreatography (MRCP) is a medical imaging technique, which uses magnetic resonance to visualize the biliary tree and pancreatic ducts in a non-invasive way. Though several variations of this technique have been developed in the recent years, they all share the use of a heavily T2W pulse sequence, which selectively displays static or slow-moving fluid-filled structures as high intensity areas. The recent development of many three dimensional (3D) sequences has substantially enhanced the quality of the MRCP images. Likewise, the introduction of hepatobiliary contrast media and secretin, has enabled functional assessment of biliary excretion and the exocrine pancreas, respectively.

In this article, we present new MRCP techniques using 3D acquisition and the role of functional MRCP. In addition, we discuss commonly imaged biliary and pancreatic duct pathologies, including congenital anomalies, obstruction, trauma and tumors.


   Techniques Top


Traditional Fluid-Based Techniques (2D MRCP)

The underlying principle of MRCP is imaging fluid in the biliary and pancreatic tree while suppressing background signals from non-fluid structures. Heavy T2W sequences are used to accomplish this purpose. Single-shot, fast spin-echo (SSFSE) sequences are considered ideal for this task. Two different and complementary approaches are generally used for 2D MRCP: a thick-slab, single-shot, turbo spin-echo (TSE) T2W sequence and a multisection, thin-slab, single-shot TSE T2W sequence. Limitations of SSFSE techniques include image blurring induced by long echo train lengths (ETL), flow artifacts within the biliary tree that can occasionally simulate stones or masses and problems with saturation of adjacent slices when sequential acquisitions are performed. [1] With this technique, it is often necessary to acquire images at different angles, through the appropriate structures and therefore the technique is dependent on the operator's familiarity with the anatomy and pathology.

3D MRCP

Advances in gradient strength and image processing software have significantly influenced the development of 3D MRCP sequences that can be acquired in suspended respiration or with respiratory gated techniques using fast recovery sequences (FSE) or steady state free precession (SSFP). The near isotropic volumetric data from a 3D MRCP sequence can then be processed using a maximum intensity projection (MIP) or volume rendered technique (VRT) for an esthetically pleasing display of the biliary tree and pancreatic duct [Figure - 1]. [Table - 1] shows the routinely used parameters for 2D and 3D MRCP. [Table - 2] examines the advantages and disadvantages of the 3D MRCP technique.

Functional / Contrast Enhanced MRCP

Although conventional, fluid-based T2W MRCP is excellent for demonstrating morphological details, there is still lack of functional information concerning bile production and excretion through the biliary tree. MR contrast agents with hepatobiliary excretion such as mangafodipir trisodium (Teslascan; GE Healthcare Technologies), gadobenate dimeglumine or Gd-BOPTA (Multihance; Bracco) and gadolinium-ethoxybenzyl-diethylene-triamine-pentaacetic acid or Gd-EOB-DTPA (Primovist, Schering-AG), are now being used for this purpose.

The optimum timing for biliary excretion of these contrast agents ranges from 10-60 minutes. The preferred acquisition sequence for T1W MRCP is a fat-saturated, spoiled gradient recall (SPGR) sequence. For image display, data can be processed with any of the preferred 3D rendering techniques [Figure - 2].

Indications and current clinical role of contrast-enhanced MRCP (CE-MRCP)

  1. Defining biliary anatomy for pre-surgical planning prior to major hepatectomies and living donor liver transplantation.
  2. Evaluating the integrity of the bile duct
  3. Differentiating true obstruction from pseudo-obstruction


Functional / Secretin Stimulated MRCP

With the availability of the new pharmaceutical agent, secretin (SecreFlo, Repligen Corporation, Waltham, MA, USA), functional MRCP of the pancreas and pancreatic duct is now a reality. Secretin stimulates exocrine secretion of the pancreas and hence improves visualization of the pancreatic duct by increasing its caliber. After the intravenous administration of 1ml of secretin per 10 kg body weight, thick slab MRCP in the coronal plane is performed and repeated every 15-30 seconds for 10-15 minutes. The effect of secretin stimulation starts almost immediately after intravenous administration and peaks between 2-5 minutes. Around 10 minutes post-injection, the caliber of the main pancreatic duct returns to the baseline value, as the pancreatic juice flows out through the papilla and progressively fills the duodenum [Figure - 3]. However, the high cost of secretin and the lack of a reimbursement mechanism for its use in MRI currently remain impediments for widespread use.

Indications and current clinical role of secretin-MRCP (S-MRCP)

  1. Detection and characterization of pancreatic ductal anomalies.
  2. Evaluating the integrity of the pancreatic duct.
  3. Diagnosing and differentiating benign versus malignant strictures of the pancreatic duct.
  4. Characterizing cyst communication and fistula.
  5. Assessment of pancreatic function and (possibly)  Sphincter of Oddi More Details dysfunction.


MRCP Findings in Biliary Pathologies

A comparison of the common diagnostic modalities for the detection and characterization of biliary tract pathologies is given in the following table [Table - 3]-

Congenital Anomalies

Anatomical variants (trifurcation and left dorsocaudal branch) and common congenital anomalies (left sided cystic duct, aberrant hepatic duct, choledochal cyst, parallel or high cystic duct, agenesis of gall bladder) can be evaluated confidently by MRCP. Currently, MRCP is considered the modality of choice for pre-operative evaluation of the biliary tree, for the diagnosis of congenital lesions and to define the anatomy [Figure - 4].

Biliary Obstruction - Stone, Benign and Malignant Stricture

In the context of biliary obstruction, the role of MRCP is to detect obstruction, define its level and to identify a potential cause. This information can then be used to guide appropriate management.

Stone

MRCP is usually performed to confirm or exclude the diagnosis of CBD stones, suspected on other tests such as USG or CT scan, usually prior to an endoscopic procedure [Figure - 5]. Studies conducted using 2D MRCP, for the detection of CBD stones, have reported a sensitivity, specificity and accuracy of 90%, 88% and 89% respectively, which after the exclusion of stones with diameters smaller than 6 mm, have improved to 100%, 99% and 99% respectively. [2] The detection accuracy of stones <6mm is likely to improve with the newer 3D sequences.

Benign Biliary Stricture

Benign biliary strictures are shorter, smoother and more symmetric; they can be post-inflammatory, congenital or idiopathic. Primary sclerosing cholangitis (PSC) is a commonly described cause of benign biliary strictures. Earlier studies have shown MRCP to be accurate in the detection, classification and staging of primary sclerosing cholangitis with a reported sensitivity and specificity greater than 85% [Figure - 6]. [3]

Malignant Biliary Stricture

MRCP helps to define the extent of biliary strictures and their relationship to critical structures in the vicinity, in patients with known or suspected cholangiocarcinoma affecting the common bile duct [Figure - 7] or the bifurcation (Klatskin tumor) [Figure - 8]. The routine use of gadolinium-based, extra-cellular contrast agents, in addition to the routine MRCP sequences, is encouraged, to allow a more comprehensive assessment of the associated mass, presence of vascular encasement, liver metastases and regional lymph nodes. [4]

MRCP in Pancreatic Pathology

Various imaging modalities are available for evaluating the pancreas and pancreatic duct. [Table - 4] shows a comparison of these modalities along with their strengths and limitations.

Congenital Anomaly of Pancreas (Pancreas Divisum)

Pancreas divisum, although present in 7-10% of the population, may be a cause of recurrent pancreatitis, in some patients. Although, the exact mechanism of pancreatitis in this subset of patients is still debated, the therapeutic benefits of minor papillotomy have been established in this cohort. Therefore, identifying this subset of patients with pancreas divisum and pancreatitis who might benefit from therapeutic intervention is an important indication for MRCP, especially with the use of 3D acquisitions and S-MRCP. Investigators using S-MRCP in this clinical setting have reported an approximately 23% increase in the detection of pancreas divisum after secretin injection [5] [Figure - 9].

Acute Pancreatitis

The role of MRCP is controversial in the setting of acute pancreatitis. Typically, CT is the most commonly used imaging modality in the setting of acute pancreatitis. In patients wherein CT cannot be performed due to iodinated contrast allergy or renal insufficiency, a combination of MRCP and gadolinium-enhanced MRI may help in the detection of pancreatitis and to stratify the patient's risk, based on the presence of necrosis, ductal integrity and hemorrhage. Due to the patients' fragile clinical status and other monitoring needs, obtaining optimal quality MRI images remains a formidable task. MRI is therefore, usually used very selectively, as a problem-solving modality. The use of secretin is not encouraged in the acute setting due to the potential of a flare-up of the inflammation [Figure - 10].

Pancreatic Duct Integrity

The assessment of pancreatic duct disruption or leakage, in cases of trauma and inflammation, helps stratify patients for endoscopic, invasive radiological or surgical intervention. ERCP has long been the modality of choice for this indication; however, S-MRCP is now being considered as the preferred modality. Demonstration of disruption, communication of the pancreatic duct with a collection and increased volumes of extra-pancreatic collections after secretin administration are considered signs of pancreatic duct disruption. In addition, MRCP can also detect complete duct disconnection, by demonstrating the duct below and above the disruption, unlike ERCP where only the duct below the disruption is visualized. In addition, ERCP can potentially introduce infection from the bowel into the previously sterile pancreatic fluid collections. [6]

Chronic Pancreatitis

The diagnosis of suspected chronic pancreatitis has been a challenge with conventional MRCP, because of its previous low accuracy, when compared to ERCP, which has traditionally been considered the gold standard for the evaluation of chronic pancreatitis [Figure - 11]. Now, with the refinement of MRCP techniques and the availability of secretin, the diagnostic accuracy of MRCP has improved substantially. Duct irregularity, filling defects and strictures can now be more confidently studied, along with quantitative assessment of exocrine function. Furthermore, in patients considered for endoscopic management of pancreatic duct stones and strictures, there has been an increase in the use of MRCP to provide a roadmap. The role of S-MRCP is however limited in advanced cases of chronic pancreatitis where diminished exocrine function results in reduced pancreatic fluid production.

Malignant Pancreatic Duct Sticture and Intraductal Papillary Mucinous Neoplasm (IPMN)

Both malignant pancreatic duct stricture [Figure - 12] and cystic lesions of the pancreas are well seen. MRCP is a reliable technique for the comprehensive evaluation of cystic lesions of the pancreas, allowing detection, categorization into a subtype (main duct versus side branch), definition of the extent of main duct involvement and of cyst communication with the duct in cases of side-branch IPMN [Figure - 3],[Figure - 13]. [8] Also differentiation between benign and malignant IPMNs can be performed confidently in most cases, based on cyst morphology, mural nodules or dilatation of the MPD. Furthermore, MRCP is the modality of choice over MDCT for the detection and characterization of small pancreatic cysts.


   Conclusion Top


The combination of conventional and functional MRCP offers a technique for the comprehensive evaluation of a wide range of biliary and pancreatic diseases and their effect on morphology and function. Understanding the clinical perspectives and then optimizing the imaging protocols are the key determinants that influence the development of a successful MRCP practice.

 
   References Top

1.Glockner JF. Hepatobiliary MRI: Current concepts and controversies. J Magn Reson Imaging 2007;25:681-95.  Back to cited text no. 1  [PUBMED]  [FULLTEXT]
2.Guarise A, Baltieri S, Mainardi P, Faccioli N. Diagnostic accuracy of MRCP in choledocholithiasis. Radiol Med (Torino) 2005;109:239-51.  Back to cited text no. 2  [PUBMED]  [FULLTEXT]
3.Fulcher AS, Turner MA, Franklin KJ, Shiffman ML, Sterling RK, Luketic VA, et al . Primary sclerosing cholangitis: Evaluation with MR cholangiography: A case-control study. Radiology 2000;215:71-80.  Back to cited text no. 3  [PUBMED]  [FULLTEXT]
4.Freeman ML, Sielaff TD. A modern approach to malignant hilar biliary obstruction. Rev Gastroenterol Disord 2003;3:187-201.  Back to cited text no. 4  [PUBMED]  [FULLTEXT]
5.Matos C, Metens T, Delhaye M, Le Moine O, Cremer M. Pancreas divisum: Evaluation with secretin-enhanced magnetic resonance cholangiopancreatography. Gastrointest Endosc 2001;53:728-33.  Back to cited text no. 5  [PUBMED]  [FULLTEXT]
6.Kinney TP, Punjabi G, Freeman M. Technology insight: Applications of MRI for the evaluation of benign disease of the pancreas. Nat Clin Pract Gastroenterol Hepatol 2007;4:148-59.  Back to cited text no. 6  [PUBMED]  [FULLTEXT]
7.Larena JA, Astigarraga E, Saralegui I, Merino A, Capelastegui A, Calvo MM. Magnetic resonance cholangiopancreatography in the evaluation of pancreatic duct pathology. Br J Radiol 1998;71:1100-4.  Back to cited text no. 7  [PUBMED]  [FULLTEXT]
8.Sugiyama M, Atomi Y, Hachiya J. Intraductal papillary tumors of the pancreas: Evaluation with magnetic resonance cholangiopancreatography. Am J Gastroenterol 1998;93:156-9.  Back to cited text no. 8  [PUBMED]  

Top
Correspondence Address:
Dushyant V Sahani
Abdominal and Interventional Radiology, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Boston, MA 02114
USA
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0971-3026.36869

Rights and Permissions


    Figures

  [Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6], [Figure - 7], [Figure - 8], [Figure - 9], [Figure - 10], [Figure - 11], [Figure - 12], [Figure - 13]
 
 
    Tables

  [Table - 1], [Table - 2], [Table - 3], [Table - 4]

This article has been cited by
1 An Update to the Management of Pediatric Acute Pancreatitis
Maisam Abu-El-Haija,Tom K. Lin,Joseph Palermo
Journal of Pediatric Gastroenterology and Nutrition. 2014; : 1
[Pubmed] | [DOI]
2 Diagnostic value of magnetic resonance cholangiopancreatography in cholestatic jaundice
Elsayed, E.Y. and Amin Abu El Maati, A. and Mahfouz, M.
Egyptian Journal of Radiology and Nuclear Medicine. 2013; 44(2): 137-146
[Pubmed]
3 Diagnostic value of magnetic resonance cholangiopancreatography in cholestatic jaundice
Engy Yousry ElSayed,Amal Amin Abu El Maati,Mohamed Mahfouz
The Egyptian Journal of Radiology and Nuclear Medicine. 2013; 44(2): 137
[Pubmed] | [DOI]
4 Magnetic resonance cholangiopancreatography in conjunction with 3D for assessment of different biliary obstruction causes
Doaa Ibrahim Hasan,Hosam Nabil Almassry
The Egyptian Journal of Radiology and Nuclear Medicine. 2010; 41(4): 483
[Pubmed] | [DOI]



 

Top
 
  Search
 
    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
    Email Alert *
    Add to My List *
* Registration required (free)  


    Introduction
    Techniques
    Conclusion
    References
    Article Figures
    Article Tables

 Article Access Statistics
    Viewed8734    
    Printed146    
    Emailed4    
    PDF Downloaded1312    
    Comments [Add]    
    Cited by others 4    

Recommend this journal