Magnetic resonance cholangiopancreatography ppt

Non Invasive Method to Image the Hepatobiliary and pancreatic duct using MRI Protocols

1. MAGNETIC RESONANCE CHOLANGIOPANCREATOGRAPHY ( MRCP) JJSJNANJan Anjan Dangal B.Sc.Medical Imaging Technology 3rd Year student National Academy of Medical Sciences,Kathmandu, Nepal

2. Hepatic , pancreatic and biliary duct information Heavily T2 weighted sequences, acquired with thin slice sections or thick slabs or both Contrasting mechanism = inherent biliary fluid (MR Hydrography) Better include sequences to evaluate contents of upper abdomen essentially, liver and pancreas: to exclude presence of any pathology associated witht these organs that may affect calibre and condition of any duct. This is because pathology of these organs may manifest itself as duct disease or can directly impinge upon and affect these ducts

3. Advantage High diagnostic accuracy to assess the ducts ( hepatobiliary and pancreatic) and associated organs ( liver, gall bladder and pancreas ) Non invasive and less costly than ERCP Less examination time, few staff and no ionizing radiation

4. Patient Preperation Need to fast : ensure gallbladder, hepatobiliary and pancreatic ducts are filled with fluid and their maximum distension NPO, 4 hrs prior to procedure Permitted to drink water and routine medication

5. Breathing Instruction Clear explanation of breathing instruction is crucial which determines overall success or failure of examination

6. It is a MRI technique used to investigate Biliary and Pancreatic pathologies. MRCP uses the inherent tissue contrast between fluid filled structures and the surrounding solid organs to generate images only of the fluid containing structures like the gallbladder, bile duct and pancreatic duct. No contrast intravenous or oral contrast is necessary(ideal for patients with history of allergy to iodine contrast agent MRCP is completely a non invasive examination. 5.

7. Ultrasound and CT scans are most frequently used in the initial evaluation of jaundice which can be categorized as hepatic or biliary . When a “road map” of biliary tree and pancreatic duct is needed , ERCP or MRCP will be imaging of choice. It was claimed that MRCP has been shown to be equal to ERCP, with nearly 95% accuracy in the depiction of ductal anatomy, obstruction dilation , and CBD stones and pseudocyst. (Chan YL, Rad.1996:200:85-89,Lee, MG, Rad .1997:202, regan f, AJR )

8. WHAT IS MRCP MAGNETIC resonance cholangiopancratography (MRCP) is a radiologic technique that produces images of the pancreatobiliary tree that are similar in appearance to those obtained by invasive radiographic methods, such as endoscopic retrograde cholangiopancreatography (ERCP).

9. BUT ERCP IS GOLD STANDARD ERCP continues to have certain advantages: therapeutic maneuvers can be performed at the time of the diagnostic procedure, manometry can be performed, and the ampulla can be directly visualized. In addition, the radiographic images obtained with ERCP have higher spatial resolution.

10. Principle MRCP is based on heavily T2 weighted pulse sequence in which stationary fluid like bile and pancreatic secretions and fluid within the bowel have high signal intensity,while solid organs have low signal intensity and blood vessels have no measureable signal. It makes use of heavily T2 weighted pulse sequence ,thus exploiting the inherent differences in the T2 weighted contrast between stationary fluid filled structures in the abdomen ( which have a long T2 relaxation time ) and adjacent soft tissue ( which has a much shorter T2 relaxation time ).

11. 3. Static or slow moving fluids within the biliary tree and pancreatic duct appears of high signal intensity on MRCP, whereas surrounding tissue of reduced signal intensity. 4. Since a large component of residual background signal in the abdomen arises from fat, magnetic resonance techniques that allow the selective suppression of fat can substantially reduce the background signal.

12. Anatomy of Hepatobiliary and Pancreatic system

13. Enlarged view of one portion of a single liver lobule The hepatocytes secrete a fluid called bile into a network of narrow channels between the opposing membranes of adjacent liver cells. These passageways, called bile canaliculi, extend outward, away from the central vein. Bile contains acidic bile salts. Bile canaliculi merge to form bile ductules , which carry bile to bile ducts in the nearest portal area. Bile plays an important role in the digestion of fats in the small intestine.

14. Bile, formed within the liver, is collected for transport to the gallbladder by the intrahepatic bile ducts. The intrahepatic bile ducts run beside the hepatic arteries and portal veins throughout the liver parenchyma. The intrahepatic ducts merge into successively larger ducts as they follow a course from the periphery to the central portion of the liver, eventually forming the right and left hepatic ducts

15. The right and left hepatic ducts unite at the porta hepatis to form the proximal portion of the common hepatic duct (CHD), which marks the beginning of the extrahepatic biliary system

16. MRCP Procedure and Technique Patient preperation : 4 -6 hours fasten No oral contrast preperation Using phased- array body coils ( Anterior and posterior cil coverages) Heavily T2 - weighted sequences : static fluid bright ( endogenous contrast ) Technique of Acquisition : Breath Hold Technique ( short time ) Non Breath Hold Technique ( respiratory triggering )

17. Protocol:Patient Preperation and Instruction Patients are fasted for 4 h prior to the study in order to reduce fluid secretions within the stomach and duodenum, reduce bowel peristalsis and promote gallbladder distension.Throughout this period, the patient is permitted to drink clear fluids only (namely water), and routine medication is allowed as per normal. The next important step is to instruct the patient on the specific breathing instructions and inform the patient that they will hear the radiographer’s voice through their headphone or speaker prompting them when to suspend expiration.

18. If the breath hold technique is not adequate, then the CBD and the main pancreatic duct may not appear to unite or may appear either stenotic or dilated. The next critical component is positioning of the patient, the respiratory bellows and the imaging coils. At this point, the adult patient should be lying supine on the MRI table positioned appropriately over the posterior half of the body array coil and also such that their feet will be entering the bore of the magnet first.

19. To position the respiratory bellows correctly, the radiographer must first observe the rise and fall of the patient’s chest and abdomen with their breathing The respiratory bellows need to be positioned across the point where the maximum difference in rise and fall occurs. Once the respiratory bellows are positioned, the radiographer must then observe the respiratory waveform that appears on the operator’s console

20. IMPORTANCE OF ORAL CONTRAST IN MRCP Overlap between high signals from the pancreaticobiliary system and from the gastrointestinal tract (GIT) (stomach, duodenum and proximal intestine), is a recognized limitation of MRCP and may mimic pathology P roblem may be overcome by multiple acquisitions of the same sequence in multiple planes, or by using a negative oral contrast agent to shorten the  T 2  relaxation time, and hence reduce the  T 2  signal, of the fluid in the bowel and improve image quality , provide good visualization of the bile and pancreatic ducts without superimposed high signal from the GI.

21. Advantage Increased the visibility in the common bile duct, cystic duct and the pancreatic duct. Suppression of signal in gastrointestinal tracts. Elimination of overlapping signals over the pancreatic biliary tract.

22. Negative oral contrast Appears predominantly dark on MRI . These agents are small particulate aggregates often termed as super magnetic iron oxide Produce spin-spin relaxation effects i.e. local field in homogeneities , which results in shorter t1 and t2 relaxation times .

23. Blueberry juice Blueberry juice is inexpensive drink . Suppress the signal from stomach and duodenum on T2W imaging in MRCP due to the paramagnetic properties of its relatively high manganese content reducing the  T 2  (and  T 1 ) recovery times. Therefore it may act as an effective negative contrast agent on T2W imaging (and a positive oral contrast agent on T1W imaging) .

24. Pineapple Juice The negative contrast effect of Pineapple Juice is due to shortening of the  T 2  relaxation time resulting in reduced signal intensity from fluid in the GIT on heavily  T 2  weighted imaging. This effect is likely to be due to the paramagnetic effect of the relatively high concentration of manganese in Pineapple Juice.

25. (a) Pre and (b) 15 min and (c) 30 min post pineapple juice (PJ) magnetic resonance cholangiopancreatography (MRCP) images. In (a) the middle portion of the common bile duct and body and tail of the pancreatic duct are not clear due to high signal in the duodenal cap and stomach. In (b) and (c) the high signal in the stomach and duodenum are eliminated almost completely, and the whole pancreaticobiliary structure is clearly visualized.

26. Patient positioning Supine Longitudinal alignment light lies in the mid sagittal plane Horizontal alignment light pass through the 3 rd lumber vertebra or lower costal margin . Position the patient over the spine coil and place the body coil over the upper abdomen( nipple down to iliac crest )

27. Phased Array coil Phased Array coil systems are collections of small surface coils whose signals may be combined but generally feed into independent receiver circuitry.   These are multi-channel coils with each channel having its own receiver.  A 4, 8, 16, 32, etc. channel system increases the number of receiver channels . By combining multiple small coils into large arrays it is possible to obtain  — high signal-to-noise and  large fields of view.

28.  Placement of bellows and belly band for respiratory gating 

29. Patient setup for respiratory gating.

30. Breath holding Breath-hold techniques can significantly reduce sequence times for T2 imaging and can be the only option for good-quality T1 weighted imaging. Breath holding can freeze the abdominal wall motion and enable us to image them almost motion free. Even though a routine breath-hold scan can be on the order of 20 s or so, the breath-hold times for elderly and sick patients would be considerably less. To maintain the quality of breath-hold scans, strongly recommend practicing the breath holding on the MR table before the actual scan, so that the patient can understand what is required.

31. Breath holding Breath holding in inspiration or expiration seems to be a choice of each site depending on their experience. For longer breath holds, the patient can inhale oxygen if you have the setup in the room. The oxygen supplement can increase the breath holding ability of the patients.

32. Respiratory gating Respiratory Gating -Synchronization of MRI signal acquisition with the respiratory cycles. The synchronization can be prospective or retrospective. it  is a respiratory motion reduction technique respiratory gating requires images to be obtained only during limited portions of the respiratory cycle and significant time penalty up to 3 times more time consuming than ungated imaging .

33. Respiratory gating and bellows placement : -options for patients unable to hold breath. -improve the image quality for T2 sequences due to longer TR and ability to do longer acquisition times. Respiratory gating cannot be used with T1 weighted acquisitions. Because the significant increase in TR time with the respiratory gating can destroy the T1 contrast completely.

34. Respiratory gating waveform window

35. Sequences Heavily T2-weighted images were originally achieved using a gradient-echo (GRE) balanced steady-state free precession technique. A fast spin-echo (FSE) pulse sequence with a long echo time (TE) was then introduced shortly after with the advantages of a higher signal-to noise ratio and contrast-to-noise ratio, and a lower sensitivity to motion and susceptibility artefacts.

36. MODIFIED FSE SEQUENCE Rapid Acquisition with rapid enhancement ( RARE ) half-Fourier Acquisition single shot turbo spinecho ( HASTE) Fast recovery fast spin echo (FRFSE)

37. Breathe Hold using a single shot approach Non-breathe hold technique using a respiratory gating Images Obtained either 2D or 3D

38. Secretin Stimulated MRCP Secretin is an endogenous hormone normally produced by the duodenum, which stimulates exocrine secretion of the pancreas . When given as a synthetic agent intravenously (1 ml/10 kg body weight), it improves the visualisation of the pancreatic duct by increasing its calibre. Pancreatic juice flows out of the major duodenal papilla to progressively fill the duodenum. Perform a thick slab MRCP in the coronal oblique plane at baseline and then at 1, 3, 5, 7 and 9 min following injection.

39. Its effect starts almost immediately and peaks between 2 to 5 mins. By 10 min, the calibre of the main pancreatic duct should return to baseline with persistent dilatation of >3 mm considered abnormal.

40. Example of a normal secretin-stimulated MRCP in apatient being investigated for sphincter of Oddi dysfunction, with idiopathic dilatation of theCBD. a Thick coronal slab at baseline shows the pancreatic duct is of normal caliber (arrow) with little secretions in the duodenum(D); b) at 3 min there is progressive filling of the duodenum (D) due to an increase in pancreatic secretions and the pancreatic duct has become more prominent(arrow); c) at 9 min, the pancreatic duct has returned to baseline calibre (arrow)

41. Indication for Secretin stimulated MRCP detection and characterisation of pancreatic duct anamolies and strictures evaluation of integrity of pancretic duct characterisation of any communication between pancreatic duct and pseudocyst and fistulas assesment of pancreatic function and sphincture of oddi dysfunction

42. Functional MR Cholangiography involves the use of MR lipophilic paramagnetic contrast agents, which when given intravenously, show hepatobiliary excretion. Contrast agents includes : gadobenate dimeglumine (Gd-BOPTA, Multihance; Bracco Imaging, Milan, Italy), gadolinium ethoxybenzyldiethylenetriamine penta-acetic acid (Gd-EOB-DTPA, Primovist; Bayer-Schering Pharma, Berlin, Germany) and, historically, mangafodopir trisodium (Teslascan; GE Healthcare, Oslo, Norway).

43. Delayed imaging in the axial and coronal plane, performed between 10-120 min following intravenous administration, normally results in hyper-intense bile on 3D T1-weighted fat-saturated GRE images. The signal to- noise ratio is higher than conventional T2-weighted MRCP, allowing better delineation of the bile ducts.

44. It is more expensive than conventional T2-weighted MRCP and only thebiliary tree is depicted. For these reasons, most centres continue to use conventional T2-weighted MRCP.

45. MRCP does have a number of advantages, as follows: better demonstrates communications between cystic lesions and draining bile ducts in the diagnosis of congenital biliary disorders it helps to distinguish true obstruction in a dilated biliary system (where delayed or no biliary excretion is demonstrated) from pseudo-obstruction and it can demonstrate active extravasation of contrast in suspected bile leaks

46. Another advantage is that these gadolinium-based hepatobiliary-specific contrast agents initially distribute in the extracellular fluid compartment, thus allowing for early dynamic pre-contrast and post-contrast images in the arterial, portal venous and equilibrium phase prior to the functional cholangiogram.

47. MRCP protocols and Dilemas 3 Plane localizer 3 plane localizer with T2 weighting. This is typically performed using a SSFSE or balanced SSFP sequence. If respiratory gated sequences are to be used this is typically done twice, one at end expiration (or inspiration) and once during free breathing so that liver location can be assessed in both states. The advantage of T2 weighted imaging is that diagnostic information can be acquired as part of the localizer sequences.

48. 2D SSFSE/HASTE: It is important to obtain a set of images without fat suppression to define anatomy surrounding the bile ducts. Axial and Coronal

49. Radial Slab: This consists of a series of SSFSE slab images with a thickness of about 4cm obtained centered around the common hepatic duct.

50. 3D T2: The use of 3D T2 sequences has been optimized with fast recovery and variable flip angle approaches (SPACE/CUBE) and allows for near isotropic imaging of the biliary tree. Theis sequence can produce very nice 3D reconstructions of the biliary tree however require very robust respiratory gating.

51. Others Addional Sequences Balanced SSFP ( true FISP/FIESTA ) This sequences gives a relative T2/T1 weighting and results in bright blood. This can be helpful in defining anatomic relationships. It can also help eliminate pulsatility artifacts in the bile ducts sometimes seen with SSFSE sequences. The sequences is SNR efficient and thus high spatial resolution images can be obtained that appear sharp.

52. DWI Diffusion weighted imaging can be valuable in detecting mural pathology in the duct wall as well as pancreatic inflammation or tumor. B values of 50s/mm2 or higher will results in elimination of signal from portal vessels which helps in assessment of periportal pathology near duct walls such as periductal inflammation or tumor

53. 3D T1 (VIBE , THRIVE, LAVA) with fat saturation Intraductal stones may be of high signal on T1 weighted images. In addition intraductal air is very dark as compared to stones and these sequences can help distinguish intraductal air from stones. Pancreatic pathology often is dark against the normal bright T1 of the pancreatic parenchyma. For this reason a T1 weighted image through the liver and pancreas is an important part of the MRCP exam even if contrast is not being administered.

54. Slice planning

55. Protocol T2W SSH- FS Tra T2w FS MSH Tra T1 inphase T1 opposed T2 W FS cor BTFE FS Tra DWI_RT Tra MRCP - SSH RA Geo4 T2W FS SSH T2W FS SSH 1 FS MSH Tra

56. Ref MRI master.com Handbook of MRI Slideshare