The diagnostic MRCP examination: overcoming technical challenges to ensure clinical success
School of Medical Sciences, Medical Radiations, RMIT University, Victoria, Australia
The magnetic resonance cholangiopancreatography (MRCP)
examination has all but replaced the diagnostic endoscopic retrograde
cholangiopancreatography (ERCP) examination for imaging the biliary tree and
pancreatic ducts in many practical aspects of the clinical setting. Despite
this increase in popularity, many magnetic resonance imaging (MRI)
radiographers still find aspects of the MRCP examination quite challenging. The
aim of this tutorial paper is to provide useful technical advice on how to
overcome such perceived challenges and thus produce a successful diagnostic
MRCP examination. This paper will be of interest to novice MRI radiographers
who are at the beginning of their learning curve in MRCP examination. Other MRI
radiographers who are interested in practical tips for protocol variations may
also find the paper useful. � 2008 Biomedical Imaging and Intervention
Journal. All rights reserved.
Keywords: MRCP; MRI; sequences; ERCP; radiographer; hydrography
A comprehensive diagnostic magnetic resonance
cholangiopancreatography (MRCP) examination should provide maximum information
pertaining to the hepatic, biliary and pancreatic ducts. Common protocols of
the MRCP examination include heavily T2-weighted sequences [1-8], acquired
either with thin slice sections or thick slabs or both [9-12]. As the inherent
biliary fluid is used as a contrasting mechanism, the broad new term of
magnetic resonance hydrography has been coined in recent years [13-15]. However,
if a patient has been scheduled for an MRCP examination, which may usually last
for thirty minutes, it would be wise to include a few dedicated (initially, non-intravenous
contrast media enhanced) magnetic resonance imaging (MRI) sequences to evaluate
the contents of the upper abdomen, essentially the pancreas and the liver. Some
authors [2, 5, 8, 16-20] use the acronyms MRCP and MRI to emphasise these
separate and distinct aspects of imaging . The rationale behind acquiring
images of the pancreas and liver is to exclude the presence of any pathology
associated with these organs that may affect the calibre or condition of any
ducts [2, 5, 6-7, 16-17, 18, 21,]. This is because pathology of these organs
may manifest itself clinically as duct disease or can directly impinge upon,
and affect, these ducts .
Since its clinical introduction well over a decade ago
, the MRCP/MRI examination has played at least two very important roles.
Firstly it has provided both clinicians and patients with a highly accurate
diagnostic test to assess the ducts (hepatobiliary and pancreatic) and
associated organs (liver, gall bladder, pancreas) . The MRCP/MRI examination
is non-invasive [8, 9, 20, 22, 23] and less costly  than the diagnostic
aspect of an endoscopic retrograde cholangiopancreatography (ERCP). Comparatively,
the MRCP/MRI requires less examination time, fewer staff, and involves no
ionising radiation . In addition, the ERCP has associated morbidity and
mortality rates, albeit relatively low [4, 24-26]. From the latter arises the
second important role played by the MRCP/MRI examination: it has allowed more
accurate selection of patients who would benefit from surgery [16, 18] and/or
the therapeutic component of the ERCP. Thus it has prevented patients from
undergoing an unnecessary invasive diagnostic ERCP procedure . Aside from
enhancing patient safety, MRCP/MRI has resulted in saving staff time, material
resources and finance in the long-term  (although to date, there has not
been a definitive agreed-upon dollar value published, or a formula that
clinical centres can use to calculate such savings). This should lead to
improved use, and allocation of assets and resources can therefore be directed
to more urgent areas of clinical practice.
This tutorial paper provides a synopsis of current
practice and emerging trends. It describes the pulse sequences commonly adopted
in a MRCP examination, with the focus on the rationale of the protocol as well
as practical suggestions for MRI radiographers in ensuring a successful
Review of relevant Anatomy
Understanding and appreciating the complexity of anatomy
is an essential factor to the success of any MRI examination. The reader is
referred to any reputable text to review the anatomy of the hepato-biliary
Patient Preparation and Instructions
To ensure that the gall bladder, hepatobiliary and pancreatic
ducts are filled with fluid and at their maximum distension, the patient would
need to fast. It is recommended that the patient be nil per oral for at least
four hours prior to commencing the examination [2, 4, 10]. Throughout this
period, the patient is permitted to drink clear fluids only (namely water), and
routine medication is allowed as per normal.
When the patient arrives for their appointment, the
radiographer must follow the centre�s policy in relation to safety screening
and this can vary from one centre to another; however all reasonable
precautions must be taken to ensure that the patient is safe to enter the MRI
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. The authors strongly believe that clear explanation of
breathing instructions is a crucial step that determines the overall success or
failure of the examination. This is because the main pancreatic duct is very
susceptible to respiratory motion , as suspended respiration is more
consistent for the patient to perform rather than suspended inspiration. Thus,
it is advisable to practice the respiratory motion with the patient at this
point. In the authors� opinion, the approach which seems to be most successful
is to instruct the patient to �breathe in, breathe out, breathe in and breathe
out, and stop.� Inform them that they are expected to suspend expiration for
approximately fifteen seconds and that the hyperventilation breathing should
allow them to fill their lungs with air to comfortably sustain the period of
suspended expiration. Mitchell  also concurs that suspended expiration is
more consistent, and provides less motion variation, whereas full inspiration
should be reserved for situations where the lung diaphragm needs to be in a
more inferior position. It is imperative that the patient understands their
role and that their co�operation and active participation is needed to ensure
overall diagnostic success. 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. 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 . It is wise to repeat the
breathing instructions while observing the patient�s chest and abdomen. 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. It must display the distinct rise and fall
wave patterns and these patterns need to be regular. If the patient has
breathing difficulties or can only take shallow breaths, one method to ensure a
respiratory wave pattern is to place the respiratory bellows diagonally
across the region (either the chest or the abdomen) that corresponds with the
patient�s breathing. From the authors� clinical experience, this will ensure
that any respiratory motion will be detected. However, when the respiratory
pattern from this technique is observed on the console monitor, it may only
display shallow peaks.
Next, pads or sponges are placed alongside the respiratory
bellows. These prevent the respiratory bellows from being compressed by the
weight of the anterior half of the imaging coils. If the respiratory bellows
were to be compressed they would be unable to detect the patient�s respiratory
motion or may not accurately represent the respiratory waveform pattern. This
will then have an adverse affect on the pulse sequences which are required with
the use of respiratory triggering.
This section focuses on the pulse sequences used, their
weightings and image planes, and most importantly, validates the reasons for
using the parameters to attain maximum diagnostic information. It should be
noted that these imaging tools vary from one clinical centre to another [2, 8, 35]
and that there are numerous valid reasons for such differences. These may include
the preference of the reporting radiologist, adhering to an already established
protocol which may be a part of an ongoing prospective study; pulse sequences
available from a particular manufacturer, and pulse sequences and technical
capabilities available or inherent to a particular software operating platform.
The following discussion relates to pulse sequences available on the GE 1.5
Tesla twin speed magnetic resonance (MR) scanner using the HDx operating
platform (General Electric Medical Systems, Wisconsin, USA).
1. Three Plane Localiser
Always commence with a T1-weighted three plane localiser
as this sequence provides low spatial resolution images demonstrating anatomy
for orientation purposes. These images are thus used for identifying the
initial required anatomical structures for subsequent planning or prescription
of the diagnostically proper pulse sequences. This sequence should be acquired
with the patient in suspended expiration so that these low resolution images
are not further degraded by respiratory motion artifacts.
2. Axial 2D FIESTA (Fat Suppressed)
The purpose of this sequence is to obtain imaging of the
hepatic ducts, biliary tree and pancreatic duct in the transverse plane. Fat
suppression improves conspicuity of solid lesions and also minimises phase
ghosting artefacts from subcutaneous and intraperitoneal fat. This is of
greater importance in respiratory triggered sequences . The transverse or
axial plane is the most common and therefore familiar of all the imaging planes
and it is an orientation which we can easily recognise. By varying the required
technical factors a balance of acceptable image quality and scan time can be
achieved. Typically, the scan time achievable is approximately between fifteen and
twenty seconds. From recent clinical experience, the authors find that most
patients are able to hold their breath for this duration regardless of their
presenting pathology. The FIESTA pulse sequence provides excellent contrast
differentiation of the fluid-filled structures (ducts and gall bladder) with
the surrounding anatomy (liver and pancreatic tissue) which includes fat
suppression . This sequence serves to demonstrate the gall bladder, the
cystic duct and the hepatic and pancreatic ducts. The first prescribed slice
should be almost at the most superior aspect of the liver to ensure that the
majority of the right and left hepatic ducts are captured. The most inferior
prescribed slice should be located into the lumen of the duodenum to ensure
that the sphincter of Oddi is captured as well as any variation in the location
of the union of the pancreatic duct. These two reference points are indicated
in Figure 1, with their corresponding axial images depicted in figures 2 (a)
and (b). This scanning range, plane and sequence-weighting is designed to
provide coverage and assessment of the entire biliary tree ducts, the main
pancreatic duct and to determine the location of any biliary stones (which
appear as hypo-intense) and strictures [4-5,9,11-12,33]. A relatively high
receive bandwidth (RBW) is used to minimise the echo spacing . This serves
two main purposes. Firstly, it allows the designated number of prescribed
slices to be acquired at an overall shorter scan time. Secondly, it minimises
distortion type artefacts such as those arising from metal surgical clips from
prior surgery. Additionally, if the RBW had not been as wide, it would not have
allowed the same number of prescribed slices scanned with a shorter acquisition
time. The down side to an increased receive bandwidth is that it captures a
greater amount of noise relative to the signal. However, to the naked eye, this
may neither be noticeable nor hinder the image quality for diagnostic reporting
Variation from the norm: possible modification of protocols
As indicated, one of the easiest ways to manipulate
acquisition time would be to adjust the RBW. If the patient is large and
additional slices need to be prescribed for anatomical coverage, then the RBW
can be increased to accommodate for this. The downside is that this will
increase the noise content inherent within the image and adversely affect the
signal-to-noise ratio (SNR). However, it can be argued that this level of
increased noise may not degrade the image significantly to adversely impinge
upon the diagnostic quality for the reporting radiologist. An increased RBW
also reduces the echo spacing and can thus minimise the image appearance of
susceptibility artefacts (such as arising from metal surgical clips). Acquisition
times of approximately twenty seconds can be achieved and approximately twenty
slices can be prescribed, with the following parameters: a RBW of approximately
85 kilohertz, a slice thickness of 8 millimeters, a spacing of 2 millimeters
and a matrix of 256 x 256.
3. Coronal 2D FIESTA (Fat Suppressed)
The reasons for performing the coronal sequence are
exactly the same as for the axial series, but another view of the relevant
anatomy is obtained. In particular, this plane is useful in adding assessment
value to the condition of the CBD, cystic duct, hepatic ducts and the gall
bladder; with pathology affecting the ampulla of Vater particularly well noted
. The scanning range should have the prescribed slices commencing within the
lumen of the duodenum (to visualise any biliary fluid passing through the
sphincter of Oddi) and ending at almost the most anterior surface of the liver
(to ensure that the intra hepatic ducts are included). The start and end slice
prescription is indicated in figure 3 and their resulting coronal images are shown
in figures 4 (a) and (b). This scanning range should also provide coverage for
the pancreas. However, it is wise to confirm the inclusion of pancreas by
scrolling through the axial images with the overlying prescribed coronal slices
to ensure that no anomalies or pathology has directed or positioned the
pancreas out of this scanning range. Figure 5 is an example of a coronal 2D
FIESTA fat suppressed image demonstrating multiple stones within the gall
Variation from the norm: possible modification of protocols
The factors concerning the RBW in the Coronal 2D
FIESTA is applicable to all sequences. Since this sequence is acquired
in the coronal plane, ensure that all precautions have been taken with the
field-of-view (FOV) so that phase wrap does not occur. It is likely that a banding
or moir� pattern  artifact will appear at the corners of the image,
particularly at the shoulder and hip regions. This artifact is common on
gradient echo-based sequences with a large FOV and the artifact will almost
always occur at the periphery of the FOV, in particular at the corners of the
image . If the patient�s arms, for example, are in contact with the magnet
bore, this would mean that anatomy from outside the FOV can produce a signal
that then enters the FOV. Furthermore, the banding, or black and white, effect
is due to inhomogeneity of signal being in and out of phase . The most
immediate action to take is to ensure that the patient�s anatomy is not in
contact with the magnet bore. Contact with the magnet bore also has potential
consequences for heating and skin burns. Therefore, ensure that thermal
resistant material is placed between the patient and the magnet bore. Otherwise,
an alternative pulse sequence can be considered; most likely a spin echo-based
sequence with factors altered to offer comparable signal contrast such as to
emphasise the fluid-filled ducts and gallbladder.
4. Axial T2-Weighted FRFSE Respiratory Triggered
The success of this sequence is a direct result of how
well the patient has been prepared and how closely they are able to follow and
maintain the correct breathing instructions. Being a T2-weighted sequence, this
sequence is valuable for aiding characterisation of extraductal (contained
within the liver and pancreas) solid and cystic masses and provides
supplementary information regarding fluid within the ducts and any other
pathologically associated fluid collection . The scanning range for this
sequence is as per the axial 2D FIESTA (fat suppressed) pulse sequence described
The purpose of this respiratory triggered sequence is to
acquire images of the biliary tree with improved spatial resolution, while
maintaining an acceptable level of contrast resolution  that is similar to
the fat suppressed FIESTA sequence. Some studies have demonstrated that
respiratory triggered sequences such as this can demonstrate spatial resolution
greater than that achievable with standard breath-hold sequences . To
achieve this, the MRI system must have dedicated gradient coils, associated
hardware and dedicated software to allow for parallel imaging, and
multi-channel receiver (surface) coils to be used. Compared to non-parallel
imaging techniques, parallel imaging may have an inherently lower signal-to-noise
ratio value [32, 37]. However, the two main advantages that make this sequence
justifiable are the improved imaging times [32, 34, 36-37] that come with
parallel imaging techniques and the highly prominent contrast demonstrated
between the fluid-filled ducts and the background tissue .
Respiratory triggered sequences provide improved overall
visualisation of the pancreatobiliary system  and in particular the main
pancreatic duct . This duct is particularly difficult to image due to its
relatively large movement with the patient�s rhythm of respiratory motion and
it is this respiratory triggered sequence which may provide the greatest
information on the condition and calibre of the main pancreatic duct. In
addition, if there is respiratory motion along the phase direction, then phase
mismapping will result [34, 38, 40]. Therefore, it is imperative that
respiratory motion is maintained by the patient in a constant rhythm, and that
respiratory monitoring and triggering are performed accurately. Figure 6
demonstrates an axial T2 weighted FRFSE respiratory triggered image showing
multiple stones within the gall bladder.� It also serves to demonstrate the
diagnostic quality of the sequence and overall image sharpness.
Variation from the norm: possible modification of protocols
This sequence becomes difficult to perform if the patient
has shallow breathing, an irregular breathing pattern or if the bellows are not
positioned correctly. Respiratory triggering synchronises the radiofrequency
excitation pulse with a phase point of the patient�s respiratory motion [34, 38].
This implies that each prescribed slice should be acquired at the identical
point of the respiration cycle. There are two inherent and interlinked
challenges of this method: the overall scan time and resulting image contrast
may be affected because the repetition time (TR) is determined by the patient�s
breathing pattern, that is, either quick or slow. If the patient is capable of
breathing in a regular fashion, then this should be encouraged [34, 38]. Factors
that may need to be adjusted can be found in the Gating Screen of the
operator�s console. The most important parameters are the number of Respiratory
Intervals, the Trigger Point, the Trigger Window and the Inter-sequence Delay. The
Respiratory Intervals allows the radiographer to select the maximum number of
breaths that the patient can take for the system to generate image data from
one prescribed slice, therefore the greater this value, the longer the overall
scan time will be [34, 38]. The Trigger Point allows the radiographer to
determine where along the ascending part of the respiratory waveform peak the
data acquisition should take place; and this is usually expressed as a
percentage value. If a patient is taking shallow breaths, then a lower value (for
example 10% above the trough or baseline) may be suitable, whereas if a patient
has comparatively deeper and regular breaths, then a trigger point of 30% to
40% may be more appropriate. The Inter-sequence Delay is a time delay that is
added to the end of the TR. This is done so that the radiofrequency excitation
pulse that is delivered to commence the pulse sequence will actually coincide
with the patient�s breathing cycle and thus minimise phase mismapping [34, 38].
Besides adding time to the overall scan period, this time delay also needs to
be added because a patient�s breath cycle is longer than the TR of the
sequence. The option available for this is usually 'minimum' or 'even space'. The
authors recommend 'minimum' as this is an appropriate balance between achieving
a respectable overall scan time (of under four minutes) and synchronising the
commencement of the pulse sequence with the patient�s breathing cycle in order
to minimise phase mismapping.
5. Coronal Oblique 3 Slab MRCP
The underlying concept is to image fluid within the ducts
while suppressing signal from non-fluid structures . The main aim of this
classic MRCP sequence is to demonstrate ductal fluid as hyperintense while
filling defects, such as those caused by stones, are displayed as hypointense
. Traditionally, a set of radially oriented thick slab MRCP images were
obtained and may still be the case in many centres [44, 47]. It has been
somewhat successful and so it is understandable that centres continue to use
this approach. This may be of benefit when anatomical structures are difficult
to identify on axial images (perhaps due to prior surgery or congenital
anomalies) or because of an advanced stage of pathology which results in severe
distortion of the relevant anatomical structures. However, the authors believe
that this approach, if used for every case, may falsely lead to an
oversimplification of the MRCP procedure. It may even be considered as a novice
approach since it is not targeted directly at the anatomical structures
specific to the biliary tree. An approach which is directed more at the anatomy
of the biliary tree, would be to obtain three specific images aimed at the CBD,
cystic duct and the pancreatic duct. This procedure is described as follows.
Firstly, from the axial 2D FIESTA F/S images, identify the
CBD. This should be easy provided that the patient has fasted adequately, the
CBD is filled with bile and fat suppression has worked successfully on the
axial 2D FIESTA sequence. Prescribe the first slice straight through the CBD in
a coronal fashion as depicted in figure 7.
Next, the second slice is prescribed parallel to the
cystic duct. Identification of the cystic duct is easier to achieve when the
gall bladder is still in situ. Once again, if the patient has fasted the gall
bladder should be easily identifiable (except in pathologies such as cystic
fibrosis where the gall bladder is invariably contracted and thick walled
). The cystic duct connects the neck of the gall bladder to the CBD,
therefore the second slice is prescribed as closely as possible along this line,
also indicated in figure 8(a) and (b).
If the patient has had the gall bladder surgically
resected, there may still be a segment of the cystic duct remaining. This is
where an element of difficulty is introduced. From the authors� experience, the
best, most accepted and safest approach is to locate the point along the
hepatic duct where the cystic duct forms its union with the CBD. If the
junction of the hepatic and CBD cannot be clearly identified, then the next
likely solution would be to identify the junction or the region where the
first, fourth and fifth liver segments meet. At this point or at the junction
of the hepatic and bile ducts, prescribe a slice approximately 45 degrees to
the para-coronal plane (used to prescribe the first slice). Bearing in mind
that the gall bladder lies on the postero-inferior surface of the right lobe
below the porta hepatis and the quadrate lobe; this angle or any variation to
this, should be approximate to the angle that the cystic duct makes with the
neck of the gall bladder.
The third slice needs to be prescribed parallel through
the pancreatic duct along the head of pancreas, figure 9(a) and (b). A normal
pancreatic duct has a diameter of 2-3 mm within the head of pancreas. The
pancreatic duct needs to be identified on an axial image and the best axial
sequence for this will either be the axial 2D FIESTA (fat suppressed) or the
axial T2 respiratory triggered. Therefore, it would be advisable to review
images from both of these sequences to determine which slice best demonstrates
the pancreatic duct.
In recent years, depending on the clinical protocol,
secretin is used to help dilate the pancreatic duct. Studies have demonstrated
that the intravenous administration of secretin has the effect of allowing the
main pancreatic duct to fill with fluid and therefore become more readily
identifiable [41-44] while another study has claimed success with the use of
intravenous morphine . Time is yet to determine whether these approaches
will be routinely performed in the broad clinical setting.
Variation from the norm: possible modification of protocols
As this overall acquisition takes several seconds to
perform, just about all patients should be compliant to allow this to be
successful. However, depending on patient size, one may need to alter the FOV
accordingly. Also, there may be software teething on some operating platforms
such that all three prescribed slices may not be able to be acquired within the
one series; therefore each prescribed slice may need to be its own series, that
is, only one slice per series.
6. Para Coronal 3D MCRP Respiratory Triggered
This is also a heavily T2-weighted sequence, but acquired
as a 3D volume . The main purpose for this approach is to capture a 3D
perspective of the biliary tree, and with appropriate software, permit the
observer to rotate the volume representation of the biliary tree in order to
view its intricacies from practically limitless angles. This is valuable in providing
detail in relation to the appearance and calibre of the ducts � remember always
that what one has imaged is fluid within the ducts, and thus only providing
information of the internal aspect and condition of the lumen. The axial images
performed earlier can provide higher quality information pertaining to the duct
This volume is positioned to capture the entire biliary
tree. The para-coronal angle used would be identical to that mentioned in the
Coronal Oblique 3D Slab MRCP sequence; that is, the volume is centred to and
along the cystic duct, and the volume expanded to include the entire components
comprising the biliary tree. �This is demonstrated in figure 10. It is
important to include saturation pulses immediately adjacent to all boundaries
of the imaging volume in order to minimise artefacts originating from both
respiratory and physiological motion from degrading the data within the imaging
Once the volume data is acquired, a maximum intensity
projection (MIP) data set is generated [4, 16]. Following this, projections are
defined at fifteen-degree intervals laterally to a complete 360-degree rotation
and also along the superior�inferior axis, once again at fifteen degrees to a
completed 360-degree rotation. Therefore, there should be twenty-four (360
divided by 15 equals 24) projections in the lateral axis rotation and a further
twenty-four projections in the superior�inferior direction. Of course, if there
is a particular area or focus of interest, which would most commonly involve a
junction of two ducts (such as at the union of the cystic duct to the hepatic
duct, or where the pancreatic and CBD unite), then additional projections that
best demonstrate the area of interest are warranted.
It is also prudent to submit the source images to the
radiologist for review and reporting. These source images provide greater
spatial resolution and can best demonstrate small filling defects and
strictures of the pancreatic duct [4, 10, 12, 23]. Depending on their location,
stones as small as two millimetres are capable of being detected and
projections from a variety of angles may also be of use in such instances .
Since spatial resolution can be degraded because of volume
averaging effects, as is well noted with 3D acquisitions, this leads to the
next discussion on axial thin slices.
Variation from the norm: possible modification of protocols
With this sequence, the radiographer must be aware of
possible phase wrap artifacts, so before the sequence begins, the FOV must be
appropriate. In addition, due to the saturation bands encompassing the imaging
volume, they must be carefully positioned for two main reasons: firstly, so
that they can minimise physiological and respiratory motion artifacts from
degrading the image volume and secondly, so that they do not inadvertently
suppress signal within the imaging volume. All the gating and respiratory
parameters discussed in the axial T2-Weighted FRFSE Respiratory Triggered
sequence also apply here.
7. Axial Thin Slices T2-Weighted
The main purpose of this sequence is to acquire biliary
tree duct detail with improved spatial resolution such that small dimension
pathology can be detected  as thick slices tend to obscure small filing
defects . The thinner the slice is, the greater the spatial resolution.
However, SNR is sacrificed for this [34, 38, 40]. Figure 11 provides image
examples of this sequence.
Scanning range once again is from the upper aspect of the
liver to the duodenum. Depending on the patient�s body habitus, this may need
to be performed over a number of breath-hold cycles. An approach such as this
will ensure that there is sufficient overlap of anatomy and the entire biliary
tree is scanned. This is also aided by performing each sequence with expiratory
breath-hold. As discussed earlier, expiratory breath-hold should provide better
consistency for overlapping acquisitions as compared with inspiratory
breath-holding. In the timing screen, there should be an option called �resps.
before pause� which allows the radiographer to determine the number of
respiratory cycles (or breaths) per acquisition. This sequence should have
about thirty-five prescribed slices of four millimetre thickness with a spacing
of one millimetre. This can be performed over nine acquisitions with four respirations
(within each acquisition) before pausing. This should take a total scan time of
approximately two minutes and fifteen seconds; equating to one hundred and
thirty-seven seconds. One hundred and thirty-seven seconds divided by nine
acquisitions equals approximately fifteen seconds. Therefore, each acquisition
takes fifteen seconds and will cover four slices. The fifteen-second value
should also be displayed in the timing screen.
Variation from the norm: possible modification of protocols
The number of respirations before pausing should be
selected according to the patient�s capabilities to perform expiratory
breath-holds. For example, a patient with associated liver pathology (such as
tumour or cirrhosis) or obstructive jaundice or ascites may not be able to hold
their breath for fifteen seconds. Therefore, it would be more prudent to offer
such patients the equivalent of two respiratory cycles before pausing the
sequence; which means that the patient would only need to hold the breath for a
more achievable duration of approximately eight seconds.
8. �Dynamic� Coronal MRCP
One of the main limitations of the MRCP/MRI examination of
the biliary tree and associated organs is that only static images can be
obtained . Whereas, with the diagnostic ERCP procedure, the biliary tree
can be filled with a contrast medium, and its drainage recorded and observed in
real-time with an image intensifier.
This limitation can be somewhat addressed with the dynamic
coronal MRCP sequence. Simply prescribe a slice in the coronal plane directly
through the level of the CBD as prescribed earlier in the Coronal Oblique 3
Slab MRCP sequence. Next, instruct the patient to hold a breath on suspended
expiration and repeat this sequence six times, thereby acquiring six images at
the same location. This is achieved by either clicking on the mouse button to
scan, or by pressing the scan button on the keyboard six times. The resulting
images should demonstrate fluid drainage into the duodenum or obstruction or
strictures along the CBD. Such images are provided in figures 12 (a) to (e) or
alternatively, the video clip (Video 1) generated from these acquired images
can be viewed.
Variation from the norm: possible modification of protocols
As this final sequence takes a combined imaging time of
only a few seconds, there may be very few possibilities for sequence
modification as all patients should be capable of complying with this series. The
radiographer needs to ensure that the FOV is set correctly so that no phase
wrap artifact occurs and that the slice thickness is substantial enough (such
as twenty-five millimetres) so that sufficient contrast resolution becomes
inherent within the resulting image.
The use of MRI and MRCP to assess the biliary tree and
related organs such as the liver and pancreas is now well established. Numerous
publications [2, 20, 25, 45-46] report on the sensitivity, specificity,
positive and negative predictive value of the MRCP/MRI assessment of the
biliary tree, while others report on its diagnostic accuracy [20, 24]. These
studies offer some degree of comparison with the diagnostic component of the
ERCP examination. However, these reported values vary greatly and are more
often reflective of the pathology being assessed, the stage (early onset or
late) at which the pathology is imaged, and the size, dimension or extent of
the pathology. These values are also a function of the capabilities and
features (hardware and software) of the MRI system used, as well as the
expertise of the MRI radiographer.
Although MRCP does not require the administration of
contrast media, the inclusion of MRI examination in conjunction with MRCP may
necessitate the use of contrast media. One recent trend is the implementation
of renal function test prior to the intravenous administration of MRI contrast
media in order to identify patients that may be potentially at risk of
developing nephrogenic systemic fibrosis (NSF). In the MRCP/MRI setting, the
use of contrast media is seen as an alternative to T2-weighted sequences ,
and Gadolinium-based contrast media has proven itself to provide
characterisation between benign and malignant tumours; although dynamic
acquisitions provide greater detection of hepatic lesions than non-enhanced
acquisitions. Kim et al. successfully demonstrated that by adding a T1-weighted,
contrast-enhanced sequence to the MRCP/MRI examination, malignant biliary
strictures were better visualised .
There is no doubt that technology is advancing rapidly to
help generate higher quality images to further enhance the standard of the
MRI/MRCP examination. Emerging trends include the use of automated-type
software programmes [5, 37]. In addition, the administration of secretin (2, 7,
41-44) has been used in the assessment of main pancreatic duct and pancreatic
pathology. Intravenous morphine is also useful in improving distention of the
biliary and pancreatic ducts as it reduces fluid outflow at the ampulla of
Vater, which increases intraluminal pressure . Further studies may be
required to establish their validity as routine practice. High magnetic field
strength at 3.0 T, shows increase in the SNR with improved visualisation of
biliary and pancreatic ducts . However, in some instances, the use of
endoscopic ultrasound is gaining popularity as an alternative to the ERCP 
and MRCP as it provides a higher sensitivity in identifying causes of CBD
obstruction compared with MRCP .
Novel and innovative techniques have also been published. For
example, pineapple juice (which has the effect of decreasing T2 signal
intensity) has been used as a negative oral contrast agent to improve
visualisation of the ampulla of Vater, the CBD and the common hepatic duct 
by minimising signals from the stomach and duodenum detracting from the biliary
and pancreatic ducts. This study purported that pineapple juice may be used as
an alternative to the commercially distributed agent, Ferumoxsil.
What is certain is that the MRCP/MRI examination is firmly
grounded in the clinical setting and has now become an examination that a MRI
radiographer must perform on a very regular basis. It is used in the evaluation
of gall stones, infection and inflammation, and malignant and benign tumours
[4-5, 7, 9, 10-12, 33]. A 2005 study by Shanmugam et al.  has
claimed that the MRCP may become the new gold standard due to its high
sensitivity and specificity for choledocholithiasis, and may even convincingly
replace the diagnostic ERCP in the coming years [7, 10] . Although
transabdominal ultrasound remains the initial imaging modality for the biliary
system , MRCP, spiral computed tomography and endoscopic ultrasound are now
essential components to be carefully considered in the diagnostic work-up 
The advantages offered by MRCP/MRI include: no ionising
radiation; no or relatively low invasiveness  (depending on the
administration of contrast media); no risk of induced pancreatitis  or
other idiopathic treatment complications [2, 16, 24, 52] such as cholangitis
due to contrast media retention in patients with advanced biliary tract
stenosis; no risk of morbidity or mortality (provided that the patient is
correctly screened and is safe to enter the MRI environment and no contrast
material is used); and it is less costly compared to ERCP. If patients are
presented with the option of the two diagnostic tests (MRCP/MRI or diagnostic
ERCP), then patient preference for a more conservative and less invasive
approach may further lead to increased bias towards MRCP/MRI . Over the
last decade, as the role of MRCP/MRI has rapidly strengthened, there has been a
noticeable and corresponding decline in the diagnostic ERCP examination, with
fewer and more complex therapeutic ERCP procedures being the norm. This decline
in ERCP has implications on ERCP training and practice , an issue which is
beyond the scope of this paper. Financial benefits of this have previously been
discussed. The authors believe that the advantages offered by MRCP/MRI
examination will ensure that the MRCP/MRI will be used as a definitive
diagnostic tool for assessing biliary and pancreatic ducts as well as a
screening tool for determining if patients need to undergo surgical
intervention, or if patients can benefit from the therapeutic solutions offered
Thus, radiographers must be aware of the role that the
MRCP/MRI examination can play in the overall medical management of patients
today. As such, it is critical that MRI radiographers must understand and
perform this examination to the highest possible standard.
We would like to thank the Radiology Department at the Alfred Hospital, Melbourne, Australia, for their support of this paper, particularly with
providing access to all the images used in this publication.
- Chart 1 Flow chart, including check-list, for the MRI/MRCP examination. This flow chart is a synopsis of the
sequences for the MRCP/MRI procedure. The chart can also be printed and used as a check-list.
Figure 1 Scanning range prescription for the axial 2D FIESTA Fat Suppressed series.
Figure 10 Volume prescription for the Para-coronal 3D MRCP Respiratory Triggered sequence. Ensure that you will capture the biliary tree, gall bladder and the main pancreatic duct. You may need to scroll through the axial series images to check this before commencing the 3D acquisition.
Figure 11 (a) and (b) are of different patients � They are axial Thin Slice T2-Weighted images demonstrating a filling defect (representing a gall stone) (a) within the gall bladder and (b) calibre irregularity of the main pancreatic duct.
Figure 12 These series of images are of the �Dynamic� Coronal MRCP. Note the movement of the common duct and the fluid drainage into the duodenum that has been captured.
Figure 2 The (a) superior and (b) inferior respective slices of the axial images acquired with 2D FIESTA Fat Suppression.
Figure 3 Scanning range prescription for the Coronal 2D FIESTA Fat Suppressed Sequence.
Figure 4 The (a) posterior and (b) anterior respective slices from the scanning range prescription for the Coronal 2D FIESTA Fat Suppressed sequence.
Figure 5 Coronal 2D FIESTA Fat Suppressed image demonstrating multiple stones within the gall bladder.
Figure 6 An axial T2 weighted FRFSE Respiratory Triggered sequence demonstrating multiple stones within the gall bladder and diagnostic quality image sharpness.
Figure 7 First slice is prescribed coronal, directly through the CBD.
Figure 8 (a) Clearly demonstrates the cystic duct and (b) indicates the second prescribed slice parallel to the cystic duct.
Figure 9 (a) demonstrates a pancreatic head that is pathologic and enlarged. Note that the course of the main pancreatic duct through the head of pancreas is not ideally straight. (b) Indicates how the third slice is prescribed parallel to the main pancreatic duct through the head of pancreas.
Movie 1 This video clip has been created from Figure 12 to demonstrate the 'dynamic� concept of this technique.
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|Received 10 January 2008; received in revised form 20 March 2008; accepted 30 March 2008
Correspondence: Division of Medical Radiations, School of Medical Sciences, RMIT University, Bundoora West campus, PO Box 71, Bundoora 3083, Victoria Australia. Tel.: +61 3 9925 7786; Fax: +61 3 9925 7466; E-mail: firstname.lastname@example.org (Jenny Sim).
Please cite as: Mandarano G, Sim J,
The diagnostic MRCP examination: overcoming technical challenges to ensure clinical success, Biomed Imaging Interv J 2008; 4(4):e28