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 . 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 environment.
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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 salso 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.
READ MORE:
Dynamic Coronal MRCP
Secretin-Enhanced MRCP Protocol
3D MRCP Pancreas Technique
READ MORE:
Dynamic Coronal MRCP
Secretin-Enhanced MRCP Protocol
3D MRCP Pancreas Technique
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