Ankle_imaging by heku


									               CLINICAL VALUE

     Tips From the Technologist:
     Easy Steps for Ankle Imaging
                                By Tony Issa, Chief MRI Radiographer,
                                Norwest Medical Imaging

                                At our facility, we perform a large number of musculoskeletal
                                MRI exams on elite athletes. One of the more difficult joints
                                to scan effectively is the ankle, which is due to its many
                                ligaments and tendons, not to mention the different angles
                                needed to image around the ankle.
                                To ensure that we obtain consistent results of ankle MR
                                studies, we use the technique described below and have
                                found it gives us extremely reproducible results, as well
                                as good demonstration of the anatomy.

                                Step 1:
                                The ankle is scanned using the transmit receive ankle
                                coil, which makes the positioning easy, reproducible,
                                and comfortable for the patient.

                                Step 2: Axial PD and PD fat sat
                                Next we use the 3-plane localizer and from there, we can
                                plan the axial (or long-axis) views.
                                Axial PD/PD fat sat: No angulation of the block is used if the
                                ankle/foot is straight, otherwise we angle along the plantar
                                of the foot. The angle is determined by the degree of
                                the plane of the foot.
                                Both PD and PD fat sat are scanned in this plane making
                                it easy to copy the prescription forward.

                                Figure 1. Note slice angles for axial   Figure 2. Resulting PD axial
38   SignaPULSE • Autumn 2009   (short axis) PD and PD Fat Sat.
                                                                    MSK IMAGING              CLINICAL VALUE

Step 3 : Sagittal PD and PD fat sat
Proper angulation of the ankle perpendicular to the talar dome and the malleoli is
necessary. Once the angle is determined, another angulation along the calcaneous
and tarsal bones is required, to reduce distortion of the ankle/foot in the sagittal                                Tony Issa
plane. Achieving these two angles to the best of your ability will reduce this
distortion and place the ankle and foot in the correct plane. A good reference
to determine whether the angles are correct is to review structures such as the
sinus tarsi. Again, we use Copy Rx when scanning a PD and PD fat sat so we can
plan once and copy the prescription forward.
                                                                                        Tony Issa, chief MRI radiographer at Norwest
                                                                                        Medical Imaging, studied at the University of
                                                                                        Sydney, where he completed a degree in Applied
                                                                                        Science Diagnostic Radiography. Issa joined
                                                                                        Norwest Medical Imaging 18 months ago and
                                                                                        was responsible for starting their very busy MRI
                                                                                        department. Issa specializes in MSK imaging,
                                                                                        always striving for the very best image quality.

Figure3. Coronal ankle (note the   Figure 4. Resulting sagittal
slice positions)                   ankle plane

Step 4 : High-resolution talar dome
Using a properly acquired sagittal and axial image, a block of fine slices is placed
over the talar dome area. A reverse angle running perpendicular to the dome on          About the facility
the sagittal image and parallel along the axial image of the dome is applied. This
                                                                                        Norwest Medical Imaging is an independently
angle can vary between 7 and 10 degrees depending on the patient’s anatomy              owned, state-of-the-art radiology practice that
and position.                                                                           has been in operation for two years. Located
                                                                                        in the Hills area of Sydney, Australia, it boasts
                                                                                        first-class premises, equipment, and staff.
                                                                                        Continuing their commitment to state-of-the-art
                                                                                        imaging services, Norwest Medical Imaging is
                                                                                        proud to announce the installation of a new
                                                                                        1.5T GE Signa MRI scanner at their facility.

Figure 5. Note the angle of the    Figure 6. Resultant coronal PD
slices through the talar dome.     small FOV

By utilizing this technique, we can generate an excellent image of the talar dome
that will help us examine the medial and lateral aspects of this anatomy. Pathology
such as talar dome lesions and chondral wear in the joint area are common and
clearly depicted with this sequence. Furthermore, orthopedic specialists use these
images to examine the medial corner of the dome, where arthroscopy often fails
to clearly show pathology, making this MRI sequence extremely useful.
By following this technique, we are able to produce consistent, high quality images
of the ankle for our radiologists. „

                                                                                       A GE Healthcare MR publication • Autumn 2009         39

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