Rev. 10-4-06
ACRIN-PA 4001
Protocol for positioning subjects and obtaining MR Images
Procedure for positioning subjects for MRI examinations
Purpose: Previous studies indicate variation in patient positioning are a substantial source
of random error in MRI measurements of articular cartilage. It is important to
take steps to reproducibly position the subject in the scanner for each study.
INITIAL MRI EXAM
1. The target knee is selected. For normal subjects this is based on the flip of a coin
(heads) right knee, (tails) left knee. For symptomatic subjects the target knee is
selected based on the radiographic assessment of KL grade used during
enrollment.
2. The subject is positioned supine feet first on the MRI table. The inferior pole of
the patella should be placed at isocenter of the radiofrequency (RF) coil.
3. The heel of the target leg is placed in the ACRIN positioning device
4. The foam pad is placed behind the knee. The thickness of the pad should be
adjusted to put the knee in approximately 5 degrees of flexion. If there are
different pads used for this study then identify and record this pad on the subject
encounter form for subsequent visits.
5. The positioning device is adjusted to achieve subject comfort, and the Velcro
strap is secured around the foot and ankles.
6. Measure the distance between the edge of the coil and the edge of the footplate on
the positioning device using a MRI compatible tape measure. This distance
should be recorded on the subject encounter form for subsequent visits.
7. Position the subject in the magnet isocenter using the scanner laser positioning
system
MRI EXAMINATIONS 2, 3, AND 4
1.
2.
3.
4.
5.
Identify the target knee and confirm with subject record
Position the target knee in the coil with the inferior patellar pole at isocenter.
Place the pad used in MRI visit 1 behind the knee
Place the heel of the target leg in the ACRIN positioning device
Adjust patient positioning to ensure the distance between the coil and positioning
device matches that used in MRI visit 1.
6. Secure foot and ankle with Velcro straps
7. Position the subject in the magnet isocenter using the scanner laser positioning
system
Rev. 10-4-06
Procedure for planning coverage for MRI study
TRIPLANE AND SAGITAL SCOUT IMAGES (FIGURE 1)
The triplane scout should be centered at isocenter and provides 3 sections in the three
standard orthogonal projections. The triplane scout is used to position the sagital scout
that will be used in planning subsequent imaging planes.
1. Select axial image that includes the posterior margin of both femoral condyles
2. Draw line that passes through the posterior margin of the femoral condyle
termed the posterior intercondylar line (PIL) (See Figure 1)
3. Position sagital scout perpendicular to the PIL
PIL
Figure 1: Axial scout image used to determine position of the posterior intercondylar
line (PIL). The sagital scout images are positioned perpendicular to the PIL
PLANNING CORONAL IMAGES (FIGURE 2)
Coronal images obtained in this protocol consist of
 3D WE-GRE
 MSME (T2 Mapping)
 T1rho weighted SSFP
These sequences should provide the same anatomic coverage of the femoral tibial joint as
outlined below:
1. Using the axial image from the tri-plane scout align the coronal plane parallel
to the PIL
2. Select the sagital scout image that passes through the center of the medial
femoral/tibial joint space
3. Adjust position of the coronal images to ensure coverage from the anterior to
posterior edge of the tibial plateau
Rev. 10-4-06
PIL
Figure 2: Coronal images should be oriented parallel to the PIL. Using the sagital
scout image obtained in the center of the medial femoral tibial coverage ensure
coronal images extend from the anterior to posterior margin of the tibial plateau
PLANNING AXIAL IMAGES (FIGURE 3)
Axial images obtained in this protocol consist of
 3D WE-GRE
 MSME (T2 Mapping)
 T1rho weighted SSFP
These sequences should provide the same anatomic coverage of the patellofemoral joint
as outlined below:
1. Select the scout image that passes through the center of the patella
2. Coverage on axial images should extend from the superior to inferior pole of
the patella
3. Ensure phase encoding is in the left/right direction to prevent pulsation artifact
from overlying the patellar cartilage.
Figure 3: Coverage
for axial images.
Coverage should
extend from the
superior to inferior
margin of the patella