Knee MRI

Thursday, March 8, 2018

MRI Scan of the Knee

    Carry out all safety checks before bringing the patient into the scanner room. Help patient to lie supine on the scanner table with the affected knee on the dedicated knee coil. The apex of the patella should be about a cm below the center of the coil. Assemble the coil and place the pads between the knee and the coil to help the patient to keep still.

    Provide the patient with an emergency button. Provide ear protection to reduce scanner noise according to your manufacturer guidelines, headphone will also enable communication with the patient during the scan.

    Move the table and center the laser beam localizer over the lower border of the patella. Move the patient into the scanner making sure that the patient is calm and comfortable before leaving the room.

knee mri
Localizer on lower border of patella.

    Once your back in control room select the correct patient details in the browser or you can type the name manually if necessary. It is very important to get the patient details right including the patients weight so that the image can be calculated accurately.

knee mri

   Register the patient as lying feet first and supine. Choose the appropriate knee protocol according to your hospital and radiologist guidelines.


Scanning Sequences

  Begin the scan with an axial localizer sequence. From the axial localizer you can plan the sagittal and coronal localizer parallel and perpendicular to the medial and lateral condyles.

In this protocol the first diagnostic sequence is the proton density or PD fat saturated axial.

PD Fat Saturated Sequences Sagittal

  On the sagittal localizer, angle the positioning box perpendicular to the line through the long axis to femur and tibia, make sure the block covers the area from above the patella and to tibial tuberosity.

Sagittal Localizer

Coronal Localizer

   On the coronal view angle the slices parallel to tibial plateau. Using the saturation bands above and below the axial block will further reduce arterial pulsation artifacts.

Coronal Localizer

Axial Localizer

    Center the axial localizer in the field of view, the face direction in the axial scan should be right to left. This is to avoid pulsation artifacts from popliteal artery.

Axial Localizer

PD Fat Saturated Sequence Routine 

   After scanning the localizer plan your PD fat saturated coronal sequence on the newly acquired axial image.
Slices should cover the knee joint from patella anteriorly to popliteal artery posteriorly.

Slices should run parallel to the posterior border of the femoral condyles.

Sagital view the slices should plan parallel to the midline of femur and tibia. Use saturation band above and below to reduce pulsation artifacts.

Check your planning and apply.

PD Fat Saturated Planning

Sagital View sequence.
STIR Sequence
STIR is design to supress the signal from fat.

STIR Planes Planning

Axial plane – plan the slices parallel to the lateral condyle of the femur, in most cases this could be also parallel to the ACL or anterior cruciate ligaments. Make sure the planning box is covered form the lateral and medial condyle.

Coronal View – align the slices parallel to the midline to the femur and tibia.

Sagital localizer – center the sagittal localizer in the field of view and apply.


Note: for the subsequent sagittal sequences the slice number and planning can be just copied from the previous sagittal sequence like the protocol of T1 and T2 stir sagittal sequences.

After scanning the image you can start the reviewing images.

PD Fat Saturated Axial image – fluid appears bright and fats appears dark. Most infection and edema in the knee appears bright in this sequence. This sequence are very useful for visualizing cartilage, ligament and bony edema.

PD Fat Sat Axial Image

PD Fat Saturated Coronal Image – you can see clearly menisci cartilages as well as the anterior cruciate ligaments and the posterior cruciate ligaments. In this view allows the best visualization of meniscus tears.

PD Fat Sat showing Meniscus coronal (arrow)

PD Fat Sat Cor. showing ACL (arrow)

PD Fat Sat showing PCL (arrow)

T2 STIR Sagittal Sequences Images

All sagittal sequences allow the visualization of menisci, the ACL and the PCL along with tears and insufficiencies.

T2 sagittal  (Menisci arrow)

T2 sagittal ( ACL arrow)

T2 Sagittal PCL (arrow)

STIR Sagittal Images
Fluids appear bright and fats appears dark. This are useful for highlighting infection and bony edema.

T1 Sagittal Images

Fluid appears dark fats appear bright. This are useful in diagnosis in cystic and blood components which if present blood could appear bright on a T1 scan.

T1 Sagittal image

T2 STIR Sagittal

In this sequence fluids appears bright and muscle appears gray. T2 STIR are very useful for visualizing the menisci and for assessing the ACL and the PCL.

T2 STIR sequence

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