Positioning Calibration Objects
Pelvis Calibration Object Positioning
Position patient to include upper third of femoral shaft in the image.
Follow the following two steps for proper marker positioning on the pelvis image:
Step 1: Position the calibration object at the level of the greater trochanter on the lateral side of the pelvis, equivalent to the level of the hip joint. Unless the patient has narrow hips, the marker will be projected beyond the margin of the image in this position, necessitating Step 2 for most patients.
Step 2: Move the calibration object carefully to the same vertical level (height) between the patient’s thighs, where it will be visible in the radiation field.
Hip Calibration Object Positioning
Anterior Posterior (AP) View: Use the same positioning of the calibration object as for the as pelvis, at the vertical level (height) of the greater trochanter on the lateral side of the hip. Ensure the calibration object is included in the x-ray field.
Lateral Oblique View: Designed to view the femoral stem width rather than the hip cup, which can be measured in the AP, place the calibration object laterally mid-thigh to best establish the level of the femoral shaft. For very large patients, take into account any adipose tissue.
Lateral Inferior-Superior (Femoral Neck) View: Position the calibration object anteriorly mid-thigh to establish femoral canal width only near the position of object.
Knee Calibration Object Positioning
Position patient so an equal amount of femoral and tibial shaft are visible on the image.
AP View: Place the calibration object over the lateral side of the knee in the joint line, roughly midway between anterior and posterior surfaces. If a patient has large muscled, this needs to be taken into account.
Lateral View – Medial to Lateral (ML): Place the calibration object on the anterior side of the knee, either superior or inferior to the patella in the midline.
Lateral View – Lateral to Medial (LM): See Long Bones / Femur.
Calibration Object Positioning for Long Bones such as Femur
AP View: Place the calibration object midway between the anterior and posterior surfaces, over the shaft on the lateral side of the bone.
Lateral View – ML: Place the calibration object on the anterior part of the limb in the mid-line.
Lateral View – LM: Place on the anterior mid-line of the limb around the area of interest, if known.
As the surgeon will need to know how the lateral was taken – annotate with horizontal beam or LM if possible.
Shoulder Calibration Object Positioning
Humerus Calibration Object Positioning
Spine Calibration Object Positioning
AP View: Place the calibration object on the lateral side of the neck over the midpoint between the anterior and posterior aspects of the neck.
Lateral View: Place the calibration object over the cervical spinous processes on the posterior aspect of the neck.
Thoracic and Lumbar Spine
Lateral View: Place the calibration object over the spinous processes at the appropriate spinal level.
Note: An AP coned view does not allow calibration object placement; however, for full length spine scoliosis images, a calibration object can be placed on the lateral abdomen at spinal level of interest.
Notes about Positioning Calibration Objects
- Individual surgeons may require alternative positioning according to their particular requirements.
- The devices shown can be replaced with alternative objects of known size.
- All objects used in a patient contact environment will need to be cleaned according to the local health and safety hygiene requirements with a suitable nonabrasive cleaning solution applied after each use.