Information for imaging professionals on the importance of scaling with a step by step guide to marker placement.
‘Scaling x-rays for digital templating is like turning on the full beam in that it adds clarity and confidence to the measurements used for planning.’
Dr Grant Shaw is an experienced orthopaedic surgeon and authority on PACS and its implications for orthopaedic practice. Click here to see Dr Shaw’s full article on scaling and marker placement for digital x-rays of the hip .
To download a fact sheet on magnification and scaling of digital images with OrthoView click here.
Marker Placement Presentation and Radiographic Technique
For a pdf version of the Presentation (6Mb) including images below, click here.
Guide to the Positioning of Calibration Markers.
Select from the list of commonly examined body areas below and click on the images to expand them.
Position patient to include uppper 1/3 of femoral shaft on the pelvis image.
There are 2 stages for marker positioning on the pelvis image:
Step 1: Position at the level of the greater trochanter on the lateral side of the pelvis, equivalent to the hip joint level. Unless the patient is narrow at the hip the marker will be projected beyond the margin of the image, therefore…
Step 2: Move the marker carefully to the same vertical height level between the thighs where it will be visible in the radiation field.
AP Hip, same positioning as pelvis, at the vertical level/height of the greater trochanter on the lateral side of the hip. Include in the radiation field.
Lateral Oblique Hip, designed to view the femoral stem width rather than the hip cup which can be measured in the AP. The marker is placed laterally mid-thigh to best establish the level of the femoral shaft. For very large patients any adipose tissue will need to be taken into account.
Lateral Inferior-Superior, NOF# view. Marker is positioned anteriorly mid-thigh to establish femoral canal width only near position of marker.
Position patient so an equal amount of femoral and tibial shaft are visible on the image.
AP View, marker is placed over the lateral side of the knee in the joint line, roughly midway between anterior and posterior surfaces, however if a patient is well muscled this needs to be considered.
Lateral (ML) View, marker is placed on the anterior side of the knee, either superior or inferior to patella in the midline.
Lateral (LM) View, see Femur.
Long bones, femur etc.
AP View, place the marker midway between anterior and posterior surfaces over the shaft on the lateral side of the bone.
ML – place the marker on the anterior part of the limb in the mid-line.
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.
Humerus AP and Lat
Cervical Spine, AP and Lateral:
AP View, place marker on the lateral side of the neck over the midpoint between the anterior and posterior aspects of the neck.
Lateral View, place the marker over the cervical spinous processes on the posterior aspect of the neck.
Thoracic and Lumbar Spine:
Lateral View, place marker over the spinous processes at the appropriate spinal level.
Note: an AP coned view does not allow marker placement, however for full length spine scoliosis images a marker can be placed on the lateral abdomen at spinal level of interest or some centres will prefer to use a ruler device.
- 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.