The quality of the CT dataset directly influences the accuracy of surgical planning and the design of patient-specific implants or guides. Adhering to the recommendations below will help ensure that the images obtained are suitable for detailed assessment and planning.
Acquiring CT for a
patient-specific guide.
1 General Requirements
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These apply to every submission, whatever the region. When a case sits outside them, the area-specific notes below take precedence.
1.1 Slice thickness
Images should be acquired using the thinnest slice thickness available whenever possible. In some circumstances, such as imaging the cervical spine or lumbosacral region in larger dogs, a slightly greater slice thickness may be required to maintain image quality and minimise excessive image noise.
1.2 Field of view
The field of view should be restricted to the smallest area that adequately encompasses the region of interest. When a larger scan is necessary, for example to assess overall limb alignment, consideration should be given to obtaining an additional focused scan of the specific anatomical area requiring treatment.
1.3 Patient positioning
The patient should be positioned so that the primary bone or anatomical structure under investigation is aligned as close as possible to perpendicular to the CT gantry. Although perfect alignment is not always achievable, careful positioning improves image consistency and assists with accurate surgical planning.
1.4 Image submission
The complete DICOM dataset should be provided and reconstructed using a bone algorithm. For oncological cases, additional soft tissue reconstructions may also be required to support comprehensive case assessment.
2 Region-specific recommendations
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Find the case type you are submitting. Positioning and coverage are tailored to what the guide design needs from each region.
Vertebral Procedures
For spinal stabilisation procedures, the CT study should include at least one complete vertebra cranial and one complete vertebra caudal to the planned surgical site. This ensures sufficient anatomical information is available for implant planning and surgical assessment.
Humeral Intracondylar Fissure
When assessing humeral intracondylar fissures, imaging of both elbows is preferred. The scan should include the elbow joints together with the distal half of the humerus. Patients should be positioned in sternal recumbency with the forelimb gently extended forwards. The humerus should be aligned as close as possible to perpendicular to the gantry to optimise image quality.
Medial Patellar Luxation and Distal Femoral Osteotomy Planning
For medial patellar luxation and distal femoral osteotomy planning, separate scans of both hindlimbs are recommended. Where practical, imaging should extend from the pelvis to the digits to allow assessment of both femoral and tibial alignment. The patient may be positioned in either sternal or dorsal recumbency with the hindlimbs gently extended caudally. The femur should be positioned as close as possible to perpendicular to the gantry.
Antebrachial Deformities
For antebrachial deformities, the scan should include the entire affected forelimb, extending from the digits to the shoulder. Patients should be positioned in sternal recumbency, with the limb gently extended forwards using light traction. The elbow and carpal joints should be maintained at angles that closely resemble the patient's normal standing posture. If the opposite forelimb is unaffected, a separate scan of the contralateral limb should also be obtained for comparison. Assessment and documentation of carpal laxity while the patient is sedated can provide valuable additional information.
Other Limb Deformities and Malunions
In cases involving other limb deformities or malunions, both the affected limb and the contralateral limb should be scanned separately and in their entirety. Patients may be positioned in either sternal or dorsal recumbency. Gentle traction should be applied to extend the forelimbs cranially and the hindlimbs caudally. For deformities affecting the antebrachium or crus, evaluation of carpal or tarsal laxity during sedation can further assist in treatment planning.
Fracture Cases
In fracture cases, the entire length of the affected bone should be scanned. A corresponding scan of the equivalent bone on the opposite limb should also be obtained to facilitate comparison and planning. Patients may be positioned in either sternal or dorsal recumbency, with the forelimbs gently extended forwards and the hindlimbs gently extended backwards.
Not sure about your protocol?
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If you have any doubt about CT acquisition for a specific case, please get in touch before scanning. Small adjustments to the protocol can save a repeat study and significantly improve guide accuracy — we are always happy to advise.