Video guides to veterinary CT scanning - head and neck

Computed Tomography (CT) is a useful diagnostic imaging modality that can provide you with more detailed information than conventional x-rays. Knowing when to do a CT scan (i.e. which types of cases and when in the case work-up) is crucial information. It helps vets get the most out of this modality for both the patient and the owner. However, there are also some considerations and limitations to think about. 

Watch our short video guides which walk you through the key considerations for:

• Head and neck CT scans
• Musculoskeletal CT scans
• Spine CT scans
• Thoracic CT scans
• Abdominal CT scans

The videos cover:

• what to consider before you choose to do a CT scan
• CT vs x-ray for each body area
• the limitations of CT scans. 

Veterinary CT scanning - questions to ask yourself

You can ask yourself these questions when deciding whether to choose to recommend a CT scan for your patient, or not:

Advantages and disadvantages of CT scanning

Irrespective of the anatomical region imaged, it's important to consider the advantages and disadvantages of CT in general. There are a good number of advantages including:

• excellent spatial and contrast resolution
• the ability to generate a 3D representation of 3D anatomy
• ability to get a good overview of a large body area in detail
• ability to give contrast to get information about vasculature and perfusion.

But there are also some disadvantages, for example:

• it requires heavy sedation or general anaesthesia
• it can be expensive
• there are occupational safety considerations, such as ionising radiation
• it may necessitate travel to a different location with a CT machine.
• additional expertise in reporting the images is often required.

Watch our short video guides which walk you through the key considerations for:

• Head and neck CT scans
• Musculoskeletal CT scans
• Spine CT scans
• Thoracic CT scans
• Abdominal CT scans

CT for the head and neck is almost always indicated if there is a suspicion of structural lesions that could explain a patient's clinical signs. It may be that you detect structural changes from your physical exam. 

The caveat to that is, if clinical signs are primarily related to the central nervous system or cranial nerves, then MRI is preferable as the modality of choice. 

However, this may not be the case in head trauma cases, where thorough assessment of the skull and the surrounding soft tissues, in addition to neurological tissue, is necessary.

Other indications for head CT include:

• asymmetry of the head, both palpable and visible 
• head trauma
• pain when opening mouth 
• recurrent or severe otitis
• dyspnoea related to the upper airways, which may include stertor or stridor 
• oral, facial or cervical masses
• neck swelling 
• surgical planning for previously identified lesions.

Watch our short video guides which walk you through the key considerations for:

Understanding the CT Imaging Process

Performing a CT scan involves three main steps: acquisition, processing, and viewing. Each of these stages is distinct and critical for producing accurate diagnostic results:

1. Acquisition: This step occurs in the CT room and involves positioning the patient and setting parameters such as KV, mAs, and table speed. It is important to optimise these settings because errors at this stage cannot be corrected later. It is also important to ensure pre- and post-contrast series are obtained where needed. During acquisition, raw data is collected as a vast set of binary data that needs further processing to be translated into interpretable images.

2. Processing: This step transforms the raw data into images using the CT scanner's built-in computer. This can be done after the patient has left, provided the raw data is available on the machine. Processing parameters include slice thickness, filters, and display field of view (DFOV). Common errors in processing can be corrected as long as the raw data is intact.

3. Viewing: This involves manipulating the processed images on a workstation using various windowing techniques to highlight different anatomical features. Windowing adjusts the image contrast and brightness to make different tissues more visible.

Watch our short video guides which walk you through the key considerations for: