Video Guides to Veterinary CT Scanning - The Abdomen

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:

• is CT appropriate for the anatomy that I want to image? 
• will it answer the clinical question that I have in mind, considering the presentation of the patient?
• is it cost effective for the client, or would an alternative modality provide the answer at a lower cost? 
• are there any contraindications that I need to consider before using it? This may be that the patient is not stable enough for chemical restraint (sedation or anaesthesia)
• am I happy with my decision on which body parts to scan?
• what type of acquisitions do I need to perform? 

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

Veterinary CT for the abdomen

When could you choose CT for the abdomen? 

CT and ultrasound are two imaging modalities that are both indicated and incredibly helpful in assessing a patient’s abdomen. Acquiring ultrasound images that are of diagnostic quality is operator-dependent; you need to have someone available, or yourself be able to do a good abdominal ultrasound. Additionally, abdominal ultrasound may be limited by the patient’s size, their shape or body condition, and you may only realise this once you've started to perform the ultrasound.

CT of the abdomen should provide a detailed tomographic (cross sectional) anatomical assessment of the abdominal organs, but bear in mind it still has some limitations. As a general rule of thumb, CT is often selected over ultrasound as the imaging modality for the abdomen in patients that are over 25kg.

The indications for abdominal CT are:

• if you have pathology that's not fully characterised on radiographs or ultrasound, or your findings from those modalities are equivocal or non-specific assessing gross structural abdominal disease or characterising abdominal masses, and these may have been found from previous imaging or may be palpable. 
• if you've already identified neoplasia in a location, then it may be good for staging that neoplasia, looking at the liver and spleen for any secondaries, or looking for any lymphadenopathy that might accompany that neoplasia 
• abdominal pain or abdominal distension
• trauma
• investigating vascular anomalies based on the physical exam and biochemistry, such as portosystemic shunts
• investigating disseminated, multifocal or systemic disease
• a lesion that has been pre-identified for which you need to do surgical planning, for example, if there's an adrenal mass identified by ultrasound, then CT would be appropriate for surgical planning for an adrenalectomy.

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

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:

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