Many advances in the management and success of cancer treatment have been due to improvements in imaging technologies.
A variety of diagnostic imaging techniques such as x-ray, CT, ultrasound and fluoroscopy are available at AURA. This variety of diagnostic imaging technology, along with the skills of the imaging personnel, allow us to achieve a number of important goals for our patients. This may include the refinement of a diagnosis that is suspected based on the history, physical examination or blood tests. We also use imaging to obtain samples directly from a mass or affected organ without the need for surgery. Our advanced diagnostic imaging systems are also used to help detect the presence of occult disease (for example, secondary cancers), or to better visualise the relationship between a mass and normal anatomical structures. This information can allow us to more confidently plan a surgical procedure. In certain cases, we use our imaging equipment to perform focussed treatments against an affected organ (see Interventional Radiology).
Our variety of diagnostic imaging technology, along with the skills of our imaging personnel, allow us to achieve a number of important goals for our patients.
Diagnostic imaging at AURA
Advancements in ultrasound and CT imaging have reduced the usefulness of the traditional x-rays for many of the complex disorders that are treated at AURA. However, our digital x-ray system is still used to provide a screening tool for many disease conditions; to confirm the accurate positioning of patient care devices such as feeding tubes, drains etc; or to provide cost-effective monitoring of disease progression.
Computed Tomography scans (CT scan)
Our Toshiba Aquilion 160-slice CT scanner allows us to obtain quality images of the entire patient. The CT scan provides exquisite detail of most internal organs and the skeleton, and allows internal structures to be viewed in their anatomical position, without superimposition. For improved visualisation of disease and organ anatomy, and to help highlight the blood supply of an organ, a contrast agent will be injected into the blood. This sequence of non-contrast and contrast-enhanced images allows us to more readily identify areas of disease, inflammation, infection, and also to pinpoint foreign bodies.
Many cancers are capable of spreading beyond their original location, a process known as metastasis. The CT scan allows us to obtain high-resolution images of the chest, abdomen or skeleton, which are common sites for secondary cancers to develop.
The presence of a metastasis does not necessarily mean that treatment of a cancer is impossible, nor that the prognosis for the patient is now hopeless. However, if metastasis is detected on the CT scan, this may change the conversation about the expectations of treatment. It may also suggest that a different treatment solution could be effective or that better control of the tumour may be achieved with a combination of treatments.
Lymphangiograms and detection of the sentinel node
Some cancers may spread to a local lymph node early in the disease course. This spread may be microscopic, so there may be no outward change in the size or texture of these nodes on physical examination. Detection of this microscopic disease, and elimination of this early spread by removing these positive nodes, may greatly improve the outcome of some patients.
To help identify the first node where a cancer may spread to, we can perform a special dye study, called a lymphangiogram. For this study, we inject a contrast agent around the circumference of the tumour. A series of images is then obtained with the CT to identify which lymph node is first highlighted by this contrast agent. This node is considered the sentinel node, and is recognised as the first site where cancer cells migrating from the primary cancer will arrive. The surgeon can then remove this node at the time of surgery, and send it to the lab for analysis to help determine if there is any spread of cancer. Sentinel node management is increasingly recognised as an important aspect of tumour staging.
The high-resolution of our CT provides excellent detail of all internal organs, as well as the musculoskeletal system. Individual muscles and blood vessels can be identified, as they contrast readily against fat and connective tissues. Contrast media is used to further enhance the distinction between diseased organs or tissues, or to improve visualisation of the tumour or disease process against surrounding tissues.
The level of detail provided by the CT scan allows the clinician to determine the precise anatomical location of the disease. For patients with suspected foreign bodies, the CT has proven a game-changer in helping to identify pockets of disease that would otherwise be impossible to find, or to highlight the location of a penetrating foreign object. For the cancer patient, the images provided by the CT allows the surgeon to determine if the tumour remains confined to well-delineated anatomical barriers, or whether it has potentially spread more widely into adjacent tissues. Using this information, the surgeon is able to plan a surgery with more confidence.
An ultrasound uses high-frequency sound waves to enable imaging of internal organs. The ultrasound is particularly useful for imaging of the organs and tissues within the abdomen, neck and musculoskeletal system. Ultrasound can provide a very different perspective on the state of internal organs compared to x-ray and CT, so often these modalities may be used together to provide a more complete understanding of the disease process. Images obtained using ultrasound are seen in real-time, which allows ultrasound-guidance to be used to assist with collection of samples directly from the organ or site of interest. This sampling can often allow us to obtain a diagnosis without the need for an invasive surgical procedure. In some cases, we can also retrieve foreign bodies deep in the body and avoid the need for an open surgery.
Contrast enhanced ultrasound (CEUS)
Ultrasound can also be used to help detect the sentinel node for certain cancers. Our Philips EPIC Elite ultrasound machine allows us to detect the flow of a special contrast agent that contains minute bubbles of air. After injection of this fluid around the tumour, ultrasound is used to detect this contrast agent as it flows through the tissue towards a lymph node. The specific node or nodes that receive this contrast agent first is then identified as the sentinel node. The surgeon can then remove this node and send to the lab for analysis to help determine if the cancer has managed to spread to this node. This information can help guide the individual treatment plan for a patient based on the extent of their disease.
Barium swallow study showing delayed transit of food into the stomach, and mild reflux.
Fluoroscopy allows a continuous x-ray image of the body to be displayed in real-time. At AURA, fluoroscopy is used for a variety of specific tasks, including evaluation of normal swallowing function and the transit of food from the mouth down to the stomach. This study – called a Barium swallow – is invaluable when investigating possible causes of regurgitation or persistent nausea in our patients. Fluoroscopy is also an essential imaging tool when performing many of our interventional procedures. Manipulation of stents or intravascular devices can be visualised directly on the viewing screen. Contrast material can be used to highlight the blood vessels to ensure that targeted treatments are accurately positioned.
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It is increasingly recognised the mast cell tumours will spread by drainage to one of the regional lymph nodes. Detection of this node can therefore be an important aspect of clinical investigation to improve outcome for patients with malignant forms of this cancer.
Knowing which lymph node is draining the tumour site is not easy to predict from examination or simple anatomical considerations. Using diagnostic imaging to identify the sentinel node is therefore recommended prior to surgery to allow accurate recognition of the correct node. This node can then be sampled and the status of the cancer better defined.
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The imaging team at AURA is comprised of veterinarians with specialist training in diagnostic imaging and qualified radiographers. Our radiologists perform all ultrasound procedures and provide additional interpretation of CT or radiographs when required. Our radiographers have all trained and worked in human hospitals and help maintain a high-standard of image acquisition for all patients coming to AURA.