What is diagnostic imaging?
Diagnostic imaging refers to multiple techniques that are used to create images of particular parts of the pet's body to aid
the process of diagnosing and evaluating the extent of the underlying disease.

What are the different types of imaging techniques used to diagnose cancer in cats and dogs?
Both traditional and special contrast X-ray techniques are used to look for tumors in the pet's lungs, gastrointestinal tract,
bladder and other internal organs. X-rays are usually used as the first imaging test to evaluate the pet's condition and
determine whether the cancer has spread throughout the body.  

Computed Tomography (CT)
CT is a very specialized imaging technique available at referral centers or specialty hospitals. Like X-rays, CT relies on the
differences in density between tissues to form an image, but the images of cross-sections of the body are generated by a
computer. It is a superior technique compared to X-rays in evaluating cancer in the lung, the chest cavity and ribs, and is
important for planning
radiation therapy. CT scan can also be used to guide biopsy instruments to collect samples from the
suspected mass for further analysis.

Contrast-enhanced CT imaging provides great detail about the extent of cancer spread, and has been very useful in
soft tissue sarcomas such as feline vaccine-associated sarcoma. The pets will have to be anesthetized for the
procedure since any movement by the pet will make the images unreadable. But the advantages of the superior clarity and
resolution of CT scans can help identify cancer at earlier stages, thus increasing the likelihood of better outlook.

Ultrasound refers to a technique used to examine internal organs in the abdomen and to guide a biopsy. The veterinarian
places a transducer emitting very high frequency sound waves in contact with the area of interest (e.g. stomach), moves it
around and views the structure of internal organs on a monitor in real time. It is routinely used to evaluate masses
discovered during physical examination or to check for metastasis (cancer spread) to liver, spleen or other organs. It
cannot generally be used to evaluate structures that contain air such as the lungs since air prevents the transfer of sound
waves. The limitation of ultrasound is that it cannot distinguish between a benign and a malignant mass, therefore a
is necessary to confirm the nature of a detected mass.  

Magnetic Resonance Imaging (MRI)
MRI is a technique that combines strong magnetic field interacting with hydrogen protons in the body, resulting in superior
three-dimensional images created by a computer. Like CT, MRI displays slices of the examined area, but unlike CT, MRI
produces images in real time rather than following later image reconstruction. MRI is extensively used to evaluate masses
in the central nervous system such as the spine or brain and has been useful in providing images of soft tissues, joints,
tendons, muscles and bone marrow. Dynamic contrast-enhanced MRI has been useful in examining changes within the
tissue such as blood flow. In order to perform the procedure, anesthesia will be required to avoid pet's movements.


Nuclear Medicine
Nuclear medicine refers to an imaging technique in which the pet is administered radioactive compounds to an area of
interest, followed by measuring the emitted radiation. It does not provide great anatomical detail like CT or MRI but
provides useful information about the
physiological processes. This technique has been useful in evaluating the entire
skeleton, kidneys, thyroid, spleen, lungs and liver for the presence of cancer and/or to determine whether the cancer has
spread throughout the body. The pet will usually not have to undergo anesthesia but may be required to stay overnight
until most of the radioactivity caused by the scan has been eliminated from its body.

SPECT and PET refer to advanced nuclear medicine imaging techniques which are widely used in human medicine. The
combination of SPECT and PET imaging allow simultaneous acquisition of both anatomical and physiological information,
providing very accurate information. Radioactively labeled glucose (type of sugar) has been used for whole body scans to
detect distant metastases since many tumors use up glucose at increased level compared to normal cells
Imaging To Diagnose Cancer in Cats and Dogs
Contrast radiography showing a mass in a dog's bladder
Contrast radiography showing a mass in a dog's spleen
Source: www.thepetcenter.com/gen/can_spleen.jpg
CT scan of a dog
Source: www.kbvetcenter.com/images/ct_scan.jpg
CT scan showing tumor in a dog's nose
Source: www.cvm.tamu.edu/oncology/faq/faq/07-13.jpg
Bladder cancer in a dog detected by ultrasound.
Source: www.ashleighvetclinic.com/images/cancerbl.jpg
Bladder cancer in a dog detected by ultrasound.
Source: www.petvets.com/img/newsletter/bladder-tumor.jpg
Brain tumor in a dog detected by MRI.
Source: www.vetmed.wsu.edu/depts-vth/images/thumbs/mritumor_small.jpg
Thyroid cancer in a cat detected by nuclear medicine scan.
Nuclear medicine gamma camera
PET and SPECT scans of a dog's brain
Source: www.snidd.org/imagemonth_files/image005.gif
© 2007 Pet Cancer Center. ALL RIGHTS RESERVED.
Last updated 2/19/2017
Comprehensive guide to cancer diagnosis and treatment in cats and dogs