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CT Scan

A CT scan (computed tomography scan) is like an x-ray that produces a set of detailed cross-sectional images of the inside of the body. The machine surrounds the body so that it can rotate around the body taking several pictures. These pictures are then put together to make a three-dimensional image of a slice of the body.

A CT scan of a bone with osteosarcoma will show if the tumor has grown into nearby soft tissues, such as muscle, fat or cartilage. Once the doctor has the CT scan images, they can easily determine the area of the bone to biopsy.

A CT scan of the chest is done to determine whether the osteosarcoma has spread (metastasized) to the lungs. Contrast dye may be injected by IV to get a better image of the tumor. This is because tumors absorb the radioactive dye causing the tumor to appear as a brighter spot in the scan. However, with CT scans there are sometimes false positive results, especially with smaller lesions, so a biopsy confirmation of lung disease is sometimes required.

Before treatment, a spiral CT scan is recommended to be done to assess lung metastases. The minimum criteria for lung metastases determined by spiral CT scanning are 3 or more lesions, which are greater than 5 mm in maximum diameter, or a single lesion greater than 1 cm.

A chest CT scan is recommended prior to surgery, as well as after the last cycle of chemotherapy if there were no lung metastasis on the CT scan at diagnosis. For patients with lung metastasis, CT scans are recommended 3 month after thoracotomy (surgery to remove lung metastasis), and then every 6 months.