OPTIMIZING CONTRAST-ENHANCED CRANIAL CT FOR DETECTION OF BRAIN METASTASES

Purpose. In order to optimise contrast-enhanced CT in the detection of brain metastases, we investigated how sensitivity was affected by an increase in contrast medium dose and a reduction in slice thickness. M aterial and Methods: A total of 198 cases of known primary malignancy with suspected brain metastases were investigated in three consecutive contrast-enhanced CT examinations. The first was a standard CT examin ation with an injection of 100 ml contrast medium (300 mg I/ml) and a slice thickness of 10 mm. A further 100 mi contrast medium was given a nd the second examination was performed immediately afterwards with th e same slice thickness as the first. This was followed by the third ex amination, which used a slice thickness of 5 mm. The standard contrast -enhanced CT images were compared with the double-dose images and with the images of reduced slice thickness (5 mm instead of 10 mm). Result s. The double-dose images demonstrated an 8-18% increase in the number of brain metastases detected compared to the standard contrast-enhanc ed CT; the images of the 5-mm-thick slices showed a further 22-33% inc rease. The comparison between the standard contrast-enhanced CT images and the images with both thinner slices and the double dose of contra st medium demonstrated a 32-55% increase in the number of metastases d etected. Conclusion: A considerable increase in sensitivity (32-55%) i n contrast-enhanced CT can be obtained by reducing the slice thickness and increasing the contrast medium dose. This optimised technique sho uld be the method of choice in patients with known primary malignancy and suspected brain metastases.