Abdominal MDCT: protocols and contrast considerations

Abstract

Multidetector computed tomography (MDCT), is the latest breakthrough in CT technology. Thin sections can now be acquired a routine basis in a single-breathhold with 3D-isotropic reconstructions. This results in improved lesion detection of benign as well as malignant abdominal tumours. The ability to scan through the entire abdomen in seconds allows multiphasic acquisitions. Therefore precise timing and optimized contrast is of great importance.

Hypervascularized solid abdominal tumours are best depicted within the time generally regarded as the arterial dominant phase in MDCT, conversely hypovascular lesions are best depicted during venous phase imaging. The acquisition of an early arterial phase provides precise documentation of the arterial vascular system and should be obtained in preoperative abdominal imaging. Three clear separate circulatory phases enable best results in the pretherapeutic work-up of abdominal patients.

Regarding follow-up oncologic work-up in colorectal metastatic disease a venous dominant phase might be the optimal protocol. Regarding contrast optimization, the traditional concept of imaging, where the injection duration equals the scanning duration cannot be used without modifications. To ensure adequate vessel opacification as well as soft tissue imaging with fast MDCT acquisitions, the iodine administration rate needs to be increased. This can be achieved either by an increase of injection flow rate or—more conveniently—by using a higher iodine concentration of the contrast medium. Especially for hypervascular tumours, e. g. HCC, a considerably to far higher contrasts can be achieved using higher concentrated contrast material. The overall improvement in precise timing and better visibility enable a comprehensive approach to abdominal imaging in MDCT.