[Study of the liver and the portal venous system with digital rotational angiography].

PURPOSE: Digital subtraction angiography is of common clinical use for the evaluation of vascular disease. The rotation of the X-ray tube around the patient's body during contrast medium injection was first proposed in the early seventies in the neuroradiologic field; only recently it has been applied to the evaluation of vascular structures and abdominal parenchymatous organs. We investigated the potential clinical value of digital rotational subtraction angiography in the evaluation of the hepatic arteries and of the portal venous system.

MATERIALS AND METHODS: Digital rotational subtraction angiography was performed in 46 patients (34 males and 12 females), mean age 59.3 years (range: 43-72). All the patients underwent digital rotational subtraction angiography after ultrasonographic, CT and/or MRI imaging for evaluation of hepatocellular carcinoma (31 patients) prior to trans-arterial chemoembolization, hepatic metastases from gastrointestinal cancer (9 patients) and pre-surgical study in portal hypertension (6 patients). Digital rotational subtraction angiography was performed using the following technical parameters: a maximum frame rate of 10 views per second, a 1024 x 1024 matrix, a rotation time of 5 seconds, a rotational arch of 90 degrees with a speed of 30 degrees/second. Digital rotational subtraction angiography of the liver was carried out after positioning of a Cobra angiographic catheter in the proper hepatic artery or in the left or right hepatic artery, and subsequent injection of 20-30 ml on contrast medium at a flow rate of 4-7 ml/sec. Conversely, in the portal study the catheter was placed in the splenic or superior mesenteric artery and contrast was administered at 10 ml/sec for an amount of 40-60 ml. Conventional, non-rotational angiography was always obtained with the same catheter and less contrast medium (15-25 at 4-7 ml/sec in the hepatic study, 25-40 ml at 5-7 ml/sec in the portal study). We have evaluated the diagnostic quality (rated as equal, superior or inferior) and the presence of image noise of digital rotational subtraction angiography when compared to digital non-rotational subtraction angiography. We also evaluated the tolerability and the mean time to perform the examination.

RESULTS: Compared to non-rotational digital subtraction angiography, the diagnostic quality of digital rotational subtraction angiography was superior in 26 cases, equal in 20 and never inferior: these results are particularly evident in cine-mode. Diagnostic efficacy was similar in the arterial phase and generally better in the venous phase. Image noise was always perceptible, mostly in lateral and oblique views and is related to the patient's size. Noise especially hindered evaluation of the portal venous phase. Digital rotational subtraction angiography was well tolerated by all patients, although its most significative drawback was the prolonged apnea time required (about 8 seconds per single rotation) which can sometimes be difficult for elderly patients. Examination duration is about 5 to 10 minutes. Contrast medium doses required never exceeded 20-60 ml.

DISCUSSION: Current evaluation of an hepatic lesion requires injections and multiple views to fully delineate arterial anatomy. This requires the radiologist to create a mental 3-D rendering based upon a 2-D view, obtained on the basis of the radiologist's experience. Rotational angiography, when reviewed in cine-loop, allows a better 3-D rendering than conventional angiography, increasing the advantages of the multiple views obtained from a single angiographic run and allowing an exact imaging of the course and direction of the hepatic arterial branching, making selective catheterization during trans-arterial chemoembolization or other interventional procedures easier. Magnification further improves the evaluation of a mass and of the arterial tree. In hepatic surgery, the most important problem is the precise knowledge of the segment involved and the position of the lesion inside the segment, since a mass in the middle of the segment requires a segmentectomy while a mass near the borders is treated by a larger resection. Digital rotational subtraction angiography improves the visibility of vascular anatomy, allows a better knowledge of hepatic artery branches and improves the angiographic investigation of the liver, permitting a correct spatial assessment.

CONCLUSION: Digital rotational subtraction angiography is a useful tool for the evaluation of the liver as well as for transarterial chemoembolization or other interventional procedures. Images are obtained during a single contrast injection, with a better 3-D rendering of the hepatic artery and the portal venous system: no other method provides as complete a visualization of liver vascular anatomy after a single injection of contrast medium in one examination series. (ABSTRACT TRUNCATED)