Optimization of the Scan Protocol for the Reduction of Diaphragmatic Motion Artifacts Depicted on CT Angiography: a Phantom Study Simulating Pediatric Patients with Free Breathing

OBJECTIVE: This study was designed to optimize the scan protocol of CT angiography to reduce diaphragmatic motion artifacts in pediatric patients with free-breathing. MATERIALS AND METHODS: A phantom with twelve tubes with different diameters was constructed. To simulate free-breathing, the phantom was connected to a motor, and the phantom moved along the axis of scan. Scans were performed under several conditions: different pitch (1, 1.5) and gantry rotation time (0.37 and 0.75 sec), and different movement range (1 cm, 3 cm) and rates (20/min, 40/min). For CT scanning, a 16-channel CT scanner was used and fixed factors of the CT protocol were as follows: 100 effective mAs, 80 kVp, reconstruction with a soft-algorithm, beam collimation 16x75 mm, reconstruction thickness of 1 mm, and an interval of 0.5 mm. CT scans were repeated five times. Each tube was evaluated with the use of a grading system (0 for images where tubes were not discriminable and 2 for images where tubes were clearly discriminable). RESULTS: A higher pitch and shorter gantry rotation time produced images with a higher grade. Average grades for the higher pitch (1.5) and faster gantry rotation time (0.37 sec) for each combination of movement were as follows: 1.94 (range 1 cm and rate 20/min), 1.42 (range 1 cm and rate 40/min), 0.86 (range 3 cm and rate 20/min) and 0.52 (range 3 cm and rate 40/min). Average grades for the lower pitch (1) and slower gantry rotation time (0.75 sec) for each combination of movement were 1.08, 0.56, 0.32 and 0.08, respectively. CONCLUSION: The scanning speed and especially the pitch are important parameters for CT scans to overcome a respiratory motion artifact.

A New Technique for Superselective Catheterization of Arteries: Preshaping of a Micro-Guide Wire into a Shepherd's Hook Form

OBJECTIVE: We wanted to introduce a new technique for superselective catheterization of arteries with preshaping of a micro-guide wire into a shepherd's hook form, and this is useful for superselection of small arteries branching at an acute angle from a large parent artery for the treatment of tumors and hemorrhages. MATERIALS AND METHODS: We developed a superselective catheterization technique by using preshaping of a micro-guide wire into a shepherd's hook form. We encountered six patients in our practice for whom we failed to catheterize the small tumor-feeding arteries that branched at an acute angle from wide parent arteries during chemoembolization of hepatocellular carcinoma; the parent arteries were the right inferior phrenic artery (n = 4) and the left gastric artery (n = 1) from the celiac axis with celiac stenosis due to compression by the median arcuate ligament and the proper hepatic artery from the gastroduodenal artery (n = 1) in a patient who had celiac axis occlusion with collateral circulation via the pancreaticoduodenal arcade from the superior mesenteric artery. In these consecutive six patients, we tested the usefulness of this new technique with employing preshaping of a micro-guide wire into a shepherd's hook form for superselective catheterization of targeted vessels. RESULTS: The target arteries were successfully catheterized and satisfactory transcatheter arterial chemoembolization was performed in all six patients. There were no significant complications such as arterial dissection. CONCLUSION: We developed a technique that is effective for superselection of vessels with preshaping of micro-guide wire into a shepherd's hook form, and we successfully applied it during chemoembolization of hepatocellular carcinoma. This technique can be useful for superselection of small arteries that branch from a large parent artery at acute angles for the treatment of tumors and hemorrhages.