Effective dose and image quality evaluations of an automatic CT tube current modulation system with an anthropomorphic phantom.

The purpose of this study was to evaluate the consequences of different choices of acquisition parameters on the actual image noise and on the patient dose with an automatic tube current modulation system. The CT investigated was a GE Lightspeed 16-slice and an anthropomorphic phantom was used to simulate the patient. Several acquisitions were made varying noise index (NI), kilovoltage and pitch values. Tube current values were compared for the different acquisitions. Patient dose was evaluated in terms of volumetric computed tomography dose index (CTDI(vol)) and also as effective dose. The noise actually present in the images was analyzed by a region of interest analysis considering representatively phantom sections in the regions of the shoulders, of the lungs and of the abdomen. The obtained results generally evidenced a good agreement between the noise index and the measured noise for the abdomen sections, whereas for the shoulders and the lungs sections the measured noise was respectively greater and lower of the NI. Varying the kV the automatic current modulation system provided images with a substantially constancy of the actual noise and of the patient dose. An increase of the pitch generally decreased the patient dose, whereas the noise was slightly greater for the lowest pitch and almost constant for the other pitch values. This study outlines some important relationships between an automatic tube current modulation system and other CT acquisition parameters, providing useful informations for the choice requested by radiologists in the task of optimization of the CT acquisition protocols. Unless there are other considerations in place, pixel pitches below 1.375 should be avoided, and kVp settings can be changed with no real impact on dose or image noise.

Pulmonary arteriovenous malformations: percutaneous treatment preserving parenchyma in high-flow fistulae.

PURPOSE: The aim of our study was to illustrate the benefits of percutaneous treatment by embolisation of high-flow pulmonary arteriovenous malformations (PAVM) in patients suffering from hereditary haemorrhagic telangiectasia (HHT; Rendu-Osler-Weber disease). MATERIALS AND METHODS: From December 2001 to February 2007, we embolised 60 PAVMS in 35 procedures performed on 30 patients, all referred by the HHT centre in Crema, and enrolled in a screening programme of HHT families. All patients underwent clinical evaluation, contrast-enhanced ultrasound (CEUS) and spiral computed tomography (CT). Embolisation was made with nonmagnetic metallic coils via femoral venous access; an endovascular Amplatzer device was used in one patient only. RESULTS: All embolisations were performed without difficulty. One patient only developed partial temporary aphasia, which resolved in 72 H. At spiral-CT follow-up, we generally demonstrated exclusion from circulation of treated PAVMS and regression of clinical symptoms. In the case of new lesions or recanalisation, further embolisation was possible: CONCLUSIONS: Percutaneous embolisation has recently become the initial treatment option in PAVM owing to its good results and minimal invasiveness compared with thoracotomy. Our experience is in agreement with the literature: the procedure has a low complication rate, provides very good technical and clinical results and avoids resection of healthy pulmonary parenchyma.

[Transjugular intrahepatic portasystemic shunt (TIPS). Role of ultrasonographic methods]. / Anastomosi porto-sistemica intraepatica per via transgiugulare (TIPS). Ruolo delle metodiche ultrasonografiche.

The transjugular intrahepatic portosystemic shunt (TIPS) is a new interventional radiology procedure which may be assisted by modern ultrasound techniques (US). Color-Doppler US can be used for patients selection, during TIPS and in the follow-up. In a 20-month period, 71 patients were examined: 3 of them were excluded because of the absolute contraindications shown by US; in 14 of the remaining 68 patients, US demonstrated relative contraindications, such as hepatocellular carcinoma, partial portal vein thrombosis and right internal jugular vein occlusion. During the maneuver, US helped to select the most adequate veins for shunt creation and was especially useful in guiding portal vein puncture, thus allowing technical success to be achieved in 65/68 patients. The mean number of passes per patient was 2.7 and no procedure-related complications were observed. US was also used to investigate TIPS patency the day after the maneuver and to monitor shunt function during the follow-up. Color-Doppler US correctly diagnosed both 3/65 early occlusions and 9/65 late stenoses; in particular, in 18/65 patients US showed gradual flow reduction through TIPS, but clinical and endoscopic findings of malfunction appeared only in 9/65 patients whose mean reduction rates exceeded 50% at Doppler US.