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Biomedical subjects

P Pavone

Publications and source records attributed to P Pavone.

At least 145 records · Page 8Linked to original sources
PubMed1992

Carotid arteries: evaluation with low-field-strength MR angiography.

Magnetic resonance (MR) angiography of neck vessels was performed with a 0.2-T permanent magnet by using a two-dimensional, time-of-flight technique. Thirty-one patients were included in the study. The imaging parameters used included a repetition time of 60 msec, an echo time of 10 msec, a 90 degrees flip angle, and a 192 x 256 matrix; 40-50 sequential two-dimensional sections were acquired through the neck. Stenosis was graded on a scale of 1-5. Correlation of digital and MR angiography was made in the clinically nonrelevant cases (stenoses of grades 1 and 2), with overestimation to grade 3 in six cases. Two grade 3 stenoses were overestimated as grade 4. Severe stenoses were correctly characterized in all but one case, which was underestimated because of a segmental short extension of the stenotic lesion. Obstructions were found in two cases. Areas with a lack of signal were observed in four patients with severe stenosis and in two with tortuous arteries. Correct diagnosis, however, was achieved with analysis of the maximum intensity projection animation display. Low-field-strength MR angiography has the same clinical value as that performed with high field strengths.

Adult↗
PubMed1992

Arteriography in diagnosing hepatocellular carcinoma.

The diagnostic role of arteriography in the evaluation of hepatocellular carcinoma is pointed out. In the identification of large lesions angiography achieves a sensitivity of 100%. However, when evaluating small lesions (under 5 or 3 cm in diameter), the sensitivity is reported to be 82-89%. To increase the sensitivity, different special techniques have been developed which require angiographic placement of a catheter. These include CT arteriography, CT arterial portography and CT after intraarterial injection of iodized oil. Particularly with the two latter techniques, the sensitivity in identification of small hepatocellular carcinoma reaches a value of 91-95%. Angiography can also be proposed for the characterization of neoplastic lesions in cirrhotic livers. Its specificity is 72% in the differential diagnosis of hepatocellular carcinoma and adenomatous hyperplastic nodules. Small grade I hepatocellular carcinoma can simulate this benign lesion at angiography, as well as at histology. Finally, angiography may still play a role in the preoperative staging of hepatocellular carcinoma both for the diagnosis of satellite lesions and for the identification of vascular invasion.

Angiography↗
PubMed1992

[Magnetic resonance imaging of the esophagus with lumen opacification using a specific contrast agent].

A new contrast agent has been developed for the opacification of the esophageal lumen in Magnetic Resonance (MR) Imaging. The contrast agent consists of an emulsion of low-density and high-viscosity barium paste employed for the CT study of the esophagus (E.Z.E.M., Westbury, USA) and a small amount of Gadolinium-DTPA (Magnevist, Schering, Germany), diluted in 3 ml of saline solution. In vitro evaluation of the contrast solution showed high-signal intensity on T1-weighted SE sequences. The study was subsequently performed on 5 healthy volunteers and 30 subjects with clinical indication for MR Imaging of the chest. The complete opacification of the esophagus was obtained in 12 of the 16 patients (75%) who presented no pathological involvement of the esophagus. The esophageal lumen was completely opacified in 8 patients with esophageal carcinoma and in 1 case of esophageal leiomyoma. In the cases with esophageal carcinoma, lumen opacification allowed the evaluation of tumor growth (concentric or eccentric), a more detailed definition of tumor extent, with assessment of neoplastic wall thickening, and the evaluation of the possible infiltration of adjacent organs. Lumen opacification was obtained in 8 of 10 patients (80%) affected with other chest conditions secondarily involving the esophagus. In these cases, lumen opacification helped to localize the esophagus and to evaluate its involvement by adjacent tumors.

Adult↗
PubMed1991

[Digestive hemorrhage caused by rupture of an aneurysm of the superior pancreaticoduodenal artery].

Aneurysms of the pancreaticoduodenal artery are rare. Nonoperative management of an iatrogenic superior pancreaticoduodenal artery aneurysm which ruptured into the duodenal stump of a Billroth II partial gastrectomy, is described here. Based on a literature review, both aetiology and site of rupture of this observation are very uncommon. Super-selective angiography was used for diagnosis and embolisation for definitive treatment.

Aneurysm↗
PubMed1991

Evaluation of hematoma by MRI in follow-up of aorto-femoral bypass.

We selected a population of 20 patients with atherosclerotic disease, submitted to implantation of aorto-femoral bypass graft. These patients were studied by MRI with T1- and T2-weighted sequences (w.s.) using a 0.5 T superconductive magnet. Investigation was performed at 1 wk, 1, 3, and 6 mo after dacron implantation, to evaluate the normal evolution of hematoma and the potential development of complications. At the first week examination, hematoma presented medium signal intensity on T1 w.s. and high signal intensity on T2 w.s.; at 1 mo control the amount of hematoma was slightly reduced and we found persistence of high signal intensity on T2 w.s.; progressive reduction of size and signal intensity on T2 w.s. was noted at 3 mo control, in patients operated for peripheral vascular disease; on the other hand we found persistence of high signal intensity in T2 w.s. in patients treated for abdominal aortic aneurysms; only after 6 mo it was evident in all patients fibrotic evolution of the collection and low signal intensity in both T1 and T2 w.s. Thus, MRI study was useful in the evaluation of patency, morphology, and in detection of intraluminal thrombosis, but also in the characterization of periprosthetic hematoma.

Aged↗
PubMed1991

Intraarterial portography with gadopentetate dimeglumine: improved liver-to-lesion contrast in MR imaging.

Magnetic resonance imaging during arterial portography (MRAP) was performed by the authors in a selected group of 12 patients with hepatic lesions. A low dose of gadopentetate dimeglumine (4 mL of a 0.5-mol/L solution, corresponding to a dose of 0.05-0.07 mmol/kg) was injected into the superior mesenteric artery during acquisition of breath-holding gradient-echo or rapid acquisition spin-echo images. Images were always acquired during the first passage of gadopentetate dimeglumine through the liver parenchyma. An increase in liver-to-lesion contrast was obtained with MRAP imaging (contrast-to-noise ratio = 8 +/- 1.8 vs 19 +/- 2.7). Signal intensity enhancement of the liver was high (signal-to-noise ratio = 9.48 +/- 2.42), while the lesion presented no significant enhancement (signal-to-noise ratio = 0.55 +/- 0.22). Lobar portal vein thrombosis was detected in one patient owing to lack of enhancement of the left lobe of the liver. No side effects related to administration of iodinated and paramagnetic contrast agents were observed. This new technique provides specific enhancement of liver parenchyma with improved liver-to-lesion contrast.

Adult↗
PubMed1991

[Mediastinal lymphatic staging of bronchial cancer. Respective value of x-ray computed tomography and magnetic resonance imaging. Radio-surgical comparison].

Fifty patients with bronchogenic carcinoma were prospectively studied by both CT and MR during 10 days preceding thoracotomy. Results of CT and MR were compared with the surgical and pathology findings. No statistically significant difference was found between the two imaging methods for the evaluation of node involvement (N2). MR appear to be superior to CT in the aortopulmonary and subcarinal areas.

Adult↗
PubMed1991

[Optimization of the techniques for studying the upper abdomen with magnetic resonance. II. Changes in the intrinsic contrast].

Magnetic Resonance imaging of the upper abdomen was performed on more than 300 patients. The aim of the study was to determine the influence of spin-echo parameters on intrinsic image contrast. Different TR (ranging 260 to 2000 ms) and TE (ranging 20 to 120 ms) values were employed in two patients with a hepatic metastases and in a healthy volunteer with a hepatic cyst. The highest liver-to-lesion contrast was observed when the shortest TR and TE values (260 and 20 ms, respectively) were used, while the lesions appeared isointense with the surrounding parenchyma with TR 800 ms. In T2-weighted images TR 2000 ms allowed the complete recovery of longitudinal magnetization, giving a contrast relative only to the T2 of the lesion.

Humans↗
PubMed1990

Abdominal aortic aneurysm evaluation: comparison of US, CT, MRI, and angiography.

We studied 26 cases of abdominal aortic aneurysm with magnetic resonance imaging (MRI), computed tomography (CT), ultrasonography (US), and angiography. Data acquired were compared to those obtained at surgery. Diameter of the aneurysm was correctly defined in all cases by CT and MRI, while angiography underestimated the diameter of lesions without peripheral calcifications. Involvement of renal arteries was present in four cases and correctly diagnosed with MRI and angiography in all of them. CT did provide this information in three cases and US were not useful. Also, iliac arteries involvement was depicted by CT, MRI, and angiography in 10 out of 10 patients. Coronal sections of MRI provided comparable images to those of angiography. By comparing these different techniques we verified the good reliability of MRI as investigation tool for an accurate evaluation of aneurysms; its only limit lying in the poor capability of detecting calcifications.

Aged↗
PubMed1990

Three-dimensional in vivo ESR imaging in rats.

The first experiment of tridimensional in vivo ESR imaging at 1.2 GHz is described in this paper. The tails of rats weighing 300-350 grams were visualized using 1 cc of a 50 * 10(-3) M solution of nitroxide free radical injected in the caudal vein. In an even distribution of spin label is assumed this would correspond to a final concentration of about 10(-4) M. A reconstruction from projections was used to obtain the images. The apparatus utilizes stationary field gradients. Projections were obtained by sweeping the main field. For 3D reconstructions, the projections were collected along 32 * 8 field gradient orientations. The whole procedure takes approximately 18 minutes.

Animals↗
PubMed1990

Role of magnetic resonance imaging in the evaluation of aortic graft healing, perigraft fluid collection, and graft infection.

The authors report their preliminary experience in the use of Magnetic Resonance Imaging (MRI) in ten patients who underwent aortic reconstruction. Examinations were performed 1, 4, 12 and 24 weeks after surgery, to examine the presence, size, magnetic characteristics and evolution of periprosthetic collections. The results have shown that periprosthetic collection can be considered normal after aortic reconstructive surgery, because such a perigraft collection (PFC) was present in 90% of the patients studied 1 week after operation, and had disappeared within 24 weeks in all cases. The magnetic characteristics were evaluated by T1 [repetition time (TR) = 480 msec and echo time (TE) = 20 msec] and T2 weighted spin-echo sequences (TR = 1800 msec and TE = 70/120 msec). Variations in the magnetic characteristics, found in sequential examinations, correlated with modifications of the collection and suggested that it was originally blood. The MRI examination performed 24 weeks after surgery gave a low signal intensity in T1 and T2 weighted sequences (w.s.) suggesting periprosthetic fibrosis. These preliminary observations may constitute a starting point for better evaluation of the normal appearance and evolution of the periprosthetic fluid collections following aortic graft implantation and, may be useful for the early detection of infection especially in asymptomatic patients.

Aorta, Abdominal↗
PubMed1990

Comparison of Gd-BOPTA with Gd-DTPA in MR imaging of rat liver.

A new lipophilic compound, gadolinium benzyloxypropionictetraacetate (BOPTA), with a high rate of biliary excretion was assessed as a magnetic resonance (MR) hepatospecific contrast-enhancing agent and compared with Gd-DTPA (diethylenetriaminepentaacetic acid) in MR imaging of normal rats. T1-weighted spin-echo images obtained before and after administration of each contrast agent at doses of 0.25, 0.5, and 1.0 mmol/kg showed greater enhancement of the liver with Gd-BOPTA than with Gd-DTPA, with the advantage more evident at lower doses. Images obtained with an inversion recovery sequence at the null value of rat liver parenchyma after injection of 0.1- and 0.5-mmol/kg doses of the contrast agent provided better evidence of the greater and longer-lasting hepatic enhancement due to Gd-BOPTA when compared with that of Gd-DTPA. Gd-BOPTA is a potentially good contrast agent for obtaining prolonged enhancement of the liver, permitting studies during the long time needed to acquire conventional T1-weighted images.

Acetates↗