Biomedical subjects

A G Tonni

Publications and source records attributed to A G Tonni.

5 recordsLinked to original sources

PubMed1995

[Diagnostic pitfalls in magnetic resonance angiography].

The authors report on their clinical experience with Magnetic Resonance angiography (MRA) pitfalls. January, 1989, to February, 1995, six hundred MRA examinations were performed in different vascular districts, with a 1.5-T superconductive magnet, the time-of-flight (TOF) technique and 2D and 3D acquisitions. Intracranial arteries, epiaortic vessels and renal arteries were studied with FISP 3D sequences; intracranial veins, thoracic vessels, vena cava and pelvic vessels were studied with FISP 2D sequences. Pitfalls were observed in 56 of 600 MRA exams (9.3%). Of 56 pitfalls, 26 (46.4%) were in epiaortic vessels, 15 (26.7%) in intracranial vessels, 6 (10.7%) in renal arteries, 6 (10.7%) in thoracic vessels, 1 (1.7%) in the inferior vena cava and 2 (3.5%) in iliac vessels. Stenoses were overestimated in 21 patients and underestimated in three; 16 patients were misdiagnosed and 16 were false positives. As for cerebral vascular lesions, 5 aneurysms and 7 transverse sinus thromboses were false positives, while 3 lesions were misdiagnosed as venous angiomas. As for 26 MRA exams of thoracic vessels, stenoses were overestimated in 16 patients and underestimated in 10 patients with subclavian steal syndrome, where the left vertebral artery was misinterpreted as occluded. In 6 MRA exams of thoracic vessels, 1 patient was misdiagnosed as having an aneurysm and 5 patients were misdiagnosed as having lung cancer infiltrating aorta and superior vena cava. As for renal vessels, 2 normal renal arteries were misdiagnosed as false positives and 4 stenoses were overestimated. In the inferior vena cava, a partial agenesis was misinterpreted as thrombosis. In 2 MRA exams of iliac vessels, a stenosis and a thrombosis were misinterpreted as false positives. Our experience suggests that MRA pitfalls are caused by the incorrect use of the various techniques. The pitfalls we observed can be classified as caused by three types of artifacts: saturation, turbulence and paramagnetic substance artifacts.

Diagnostic Errors↗

PubMed1994

Magnetic resonance angiography of the left renal vein.

The authors evaluated magnetic resonance angiography (MRA) as a possible diagnostic method to image the left renal vein. Twenty-five patients with abdominal aortic aneurysm underwent both plain and contrast-enhanced CT, as well as two-dimensional (2D) sequential time of flight (TOF) MRA. MRA images were evaluated on the basis of the results of CT, taken as the "gold standard" for vessel demonstration. MRA was performed with a 1.5 T superconductive magnet (Magnetom), fast imaging with steady-state free precession (FISP) 2D sequence (TR 40 ms, TE 10 ms, FA 18 degrees). Images were acquired in breath-hold on the coronal and sagittal plane and reconstructed according to maximum intensity projection (MIP) and targeted-MIP techniques. MRA images acquired on the sagittal plane correctly showed the retroaortic course on the left renal v. in six cases. On the coronal plane, targeted-MIP reconstructions for the course of the left renal v. correctly detected its outlet at the level of the inferior vena cava in five cases and of the left iliac v. in one case. MRA appears to be a promising noninvasive vascular imaging technique capable of correctly detecting the course and the outlet of the left renal v. We particularly noticed that the left renal v. can be imaged in a few seconds by using only one scout view with 2D sequential TOF technique on the sagittal plane at the level of the abdominal aorta.

Aged↗

PubMed1994

[Anesthesiological problems in magnetic resonance].

A prospective study was carried out on 68 patients examined with Magnetic Resonance Imaging (MRI) under general anesthesia. Mean patients age was 10 years (range: 9 days to 77 years). MRI was performed with a 1.5 T superconductive magnet and different anatomical regions were studied: the brain in 63 cases, the lumbar spine in 3, the cervical spine in 1 and finally the upper abdomen in 1 patient. The patients 0-10 years old were anesthetized with isoflurane, while those 11-77 years old were given i.v. propofol and isoflurane. Severe complications occurred in 2 patients only (3%): a 3-year-old child presented respiratory depression and a 21-year-old man had a bronchospasm. Minor complications occurred in 5 more patients. Image quality was excellent in 75% of cases, while few movement artifacts were observed in the extant 25%. To conclude, isoflurane anesthesia is a safe, effective and efficient type of sedation for the patients to be submitted to MRI which can be used also on an outpatient basis.

Adolescent↗

PubMed1993

[Carotid bifurcation: angiography with magnetic resonance versus carotid angiography].

The reliability of Magnetic Resonance Angiography (MRA) was investigated in the study of stenosis and obstruction of carotid bifurcation; digital carotidography was the gold standard. Twenty-five consecutive patients with clinical suspicion of cerebrovascular insufficiency entered the study. MRA was performed with a 1.5 T superconductive magnet (Magnetom Siemens) and a linear head coil. The TOF 3D (FA 20 degrees, TR 30 ms, TE 7 ms) technique was applied. Images were acquired on the sagittal plane and rotated in postprocessing according to MIP on the z axis from 60 to 120 degrees (step 5). MRA exhibit 80.5% sensitivity, 96% specificity, 89.4% accuracy, 94.7% positive predictive value and 86.3% negative predictive value. When calculating the interrupted flow relative to hemodynamically significant stenoses (range 31%-occlusions), MRA sensitivity was 80.5%, specificity 100%, negative predictive value 86.3%, positive predictive value 94.7% and overall diagnostic accuracy 91.2%. MRA is to be considered a diagnostically reliable procedure in the study of carotid bifurcation and its diagnostic accuracy may even be increased in the future by the possible assessment of over- and underestimated cases.

Adult↗

PubMedDate not supplied

[Neoplasms of the glomus caroticum: magnetic resonance angiography versus magnetic resonance].

This work was aimed at investigating the diagnostic role of Magnetic Resonance angiography (MRA) versus spin-echo images in the study of carotid paragangliomas. Ten patients affected with carotid paragangliomas were studied; surgery was the gold standard. MR examinations were performed with a superconductive 1.5 T magnet and a linear head coil. T1-weighted (TR 500 ms, TE 15 ms, 256 x 256 matrix) and T2-weighted (TR 2000 ms, TE 15/90 ms, 256 x 256 matrix) spin-echo sequences were acquired. TOF 3D (flash: FA 25 degrees, TR 30 ms, TE 7 ms) MRA images were acquired; coronal and sagittal images were rotated according to the MIP. Spin-echo images demonstrated the typical "salt and pepper" pattern in all cases. In 6 cases (lesion diameter > 3 cm) the vascular structures of the paragangliomas and carotid dislocation were clearly demonstrated by MRA. MRA also depicted carotid dislocation in all cases. In conclusion, in the evaluation of carotid paragangliomas > 3 cm diameter, MRA yields complementary information on vascular structures and dislocation of carotid vessels to spin-echo MR sequences.

Adult↗