[Clinical indications for the use of cardiac MRI. By the SIRM Study Group on Cardiac Imaging]

Cardiac magnetic resonance (CMR) is considered an useful method in the evaluation of many cardiac disorders. Based on our experience and available literature, we wrote a document as a guiding tool in the clinical use of CMR. Synthetically we describe different cardiac disorders and express for each one a classification, I to IV, depending on the significance of diagnostic information expected.

Multiple 3D inversion recovery imaging for volume T1 mapping of the heart

In this article, a three-dimensional inversion recovery sequence was optimized with the aim of generating in vivo volume T(1) maps of the heart using a 1.5-T MR system. Acquisitions were performed before and after gadolinium diethylenetriamine penta-acetic acid (Gd-DTPA) administration in one patient with hypertrophic cardiomyopathy and in two healthy volunteers. Data were acquired with a multishot fast field echo readout using both ECG and respiratory triggers. A dedicated phantom, composed of four solutions with different T(1) values, was positioned on the subjects' thoracic region to perform patient-specific calibration. Pixel based T(1) maps were calculated with a custom Matlab(®) code. Phantom measurements showed a good accuracy of the technique and in vivo T(1) estimation of liver, skeletal muscle, myocardium, and blood resulted in good agreement with values reported in the literature. Multiple three-dimensional inversion recovery technique is a feasible and accurate method to perform T(1) volume mapping.

Swelling of the submandibular glands after administration of low-osmolarity contrast agent: Ultrasound findings

Swelling of the salivary glands occurring after injection of iodine based contrast agent is a rare late adverse reaction. Only a few cases in the literature report such diagnostic findings. We present our color Doppler ultrasound findings in a case of swelling of both submandibular glands occurring after administration of iodinated contrast agent.

Tachycardias in children originating in the right ventricular outflow tract: lack of clinical features predicting the presence and severity of the histopathological substrate

The aim was to determine whether the clinical features of tachycardias originating from the right ventricular outflow tract in children with an apparently normal heart could predict the presence and the severity of the histopathological substrate. Thirteen children (median age 6 years; range 6 months-12 years) with tachycardia originating from the right ventricular outflow tract of apparently normal hearts, were assessed by echocardiography, heart catheterization with angiography, endomyocardial biopsy (13 patients) and magnetic resonance imaging (MRI) (nine patients). Tachycardia was symptomatic in six and sustained in nine. Endomyocardial biopsy and MRI revealed acute myocarditis in five patients (38%), fatty infiltration of the right ventricle in two (15%), and minor histologic abnormalities in three (23%). Myocarditis was diagnosed in three of nine patients with sustained ventricular tachycardia, as opposed to two of four with non-sustained tachycardia (p = NS); in three of six symptomatic versus two of seven asymptomatic patients (p = NS); and in two of eight patients in whom ventricular tachycardia was induced during exercise testing as opposed to one of three in which it was not inducible (p = NS). A histopathological substrate was found in six of nine patients with sustained ventricular tachycardia, and in all four with non-sustained tachycardia (p = NS); in five of six patients with symptoms versus five of seven asymptomatic patients (p = NS); and in five of eight with inducible ventricular tachycardia during exercise testing versus all three in whom it was not inducible (p = NS). The mean rate of tachycardia was 184+/-39 beats min(-1) in patients with myocarditis, as opposed to 171+/-48 in patients without myocarditis (p = NS); and 163+/-33 in patients with a histopathological substrate compared with 210+/-65 in patients without a histopathological substrate (p = NS). It is concluded that a histopathological substrate is present in the greater majority of children affected by the so-called right ventricular outflow tract tachycardia, but that the clinical features of the tachycardia do not predict the presence and the severity of this histopathological substrate.

Extracardiac Fontan operation for complex cardiac anomalies: seven years' experience

METHODS

Between 1988 and 1995, 60 patients with complex cardiac anomalies underwent a total extracardiac cavopulmonary connection, a combination of a bidirectional cavopulmonary anastomosis with an extracardiac conduit interposition between the inferior vena cava and pulmonary arteries, except in one patient in whom direct anastomosis was possible. In 40 patients the total extracardiac cavopulmonary connection followed preliminary bidirectional cavopulmonary anastomosis, associated with a modified Damus-Kaye-Stansel anastomosis in 16. The conduits were constructed of Dacron fabric (n = 34), homografts (n = 3), and polytetrafluoroethylene (n = 22).

RESULTS

Total early failure rate was 15% (n = 9). Six patients died, and three more had conduit takedown owing to pulmonary artery stenosis and hypoplasia (n = 2) and severe atrioventricular valve regurgitation (n = 1). Two other patients required anastomosis revision owing to stricture. In a mean follow-up of 48 months (6 to 86 months) there were no late deaths (actuarial 5-year survival 88% +/- 4%); 52 of 54 patients are in New York Heart Association class I or II. Two patients required pulmonary artery balloon dilation or stent implantation, or both, after total extracardiac cavopulmonary connection. Late tachyarrhythmias were detected in four of 54 patients: two had sick sinus syndrome with flutter necessitating a pacemaker implantation and two had recurrent flutter (actuarial 5-year arrhythmia-free rate 92% +/- 4%). Conduit patency was evaluated by serial magnetic resonance imaging studies. Preliminary data showed a 17.8% +/- 7.6% mean reduction in conduit internal diameter during the first 6 months after total extracardiac cavopulmonary connection, with no progression over the next 5 years.

CONCLUSION

These results demonstrate that the total extracardiac cavopulmonary connection provides good early and midterm results and may reduce the prevalence of late arrhythmias in patients undergoing the Fontan operation.

[Role of computerized tomography in bladder carcinoma treated with simultaneous combined radiotherapy and chemotherapy]

We report on the pneumocystography-CT follow-up of locally aggressive bladder carcinoma patients treated with combined and simultaneous irradiation and chemotherapy. Particular attention was paid to assess residual thickening of the wall involved by the tumor, which is the most critical parameter to discriminate a persistent from a resolved condition. We examined 16 patients (mean age: 66.5 years) with histologically locally advanced urinary bladder cancer staged T2-T3. All patients underwent the first CT exam of the bladder with the pneumocystography technique before therapy, for disease staging, another exam after chemotherapy and a third one after simultaneous irradiation and chemotherapy. The endoluminal mass completely regressed in all cases, with normal endoscopic findings. In 9 of 16 cases, the bladder wall was thickened in the tumor site, with normal mucosal surface. The histology of bioptic specimens obtained during cystoscopy showed a high frequency of phlogistic reactions from foreign bodies, corresponding to the bladder wall thickening seen on CT images. We conclude that, in extensive neoplastic bladder wall involvement, therapy-induced histologic regressive phenomena can cause a granulomatous reaction in the bladder wall, thus thickening it, which is the most frequent sign in these cases but that, in our experience, was never associated with tumor invasion. This should be always considered in the CT studies performed after this kind of combined treatment.

[Iron accumulation in the liver of patients with thalassemia major assessed with low field strength magnetic resonance: correlation with clinico-instrumental parameters]

Eight transfusion dependent patients (3 women and 5 men) with thalassemia major undergoing long-term treatment with Desferoxamine were submitted to MRI, with T2* GE sequences and low field strength. The ratio between liver mean signal intensity and skeletal muscle (L/M) and the ratio between the former and subcutaneous fat (L/F) were calculated in all patients. The results were compared with those of a control group of 7 healthy volunteers (7 men). L/M and L/F ratios were separately correlated with the following parameters: patient's age, transfusion history, serum ferritin, ferritin peak and its onset, transaminases (AST and ALT) and chelation index. The latter is a complex parameter allowing the actual assessment of iron content and of the real efficacy of chelation therapy. In all patients, both the L/M and the L/F ratios decreased significantly (L/M ratio: 0.67 +/- 0.45 vs. 1.2 +/- 0.21, p < 0.02; L/F ratio: 0.39 +/- 0.15 vs. 0.84 +/- 0.11, p < 0.001) relative to the control group. No significant correlation was found between the ratios and any hematochemical parameter, except for r = 0.77 (p < 0.04) between L/F ratio and the chelation index. Our study demonstrates that MRI may play a major role in the examination of thalassemic patients even at low field strength and with GE sequences, which yield good quality images with a relatively short acquisition time. Thus, MRI can be suggested for routine liver studies thanks to its high quality depiction of the liver and to its qualitative and semiquantitative yield. The good correlation between L/F ratio and the chelation index permits MR evaluation of the efficacy of different chelation treatments.

MRI postoperative monitoring in patients surgically treated for aortic dissection

In most cases, surgery of aortic dissections repairs only the ascending portion of the aorta, leaving a residual dissection in the arch and descending aorta. We studied 17 patients operated upon for type A aortic dissection. A total of 42 magnetic resonance imaging (MRI) examinations were performed, with two to five studies per patient (mean 2.47). The studies were done between 5 weeks and 47 months (mean 17.5 months) after surgery. The patients were evaluated by MRI using gated spin-echo and gradient-echo sequences on axial and oblique sagittal views, and in selected cases, coronal views. A high incidence of abnormalities was observed. Pericardial hematoma was observed in 11% of cases, aortic and branch involvement in 41%, abdominal aortic branch involvement in 47%, dilatation of native aorta in 58%, and extension of dissection in 10%. New complications were detected during follow-up in 53% of patients. MRI was helpful in the follow-up of patients operated upon for aortic dissections, owing to its noninvasiveness and multiplanarity. By means of this technique, it was possible to obtain information about the natural history of the disease, as well as information useful for subsequent treatment.

Identification of viable myocardium in patients with chronic coronary artery disease and left ventricular dysfunction: role of magnetic resonance imaging

Nineteen patients (16 men and 3 women, mean age 51 years) with previous anterior myocardial infarction and severe stenosis (> or = 90%) of the left anterior descending coronary artery were studied by magnetic resonance imaging (MRI) without and with contrast media to verify the capability of MRI in identifying viable myocardium in areas of severe systolic dysfunction. In corresponding left ventricular segments, a comparison was made between regional signal intensities (SI) determined on MRI images before and 4, 8, 12, and 30 minutes after administration of paramagnetic contrast media (gadolinium diethylenetriaminepentaacetic acid, 0.4 mmol/kg intravenously) and metabolic parameters determined by iodine 123 phenylpentadecanoic acid (IPPA) scintigraphy. The SI and the time of maximum postcontrast enhancement were analyzed by dividing the left ventricle into 11 segments. Each segment was classified as normal (group 1, n = 116), hibernating (group 2, n = 50), or necrotic (group 3, n = 43) on the basis of the IPPA washout rate (> 30%, 10% to 30%, and < 10%, respectively). Regional SI demonstrated significant differences in absolute values at 12 minutes (group 3: 1.62 +/- 0.58 vs group 1: 1.32 +/- 0.52, p < 0.01, and vs group 2: 1.34 +/- 0.48, p < 0.05) and at 30 minutes (group 3: 1.71 +/- 0.47 vs group 1: 1.21 +/- 0.55, p < 0.01, and vs group 2: 1.49 +/- 0.57, p < 0.05) and in temporal distribution. These results suggest that MRI has a potential role in differentiating viable from necrotic myocardium in patients with chronic severe systolic dysfunction.

Characterization of reversible myocardial dysfunction by magnetic resonance imaging

Some recent cardiovascular applications of nuclear magnetic resonance imaging (MRI) are discussed, on the basis of both literature and personal data. Management of coronary patients has become directed to strategies aiming at salvaging the ischemic myocardium, and MRI can play an important role in providing the necessary data leading to an appropriate assessment. Due to its capability in showing morphofunctional information on wall thickness and thickening, cine-MRI technique can be used to detect myocardial ischemia and infarction, since it allows the acquisition of 16 or more frames of the cardiac cycle which can be displayed in a cine loop format. In an Italian Cooperative Study the role of MRI in discriminating stunned from necrotic areas has been investigated. Comparison of fractional area change by echo versus cine-MR turned out to be almost completely overlapping, but cine-MRI allowed a more accurate measurement of systolic wall thickening due to better visualization of endo- and epicardial borders (more sensitive marker of kinetic damage than wall motion). Other studies have also been performed in order to determine the capability of contrast agents of allowing differentiation between reperfused reversible and irreversible myocardial injury and allowing distinction between reperfused and occlusive myocardial infarction. In a recent study we investigated the MRI possibility of identifying viable myocardium in severely chronic systolic dysfunctioning areas by comparing, in corresponding left ventricular segments, regional perfusion and metabolism at IPPA scintigraphy and regional signal intensity at MR images obtained before and after paramagnetic contrast media administration. The potential role of MRI was shown in the identification of viable myocardium with the use of contrast medium, that is of crucial importance in this respect.

[Characterization of hypertrophic cardiomyopathy with magnetic resonance]

We selected 15 patients with hypertrophic cardiomyopathy (HCM) and 5 with secondary myocardial hypertrophy (SMH). All patients were examined by means of Magnetic Resonance Imaging (MRI) and echocardiography. The MR study was performed with gated T1- and T2-weighted spin echo sequences and cine MRI. We correlated echocardiographic and MRI measurements and found a correlation coefficient (R) of 0.72 for apex thickness, r = 0.84 for posterior wall thickness, 0.76 for the lateral wall and 0.89 for the area at papillary level. Cine MR acquisitions showed signal loss in the systolic phase at the outflow tract in 9 obstructive HCM patients, which was consistent with echocardiographic color Doppler findings. The signal intensity of myocardial tissue was analyzed with MRI. The values were correlated with those of the skeletal muscle. We performed the paired sample t-test on T1- and T2-weighted spin echo sequences between the signal at the septum and that of the free wall in the 15 HCM patients. The analysis showed significant differences on T2-weighted sequences (p < 0.02). Unpaired t-test was performed between the 15 HCM and the 5 SMH patients; the analysis showed significant differences on both T1- (p < 0.01) and T2-weighted sequences (p < 0.04).

[Evaluation of aortic distensibility using cine-MR before and after antihypertensive treatment with calcium antagonists and ACE-inhibitors]

Several studies have been performed in the last years to evaluate arterial distensibility, particularly of the aorta, in hypertension and to estimate the changes of this distensibility after anti-hypertensive treatment. The aim of this study was to assess the aortic distensibility in a group of 10 patients with essential hypertension in comparison with a control group, with regard to the vascular effects of a long-term anti-hypertensive treatment with calcium-antagonists and ACE-inhibitors. All patients were studied using cine-MR imaging, a technique with several peculiarities (multiplanar scanning, intrinsic contrast, etc) that allows simple and quick assessment of the aortic vascular parameters in the ascending and descending tracts. The results of our study show the absence of a significant improvement of aortic vascular areas, and therefore of vessel distensibility, even in the presence of a complete blood pressure normalization in all patients after a 3-month treatment. These data do not confirm previous reports in this setting, based on the ultrasonographic techniques (2D and Doppler echocardiography). Two major reasons may explain our results: first, the rigorous criteria of patient enrollment that we have stated in order to avoid any influence of age and/or other pathologies; second, the ability of MR imaging to allow accurate estimation of aortic vascular parameters and to achieve an excellent intraobserver and interobserver reproducibility in comparison with other techniques. We conclude that MR imaging is the method of choice for the assessment of cardiovascular function and morphology.

[Imaging of atherosclerosis: magnetic resonance]

Atherosclerosis is the disease with the most important social impact in terms of cost and human life. Its study in the prevention and cure of its consequences needs integration using many imaging modalities, and magnetic resonance presents advantages due to its particular characteristics. The Authors make an overview of its indications and potential applications in the assessment of atherosclerotic disease. In vitro studies have demonstrated that it is possible to evaluate the normal and abnormal components of vessel walls by means of magnetic resonance imaging (MRI) as well as fatty deposition and intraplaque hemorrhage. On the other hand, in the in vivo studies, despite the impossibility to make a too fine structural analysis of the vessel wall, MRI allows to easily discriminate between blood flow and parietal wall. This is of great importance in the study concerning arterial aneurysms, that represent a consequence of atherosclerotic disease. Information as the presence, the site, the extension, the collateral vessel involvement and, finally, the presence or absence of dissection are all obtainable by using MRI. In the early 1990's magnetic resonance angiography (MRA) was developed and is now used in clinical practice. By means of this new application of MRI there is the possibility of increasing the non invasive screening of atherosclerosis especially in some body districts. The evaluation of the plaque obtainable by the combined use of MRA and ultrasound studies allows to decrease the employment of traditional and digital angiography. If, as studies predict, we will able to obtain coronary angiograms in the near future, there will be a further increase in the non invasive evaluation and in the prevention of atherosclerotic disease.

Identification of coronary artery by-pass grafts: reliability of MRI in clinical practice

In order to test MRI ability to detect the number and the sites of coronary artery by-pass grafts (CABGs), 22 patients with CABGs were studied. The detection of a neo-vessel in even one of the examination slices was considered as positive for the study, disregarding the difference between its origin and course. With such a criterion, MRI total percentage of vascular bridges identification resulted in 76.1% (51/67) with very low values for CABGs implanted on diagonal, obtuse marginal and posterior descending vessels (11/24 = 45.8%). These results lead to the conclusion that, although MRI has some advantages in the identification of CABGs implanted on the main coronary vessels in the early post-operative period, its extensive use cannot be proposed at the present state of the art.

[Magnetic resonance: the usefulness of gradient-echo refocusing sequences in the diagnosis of aneurysms of the abdominal aorta]

Sixteen patients bearing aneurysms of the abdominal aorta were studied by means of a 0.5 T MR unit. Spin-echo T1-weighted sequences and gradient-echo refocusing sequences were performed. All patients were previously submitted to US; in 8 cases angio CT was performed, and in 6 patients angiography of the abdominal aorta. A comparative analysis with the US findings showed a high correlation coefficient for the maximum diameters (R = 0.93) while site and size evaluations were not accurate. A very high correlation coefficient for the maximum diameters (0.97) was found at the comparative analysis with CT findings, while in two cases an erroneous suprarenal location was described. Angiographic examination provided valuable information about renal and iliac involvement, but the maximum diameters could not be accurately assessed. Spin-echo MRI allowed good evaluation of the maximum size, of location and extent of the aneurysm, as well as of iliac involvement; this technique, however, was useless in the characterization of the thrombus. Gradient-echo refocusing sequences have proven very useful for the identification of endoluminal contours and for the correct evaluation of the thrombus. Spin-echo sequences, on the contrary, accurately assessed only 7 cases, whereas the diagnosis was uncertain in the remaining 4 patients.

Postsurgical follow-up of aortic dissections by MRI

Fifteen patients with surgical repair for dissecting aneurysm were examined by Magnetic Resonance Imaging (MRI), using a 0.5 T super-conductive unit. Follow-up studies were obtained at 1 to 18 months (mean 7.2) post-surgery. T1-weighted spin-echo sequences were acquired with ECG gating on axial, coronal and oblique sagittal planes. In 6 patients gated gradient rephased sequences were also employed. Residual intimal tear in the native aorta was visualized in 11 patients, together with new or progressive extention of the dissection and aneurysmatic development. Gradient rephasing sequences were useful in detecting slow flow and thrombotic deposits and in evaluating relations to aortic vessels and intimal flap. MR images provided useful information on pathology allowing a non invasive evaluation of the status of the aorta.

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.

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.

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.

[Pathologic dilatation of the thoracic aorta: a study using magnetic resonance]

Magnetic resonance (MR) imaging provides detailed evaluation of cardiovascular structures, due to high intrinsic contrast between flowing blood and vessel's lumen. Early application have shown the clinical validity of the technique, with non-invasive, multiplanar imaging of large and medium sized vessels. In this study we evaluate the capabilities of MR in screening out patients with thoracic aorta enlargement. Examination has been performed in 16 patients, employing a 0.5 T superconductive unit, and acquiring images on axial, sagittal and coronal planes with 7 mm slice thickness. In 15 cases it was possible to detect the pathology and to characterize it according to type, location and extension. In 1 case it was no possible to make an accurate diagnosis for the presence of movement artefacts, due to poor patient's cooperation. In dissecting aneurysms the true and false lumen may be differentiated, with a good visualization of the intimal flap. The relation between the origin of the aortic branches and the aneurysm may also be ascertained.

Magnetic resonance imaging of abdominal aortic grafts

The widespread use of abdominal aortic grafting procedures and increasing awareness of related complications suggests the need for a reliable and non-invasive diagnostic technique which will allow early detection of both occlusive and non-occlusive complications. Ultrasound is generally used with satisfactory results, but has several limitations, whereas MRI has shown great promise in the study of cardiovascular disease, being non-invasive, multiplanar and multiparametric. The present research aims to evaluate MRI in the follow-up of abdominal aortic grafts, attempting to define its significance as a screening procedure in non-selected patients. MRI is reliable in ascertaining the normality of the graft as well as the complications, these being partial or total thrombosis, pseudoaneurysms and perigraft collections. The data obtained are highly satisfactory and are almost always superior to those achieved with ultrasound and CT.

[Magnetic resonance in the characterization of atherosclerotic lesions]

Fifty-one patients with occlusive and dilating vascular diseases were evaluated with MR imaging, using T1 and T2-weighted sequences and an 0.5 T superconducting magnet. Atheromatous plaques were detected in the carotids and on the aortic walls. Fatty lesions had high signal intensity on T1-weighted sequences and could be well distinguished from older thrombotic depositions which presented with medium signal intensity on T1-weighted scans and low signal on T2-weighted images. Thrombotic depositions in aneurysmal dilatation of the aorta and carotid arteries could be distinguished from patent internal lumen; inside them, areas of different signal intensity were demonstrated, which were related to the paramagnetic effect of hemoglobin degradation products (hemosiderin and methemoglobin).

[Pseudoaneurysm of the superficial femoral artery diagnosed preoperatively by magnetic resonance]

A case of pseudoaneurysm of the superficial femoral artery identified preoperatively by Magnetic Resonance is reported. The number of different parameters and planes covered by the technique permitted an accurate assessment of the site, extent, internal conformation and staging of the thrombotic deposits inside the pseudoaneurysm itself.

[Abdominal aortic aneurysms. Comparison of magnetic resonance, ultrasound, CT x-ray and angiography]

Twenty-four cases of abdominal aortic aneurysm were studied by means of MR Imaging, Computed Tomography (CT), Ultrasound (US) and Angiography. MR Imaging gave detailed information on the site and extension of the aneurysm. The extent of branches involvement, the presence of thrombosis, and the adjacent structures were also demonstrated. Major limitations of angiography were its morbility, and the difficult/impossible demonstration of eventual thrombi, and of the adjacent structures. CT, although extremely valuable in emergency cases and in the detection of calcifications, provided insufficient information on the involvement of the vessels originating from the aorta. US proved useful in the screening of abdominal aortic aneurysms, but lacked both the accuracy and the reliability necessary to a complete preoperative evaluation. MR Imaging proves thus to be a good investigation technique for a complete assessment of aneurysmatic lesions. Its major limitation is its inability to detect calcifications, while its major advantages are the accurate demonstration of both blood flow and eventual thrombi, and the multiplanarity and non-invasiveness of the methodology.

[Magnetic resonance study of renal function. Preliminary evaluation]

The amount of functioning renal parenchyma can be estimated by MRI by considering the ratio between the mean intensities of cortical and medullar zones of the kidney. Fifty-six patients and 5 healthy volunteers were studied by MRI in our department. Scanning was performed with a superconductive magnet system operating at 0.5 Tesla. Pulse sequence was Spin-Echo with TR 300/TE 30 ms. The cortico-medullary ratio (CMR) and differentiation (CMD) were standardized and related with creatine blood levels. CMR data ranged from 1.05 to 3.00, while CMD data ranged from 0.04 to 0.50. High values (good cortico-medullary contrast) were observed in subjects with normal renal function. Patients with renal diseases had low CMR and CMD, proportionally to the degree of renal failure, as proved by laboratory findings. Our preliminary study seems to demonstrate that MRI is an useful technique in the follow-up of patients with chronic renal disease.