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Biomedical subjects

M Midiri

Publications and source records attributed to M Midiri.

At least 55 records · Page 3Linked to original sources
PubMed1998

Image quality control in breast ultrasound.

Sonography is well suited for breast studies. Adequate equipment is needed to acquire high quality images because several technical factors influence ultrasound images. Thus, the use of high frequency dynamic scanning probes, the ultrasound beam focusing corrected for the near field, the adjustment of the gain and image contrast may all interfere with ultrasound beam reflection and scattering, determined by the heterogeneity of the gland parenchyma. In the last few years, a line of ultrasound equipment dedicated to this kind of application has been developed with 'small parts' transducers and frequencies ranging 10-13 MHz. These units can improve the evaluation of superficial structures and provide diagnostic results that conventional equipment cannot achieve. The higher the quality, the more a sonographic image corresponds to real anatomy. This capability depends on the different kinds of system resolution. Axial spatial resolution is the capability to resolve discrete structures along the beam axis. Pulse length is inversely proportional to frequency and thus, the higher the transducer frequency, the better the axial resolution. However, the increase in frequency reduces the depth of penetration of the ultrasound beam. The spectrum of frequencies emitted by the crystal has been recently modified in order to obtain a good trade-off between the beam resolution and its penetration. Indeed, the development of the multifrequency technology allowed to improve the near field resolution while retaining a good penetration into the distant field. Furthermore, the use of compound ceramics with a broad bandwidth helps Doppler analysis because flow studies are optimized by low frequencies, whereas two-dimensional morphologic imaging is optimized by high frequencies. Lateral spatial resolution is the capability to resolve discrete structures perpendicular or lateral to the beam axis. This parameter strictly depends on the size of the ultrasound beam section and it is optimal only in the focal area. Therefore, it improves with narrow beams. Several transducers are available in breast sonography, but the most adequate one is currently the annular transducer. The equipment should be able to detect even slight differences in acoustic impedance between the several breast tissues. This may be obtained by optimizing the dynamic range and the pre- and postprocessing setting. Apart from equipment, two other technical factors should be optimized to obtain high quality images, namely beam intensity and gain curve. A new Doppler technique has been recently introduced: power Doppler, which allows the demonstration of breast nodule vascularization with higher sensitivity than color Doppler. Finally, a rigorous examination technique is required to obtain high quality images. In the last few years, several quality assurance programs have been introduced. Dedicated phantoms are generally used. Recently, computer systems have been also developed.

Breast Diseases↗
PubMed1998

[The heart of the patient with beta thalassemia major. Study with magnetic resonance].

PURPOSE: The main cause of death in beta-thalassemia major patients is congestive heart failure which is traditionally referred to myocardial iron overload. Recently, some investigators have found that cardiac failure is not caused by the iron overload. In their opinion, left-sided heart failure develops years after the onset of acute myocarditis and might be related to a late autoimmune process. Right-sided heart failure is related to the combination of left ventricular diastolic restriction and pulmonary hypertension. The aim of this work is to study myocardial iron overload by MRI and to correlate the signal intensity changes of the myocardium with cardiac function. MATERIAL AND METHODS: Sixteen patients with beta-thalassemia major were examined with a .5 super-conducting unit. SE and cine-GE sequences were used in the 4 chamber and 2 chamber views. Left ventirclar ejection fraction (EF) was calculated by using the biplane area-length method. Right ventricular size was assessed by measuring the end-diastolic anteroposterior diameter (APD). Myocardial signal intensity was evaluated qualitatively and quantitatively (myocardium/subcutaneous fat) in all the beta-thalassemia patients and in 10 normal volunteers. RESULTS: Left ventricular function was decreased (EF < 55%) in 2/16 patients. The right ventricle was dilated in 5/16 patients (APD > 42 mm). The myocardium had a lower signal intensity than that of normal volunteers in 15/16 patients. No statistical correlation was found between myocardial signal intensity and serum ferritine levels or cardiac function. CONCLUSIONS: The small number of patients in our series does not allow any definitive statements. However, our results show that cardiac function is not influenced by myocardial iron overload.

Adolescent↗
PubMed1998

[The assessment of skin tumors with magnetic resonance with high resolution and a paramagnetic contrast medium].

INTRODUCTION: The technologic improvement of surface coils in MRI has allowed better visualization of the skin and thus permitted the clinical use of this technique in dermatology. MRI allows to assess the depth and extent of skin tumors and to detect any malignant transformation. The MR differentiation between benign and malignant skin lesions relies on morphological criteria which however do not have an absolute diagnostic value. We investigated the role of paramagnetic contrast agents in the differentiation between benign and malignant skin lesions. MATERIAL AND METHODS: Forty-one patients, 33 with benign and 8 with malignant skin tumors, were submitted to MRI. All the examinations were performed with a 1.5 T superconductive unit, with a 2.5 cm surface coil. Axial T1- and T2-weighted SE images were acquired with 2 mm slice thickness. Paramagnetic contrast material was administered to all patients. The signal intensity of the skin lesions was calculated before and after paramagnetic contrast agent administration positioning a region of interest. A percentage ratio of contrast enhancement was calculated to quantify contrast agent uptake and the relative values were compared between benign and malignant lesions. A qualitative analysis was also performed rating the contrast enhancement of each lesion as high, intermediate, or absent. RESULTS: The quantitative analysis showed a statistically significant difference (p < .5) between the contrast enhancement values of benign and malignant lesions. In particular, malignancies had values ranging 117.3 (+/- 28.7) to 125 (+/- 32.4), while benign lesions had -20.6 to 99.8 (+/- 21.1). Conversely, no difference in contrast enhancement was found at qualitative analysis. CONCLUSIONS: MRI is a promising tool for characterizing skin tumors. Our preliminary results should be confirmed on larger series of patients with the use of high temporal resolution imaging sequences.

Adolescent↗
PubMed1998

[Focal liver lesions. A comparison between magnetic resonance under base conditions and after a superparamagentic contrast medium].

INTRODUCTION: Superparamagnetic iron oxide (Spio) is a negative contrast material which is phagocytosed by reticuloendothelial cells. It significantly decreases the signal intensity of the organs where it is taken up selectively, especially on T2-weighted images. According to previous reports, it improves the visualization of focal liver lesions with(out) a low content of Kupffer's cells. We investigated the yield of Spio-enhanced MRI in the detection and characterization of focal liver lesions. MATERIALS AND METHODS: Eighteen patients underwent MRI before and after the administration of Spio particles. T1, PD, T2 SE and T2* GE images were acquired with a .5 T superconductive unit. The Spio dose was .075 mL/kg which was administered i.v. in 35-45 minutes' infusions. Images were acquired about 30-90 minutes after the end of administration. Scanning was repeated in one patient about 8 hours after the end of Spio administration. RESULTS: Baseline MRI showed hepatocellular carcinoma (HCC) in 10 patients, metastases in 4, 1 dysplastic lesion, 1 single and 1 multiple hemangioma, 1 focal nodular hyperplasia (FNH) and 1 intrahepatic cholangiocarcinoma. No lesion was detected in one patient. Spio-enhanced MRI detected 7 more lesions that baseline MRI, with 11.47% sensitivity improvement. Moreover, Spio-enhanced MRI detected more lesions that baseline MRI in 5/18 patients (27.78%). PD/T2 SE images were the most sensitive ones, followed by T2* GE and finally by T1 SE. Nearly all HCC nodules (17/18), all metastatic lesions and the cholangiocarcinoma did not take up iron oxide and were relatively hyperintense to the liver. However, in one well-differentiated HCC, the nodule partially took up the contrast agent and became isointense, with high-signal borders on PD/T2 SE images. Both the dysplastic lesion and FNH took up iron oxide; the former was isointense to the liver, while the latter appeared slightly hyperintense, with a high-signal central scar. Finally, hemangiomas became hyperintense on Spio-enhanced T1 SE images and had slightly decreased signal intensity on Spio-enhanced T2 SE images. CONCLUSIONS: In our experience iron oxide was an effective contrast material. Spio-enhanced MRI improved the detection and characterization of focal liver lesions relative to baseline MRI. Several liver-specific contrast agents are now available or in an advanced experimental stage. Therefore, future studies could be aimed at assessing the effectiveness of iron oxide versus other contrast agents and at establishing the role of Spio-enhanced MRI versus spiral CT and CT during arterial portography.

Adult↗
PubMed1998

[Magnetic resonance imaging of seronegative sacroiliitis].

INTRODUCTION: The inflammatory involvement of the sacroiliac joint is frequent during seronegative spondylarthritis. The clinical diagnosis of sacroiliitis may be very difficult, especially in the early stage, because joint motion cannot be assessed directly and the clinical picture is very similar to that of lumbar pain. Conventional radiography is negative as long as the structural change in the joint is limited to the synovial membrane and the cartilage (early stage). Computed Tomography (CT) also has many drawbacks, and thus the changes can be shown only when chondritis and enthesitis have already damaged the bone. The disease onset is usually preceded by a long latency; early diagnosis is needed for a proper and timely treatment, which can be made only with a highly sensitive and specific technique. We investigated the diagnostic accuracy of MRI in the early detection of sacroiliitis during seronegative spondylarthritis. MATERIAL AND METHODS: Forty patients with suspected sacroiliitis and negative radiographic findings were submitted to MRI; thirty-seven of them were HLA B27 positive. MRI was performed with a .5 T superconducting unit; T1-weighted SE, T2-weighted FSE, T2* GE, and STIR images were acquired on the oblique coronal plane parallel to the anterior sacrum. Ten asymptomatic volunteers were also examined as a control group. RESULTS: An irregular sacral border and marrow changes at the insertion of the sacroiliac ligaments were seen in 3/10 asymptomatic volunteers. MRI was negative in 7/40 patients, while the synovial compartment was replaced by some tissue with low signal intensity of T1 and high signal on T2 in the other 33 patients; this finding was referred to synovial pannus. Persisting low-signal foci were seen in the synovial compartment in 16/33 patients, which were referred to spared cartilage. High-signal regions were depicted at the bone periphery in 9/33 patients, which areas were consistent with bone erosion; the subchondral bone was markedly hypointense in 5 of these patients, indicating sclerosis. Finally, diffuse high signal intensity was found in the bone marrow in 3/33 patients and referred to infectious sacroiliitis. CONCLUSIONS: MRI appears the method of choice for the early detection of seronegative sacroiliitis because it can show the early changes in cartilage and subchondral bone, filling the gap between the onset of symptoms and radiographic evidence. Moreover, MRI uses no ionizing radiations and makes therefore a precious tool for the diagnosis and follow-up of young patients, hopefully decreasing the use of CT which however provides better detailing of bone and bone degeneration.

Arthritis↗
PubMed1997

Magnetic resonance findings in scuba diving-related spinal cord decompression sickness.

Scuba diving is associated with risk of severe decompression sickness (DCS type II), which results from rapid reduction of the environmental pressure sufficient to cause the formation into tissue or blood of inert gas bubbles previously loaded within tissues as a soluble phase. DCS type II constitutes a unique subset of ischemic insults to the central nervous system (CNS) with primarily involvement of the spinal cord. Ten patients with diving-related barotrauma underwent neurologic examination. Two of them presented progressive sensory and motor loss in the extremities at admission and were presumed affected by spinal cord DCS. Magnetic resonance imaging (MRI) demonstrated abnormalities in the white-matter tracts of the spinal cord in these patients, in each case corresponding to an area of the cord believed to be clinically involved. After a course of therapeutic recompressions, one patient was able to stand and walk a short distance, and MRI revealed a decreased extension of areas of spinal cord abnormalities. MRI has proved to be reliable in the detection of pathologic changes of spinal cord decompression sickness that were previously undetectable by other neuroimaging methods and also has proved to be useful in the follow-up during therapeutic hyperbaric recompressions.

Adolescent↗
PubMed1997

Serum and fecal pancreatic enzymes in beta-thalassemia major.

CONCLUSION: This study, using indirect tests, demonstrated that exocrine pancreatic function is impaired in a proportion of patients with beta-thalassemia major (TM), though this impairment is generally mild or moderate. BACKGROUND: Impaired structure and function of the exocrine pancreas has been reported in patients with Beta-thalassemia major. METHODS: In this study we measured fecal fats and serum and fecal pancreatic enzymes in 30 patients (13 M, 17 F) with TM, mean age 22.1 yr (range 14-39) and compared them with those of a matched group of healthy controls. Results were correlated with age, serum ferritin, blood transfusion, and various nutritional parameters. Enzymes assays included: serum pancreatic amylase (PA), lipase (L), trypsin (T), fecal chymotrypsin (FCT), and fecal elastase (FE). RESULTS: No patient was positive for steatorrhea. Comparison of the mean values showed a significant difference only for FE (p < 0.002). Using only the fecal tests as a reference, we found that 12 patients had FE values below the cutoff limit; of these, five had values between 100 and 185 micrograms/g, three between 50 and 99 micrograms/g and four below 50 micrograms/g. Ten patients had FCT values below the cutoff limit; seven presented impairment in both tests and six of them had FE values below 100 micrograms/g (including four diabetics). No correlations were found between enzyme values and mean serum ferritin values or mean blood consumption over the previous 3 yr. No correlation was found between FE and FCT levels or between enzymes and age.

Adolescent↗
PubMed1997

Blood-ocular barrier damage: use of contrast-enhanced MRI.

The blood-ocular barrier (BOB) shares similar neuroepithelial origin, microanatomy and functions with the blood-brain barrier. There are many natural (e. g. diabetes, hypertension) or iatrogenic (chemotherapy, retinal photocoagulation) conditions which can cause a BOB breakdown, resulting in visual acuity impairment or loss. The authors examined 42 patients affected by BOB damage in different pathological conditions. All patients previously underwent a conventional fluoroangiographic (FA) study. Nine patients with normal FA exam were evaluated also. Despite normal MRI findings immediately after Gd-DTPA injection, contrast leakage into the vitreous body or into the aqueous fluid was demonstrated in delayed scans (40-50 min after contrast administration), proving the existence of a BOB damage (sensitively 94 %). Although FA exam remains the choice modality in BOB breakdown demonstration, we propose MRI as a useful diagnostic tool when optic media opacity (cataract, haemovitreous, intraocular silicon oil) occurs, preventing direct retinal fundus imaging and/or an early screening tool.

Adult↗
PubMed1997

Arrhythmogenic right ventricular dysplasia: MR features.

Arrhythmogenic right ventricular dysplasia (ARVD) is a heart disease characterized by a total or partial fat replacement of the myocardium. A total of 30 patients were studied with a suspected diagnosis of ARVD. Clinical criteria used for evaluation of ARVD were: (a) ventricular origin arrhythmias with a left bundle branch block configuration, (b) T-wave inversion in the anterior precordial leads, (c) ventricular kinetic alterations observed using echocardiography and angiography and (d) cardiac failure when there are no pathologies attributable to other heart diseases. All patients had serial EKG and echocardiography tests. One third of patients underwent angiocardiography; 7 of 30 had Holter; 7 of 30 had exercise test just to evaluate the effectiveness of the anti-arrhythmic therapy. All patients underwent MRI examination. The following MRI criteria were used: (a) high-intensity areas indicating the fatty substitution of the myocardium, (b) ectasia of the right ventricular outflow tract, (c) dyskinetic bulges, (d) dilation of the right ventricle and (e) enlargement of the right atrium. The diagnosis of ARVD was classified as highly probable for patients manifesting at least three positive criteria, probable with two positive criteria, dubious with one and negative in the absence of all criteria. Highly probable diagnosis of ARVD was made in 8 patients, probable in 4, dubious in 7 and negative in 11. The MRI technique is very effective in the assessment of ARVD. The MRI criteria may be helpful in the diagnosis of this condition.

Adipose Tissue↗
PubMed1997

[Normal anatomy and pathologic features of the supraspinatus muscle: comparison between ultrasonography and surgery. Analysis of the potential sources of diagnostic errors].

The supraspinatus muscle performs about 60% of the elevation-abduction motion of the arm; therefore, it has a prominent functional role among the extrarotational muscles of the shoulder and is the most injured in subacromial space conditions. Seventy-four patients, aged 21-64 years, were examined to compare ultrasonography (US) results with surgical findings in supraspinatus conditions and to analyze the possible pitfalls in US diagnosis. All the patients underwent conventional X-ray, US and then surgery or arthroscopy. The following criteria were considered: morphology, thickness, echotexture, the convexity of the superior border of supraspinatus tendon, the relationships with the subacromial bursa and the tendon of the biceps long head, the regularity of the bone cortex of the humeral head. US showed: chronic degenerative tendinopathy in 10 patients; perforating focal injuries in 21 patients; deep focal injuries in 10 patients; intramural focal injuries in 6 patients; superficial focal injuries in 8 patients; complete tendon tear with detachment in 19 cases. 62/74 US diagnoses were surgically confirmed, with a specificity of 83.7%. In our experience, US provided very useful information about the pattern, size and site of the injuries and was very helpful in the surgical planning.

Adult↗