Biomedical subjects

M Cova

Publications and source records attributed to M Cova.

At least 37 records · Page 2Linked to original sources

PubMed1996

Investigation of laminar appearance of articular cartilage by means of magnetic resonance microscopy.

Magnetic resonance (MR) images and relaxation and diffusion maps of articular cartilage were obtained to explain discrepancies in its MR appearance. Porcine specimens were studied only by MR microscopy. For human specimens a combination of MR microscopy and large-scale MR imaging was used. Common features in the laminar structures of human and porcine samples are described. It was found that the decay of transverse magnetization was nonexponential with a rapidly decaying component which prevented construction of reliable proton-density maps. Dependence of T2 values on the orientation of specimens in the magnetic field as well as magnetization transfer experiments supported the previous suggestions about a significant role of dipolar interaction with protons of collagen in the laminar appearance of articular cartilage. The loss of the laminar structure induced by rotation of the human cartilage specimen around the axis normal to its surface demonstrated nonuniform angular distribution of the collagen fibers within the layer.

Animals↗

PubMed1996

Dose effect of nitrendipine on urinary enzymes and microproteins following non-ionic radiocontrast administration.

BACKGROUND: Although calcium-channel antagonists have been proposed as prophylaxis to prevent radiocontrast-induced nephropathy, the dose and dose interval to achieve a protective effect have not been quantified in humans. METHODS: In a randomized, double-blind protocol we studied urinary enzyme and microprotein excretion in 121 outpatients (mean age 65.3 +/- 9.3 years, 62% male) with normal renal function who were to undergo digital subtraction arteriography with iohexol or iopentol. The subjects were treated with a single dose of placebo (group 1) or nitrendipine 10 mg (group 2) or 20 mg (group 3) p.o. 1 h before the procedure. Blood and urine samples were collected 1 h before, 1 h after, and 24 h after contrast administration. Study variables included contrast volume and serum creatinine, and urinary creatinine, osmolality, albumin, alanylamino-peptidase (AAP, a brush border enzyme), N-acetyl-beta-glucosaminidase (NAG, a lysosomal enzyme), and alpha-1-microglobulin (alpha-1-micro, a filtered microprotein). RESULTS: Serum values of creatinine remained unchanged during the study period. Albuminuria was not affected by contrast administration, whereas AAP, NAG, and alpha-1-micro increased significantly, all except AAP returning to baseline at 24 h. Pretreatment with nitrendipine did not reduce enzyme excretion, although AAP levels were lower in general in the group assigned to the 20-mg dose. Acute renal failure, defined as a 50% increase of serum creatinine 24 h after radiocontrast administration, was found in eight patients: four from group 1 (8.3%), three from group 2 (6.5%), and one from group 3 (3.7%). CONCLUSIONS: Neither the course of enzyme excretion nor the incidence of acute renal failure following radiocontrast administration were affected by single doses of calcium antagonists. AAP levels were lower in general in subjects taking the 20-mg dose of nitrendipine. This study also indicates that a single low or normal dose of nitrendipine per os is not effective prophylaxis before radiocontrast administration. The designs of future studies investigating the "nephroprotective' effect of calcium-channel antagonists per os should incorporate (1) the use of repeated doses to saturate hepatic metabolic pathways, and (2) the control of confounding variables in the measurement of urinary enzymes.

Acetylglucosaminidase↗

PubMed1996

[Magnetic resonance assessment of knee joint hyaline cartilage according to age, sex, and body weight].

To study the MR appearance of knee joint hyaline cartilage, 120 subjects were examined with MRI of the knee. Axial SE proton-density (PD) and T2, GE T1 and GE-MTC sequences were used, as well as coronal SE T1 and sagittal SE PD and T2 sequences. At the patellar and femorotibial cartilages the following variables were investigated: thickness, surface, signal intensity and visibility. Moreover, the three patellar sequences were compared qualitatively, by giving a 1-to-4 score to the images, depending on their yield in the four variables. As for articular cartilage thickness, a statistically significant difference was found between men and women in nearly all measurement sites, the mean values being always higher in men. A statistically significant inverse correlation between cartilage thickness and age was found, in men only, at the three load-bearing regions of the medial femoral condyle. Cartilage surface was irregular and/or its signal intensity altered in 28% of patients at the femoral condyles, while the cartilage of tibial plates exhibited normal surface and homogeneous signal intensity in most cases. The visibility rate of trilaminar cartilage was 82.5% for the medial femoral condyle, 87.5% for the lateral femoral condyle, 70% for the patella, 12.5% for the medial tibial plateau and 14.5% for the lateral tibial plateau. No statistically significant correlation was found between cartilage thickness, surface, signal intensity and visibility and age, sex, and body weight. The GE sequence was the best tool to study cartilage thickness and signal intensity, while the SE T2 sequence was the most accurate one to depict the articular surface and, together with the PD SE sequence, to visualize the trilaminar structure. Our study suggests that articular cartilage surface, thickness, and signal intensity can be studied accurately with SE PD and T2 sequences, combined with a GE T1 sequence.

Adolescent↗

PubMed1995

Pulmonary nodules: improved detection with vascular segmentation and extraction with spiral CT. Work in progress.

PURPOSE: To determine whether extraction of pulmonary vessels from computed tomographic (CT) images with automated segmentation improves the detection of pulmonary nodules. MATERIALS AND METHODS: Simulated nodules were superimposed on normal spiral CT images. Eight patients referred for CT assessment of pulmonary nodules were selected for clinical evaluation. Vessels were extracted from both the simulation and clinical study with a three dimensional seeded region-growing algorithm. Three experienced radiologists were asked to locate the nodules and assign a level of confidence to their findings. Sensitivity and proportion of false-positive results per case (FPC) were calculated. Observer performance was evaluated by alternate free-response receiver operating characteristic analysis. RESULTS: Extraction of vascular structures from CT scans improved sensitivity from 63% to 84% in the simulation study and from 58% to 78% in the clinical study. The proportion of FPC decreased from 52% to 24% and from 55% to 12%, respectively. Radiologists performed consistently better with the segmented images than with the original images in both the simulation (P = .006) and the clinical (P = .0013) study. CONCLUSION: Automated vessel subtraction and extraction improves detection of pulmonary nodules.

Adult↗

PubMed1995

[Magnetic resonance of tibiotalar and subtalar joints. Normal anatomy].

Fifty-three ankles of 29 normal volunteers were examined with Magnetic Resonance Imaging (MRI) to improve the anatomical MR knowledge of tibiotalar and subtalar joints. The aim of our study was therefore to assess the visibility of articular cartilages, tendons and ligaments of the ankle and to define the best scan plane for their visualization. MR studies were performed with SE T1-weighted sequences on the sagittal, coronal and axial planes. The visibility of articular cartilages was 70.8% for the tibiotalar joint and 56.3% for the subtalar joint. All ankle tendons and four of the eight ankle ligaments considered in our study were assessed, at least on one of the sagittal, coronal or axial planes, with over 70% visibility. The deltoid ligament was detected in 95% of the cases on coronal images, the anterior and the posterior talofibular ligaments were seen respectively in 82% and in 75% of the cases on axial images, while the interosseous ligament was detected in 87.5% of the cases on sagittal images. Our study assessed both the capabilities and the limitations of MRI in the detection of anatomical structures of the tibiotalar and subtalar joints and defined the best scan plane for their visualization.

Achilles Tendon↗

PubMed1994

[Magnetic resonance of the cartilages of the large joints].

MRI of the articular cartilage requires a careful technical approach since this structure is very thin, with a peculiar internal architecture between the supporting matrix and the cell component. On MR images the normal articular cartilage has a zonal appearance. To optimize the variables for best visualization of the internal architecture of the hyaline articular cartilage, an ex vivo and in vivo study was carried out. Accurate T1 and T2 relaxation times of the articular cartilage were obtained with a particular mixed sequence and then used to create isocontrast intensity graphs. The latter allowed, in all pulse sequences (SE and GRE), the best combination of TR, TE and FA to optimize signal differences between cartilage areas. A trilaminar pattern was demonstrated, with a superficial and a deep hypointense areas, in all sequences, together with an intermediate area which was moderately hyperintense on SE images and markedly hyperintense on GRE images. In the current literature, MRI appears to have been widely used to investigate hyaline cartilage conditions. In many series, the technique proved its efficacy in assessing both acute (traumatic cartilage fractures, osteochondritis dissecans, arthritis) and chronic (arthrosis, chondromalacia patellae, Hoffa's disease, synovial plica syndrome) conditions of the articular cartilage. T2-weighted sequences (both SE and GRE) are widely known as the most accurate in assessing cartilage conditions, which depends mainly on the arthrographic effect of synovial fluid on T2-weighted images. Of late, also MR arthrography, especially MR arthrography after the i.v. administration of Gadolinium, has emerged as an outstanding technique to investigate articular cartilage conditions. On the basis of MR arthrography findings, some authors suggested a classification of osteochondritis dissecans, arthrosis and chondromalacia patellae on MR images. MR stages seem to be closely correlated with the histologic classification suggested for these conditions.

Cartilage Diseases↗

PubMed1994

[Thin-section computerized tomography of the kidney in the differential diagnosis of small tumor and cystic hypodensities].

Small hypodense renal lesions with a round shape are frequently detected on CT scans of the upper abdomen after contrast medium administration. In nearly all cases these round hypodensities are simple small cysts with no clinical significance. However, the fluid density of these cysts cannot be always defined, due to the partial volume averaging which occurs on CT when 10-mm-thick slices and contrast enhancement are used. Therefore, a malignant tumor--i.e., small renal tumors or metastatic lesions--cannot be ruled out in some cases. Since the limitations of CT are related to partial volume averaging, the authors used both 5-mm and 10-mm slices to reduce this artifact. Forty-eight small hypodensities (< 15 mm) were studied after contrast agent administration: 42 of them were simple cysts and 5 were tumoral lesions--i.e., 3 renal cell carcinomas and 2 lymphomatous lesions. The results showed that, with 5-mm slices, the density of the fluid hypodensities decreased in nearly all cases and in 81.3% of cases it was below 30 HU. The difference in densities between 10-mm and 5-mm slices was about 50 HU (75 +/- 30 to 21 +/- 16 HU). In the 5 tumoral hypodensities, lesion density was still in the soft tissue range also with 5-mm slices, with no major decrease. These results show that this technique is simple and effective in the differential diagnosis of small renal hypodensities since it requires only a short additional examination time.

Adult↗

PubMed1993

[Renal angiomyolipomas: atypical aspects in ultrasonography and computerized tomography].

As a rule, renal angiomyolipomas (AML) present with characteristic patterns on US and CT images. However, in a limited number of cases US and CT findings are atypical, so that no diagnosis can be made on their basis. The authors reviewed their personal series of renal tumors and now report the US and CT findings of 5 cases with atypical features on one or both examinations. Two patients had hyperechoic lesions with typical AML patterns, but no fatty densities were visible with CT. Both patients underwent surgery and histology which showed two AMLs with muscular and vascular components and very few fatty cells. Two cases were observed in patients with Bourneville disease. Even though the cases exhibited atypical features on US and CT images, the diagnosis was suspected on the basis of the well-known association of tuberous sclerosis with AML. One case presented with a complex cystic mass on US; CT showed a bleeding tumor. Even though no unquestionable diagnosis of AML could be made in this case, the hypothesis of a bleeding AML was considered in the differential diagnosis. Such atypical imaging features were related to low fatty content inside the lesion and to bleeding complications. Absent/low fatty component represented a cause of atypical lesion appearance on CT which showed a mass with soft-tissue density which could not be differentiated from a solid tumor. In these cases, AMLs remained typically hyperechoic on US images. Bleeding represented a cause of error mainly on US since the typical hyperechoic pattern was replaced by a iso-hypoechoic pattern. CT is helpful in these cases because it shows both the bleeding and possible low-density fatty areas.

Adult↗

PubMed1993

[Comparative evaluation of the SPIR sequence with gadolinium and other sequences in bone diseases].

In order to assess the value of the SPIR (Spectral Presaturation with Inversion Recovery) sequence (a fat-suppression technique) with Gd-DTPA in the investigation of skeletal diseases, 50 patients were examined with conventional SE T1- and T2-weighted sequences, as well as with SE T1 and SPIR sequences after the i.v. injection of Gd-DTPA. Twenty patients were affected with a skeletal infection (11 spondylodiscites and 9 osteomyelitis) and 5 with a primary tumor; 15 had metastases and 10 a hemolymphopoietic disorder (6 myelomas and 4 non-Hodgkin's lymphomas). In the four groups of patients, the mean visibility of skeletal lesions was higher on SPIR images with Gd-DTPA than on the other images, even though a statistically significant difference was observed only in the group of infections (p < 0.002) and in myelomas and lymphomas (p < 0.001). In 13 cases with extraosseous spread, visibility was higher on contrast-SPIR images than on the other sequences, even though high sensitivity was also exhibited by SE T2-weighted sequences. Even though the SPIR sequence still exhibits some technical limitations, our study assesses the value of this sequences with Gd-DTPA in the investigation of skeletal lesions. The major advantages of contrast-SPIR imaging follow: 1) it shows skeletal lesions, which are isointense on enhanced SE T1-weighted images, 2) it provides better visibility of the lesion than the other sequences, more accurately defining their borders, 3) it provides better anatomical detailing than SE T2-weighted images and 4) its sensitivity is higher.

Adult↗

PubMed1992

Evaluation of marrow perfusion in the femoral head by dynamic magnetic resonance imaging. Effect of venous occlusion in a dog model.

RATIONALE AND OBJECTIVES: There is a continuing need for a greater sensitivity of magnetic resonance imaging (MRI) in the diagnosis of avascular necrosis (AVN). Previously, it was demonstrated that a dynamic MRI method, with gadolinium-DTPA (Gd-DTPA) enhancement, can detect acute changes not seen on spin-echo images after arterial occlusion in a dog model. Because venous congestion appears to be a more directly relevant hemodynamic abnormality in a majority of clinical AVN cases, the authors extended the dynamic MRI technique to study changes in venous occlusion. METHODS: Dynamic MRI of the proximal femur was performed in five adult dogs before and after unilateral ligation of common iliac and lateral circumflex veins. Sixteen sequential gradient-recalled pulse sequence (GRASS) images (time resolution = 45 mseconds, echo time = 9 mseconds, flip angle = 65 degrees) were obtained immediately after a bolus intravenous injection of 0.2 mmol/kg of Gd-DTPA. Simultaneous measurements of regional blood flow were made using the radioactive microsphere method. RESULTS: After venous ligation, there was a 25% to 45% decrease in the degree of enhancement compared with preligation values on the ligated side. The decrease in cumulative enhancement (integrated over the entire time course) was statistically significant. The occlusion technique was verified by confirming a statistically significant decrease in blood flow determined by the microsphere method. CONCLUSIONS: Dynamic Gd-DTPA-enhanced fast MRI technique can detect acute changes in bone marrow perfusion due to venous occlusion. This technique may have applications in the early detection of nontraumatic AVN.

Animals↗

PubMed1991

Avascular necrosis of bone in children undergoing allogeneic bone marrow transplantation.

Avascular necrosis of bone (AVNB) is reported in two children after allogeneic bone marrow transplantation. Preparation therapy for transplantation included cyclophosphamide and total body irradiation. Corticosteroids, cyclosporine A, and methotrexate were used for graft-versus-host-disease prophylaxis. The possible role of combination therapy in development of AVNB is discussed, but a direct relationship with single agents was not found. However, an early diagnosis is important to institute conservative treatment and prevent irreversible damage to affected joints. Magnetic resonance imaging was found to be more sensitive than plain radiography in early detection of AVNB.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1991

Bone marrow perfusion evaluated with gadolinium-enhanced dynamic fast MR imaging in a dog model.

The authors studied, in a dog model, the feasibility of using gadolinium-enhanced dynamic magnetic resonance (MR) imaging to noninvasively monitor bone marrow perfusion of the proximal femur. With a gradient-recalled acquisition, sequential images of 10 hips in five healthy dogs were obtained for 14 minutes after an intravenous bolus injection of 0.2 mmol of gadopentetate dimeglumine per kilogram. The study was repeated after unilateral arterial embolization of major femoral vessels. Radiolabeled microspheres were injected before and after vessel occlusion. After unilateral embolization, statistically significant differences in enhancement were observed between embolized and control sides (eg, 31% vs 83% average peak enhancement in the femoral neck). There was a high correlation (r = .81 [average]) between the MR data and the microsphere blood flow measurements. The postembolization data indicate that contrast-enhanced fast MR imaging may allow early detection of abnormal bone marrow flow. This technique may be valuable in evaluating patients at risk for avascular necrosis of the femoral head, especially in posttraumatic cases.

Animals↗

PubMed1991

[The contribution of gadolinium to the magnetic resonance diagnosis of spondylodiscitis].

To determine the contribution of Gd-DTPA to the evaluation of vertebral infections 16 MR examinations with i.v. Gd-DTPA injection were performed on 12 patients with diagnosis of spondylodiscitis. All patients were examined with both SE T1- and SE T2-weighted sequences. The SE T1-weighted sequence was repeated following i.v. Gd-DTPA injection (0.1 nmol/kg). Signal intensities and visibility of the lesions were evaluated with MR. For each lesion the grade of visibility on SE T1-weighted sequence was compared with the grade of visibility on SE T2-weighted sequence. Moreover, for each study the information obtained by the combined evaluation of SE T1-weighted sequence without and with Gd-DTPA was compared with the information obtained by combined SE T1- and SE T2-weighted sequences. Gd-DTPA was useful in the evaluation of lesions of the discal space, showing in all cases an area of low signal intensity with peripheral enhancement; this finding allowed, in some cases, to differentiate mild spondylodiscitis from degenerative features. Gd-DTPA was also very useful in determining the extent of the disease: in comparison with MR study without contrast media, the combined evaluation of SE T1-weighted sequence without and with Gd-DTPA better showed the extent of the disease in 7/8 cases (88%).

Adult↗

PubMed1990

Normal age-related patterns of cellular and fatty bone marrow distribution in the axial skeleton: MR imaging study.

Knowledge of age-related distribution patterns of cellular and fatty marrow is critical to the interpretation of magnetic resonance (MR) imaging studies. To determine such patterns, the authors retrospectively evaluated 70 examinations each of the skull, cervical spine, thoracic spine, lumbar spine, pelvis, and proximal femur (420 examinations) in patients without known bone marrow abnormality who ranged in age from 6 months to older than 70 years. Two to four distinct patterns were identified in each anatomic area on spin-echo images obtained with a short repetition time and a short echo time. The relative frequency of the patterns for different age groups is consistent with the known physiologic conversion from cellular to fatty marrow with advancing age. Knowledge of these patterns should help in the interpretation of MR images of the axial skeleton.

Adult↗

PubMed1990

[Magnetic resonance in the diagnosis of bone infections].

Skeletal infections represent a variety of clinical and pathological conditions in which both an early diagnosis and the precise evaluation of disease extent are very important in planning proper therapy. To determine MRI capabilities and limitations in the evaluation of skeletal infections 21 patients--12 with a clinical diagnosis of osteomyelitis of the lower limbs and 9 with a clinical diagnosis of spondyloscitis--were studied with this technique. All patients were examined with conventional X-rays; conventional tomography was performed in 3 cases, and CT in 6. Signal intensities and morphological aspects were then evaluated with MRI. MRI diagnoses were compared with surgical findings or clinical follow-up, after antibiotic therapy: 19 true-positives were observed, together with 1 true-negative, 1 false-positive, and no false-negatives. MRI findings were correlated with those of conventional radiology: MRI identified the lesions and their nature in 100% of cases, whereas conventional radiology did the same in 85% of cases; in 50% of cases only the latter was able to define the nature of the process. Four patients underwent MRI follow-up. MRI was highly sensitive in determining the presence of lesions in an early stage and in demonstrating lesion regression. Moreover, MRI was able to identify the complications occurring in some cases of osteomyelitis and spondyloscitis. In all cases MRI allowed the extent of the disease to be accurately determined and, in osteomyelitis of the lower limbs, it was extremely useful to differentiate soft-tissue infections from bone marrow involvement.

Adolescent↗

PubMed1990

[Magnetic resonance of the bone marrow].

Magnetic resonance imaging has opened new possibilities to current diagnostic radiology in the evaluation of bone marrow. In the past, bone marrow imaging was based on conventional radiology, nuclear medicine and computed tomography; they all exhibited some capabilities but also some limitations. Bone image on MR scans is due to bone marrow, with its different components of red and yellow marrow. Since red marrow is mostly liquid and yellow marrow contains large amounts of fat, the signal will vary, on T1-weighted images, according to their different proportions. There is a gradual change from red marrow to yellow marrow from birth to adulthood: this change determines the MR appearance of bone marrow, the different features of which should be known for a correct evaluation of pathologic findings. MRI is extremely effective in the evaluation of infiltrative disorders of bone marrow, such as leukemia, lymphoma, myeloma, primary and metastatic skeletal tumors, and infections. MRI allows depletive disorders of bone marrow and ischemic processes to be studied. Finally, MRI allows the non-invasive follow up of bone marrow pathologic conditions, thus representing a valid alternative to biopsy.

Bone Marrow↗

PubMed1984

[Autoantibodies and respiratory allergy: immunologic case study].

Sera obtained from 212 patients with rhinopathy and/or asthma of allergic origin (pollens and/or mites) and from 87 apparently healthy controls were studied for the presence of organ and non organ specific autoantibodies. These were determined by indirect immunofluorescence techniques (5) using test tissue from monkeys (thyroid) and rats (stomach, liver and kidney). Two groups were matched for age and sex and the tests were performed using the double-blind method. The incidence observed was not dissimilar to that detected in healthy subjects, with the exclusion of smooth-muscle antibodies. These were present to a lesser extent in patients with respiratory allergies (0.94%) in contrast with the incidence of 5.73% in normal subjects (P less than 0.01). On the basis of our findings, it seems possible to hypothesize that allergic patients have a lesser tendency to autoimmune diseases because the immune system is committed to the IgE-mediated immunoreactions. In conclusion, autoantibodies do not seem to play a role in the pathogenesis of respiratory allergies to inhaled allergens.

Adult↗

PubMedDate not supplied

Value of magnetic resonance imaging in the evaluation of sex-reassignment surgery in male-to-female transsexuals.

BACKGROUND: We investigated the value of magnetic resonance imaging (MRI) in the evaluation of sex-reassignment surgery in male-to-female transsexual patients. METHODS: Ten male-to-female transsexual patients who underwent sex-reassignment surgery with inversion of combined penile and scrotal skin flaps for vaginoplasty were examined after surgery with MRI. Turbo spin-echo T2-weighted and spin-echo T1-weighted images were obtained in sagittal, coronal, and axial planes with a 1.5-T superconductive magnet. Images were acquired with and without an inflatable silicon vaginal tutor. The following parameters were evaluated: neovaginal depth, neovaginal inclination in the sagittal plane, presence of remnants of the corpus spongiosum and corpora cavernosa, and thickness of the rectovaginal septum. RESULTS: The average neovaginal depth was 7.9 cm (range = 5-10 cm). The neovagina had a correct oblique inclination in the sagittal plane in four patients, no inclination in five, and an incorrect inclination in one. In seven patients, MRI showed remnants of the corpora cavernosa and/or of the corpus spongiosum; in three patients, no remnants were detected. The average thickness of the rectovaginal septum was 4 mm (range = 3-6 mm). CONCLUSION: MRI allows a detailed assessment of the pelvic anatomy after genital reconfiguration and provides information that can help the surgeon to adopt the most correct surgical approach.

Adult↗