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Biomedical subjects

G Frija

Publications and source records attributed to G Frija.

At least 55 records · Page 3Linked to original sources
PubMed1994

MR lymphography with superparamagnetic iron nanoparticles in rats: pathologic basis for contrast enhancement.

OBJECTIVE: The purpose of this study in rodents was to determine the pathologic basis for enhancement patterns of hyperplastic and tumours lymph nodes shown by MR lymphography after IV injection of superparamagnetic iron oxide nanoparticles (AMI-227). MATERIALS AND METHODS: Hyperplastic and tumorous lymph nodes were imaged in vivo at 1.5 T 1 day after IV administration of AMI-227 (40-200 mumol Fe/kg) to rats. Inguinal and axillary lymph nodes were surgically resected, and in vitro imaging was done by using the same magnet with a prototype coil that allowed a pixel size of 70 x 230 microns. Imaging findings were correlated with histologic findings and iron staining of the nodes. RESULTS: With all sequences, at doses of 80 mumol Fe/kg or higher, the signal intensity of hyperplastic nodes was lower than on unenhanced images. The same pattern was seen in the remaining normal tissue of tumourous lymph nodes. This T2* effect was a result of clustered particles inside macrophages in the lymphatic sinuses. At doses of 200 mumol/kg, the tumor itself consistently showed an increase in signal intensity on T1-weighted images. This T1 effect probably resulted from particles leaking into the interstitial spaces of the tumor. CONCLUSION: After IV injection of superparamagnetic nanoparticles, a decrease in signal intensity indicates active uptake of particles into macrophages, whereas an increase in signal intensity indicates altered capillary permeability in tumor. These findings in rats may prove to be clinically useful in the future for differentiating benign from malignant enlarged lymph nodes.

Animals↗
PubMed1993

Superparamagnetic iron oxides as positive MR contrast agents: in vitro and in vivo evidence.

The ability of superparamagnetic iron oxides (SPIO) and ultrasmall superparamagnetic iron oxides (USPIO) to act as positive contrast enhancers due to a marked T1 relaxivity was investigated. At low concentrations, an important signal enhancement was observed in vitro, reaching 120% for SPIO and 140% for USPIO in a spin echo 500/22 sequence. The more heavily the sequence was T1-weighted the greater the enhancement. As the concentration increased, the signal dropped. The in vivo study of USPIO in the rat showed that at low doses (14 mumol Fe/kg), the myocardial signal was enhanced by 30%, whereas at high doses (77 mumol Fe/kg), it fell by -50%. These results indicate that in T1-weighted spin echo sequences, the MR signal can be enhanced by low concentrations of superparamagnetic compounds. This effect could be useful in perfusion imaging, and is also important for a better understanding of any possible paradoxical positive enhancement which could occur in perfused organs.

Animals↗
PubMed1993

Internal architecture of the parotid gland at MR imaging: facial nerve or ductal system?

A radiologic-anatomic study was performed to determine the nature of the low-signal-intensity curvilinear structures currently seen in the normal parotid gland on axial T1-weighted magnetic resonance (MR) images. These structures are considered by some to represent the intraparotid facial nerve. After cannulation of the Stensen duct, the authors imaged the parotid gland of two cadavers in situ before and after intraductal injection of gadolinium tetrazacyclododecanetetraacetic acid. Retrograde filling was obtained in one gland. The same sections were used throughout a subsequent anatomic study, allowing correlation of the MR findings with the macroscopic and histologic appearance of the gland. Comparison of MR images and gross and histologic sections established that two intraparotid facial nerve segments, although identified from the histologic study, were not visible on corresponding MR images. Many areas of low signal intensity seen within the gland were found to represent the main duct and some afferent ductal branches.

Cadaver↗
PubMed1993

Periventricular leukomalacia: correlation between MR imaging and autopsy findings during the first 2 months of life.

PURPOSE: To correlate magnetic resonance (MR) imaging and pathologic findings in premature infants with periventricular leukomalacia (PVL). MATERIALS AND METHODS: Eight premature infants with PVL who died after 3-7 weeks of life were studied with in vivo T1-weighted MR imaging, and imaging patterns were compared with hypoxic-ischemic injuries at pathologic analysis. RESULTS: Cavities were seen as zones of absent or weak signal intensity. Translucent sparsely cellular zones appeared as areas of intermediate intensity, and cellular reactions were seen as limited linear or punctate zones of increased intensity, usually less intense than the cortex. MR imaging provided reliable depiction of these lesions, with adequate estimation of their volume and topography. However, the extent of periventricular cellular lesions was underestimated. In one case, blood seen as hyperintense or isointense zones masked portions of cystic lesions, and in three cases small thalamic lesions were overlooked. CONCLUSION: With the above limitations, T1-weighted MR imaging offers precise evaluation of PVL.

Autopsy↗
PubMed1993

Intraabdominal serous fluid collections after appendectomy: a normal sonographic finding.

OBJECTIVE: The significance of sonographic findings 1 week or less after appendectomy is difficult to evaluate without knowing the inconsequential abnormalities that may occur in these patients. Accordingly, we performed postoperative sonography on patients who had a normal course after appendectomy to determine the findings that can be considered normal within 1 week after surgery. SUBJECTS AND METHODS: Forty-four patients who had an appendectomy for acute appendicitis and who had normal findings at clinical follow-up 5 days and 6 months later were included in the study. In all patients, sonograms were obtained on the fifth postoperative day and interpreted by a radiologist who did not know the surgical findings. RESULTS: Ten fluid collections (23%) were found in the pericecal area, ranging in size from 10 x 10 mm to 40 x 20 mm. The collections were hypoechoic or anechoic, crescent-shaped, and immobile. Fluid collections were more common in cases of suppurative appendixes (6/20, 30%) than in cases of inflamed appendixes (4/19, 21%) and in retrocecal appendixes (3/9, 33%) than in normally located appendixes (7/34, 21%). However, the differences were not statistically significant (p > .05). CONCLUSION: Inconsequential fluid collections are detected with considerable frequency on postoperative sonograms 5 days after an appendectomy. Consequently, not every fluid collection should be considered an abscess.

Abdomen↗
PubMed1992

The meniscofemoral ligaments: magnetic resonance imaging and anatomic correlations.

Examination of the knee joint by magnetic resonance imaging (MRI) is a noninvasive technique of proven reliability as regards lesions of the menisci and ligaments. It provides good definition of the different anatomic structures. The meniscofemoral ligaments have been observed with varying frequency and may be responsible for false images. However, it is important to detect them in cases of hypermobile discoid menisci of the 'Wrisberg ligament type' in order to guide the surgeon in their excision during total meniscectomy. We have attempted to assess the ability of MRI to visualise the meniscofemoral ligaments in correlation with an anatomic study and to identify certain anatomic pitfalls. This study will allow better investigation of the hypermobile menisci associated with the meniscofemoral ligaments. A clinical case is reported to illustrate its practical importance.

Humans↗
PubMed1992

Superparamagnetic iron oxide-enhanced magnetic resonance imaging of experimental liver tumors after mitomycin C administration.

The influence of mitomycin C chemotherapy on superparamagnetic iron oxide (SPIO) uptake by the liver was studied in rats (n = 70). This commonly used antineoplastic drug induces a decrease in the phagocytic function of the macrophage-phagocytic system (MPS). The plasma clearance of SPIO measured by relaxometry followed a biexponential model. The fast component half-life increased from 2.9 minutes in controls to 4.5 minutes in mitomycin C-treated animals. The slow component half-life increased from 11.3 to 36.7 minutes. Nevertheless, the magnetic resonance imaging (MRI) diagnostic efficacy 2 hours after infusion of the superparamagnetic agent AMI 25 (n = 10) was as satisfactory in the treated group as in the untreated one. These MRI results were consistent with the relaxometric T2* liver measurements, which were identical in both groups.

Animals↗
PubMed1992

[Contribution of gradient-echo MRI in the study of subacromial pathology: correlation between surgery and arthrography].

30 asymptomatic volunteer subjects and more than 400 patients with suspected rotator cuff lesions were examined by MRI at 0.5 T using T2*-PD weighted gradient echo (T2-GEI) sequences. Its superiority over T2 spin echo imaging was established in previous studies. The results were compared to those of surgery in 87 cases and arthrography in 233 cases (associated with CT arthrography in 70 cases). In the operated patients, T2-GEI and arthrography correctly diagnosed 49 complete ruptures (CR). T2-GEI was found to be superior to arthrography for defining the real extent of the rupture, the degree of tendon retraction and the local muscular trophicity, essential information to define the therapeutic indications. In contrast, among 22 lesions of the long biceps tendon, correctly demonstrated by arthrography or CT arthrography, 5 intracapsular lesions were not detected by MRI. MRI was able to detect 8 lesions of the anterior labrum associated with a CR not demonstrated by arthrography. Lastly, among the 18 cases of partial inferior rupture (PIR), 6 partial superficial ruptures and 14 cases of inflammatory changes, correctly diagnosed by MRI, only 8 PIR were also demonstrated by arthrography. For the non-operated patients investigated by the two modalities (146 cases), T2-GEI and arthrography were concordant in 43 cases. In contrast, 103 intact cuffs on arthrography showed features on T2-GEI compatible with tendinopathy without rupture, bursitis and degenerative changes. In the absence of very fine surgical or histological correlations for these small lesions, it is impossible, at the present time, to determine the real sensitivity and specificity of MRI.

Arthrography↗
PubMed1992

[Nasal and sinusal polyposis. Semiology and values of magnetic resonance imaging].

Twelve patients with nasal polyposis were examined with magnetic resonance imaging (MRI) prior to surgical ethmoidectomies (20 ethmoidectomies). MRI signal was analyzed in correlation with surgical findings in order to define the semiology of nasal and sinuses polyps. One of the most important point of this semiology is based on the analysis of sequences after administration of gadolinium. MRI seems an interesting method for analysing the extension of nasal polyposis and could be useful for ENT surgeons before an endoscopic nasal surgery.

Adolescent↗
PubMed1991

Systematic lower limb phlebography in acute spinal cord injury in 147 patients.

This study was concluded on paraplegic and tetraplegic patients of all aetiologies except neoplasic, where paralysis developed within 48 hours. All patients were admitted to the rehabilitation department within 90 days after the onset of paralysis. In a preliminary review of 328 files, there were 27 cases of clinical deep vein thrombosis (DVT) and 10 with pulmonary embolism (PE), 6 of which were fatal. A prospective study was conducted, based on systematic detection of asymptomatic DVT with phlebography. Among the 147 patients, 20 previously presented with DVT. The 127 others underwent phlebography which showed 39 DVT in 29 patients. Eighty seven patients with negative phlebography underwent a second study a month later which showed 14 DVT in 12 patients. Only one minor pulmonary embolism occurred in these 147 patients. The incidence of DVT after acute spinal cord injury and the frequent absence of clinical manifestations were confirmed. Prophylactic anticoagulant therapy is useful but insufficient. This study demonstrates that systematic and repeated detection of DVT by phlebography may reduce the incidence of PE.

Adult↗
PubMed1991

Liver tumors in cirrhosis: experimental study with SPIO-enhanced MR imaging.

The influence of cirrhosis on superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging of the liver was studied in 31 rats. Experimental models included carbon tetrachloride-induced cirrhosis and liver engrafting of rhabdomyosarcoma S4T cells. Hepatic uptake of SPIO measured with relaxometry decreased dramatically with histologic grade, while splenic uptake increased; the same results were achieved by calculating K values. Imaging of 13 tumorous cirrhotic rats confirmed these results by showing a muted decrease in liver signal intensity on spin-echo images after injection of SPIO. Nevertheless, all intrahepatic tumors could be visualized, as confirmed by postmortem examination. On gradient-echo images, postinjection contrast between the tumor and the liver was not affected by cirrhosis. Thus, despite strong impairment of hepatic uptake in cirrhosis, the diagnostic efficacy of MR imaging with SPIO did not seem to be significantly affected.

Animals↗