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Biomedical subjects

Didier Mathieu

Publications and source records attributed to Didier Mathieu.

7 recordsLinked to original sources
PubMed2004

Comparison of in vitro and in vivo MRI of the spine using parallel imaging.

OBJECTIVE: The purpose of this study was to compare the image quality of two parallel-imaging methods applied to standard turbo spin-echo T2-weighted imaging of the lumbar spine. MATERIALS AND METHODS: Phantom imaging and lumbar spine studies of 15 healthy subjects were performed using T2-weighted turbo spin-echo sequences obtained with and without parallel imaging (generalized autocalibrating partially parallel acquisition [GRAPPA] and modified sensitive encoding [mSENSE]) on a 1.5-T magnet. The signal-to-noise ratio (SNR) and uniformity were measured in the phantom, and SNR and signal difference-noise ratio were evaluated in cerebrospinal fluid, vertebral bodies, and subcutaneous fat of the volunteers, using both techniques sequentially. Aliasing artifacts on GRAPPA and mSENSE images were visually evaluated. SNRs were compared using the Student's paired t test, with p values less than 0.05 considered significant. RESULTS: In the phantom study, when the same number of coil elements were used (n = 3), SNR and uniformity values obtained with standard T2-weighted turbo spin-echo sequences were higher than those obtained with parallel sequences. The GRAPPA SNR obtained with three coil elements was higher than the standard T2-weighted SNR obtained with one coil element. Similar findings were noted regarding uniformity. In the lumbar spine, GRAPPA SNR values for fat, cerebrospinal fluid, and vertebral bodies were significantly higher than mSENSE SNR values, with a p value less than 0.01, but were not significantly different from T2-weighted turbo spin-echo SNR values. GRAPPA signal difference-noise ratio values were significantly higher than mSENSE signal difference-noise ratio values, with a p value less than 0.01, but were not significantly different from T2-weighted turbo spin-echo signal difference-noise ratio values. GRAPPA produced fewer aliasing artifacts than mSENSE. CONCLUSION: In spine MRI, GRAPPA may be used to reduce scanning time and yields a higher SNR than mSENSE without any increase in aliasing artifacts and with an SNR similar to that obtained with standard T2-weighted turbo spin-echo.

Artifacts↗
PubMed2004

MRI of atypical focal nodular hyperplasia of the liver: radiology-pathology correlation.

OBJECTIVE: The purpose of our study was to determine the MRI features of atypical focal nodular hyperplasia of the liver and to compare them to pathology findings. MATERIALS AND METHODS: We retrospectively reviewed MRI and pathology findings in 27 focal nodular hyperplasia lesions with atypical MRI features. Six criteria for typical focal nodular hyperplasia were required: iso- or hypointensity on T1-weighted sequences and iso- or slight hyperintensity on T2-weighted sequences; homogeneous signal intensity; central hyperintense area on T2-weighted sequences; marked lesion contrast enhancement; accumulation of gadolinium chelates within the central area on delayed contrast-enhanced T1-weighted sequences; and absence of capsule. RESULTS: The most common atypical radiology features included absence of, or an atypical, stellate area; heterogeneity on both T1- and T2-weighted images; and high-intensity signal on T1-weighted sequences. MRI-pathology correlation showed that T1 hyperintensity with no other atypical MRI feature (n = 3) could be explained by steatosis, sinusoidal dilatation, or hemorrhage. In addition, in two patients with lesions smaller than 3 cm in diameter, the only atypical MRI feature was absence of a stellate area. CONCLUSION: These findings suggest a lesion that is hyperintense on T1-weighted sequences or that lacks a stellate area but is smaller than 3 cm in diameter can be diagnosed as focal nodular hyperplasia provided all other MRI criteria for this diagnosis are present. In such cases, close monitoring on MRI without invasive diagnostic procedures may be warranted. However, in large lesions (> 3 cm) without a stellate area and in lesions with heterogeneity, histopathology examination is mandatory to rule out other diagnoses.

Adolescent↗
PubMed2003

Calculation of the crystal densities of molecular salts and hydrates using additive volumes for charged groups.

Standard group volumes which can be used to estimate the crystal densities of molecular salts and hydrates are reported, as a complement to values derived recently for the functional groups of neutral organic compounds. These new parameters were derived from a least-squares fit of cell volumes for a set of 1132 ionic molecular crystals from the Cambridge Structural Database. Their values point to the unusual overlap between monovalent O atoms and neighbouring H atoms. Using the new group volumes presently obtained, the crystal densities of the salts are predicted with an average error of <2.5%, while previous atom-based schemes yield average errors of >3%. To illustrate the possible application of the present database, the problem of designing environmentally friendly propellants is addressed.

Journal Article↗
PubMed2002

Percutaneous coil embolization of postcatheterization arterial femoral pseudoaneurysms.

STUDY DESIGN: This study was a prospective monocentric study to assess the safety and effectiveness of percutaneous embolization with coils of postcatheterization femoral pseudoaneurysm (PCFP). PATIENTS AND METHODS: Seventeen PCFPs of 32-mm mean diameter in 16 patients were embolized while anticoagulant or antiplatelet therapy was maintained. Ultrasound scan-guided compression repair failed at least one time in 13 cases and was contraindicated in the four remaining cases. With ultrasound-Doppler scan guidance, the PCFPs were percutaneously punctured with a 16-gauge intravenous catheter. An angiogram was performed through the catheter to ensure its location within the sac. Stainless steel spring coils with synthetic fibers were introduced within the PCFP with fluoroscopic control. Successful thrombosis was checked with ultrasound-Doppler scan and was repeated at days 1, 30, and 180 when possible. RESULTS: All PCFPs of 32-mm mean diameter were successfully treated with two to nine coils. After embolization, gentle additional compression was necessary for complete occlusion, with a mean duration of 6.3 minutes (range, 0 to 15 minutes), except in one case with treatment with abciximab in which it was 45 minutes. All procedures were uneventful and painless. The mean follow-up period was 9.5 months (range, 1 to 21 months). Two recurrences (11.7%) were observed, and one was successfully treated with a second embolization. CONCLUSION: Percutaneous embolization with coils appears to be a safe and effective method for treatment of PCFP. It may be performed in patients undergoing anticoagulant or antiplatelet therapy and must be attempted when ultrasound scan-guided compression repair has failed or is contraindicated.

Adult↗
PubMed2001

Dilatation of the intrahepatic bile ducts associated with benign liver lesions: an unusual finding.

In three patients presenting different types of liver lesions, including isolated cyst, focal nodular hyperplasia (FNH), and hemangioma, intrahepatic bile duct dilatation was observed on US and CT. Final diagnosis was obtained by surgery in two cases (cyst and FNH) and by 1-year follow-up in one patient presenting an isolated hemangioma. The only common characteristic in our three cases was that lesions were present in segment four according to Couinaud's classification, at the level of the transverse fissure, suggesting that a space-occupying lesion at this site may cause compression of the common hepatic duct and right or left intrahepatic bile ducts. Our report indicates that compression may occur even with lesion of moderate size (35-40 mm in diameter). A benign liver lesion may cause a bile duct dilatation, particularly if located in segment 4, close to the hilum. Awareness of this possibility is important to avoid unnecessary invasive diagnostic procedures, particularly when all imaging criteria are consistent with a benign lesion.

Adult↗
PubMedDate not supplied

Magnetic resonance imaging for the diagnosis of stress fractures in a horse.

In humans, magnetic resonance (MR) imaging is the method of choice for the diagnosis of stress fractures. In this paper, bilateral stress fracture of the lateral condyle of the third metacarpal bone in a French trotter is described. Results of the radiographic, MR imaging, and histologic examinations are presented, with a focus on the MR signal abnormalities found. Based on this patient, the potential use of MR imaging for the diagnosis of stress fractures in horses is discussed.

Animals↗