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Biomedical subjects

T Stadnik

Publications and source records attributed to T Stadnik.

At least 19 recordsLinked to original sources
PubMed2006

Prognostic value of perfusion-weighted imaging in brain glioma: a prospective study.

OBJECT: Biopsy targeting based on MR imaging alone may fail to identify malignant areas in brain gliomas. Considering the differences in relative Cerebral Blood Volume (rCBV) ratios reported among tumour grades, we evaluated whether perfusion-weighted MR imaging (PWI) could usefully implement the routine preoperative imaging by detecting those areas bearing a higher yield for malignancy to guide the stereotactic biopsy or the surgical removal. CLINICAL MATERIAL AND METHODS: We studied a series of 55 consecutive patients with newly diagnosed brain glioma using both conventional MR imaging and PWI in the preoperative assessment. The pathological diagnosis was established by stereotactic biopsy in 29 cases and by craniotomy in 24 cases. We evaluated the patient survival to detect undergrading. DISCUSSION: Independent from contrast-enhancement, perfusion-weighted MR imaging improved the target selection in stereotactic biopsy guidance and the removal of malignant areas in tumours amenable to surgery. Particularly sensitive to the perfused part of the tumour as to small regional changes, rCBV maps allowed a better detection of malignant areas. The rCBV ratios correlated significantly to the tumour grade and the final outcome (p < 0.01). CONCLUSIONS: We found PWI valuable in the preoperative assessment of brain gliomas, discriminating high from low-grade gliomas. PWI can easily be performed on widely available MR imaging systems as part of the routine imaging of gliomas.

Adolescent↗
PubMed2006

Demonstration of tissue alterations by ultrasonography, magnetic resonance imaging and spectroscopy, and histology in breast cancer patients without lymphedema after axillary node dissection.

Estimates of the incidence of arm swelling after axillary lymph node dissection for breast cancer range from 10 to 37%. Yet the subjective sensation of edema is described in at least 54% of patients. The purpose of this research was to examine the structural changes occurring in the subcutaneous tissue that might explain these subjective complaints using multiple imaging modalities. Two female cadavers with unilateral breast amputation and axillary dissection were studied. The dermal and subcutaneous layers of both arms were visualized with high frequency ultrasonography, and magnetic resonance imaging and spectroscopy (MRS), and tissue biopsies were taken for histological evaluation. On the operated side, ultrasound imaging showed a hyperechogenic subcutis and the fat-to-water relationship in adipose cells was higher as measured by MRS. Dissection of the arms revealed structural adipose tissue changes, which were confirmed by microscopic evaluation.

Biopsy↗
PubMed2005

Quantification of renal perfusion and function on a voxel-by-voxel basis: a feasibility study.

The feasibility of a voxel-by-voxel deconvolution analysis of T(1)-weighted DCE data in the human kidney and its potential for obtaining quantification of perfusion and filtration was investigated. Measurements were performed on 14 normal humans and 1 transplant at 1.5 T using a Turboflash sequence. Signal time-courses were converted to tracer concentrations and deconvolved with an aorta AIF. Parametric maps of relative renal blood flow (rRBF), relative renal volume of distribution (rRVD), relative mean transit time (rMTT), and whole cortex extraction fraction (E) were obtained from the impulse response functions. For the normals average cortical rRBF, rRVD, rMTT, and E were 1.6 mL/min/mL (SD 0.8), 0.4 mL/mL (SD 0.1), 17s (SD 7), and 22.6% (SD 6.1), respectively. A gradual voxelwise rRBF increase is found from the center of two infarction zones toward the edges. Voxel IRFs showed more detail on the nefron substructure than ROI IRFs. In conclusion, quantitative voxelwise perfusion mapping based on deconvolved T(1)-DCE renal data is feasible, but absolute quantification requires inflow correction. rRBF maps and quantitative values are sufficiently sensitive to detect perfusion abnormality in pathologic areas, but further research is necessary to separate perfusion from extraction and to characterize the different compartments of the nephron on the (sub)voxel level.

Algorithms↗
PubMed2004

Choice of the regularization parameter for perfusion quantification with MRI.

Truncated singular value decomposition (TSVD) is an effective method for the deconvolution of dynamic contrast enhanced (DCE) MRI. Two robust methods for the selection of the truncation threshold on a pixel-by-pixel basis--generalized cross validation (GCV) and the L-curve criterion (LCC)--were optimized and compared to paradigms in the literature. GCV and LCC were found to perform optimally when applied with a smooth version of TSVD, known as standard form Tikhonov regularization (SFTR). The methods lead to improvements in the estimate of the residue function and of its maximum, and converge properly with SNR. The oscillations typically observed in the solution vanish entirely, and perfusion is more accurately estimated at small mean transit times. This results in improved image contrast and increased sensitivity to perfusion abnormalities, at the cost of 1-2 min in calculation time and hyperintense clusters in the image. Preliminary experience with clinical data suggests that the latter problem can be resolved using spatial continuity and/or hybrid thresholding methods. In the simulations GCV and LCC are equivalent in terms of performance, but GCV thresholding is faster.

Arteries↗
PubMed2002

Extramedullary plasmacytoma of the cavernous sinus.

We present the case of an 80-year-old male with an history of multiple myeloma (MM) stage I with extramedullary plasmacytoma of the neck, diagnosed 18 months before and in complete remission after radiation therapy and melphalan-prednisone therapy. He was admitted with signs and symptoms characteristic for cavernous sinus syndrome, including diplopia, exophthalmia, ptosis and orbital pain. Magnetic resonance imaging showed a mass lesion in the cavernous sinus, consistent with relapsing extramedullary plasmacytoma. The patient received palliative radiation therapy and high dose dexamethasone, but treatment failed and the patient died. This case represents one of the few reports of extramedullary plasmacytoma of the cavernous sinus. The development of a clinical presentation of cavernous sinus syndrome in a patient with a history of MM or extramedullary plasmacytoma should raise the suspicion of a plasmacytic involvement of the cavernous sinus.

Aged↗
PubMed2001

Severe adverse reactions with contrast agents for magnetic resonance: clinical experience in 30,000 MR examinations.

We report on the frequency, manifestations and reactions to gadolinium contrast media in patients who underwent MR imaging at our institution between 1988 and 1998. During a 10-year period 30,000 patients received an intravenous injection of 0.1 mmol/kg gadoterate meglumine or gadopentetate dimeglumine for an MRI examination. When a reaction occurred a written report was made (the events were categorized into mild, moderate, and severe). In the period of 10 years we obtained three reports of moderate or severe reactions to the administration of gadolinium. This paper discusses the safety issues of intravenous contrast media in MR imaging, focusing on two gadolinium complexes, gadoterate meglumine, gadopentetate dimeglumine.

Adult↗
PubMed1999

Diffusion-weighted MRI in cyclosporin A neurotoxicity for the classification of cerebral edema.

Cyclosporin A, an immunosuppressive agent, is known to have neurotoxic effects, but until now, there has not been agreement on the underlying mechanism. Our report suggests, by using diffusion-weighted MRI, that the brain lesions caused by cyclosporin A, are probably related to vasogenic edema. This may explain the complete recovery of the lesions on imaging when cyclosporine therapy is stopped.

Adult↗
PubMed1999

Use of diffusion-weighted MR imaging in differential diagnosis between intracerebral necrotic tumors and cerebral abscesses.

The differential diagnosis between intracerebral necrotic tumors and cerebral abscesses is frequently impossible with conventional MR imaging. We report two cases of cerebral abscesses that showed high signal on diffusion-weighted echo planar imaging and a strongly reduced apparent diffusion coefficient. This appearance was not present in our cases of necrotic/cystic gliomas (eight cases) and necrotic metastases (two cases). We believe that diffusion-weighted MR imaging may be a diagnostic clue in cases of cerebral "ring-enhancing" masses.

Aged↗
PubMed1997

Calcified, cystic brain metastases.

Calcifications are uncommon in metastases. Adenocarcinoma, osteopenic, osteosarcoma, lung and breast carcinoma can be the origin. A rare case of calcified cystic brain metastasis deriving from papillary cystadenocarcinoma is reported.

Aged↗
PubMed1996

[Medical imaging and headache: choice of studies and their economic impact].

These past few years, new imaging technologies, very efficient but often quite expensive, have been developed. Within the context of budgetary restrictions, these progresses require a carefully planned strategy on the choice of investigations. Within the clinical environment of headaches, we have to discuss: conventional radiology (skill and cervical spine), cerebral CT scan, Magnetic Resonance Imaging and Angiography. These examinations are first discussed about their strong and weak aspects; then their indications are presented by pathology group. The related costs are analysed in terms of: health insurance rate, real production costs, consumption volume and total budgetary cost for Belgium. Based upon these data, concrete recommendations are proposed.

Brain Diseases↗
PubMed1995

Cortical stimulation for central neuropathic pain: 3-D surface MRI for easy determination of the motor cortex.

Motor cortex electric stimulation has been reported to be effective for the treatment of central post-stroke pain and trigeminal neuropathic pain. Five patients with pain due to injury of the trigeminal nerve and with abnormalities of facial sensibility, as well as two patients suffering of a post-stroke thalamic pain, were subjected to stimulation applied epidurally on the motor cortex. Quadripolar electrodes were implanted under local anaesthesia and the precise location of the motor cortex was determined on three-dimensional surface MRI the day prior to surgery. In our experience, correct topographic localization of the electrode on the motor cortex seems to be crucial to obtain pain reduction.

Adult↗
PubMed1994

The value of three-dimensional turbo-FLASH and spin-echo sequences in the detection of pituitary microadenomas following gadolinium administration.

Our purpose was the comparison of T1-weighted spin-echo (SE) and three-dimensional (3D) Turbo-fast low-angle shot (FLASH) (3DTFL) in detection of 14 pituitary microadenomas following intravenous gadolinium (Gd). 3DTFL represents an important improvement in the diagnosis of pituitary microadenomas. In two cases, the site of the tumour was correctly identified only by Gd-enhanced Turbo-FLASH. Nevertheless, in two other cases, the Gd-enhanced 3DTFL gave false negative (FN) results while the T1-weighted SE images enabled correct localisation. Replacement of T1-weighted SE by 3DTFL cannot therefore be advocated and use of both contrast-enhanced sequences offers the highest detection capability for microadenomas.

Adenoma↗
PubMed1994

Pituitary microadenomas: diagnosis with dynamic serial CT, conventional CT and T1-weighted MR imaging before and after injection of gadolinium.

PURPOSE: The few studies comparing CT and MR in the diagnosis of pituitary microadenomas give discordant results. This prospective study compares the value of dynamic serial CT (DSCT), conventional CT (CCT), pre-Gd T1-weighted spin echo (T1SE-Gd) and post-Gd T1-weighted SE (T1SE+Gd) in the detection of pituitary microadenomas. METHODS: The value of CT and MR was assessed in 17 cases, with the surgical confirmation as reference. The CTs and MRs were independently and blindly evaluated by two neuroradiologists. Because the finding at MR and/or CT influenced the selection of patients for surgery, the positive predictive value was calculated. The sensitivity calculation applies only for a specific group of postsurgical patients with positive CT and/or MR (marked with an asterisk for these reasons). RESULTS: In this study, the highest sensitivity* (88% and 82%, respectively, for observers I and II) was achieved by DSCT. The T1SE-Gd and T1SE+Gd (evaluated separately) were slightly inferior (sensitivity* of 76% for observer I). The combination of T1SE-Gd with T1SE+Gd improved the sensitivity* to 94% and 82% respectively, for observers I and II. There was also moderate improvement of sensitivity* by combination of DSCT with conventional CT (94% for observer I). CONCLUSION: These results suggest that rapid injection of a large amount of contrast conjointly with a fast scanning through the pituitary is crucial for the confident detection of microprolactinomas. Taking into account the similar results of the combination DSCT + CT and T1SE-Gd + T1SE+Gd in the detection of microprolactinomas, high field MRI is the first step modality in the evaluation of presumed hypophyseal hyperprolactinemia.

Adenoma↗
PubMed1994

A method for myelin fiber orientation mapping using diffusion-weighted MR images.

In the past, the anisotropic diffusion of water molecules in white matter in the brain has been correlated to the basic symmetry of the myelin fibers: water diffuses more readily along the fiber direction than perpendicular to it. As a consequence, diffusion sensitized magnetic resonance imaging can be expected to be useful for studying the fiber orientation. In this work, we present a method for exploiting this type of information to map the fiber orientations in the image plane. It makes use of three diffusion-weighted images with sensitizing gradients along x, y and u, an axis at 45 degrees with respect to x and y. The orientation information contained in these images is summarized in a single image representing the angle between the fiber direction and a fixed axis, making use of a cyclic color scale. The method is evaluated using computer simulations for a variety of diffusion weighting strengths and signal-to-noise ratios, tested on a phantom and illustrated on an in vivo example. An extension to the determination of the fiber orientation in three dimensions is also described.

Anisotropy↗