Search PubMed⌕ Search

Biomedical subjects

J Valk

Publications and source records attributed to J Valk.

At least 199 records · Page 11Linked to original sources
PubMedDate not supplied

MR imaging of laryngeal cancer.

Forty-four consecutive patients with laryngeal carcinomas presenting at different stages of the disease were investigated by magnetic resonance (MR) imaging. Twelve patients (six with primary lesions and six with recurrent tumors) underwent laryngectomy, and the macro- and microscopic appearance of the slice specimens were correlated with MR imaging. In the remaining patients surgery was not performed, and MR results are compared with the laryngoscopic findings. Cancerous tissue was seen on T1-weighted images as a homogeneous mass of intermediate signal intensity. slightly higher than infrahyoid muscles. The MR examinations failed mainly in patients with tumor recurrence who had undergone previous radiation treatment.

Aged↗
PubMedDate not supplied

Detection and characterization of metastatic cervical adenopathy by MR imaging: comparison of different MR techniques.

Thirty-five patients scheduled to undergo a neck dissection for squamous cell carcinoma of the head and neck were evaluated preoperatively by magnetic resonance (MR) imaging. Axial and occasionally sagittal and coronal images were obtained. To define the most reliable technique to detect cervical lymph node metastasis, we compared several MR pulse sequences with and without Gd-DTPA administration to histopathologic findings in the neck dissection specimens. T1-weighted spin echo combined with T2-weighted gradient recalled echo (GE) sequences were found to be more useful than any other combination of pulse sequences in localizing lymph nodes. On T2-weighted GE images, lymph nodes were depicted with intermediate to high signal intensity in contrast to low signal muscular and fatty tissue. Gadolinium DTPA enhanced T1-weighted GE images reliably depict central lymph node necrosis, the most specific criterion for lymph node metastasis.

Adult↗
PubMedDate not supplied

Comparison of skull circumference and linear measurements with CSF volume MR measurements in hydrocephalus.

In children with hydrocephalus, accurate and reproducible estimation of the presence, severity, and course of the condition is of paramount importance for both clinical and scientific purposes. In this study, 30 hydrocephalic patients were assessed with a number of commonly used methods, such as occipitofrontal skull circumference (SC) measurements, Evans ratio (ER), and bicaudate index (BCI), as well as, for comparison, another ratio of linear measurements [ventricle-skull ratio (VSR)] and MR measurements of total intracranial CSF volume. In repeated CSF volume measurements in healthy volunteers, the MR method appeared to be accurate and reproducible. This technique was simpler and easier in application, requiring less interaction than comparable MR techniques described by others. The variation coefficients were within the same range. In increased CSF volumes, our technique can be recommended; in very small CSF volumes, another technique is more adequate. Direct assessment of CSF volume as a measure of hydrocephalus was preferable over derived estimations for scientific purposes and may function as a gold standard against which to evaluate other techniques that are easier to apply clinically. In comparison, SC measurements were poor; CSF volume changes were not reflected in SC changes. VSR was preferable over ER and BCI, because it correlated more closely with CSF volume.

Cerebrospinal Fluid↗
PubMedDate not supplied

Ultrafast scan magnetic resonance in prenatal diagnosis.

OBJECTIVE: To determine whether magnetic resonance (MR) can give additional information in prenatal diagnosis of congenital anomalies, when the ultrasound (US) analysis is not conclusive. METHODS: Ultrafast MR scanning examined 39 pregnant women with 41 fetuses in whom US was suspicious of fetal congenital abnormalities. Two techniques were used namely (1) HASTE inversion recovery sequence and (2) FISP 2D. RESULTS: Thirty-nine patients with 41 fetuses were referred for MR because of an equivocal US with regard to brain, spine, skeletal and miscellaneous anomalies. In 1 twin pregnancy, 1 co-twin has not been examined with MRI because of its demise. In 22 of them, additional information was obtained by MR. In 9 the MR was confirmative with the US examination. Four were false negative, comparing with the postnatal diagnosis. Three failed because of maternal claustrophobia and in 2 a diagnosis could not be made. From the 40 fetuses in this study, 38 were examined postnatally by MR, US, plain X-ray or autopsy was performed to confirm the prenatal diagnosis. CONCLUSION: The use of MRI in obstetrics has been limited, until recently. With fast MRI sequences it is not necessary to sedate the fetus. It is advisable in cases where US is equivocal concerning congenital anomalies of the fetus to use MR with fast or ultrafast scan technique, especially when the central nervous system is concerned.

Brain↗
PubMedDate not supplied

Functional MR imaging in Alzheimer's disease during memory encoding.

BACKGROUND AND PURPOSE: We applied functional MR imaging with a learning task in healthy elderly volunteers and in patients with Alzheimer's disease to study brain activation during memory performance. The purpose was to determine the feasibility of functional MR imaging during a learning task in healthy elderly volunteers and in patients with Alzheimer's disease and to test our hypothesis that brain activation is decreased in the medial temporal lobe (MTL) memory system in patients with Alzheimer's disease compared with control volunteers. METHODS: In 12 patients with mild to moderate forms of Alzheimer's disease and 10 elderly control volunteers, activation of the MTL memory system was studied. We used two learning tasks that required the encoding of new information into memory. After the functional MR imaging experiment, participants were tested for recognition of the encoded objects. RESULTS: In the elderly control volunteers, activation during memory encoding was observed in medial and lateral temporal lobe structures (fusiform, parietal and occipital parts, and hippocampal formation) and in the frontal cortex, as reported previously in studies of young control volunteers. Focusing on the MTL, we observed that activation was significantly decreased in patients with Alzheimer's disease compared with control volunteers in the left hippocampus and parahippocampal gyrus bilaterally during the first encoding task but not during the second (P < .05, uncorrected). CONCLUSION: Functional MR imaging with a learning task seems feasible in elderly volunteers and in patients with Alzheimer's disease. The measured functional signal decrease in MTL areas warrants further exploration of the (early) diagnostic usefulness of functional MR imaging in cases of Alzheimer's disease and other dementias.

Aged↗
PubMedDate not supplied

Toxic encephalopathy.

Explore the source record for details and available documents.

3,4-Methylenedioxyamphetamine↗
PubMedDate not supplied

Gadopentetate dimeglumine enhancement of multiple sclerosis lesions on long TR spin-echo images at 0.6 T.

The authors sought to determine if Gd-DTPA enhancement of multiple sclerosis (MS) hampers lesion detection on long TR spin-echo images (TE 60 msec) at 0.6 T. They measured the signal intensity (SI) of 41 lesions (10 patients) and normal-appearing gray (NAGM) and white matter (NAWM) before and after administration of contrast. The change in SI of nonenhancing lesions and NAGM and NAWM was small (less than or equal to 1.5%), and of enhancing lesions (5.3%) moderate. The contrast of nonenhancing lesions to NAGM and NAWM changed insignificantly, but the contrast of enhancing lesions to NAGM and NAWM increased significantly. The authors conclude that long TR images can be obtained after Gd-DTPA without hampering lesion conspicuity in research MR protocols in multiple sclerosis.

Adult↗
PubMedDate not supplied

The reflection of histology in MR imaging of Pelizaeus-Merzbacher disease.

Pelizaeus-Merzbacher disease is a rare disease of infants and young children in which there is an arrest of myelination of the CNS. The cause of the disorder is unknown. Three cases are reported, representing the connatal and classical forms of the disease. The MR images obtained of these children are compared with histologic findings as reported in the literature. In the connatal form a complete absence of myelin in the brain is demonstrated. In the classical form an arrest of myelination in an early stage of development is shown in combination with progressive abnormalities of the unmyelinated white matter and possibly a slow degradation of some myelin. MR imaging appears to be a unique diagnostic method for assessing the degree of hypomyelination, the core of Pelizaeus-Merzbacher disease, and for contributing to the understanding of the underlying pathology of this disorder.

Brain↗
PubMedDate not supplied

Oblique views in magnetic resonance imaging of the heart by combined axial rotations.

Magnetic resonance imaging of the heart, and more specifically of the left ventricle (LV), is optimized by using oblique imaging planes adapted to the long and short axes of the LV, comparable to other imaging modalities in cardiology. We report a procedure to perform two chamber views, four chamber views and true short axis views by combinations of electronic axial rotations. The technique of selecting appropriate gradient angles is explained. Thus, there is no requirement for altering patient position in the imager, while individual anatomic variations are taken into account.

Adult↗
PubMedDate not supplied

Contrast enhanced magnetic resonance imaging of the brain using gadolinium-DTPA.

This report concerns a clinical trial with gadolinium-DTPA (Gd-DTPA) as an intravenous contrast medium for magnetic resonance imaging (MRI) in patients with disorders of the central nervous system. Fifty patients, 30 females and 20 males, were examined without and with Gd-DTPA. The contrast medium was well tolerated by all patients. The results of MRI scanning without and with Gd-DTPA and those obtained with computed tomography (CT) using intravenous contrast enhancement were compared. This investigation comprised mainly patients with intracranial tumors, multiple sclerosis, and nasopharyngeal tumors. The results may be summarized as follows: 1) MRI with Gd-DTPA (MRI+) gave better results than MRI without Gd as regards delineation of the lesion, blood vessels and edema in cerebral tumors, pituitary adenomas and acute forms of multiple sclerosis (MS). 2) MRI+ was better than CT in 32 of the 50 cases examined; with intracerebral tumors it was better in 15 out of 18 cases. 3) MRI+ was always better than CT in patients with MS. In 3 out of 7 cases MRI demonstrated the acute MS lesions. 4) MRI+ seemed to have advantages also in nasopharyngeal tumors as ascertained from this limited experience.

Adult↗