PubMed Health⌕ Search

Biomedical subjects

E Kanal

Publications and source records attributed to E Kanal.

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

Pregnancy and the safety of magnetic resonance imaging.

Many data exist regarding the safety of the static and time-varying magnetic and electromagnetic fields used in MR environments for the developing fetus. Many of these data, however, are confusing and nebulous. The literature in this area is reviewed, and the issues related to MR imaging of the pregnant patient and MR and the pregnant health care practitioner are discussed. Practice guidelines also are suggested.

Electromagnetic Fields↗
PubMed1993

Blood flow in the portal vein: velocity quantitation with phase-contrast MR angiography.

Quantitative phase-contrast magnetic resonance (MR) angiography of the portal vein was prospectively evaluated in 79 fasting patients and 23 healthy volunteers. Images were obtained during a 12-second breath-hold acquisition in the coronal (n = 102) and axial (n = 11) planes. Pathologic correlation was available in 55 of 79 patients and included findings of cholangiocarcinoma, cirrhosis, hepatocellular carcinoma, hepatitis, and metastatic disease. Forty-one patients had correlative Doppler ultrasound (US) findings. MR and US findings correlated as to flow direction in all cases. In nine patients, Doppler US velocity measurements were available and closely correlated with MR findings. A comparison of axial and coronal portal venous phase-contrast measurements in 11 patients revealed no substantial difference with regard to the plane used. Quantitative phase-contrast MR angiography is a simple and rapid technique for the assessment of portal venous patency, flow direction, and flow velocity and, combined with high-resolution conventional MR imaging, may obviate the current use of both computed tomographic and US examinations.

Blood Flow Velocity↗
PubMed1993

Survey of reproductive health among female MR workers.

Epidemiologic data were obtained to evaluate potential risks from exposure to the static and time-varying magnetic fields used in magnetic resonance (MR) imaging. A questionnaire sent to women workers in more than 90% of clinical MR facilities in the United States addressed menstrual-reproductive experiences, work activities, and potential confounders (eg, age, smoking, alcohol use). In 1,915 completed questionnaires, 1,421 pregnancies were reported: 280 occurred in an MR worker (technologist or nurse), 894 in an employee in another job, 54 in a student, and 193 in homemakers. Comparing MR-worker pregnancies with those occurring in employees at other jobs, a relative risk ratio of 1.27 (95% confidence interval [CI], 0.92-1.77) was found for spontaneous abortions; for conception taking more than 12 months, 0.90 (CI, 0.54-1.51); for delivery before 39 weeks, 1.19 (CI, 0.76-1.88); for birth weight below 5.5 lb (2.5 kg), 1.01 (CI, 0.50-2.04); and for male gender of the offspring, 0.99 (CI, 0.80-1.22). Adjustment for maternal age, smoking, and alcohol use also failed to markedly change any of the associations. These results suggest that there is not a substantial increase in these common adverse reproductive outcomes.

Female↗
PubMed1993

MR procedures and biomedical implants, materials, and devices: 1993 update.

PURPOSE: To provide information on ferromagnetic metallic implants, materials, and devices that may be exposed to static magnetic fields during magnetic resonance (MR) imaging or spectroscopy. MATERIALS AND METHODS: An updated compilation of the results of more than 80 studies lists the specific object tested, the material used to construct the object, whether the object was deflected or moved during exposure to the static magnetic field, and the highest field strength used for testing the object (range, 0.147-4.7 T). RESULTS: The ferromagnetic qualities of 338 objects (32 aneurysm and hemostatic clips; six biopsy needles; five carotid artery vascular clamps; 18 dental devices or materials; 11 halo vests; 29 heart valve prostheses; 20 intravascular coils, filters, and stents; 22 ocular implants; 30 orthopedic implants, materials, and devices; 62 otologic implants; 23 pellets and bullets; 13 penile implants; 38 vascular access ports; and 29 miscellaneous objects) are reported. CONCLUSION: MR imaging or spectroscopy may be contraindicated in patients with such objects because of the risk of movement or dislodgment of the object.

Biocompatible Materials↗
PubMed1992

Patient monitoring during clinical MR imaging.

The impressive growth in the number of patients imaged with magnetic resonance (MR) technology has been accompanied by technical advances that have permitted more acutely ill patients to be studied with this diagnostic tool. Such patients, however, might require monitoring of vital functions during the examination. Unfortunately, the present construction of most MR imaging systems makes direct visualization of the patient difficult, if not impossible. Furthermore, the static and time-varying magnetic (and electric) fields associated with MR imaging systems may be incompatible with most physiologic monitoring devices, either because of safety or function. The authors review herein the data regarding presently available monitoring devices for various physiologic parameters and provide recommendations regarding what--and whom--to monitor during clinical MR examinations.

Humans↗
PubMed1992

A comparison between magnetic resonance imaging and computed tomography for stereotactic coordinate determination.

The spatial accuracy of magnetic resonance imaging (MRI) has not been established for stereotactic surgery. Magnetic susceptibility artifacts may lead to anatomical distortion and inaccurate stereotactic MRI coordinates, especially when targets are in regions of the brain out of the center of the magnetic field. MRI-guided stereotactic localization, however, provides better multiplanar target resolution than is available with computed tomographic (CT) scanning. Therefore, we compared the accuracy of stereotactic coordinates determined by MRI and CT studies in 41 patients (53 targets). Coordinates were measured in each plane and as vector distances between the target and the center of the stereotactic frame on axial or coronal MRI studies. Absolute axial plane MRI and CT distances varied an average of 2.13 +/- 1.59 mm. The mean difference in measurements in the X (left-right) dimension was 1.19 mm and 1.55 mm in the Y (anterior-posterior) dimension. Central targets (located less than 2 cm from the frame center) had a mean MRI-CT difference of 2.09 +/- 1.79 mm; peripheral targets (greater than 2 cm from the frame center) differed by 2.17 +/- 1.3 mm. The voxel volumes were calculated for all compared images. Although differences between the physical properties of data acquisition with each imaging modality could explain the observed CT-MRI discrepancies, a 1-pixel difference in target selection could account totally for all the variance observed. MRI field strength (0.5 vs. 1.5 T) did not correlate with coordinate determination accuracy. We conclude that MRI-guided stereotactic localization can be used with confidence for most diagnostic, functional, and therapeutic stereotactic procedures.

Artifacts↗
PubMed1990

Safety considerations in MR imaging.

The authors identify eight areas of potential safety concern during clinical magnetic resonance (MR) imaging. These include (a) biologic effects of the static magnetic field; (b) ferromagnetic attractive "projectile" effects of the static magnetic field; (c) potential effects of the relatively slowly time-varying magnetic field gradients; (d) effects of the rapidly varying radio-frequency (RF) magnetic fields, including RF power deposition concerns; (e) auditory considerations from noise caused by the rapidly pulsed magnetic field gradients; (f) safety considerations concerning superconductive systems, including quenches, use of cryogens, and cryogen storage and handling; (g) psychological effects, such as claustrophobia and anxiety induced because of the examination; and (h) possible effects of the intravenous use of the MR contrast agent gadopentetate dimeglumine. The concerns in each of these categories are elaborated upon, and the available data are presented to clarify their status.

Accident Prevention↗
PubMed1988

Ferrioxamine as a magnetic resonance contrast agent. Preclinical studies and phase I and II human clinical trials.

The preclinical and clinical trial experience with ferrioxamine (S-FDF; Salutar, Inc.) as a contrast agent for magnetic resonance imaging (MRI) is summarized. The results in 44 patients or subjects show that the drug is safe and well tolerated when given intravenously. In certain conditions, early results show that the use of this contrast agent provides more information than can be obtained with MRI alone.

Adult↗
PubMed1988

Normal perivascular spaces mimicking lacunar infarction: MR imaging.

Perivascular (Virchow-Robin) spaces normally surround perforating arteries that enter the medial temporal lobes, corpus striatum, and thalamus. The high soft-tissue sensitivity of magnetic resonance (MR) imaging allows for the frequent detection of such cerebrospinal fluid (CSF)-filled spaces. Especially on axial images, these CSF-filled perivascular spaces may be confused with pathologic lesions, such a lacunar infarcts. Postmortem brain specimens demonstrate the anatomy of perivascular spaces around perforating arteries. Orthogonal images in the living patient help confirm this anatomic relationship. The characteristic CSF signal patterns from these foci are further evidence of their anatomic identification and true benign nature.

Brain↗
PubMed1988

Meniscal and ganglion cysts of the knee: MR evaluation.

Meniscal and ganglion cysts frequently present as palpable masses of the knee but occur at different locations than do popliteal cysts. Meniscal cysts also may be discovered incidentally on studies performed for suspected internal derangement. Sixteen cystic lesions of the knee were evaluated with MR, including 11 meniscal cysts and five ganglion cysts. Scans were performed at 1.5 T by using a transmit/receive extremity coil or a receive-only surface coil. Standard spin-echo imaging, including at least one long-TR/asymmetric-TE sequence, was performed in all cases. In six patients, gradient-echo, reduced flip-angle sequences also were done. All meniscal cysts (but none of the ganglion cysts) were associated with horizontal meniscal tears. Cysts were visualized best on the long-TR/TE images; meniscal tears were seen best on the short-TR/TE and long-TR/short-TE images. Meniscal tears and cysts were also seen well on the fast-scanning sequences. Septations were noted in four meniscal cysts and in four ganglion cysts on the long-TR/TE images. Long-TR/TE images were also useful in showing the relationship between the cyst and joint capsule in three of the ganglion cysts. MR imaging is an effective, noninvasive method for evaluating cystic lesions of the knee. Meniscal cysts are always associated with underlying horizontal meniscal tears, which can be detected with MR. Ganglion cysts are not associated with meniscal tears, but may have connections to the joint capsule, which can be detected with MR.

Humans↗