MR imaging of the knee with a 0.064-T permanent magnet

Magnetic resonance (MR) imaging has proved beneficial in the evaluation of internal derangements of the knee. A limitation to general acceptance of MR imaging of the knee has been availability and cost. The recent introduction of low-field-strength MR imaging has shown promise in decreasing the cost and increasing the availability of this modality. High-resolution (pixel size, 0.7 mm2), three-dimensional Fourier transform (3DFT), thin-section (3.5 mm) imaging performed on a 0.064-T permanent magnet was used to evaluate 117 knees in 114 consecutive patients. The appearance of normal anatomy and internal derangements of the knee at low-field-strength imaging is described. Arthroscopic correlation was available for 28 knees. Findings from low-field-strength MR imaging and arthroscopy agreed in 79% of cases in the determination of meniscal tears. Partial-flip-angle techniques with 3DFT produced thin-section images of the knee of diagnostic quality. The authors conclude that in patients with internal derangements of the knee, low-field-strength (0.064-T) MR imaging may provide useful information.

Local blood flow measured by fluorescence excitation of nonradioactive microspheres

An X-ray fluorescence system with low Compton background and high counting efficiency was developed to measure regional blood flow with nonradioactive microspheres. The performance of the system was tested in vitro by counting mixed aqueous solutions of either Mo, Ag, and I; Nb, Ag, and Ba; or Zr, Mo, Rh, Ag, Sn, I, and Ba, as well as a mixture of Ag and Ba nonradioactive microspheres. Mixtures containing 2-20 ppm of each element were counted for 10 min by the fluorescence system, and the individual elements in mixtures of three to seven nonradioactive elements were measured with high accuracy. The best counting statistics were obtained for Ag. For 10-min counts, the system measures as few as 120 Ag microspheres with 30% standard deviation but measures 800 Ag microspheres per sample with 3.6% standard deviation. We compared regional myocardial blood flows determined simultaneously by fluorescence and radioactive microsphere methods; the latter samples were counted by a 3-in. NaI (Tl) well detector and pulse-height analyzer. The radioactive and nonradioactive measurements showed good correlations.

Comparison of antibody, antigen, and metabolite assays for hospitalized patients with disseminated or peripheral candidiasis

Repeat serum samples from 22 patients with proven disseminated candidiasis and 42 with simple peripheral colonization were assayed for Candida antibodies by coelectrosyneresis, immunoprecipitation, and A and B immunofluorescence, for metabolites by D-arabinitol measurement, and for antigens by the mannan immunoassay and Cand-tec latex agglutination (mean number of samples tested, 2.5 per patient). For the antibody and metabolite assays, the results showed no statistical difference between the two groups. By contrast, the results of both antigen assays were positive for a significantly larger number of patients with disseminated candidiasis than of those with simple peripheral colonization. Results were regardless of whether the patients were neutropenic. They were not predictive of death. We calculated that the mannan antigen assay had 29% sensitivity and 97% specificity for the diagnosis of disseminated candidiasis. Likelihood ratios of a positive and a negative result of this test were 9.2 and 0.7, respectively, for this diagnosis. In the latex agglutination test, likelihood ratios were 2.5, 1.5, 1.6, and 0.3 when the test was positive for dilutions of 1/8, 1/4, and 1/2 and was negative, respectively.

Modulation of Spontaneous Brain Activity during Mental Imagery

Magnetic measurements of average power of human alpha and beta activity over the occipital and parietal areas of the scalp reveal spatially selective suppression of the activity of the occipital cortex when abstract figures are briefly presented visually and subjects simply indicate that they saw the figure. However, the duration of the suppression increases markedly when subjects must indicate whether or not they had previously seen the figure. The reaction time is similarly prolonged during the search of visual memory, and is commensurate with the duration of selective suppression of brain activity. It is also demonstrated that alpha activity is not replaced by beta activity during this suppression, but that power in the beta band is also diminished during memory search. Low correlations between the scalp distributions of power in the beta and alpha bands indicate that partly different neuronal populations give rise to activity of these different frequency bands. Since magnetic fields are negligibly affected by intervening bone tissues, dramatic asymmetries in the distribution of alpha activity across the scalps of individuals and the differences in distribution between individuals cannot be ascribed to differences in skull thickness but are due instead to differences in underlying brain anatomy or function. Nevertheless, a common pattern of suppression of alpha activity is observed across subjects during well-controlled cognitive tasks. This implies that the visual system is involved in mental imagery.

Oblique reformatting of multislice magnetic resonance images for improved visualization of coronary arteries

A technique for reformatting multislice magnetic resonance images into arbitrary oblique planes has been developed and implemented on a Toshiba MRT-35 (formerly Diasonics MT/S) imaging system (South San Francisco, CA). This method is designed to allow the user to easily define a new plane by marking with a cursor features of interest on two or three different image levels. These features are combined in the resulting oblique image. The reformatted image can have arbitrary angulation and is created with a pixel dimension equivalent to the original data set. Resolution ranges from the original in-plane resolution to the slice thickness, depending on angulation. An improvement in signal-to-noise ratio results from the effective averaging performed by interpolation. This method is optimally used to correct for small variations in alignment, such as the positioning of the intervertebral disks. It can also be used to generate reformatted images at many different angles from a single multislice data set. This method has been applied to the particular problem of improving the presentation of coronary arteries on a conventional set of multislice spin-echo cardiac images by increasing the visible length of individual coronary segments.

Collaborative evaluation of antigen detection by a commercial latex agglutination test and enzyme immunoassay in the diagnosis of invasive candidiasis

The Cand-Tec Candida detection system and enzyme immunoassay for serum mannan were retrospectively compared in a controlled collaborative evaluation of antigen detection in 32 patients with candidiasis proven by biopsy or culture from a normally sterile site and with sera drawn within 7 days of inclusion. With a threshold titer of 1/8, which excluded false-positive results in 17 hospitalized patients without candidiasis, sensitivities for all 32 patients with candidiasis were 44% for the Cand-Tec assay and 17% for the enzyme immunoassay. Both assays provided greater sensitivity when sera were drawn within 24 h of inclusion in the study and in the category of patients with invasive candidiasis (57% by Cand-Tec and 33% by enzyme immunoassay). The Cand-Tec assay gave false-positive results (titer, greater than or equal to 1/8) in 4 of 6 patients with transient candidemia, in 1 of 20 otherwise healthy patients with rheumatoid factor, and in 1 patient with a positive cryptococcal latex agglutination test. Three serum specimens from 3 of 32 patients with candidiasis contained rheumatoid factor and gave titers of greater than or equal to 1/8 by the Cand-Tec assay. Detection of serum mannan by enzyme immunoassay was less sensitive but more specific than the Cand-Tec Candida detection system for the diagnosis of invasive candidiasis.

Evolution of neuromagnetic topographic mapping

Magnetoencephalography has developed during the past twenty years with a different overall emphasis than found in electroencephalography. These differences are explored in selected applications. One dominant feature of magnetic studies is a quantitative approach to characterize the strength of neuronal activity, as well as its position within the brain. There is evidence from recent analyses of current source-density measurements in animal models that the deduced peak neuronal strength can also be interpreted in terms of the spatial extent of activity across cortex.

Safety, pharmacokinetics and efficacy of once-a-day netilmicin and amikacin versus their conventional schedules in patients suffering from pelvic inflammatory disease

The safety, pharmacokinetics and efficacy of one daily injection (qd) of amikacin (AK) and netilmicin (NT) was compared with the recommended schedules (cs), i.e. twice-daily or thrice-daily, respectively. Women (17-43 years, n = 78) suffering from pelvic inflammatory disease were randomly assigned to qd or cs of either AK (14 mg/kg per day) or NT (6.6 mg/kg per day). Biometric parameters were similar in the 4 groups and all patients received ampicillin (4 g/day) and tinidazole (0.8 g/day). The Repeated Measures Analysis of Variance was used to distinguish the effects of the schedules and of the drugs choice on critical parameters. Efficacy was similar in the 4 groups and not influenced by the schedule of administration. No significant differences in nephro- and oto-toxicity were observed as assessed by serum creatinine and losses of hearing at low frequencies, but early phospholipiduria and auditory losses at high frequencies were significantly reduced with the qd administration compared to cs and by AK compared to NT. These data suggest that the qd schedule of AK and of NT is as efficacious as their cs schedules, and causes less renal and auditory alterations.

Characterization of Cryptococcus neoformans capsular glucuronoxylomannan polysaccharide with monoclonal antibodies

Mice were immunized with Cryptococcus neoformans serotype A capsular glucuronoxylomannan (GXM) conjugated to bovine serum albumin-adipic dihydrazide. Two splenocyte fusions yielded two monoclonal antibodies (MAbs) that were highly reactive in dot enzyme immunoassay, immunofluorescence, and sandwich enzyme immunoassay. The first MAb, BD-1 [immunoglobulin G1 (kappa) [IgG1(kappa)]], was GXM-A and GXM-D specific, whereas the second MAb, BA-4 (IgM), reacted with GXM-A and GXM-B. A third MAb, CD-6 [IgG1(kappa)], originated from mice immunized with O-deacetylated GXM-C-bovine serum albumin and reacted with GXMs of all four serotypes. Two of the MAbs (CD-6 and BD-1) were further characterized with chemically modified GXMs. Removal of glucuronosyl residues completely inhibited the binding of both MAbs, implicating (1----2)-beta-glucuronic acid as a key component of the epitope. Removal of (1----2)-beta-xylosyl residues decreased reactivity to an intermediate extent. O deacetylation led to a measurable decrease but had the least inhibitory effect of the three GXM derivatives tested. The combining site for these two MAbs appears to be a complex antigenic determinant involving more than one glycosidic residue.

Physics of thin-section MR imaging at low field strength

Thin-section magnetic resonance imaging at low field strengths requires analysis of the relative merits of data collection techniques for direct three-dimensional versus multisection two-dimensional imaging. This analysis was done with specific emphasis on shortened relaxation times and the use of reduced magnetic field gradients. Three-dimensional Fourier transform techniques can provide thin-section images of good diagnostic quality when combined with partial flip-angle gradient-reversal techniques.

Measuring signal-to-noise ratios in MR imaging

The signal-to-noise ratio (S/N) in magnetic resonance imagining is one of the variables that must be measured when comparing the relative performance of different techniques. Although various investigators and official groups have proposed different methods for measuring S/N, these are generally not practical for use by a physician working in a clinical situation. The authors present a simple method that should serve for estimating S/N in most cases.

The Budd-Chiari syndrome caused by a zygomycete. A new pathogenesis of hepatic vein thrombosis

The clinical history of a 60-year-old woman suffering from chronic lymphocytic leukemia with sudden deterioration and death is reported. The postmortem macroscopic and microscopic findings included pulmonary aspergillosis and pulmonary zygomycosis (mucormycosis). Hematogenous dissemination of the zygomycete causing cardiac zygomycosis, cerebral infarcts due to vascular occlusion by hyphae, and thrombosis of the major hepatic veins (Budd-Chiari syndrome) with submassive necrosis of the right liver lobe were also observed. To our knowledge, this is the second report dealing with occlusion of the hepatic veins caused by a fungus and the first study reporting the Budd-Chiari syndrome due to a mold of the subclass Zygomycetes.

Accessible magnetic resonance imaging

The cost of magnetic resonance imaging (MRI) is driven by magnetic field strength. Misperceptions as to the impact of field strength on performance have led to systems that are more expensive than they need to be. Careful analysis of all the factors that affect diagnostic quality lead to the conclusion that field strength per se is not a strong determinant of system performance. Freed from the constraints imposed by high-field operation, it is possible to exploit a varied set of opportunities afforded by low-field operation. In addition to lower costs and easier siting, we can take advantage of shortened T1 times, higher contrast, reduced sensitivity to motion, and reduced radiofrequency power deposition. These conceptual advantages can be made to coalesce onto practical imaging systems. We describe a low-cost MRI system that utilizes a permanent magnet of open design. Careful optimization of receiving antennas and acquisition sequences permit performance levels consistent with those needed for an effective diagnostic unit. Ancillary advantages include easy access to the patient, reduced claustrophobia, quiet and comfortable operation, and absence of a missile effect. The system can be sited in 350 sq ft and consumes a modest amount of electricity. MRI equipment of this kind can widen the population base than can access this powerful and beneficial diagnostic modality.

Indirect enzyme-linked immunosorbent assay for zygomycosis

A 2-h indirect enzyme-linked immunosorbent assay (ELISA) using homogenate antigens of Rhizopus arrhizus and Rhizomucor pusillus was developed and compared with the existing immunodiffusion (ID) test for zygomycosis, using homogenate antigens of R. arrhizus. Utilizing 1:400 as a minimally positive ELISA titer, 33 of 43 proven cases of zygomycosis were diagnosed. The sensitivity of the ELISA was 81%. The ID test, in contrast, detected only 21 cases and demonstrated a sensitivity of 66%. The specificity of the ELISA was 94%, whereas that of the ID test was 91%. Nonspecific ELISA reactivity was particularly evident with sera from patients with aspergillosis and candidiasis. With the antigens now available, the ELISA was unable to generically or specifically identify the etiologic agents.

Deoxyribonucleic acid hybridization studies of Exophiala dermatitidis and Exophiala jeanselmei

Exophiala dermatitidis and Exophiala jeanselmei share similar morphological features and have been confused with each other. To clarify the relationship between the two fungi, we conducted a deoxyribonucleic acid (DNA)-DNA hybridization study using a dot blot method. Between E. dermatitidis and E. jeanselmei, only a very low level of DNA relatedness was seen and it was confirmed that these two fungi are distinct species based on DNA similarity. Close correspondence of DNA from the isolates of E. dermatitidis was obtained, whereas the isolates of E. jeanselmei were divided into 6 groups according to their DNA similarity and a possibility was shown that E. jeanselmei is composed of genetically heterogeneous groups. The subdivision of the species E. jeanselmei by the DNA-DNA hybridization method was in agreement with serotyping exoantigens. This result suggests that DNA-DNA hybridization studies provide an excellent tool for the identification and grouping of pathogenic dematiaceous fungi.

Identification of aortic thrombus by magnetic resonance imaging

The unique properties of magnetic resonance imaging result in the potential to differentiate various components of the diseased arterial wall. In this article four cases are presented in which magnetic resonance imaging showed mural aortic thrombus and its anatomic relationship to the visceral and renal arteries. Once thrombus is identified and localized specific operative strategies can be undertaken to prevent recurrent embolic events and/or avoid perioperative thromboembolic complications.

Sporothrix schenckii var luriei as the cause of sporotrichosis in Italy

The second known case of sporotrichosis caused by Sporothrix schenckii var. luriei in a patient living in Piacenza, Italy is described. In the absence of cultures, the diagnosis was based on histologic studies. Stained tissue sections (Hematoxylin and eosin, & Gomori methenamine silver) revealed hyaline, large, thick walled tissue form cells that had divided by septation or a budding process. These forms, along with the striking "eyeglass" configuration of incompletely separated cells that were also present, are the diagnostic features of this apparently rare variety. The use of a fluorescent antibody reagent, specific for S. schenckii, confirmed the identity of the etiologic agent.

The regulation of immunoglobulin production by B cells in patients with endometriosis

Nineteen patients with endometriosis and 26 control infertile patients were included in the study. All patients were undergoing laparoscopy as part of their infertility evaluations. The study was conducted on sterile heparinized peripheral blood and peritoneal fluid. The age range was 20 to 37 years for both groups. Mononuclear cells were isolated on Ficoll-hypaque density gradients. T cells, B cells, and T cell subsets were identified by the specific immunobead rosette technique. Mononuclear cells 1 x 10(6) were cultured in Roswell Park Memorial Institute medium and stimulated in the presence or absence of pokeweed mitogen. Immunoglobulin production was measured by an enzyme-linked immunosorbent assay. Increased amounts of immunoglobulin (Ig) IgG and IgA were demonstrated in the peritoneal cell cultures (P less than 0.05), whereas peripheral blood cell cultures showed only an increase in IgG in patients with endometriosis (P less than 0.05). There was an increase in the number of T cells, B cells, and the ratio of CD4/CD8 lymphocytes in endometriosis compared with control patients (P less than 0.005) in both peritoneal fluid and peripheral blood. This study suggests that immunoglobulin production by the "activated" B cells may be regulated by the increased presence of T cells, specifically the helper cells (CD4) in endometriosis.

"Angiography" by magnetic resonance imaging: detailed vascular anatomy without ionizing radiation or contrast media

Using software to transform magnetic resonance imaging (MRI) tomographic data into three-dimensional projections, we have produced "angiograms" of the abdominal aorta in 18 patients with occlusive (15) and aneurysmal (3) disease. This information may be displayed to demonstrate flow, cross-sectional diameter, or aortic surface anatomy. To test the accuracy of the MRI studies, we compared them at selected points with the transected aorta and with routine aortograms. Relative cross-sectional diameter estimated by MRI was within 15% of measured aortic diameter in 14 of the 18 vessels and enabled correct detection of thrombus in 16. We conclude that MRI may accurately image the diseased abdominal aortic wall. In addition, an angiographic display format may aid in the interpretation of these studies. Although MRI is not likely to replace aortography, it could be used adjunctively to define aortic wall thickness and the presence of thrombus.

Hepatic neoplasia: breath-hold MR imaging

Twenty-seven patients with hepatic neoplasms were prospectively examined at 0.35 T with multisection magnetic resonance (MR) imaging during a single breath hold. The procedures included a spin-echo (SE) sequence with a repetition time (TR) of 250 or 125 msec and an echo time (TE) of 15 msec (TR/TE = 250 or 125/15) and gradient-echo (GRE) partial-flip sequences at 250 or 125/20 in phase and 250 or 125/12 out of phase (flip angle of 70 degrees). These procedures were compared with conventional multiacquisition sequences at SE 250/15 (n = 8) in the same patients. GRE partial-flip sequences with a large flip angle provided the optimum combination of contrast and signal-to-noise ratio for imaging hepatic neoplasms, with a signal-difference-to-noise ratio that for in-phase images was 93% greater and for out-of-phase images was 53% greater than that of the SE images. The use of in-phase TEs was preferable to maintain tissue contrast, and presaturation pulses were employed to eliminate vascular pulsation artifacts. All breath-hold procedures provided suppression of motion artifacts superior to that of the short TR, short TE multiacquisition SE imaging. Such sequences should become indispensable for MR imaging of the upper abdomen.

Advances in neuromagnetic instrumentation and studies of spontaneous brain activity

Rapid progress in neuromagnetic technology has been achieved during the past two years with the introduction of a method for accurately indicating magnetic sensor locations with respect to a head-based coordinate system and the advent of refrigerator-cooled sensors and larger arrays of sensors. These make possible the real-time monitoring of evoked activity at several widely separated locations over the scalp, thus revealing sequential activity in, e.g., sensory-motor tasks. Arrays of magnetic sensors also provide sufficient information to locate the sources of spontaneous activity, such as alpha rhythm. The locations of discrete generators (alphons) of individual alpha spindles is now possible with an array of 14 sensors. Mapping techniques with a 5-sensor system have revealed preferential suppression of alpha activity within certain regions of the occipital lobe to tasks involving mental comparisons of abstract figures. These studies provide evidence that the machinery of visual cortex is involved in mental imagery.