Management of suppurative pylephlebitis by percutaneous drainage: placing a drainage catheter into the portal vein.

Persistent infection of the portal vein is a rare entity with significant mortality. We present two cases of infected thombis of the portal vein, one infected with fungus and the other with bacteria, both requiring percutaneous drainage to allow a response to antibiotics. The distinction between bland thrombis, infected thrombis, portal venous air, and pneumobilia will be discussed so that suppurative pylephlebitis can be recognized more easily as drain placement appears to affect a more prompt degree of improvement than antibiotics alone.

Inelastic scattering on spherical microparticles with inclusions.

The subject of the paper is scattering at spherical microparticles with inclusions. The inclusions are represented as dipoles for both elastic and inelastic scattering. For elastic scattering the dipoles are computed iteratively, and sequence transformations are used to accelerate this iteration. Mie theory is used to calculate the cross sections for scattering on spherical microparticles with inclusions as well as on agglomerates.

Cascade lasing with spherical microparticles.

Lasing characteristics of dye-doped spherical solid microparticles produced by photopolymerization in aerosols are investigated. It is well known that dielectric spherical microparticles are optical resonators with very high quality. The resonant internal field is not completely confined to the interior of the particle. An evanescent wave extends a couple of micrometers into the surrounding area. This evanescent field decays exponentially. We demonstrate that cascade lasing can be excited by coupling of two spherical microresonators through this evanescent field.

CT fluoroscopic guidance for percutaneous needle placement into abdominopelvic lesions with difficult access routes.

BACKGROUND: We wished to evaluate the utility of computed tomography fluoroscopy (CTF) for guiding percutaneous abdominopelvic biopsies or fluid aspirations that are considered difficult with conventional computed tomographic (CT) guidance. METHODS: CTF-guided percutaneous biopsy (n = 11) or fluid aspiration (n = 2) was attempted in 13 patients with lesions that were otherwise difficult or potentially unsafe by conventional CT guidance because they were deep to colon, small intestine, or major blood vessels. RESULTS: Using CTF assistance to guide external compression or needle positioning, appropriate needle placement was performed in 11 patients. Biopsy or aspiration was diagnostic in 10 patients. Needle advancement was not attempted in two patients. CONCLUSION: CTF appears to be a valuable tool to dynamically assist percutaneous needle placement into lesions that may be considered difficult with standard CT assistance.

Geometrical optics model of Mie resonances

The geometrical optics model of Mie resonances is presented. The ray path geometry is given and the resonance condition is discussed with special emphasis on the phase shift that the rays undergo at the surface of the dielectric sphere. On the basis of this model, approximate expressions for the positions of first-order resonances are given. Formulas for the cavity mode spacing are rederived in a simple manner. It is shown that the resonance linewidth can be calculated regarding the cavity losses. Formulas for the mode density of Mie resonances are given that account for the different width of resonances and thus may be adapted to specific experimental situations.

Computed tomography fluoroscopy: techniques and applications.

Computed tomography fluoroscopy (CTF) was first introduced into clinical practice in Japan in 1993 and in the United States in 1995, yet it has been used predominantly at large academic hospitals. Early literature on CTF is composed primarily of abstracts that detail anecdotal experiences and that have been presented at major meetings. Scientific papers evaluating CTF in clinical practice have been introduced in scientific journals only recently. This article reviews the literature for CTF with specific emphasis on clinical techniques, applications, and results. It is the goal of the author to provide the reader with a basic working knowledge of how to perform CTF-guided procedures and how to integrate CTF into clinical practice.

CT fluoroscopy: technique and utility in guiding biopsies of transiently enhancing hepatic masses.

We evaluated a new percutaneous biopsy technique for rapid needle localization and biopsy of transiently enhancing focal hepatic masses. Three biopsies in three patients were completed on lesions 18-22 mm in diameter by using computed tomographic fluoroscopy during intravenous contrast enhancement of the liver. All three biopsies were diagnostic.

Simultaneous In-Situ Measurement of Local Particle Size, Particle Concentration, and Velocity of Aerosols.

Photon correlation spectroscopy has been applied to the characterization of (quasi-)monodisperse aerosols. The experiments were carried out with an experimental standard pin hole setup on laminar flowing aerosols of the submicrometer particle size range. It is shown that beside local mean particle size and local aerosol velocity simultaneously the local particle number concentration may be obtained from a single measured autocorrelation function. The proposed procedure does not require calibration. It is pointed out that measurement conditions can be adapted to the properties of the aerosol to be characterized, thus allowing characterization of aerosols over a wide parameter range, e.g., it is not restricted to the case of low particle concentration. The experimental results are compared to data from literature, data from reference measurements and data from a theoretical model, respectively. The method can also be usefull for characterization of other fluid-particle systems as hydrosols. Copyright 1999 Academic Press.

Geometrical optics calculation of inelastic scattering on large particles.

A geometrical optics approximation was used for calculations of inelastic (Raman and fluorescent) scattering on particles with large size parameters. The inelastic part of the radiation was obtained by use of the principle of ray reversibility. The technique presented simplifies the computations and provides a geometric interpretation of how far-field patterns can be calculated by use of the internal field distributions. The numerical results for homogeneous spherical particles are compared with the classic dipole solution.

Optimizing contrast enhancement during helical CT of the liver: a comparison of two bolus tracking techniques.

OBJECTIVE: The purpose of this study was to evaluate a recently developed hardware and software system for CT scanning that generates images in real time and switches to helical CT scanning by either a visual cue or a region of interest (ROI) amplitude threshold. SUBJECTS AND METHODS: We randomly and prospectively divided 120 abdominal CT examinations into three groups. Two groups received 75 ml of contrast agent at 1.5 ml/sec. Helical CT scanning began after visualization of the contrast bolus arrival in the hepatic veins (visual cue triggering) (39 patients) or after reaching an ROI threshold (automated ROI threshold triggering) (39 patients). A third group served as a control group (42 patients) and received 150 ml of contrast agent at 1 ml/sec. Quality of hepatic enhancement was assessed objectively and subjectively. Comparisons were made after stratifying each group into three weight classes. RESULTS: Errors occurred in 12 (31%) of 39 examinations in the group with automated ROI threshold triggering. In that group, we found a significantly (p < .04) lower mean hepatic enhancement in two of three weight categories, and a significantly (p < .04) lower mean subjective scan quality in one of three weight categories, than we found in the group with visual cue triggering. CONCLUSION: Optimizing portal venous phase helical CT of the liver after a low-volume bolus of contrast agent and an injection rate of 1.5 ml/sec is best achieved by initiating helical CT scanning after visualizing the contrast bolus arrival within the liver rather than after reaching a preset attenuation threshold.

Postbulbar duodenal ulceration and stenosis associated with celiac disease.

The case histories of five patients with celiac disease and postbulbar duodenal ulceration and stenosis are presented. Celiac disease was unexpected in three of the five patients until endoscopic biopsy revealed villous atrophy. Our findings suggest that duodenal ulceration and stenosis may be a more common complication of celiac disease than previously thought and may precede the clinical diagnosis of celiac disease or occur when there are minimal symptoms and nonspecific radiographic findings for the disease.

Teaching physical examination of the adult liver with use of real-time sonography.

RATIONALE AND OBJECTIVES: The authors developed and evaluated an approach to teaching examination of the liver that incorporates real-time ultrasound (US) imaging as immediate feedback to improve diagnostic accuracy. MATERIALS AND METHODS: Second-year medical students participating in a course in physical examination were assigned to receive instruction in measuring liver span without (group 1) or with (group 2) real-time sonography. Students from each group attended a practice session given by one of two physicians who were board certified in radiology and internal medicine with special expertise in US. During the practice session for group 2, students were shown the boundaries of the liver of the practice patient with real-time US. Both groups of students then made three measurements each of the liver span of a healthy practice patient and a single healthy test patient without US. The vertical liver span reference standard was determined by one of the authors. RESULTS: Students in group 2 showed greater accuracy in measuring liver span during both the practice and the test sessions than did students in group 1. The differences were significant for the third practice measurement and all three test measurements (P < .05). CONCLUSION: The use of real-time US as an aid in teaching physical examination improves students' accuracy in measuring liver size.

An iterative algorithm for X-ray CT fluoroscopy.

X-ray computed tomography fluoroscopy (CTF) enables image guidance of interventions, synchronization of scanning with contrast bolus arrival, and motion analysis. However, filtered backprojection (FB), the current method for CTF image reconstruction, is subject to motion and metal artifacts from implants, needles, or other surgical instruments. Reduced target lesion conspicuity may result from increased image noise associated with reduced tube current. In this report, we adapt the row-action expectation-maximization (EM) algorithm for CTF. Because time-dependent variation in images is localized during CTF, the row-action EM-like algorithm allows rapid convergence. More importantly, this iterative CTF algorithm has fewer metal artifacts and better low-contrast performance than FB.

Controlled modification of the expansion order as a tool in mie computations.

In the framework of Mie theory the involved electromagnetic fields are expanded in an infinite series of multipoles. In numerical computations the summation has to be terminated after a finite number of terms (the expansion order N), which unavoidably produces errors. On the other hand, it is known that the contributions of terms of order l with x

Photon correlation spectroscopy on flowing polydisperse fluid-particle systems: theory.

We develop an analytical expression for the homodyne autocorrelation function of laser light scattered by a laminar flow of a polydisperse particle-fluid system. In contrast to the already existing literature on the development of autocorrelation functions, we explicitly begin with the effects of the finite linewidth of the light source, the spatial and temporal intensity averaging that is due to the detection process, the Brownian particle movement on the amplitudes of the scattered light waves as well as on the degree of resolution that we introduce in this paper, and a general system velocity v = (v(x), v(y), v(z)). One main result is a new physical interpretation of the well-known, generally empirically introduced coherence factor. Quantities that are comparable to the well-known degree of coherence, coherence area, and number of coherence areas have also been obtained. Finally the investigations are simplified to an autocorrelation function that can be used for the analysis of fluid-particle systems in the low Knudsen number regime. It is shown that in this case particle size or size distribution, system velocity, and particle concentration can be obtained simultaneously. The developed autocorrelation function is related to frequently analyzed special cases and compared with expressions from the literature.

Resonance shift of obliquely illuminated dielectric cylinders: geometrical-optics estimates.

Some characteristics of resonant states in obliquely illuminated cylinders are derived from a geometrical-optics point of view. A formula for the resonance shift that is due to tilted illumination is derived and predictions are compared with data from the literature.

Electrodynamic Trapping of Aerocolloidal Particles: Experimental and Theoretical Trapping Limits

Aerocolloidal particles have been trapped from an uncharged source aerosol using an electrodynamic balance. Graphite and soot particles were charged photoelectrically using a Xe2 (172 nm) excimer lamp, while particles of titanium dioxide, sodium nitrate, and diethylhexyl sebacate (DEHS) were charged using a unipolar corona charger prior to injection into the chamber. It was found that the Stokesian drag force produced by convection in the balance chamber can destabilize the levitated microparticle when it exceeds the electrostatic force required to center the particle. Although the electrostatic restoring force can be increased by increasing either the particle charge or the ac field strength, charging of the particles is more difficult as the particle diameter is decreased, which gives rise to a trapping limit. Monodisperse DEHS particles were used to determine the experimental trapping limit for unipolar charging. For the experimental apparatus used in this study, a diameter of about 1 µm was found to be the trapping limit for DEHS. Results are compared to the theoretical trapping limit calculated by a force balance on a particle exposed to motion of the surrounding gas.

Pediatric radiology at a rural hospital: value of teleradiology and subspecialty consultation.

OBJECTIVE: We performed a field study and subsequent laboratory investigation of pediatric radiology at a small rural hospital. Our investigation had three components: to describe the characteristics of pediatric radiology in a rural primary care facility, to test the diagnostic accuracy of interpretation of pediatric images transmitted by teleradiology, and to compare relative diagnostic accuracy of general and pediatric radiologists who interpreted pediatric images at a rural institution. MATERIALS AND METHODS: All 196 pediatric radiographs obtained during a 4-month period comprised the database from which we determined practice characteristics. Reports of 153 unselected cases interpreted by general radiologists using teleradiology were compared with interpretation of the same cases by a pediatric radiologist who interpreted the original radiographs. Discrepant cases were further investigated by a receiver-operating-characteristic curve experiment in which general and pediatric radiologists interpreted each case twice: once viewing teleradiologic images and once viewing the original radiographs at another setting. We then compared interpretive accuracy of observers and techniques. RESULTS: The pediatric radiographs were predominantly simple examinations for common acute disease, particularly pneumonia and fractures. Discrepancies of interpretation between teleradiology and original radiographs, which occurred in 13% of images, showed no significant difference in accuracy of interpretation for either teleradiologic images or original radiographs. Likewise, we found no significant advantage for accuracy of interpretation by general or pediatric radiologists. Receiver-operating-characteristic analysis of 18 discrepant cases showed slightly increased accuracy for interpretation of original radiographs by pediatric subspecialists. CONCLUSION: Simple pediatric radiographs obtained at a rural primary care institution and transmitted by teleradiology can be adequately interpreted by general radiologists.

Accuracy of color Doppler sonography in assessing venous thrombus extension in renal cell carcinoma.

OBJECTIVE: Our objective was to evaluate the accuracy of color Doppler sonography for assessing tumor thrombus extension into the renal veins, the inferior vena cava, and the right side of the heart in patients with renal cell carcinoma. MATERIALS AND METHODS: Over the past 4.5 years, 44 patients with 46 renal cell carcinomas were examined with color Doppler sonography for the presence and extent of tumor thrombus in the renal veins, the inferior vena cava, and the right side of the heart. Examinations were performed after an equivocal CT scan in 34 patients and as a primary imaging technique in 10. Color Doppler sonographic findings were correlated with surgical-pathologic findings or findings from autopsies performed within 3 months of the Doppler study. Seven patients were excluded: two because of poor technical quality caused by body habitus and five because pathologic correlation was performed more than 3 months after the color Doppler sonographic examination. The remaining 39 renal vein and 37 caval Doppler examinations constituted the study material. Criteria used for the diagnosis of tumor thrombus included distention of the renal vein or the inferior vena cava by echogenic material and partial or complete absence of flow detected with color Doppler sonographic examination. RESULTS: Sixteen of 39 renal veins evaluated had pathology-proven tumor thrombus. Color Doppler sonography was 87% accurate with a sensitivity of 75%, a specificity of 96%, a positive predictive value of 92%, and a negative predictive value of 85%. In two false-positive cases, involvement was limited to intrarenal veins, causing no change in the surgical approach. Five of 37 inferior venae cavae evaluated had proven involvement by tumor thrombus. Color Doppler sonography was 100% accurate in assessing the presence and extent of inferior vena caval involvement by tumor thrombus. Extension into the right atrium and ventricle that was shown by this technique was proven by surgery in one case. The overall accuracy for detecting venous involvement for both the renal veins and the inferior vena cava was 93%, the sensitivity was 81%, and the specificity was 98%. CONCLUSION: In patients with renal cell carcinoma, color Doppler sonography appears to be fairly accurate in assessing tumor extension into the renal veins, the inferior vena cava, and the right side of the heart. Although CT is the primary imaging technique for staging renal cell carcinoma, color Doppler sonography may be used as a complementary technique for assessing venous extension in patients with an equivocal CT examination.