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PubMed1994

Imaging of mediastinal foregut cysts.

This study was undertaken to determine the value of magnetic resonance imaging (MRI) in the diagnosis of mediastinal foregut cysts. The MRI scans of 56 patients (with a total of 57 mediastinal masses) were reviewed. The patients (26 women and 30 men) had been examined between March 1986 and April 1991 at a tertiary-care hospital. T1-weighted and T2-weighted spin-echo images were available in all cases. The signal intensity of the lesions was compared with that of normal fat and muscle; the size, shape and location of the mediastinal masses were also noted. The 57 lesions consisted of 15 lymphomas, 10 neurogenic tumours, 10 thyroid masses, 6 thymomas, 6 foregut cysts and 10 other masses. Forty-eight of the masses had a signal intensity similar to that of muscle in T1-weighted images and higher than, equal to or lower than that of fat in T2-weighted images. Nine of the masses appeared bright in T1-weighted images, and the signal intensity was less than or equal to that of fat. Of these, four were foregut cysts and five were lymphomas. Of the six foregut cysts, four had short T1 values (the signal intensity ratio for cyst to fat ranging from 0.78 to 0.98) and long T2 values; two had the characteristic appearance usually associated with cystic lesions containing serous fluid--long T1 and T2 values. All of the foregut cysts appeared to be of soft-tissue attenuation on computed tomography (CT), all were located in the middle or posterior mediastinum, and all were round or oval.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1996

[The prospects for the use of computers in dentistry].

A universal soft-art complex tentatively named Arm-Stomatolog, covering all sections of dentistry, has been developed. It is based on individual programs in dentistry, making use of high-level algorithmic languages fitted to modern operation systems and permitting block-to-block fitting of individual programs to unite them in a complex.

Algorithms↗
PubMed1995

Computational properties of self-reproducing growing automata.

Living organisms perform much better than computers at solving complex, irregular computational tasks, like search and adaptation. Key features of living organisms, identified in the paper as a basis for their success in solving complex problems, are: self-reproduction of cells, flexible framework, and modification. These key features of living organisms are abstracted into a computational model, called growing automata. Growing automata are suited for extremely large computational problems, such as search problems. Growing automata are representatives of soft machines. Soft machines can change their physical structure as opposed to hard machines which have fixed structure. An example of a soft machine is a living organism, an example of a hard machine is an electronic computer. The computational properties of soft and hard machines are analyzed and compared. An analysis of growing automata demonstrates their advantages, as well as their limitations as compared to hard machines.

Computer Simulation↗
PubMed1989

Tooth positions in the natural and complete artificial dentitions, with special reference to the incisor teeth: an interactive on-line computer analysis.

A comparison of tooth positions and soft tissue profiles was made between samples of edentulous patients recently provided with new complete dentures, and dentate subjects. The dentures were marked with lead foil on the most prominent incisor teeth and labial surfaces of the flanges. Lateral skull radiographs were made with the jaws in centric relation. The dentate subjects were recorded with the teeth held in centric occlusion. Discrete soft and hard tissue landmarks were identified and recorded using an interactive on-line computer system, enabling linear and angular measurements to be made. A mathematical comparison was produced employing a series of independent t-tests. Composite computer tracings were also produced. Important differences were found between the two groups, in which the influence of the upper lip length, mandibular resorption, and selected overbite were identified as factors determining artificial tooth position.

Adult↗
PubMed2006

Elongated eccentric soft coronary plaque: major diagnostic pitfall on quantitative coronary angiography overpowered by computed tomography coronary angiography and intravascular ultrasound.

We describe a significant left anterior descending coronary lesion in a patient with unstable angina pectoris. This lesion was erroneously underestimated using quantitative coronary angiography; however, CT coronary angiography correctly showed a significant, elongated, eccentric, soft plaque that was later confirmed by repeated quantitative coronary angiography with intravascular ultrasound. As showed, CT coronary angiography may offer a reliable non-invasive alternative to quantitative coronary angiography and intravascular ultrasound by enabling a true 3-D coronary lumenogram combined with plaque detection and characterization.

Angioplasty, Balloon, Coronary↗
PubMed2000

Imaging of soft-tissue tumors using L-3-[iodine-123]iodo-alpha-methyl-tyrosine single photon emission computed tomography: comparison with proliferative and mitotic activity, cellularity, and vascularity.

The radiolabeled amino acid L-3-[123I]-iodo-alpha-methyltyrosine (IMT) is a new tumor tracer that accumulates in many tumors and is suitable for single photon emission computed tomography (SPECT) imaging. Using IMT SPECT, we studied 32 patients with a soft-tissue tumor suspected to be a soft-tissue sarcoma to determine whether: (a) tumors can be visualized; (b) benign and malignant lesions can be distinguished; and (c) IMT uptake is related to tumor grade and proliferation. Whole-body imaging was performed 15 min after administration of 300 MBq IMT, biopsy, or resection 1-2 weeks later. IMT uptake was quantified using a region-of-interest method resulting in tumor:background (T:B) ratios. These were compared with tumor grade, mitotic index, tumor cellularity, vascularity, and the Ki-67 proliferation index. Eleven patients had a benign tumor, and 21 patients had a soft-tissue sarcoma. Six benign tumors demonstrated minor IMT uptake, and five lipomas had no uptake. All malignant tumors had high uptake and were clearly visualized. T:B ratios in malignant tumors (3.83 +/- 1.16) were higher (P < 0.001) than in benign tumors (1.52 +/- 0.60). Small (<5 mm) metastases in two patients were not detected. Taking the T:B ratio 2.0 as the cutoff level, the sensitivity for detection of malignancy was 100%, and specificity was 88%. IMT uptake correlated with histological grade (r = 0.82; P < 0.001), mitotic index (r = 0.75; P < 0.001), tumor cellularity (r = 0.73; P < 0.01), and with the Ki-67 proliferation index (r = 0.63; P < 0.01). In conclusion, IMT SPECT visualized all soft-tissue sarcomas. Uptake in sarcomas was clearly higher than in benign lesions, yielding 100% sensitivity for detection of malignancy at 88% specificity. Uptake increased with higher tumor grade and higher proliferation rate.

Adolescent↗
PubMed1989

Otologic manifestations of Langerhans' cell histiocytosis.

Eighteen of 62 children diagnosed with Langerhans' cell histiocytosis at the Children's Hospital of Pittsburgh (Pa) between 1970 and 1986 demonstrated ear and temporal bone involvement. In six children, such otologic disease was their sole presenting manifestation. Common signs and symptoms included aural discharge, postauricular swelling, and conductive hearing loss. The otologic findings in these children, if not investigated properly, could easily be attributed to acute or chronic infectious ear disease. Computed tomography with contrast enhancement proved to be particularly valuable as a diagnostic study because of its clear delineation of both osseous and soft-tissue temporal bone involvement. Computed tomographic findings could also be used to enhance local treatment by guiding surgical biopsy and curettage procedures or defining low-dose radiation therapy portals. Eleven of these 18 children with otologic Langerhans' cell histiocytosis additionally required chemotherapy due to the systemic nature of their disease.

Child↗
PubMed2002

Magnetic resonance imaging of the adolescent female pelvis.

MR imaging is well suited to evaluation of the pelvis. Ultrasonography remains the study of choice for the initial evaluation of a suspected gynecologic mass. MR imaging and computed tomography remain problem-solving tools that can help to characterize masses and stage gynecologic malignancies. MR imaging has the advantage of higher soft tissue contrast compared with computed tomography. This article reviews the MR findings of congenital anomalies and masses of the adnexa and uterus in adolescent girls.

Adolescent↗
PubMed2006

Soft nanopolyhedra as a route to multivalent nanoparticles.

Computer simulations show that end-grafted immiscible homopolymers can confer multivalence to nanoparticles, resulting in soft nanopolyhedra with structures identical to those found in small clusters of colloidal microspheres. Unprecedented structure tunability is demonstrated by several structure transition sequences, including a reentrant transition, induced by varying composition, polymer lengths, or grafting patterns. These results suggest a new method for fabricating nanoparticles with precisely controlled numbers and locations of functional sites (i.e., multivalent nanoparticles).

Journal Article↗
PubMed1995

Imaging features of dissecting neuropathic joints.

The imaging appearances of three patients with variable clinical presentations of dissecting neuropathic joints are described. Plain radiographs demonstrated bony debris within the soft tissues adjacent to and distant from neuropathic joints. Computed tomography combined with arthrography confirmed that the soft tissue bony debris communicated with the joints.

Aged↗
PubMed1992

Finite element methods for the biomechanics of soft hydrated tissues: nonlinear analysis and adaptive control of meshes.

This chapter addresses computationally demanding numerical formulations in the biomechanics of soft tissues. The theory of mixtures can be used to represent soft hydrated tissues in the human musculoskeletal system as a two-phase continuum consisting of an incompressible solid phase (collagen and proteoglycan) and an incompressible fluid phase (interstitial water). We first consider the finite deformation of soft hydrated tissues in which the solid phase is represented as hyperelastic. A finite element formulation of the governing nonlinear biphasic equations is presented based on a mixed-penalty approach and derived using the weighted residual method. Fluid and solid phase deformation, velocity, and pressure are interpolated within each element, and the pressure variables within each element are eliminated at the element level. A system of nonlinear, first-order differential equations in the fluid and solid phase deformation and velocity is obtained. In order to solve these equations, the contributions of the hyperelastic solid phase are incrementally linearized, a finite difference rule is introduced for temporal discretization, and an iterative scheme is adopted to achieve equilibrium at the end of each time increment. We demonstrate the accuracy and adequacy of the procedure using a six-node, isoparametric axisymmetric element, and we present an example problem for which independent numerical solution is available. Next, we present an automated, adaptive environment for the simulation of soft tissue continua in which the finite element analysis is coupled with automatic mesh generation, error indicators, and projection methods. Mesh generation and updating, including both refinement and coarsening, for the two-dimensional examples examined in this study are performed using the finite quadtree approach. The adaptive analysis is based on an error indicator which is the L2 norm of the difference between the finite element solution and a projected finite element solution. Total stress, calculated as the sum of the solid and fluid phase stresses, is used in the error indicator. To allow the finite difference algorithm to proceed in time using an updated mesh, solution values must be transferred to the new nodal locations. This rezoning is accomplished using a projected field for the primary variables. The accuracy and effectiveness of this adaptive finite element analysis is demonstrated using a linear, two-dimensional, axisymmetric problem corresponding to the indentation of a thin sheet of soft tissue. The method is shown to effectively capture the steep gradients and to produce solutions in good agreement with independent, converged, numerical solutions.

Adaptation, Physiological↗
PubMed1989

Computed tomography as a diagnostic aid in diabetic and other problem feet.

Determining whether osteomyelitis is present in patients with foot infections represents a significant diagnostic challenge. As bone uptake with nuclide scans can be affected by soft tissue infection, we performed computed tomography (CT) on seven patients to see if marrow or bone abnormalities could be seen and used to predict the presence or absence of osteomyelitis. The CT scans correctly predicted the presence or absence of osteomyelitis in all seven patients. Four patients had osteomyelitis and three patients did not. Nuclide bone scans had one false-positive and one false-negative result. In this small series, CT proved helpful in evaluating foot problems.

Adult↗
PubMed2006

Risk factors associated with soft coronary artery plaques in Japanese, as determined by 16 slice multidetector-row computed tomography.

PURPOSE: The acute coronary syndrome is often caused by the rupture of plaques and thrombus formation even without significant stenosis, and patients with soft plaques, but without significant stenosis evidenced by coronary angiography (CAG), often develop an acute coronary syndrome. To address this discrepancy, a qualitative diagnosis of coronary plaques using a 16 slice multidetector-row CT was conducted. METHODS AND RESULTS: Volume rendering and cross-sectional MPR images were obtained. Based on the CT values, plaques on the coronary artery wall were classified as lipid-rich soft plaques (CT value<50 HU) and non-soft plaques (>50 HU).A significant correlation was observed between the percent stenosis determined in cross-sectional MPR images and those determined by CAG (r=+0.92, p<0.01). Diffuse plaques with CT values of less than 50 HU often caused stenosis at level of 75% or less, which were not indicated by percutaneous transluminal coronary angioplasty. CONCLUSIONS: Although diffuse soft plaques with CT values less than 50 HU are not an indication of intervention, a risk of an acute coronary syndrome exists, due to rupture. These soft plaques must be stabilized by treatment even when they do not cause significant stenosis, and MDCT is considered to be useful for their evaluation.

Aged↗
PubMed1991

Digital imaging with a photostimulable phosphor in the chest of newborns.

To evaluate use of a digital photostimulable phosphor imaging system in the neonatal nursery, 150 newborns were divided into three groups of 50. In the first two groups, screen-film and computed radiographs of the chest were obtained at the same radiation exposure; in the third group, computed radiographs were obtained with a 50% dose reduction (half-exposure computed radiographs). All images were blindly evaluated by three readers who scored the quality of visualization of the mediastinum, lung, bone, soft tissues, and endotracheal and nasogastric tubes, and also image density. No statistical differences in visualization of tubes existed among the three groups. Visualization of the mediastinum, lung, bones, and soft tissues was statistically significantly better on computed radiographs than on half-exposure computed radiographs; visualization of the lungs, bones, and soft tissues was statistically significantly better on screen-film radiographs than half-exposure computed radiographs. Image density was statistically better on computed and half-exposure computed radiographs than on screen-film radiographs.

Humans↗
PubMed1996

Conformal treatment planning for interstitial brachytherapy.

PURPOSE: Quality of a brachytherapy application depends on the choice of the target volume, on the dose distribution homogeneity and radiation injury on critical tissue, which should be postulated by advanced brachytherapy treatment planning systems. MATERIAL AND METHODS: Basic imaging method for conformal treatment planning is the cross-sectional imaging. The clinical applicability of a new type 3D planning system using CT and/or MRT-simulation or US-simulation for planning purposes was studied. The planning system developed at Kiel University differs from usual brachytherapy planning systems because of the obligatory use of cross-sectional imaging as basic imaging method for reconstruction of structures of interest. Dose distribution and normal anatomy can be visualized on each CT/MRT/US slice as well as coronal, sagittal, axial and free chosen reconstruction (3D), as well as dose-volume histogram curves and special colour-coded visualization of dose homogeneity in the target can be analyzed. RESULTS: Because of the experience in the clinical routine, as well as on the base of 30 simultaneous planning procedures on both 2D (semi-3D) and 3D planning systems we observed similar time consumption. Advantages of 3D planning were the better interpretation of target delineation, delineation of critical structures as well as dose distribution, causing more accurate volume optimisation of dose distribution. CONCLUSION: Conformal brachytherapy treatment planning for interstitial brachytherapy means significant advantages for the clinical routine compared to 2D or semi-3D methods.

Algorithms↗
PubMedDate not supplied

Neurothekeoma in the upper extremity: magnetic resonance imaging and computed tomography findings.

Neurothekeomas are rare benign tumors of soft tissue that are of presumed neural sheath origin. This report describes the magnetic resonance imaging and computed tomography features of a neurothekeoma in the left forearm of a 38-year-old woman with a 2-year history of a painful mass. Magnetic resonance imaging showed a smooth-bordered ovoid lesion within the inner portion of the extensor digitorum muscle with a Hounsfield number of 15. The lesion had intermediate signal on T1-weighted images, high signal on T2-weighted images, and mild to moderate heterogeneous gadolinium contrast enhancement.

Adult↗
PubMed1987

Computed tomography for parotid neoplasia: a new look.

Sixty-five mass lesions of parotid origin were evaluated using thin-section high-resolution computed tomography to ascertain histologic specificity. All patients were studied after infusion of intravenous contrast media. Factors judged included the extent of glandular involvement, invasion of adjacent soft tissues, degree of postcontrast computed tomography density (relative to muscle), and the presence of calcification.

Adenolymphoma↗