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At least 199 records · Page 11Linked to original sources
PubMed2003

Carbon dioxide reactivity of computed tomography functional parameters in rabbit VX2 soft tissue tumour.

Tumour blood flow is one of the important factors limiting the efficacy of radiation therapy (hypoxic radioresistance), chemotherapy (drug delivery) and thermal therapy (heat dissipation) in treating cancer. The modification of tumour blood flow has been an area of intense investigation. In the current study, the arterial carbon dioxide tension (PaCO2) was changed in order to investigate the tumour vascular response to carbon dioxide. Functional maps of blood flow, blood volume and mean transit time were generated at four PaCO2 levels in VX2 tumour in the rabbit thigh and normal soft tissue. The PaCO2 levels investigated were normocapnia (PaCO2 = 40.9 +/- 1.2 mmHg), hypocapnia (27.2 +/- 2.3 and 33.5 +/- 2.3 mmHg) and hypercapnia (54.9 +/- 4.4 mmHg). The carbon dioxide reactivity of the global tumour blood flow and mean transit time showed significant differences between normocapnia and the two levels of hypocapnia, but not between normocapnia and hypercapnia. The average fractional change of blood flow from normocapnia for the two levels of hypocapnia was -0.41 +/- 0.06 and -0.29 +/- 0.08, respectively (P < 0.05). In the case of mean transit time the fractional change was +0.39 +/- 0.30 and +0.23 +/- 0.24, respectively (P < 0.05). The fractional change of blood volume from normocapnia, however, was not significantly different at any capnic level, as was the case with respect to each of the functional parameters in normal tissue. The ability to reduce blood flow and increase mean transit time through hypocapnia has significant implications in thermal therapy, since heat dissipation is a major factor in limiting the effectiveness of treatment.

Animals↗
PubMed2001

3-D simulation of craniofacial surgical procedures.

An integrated system for simulating craniofacial surgical procedures is presented. The system computes nonlinear soft-tissue deformation due to bone realignment. It is capable of simulating bone cutting and bone realignment with integrated interactive collision detection. Furthermore, soft-tissue deformation and cutting due to surgical instruments can be visualized. The system has been tested with several individual patient data sets. Simulation processes are based on a 3-D model of a patient's preoperative bone structure of the skull derived from a computer tomography scan and on a 3-D, photorealistic model of the patient's preoperative appearance obtained by a laser range scanner. The multi-layer soft-tissue model is represented by nonlinear springs. Very fast and robust prediction of nonlinear soft-tissue deformation is computed by optimizing a nonlinear cost function.

Cephalometry↗
PubMed1986

Growth of human renal carcinoma in soft agar colony formation assays measured by computer-assisted volume analysis.

Technical methods for assessing the growth and chemotherapy sensitivity of human tumor cells growing in soft-agar culture have been less than ideal. Within the past year, there have been reports of studying the extent of growth of human tumor cells in these cultures by quantitating the change in cumulative volume for the growth units observed. The present report describes the results of computer-assisted volume analysis applied to soft-agar cultures of cells from 74 primary renal cell carcinomas, 14 primary transitional cell carcinomas of the renal pelvis, and four different human renal cell carcinoma xenografts. The extent of growth in vitro observed for cells from freshly excised human renal tumors showed the expected and statistically significant relationship to tumor grade and stage. The renal cell carcinoma xenografts proliferated to a much greater extent in vitro than the cells from freshly excised human renal carcinomas. The fundamental growth limit of 10(9) micron. cumulative growth unit volume per plate was confirmed by this series of experiments. Computer-assisted volume analysis appears to be a useful method to study the growth of freshly excised human renal carcinoma cells in vitro.

Agar↗
PubMed1994

Computer-assisted quantitative description of chromatin pattern in soft tissue tumors of the adult.

The chromatin pattern in Feulgen-stained nuclei from soft tissue tumors was quantitatively described by means of computer-assisted microscope analysis. The morphonuclear parameters described densitometric, run length, and co-occurrence matrix features. The present series of cases, which relied upon archival (ie, formalin-fixed, paraffin-embedded), tissues, included 19 benign (9 lipomas and 10 leiomyomas) cases, and 49 malignant (31 primitive non-recurrent, 14 primitive locally recurrent, and 4 metastatic) cases. The 31 primitive nonrecurrent cases included 12 liposarcomas, 11 leiomyosarcomas, 4 rhabdomyosarcomas, and 4 malignant fibrohistiocytomas. The results show that the quantitative description of chromatin patterns in Feulgen-stained nuclei made it possible to distinguish between certain benign and malignant soft tissue tumors. However, this was true only when specific histopathologic groups were taken into consideration. Indeed, the lipomas were markedly different from the liposarcomas, whereas the leiomyomas closely resembled the leiomyosarcomas. The quantitative description of the chromatin patterns also made it possible to identify certain clinically aggressive soft tissue tumors. In this context, the authors observed that the chromatin pattern in the cell nuclei from the group of patients whose tumors had recurred less than 10 months after first surgery was significantly more heterogeneous and less condensed than in the cell nuclei from patients whose tumors had recurred more than 10 months after this surgery. In the same manner, the morphonuclear parameters under study made it possible to establish a more marked distinction between the primitive and recurrent soft tissue tumors that developed a metastasis between 3 and 48 months after the diagnosis, and those tumors free of metastasis until 38 months after the diagnosis. The former group exhibited cell nuclei with a chromatin pattern markedly more condensed and heterogeneous than in the case of the cell nuclei belonging to the latter group.

Adult↗
PubMed2005

Soft annealing: a new approach to difficult computational problems.

I propose a new method to study computationally difficult problems. I consider a new system, larger than the one I want to simulate. The original system is recovered by imposing constraints on the large system. I simulate the large system with the hard constraints replaced by soft constraints. I illustrate the method in the case of a ferromagnetic Ising model and in the case of a three-dimensional spin-glass model. I show that in both models the phases of the soft problem have the same properties as the phases of the original model and that the softened model belongs to the same universality class as the original one. I show that correlation times are much shorter in the larger soft constrained system and that it is computationally advantageous to study it instead of the original system. This method is quite general and can be applied to many other systems.

Journal Article↗
PubMed1983

Soft-tissue hemorrhage in hemophiliac patients. Computed tomography and ultrasound study.

Fifty-four hemophiliac patients underwent a total of 94 studies using computed tomography (CT), ultrasound, or both. Not only common bleeding sites such as the iliopsoas muscles but also several unusual sites were encountered: these included the iliac bone, bowel wall, mesentery, rectus abdominis muscle, retroperitoneum, bladder wall, and scrotum. Both modalities gave comparable results, and each was helpful in (a) establishing the diagnosis, (b) evaluating the extent of bleeding and its effect on adjacent organs, and (c) demonstrating regression after treatment.

Abdomen↗
PubMed1984

The comparative value of bone scintigraphy and computed tomography in determining bone involvement by soft-tissue sarcomas.

In seventeen patients with a soft-tissue sarcoma, bone scintigrams were found to be more useful than computed tomograms for evaluating bone involvement. The scintigrams had higher predictive value and higher sensitivity, as there were no false-negative or false-positive scintigrams, while there were three false-positive computed tomograms. Accurate scintigraphy requires the use of high-resolution static gamma-camera images that show the tangential relationship between tumor and bone. The images that are usually made in surveying the skeleton for metastatic disease--routine whole-body bone scans, or even gamma-camera images that provide only anterior and posterior views--are inadequate. They did not demonstrate the true relationship of the tumor to bone in the patients in this study when activity within the tumor itself was superimposed over bone. In such patients, properly selected oblique views sometimes showed that the tumor was clearly separate from normal bone activity. Determination of the relationship of the soft-tissue tumor to bone is an important part of the accurate anatomical staging that is required to select appropriate surgical management.

Adolescent↗
PubMed2000

BiGGER: a new (soft) docking algorithm for predicting protein interactions.

A new computationally efficient and automated "soft docking" algorithm is described to assist the prediction of the mode of binding between two proteins, using the three-dimensional structures of the unbound molecules. The method is implemented in a software package called BiGGER (Bimolecular Complex Generation with Global Evaluation and Ranking) and works in two sequential steps: first, the complete 6-dimensional binding spaces of both molecules is systematically searched. A population of candidate protein-protein docked geometries is thus generated and selected on the basis of the geometric complementarity and amino acid pairwise affinities between the two molecular surfaces. Most of the conformational changes observed during protein association are treated in an implicit way and test results are equally satisfactory, regardless of starting from the bound or the unbound forms of known structures of the interacting proteins. In contrast to other methods, the entire molecular surfaces are searched during the simulation, using absolutely no additional information regarding the binding sites. In a second step, an interaction scoring function is used to rank the putative docked structures. The function incorporates interaction terms that are thought to be relevant to the stabilization of protein complexes. These include: geometric complementarity of the surfaces, explicit electrostatic interactions, desolvation energy, and pairwise propensities of the amino acid side chains to contact across the molecular interface. The relative functional contribution of each of these interaction terms to the global scoring function has been empirically adjusted through a neural network optimizer using a learning set of 25 protein-protein complexes of known crystallographic structures. In 22 out of 25 protein-protein complexes tested, near-native docked geometries were found with C(alpha) RMS deviations < or =4.0 A from the experimental structures, of which 14 were found within the 20 top ranking solutions. The program works on widely available personal computers and takes 2 to 8 hours of CPU time to run any of the docking tests herein presented. Finally, the value and limitations of the method for the study of macromolecular interactions, not yet revealed by experimental techniques, are discussed.

Algorithms↗
PubMed2003

Early experience with computed tomographic angiography in microsurgical reconstruction.

Preoperative angiography is frequently used in the planning of microsurgical reconstruction. However, several potentially devastating complications can result from angiography, including arterial occlusion and pseudoaneurysm. Computed tomographic angiography is a relatively new technique that can provide detailed information about vascular anatomy as well as soft and bony tissue without the risks of traditional angiography. In addition, three-dimensional image reconstruction uniquely demonstrates anatomical relationships among blood vessels, bones, and soft tissue. Fourteen computed tomographic angiograms were obtained in 10 patients undergoing microsurgical reconstruction of the head and neck, lower extremity, or upper extremity. The average patient age was 46.9 years (range, 22 to 67 years). Charges related to the computed tomographic procedure were compared with those of conventional preoperative imaging for microsurgical repair. At our institution, the average computed tomographic angiogram charge was 1140 US dollars, whereas the average charge for traditional arteriography was 3900 US dollars. When compared with intraoperative evaluation, computed tomographic angiograms demonstrated clinically relevant surgical anatomy. No complications were noted for the radiographic procedure or after free flap reconstruction. Computed tomographic angiography provides high-resolution, three-dimensional arterial, venous, and soft-tissue imaging without the risks of traditional angiogram and at a lower cost.

Adult↗
PubMed1983

Computed tomography of the middle ear in the evaluation of cholesteatomas and other soft-tissue masses: comparison with pluridirectional tomography.

Computed tomographic (CT) scans and tomograms of 60 patients with various soft-tissue masses of the middle ear, including 30 with cholesteatomas, were studied. CT produced excellent images of middle ear soft-tissue masses and appears to be the diagnostic method of choice for cholesteatomas, glomus tympanicum tumors, and other soft-tissue masses. In one patient CT demonstrated pneumolabyrinth resulting from postsurgical fracture of the footplate of the stapes. Pneumolabyrinth is a newly reported CT finding in stapes footplate fracture.

Adolescent↗
PubMed1978

Computed tomography of the paranasal sinuses and face: part I. Normal anatomy.

With the ability to image both bone and soft tissue structures, computed tomography (CT) is capable of visualizing many normal anatomical structures of the paranasal sinuses and face not seen with other radiological techniques. The superficial and deep fat planes, all of the muscles of mastication, and many of the facial muscles are readily identified. The extraocular muscles, optic nerves, and globes are clearly seen. The purpose of this report is to review the normal anatomy of the paranasal sinuses and face imaged by CT in both the transverse and coronal planes.

Face↗
PubMedDate not supplied

Orthogonal polynomials used as soft tissue energy density functions.

A mathematical method is developed for computing the coefficients of soft tissue energy density polynomials, satisfying certain constraints. The polynomial coefficients are computed in the least squares sense. It is demonstrated that this method: (a) determines up to 30 polynomial coefficients whereas the unmodified least squares method based on Maclaurin power series determines up to nine coefficients; and (b) increases numerical stability and accuracy by several orders of magnitude. All computations are carried out in single precision on a LSI-11/23 laboratory minicomputer. The algorithm is particularly useful for on-line data analysis using small laboratory computers.

Connective Tissue↗
PubMed1982

Computed tomography in the evaluation of acquired stenosis in the neonate.

We studied the feasibility of computed tomographic evaluation of the neonatal airway. Three neonatal larynges, removed at necroscopy, were examined by computed tomography. Good resolution of soft tissue, cartilage and airway lumen was obtained in these small specimens. On the basis of these findings two neonates with acquired subglottic stenosis were examined by endoscopy, soft tissue airway radiographs, and computed tomography. Measurements of radiation dose revealed that a computed tomographic study delivered 36% of the mean tissue dose of standard image intensifier fluoroscopy. Computed tomography and fluoroscopy both demonstrated the degree and length of this stenosis accurately. An advantage of CT over conventional imaging procedures was better definition of the cross sectional area of the airway.

Female↗
PubMed2004

Long line positioning in neonates: does computed radiography improve visibility?

OBJECTIVES: To assess the use of soft copy reporting of computed radiography (CR) images in determining intravenous long line tip position in neonates and compare visibility rates with hard copy printed images. METHOD: A retrospective study of all long lines inserted on the neonatal unit over a period of one year was performed. Forty five lines were inserted in 30 neonates over this time. Assessment of the CR images was made by three independent observers by reviewing the films on the viewing console and as hard copy printed films. RESULTS: Accurate identification of the line tip could be made in 66.7% of cases (kappa = 0.9) using hard copy images and 95.6% cases (kappa = 1.0) using soft copy reporting (significant difference: p = 0.002). The difference in percentage visibility using the two techniques was 28.9% (95% confidence interval 10.2% to 36.7%). CONCLUSION: The use of soft copy review of CR image improves the visibility of the line tip position compared with hard copy films and reduces the need for repeat radiographs with/without intravenous contrast.

Catheterization, Central Venous↗
PubMed2005

Computer simulation of forward wave propagation in soft tissue.

A method for simulating forward wavefront propagation in heterogeneous tissue is discussed. The intended application of this method is for the study of aberration produced when performing ultrasound imaging through a layer of soft tissue. A one-way wave equation that permits smooth variation in all acoustically important variables is derived. This equation also describes tissue exhibiting nonlinear elasticity and arbitrary frequency-dependent relaxation. A numerical solution to this equation is found by means of operator splitting and propagation along the spatial depth coordinate. The numerical solution is accurate when compared to analytical solutions for special cases, and when compared to numerical solutions of the full wave equation by other methods. The presented implementation provides a fast numerical method for studying the impact of aberration in medical ultrasound imaging through soft tissue--both on the transmitted beam and the nonlinearly generated harmonic beam.

Animals↗