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At least 415 records · Page 23Linked to original sources
PubMed1990

Computed tomography of metastatic cervical lymph nodes. A clinical, computed tomographic, pathologic correlative study.

A retrospective comparative study of 63 neck dissections was undertaken to evaluate further the accuracy of high-resolution computed tomography (CT) in the detection of nodal metastases, as previous studies have indicated a trend toward the superiority of CT scanning over palpation. The respective values of neck examination, CT scanning, and histopathologic examination were assessed in 51 patients with head and neck cancer who underwent a total of 63 neck dissections. The overall agreement between clinical examination findings and histopathologic findings was 92% vs 81% for CT scanning. A retrospective analysis of the CT findings failed to reveal greater accuracy. We found nodes measuring 10 mm or more with central low density always to be malignant. Because CT scanning seems to offer little advantage over palpation in the nonirradiated neck, it should not be regarded as an essential tool in the staging of nodal disease. After radiation therapy, as neck dissection is only performed because of clinical or radiologic suspicion, CT scanning is of utmost importance.

False Negative Reactions↗
PubMed1986

Computer-assisted morphometry using video-mixed microscopic images and computer graphics.

A microcomputer system has been developed for collection and analysis of morphometric data from video images of histological sections. Microscopic fields of view are visualized on a video monitor and are overlaid with computer-generated graphics by means of a video mixer. Planimetric data are entered by drawing on a digitizing tablet while observing the drawn image superimposed on the tissue. Programs are available to calculate various geometric parameters, count objects in a field, perform descriptive statistics, and measure volume and surface area of a solid from a series of cross sections. A program for point-counting stereology presents single points for scoring within a user-defined reference area. The potential applications of interactive graphics in morphometry are discussed.

Cell Nucleus↗
PubMed2004

Prospective study of contrast-enhanced computed tomography, computed tomography during arterioportography, and magnetic resonance imaging for staging colorectal liver metastases for liver resection.

BACKGROUND: This study compared the value of contrast-enhanced helical computed tomography (CT), CT during arterioportography (CTAP), and contrast-enhanced magnetic resonance imaging (MRI) for staging patients with colorectal liver metastases. METHODS: One hundred and twenty patients with known or suspected colorectal liver metastases were evaluated prospectively. MRI and CTAP were performed within 3 weeks of CT in patients with potentially resectable tumours. Results of imaging were compared with findings at surgery, intraoperative ultrasonography and histological examination. RESULTS: Twenty patients were not considered for liver resection following CT. The remaining 100 patients underwent CT and CTAP, 85 of whom had CT, CTAP and MRI. The sensitivity and specificity were 73.0 and 96.5 per cent for CT, 87.1 and 89.3 per cent for CTAP, and 81.9 and 93.2 per cent for MRI. Positive predictive values were 89.7, 87.5 and 87.5 per cent respectively. Receiver-operator characteristic analysis gave an accuracy on a segment-by-segment analysis of 0.73 for CT, 0.87 for CTAP and 0.82 for MRI. Combining information from CT and CTAP, CT and MRI, or all three modalities, did not significantly increase the percentage of patients staged correctly (71, 72 and 76 per cent respectively). CONCLUSION: The diagnostic accuracy of spiral CT, MRI and CTAP was similar. Combining modalities did not improve accuracy.

Adult↗
PubMedDate not supplied

[Deliberations and computer computations on the epidemiology of the acquired immunodeficiency syndrome in the Federal Republic of Germany].

A computer simulation of the morbidity and mortality rates of the "Acquired Immunodeficiency Syndrome" in the Federal Republic of Germany was performed. Since sexual intercourse is the main mode of transmission, the population was divided into six groups with different sexual behaviour. In several variations of the program it is demonstrated that during the next 15 years up to 41,000 AIDS patients can be expected. The importance of female prostitutes and male bisexuals as "vectors" who may transmit the infection into exclusively heterosexual groups is shown. Using this program, the effect of prophylaxis against infection as well as of changes of sexual behaviour within the population at large can also be examined.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Graz brain-computer interface II: towards communication between humans and computers based on online classification of three different EEG patterns.

The paper describes work on the brain--computer interface (BCI). The BCI is designed to help patients with severe motor impairment (e.g. amyotropic lateral sclerosis) to communicate with their environment through wilful modification of their EEG. To establish such a communication channel, two major prerequisites have to be fulfilled: features that reliably describe several distinctive brain states have to be available, and these features must be classified on-line, i.e. on a single-trial basis. The prototype Graz BCI II, which is based on the distinction of three different types of EEG pattern, is described, and results of online and offline classification performance of four subjects are reported. The online results suggest that, in the best case, a classification accuracy of about 60% is reached after only three training sessions. The online results show how selection of specific frequency bands influences the classification performance in single-trial data.

Communication↗
PubMed2003

Usefulness of known computed tomography and clinical criteria for diagnosing strangulation in small-bowel obstruction: analysis of true and false interpretation groups in computed tomography.

Computed tomography (CT) criteria have proven useful, but not sufficient, for diagnosis of bowel strangulation. The purpose of the present study was to evaluate the use of clinical criteria in the interpretation of CT scans as a means of improving the diagnostic accuracy of CT, especially in patients whose CT scans are equivocal for distinguishing simple obstruction from strangulated obstruction. We analyzed the CT scans of 136 patients with simple (n=70) or strangulated (n=66) small-bowel obstruction. Three radiologists interpreted the CT scans independently for the presence of intestinal strangulation. According to their interpretation, 136 patients were divided into two groups, i.e., a false and a true interpretation group. The diagnostic value of known CT and four clinical criteria (tenderness, tachycardia, fever, and leukocytosis) were compared in the two groups. The diagnostic accuracy of CT criteria for distinguishing simple obstructions from strangulated small-bowel obstructions ranged between 73% and 80%. Of the 136 patients, 31 belonged to the false group and 105 to the true group. The CT criteria that were highly specific in both groups included severe mesenteric haziness, serrated beak, and poor bowel wall enhancement. Among the clinical criteria, both tachycardia and leukocytosis were highly specific in both groups. The number of positive clinical criteria was helpful in making a diagnosis; none or one clinical criterion indicated a simple obstruction, whereas three or four criteria indicated a strangulated obstruction; when this result was applied retrospectively to the false group, the CT diagnostic accuracy improved in 19 of the 31 patients. The use of clinical criteria when CT findings are equivocal, may overcome the inherent limitations of CT for diagnosing strangulated small-bowel obstruction.

False Negative Reactions↗
PubMed2005

Evaluation of computed tomography coronary angiography in patients with a high heart rate using 16-slice spiral computed tomography with 0.37-s gantry rotation time.

The aim of our study is to evaluate computed tomography (CT) coronary angiography in patients with a high heart rate using 16-slice spiral CT with 0.37-s gantry rotation time. We compare the image quality of patients whose heart rates were over 70 beats per minute (bpm) with that of patients whose heart rates were 70 bpm or less. Sixty patients with various heart rates underwent retrospectively ECG-gated multislice spiral CT (MSCT) coronary angiography. Two experienced observers who were blind to the heart rates of the patients evaluated all the MSCT coronary angiographic images and calculated the assessable segments. A total of 620 out of 891 (69.6%) segments were satisfactorily visualized. On average, 10.3 coronary artery segments per patient could be evaluated. In 36 patients whose heart rates were below 70 bpm [mean 62.2 bpm+/-5.32 (standard deviation, SD)], the number of assessable segments was 10.72+/-2.02 (SD). In the other 24 patients whose heart rates were above 70 bpm [mean 78.6 bpm+/-8.24 (SD)], the corresponding number was 9.75+/-1.74 (SD). No statistically significant difference was found in these two subgroups' t test, P>0.05. The new generation of 16-slice spiral CT with 0.37-s rotation time can satisfactorily evaluate the coronary arteries of patients with high heart rates (above 70 bpm, up to 102 bpm).

Adult↗
PubMed1989

Analysis of Ter-Ter enzyme kinetic mechanisms by computer simulation of isotope exchange at chemical equilibrium: development and application of ISOTER, a personal-computer-based program.

A convenient, personal-computer-based program has been developed that allows simulation of isotopic exchange kinetics at chemical equilibrium catalyzed by a three reactant-three product (TerTer) enzyme system: A + B + C integral of P + Q + R. This program, ISOTER, utilizes a rapid algebraic method to calculate the exchange rate between any reactant-product pair as a function of the substrate concentration and avoids altogether the necessity of deriving an explicit (but cumbersome and impractical) equation for exchange rate. ISOTER was used to generate model saturation patterns for 16 different TerTer kinetic mechanisms, varying different combinations of reactant-product pairs in constant ratio at equilibrium: [all substrates], [A, P], [B, Q], and [C, R], while holding the nonvaried components constant. These model studies indicate that virtually every one of these mechanisms can be distinguished from the others. In addition, ISOTER has been used to fit multiple sets of experimental data for Escherichia coli glutamine synthetase, which produced a set of rate constants consistent with the previously proposed "preferred order random" kinetic mechanism.

Computer Simulation↗
PubMed1994

Intraoral computed radiography using the Fuji computed radiography imaging plate. Correlation between image quality and reading condition.

The quality of images obtained by a new method of intraoral computed radiography using three types of imaging plates and a drum scanner designed exclusively for use with an imaging plate was investigated. The aperture size for reading of radiographic data from the imaging plate and for film recording was 50, 100, or 150 microns 2. The results indicated that high resolution type imaging plate for mammography produced the best image quality. For each imaging plate, it was also found that the image quality improved as the aperture size was decreased. However, the high resolution type IP even at the aperture size of 100 microns 2 showed diagnostic accuracy as high as the image processing of conventional periapical radiographs. This finding suggests that this new imaging system using an imaging plate at the reading and recording aperture size 100 microns 2 has promise for use in intraoral radiography.

Evaluation Studies as Topic↗
PubMedDate not supplied

Comparative assessment of doses to tumor, rectum, and bladder as evaluated by orthogonal radiographs vs. computer enhanced computed tomography-based intracavitary brachytherapy in cervical cancer.

PURPOSE: To carry out a comparative assessment of intracavitary brachytherapy (ICBT) doses to tumor, bladder, and rectum based on orthogonal films and contrast enhanced computed tomography (CECT). METHODS AND MATERIALS: Fifty-five ICBT procedures with CT/MRI compatible applicator and CECT scans were evaluated. Doses to Point A, International Commission on Radiation Units and Measurement (ICRU) reference points for maximum bladder (B max(ICRU)) and rectum (R max(ICRU)) localized from orthogonal films were compared with CECT delineated tumor, bladder (B max(CECT)), and rectum (R max(CECT)) doses, respectively. The 95th and 90th percentile bladder (B 95(CECT) and B 90(CECT)) and rectal (R 95(CECT) and R 90(CECT)) doses based on CECT were also estimated. RESULTS: Mean percentage tumor volume encompassed within the prescribed dose of 600 cGy to Point A was 88.8%. Mean B max(ICRU), B max(CECT), R max(ICRU), and R max(CECT) were 631.3 cGy, 1221.4 cGy, 454.8 cGy, and 526.9 cGy, respectively. Paired mean differences were significant between B max(ICRU) and B max(CECT) or B 95(CECT) (both p < 0.001); R max(ICRU) and R max(CECT) (p = 0.005) or R 90(CECT) (p < 0.001), whereas insignificant for B max(ICRU) and B 90(CECT) (p = 0.281), and R max(ICRU) and R 95(CECT) (p = 0.372). CONCLUSIONS: Prescription based on Point A ICBT doses could lead to uncertainty and underdosage in tumor. ICRU 38 maximum bladder and rectal doses significantly underestimate the maximum doses to these organs and represent the 90th and 95th percentile of the maximum doses to these organs, respectively.

Brachytherapy↗
PubMed2004

Facial computed tomography use in trauma patients who require a head computed tomogram.

PURPOSE: Head-injured patients admitted to a trauma center may or may not have associated facial fractures. Most head-injured patients undergo head computed tomography (CT) scan early in their evaluation. The question of adding a facial CT at the time of the head CT can be unclear. The aims of our study are 1) to analyze how the facial CT is used in conjunction with the head CT in facial fracture trauma patients, 2) to recognize unique identifiers that would aid the surgeon's decision-making process to order a facial CT in continuity with a head CT, and 3) to examine what is characteristic of head trauma patients who receive a facial CT separately, at some point after the head CT. Materials and methods Data were retrospectively reviewed for a 5-year period at a level I trauma center in which all patients who present with craniomaxillofacial trauma are managed by the oral and maxillofacial surgery (OMFS) service. Included patients must have obtained a head CT during initial resuscitation and be diagnosed with a facial fracture during the same hospital stay. These patients were divided into 3 groups: those who had a 1) head CT only, 2) head CT and facial CT at the same time, and 3) head CT with the facial CT performed at a later time. RESULTS: A total of 9,871 patients were admitted to the trauma service during a 5-year period and 4,926 patients (49.9%) had head CT performed. Of this group, 12% had facial fractures, and the most common associated injury in this group was facial lacerations and concussions. The nasal fracture followed by the orbital fracture was the most common fracture type. Eighty-four percent of the time, the facial CT was used to help diagnose facial fractures in this patient population. The 3 different groups showed unique trends. CONCLUSION: Six points were identified in our study that can augment the physical examination in patients who require head CT. The following points can help prompt the clinician to order a combination head and facial CT: 1) 12% of trauma patients who require a head CT will have a facial fracture, whereas half of these patients will have multiple facial fractures. 2) Orbital fractures are commonly missed in this group and often require a secondary scan such as coronal views for accurate diagnosis. 3) Facial lacerations correlate with ordering a combination head and facial CT. 4) The most common facial fracture identified among patients receiving a trauma head CT is the nasal fracture. 5) The use of the facial CT in more severely injured patients tended to be delayed and was related to increased hospital and intensive care unit days. 6) Only 16% of facial fracture patients who had received an initial trauma head CT did not require further facial CT scanning.

Adult↗
PubMed2005

A novel high-resolution magnetic resonance imaging microscopy coil as an alternative to the multislice computed tomography in postoperative imaging of orbital fractures and computer-based volume measurement.

BACKGROUND: Multislice computed tomography (MSCT) has been the modality of choice for postoperative detailed imaging of orbital trauma. Unfortunately, it involves extensive exposition of the lens to radiation, especially when taking multiple readings. Also, it holds beam hardening effects and limited imaging (delineation) of the reconstruction material. Alternative conventional magnetic resonance imaging (MRI) head coils (MRIhc) present reduced differentiation of anatomic structures caused by low signal and artifact appearance. A substantially improved depiction is made possible by a newly introduced MRI microscopy coil (MRImc), used for the first time in this field. PATIENTS AND METHODS: In this prospective study, 32 patients with extended orbital wall fractures (n = 36) were treated surgically using a polydioxanonsulfate (PDS) foil after reconstruction. Postoperatively, imaging was performed using MRImc, conventional MRI, and MSCT to evaluate the different imaging techniques. RESULTS: The position of the PDS foil could precisely be depicted in 29 of 36 fractures by MRImc, whereas by conventional MRI and MSCT the reconstruction material could only be detected in 25 and 24 of 36 fractures, respectively. In contrast to MRIhc, the new microscopy coil allows fast and high resolution imaging and therefore a clear differentiation of eventual postoperative complications (eg, dislocation of the PDS foil with secondary soft tissue entrapment resulting in limitation of ocular movements or enophthalmos). In 13 long lasting symptomatic cases, revision surgery could be avoided because of regular MRImc findings, apart from muscle swelling and hematoma. In 11 cases of inadequate PDS foil position resulting in revision, the mean volume of displaced tissue (VDT) of 0.62 cm3 correlated significantly to an enophthalmos of more than 2 mm. CONCLUSION: In this pilot study, MRImc proved to be highly superior to MRIhc and MSCT in postsurgical orbital imaging, especially for decision making regarding revision surgery.

Adolescent↗
PubMed2004

Helical computed tomography accurately reports urinary stone composition using attenuation values: in vitro verification using high-resolution micro-computed tomography calibrated to fourier transform infrared microspectroscopy.

OBJECTIVES: To assess the ability of helical computed tomography (CT) to differentiate regions of known mineral composition in typical, heterogeneous urinary stones. Interest is substantial in the urologic community in using radiologic imaging to determine accurately the composition of urinary calculi. Recent advances in CT make this a viable prospect, but the heterogeneity of most stones is a complicating factor. METHODS: The ability of micro-CT (a high-resolution laboratory instrument) to identify the mineral composition of stones was confirmed by calibrating micro-CT attenuation values to pure mineral regions of sliced stones using infrared microspectroscopy. Intact human urinary stones were then analyzed by micro-CT, and regions-of-interest of pure mineral were correlated with identical regions-of-interest from quad slice multi-detector row helical CT images. With helical CT, narrow slice widths were used to decrease volume-averaging errors, and bone windows were used so that internal stone structure was visible. RESULTS: When stones were imaged using helical CT at narrow slice widths, mineral-specific regions-of-interest yielded nonoverlapping attenuation values for uric acid (566 to 632 Hounsfield units [HU]), struvite (862 to 944 HU), calcium oxalate (1416 to 1938 HU), and hydroxyapatite (2150 to 2461 HU). CONCLUSIONS: High resolution helical CT yields unique attenuation values for common types of stone mineral, but proper windowing is required to localize regions of homogeneity. The results of this in vitro study suggest that high-resolution helical CT may be able to identify stone composition at patient diagnosis.

Calcium Oxalate↗
PubMed2003

DISCO--a general computer program for the computation of acid dissociation constants of polyprotic molecules in water and biological fluids, from nuclear magnetic resonance data: application to polyamines.

A new computer program, DISCO, running under Windows, has been developed under the project CSA98P22 falling within the Competitive Support Activities initiative launched within the EU 4th Framework Programme. DISCO allows the calculation of the stepwise acid dissociation constants of polyprotic molecules in water and in complex media (i.e., biofluids, etc.) from nuclear magnetic resonance (NMR) data (chemical shifts) by means of two derivative-free methods: Pit-mapping and Simplex. DISCO performances were tested using simulated-unaffected by experimental error-data sets, for systems having up to seven equilibrium constants and experimental NMR data of spermine, 6-monofluorospermine, and 6,6-difluorospermine, dissolved in D(2)O and in physiological solution (D(2)O/NaCl). Results demonstrated that (i) DISCO enables the determination of pK(A) values with high precision even when small-sized raw data sets are employed, when chemical shifts are measured with low precision (the usual condition in biofluids due to the impossibility to obtain narrow line shape), and when the guess solution, necessary as an initial step of the mathematical iterative process, is fixed within a large interval of variation; (ii) DISCO always converges to the root; (iii) DISCO permits the calculation of pK(A) values which lie within the observed pH range, independent of the narrowness of the pH range.

Algorithms↗
PubMed1996

Manual versus computer-automated semen analyses. Part II. Determination of the working range of a computer-automated semen analyzer.

OBJECTIVE: To determine the accuracy and precision of a computer-automated semen analyzer (CASA; Hamilton-Thorne Research, Beverly, MA) over a wide range of sperm concentrations. DESIGN: Prospective study using comparative measurements of sperm concentration and motility were performed using manual and CASA methods of analyses. SETTING: A hospital-based Andrology laboratory. PATIENTS: Male partners of couples undergoing infertility evaluation. MAIN OUTCOME MEASURES: Measurements of sperm concentration in the range of 1 to 200 x 10(6)/mL were performed using hemacytometers and CASA-analyzed 20 MicroCell counting chambers (Conception Technologies, Inc., La Jolla, CA). Accuracy was assessed by comparison to the hemacytometer ("gold standard"). The MicroCell counting chambers also were used for manual and CASA sperm motility determinations. RESULTS: The CASA-analyzed 20 Microcell Chamber most precisely determined sperm concentration in the 1 to 200 x 10(6)/mL range (intraclass correlation coefficient = 0.94). The hemacytometer was least precise (intraclass correlation coefficient = 0.91). There was a high degree of correlation between the manually and CASA-analyzed MicroCell Chambers in the sperm concentration range of 20 to 149 x 10(6)/mL. Above and below this range, correlation was lower. Motility was determined most precisely using the CASA-analyzed 20 MicroCell Chamber. CONCLUSIONS: The Hamilton-Thorne CASA used with the 20 MicroCell Chamber is a precise and accurate method for determining sperm concentration and motility of semen specimens with concentrations in the 20 to 149 x 10(6)/mL range. This same combination of CASA and MicroCell Chamber provides precise sperm motility results.

Computers↗
PubMed1998

Multiplanar imaging in the preoperative assessment of metallic intraocular foreign bodies. Helical computed tomography versus conventional computed tomography.

OBJECTIVE: This study aimed to compare the effectiveness of helical computed tomography (CT) versus conventional CT in the preoperative assessment of metallic intraocular foreign bodies on axial, coronal, and multiplanar reconstruction images in clinical routine. DESIGN: Prospective comparative trial, alternate assignment of consecutive patients. PARTICIPANTS: Eighteen patients with penetrating eye injuries and suspected metallic intraocular foreign bodies were studied. INTERVENTION: Alternate patients were assigned to undergo either helical CT or conventional CT in the axial plane. Both the helical and the conventional data were transferred to a workstation, and reconstructions in the coronal and sagittal planes were performed. Additional direct coronal scanning was performed only when necessary for preoperative assessment. MAIN OUTCOME MEASURES: The quality of the directly obtained axial and coronal, as well as the reconstructed coronal and sagittal images, was assessed for each, imaging method based on the ability to detect and accurately localize foreign bodies. The size of the foreign bodies was measured and compared to the actual diameter. Total examination time and radiation dose delivered to the lens were measured for each imaging method. RESULTS: All foreign bodies were detected by each scanning method on the axial, the coronal, and on the reconstructed planes. The quality of the axial images was similar for helical and conventional CT. The helical technique provided high-quality reconstructed images comparable in quality to the directly obtained coronal planes in conventional CT. Reconstructions by conventional technique were not useful for preoperative assessment. The examination time for the total orbital volume was 18 seconds for helical CT examinations and 52 seconds for conventional CT examinations. Radiation dose delivered to the lens for the complete examination was 35 mGy for helical CT axial scanning, 56 mGy for conventional CT axial scanning, and 63 mGy for conventional CT coronal scanning. CONCLUSIONS: Helical CT multiplanar imaging offers several significant advantages for the preoperative assessment of metallic intraocular foreign bodies compared to the conventional CT technique in clinical practice, including short examination time, reduced motion artifacts, reduced radiation exposure, and the ability to obtain diagnostically useful coronal and sagittal reconstruction images without the need for additional scanning.

Adolescent↗
PubMed2003

Imaging of myocardial microvasculature using fast computed tomography and three-dimensional microscopic computed tomography.

In the past, much attention in imaging research was focused on the macroscopic morphology and patency of arteries. Only recently, research and clinical interest have shifted to the microcirculation and its impact on the long-term prognosis in patients with vascular diseases. This focus and newly developed therapeutic strategies require high-resolution imaging modalities, which do not focus exclusively on the macroscopic aspects of the arterial tree. Provided here is a comprehensive perspective of using computed tomography technology to image and quantify the function and morphology of myocardial and vascular adventitial microvessels in normal and disease states.

Blood Volume↗