Morphological characteristics of styloid process evaluated by computerized axial tomography

Morphological characteristics of styloid process and ossified stylohyoid ligament and their overall relationships to age and sex were studied by using computerized axial tomography images.

The styloid process and ossified stylohyoid ligaments were classified into seven groups according to their shapes and lengths.

The styloid process of a length of 25–40 mm, was the most frequently encountered. The elongated styloid process was mostly seen in males.

There was no overall correlation between the types of SP and sex. The progressive increase in length with age was not seen in our study.     

Vector entropy imaging theory with application to computerized tomography

Medical imaging theory for x-ray CT and PET is based on image reconstruction from projections. In this paper a novel vector entropy imaging theory under the framework of multiple criteria decision making is presented. We also study the most frequently used image reconstruction methods, namely, least square, maximum entropy, and filtered back-projection methods under the framework, of the single performance criterion optimization. Finally, we introduce some of the results obtained by various reconstruction algorithms using computer-generated noisy projection data from the Hoffman phantom and real CT scanner data. Comparison of the reconstructed images indicates that the vector entropy method gives the best in error (difference between the original phantom data and reconstruction), smoothness (suppression of noise), grey value resolution and is free of ghost images.     

A biologically-based algorithm for companding computerized tomography (CT) images

Computerized Tomography (CT) images are High Dynamic Range (HDR) images of the X-ray attenuation coefficients of the body's tissues. The inability to see abnormalities in tissues with marked differences in their X-ray attenuation coefficients, in a single CT window, poses a significant clinical problem in radiology. In order to provide proper contrast, which reveals all the required clinical details within each specifically imaged tissue, a single CT slice must be viewed by a radiologist four times: the first viewing focuses on the lung window; the second viewing focuses on the soft tissues window; the third viewing focuses on the liver window; and the fourth viewing focuses on the bone window. In order to enhance the ability to perform a complete diagnosis, while decreasing diagnostic time, we developed the BACCT (Biologically-based Algorithm for Companding CT images) method. Our algorithm compresses and expands (compands) the HDR CT image into a single, low dynamic range image. Before performing the companding procedure, unique processing is required which involves operations that enhance and stretch the image. The performance of our algorithm has been demonstrated on a large repertoire of CT body images. All the clinically required CT information is exposed in each CT slice in a single image. The algorithm compands the CT images in a fully automatic way. Collaborating radiologists have already tested the results of our algorithmic method, and reported that the images seem to provide all the necessary information. However, clinical tests for statistical reliability are still required.     

Computerized axial tomography in syringomyelia.

The ACTA-scanner, a device for computerized axial tomography, permits cross-sectional radiographic study of the entire human body, including the spine. In the ACTA-scan, the spinal cord appears as a roundish formation surrounded by the less dense subarachnoidal cerebrospinal fluid. The spines of 18 patients with verified (nine cases) or suspected (nine cases) syringomyelia were studied by ACTA-scanning. In seven of the verified and in four of the nonverified cases, some evidence of cord cavitation was shown. The cystic part of a cervical-cord ependymoma was also demonstrated. ACTA-scanning is an easily performed, noninvasive, innocuous procedure. This technic, which complements other radiographic methods of evaluating the spinal cord, is particularly suitable for screening and follow-up study of patients with syringomyelia. The easily accomplished recognition of a possible associated hydrocephalus is an added advantage of ACTA-scanning.     

Model-based ultrasound tomography: tissue phantom experiments

We present a detailed experimental study to evaluate our finite element based nonlinear reconstruction algorithm for recovery of acoustic properties in heterogeneous scattering media. Using a circularly scanning ultrasound system at 500 KHz, tissue phantom experiments were performed to study spatial resolution and contrast issues in model-based ultrasound tomography. Our results show that both acoustic attenuation and speed images can be quantitatively reconstructed in terms of the location, size, shape, and acoustic property value of the target when different contrast levels between the target and background were used. We also demonstrate that a high contrast target as small as 3 mm in diameter can be quantitatively resolved with our acoustic speed and attenuation images.     

Differential findings in post-factum dissections of medieval Korean mummies exhibiting similar preservation patterns on computerized tomography images

In our previous CT and post-factum dissection studies on medieval Korean mummies, well preserved internal organs generally were found to have been displaced to the dorsal side of the body cavity. This movement seems to have been caused by the effect of gravitational force exerted over long burial durations. However, when we recently examined a newly discovered medieval Korean mummy (SN1-2) by CT, most of the mummified organs were found to have remained in their natural positions. Our post-factum dissection of SN1-2 showed that the organs might have undergone expansion by posthumous gas formation, after which they hardened into a stone-like state, which mitigated against their displacement.Similar CT findings were made in the case of a second Korean mummy (KU-1). Since the internal organs within the thoracic cavity were discovered to be in their natural positions, we suspected that they, like those in the case of SN1-2, had also been changed into stony structures. However, the post-factum dissection showed that the internal organs of KU-1 had neither hardened nor been displaced to the back wall of the thoracic cavity, owing possibly to the presence of a pleural adhesion. Overall, our results indicated that CT alone might be inadequate for correct estimation of the preservation status of internal organs in Korean mummies. This calls for further accumulation of dissection data, against which CT diagnoses can be compared and by which they can be improved.     

A phantom and a procedure to obtain variable-object-contrast test images in gamma camera emission computed tomography (SPECT)

The value of test objects with a range of object contrast has been widely recognized for the testing of medical imaging equipment. A simple phantom is described, which, together with a data processing procedure, provides variable-contrast rod objects in gamma camera emission computed tomography (SPECT). There is only one compartment to fill with radioisotope, and data from hot rods, cold rods and a uniform section are available for analysis. The rod object contrast varies from 100% to 0%, with nine contrast steps used in this analysis. The measured image contrast in the transaxial slices is shown to be sensitive to variations in the system spatial resolution. With only one compartment to fill with radioisotope, this procedure is applicable for routine checking or optimization of gamma camera SPECT systems.     

Geometrical accuracy and fusion of multimodal vascular images: a phantom study

The aim of this work was to compare the geometrical accuracy of x-ray angiography, magnetic resonance imaging (MRI), x-ray computed tomography (XCT), and ultrasound imaging (B-mode and IVUS, or intravascular ultrasound) for measuring the lumen diameters of blood vessels. An image fusion method was also developed to improve these measurements. The images were acquired from a phantom that mimic vessels of known diameters. After acquisition, the multimodal images were coregistered by manual alignment of fiducial markers, and then by maximization of mutual information. The fusion method was performed by means of a fuzzy logic modeling approach followed by a combination process based on a possibilistic theory. The results showed (i) the better geometrical accuracy of XCT and IVUS compared to the other modalities, and (ii) the better accuracy and smaller variability of fused images compared to single modalities, with respect to most diameters investigated. For XCT, the error varied from 0.4% to 5.4%, depending on the vessel diameter that ranged from 0.93 to 6.24 mm. For IVUS, the error ranged from -0.3% to 1.7% but the smallest vessel (0.93 mm) could not be investigated because of the probe size. Compared to others fusion schemes, the XCT-MRI fused images provided the best results for both accuracy (from -1.6% to 0.2% for the three largest vessels) and robustness (mean relative error of 1.9%). To conclude, this work underlined both the usefulness of the multimodality vascular phantom as a validation tool and the utility of image fusion in the vascular context.     

Imaging modalities in x-ray computerized tomography and in selected volume tomography

This review of different principles used in x-ray computerized tomography (CT) starts with attenuation (transmission) CT. The pros and cons of different geometrical solutions, single-ray, fan-beam and cone-beam, are discussed. Attenuation CT measures the spatial distribution of the linear attenuation coefficient, mu. The contributions of different interaction processes to mu have also been used for CT. Fluorescence CT is based on measurements of the contribution, cZtauZ/rho, from an element Z with concentration cZ, to the linear attenuation coefficient. Diffraction CT measures the differential coherent cross section d sigma (theta)(coh)/d omega, Compton CT the incoherent scatter cross section sigma. The usefulness of these modalities is illustrated. CT methods based on secondary photons have a competitor in selected volume tomography. These two tomography methods are compared. A proposal to perform Compton profile tomography is also discussed, as is the promising method of phase-contrast x-ray CT.     

Compton scatter axial tomography with x-rays: SCAT-CAT

A method of extracting information from the backscattered field produced in parallel beam x-ray computed tomography (CT) is presented. A calculational model to predict the backscattered field based on Compton scattering is described, and the model is verified by measurements of simple phantoms. The phantoms tested--cylinders of polymethylmethacrylate (PMM) with air gaps and aluminium rods placed internally--are irradiated on a scanning assembly, built to simulate a first generation CT scanner with a transmission and a scatter detector (the SCAT-CAT). Data from the transmission detector are reconstructed by traditional CT methods to provide a transmission image; it is the data from the backscatter detector which are analysed in this study. After verification of the model for the scattered field calculations, a method of extracting information from the scattered field is developed, based on ratios of scatter signals from non-uniform to uniform phantoms. This method is demonstrated for predicted data of a simulated phantom and for measured data of the same and two additional phantoms. The method is very sensitive to air gaps in the phantoms because of the relative electron density of air with respect to PMM; it is not as sensitive to aluminium rods for the same reason. Various methods of applying the scattered field information to produce an image representing a simulated phantom are considered, and a preferred method is chosen to reconstruct scattered field data into an image for the three phantoms studied.     

Sciatic nerve compression: diagnostic value of electromyography and computerized tomography

A 54 year old man on long term anticoagulation (warfarin) treatment for prosthetic heart valve, developed sciatic nerve compression and femoral nerve dysfunction due to hematoma and edema in the gluteal muscles. Computerized tomography of the pelvis and electrodiagnostic studies helped in localizing and understanding the pathophysiology of the clinical signs and symptoms.