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Biomedical subjects

C Ytterbergh

Publications and source records attributed to C Ytterbergh.

15 recordsLinked to original sources
PubMed1989

Radiation dose in assessment of tibial torsion with a mobile C-arm fluoroscope.

The absorbed dose to the skin was measured in adult patients undergoing fluoroscopy with a mobile C-arm fluoroscope for determination of tibial torsion. Two methods suitable for routine measurement of tibial torsion were investigated in this respect. The mean absorbed doses for assessment of torsion in one extremity were found to be 5.3 and 5.5 mGy respectively. No scattered radiation to the contralateral foot or symphysis of patient was recorded. The examiner received no measureable dose on any occasion.

Fluoroscopy↗
PubMed1987

From sagittal distance to area. A study of transverse, vocal tract cross-sectional area.

In speech articulation studies, data on the pharynx are scarce. Still, the pharynx is an important part of the vocal tract. The present paper reports on an attempt to use computed tomography for investigating the pharynx. Axial computed tomograms were taken at four levels in the pharynx of a male and a female subject sustaining the vowels [u:, i:, a:, oe:]. From the tomograms the lateral width and the cross-sectional area were measured and their relations to the sagittal distance from the back pharynx wall to the midline of the tongue examined and compared with previously published data. In addition, some previous results derived from plaster casts are presented showing the corresponding distance-to-area relationship in the mouth region of some male and female subjects.

Female↗
PubMed1984

Radiographic pelvimetry--its use and possible radiation risk.

Radiographic pelvimetry is widely used in obstetrics. Every fourth primapara in Sweden is submitted to this radiographic examination. The frequency of the examination in the United States is estimated to a mean of 6% of all deliveries. The use of radiographic pelvimetry is now under intense debate and the missing argument in this discussion is a prospective study of an unselected group of parturients where progress and outcome of labour is referred to known pelvic dimension. Since the value of the method is questioned the frequent use of radiographic pelvimetry is justified only by an almost negligible radiation risk to the mother and her baby. Such a low risk is also an indispensable condition to allow the correct scientific evaluation of radiographic pelvimetry mentioned above. This paper presents the measurement results of absorbed radiation dose with the only radiographic pelvimetry method used in Sweden. The estimated radiation risk of the method, based on these figures, is 1 case of childhood malignancy in 50 000 pelvimetries. This corresponds to 4 years routine use of radiographic pelvimetry in Sweden. The annual incidence of childhood malignancy in Sweden is 220. The maternal risk is estimated to one tenth of the fetal risk.

Female↗
PubMed1983

Ellipsoidal body phantom for evaluation of CT scanners.

A phantom for study of uniformity, artifacts from dense structures, and consistency in pixel values was constructed. On-site studies of eight computed tomographs belonging to the second, third, and fourth generations showed that the phantom was appropriate for such measurements. The results indicate certain inherent shortcomings in some of the present designs.

Humans↗
PubMed1981

Perceptibility of experimental and clinical lesions in the CT image with and without image processing.

The Ohio-Nuclear Delta 50 FS whole-body CT scanner and image filtering programs FI and SP:SMOOTH provided with the equipment were used to investigate how the perceptibility in the CT image of artificial lesions in a phantom and of liver lesions in patients was influenced by different reconstruction diameters, radiation doses and section thicknesses and by image filtering and different conditions of viewing. The perceptibility of both artificial and clinical lesions was considerably improved, especially in scans with a low radiation dose, when optimum viewing conditions and image filters were used.

Filtration↗
PubMed1980

Noise and noise texture in CT images before and after post-processing.

Two homogeneous water phantoms were recorded under various CT scanner settings, and the reducing effect of various convolution filters on the noise level was evaluated. The change in noise texture introduced by the filtering process was assessed for a limited range of scanner settings by noise analysis of the autocovariance matrix before and after filtering. The results indicate that reduction of noise expressed as RMSD by a factor of about 8 is possible with the filters available in the software package of the Ohio-Nuclear Delta 50 FS tomograph, with some sacrifice in spatial resolution. Results of preliminary experiments with an inhomogeneous phantom are in agreement with this finding and indicate that filtering allows smaller lesions to be detected.

Computers↗
PubMedDate not supplied

Artifacts in computed tomography of the posterior fossa: a comparative phantom study.

A phantom consisting of a human skull fixed in a cylinder containing water was used to study the occurrence of artifacts and their influence on image quality in CT of the posterior fossa. Only minor differences in interpetrous bone artifact and in deviation in CT numbers in other parts of the posterior fossa were found between eight tested scanner models. Interpetrous bone artifact was not significantly affected by slice thickness but it could be reduced to some extent by proper selection of the scan angle and almost eliminated by application of a dual-energy technique. Other bone-related artifacts, however, were found to be dependent on slice thickness.

Evaluation Studies as Topic↗
PubMedDate not supplied

Deep-frozen biologic phantom for performance evaluation of CT scanners.

A test method with use of a biologic phantom--a deep-frozen specimen of a human cadaver--was developed in an attempt to simulate the clinical setting in CT of the spine. The quality of both soft tissue and bone images in the absence of motion artifacts was evaluated for seven scanner models. Special attention was paid to identification of the pattern and extent of artifacts. The phantom consisted of a spine with surrounding muscles. The images were evaluated subjectively and comparisons were made between the different scanners. Examples of these results are presented. A biologic phantom is a valuable supplement to artificial phantoms and increases the ability to evaluate and compare the performance of CT scanners.

Cadaver↗
PubMedDate not supplied

Reliability of attenuation measurements in CT of the lumbar spine: evaluation with an anthropomorphic phantom.

A phantom was constructed with the intention of simulating the clinical situation at examination of the spine. Artifacts from bony vertebral structures were analyzed and the uniformity in a body-shaped object was studied. Tests were carried out on eight CT scanners. A considerable variation in uniformity was found between the tested scanner models. The CT numbers within the spinal canal and in a region anterior to the spine were elevated for most of the scanners. The deviation varied considerably, however, between models.

Humans↗
PubMedDate not supplied

Eye lens dose in cranial computed tomography with reference to the technical development of CT scanners.

The continuous technical development of cranial CT and the accumulation of clinical experience with this method, have resulted in the use of an increasing number of scan protocols for different clinical situations. An investigation was undertaken to find out how this change has influenced the dose delivered to the patient. The eye lens dose was measured at CT examinations in 245 patients, with appropriate scan protocols, and also at corresponding examinations in an anthropomorphic head phantom. One CT scanner of early (EMI CT 1010) and one of modern design (Siemens Somatom DR2) were investigated. The range of the eye lens dose was wide, namely 4 to 206 mGy for EMI CT 1010 and 6 to 124 mGy for Somatom DR2. In patient groups with comparable scan protocols the mean eye lens dose was higher with the Somatom DR2, mostly on account of a different spatial distribution of the dose in the scan plane. The dose varied less with this scanner, however, mainly because of the possibilities for more accurate positioning.

Humans↗
PubMedDate not supplied

Computed tomography of temporal bone specimens. A test of the resolution capability.

Ten deep-frozen temporal bone specimens were subjected to computed tomography (CT) in five different projections. The possibility of identifying small structures, such as the ossicles and aqueductal lumina, was assessed. In addition, the semicircular canals were measured. Subsequently corresponding measurements were carried out on plastic casts of these specimens for comparison. A temporal bone specimen is well suited as a test object for evaluating the detectability of small and dense natural structures by CT.

Ear Ossicles↗
PubMedDate not supplied

Spatial distribution of dose in computed tomography with special reference to thin-slice techniques.

The spatial dose distribution in a cylindrical polystyrene phantom with a diameter of 200 mm was measured for seven computed tomography (CT) scanners. The measurements were performed in the head mode and mainly for narrow slices in the range 1.5 to 4 mm. Both radial and axial dose profiles were measured and the dose distribution for multiple-scan procedures was calculated. The ratio between the surface and centre doses for a single scan varied between the extremes of 1.8 and 4.3 and was generally higher for narrow than for wide slices. With multiple nominally contiguous scans the difference in absorbed dose between surface and centre locations in the object decreased, on account of scattered radiation. The CT dose index for centre locations varied considerably between the tested scanners, with a range from 5.6 to 27.2 mGy per nominal 100 mAs. For a simulated multiple-scan procedure, comparable to a CT examination of the orbits, the multiple-scan average dose varied between 4.3 and 16.4 mGy per nominal 100 mAs.

Body Burden↗
PubMedDate not supplied

Dual energy computed tomography: simulated monoenergetic and material-selective imaging.

A dual beam-quality technique was used to reduce the beam hardening artifact in CT and to obtain separate images of osseous and soft-tissue structures in phantom and clinical CT studies. Recordings were made with pulsed low and high kVp spectra with the Somatom DR2. Conventional polyenergetic and simulated monoenergetic images were reconstructed from the measurements. In the monoenergetic images the beam hardening artifacts were 60-90% lower than in the high kVp polyenergetic images whereas the noise was of the same order of magnitude in the two types. Noise in the monoenergetic images was lowest around 70-80 keV both in body and skull examinations although the contrast in the monoenergetic image was rather independent of energy.

Giant Cell Tumors↗
PubMedDate not supplied

Multiplanar spinal anatomy: comparison of CT and cryomicrotomy in postmortem specimens.

Good anatomic knowledge is a prerequisite for correct interpretation of computed tomographic (CT) scans. To elucidate the complex CT anatomy of the spine, autopsy specimens from various spinal regions were frozen in situ to preserve the undistorted topographic anatomy. The frozen specimens were examined by CT in axial, sagittal, and coronal planes and sectioned by cryomicrotomy along the scanning planes. Photography of the section surfaces yielded detailed anatomic images that were accurately correlated with the CT scans.

Adult↗