Biomedical subjects

W Kalender

Publications and source records attributed to W Kalender.

28 records · Page 2Linked to original sources

PubMed1987

[Material-selective imaging and density measurement using the dual-energy method. I. Principles and methodology].

The principles of the Dual Energy method are discussed from two perspectives: a clear illustration of the method and an exact presentation of the principles involved. The principles apply to both radiography and computed tomography. The method was implemented on a CT scanner (SOMATOM DR, Siemens AG). Dual Energy images enable highly selective imaging based on the determination of density values for calcified and soft tissue. Images may also be reconstructed that are based on other parameters such as electron density and effective atomic number. The degree to which selective imaging is possible is discussed. Examples of Dual Energy clinical applications for radiography and computed tomography are presented. More detailed information will be available in future contributions.

Humans↗

PubMed1984

[Computerized tomographic demonstration of the nerves and blood vessels of the cerebellopontile angle. Results of pneumocisternomeatography in comparison with intraoperative findings].

Disorders of the 8th cranial nerve such as sensori-neural hearing loss, tinnitus or vertigo may be of vascular origin. Pulsation of arteries can cause compression of, or traction on the nerve, and surgical "decompression" using a modified transtemporal approach may be helpful for these cases. The investigations are based on modern computerized tomography techniques combined with air-cisterno-meatography. The nerves can be demonstrated routinely, while the imaging of vessels is not always possible. This different appearance of arteries may be caused by their pulsatile motion, as shown by phantom studies. The effect of this motion is discussed on the basis of a comparison between preoperative CT-findings and the topography of the vessels verified at operation.

Angiography↗

PubMed1983

[Relevance of computed tomography to the fine-structure analysis of bone. A comparative radiological study].

Computed tomography, a relatively young X-ray imaging modality, has so far been mainly employed for the differentiation and densitometry of soft tissues. By modification of the image reconstruction algorithm spatial resolution was improved significantly such that imaging of fine structures and of high contrast boundaries became possible. The image characteristics of the high-resolution computed tomograms were investigated on petrous bones and lumbar vertebral bodies. In the petrous bone, an exact anatomic reconstruction of the bony structures of the inner ear is achieved. In vertebral bodies, imaging of spongiosa structures with 2 mm slice thickness and thereby an early diagnosis of osteoporosis are possible.

Bone and Bones↗

PubMed1982

[Initial clinical experiences with the fast digital picture of roentgen transmission profiles in the human (the chronogram)].

By means of suitable hardware and software changes it becomes possible to obtain transmission profiles of high time resolution (up to 50 profiles/sec) with the help of a CT device which is suitable for the recording of digital radiographs, in one transversal body layer. In this manner, it becomes possible to measure changes in the density profile from 6 up to 50 sec and to analyse them. This method called "Chronogram", enables high-resolution recording of density changes, similar to kymography. The possibilities of using contrast media are demonstrated by means of phantom measurements, and initial clinical experiences are outlined on the basis of practical examples.

Abdominal Neoplasms↗

PubMed1981

Monte Carlo calculations of x-ray scatter data for diagnostic radiology.

X-ray scatter data have been calculated by Monte Carlo methods for diagnostic radiology applications. The scatter intensities relative to the primary intensities are given for different detectors for various values of object thickness, field size, object-to-detector distance, and primary energy. The results are compared the those from previous investigations. The calculations made it possible to resolve contradictions in published measurements regarding the dependence of scatter intensities on primary X-ray energy and detector response.

Models, Theoretical↗

PubMed1981

[Computerized tomography in ORL-diseases. II. High resolution-CT of the paranasal sinuses].

Computerized tomography of the paranasal sinuses so far was restricted to imaging soft tissue structures. By means of new high resolution algorithms spatial resolution has been improved significantly without any increase in patient dose. Thereby a clear delineation of fine structures and of the transitions from bone to mucosa and air has been achieved. The scope of applications is thus extended to the diagnosis of purely osseous processes like fractures and osteoplastic changes for example. Computerized tomography, therefore, is the method of choice for most diseases of the paranasal sinuses.

Fractures, Bone↗

PubMed1979

Reduction of dose in pelvic examinations of infants using modern X-ray techniques.

A simple dose-saving procedure for the diagnosis of congenital hip dysplasia employing a diaphragm in near-focus position is presented. Doses to the skin and the gonads are measured with a phantom, comparing the new and other techniques. With optimal techniques the skin dose is smaller than 2 mR and the gonadal doses lie around 0.1 mR for both male and female patients.

Age Factors↗

PubMed1979

[Futher means for reducing radiation dose during exposure of the pelvis in infants (author's transl)].

A simple dose-saving procedure for the diagnosis of congenital hip dysplasia employing a diaphragm in nearfocus position is presented. Doses to the skin and the gonads were measured with a phantom for the new and other techniques. With optimal techniques the skin dose is smaller than 2 mR and the gonadal doses lie around 0.1 mR for both male and female patients. An estimate of the dose burden from undesired radiation is appended.

Female↗

PubMed1977

Tomogram degradation due to eye shielding and collimation.

Phantom-image, line-pair resolution and anterior eye exposure have been measured to determine the optimum collimation and eye shielding for petrous temporal tomography. Small round collimation and 0.5-1.0-mm lead equivalent eye shields are recommended. This reduces eye exposure to 10% of the usual dose without changing line-pair resolution.

Eye↗

PubMedDate not supplied

The wash-in/washout protocol in stable xenon CT cerebral blood flow studies.

PURPOSE: We conducted a comparative study to optimize the scanning and inhalation protocols for xenon CT cerebral blood flow (CBF) examination (Xe CT), with the aim of improving the practical performance of Xe CT as a routine clinical examination. MATERIALS AND METHODS: Four different inhalation protocols, including 3-min, 6-min, and 8-min wash-in protocols, and a 3-min wash-in/5-min washout protocol, were compared in five healthy volunteers. Each subject underwent two serial Xe CT examinations with an interval of 30 min between the first one (wash-in) and the second one (wash-in/washout). A computer simulation was also performed to support the results of the clinical study. The rate of success was calculated from our experience of 110 clinical cases examined with the wash-in/washout protocol over the last 9 months. RESULTS: The mean CBF values with 6-min and 8-min wash-in protocols were 59.0 and 59.5 mL/100-g brain per min in the thalamus, and 19.5 and 19.0 mL/100-g brain per min in the frontal white matter, respectively. The mean CBF values with 3-min wash-in/5-min washout protocol were 60.0 mL/100-g brain per min in the thalamus and 18.5 mL/100-g brain per min in the frontal white matter, respectively. Computer simulation showed improved signal-to-noise ratio by employing the 3-min wash-in/5-min washout protocol instead of 8-min wash-in protocol for the same number of data points. The rate of success improved to 99.1% due to the significant decrease in head motion with the shorter period of inhalation. CONCLUSION: A wash-in/washout protocol is a useful alternative in Xe CT CBF measurement and more useful than the wash-in method for clinical purposes.

Administration, Inhalation↗