Biomedical subjects

L Jangland

Publications and source records attributed to L Jangland.

3 recordsLinked to original sources

PubMed2005

Artifacts in 3D rotational angiography: an experimental study.

PURPOSE: To investigate artifacts in three-dimensional rotational angiography (3D-RA) in an experimental model and to evaluate which parameters influence their distribution. MATERIAL AND METHODS: 3D-RA was carried out in a circular vessel phantom filled with contrast medium. Two different rotational angulations were used: 160 degrees causing 64 images and 180 degrees causing 90 or 120 images. The images were transferred to one workstation for reconstruction of axial slices and then to another workstation for 3D reconstructions. The 3D reconstructions were compared with standardized threshold settings. RESULTS: The artifacts occurred where the vessel had a longer path parallel to the rotation plane and became increasingly pronounced when the threshold level was raised. The artifacts decreased in size when rotation angle and number of projections were increased. CONCLUSION: The quality of the 3D reconstructions from RA was degraded by beam-hardening and sampling artifacts. The sampling artifacts were diminished by increasing both the rotation angle and the number of projections. The distortions in the 3D reconstructions caused by beam-hardening remain to be resolved. The threshold values also had a considerable influence on the 3D reconstructions.

Angiography↗

PubMed2004

Dose reduction in computed tomography by individualized scan protocols.

PURPOSE: To find a method of adjusting the mAs-value in relation to the size of the patient undergoing computed tomography (CT) examination as a means of minimizing the radiation dose to the patient. MATERIAL AND METHODS: A correction factor to be applied on the tube charge for each patient was calculated using two mathematical methods. This approach was tested on 4 Perspex phantoms of different sizes and geometries. Noise was measured in the images with and without use of the correction factors. Retrospectively, correction factors were calculated for 12 CT examinations of the abdomen and the dose reduction was estimated for these patient studies. RESULTS: The variations in noise measured in the images of the different phantoms were dramatically reduced by both methods. The retrospectively performed patient study showed that the largest correction factor was 7 times greater than the smallest, which means that a dose reduction factor of 7 is possible in the extreme case. CONCLUSION: Our proposed methods of adjusting the applied tube charge (mAs-value) in relation to the size of the patient can be used on the vast majority of CT systems. The potential for dose reduction is great, especially for small patients.

Humans↗

PubMed1990

Niobium filters for dose reduction in pediatric radiology.

The performance of a niobium filter, with K-edge at 19 keV, and a copper filter have been studied concerning absorbed dose, image quality and tube loading. Absorbed doses were measured with TLD. To evaluate image quality a perspex phantom with image quality test objects was used. In comparison with a conventional filter made of copper no significant advantage was obtained with the niobium filter.

Copper↗