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K T Karila

Publications and source records attributed to K T Karila.

6 recordsLinked to original sources
PubMed1997

Computing patient doses of X-ray examinations using a patient size- and sex-adjustable phantom.

Both the use of traditional fluoroscopy and the increasing use of modern digital techniques in radiology and interventional radiology demand the development of versatile computer programs for patient dose determinations. Long computing times restrict the use of Monte Carlo (MC) methods in dose monitoring applications where the radiological views change frequently. In the Organ Doses Calculation Software application (ODS-60), the phantom model is similar in principle to the Alderson-Rando (A-R) phantom, but its sex, size and shape is modified according to a particular patient. Organ and effective doses are computed online (in a few seconds) using a method similar to the traditional dose planning systems used in radiotherapy. In this paper, the new ODS-60 software is presented in detail and its capabilities are demonstrated. Software performance was determined by comparing the results with those from independent methods. In the case of a reference man-sized male, the effective dose was about 7% larger than the effective dose given in another publication. In the case of a reference woman-sized female, the disagreement with the other method was greater (33%). Anatomical differences between the phantom models (ODS-60 and MC) were found to be the main reasons for these findings. This paper shows the advantage of using a patient size- and sex-adaptable phantom for patient dose determinations; the conversion coefficient from entrance surface dose-to-effective dose ratio between male (170 cm, 85 kg) and a female (160 cm, 43 kg) varies in the range 1.5-2.

Anthropometry↗
PubMed1988

Quality control of mammographic equipment: a 5-year follow-up.

A quality-control project covering 56 pieces of mammographic equipment was carried out in Finland. The evaluation was based on the determination of contrast, film optical density, resolution, focus size, tube voltage, exposure time, half-value thickness, reproducibility and linearity of exposure, surface and exit dose, and defects at each centre when employing routinely used techniques. Dose and image quality were assessed using three phantoms. The results are compared with those obtained 5 years earlier and by other authors. Although the situation has, in many ways, improved considerably over the last 5 years (for instance, the average whole-breast dose has fallen on average by 84%, 7.37----1.10 mGy), there is still room for further improvement, especially in the optimization of the developing processes.

Female↗
PubMed1987

Image quality of mammographic systems.

The image quality in mammography was evaluated for all the 56 equipment-image receptor combinations used in Finland with two phantoms containing test objects of three types and different sizes. We obtained 2-8 fold variations for the smallest sizes of the three objects (specks, fibres and masses) visible in the X-ray images and 3.0-3.7 fold variations for an "image score". The smallest speck, fibre and mass sizes visible in the radiographs were 0.24, 0.75 and 0.5 mm, respectively. An unacceptable image quality was obtained in 36% of the studied cases. A recommendation is presented.

Breast Neoplasms↗
PubMed1982

Performance of x-ray generators and unnecessary dose in mammography.

All x-ray equipment used for mammography in Finland was studied and performance assessed. Numerous functional differences and malfunctions were found in the generators. Medically unproductive absorbed skin dose varied from 0.15 to 130 mrad (1.5-1,300 microGy) per exposure for an average breast. Corrective actions are recommended.

Background Radiation↗
PubMedDate not supplied

Performance of automatic exposure controls in mammography.

This study describes the phantoms and methods for performance evaluation of 23 phototimers used in mammography. The evaluation is primarily based on an analysis of the optical densities of image receptors (films). According to the results, the kVp compensation, the response capability, the saturation, and the density controls of the phototimers are very poor. The variation in optical film density exceeded +/- 0.3 optical density (OD) in 87% of the phototimers for the tube voltage range 25-40 kVp and for the 2-6-cm-thick phantoms. The operation of the density controls should be adjusted in 70% of the phototimers. Recommendations are presented.

Evaluation Studies as Topic↗