Biomedical subjects

K Tägil

Publications and source records attributed to K Tägil.

3 recordsLinked to original sources

PubMed2001

An independent evaluation of a new method for automated interpretation of lung scintigrams using artificial neural networks.

The purpose of this study was to evaluate a new automated method for the interpretation of lung perfusion scintigrams using patients from a hospital other than that where the method was developed, and then to compare the performance of the technique against that of experienced physicians. A total of 1,087 scintigrams from patients with suspected pulmonary embolism comprised the training group. The test group consisted of scintigrams from 140 patients collected in a hospital different to that from which the training group had been drawn. An artificial neural network was trained using 18 automatically obtained features from each set of perfusion scintigrams. The image processing techniques included alignment to templates, construction of quotient images based on the perfusion/template images, and finally calculation of features describing segmental perfusion defects in the quotient images. The templates represented lungs of normal size and shape without any pathological changes. The performance of the neural network was compared with that of three experienced physicians who read the same test scintigrams according to the modified PIOPED criteria using, in addition to perfusion images, ventilation images when available and chest radiographs for all patients. Performances were measured as area under the receiver operating characteristic curve. The performance of the neural network evaluated in the test group was 0.88 (95% confidence limits 0.81-0.94). The performance of the three experienced experts was in the range 0.87-0.93 when using the perfusion images, chest radiographs and ventilation images when available. Perfusion scintigrams can be interpreted regarding the diagnosis of pulmonary embolism by the use of an automated method also in a hospital other than that where it was developed. The performance of this method is similar to that of experienced physicians even though the physicians, in addition to perfusion images, also had access to ventilation images for most patients and chest radiographs for all patients. These results show the high potential for the method as a clinical decision support system.

Adolescent↗

PubMed2000

Automated interpretation of ventilation-perfusion lung scintigrams for the diagnosis of pulmonary embolism using artificial neural networks.

The purpose of this study was to develop a completely automated method for the interpretation of ventilation-perfusion (V-P) lung scintigrams used in the diagnosis of pulmonary embolism. An artificial neural network was trained for the diagnosis of pulmonary embolism using 18 automatically obtained features from each set of V-P scintigrams. The techniques used to process the images included their alignment to templates, the construction of quotient images based on the ventilation and perfusion images, and the calculation of measures describing V-P mismatches in the quotient images. The templates represented lungs of normal size and shape without any pathological changes. Images that could not be properly aligned to the templates were detected and excluded automatically. After exclusion of those V-P scintigrams not properly aligned to the templates, 478 V-P scintigrams remained in a training group of consecutive patients with suspected pulmonary embolism, and a further 87 V-P scintigrams formed a separate test group comprising patients who had undergone pulmonary angiography. The performance of the neural network, measured as the area under the receiver operating characteristic curve, was 0.87 (95% confidence limits 0.82-0.92) in the training group and 0.79 (0.69-0.88) in the test group. It is concluded that a completely automated method can be used for the interpretation of V-P scintigrams. The performance of this method is similar to others previously presented, whereby features were extracted manually.

Adolescent↗

PubMed2000

Efficient lung scintigraphy.

Lung scintigraphy is a first-choice method to diagnose lung embolism. The clinical routine in most centres is a perfusion study complemented with a ventilation study when judged necessary. We describe a routine with ventilation scintigraphy preceding perfusion scintigraphy, which is completed within one hour. Furthermore, the data acquired allow the determination of lung clearance of the tracer 99mTc-DTPA (diethylene triamine penta-acetate) used for the ventilation scintigraphy. An aerosol generator charged once a day with 99mTc-DTPA solution is used for all inhalations during the day. Inhalation is monitored with a counter and interrupted when the count rate corresponds to about 20 MBq. The ventilation imaging starts and ends with posterior projections. This allows calculation of lung clearance of 99mTc-DTPA. Perfusion scintigraphy is performed in a standard fashion with 100 MBq of 99mTc-MAA (macro-aggregated albumin). The ventilation study was considered to give some diagnostic information in the majority of the patients. The clearance determination allows detection of inflammatory lung disease. The background activity caused by the ventilation study comprised only 13% of the activity in the perfusion scintigraphy and did not significantly interfere with interpretation of the perfusion scan. The cost for the investigation is low because of the rational system for aerosol administration and the short time for a complete study.

Humans↗