Factor analysis of 81mKr lung ventilation studies

Factor analysis of dynamic structures (FADS) summarizes data depending on time and space in a few elementary components. Each of them associates a time-activity curve (factor) and the spatial distribution of the corresponding events. The aim was to evaluate the patterns, the number of components, and their possible link to physiology when FADS was applied to scintigraphic images representing a composite of a 81mKr ventilation cycle. In a study of 26 patients (10 normal, 16 pathologic), components were found that represent: (1) a rapid and steeply changing ventilation factor, corresponding mainly to bases in normal subjects and whole lung fields in patients, (2) a slower expiration and shorter inspiration ventilation factor distributed throughout both lung fields in all patients, (3) a constant activity curve, with an inspiratory activity peak distributed over both lung fields and the large airways, and (4) a factor including a phase shift with respect to the first; this was found significantly more often in patients with pathology.     

An extension set for 81Rb-81mKr solution generators for lung ventilation studies

For ⁸¹Rb-^81mKr solution generators, an extension set has been developed, which strips the ^81mKr from the liquid eluate with a stream of air for use in lung ventilation studies. Via a three-way valve the ⁸¹Rb-^81mKr solution generator can be operated alternately in the perfusion mode or in the ventilation mode. Measurements and calculations have been performed to get more insight into the parameters of interest for an optimum design of the extension set and its operation conditions.     

A new high flow 81Rb/81mKr generator

Using an ion-exchange membrane a Krypton-81m generator for ventilation has been developed which is compact, allows elution with high flowrates and gives higher extraction yields than the normally used column generator.     

A 81Rb/81mKr generator made by ion implantation

Isotopically pure ⁸¹Rb was implanted in plastic foils, and the daughter-^81mKr was eluted quantitatively by air or by a 0.9% NaCl solution. The elution yield, the purity of the ^81mKr, and the washing-out losses of ⁸¹Rb were studied as functions of the implantation density. It was seen that the densities below 5 × 10¹² Rb atoms/cm² provide a high yield for elution both by liquid and air. The first 100 MBq implantation-type generator was tested by making a lung-ventilation study in man.     

A breathing lung phantom for 81mKr lung ventilation studies its use in dosimetry and quality control

The construction of a breathing lung phantom that can be used to measure the amount of radioactive gas in the lungs as well as to determine the absorbed dose is described. For a lung ventilation study that consists of 6 views of 300 kents each, an effective dose equivalent of 50 Sv was calculated. The phantom is also suitable for comparison of different generator systems.     

A breathing lung phantom for 81mKr lung ventilation studies its use in dosimetry and quality control

The construction of a breathing lung phantom that can be used to measure the amount of radioactive gas in the lungs as well as to determine the absorbed dose is described. For a lung ventilation study that consists of 6 views of 300 kcnts each, an effective dose equivalent of 50 microSv was calculated. The phantom is also suitable for comparison of different generator systems.     

Provocation test for children with bronchial asthma monitored by 81mKr ventilation and perfusion lung scans

A provocation test of bronchial asthma was performed on two children. The test involved the continuous inhalation of krypton-81m gas and intermittent intravenous injections of krypton-81m glucose solution. The patient's response was carefully monitored in order to clarify the relationship between the time of the appearance and the intensity of ventilation and perfusion defects. The bronchial sensitivity of each patient was determined according to the dose of allergen or bronchoconstrictor delivered before the first ventilation defects were observable. The test was sensitive enough for the children not to develop asthmatic symptoms during and after the test. The results showed that perfusion defects appeared after ventilation defects and were less intense. The perfusion defects disappeared rapidly and before the ventilation defects had become undetectable.     

Provocation test for children with bronchial asthma monitored by 81mKr ventilation and perfusion lung scans

A provocation test of bronchial asthma was performed on two children. The test involved the continuous inhalation of krypton-81m gas and intermittent intravenous injections of krypton-81m glucose solution. The patient's response was carefully monitored in order to clarify the relationship between the time of the appearance and the intensity of ventilation and perfusion defects. The bronchial sensitivity of each patient was determined according to the dose of allergen or bronchoconstrictor delivered before the first ventilation defects were observable. The test was sensitive enough for the children not to develop asmatic symptoms during and after the test. The results showed that perfusion defects appeared after ventilation defects and were less intense. The perfusion defects disappeared rapidly and before the ventilation defects had become undetectable.     

Mismatch between 99mTc-DTPA aerosol and 81mKr lung ventilation scintigraphy: a pitfall of radionuclide imaging

Pulmonary ventilation and perfusion scintigraphies were performed using 99mTc-MAA, 81mKr, and 99mTc-DTPA aerosol in a patient with asthma. Lung perfusion scintigraphy and 99mTc-DTPA aerosol scintigraphy showed multiple matching defects, however, 81mKr ventilation scintigraphy showed mismatch with lung perfusion scintigraphy. A pitfall of this examination was discussed.     

Mismatch between99mTc-DTPA aerosol and81mKr lung ventilation scintigraphy: a pitfall of radionuclide imaging

Pulmonary ventilation and perfusion scintigraphies were performed using^99mTc-MAA,^81mKr, and^99mTc-DTPA aerosol in a patient with asthma. Lung perfusion scintigraphy and^99mTc-DTPA aerosol scintigraphy showed multiple matching defects, however,^81mKr ventilation scintigraphy showed mismatch with lung perfusion scintigraphy. A pitfall of this examination was discussed.     

81mKr: Production,application, and use of computer for ventilation studies

Theoretical excitation functions have been used for the production of neutron-deficient rubidium isotopes by (, kn) reactions on ⁷⁹Br and ⁸¹Br. Krypton generators have been produced using the internal beam of the cyclotron of the Rudjer Bokovi Institute. New methods for target preparation and radiochemical separation have been developed.Preliminary clinical studies have been performed with the aim of investigating the possible use of krypton generators in conjunction with a gamma camera and a digital computer.The digital computer was used to normalize images of regional ventilation and to calculate and display isoventilation regions.Clinical examples of images of regional ventilation that permit resolution between nonventilated and well-ventilated regions are given.     

Improved version of the wetted-paper 81Rb/81mKr generator. Influence of porous capillary spreading and diffusion on the performance

The performance of the Rb/Kr generator based on sorption of ⁸¹Rb solution in paper was investigated for various design modifications. Replacement of the ridged copper-foil separator between adjacent paper layers by ridged paper resulted in a more rapid attainment of the equilibrium elution efficiency and a more compact geometry. This is explained by the nature of the spreading process of water via the pores in the paper. Also the influence of the water concentration in the paper on equilibrium efficiency, drying rate, and pressure drop is related to this mechanism. A range of water concentrations (0.1–0.8 mL/g of paper) could be indicated where the equilibrium efficiency (>90%) is not limited by diffusion out of the larger pores (>0.9 mL/g) and where the “run-dry” phenomenon does not occur (<0.1 mL/g).     

81mKr ventilation and 99mTc perfusion scans in chest disease: comparison with standard radiographs.

In 75 patients with various pulmonary disorders, ventilation and perfusion scans were obtained in multiple views with the 81mKr/99mTc technique and compared with an evaluation of regional ventilation and perfusion derived from the standard chest radiograph. In emphysema, the chest film correlated poorly with ventilation-perfusion scans, showing a trend to underestimate the functional impairment. In chronic bronchitis and asthma, large segmental defects observed on both ventilation and perfusion scans were associated with a normal chest radiograph. Typical findings in pulmonary embolism were segmental defects on perfusion scan with normal ventilation scan and clear lung fields on the chest film. In chronic left heart disease, plain films were inaccurate in predicting alteration of the base-to-apex perfusion gradient observed on the scan.     

81mKr gas and 99mTc-MAA V/Q ratio images for detection of V/Q mismatches

Methods for creating ventilation/perfusion ratio images have been reported previously using radioxenon. With the availability of 81mKr gas, corresponding ventilation and perfusion views in multiple projections to evaluate for V/Q mismatch may be performed more readily. A technique for the creation of a functional V/Q ratio image to highlight V/Q mismatches to aid in the evaluation of pulmonary embolism is described. By removing nonpertinent and distracting information and by converting a 'cold spot' imaging modality to a 'hot spot' modality, these functional images aid in the synthesis of the information provided by the ventilation and perfusion images. The limitations due to technical artifacts and the advantages of using these functional images are described.