We have investigated the effect of acute and long-term bronchodilator treatment on the distribution of ventilation and perfusion in 15 asthmatics using a gamma camera, krypton-81m (for ventilation) and technetium-99m macroaggregate (for perfusion). Individual peak expiratory flow (PEF) values before bronchodilation were slightly or moderately below the predicted values. The simultaneous ventilation images (analysed visually) showed areas of delayed ventilation in all patients (mean distribution score on 3-point scale 2.1). After isoprenaline inhalation (240 micrograms) the mean PEF increased by 24%, but the distribution of ventilation remained virtually unchanged in all patients (mean score 2.0). Simultaneously defects in perfusion could be seen in all patients (mean score 1.5). After intensive treatment, when the mean PEF increased by a further 29%, the distribution scores of ventilation and perfusion fell to 0.8 and 0.9, respectively. The results indicate that, without intensive and long-term treatment, appreciable inequality of ventilation and perfusion are usual consequences of asthma; and suggest that although larger airways are dilated by isoprenaline inhalations residual bronchial obstruction may still remain in some smaller airways, maintaining uneven distribution. Perfusion disturbances seem to be secondary to changes in regional ventilation.

https://thorax.bmj.com/content/thoraxjnl/37/7/516.full.pdf

Effects of acute and long-term bronchodilator treatment on regional lung function in asthma assessed with krypton-81m and technetium-99m-labelled macroaggregates.

We have used asthma as a model of airways disease to test how well an automated, quantitative method of analysis of lung scans correlates with physiological measurements of disturbed lung function and gas exchange We studies 25 asthmatics (age 16–73) of widely differing severity (forced expiratory volume in 1-s (FEV1) 22% 123% of predicted value), who had airways tests, arterial blood gas analysis, and krypton-technetium lung scans within a short time of each other In all patients with airways obstruction and in some with normal function during remission, scans showed the typical appearances of multiple defects of ventilation and perfusion The severity of ventilation defects was computed from the posterior view of the krypton scan compared to an age- and sex-matched normal range to yield an underventilation score This correlated closely with the severity of airways obstruction as measured by forced expiratory manouevres Ventilation and perfusion defects were usually imperfectly matched; the severity of this was computed using a subtraction method applied to the counts on the posterior krypton and technetium scans The degree of mismatch was inversely related to the arterial partial pressure of oxygen (r=-086) The results suggest that computer scan analysis can provide useful functional information about the lung in airways disease

Lung scan abnormalities in asthma and their correlation with lung function

Lung volumes, calculated from 81Krm single-photon emission computed tomography (SPECT) of the lungs, were compared with functional residual capacity (FRC), measured with the helium dilution technique in controls and in patients with various pulmonary diseases. SPECT volume was greater than FRC, which was attributed to non-gas-containing structures in the lung such as the alveolar walls, the interstitium, the blood vessels and the blood, included in the SPECT volume. A good correlation (r = 0.91) was found between the two volumes and there was no difference in this relationship between patients and controls. It was concluded that the relative volume distribution, calculated from SPECT, can be used for the quantification of ventilation from 81Krm SPECT steady-state count distributions.

http://iopscience.iop.org/article/10.1088/0143-0815/9/2/007/pdf

Lung volume calculations from 81Krm SPECT for the quantification of regional ventilation

Technological developments over the past few years have led to substantial advances in medical organ imaging and a broadening of diagnostic radiology. Some ofthe new techniques use ionising radiation somewhat similar to orthodox radiology, as, for example, isotope scanning, but ultrasound and nuclear magnetic resonance use different physical principles to produce images. A further important factor is the noninvasive nature of such investigations. To some extent we are only at the beginning of the application of some of these newer techniques, and how far they will advance our ability to establish more accurate and definitive diagnoses cannot yet be predicted. Quite probably, however, the time may come when a reliable tissue diagnosis will become possible in vivo with results on a par with a histological interpretation of a biopsy specimen. The important question then will be how much further will advances in detailed diagnostic ability help the management of patients if these advances cannot be matched in treatment ? Such thoughts are entirely speculative at present and must not in any way influence our forward thinking in the application of the newer imaging techniques; but one further question will soon be widely asked-is the time coming when routine diagnostic radiology will be outdated and replaced by some of these ncw investigative techniques ? Again, this question cannot be fully answered at present, since our total experience is not broad enough to provide the final answer. At present the techniques discussed below are complementary and in no way competitive in their application.

https://www.bmj.com/content/bmj/284/6329/1590.full.pdf

New imaging techniques: their relation to conventional radiology.

SUMMARY

The current status of tests of regional lung function has been reviewed from the physiological and clinical standpoint. Recent technical innovations include the use of single photon and positron emission computerized tomography (SPECT and PET). For PET work, neon-19 (t1/7 17 sec) has been introduced as a ventilation tracer, and fluorine-18 deoxyglu-cose as a marker of glucose metabolism. Indium-111 labelled neutrophils have been studied. Physiological measurements of the distribution of blood flow and ventilation are concentrating on non-gravitational influences such as the pattern of force generation by the respiratory muscles and vasomotor tone. Ventilation and perfusion imaging of the lung with the gamma camera has established itself as an essential screening test for the diagnosis of pulmonary embolic disease. Inhalation of a radio-labelled aerosol of small particle size (1 μm) may be an acceptable substitute for a radioactive gas ventilation scan. Mucociliary clearance has been investigated with radionuclide techniques. Measurements of regional lung water have been replaced by tracers sensitive to alterations of epithelial (inhaled 99TCI-DTPA) or endothelial (i.v. 113inm-transferrin) permeability. New techniques using positron emission tomography, such as measurements of extravascular lung density, regional ventilation (19Ne) and regional glucose metabolism (18F-deoxy-glucose) have been discussed briefly.

Regional lung function: physiology and clinical applications.

Clinical value of krypton-81m and technetium-99m perfusion lung scanning.

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Clinical value of krypton-81m and technetium-99m perfusion lung scanning.