The place of radioisotopic lung function studies in paediatrics

The contribution of perfusion scintigraphy in the evaluation of children suffering from recurrent localized pneumonia

The value of perfusion scintigraphy as a screening test for children who have suffered from several episodes of recurrent localized pneumonia was evaluated in 32 patients aged 1-15 years. Perfusion studies were carried out using macroaggregated albumin (MAA) labeled with technetium 99m. In 9 patients (28%), large lobar or multisegmental perfusion defects were demonstrated. Their final diagnoses proved to be bronchiectasis (5 patients), bronchomalacia (2 cases), agenesis of a lobe (1 subject), and lobar sequestration (1 patient). In 23 children (72%), the perfusion scintigraphic patterns were normal or diffusely nonhomogeneous. All of these patients improved clinically on a 1- to 2.9-year follow-up. We conclude that a normal perfusion scintigraphy is a useful screening test for excluding structural lung abnormalities in pediatric patients with recurrent localized pneumonia. Children showing a pattern of lobar or multisegmental perfusion defects should be further investigated to rule out structural abnormalities as an underlying cause of disease.

Differential lung function in an infant with the Swyer-James syndrome

A previously healthy two year old boy had an adenoviral infection at the age of 13 months and developed hyperlucency of the left lung, chronic respiratory distress, and failure to thrive. Bronchodilators and steroid treatment had no effect. Radionuclide lung scans using an intravenous bolus of xenon-133 both before and after treatment showed substantially reduced function on the hyperlucent side and modestly reduced function on the other side. Fibreoptic bronchoscopy showed no structural abnormalities. Partial forced expiratory flow volume (PEFV) curves, generated from end inspiration by rapid compression of the chest wall with an inflatable jacket, were obtained from the total respiratory system and from each lung separately by inflating a Fogarty catheter in the contralateral mainstem bronchus. Expiratory flow rates and volumes during both tidal breathing and PEFV manoeuvres were considerably decreased in the hyperlucent lung. PEFV curves from the "healthy" right lung and from the total respiratory system were similar in shape and showed a moderately obstructive pattern. The right lung ventilated about four times as much as the left when measured by bronchospirometry and about three times as much when measured by the radionuclide technique. The lung scans appeared to reflect adequately the functional abnormality in this infant with the Swyer-James syndrome.

Clinical applications of nuclear medicine

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Relation between clinical and roentgenological scores and measures of lung function in cystic fibrosis, with special reference to pulmonary Xenon133 elimination

Regional lung function (RLF) with Xenon133 was investigated in 40 patients with cystic fibrosis (CF) aged 5-28 years (mean 13) at 1-5 occasions during a 3-year period. The RLF was determined with a 4-collimator system and evaluated with a score based on the following parameters: (1) time of elimination of injected isotope and (2) of inhaled isotope, (3) regional ventilation, (4) regional perfusion and (5) ventilation-perfusion ratios. The results were related to spirometry, X-ray score (according to a modification of Chrispin and Norman) and clinical score (according to Shwachman and excluding X-ray), which were all assessed in the same day. RLF correlated to clinical (P less than 0.01) and radiological score (P less than 0.01) and to residual volume (P less than 0.001) and the ratio between one second forced expiratory volume to vital capacity (FEV%) (P less than 0.01), but much higher correlations were found between X-ray score, clinical score and different spirometric variables. We therefore conclude that RLF can be used in patients too young to cooperate in spirometry but that it is of less clinical value in older patients with CF.

Quantitative ventilation-perfusion lung scans in infants and children: utility of a submicronic radiolabeled aerosol to assess ventilation

The quantitative assessment of regional pulmonary ventilation and perfusion provides useful information regarding lung function. Its use in infants and young children, however, has been minimal because of practical and technical limitations when the distribution of ventilation is assessed by radioactive gases. In 16 infants and children we used an inexpensive commercially available nebulizer to produce a submicronic aerosol labeled with 99mtechnetium-diethylenetriamine pentacetic acid to assess ventilation quantitatively, and intravenous injections of 99mtechnetium-labeled macroaggregates of albumin to assess pulmonary perfusion quantitatively. Studies were safely completed in both ambulatory and critically ill patients, including two premature infants who had endotracheal tubes in place for ventilatory support. No sedation or patient cooperation is required. This technique enables any department of nuclear medicine to measure regional pulmonary ventilation and perfusion in infants and children.

Regional lung function in children: the accuracy of nitrogen-13 inhalation and infusion studies

The assumptions made in 13N lung function tests in children with pulmonary or cardiac disorders have been examined. The index of lung function employed was the height/area (H/A) of the lung curves obtained following either bolus inhalation or infusion of 13N. Three aspects were considered: (1) the accuracy of H/A values with count rates obtained in typical patients; (2) the effect on perfusion H/A values of prolonged arrival of isotope in the lungs; and (3) the effect on perfusion H/A values of recirculation of isotope through the lungs due to a right-to-left intracardiac shunt. It was found that, for inhalation studies, the index H/A was sufficiently accurate to distinguish localised from generalised disease. For perfusion studies, prolonged arrival of isotope in the lungs caused a reduction in measured H/A values of up to 15%. In the presence of a right-to-left shunt recirculation of isotope could prevent the detection of a small, poorly-ventilated lung component. It is concluded that the use of 13N for measurement of ventilation/perfusion balance is not a sensitive method for monitoring the progress of generalised pulmonary disease.

Clinical applications of radionuclide lung scanning in infants and children

Krypton 81m ventilation and technetium 99m perfusion lung scans in anterior, posterior and oblique views in 86 children (age range 14 days to 15 years) with various paediatric problems were obtained. On reviewing these studies we found four main areas of clinical usefulness. (a) Establishing the diagnosis; in a relatively small number of patients the lung scan was essential for either establishing the exact diagnosis or directing attention to the abnormal area. (b) Refuting a diagnosis: the two main groups in this category include possible bronchiectasis and inhaled foreign body. (c) Establishing the extent of the disease; radionuclide studies enable one to assess and follow up the extent of the disease in children with lower respiratory problems; a lung scan may obviate the need for bronchography in bronchiectatics failing to respond to medical treatment and for whom surgery is being considered. Repeat studies are useful in following the natural history or the response to treatment of various lung conditions. (d) Assessing the success of surgical procedures on the heart and on abnormal pulmonary arteries. We indicate that 81Krm ventilation/99Tcm perfusion scanning are particularly useful in small children in whom tests of overall pulmonary function cannot be carried out because of lact of co-operation.

Relationship between the chest radiograph, regional lung function studies, exercise tolerance, and clinical condition in cystic fibrosis

This study evaluated the accuracy of the interpretation of the chest film in delineating localised abnormalities of ventilation and perfusion, as well as the overall severity of airways obstruction, exercise tolerance, and clinical condition in children with cystic fibrosis. Radiographic findings in various regions of the chest film were compared with the functional values obtained with regional lung function tests which evaluated the arrival and disappearance of boluses of radioactive nitrogen given by inhalation and infusion. While the more severely affected areas on the chest radiograph were found to correlate with similar regions on the lung function tests, as did overall scores, errors occurred in some cases if the x-ray film alone was used as a judge of regional physiological derangement. In addition the degree of airways obstruction, the exercise tolerance on a cycle ergometer, and clinical grading, each correlated significantly with the radiographic score. We conclude that the chest radiograph is a good indicator of the overall severity of the lung disease and that it correlates well with exercise tolerance and clinical condition in cystic fibrosis.

Pulmonary scintigraphy in pediatrics

Pulmonary radionuclide studies in children provide reliable information on regional lung perfusion and ventilation. They are easily and safely performed and they do not usually require full patient cooperation. Their clinical indications and applications are not as well defined as and frequently differ from those in pulmonary disorders of the adult patient. Radiation exposures resulting from radionuclide pulmonary examinations are well within acceptable limits set up for a variety of radiologic diagnostic procedures. Our lung scanning experience with a spectrum of congenital and acquired cardiopulmonary diseases is presented and the contribution of the radionuclide methods to the specific problems facing the pediatrician or the surgeon is discussed.