Michaela Moonen

Dynamics of 'Technegas' deposited in the lung.

n tomographic Technegas ventilation studies, the deposited aerosol should be stable. The aim of this study was to investigate the stability of deposited Technegas in severely obstructed patients and in healthy volunteers. Six emphysematous patients and five healthy volunteers were studied. Anterioposterior (AP) and posterioanterior (PA) dynamic images of ventilation (120 frames, 1 frame·min−1) were acquired after inhalation of 99mTc-‘Technegas’ in the supine position. The time-activity curve of the whole lung showed two phases in the emphysematous patients as well as in the healthy volunteers. The activity decreased rapidly in the first phase, then reached almost a constant level (the second phase) after approximately 50 min. The logarithms of both the first phase and the second phase were close to straight lines. The half-time of the first phase was approximately 9 min. No systematic differences in ‘Technegas’ clearance rate were found between central regions and peripheral regions and between high count rate regions and normal count rate regions. Pertechnegas contamination was subsequently detected, and we conclude that the rapid first phase is probably due to clearance of Pertechnegas. When stable Technegas is required, we suggest that data acquisition should start about 50 min after inhalation.

Evaluation of attenuation corrections using Monte Carlo simulated lung SPECT

SPECT (single photon emission computed tomography) images are distorted by photon attenuation. The effect is complex in the thoracic region due to different tissue densities. This study compares the effect on the image homogeneity of two different methods of attenuation correction in lung SPECT; one pre-processing and one post-processing method. This study also investigates the impact of attenuation correction parameters such as lung contour, body contour, density of the lung tissue and effective attenuation coefficient. The Monte Carlo technique was used to simulate SPECT studies of a digital thorax phantom containing a homogeneous activity distribution in the lung. Homogeneity in reconstructed images was calculated as the coefficient of variation (CV). The isolated effect of the attenuation correction was assessed by normalizing pixel values from the attenuation corrected lung by pixel values from the lung with no attenuation effects. Results show that the CV decreased from 12.8% with no attenuation correction to 4.4% using the post-processing method and true densities in the thoracic region. The impact of variations in the definition of the body contour was found to be marginal while the corresponding effect of variations in the lung contour was substantial.

Evaluation of various attenuation corrections in lung SPECT in healthy subjects

The effect of increasingly more sophisticated attenuation correction methods on image homogeneity has been studied in seven healthy subjects. The subjects underwent computed tomography (CT), single photon emission computed tomography (SPECT) and transmission computed tomography (TCT) of the thorax region in the supine position. Density maps were obtained from the CT and TCT studies. Attenuation corrections were performed using five different methods: (1) uniform correction using only the body contour; (2) TCT based corrections using the average lung density; (3) TCT based corrections using the pixel density; (4) CT based corrections using average lung density; and (5) CT based corrections using the pixel density. The isolated attenuation effects were assessed on quotient images generated by the division of images obtained using various attenuation correction methods divided by the non-uniform attenuation correction based on CT pixel density (reference method). The homogeneity was calculated as the coefficient of variation of the quotient images (CVatt), showing the isolated attenuation effects. Values of CVatt were on average 12.8% without attenuation correction, 10.7% with the uniform correction, 8.1% using TCT map using the average lung density value and 4.8% using CT and average lung density corrections. There are considerable inhomogeneities in lung SPECT slices due to the attenuation effect. After attenuation correction the remaining inhomogeneity is considerable and cannot be explained by statistical noise and camera non-uniformity alone.

Effects of lung volume reduction surgery on distribution of ventilation and perfusion

Lung volume reduction surgery (LVRS) results in functional improvements in most patients. The mechanisms behind the improvements are not clear. We hypothesized that reduced inequalities in ventilation to perfusion ratio (V/Q) may be a contributing explanation. Nine patients who underwent LVRS were investigated by ventilation and perfusion scintigrams before and after surgery. In addition, 8 healthy subjects were investigated once. The relative ventilation, perfusion and V/Q were calculated in 1 × 1 cm lung elements. Normal range of the element count‐rate was determined by the corresponding results in the normal subjects. Results of this small study show a significant effect of LVRS on V/Q, with reduction of shunt‐like elements. We conclude that the functional improvement after LVRS to some extent may be explained by decreased V/Q inequality.

Detection of chronic rejection by quantitative ventilation scintigrams in lung-transplanted patients: a pilot study

The suspicion of chronic rejection [bronchiolithis obliterans syndrome (BOS)] is usually based on deteriorating forced expired volume in 1 s. It is however, desirable to develop more sensitive methods as increased anti‐inflammatory therapy is thought to stop progression of the rejection. The aim of the present study was to develop quantitative tools based on ventilation scintigrams, to diagnose BOS. Sixteen double‐lung‐transplanted patients participated, six developing BOS and 10 who did not develop BOS. They were investigated with planar posterior–anterior 99mTc‐Technegas (Tetley Manufacturing Ltd, Sydney, Australia) ventilation scintigraphy at baseline, 6 months to 1 year post‐transplantation, and at a follow‐up examination 3–4‐year post‐transplant or in the BOS patients close to the time of the diagnosis. An automatic region of interest (ROI) was drawn on each lung in the scintigraphic image at baseline and also applied to the follow‐up investigation. The area inside the ROI was subdivided into stripes 10·8 mm high and squares 10·8 × 10·8 mm wide. Corresponding stripes and squares in baseline and follow‐up were analysed regarding differences in relative retention. The results show that the square analysis is superior. Applying chosen cut‐off values for square element differences, 6/6 right and 5/6 left BOS lungs were identified and one left and one right lung of patients not developing BOS were misclassified. We conclude that the square element difference appears to be a promising method to diagnose BOS.

Regional ventilation and distribution of emphysema: a quantitative comparison

The distribution of ventilation and emphysema throughout the lung was compared in 20 emphysematous patients who were candidates for lung volume reduction surgery. Ventilation distribution among 1·6‐cm‐high stripe regions was obtained in supine position by planar gamma camera scintigraphy after inhalation of technegas®. Results from nine healthy subjects provided normal stripe count rates. Patient count rates were expressed as the difference from predicted normal stripe count rate (ΔSVI). Thus, ΔSVI is a relative index of abnormal ventilation. Emphysema was assessed quantitatively by a density mask method on corresponding slices of high resolution computed tomography (HRCT). The results show that in the majority of patients, there is a highly significant relationship between the degree of stripe hypoventilation and the amount of distribution of emphysema, but in some patients no such relationship is found. We speculate that the distribution of airway obstruction not necessarily follows the distribution of emphysema, which could explain the lack of concordance between ventilation and emphysema distribution in some patients. We conclude that ventilation scintigraphy contains complementary information to lung HRCT.

Attitudes toward quality improvement among healthcare professionals: Lessons from a hospital-wide quality initiative

Purpose– The purpose of this article is to describe how the training of healthcare professionals in improvement work can be performed, and evaluate potential changes in attitude as a result of the initiative. Design/methodology/approach – The study was carried out at a University Hospital in Sweden. There were 443 participants in the study. The response rate before the intervention was 55 per cent (242 respondents) and six months later, it was 43 per cent (190 respondents). A two-day training program about quality improvement was performed on seven different occasions and after the training had been concluded, participants were encouraged to translate their newly acquired knowledge into improvement projects. Surveys on attitudes toward improvement work were completed by the participants right before the training and six months afterwards. The results were analyzed using a Mann-Whitney test. Findings– The analysis showed some statistically significant changes in attitude among the participants. There were also differences between groups of participants based on their profession and the number of years in their current position. Research limitations/implications – A limitation of the study is that it was solely based on attitudes expressed during the survey and did not include any observed changes in behavior. Another limitation is that attitudes after the intervention were only measured once. Originality/value– It is possible to use training to change attitudes toward improvement work. The result differs among groups of participants, which raises the question as to whether training should be tailored to better suit the needs of different groups to create positive change. Further research is needed regarding how to reach and fully implement a quality improvement mindset.