UK audit and analysis of quantitative parameters obtained from gamma camera renography

The purpose of this study was to perform an audit of quantitative values obtained from gamma camera renography in the UK. Ten patient image sequences representing normal and pathological renal function were obtained from archived studies and distributed to hospitals in the UK. Hospitals were asked to measure five parameters: relative function, renogram time-to-peak (left and right), and whole kidney mean transit time (left and right). Details of methodology, software used and operator experience were requested. This allowed the influence of operational factors on variations in reported values to be examined. A total of 180 responses from 81 hospitals were received. Values reported for the parameters, together with other details supplied, were entered into Excel and SPSS for statistical analysis. Histograms representing the distribution of values were produced for each parameter. The largest variations were found for mean transit time and occasionally for time-to-peak. The effect of factors was assessed using non-parametric statistical tests applied independently to each renogram. For all the parameters, the hospital, UK region, supplier, computer and software version influenced variations in the reported values. Algorithm and site of background region were influencing factors for relative function, the background subtraction method influenced time-to-peak, and curve smoothing influenced mean transit time

UK audit of single photon emission computed tomography reconstruction software using software generated phantoms

The purpose of this study was to undertake an audit of the quantitative characteristics of single photon emission computed tomography software using projection data from an analytically generated software phantom and a measured line source. The phantom consisted of three structures. A uniformly filled cylinder, a series of cylindrical rods of various diameters in a background activity with a rod to background ratio of 2 : 1 and lastly, a set of three concentric rings of activity in the ratio 1 : 0 : 1. The phantom contained no added statistical noise. No attenuation was imposed on the data. The phantom was generated analytically and projections were distributed at six different count densities. A single set of projections from a thin line source was also distributed. These data were distributed to centres throughout the UK. Centres were asked to reconstruct the data using a 'ramp only' reconstruction with no additional smoothing function applied. Data were requested for mean and standard deviation in the uniform cylinder, the maximum counts for each cylindrical rod and the mean counts in regions placed within the concentric rings. For the measured line source, centres were asked to measure the full width at half maximum and peak pixel counts for a profile through the reconstructed line. Results from 115 systems were obtained from 100 centres throughout the UK. These provided data from 12 software providers, 11 of these being commercial companies. Data were compared with the known input values and histograms of the distribution of results obtained. Significant differences in quantitative parameters were noted for the different input count densities as well as between suppliers and revisions of software from single suppliers

UK audit of left ventricular ejection fraction estimation from equilibrium ECG gated blood pool images

Purpose: To examine the variability of results obtained from computer analysis of left ventricular gated blood pool (LVGBP) images by nuclear medicine centres in the UK.Methods: Twelve data sets of LVGBP images were distributed via commercial software suppliers to nuclear medicine centres in the UK. Two of the data sets were duplicates and three were acquired from the same patient with different total counts in the images. The quality of the images was also variable and two images had poorly defined left ventricular walls. A questionnaire was used to identify the parameters used during the analysis and to give an indication of the number of LVGBP scans per year routinely carried out by each centre as well as report the results obtained from the analysis.Results: Results were received from 63 nuclear medicine centres using 77 computer systems. The vast majority of participants (57) carried out fewer than 10 scans per month. Only two centres performed more than 30 scans per month. Sixteen centres did not quote a minimum normal value for left ventricular ejection fraction (LVEF) and 36 did not record a maximum value. The remainder recorded between 0.40 and 0.60 for the minimum of normal range and 0.60-0.90 for the maximum of normal range. Analysis of returns showed that LVEF estimates for the data sets were highly variable between centres and computer systems. The overall standard deviation of results compared to the mean for each study was 0.076. Approximately half this variation was due to systematic variation between centres. The overall precision taking into consideration this systematic variation, was 0.055. Lower variability was found between studies with higher overall counts and this was highly significant