UK audit of analysis of quantitative parameters from renography data generated using a physical phantom.

BACKGROUND: In this second UK audit of quantitative parameters obtained from renography, phantom simulations were used in cases in which the 'true' values could be estimated, allowing the accuracy of the parameters measured to be assessed. MATERIALS AND METHODS: A renal physical phantom was used to generate a set of three phantom simulations (six kidney functions) acquired on three different gamma camera systems. A total of nine phantom simulations and three real patient studies were distributed to UK hospitals participating in the audit. Centres were asked to provide results for the following parameters: relative function and time-to-peak (whole kidney and cortical region). As with previous audits, a questionnaire collated information on methodology. Errors were assessed as the root mean square deviation from the true value. RESULTS: Sixty-one centres responded to the audit, with some hospitals providing multiple sets of results. Twenty-one centres provided a complete set of parameter measurements. Relative function and time-to-peak showed a reasonable degree of accuracy and precision in most UK centres. The overall average root mean squared deviation of the results for (i) the time-to-peak measurement for the whole kidney and (ii) the relative function measurement from the true value was 7.7 and 4.5%, respectively. These results showed a measure of consistency in the relative function and time-to-peak that was similar to the results reported in a previous renogram audit by our group. CONCLUSION: Analysis of audit data suggests a reasonable degree of accuracy in the quantification of renography function using relative function and time-to-peak measurements. However, it is reasonable to conclude that the objectives of the audit could not be fully realized because of the limitations of the mechanical phantom in providing true values for renal parameters.

A novel method for more accurately mapping the surface temperature of ultrasonic transducers.

This paper introduces a novel method for measuring the surface temperature of ultrasound transducer membranes and compares it with two standard measurement techniques. The surface temperature rise was measured as defined in the IEC Standard 60601-2-37. The measurement techniques were (i) thermocouple, (ii) thermal camera and (iii) novel infra-red (IR) "micro-sensor." Peak transducer surface measurements taken with the thermocouple and thermal camera were -3.7 ± 0.7 (95% CI)°C and -4.3 ± 1.8 (95% CI)°C, respectively, within the limits of the IEC Standard. Measurements taken with the novel IR micro-sensor exceeded these limits by 3.3 ± 0.9 (95% CI)°C. The ambiguity between our novel method and the standard techniques could have direct patient safety implications because the IR micro-sensor measurements were beyond set limits. The spatial resolution of the measurement technique is not well defined in the IEC Standard and this has to be taken into consideration when selecting which measurement technique is used to determine the maximum surface temperature.

(18)F-FDG PET-CT simulation for non-small-cell lung cancer: effect in patients already staged by PET-CT.

PURPOSE: Positron emission tomography (PET), in addition to computed tomography (CT), has an effect in target volume definition for radical radiotherapy (RT) for non-small-cell lung cancer (NSCLC). In previously PET-CT staged patients with NSCLC, we assessed the effect of using an additional planning PET-CT scan for gross tumor volume (GTV) definition. METHODS AND MATERIALS: A total of 28 patients with Stage IA-IIIB NSCLC were enrolled. All patients had undergone staging PET-CT to ensure suitability for radical RT. Of the 28 patients, 14 received induction chemotherapy. In place of a RT planning CT scan, patients underwent scanning on a PET-CT scanner. In a virtual planning study, four oncologists independently delineated the GTV on the CT scan alone and then on the PET-CT scan. Intraobserver and interobserver variability were assessed using the concordance index (CI), and the results were compared using the Wilcoxon signed ranks test. RESULTS: PET-CT improved the CI between observers when defining the GTV using the PET-CT images compared with using CT alone for matched cases (median CI, 0.57 for CT and 0.64 for PET-CT, p = .032). The median of the mean percentage of volume change from GTV(CT) to GTV(FUSED) was -5.21% for the induction chemotherapy group and 18.88% for the RT-alone group. Using the Mann-Whitney U test, this was significantly different (p = .001). CONCLUSION: PET-CT RT planning scan, in addition to a staging PET-CT scan, reduces interobserver variability in GTV definition for NSCLC. The GTV size with PET-CT compared with CT in the RT-alone group increased and was reduced in the induction chemotherapy group.

UK audit of glomerular filtration rate measurement in 2001.

OBJECTIVE: To investigate the consistency of glomerular filtration rate (GFR) calculation from plasma sampling in the UK. METHODS: Ten patients' data sets from plasma sampling measurements of GFR were distributed throughout the UK. The data included count rates from four samples taken between 2 and 4 h after injection, a diluted sample of injected dose for standardisation, the patient's height, weight, age and sex. Participants were asked to use the routine method to calculate GFR and express the results in absolute terms (i.e. in millilitres/minute) and normalized for body surface area (ml/min/1.73 m2). Supplementary data were also requested relating to workload, method used and normal range. Intercentre variability was assessed by calculating the root median square (RMedS) deviation of each GFR from the median for that data set. Centres using a particular analysis method were grouped together and the RMedS deviation of each result from the median for that group and that data set was calculated. The influence of using normalized data and number of samples was also studied. RESULTS: Seventy-nine returns were received. For the normalized data, the overall RMedS variability was 5.8 ml/min/1.73 m2. This decreased significantly to 0.6 ml/min/1.73 m2 when results were grouped by analysis method. Results were similar for non-normalized data. A small but significant decrease in error with the number of samples was observed. CONCLUSION: Considerable variability in GFR values obtained at different centres in the UK for a given set of data was observed. Nearly all this variability was due to different methods of analysis. If methodology were standardized then intercentre variability in GFR analysis could be reduced dramatically. Radionuclide techniques are confirmed as being the method of choice if an accurate value of GFR is required.

A Monte Carlo analysis technique applied to cerebral perfusion SPECT scans.

OBJECTIVE: Voxel-based techniques are used to provide objective analyses of SPECT scans. The aim of this study was to develop a voxel-based analysis technique that uses a Monte Carlo method of statistical inference and assess this analysis technique for application to cerebral perfusion SPECT scans. METHODS: Assessment of the validity of this non-parametric, Monte Carlo method of statistical inference has been performed for a range of study designs, image characteristics and analysis parameters using phantom SPECT and Gaussian images. The Monte Carlo method of statistical inference and the voxel-based analysis technique were clinically evaluated for the analysis of individual cerebral perfusion SPECT scans using control subject data. In addition, a comparison has been performed with an existing analysis package that uses a theoretical parametric method of statistical inference (statistical parametric mapping). RESULTS: The Monte Carlo method was found to provide accurate statistical inference for phantom SPECT and Gaussian images independent of degrees of freedom, acquired counts, image smoothness and voxel significance level threshold. The clinical evaluation of the analysis of individual cerebral perfusion SPECT scans demonstrated satisfactory statistical inference and characterization of perfusion deficits. CONCLUSION: An analysis method incorporating a Monte Carlo method of statistical inference has been successfully applied for the analysis of cerebral perfusion SPECT scans.

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.

UK audit of relative lung function measurement from planar radionuclide imaging.

BACKGROUND: Quantitative measurements of regional lung ventilation and perfusion are useful adjuncts to image interpretation. AIM: This study investigated the accuracy and precision of the software used to carry out such measurements in the UK. METHODS: Ten examples of perfusion distribution, representing the range of patterns expected in practice, were simulated on computer using a segmental model of the lung and real three-dimensional lung shapes obtained from magnetic resonance images. Pairs of anterior and posterior perfusion images were simulated and distributed to UK hospitals wishing to take part in the audit. Each centre returned analysis results and technical details. Forty centres provided data on the relative right:left lung perfusion. Thirteen also submitted data with each lung divided into three zones and four with each lung divided into two zones. All measurements were expressed by the percentage of total perfusion in a particular region. Errors were assessed as the root-mean-square (rms) deviation from the true value. RESULTS: Methods varied in the view used for analysis (80% geometric mean, 20% posterior) and the use of background subtraction (71% not used, 29% used). The rms error for percentage right assessment was 1.5 percentage points. This increased on two- and three-zone analysis to 3.8 and 4.3 percentage points, respectively. Differences in technique made little difference to whole-lung relative perfusion errors, but were important in zonal analysis. CONCLUSIONS: Quantification of whole-lung relative function is accurate and reproducible. Zonal values are determined less accurately, but still provide a useful guide to the distribution of function.

Audit of nuclear medicine scientific and technical standards.

The British Nuclear Medicine Society has developed a process for the service-specific organizational audit of nuclear medicine departments. This process identified the need for a scheme suitable for the audit of the scientific and technical standards of a department providing such a service. This document has evolved following audit visits of a number of UK departments. It is intended to be used as a written document to facilitate the audit procedure and may be used for both external and self-audit purposes. Scientific and technical standards have been derived from a number of sources, including regulatory documents, notes for guidance and peer-reviewed publications. The audit scheme is presented as a series of questions with responses graded according to legal and safety obligations (A), good practice (B) and desirable aspects of service delivery (C). This document should be regarded as part of an audit framework and should be kept under review as the process evolves to meet the future demands of this high-technology-based clinical service.

Value of sequential monitoring of left ventricular ejection fraction in the management of thalassemia major.

Regular monitoring of left ventricular ejection fraction (LVEF) for thalassemia major is widely practiced, but its informativeness for iron chelation treatment is unclear. Eighty-one patients with thalassemia major but no history of cardiac disease underwent quantitative annual LVEF monitoring by radionuclide ventriculography for a median of 6.0 years (interquartile range, 2-12 years). Intraobserver and interobserver reproducibility for LVEF determination were both less than 3%. LVEF values before and after transfusion did not differ, and exercise stress testing did not reliably expose underlying cardiomyopathy. An absolute LVEF of less than 45% or a decrease of more than 10 percentage units was significantly associated with subsequent development of symptomatic cardiac disease (P <.001) and death (P =.001), with a median interval between the first abnormal LVEF findings and the development of symptomatic heart disease of 3.5 years, allowing time for intervention. In 34 patients in whom LVEF was less than 45% or decreased by more than 10 percentage units, intensified chelation therapy was recommended (21 with subcutaneous and 13 with intravenous deferoxamine). All 27 patients who complied with intensification survived, whereas the 7 who did not comply died (P <.0001). The Kaplan-Meier estimate of survival beyond 40 years of age for all 81 patients is 83%. Sequential quantitative monitoring of LVEF is valuable for assessing cardiac risk and for identifying patients with thalassemia major who require intensified chelation therapy.

A comparison of three radionuclide myocardial perfusion tracers in clinical practice: the ROBUST study.

UNLABELLED: There are no large studies available to guide the selection of thallium (Tl), methoxyisobutylisonitrile (MIBI) or tetrofosmin (Tf) for myocardial perfusion imaging. Our objective was to compare the technical and clinical performance of the three in routine clinical practice. We randomised 2,560 patients to receive Tl, MIBI or Tf. A 1-day stress/rest protocol was used for MIBI and Tf. Tracer uptake was scored using a 17-segment model, quality and artefact scores were assigned, and ratios of heart (H), liver (L), subdiaphragmatic (S) and lung activity were measured. Mean quality scores (stress/rest) were Tl 2.13/2.16, MIBI 2.18/2.39, Tf 2.18/2.42 ( P=ns stress and <0.00001 rest). For attenuation artefact, Tl>MIBI=Tf ( P<0.05) and for low-count artefact Tl>MIBI>Tf ( P<0.001). For H/S, Tl>MIBI=Tf, for H/L Tl>MIBI=Tf, and for H/lung Tl