18F-Fluorodeoxyglucose PET/CT and dynamic contrast-enhanced MRI as imaging biomarkers in malignant pleural mesothelioma.

PURPOSE: The purpose of this study was to compare the use of fluorine-18-fluorodeoxyglucose (F-FDG) PET with computed tomography (CT) and dynamic contrast-enhanced (DCE) MRI to predict prognosis and monitor treatment in malignant pleural mesothelioma. PATIENTS AND METHODS: F-FDG PET/CT and DCE-MRI studies carried out as part of the South West Area Mesothelioma Pemetrexed trial were used. F-FDG PET/CT and DCE-MRI studies were carried out before treatment, and after two cycles of chemotherapy, on patients treated with pemetrexed and cisplatin. A total of 73 patients were recruited, of whom 65 had PET/CT and DCE-MRI scans. Baseline measurements from F-FDG PET/CT (maximum standardized uptake value, metabolic tumour volume and total lesion glycolysis) and DCE-MRI (integrated area under the first 90s of the curve and washout slope) were compared with overall survival (OS) using Kaplan-Meier and Cox regression analyses, and changes in imaging measurements were compared with disease progression. RESULTS: PET/CT and DCE-MRI measurements were not correlated with each other. Maximum standardized uptake value, metabolic tumour volume and total lesion glycolysis were significantly related to OS with Cox regression analysis and Kaplan-Meir analysis, and DCE-MRI washout curve shape was significantly related to OS. DCE-MRI curve shape can be combined with F-FDG PET/CT to give additional prognostic information. Changes in measurements were not related to progression-free survival. CONCLUSIONS: F-FDG PET/CT and DCE-MRI give prognostic information in malignant pleural mesothelioma. Neither PET/CT nor DCE-MRI is useful for monitoring disease progression.

UK audit of quantitative thyroid uptake imaging.

AIM: A national audit of quantitative thyroid uptake imaging was conducted by the Nuclear Medicine Software Quality Group of the Institute of Physics and Engineering in Medicine in 2014/2015. The aims of the audit were to measure and assess the variability in thyroid uptake results across the UK and to compare local protocols with British Nuclear Medicine Society (BNMS) guidelines. PARTICIPANTS AND METHODS: Participants were invited through a combination of emails on a public mailbase and targeted invitations from regional co-ordinators. All participants were given a set of images from which to calculate quantitative measures and a spreadsheet for capturing results. The image data consisted of two sets of 10 anterior thyroid images, half of which were acquired after administration of Tc-pertechnetate and the other half after administration of I-iodide. Images of the administration syringes or thyroid phantoms were also included. RESULTS: In total, 54 participants responded to the audit. The median number of scans conducted per year was 50. A majority of centres had at least one noncompliance in comparison with BNMS guidelines. Of most concern was the widespread lack of injection-site imaging. Quantitative results showed that both intersite and intrasite variability were low for the Tc dataset. The coefficient of quartile deviation was between 0.03 and 0.13 for measurements of overall percentage uptake. Although the number of returns for the I dataset was smaller, the level of variability between participants was greater (the coefficient of quartile deviation was between 0.17 and 0.25). CONCLUSION: A UK-wide audit showed that thyroid uptake imaging is still a common test in the UK. It was found that most centres do not adhere to all aspects of the BNMS practice guidelines but that quantitative results are reasonably consistent for Tc-based scans.

UK audit of glomerular filtration rate measurement from plasma sampling in 2013.

INTRODUCTION: An audit was carried out into UK glomerular filtration rate (GFR) calculation. The results were compared with an identical 2001 audit. METHODS: Participants used their routine method to calculate GFR for 20 data sets (four plasma samples) in millilitres per minute and also the GFR normalized for body surface area. Some unsound data sets were included to analyse the applied quality control (QC) methods. Variability between centres was assessed for each data set, compared with the national median and a reference value calculated using the method recommended in the British Nuclear Medicine Society guidelines. The influence of the number of samples on variability was studied. Supplementary data were requested on workload and methodology. RESULTS: The 59 returns showed widespread standardization. The applied early exponential clearance correction was the main contributor to the observed variability. These corrections were applied by 97% of centres (50% - 2001) with 80% using the recommended averaged Brochner-Mortenson correction. Approximately 75% applied the recommended Haycock body surface area formula for adults (78% for children). The effect of the number of samples used was not significant. There was wide variability in the applied QC techniques, especially in terms of the use of the volume of distribution. CONCLUSION: The widespread adoption of the guidelines has harmonized national GFR calculation compared with the previous audit. Further standardization could further reduce variability. This audit has highlighted the need to address the national standardization of QC methods. Radionuclide techniques are confirmed as the preferred method for GFR measurement when an unequivocal result is required.

An audit of half-count myocardial perfusion imaging using resolution recovery software.

INTRODUCTION: The Nuclear Medicine Software Quality Group of the Institute of Physics and Engineering in Medicine has conducted a multicentre, multivendor audit to evaluate the use of resolution recovery software from several manufacturers when applied to myocardial perfusion data with half the normal counts acquired under a variety of clinical protocols in a range of departments. The objective was to determine whether centres could obtain clinical results with half-count data processed with resolution recovery software that were equivalent to those obtained using their normal protocols. MATERIALS AND METHODS: Sixteen centres selected 50 routine myocardial perfusion studies each, from which the Nuclear Medicine Software Quality Group generated simulated half-count studies using Poisson resampling. These half-count studies were reconstructed using resolution recovery and the clinical reports compared with the original reports from the full-count data. A total of 769 patient studies were processed and compared. RESULTS: Eight centres found only a small number of clinically relevant discrepancies between the two reports, whereas eight had an unacceptably high number of discrepancies. There were no significant differences in acquisition parameters between the two groups, although centres finding a high number of discrepancies were more likely to perform both rest and stress scans on normal studies. CONCLUSION: Half of the participating centres could potentially make use of resolution recovery to reduce the administered activity for myocardial perfusion scans without changing their routine acquisition protocols. The other half could consider adjusting the reconstruction parameters used with their resolution recovery software if they wish to use reduced activity successfully.

UK audit of quantification of left-ventricular function using gated myocardial perfusion imaging.

PURPOSE: The aim of the study was to evaluate UK-wide interinstitutional reproducibility of left-ventricular functional parameters, end-systolic volume, end-diastolic volume and ejection fraction, obtained from gated myocardial perfusion imaging (GMPI) studies using technetium-99m-labelled radiopharmaceuticals. The study was carried out by the UK Institute of Physics and Engineering in Medicine Nuclear Medicine Software Quality Group. MATERIALS AND METHODS: Ten anonymized clinical GMPI studies, five with normal perfusion and five with perfusion defects, were made available in DICOM and proprietary formats for download and through manufacturers' representatives. Two of the studies were duplicated in order to assess intraoperator repeatability, giving a total of 12 studies. Studies were made available in 8 and 16 frames/cycle. RESULTS: A total of 58 institutions across England, Scotland, Wales and Northern Ireland participated in this study using six different computer packages. Studies were processed at centres using their normal clinical computers and software. The overall mean±SD ejection fraction for all centres was 58.5±3%; the mean end-diastolic volume was 114±12 ml and the mean end-systolic volume was 54±6 ml. The results were affected by the number of frames per cycle and by the postprocessing computer package, but not by the reconstruction filter in the filtered back-projection. CONCLUSION: Calculation of functional parameters from GMPI using technetium-99m-labelled radiopharmaceuticals is reliable and shows limited variability across the UK.

An audit of manufacturers' implementation of reconstruction filters in single-photon emission computed tomography.

AIM: The Nuclear Medicine Software Quality Group of the Institute of Physics and Engineering in Medicine has conducted an audit to compare the ways in which different manufacturers implement the filters used in single-photon emission computed tomography. The aim of the audit was to identify differences between manufacturers' implementations of the same filter and to find means for converting parameters between systems. METHODS: Computer-generated data representing projection images of an ideal test object were processed using seven different commercial nuclear medicine systems. Images were reconstructed using filtered back projection and a Butter worth filter with three different cutoff frequencies and three different orders. RESULTS: The audit found large variations between the frequency-response curves of what were ostensibly the same filters on different systems. The differences were greater than could be explained simply by different Butter worth formulae. Measured cutoff frequencies varied between 40 and 180% of that expected. There was also occasional confusion with respect to frequency units. CONCLUSION: The audit concluded that the practical implementation of filtering, such as the size of the kernel, has a profound effect on the results, producing large differences between systems. Nevertheless, this work shows how users can quantify the frequency response of their own systems so that it will be possible to compare two systems in order to find filter parameters on each that produce equivalent results. These findings will also make it easier for users to replicate filters similar to other published results, even if they are using a different computer system.

Investigation of normal ranges for left ventricular ejection fraction in cardiac gated blood pool imaging studies using different processing workstations.

BACKGROUND: An investigation has been undertaken to calculate normal ranges for left ventricular ejection fraction (LVEF) measured by the gated blood pool (GBP) technique. A common set of normal studies was used at 11 hospitals within the south of England to assess the variability of results and normal ranges. METHODS: Normal studies were identified by retrospective review of patients who had undergone a GBP study and echocardiogram at the Royal United Hospital, Bath. Patients who had left ventricular function qualitatively identified as normal on echocardiogram and normal wall motion for the GBP were included. In total, 64 datasets were found to match the criteria. All the studies were made anonymous prior to being distributed to the participating hospitals. The upper and lower limits for normal ejection fraction were defined for each system using the 95% confidence limits around the mean value, before and after normalizing the results to remove systematic differences between the processing systems. RESULTS: The lower cut-off for normal function varied between 40 and 51%. Analysis of the individual operator results gave an inter-operator standard deviation of 4.2 and an intra-operator standard deviation of 2.7. CONCLUSIONS: It is recommended that all studies should be processed at least twice and an average taken to minimise these sources of uncertainty. If there is a significant difference the study should be reprocessed. Due to random differences between results from different systems it is suggested that an equivocal range be used between clearly normal and abnormal function.

Outdoor production of Phaeodactylum tricornutum biomass in a helical reactor.

The production of microalga Phaeodactylum tricornutum in an outdoor helical reactor was analysed. The influence of temperature, solar irradiance and air flow rate on the yield of the culture was evaluated. Biomass productivities up to 1.5 g l(-1) per day and photosynthetic efficiency up to 14% were obtained by maintaining the cultures below 30 degrees C, dissolved oxygen levels less than 400% Sat. (with respect to air saturated culture) and controlling the cell density in order to achieve an average irradiance within the culture below 250 microE m(-2) s(-1). Under these conditions, the fluorescence parameter, Fv/Fm, which reflects the maximal efficiency of PSII photochemistry, remained roughly 0.6-0.7 and growth rates up to 0.050 h(-1) were achieved. The average irradiance and the light/dark cycle frequency, were the variables determining the behaviour of the cultures. A hyperbolic relationship between growth rate and biomass productivity with the average irradiance was observed, whereas both biomass productivity and photosynthetic efficiency linearly increased with the light/dark cycle frequencies. Optimum design and operational conditions which maximise the production of P. tricornutum biomass in outdoor helical reactors were determined.

Outdoor helical tubular photobioreactors for microalgal production: modeling of fluid-dynamics and mass transfer and assessment of biomass productivity.

The production of the microalga Phaeodactylum tricornutum in an outdoor helical reactor was analyzed. First, fluid dynamics, mass-transfer capability, and mixing of the reactor was evaluated at different superficial gas velocities. Performance of the reactor was controlled by power input per culture volume. A maximum liquid velocity of 0.32 m s(-1) and mass transfer coefficient of 0.006 s(-1) were measured at 3200 W m(-3). A model of the influence of superficial gas velocity on the following reactor parameters was proposed: gas hold-up, induced liquid velocity, and mass transfer coefficient, with the accuracy of the model being demonstrated. Second, the influence of superficial gas velocity on the yield of the culture was evaluated in discontinuous and continuous cultures. Mean daily values of culture parameters, including dissolved oxygen, biomass concentration, chlorophyll fluorescence (F(v)/F(m) ratio), growth rate, biomass productivity, and photosynthetic efficiency, were determined. Different growth curves were measured when the superficial gas velocity was modified-the higher the superficial gas velocity, the higher the yield of the system. In continuous mode, biomass productivity increased by 35%, from 1.02 to 1.38 g L(-1) d(-1), when the superficial gas velocity increased from 0.27 to 0.41 m s(-1). Maximal growth rates of 0.068 h(-1), biomass productivities up to 1.4 g L(-1) d(-1), and photosynthetic efficiency of up to 15% were obtained at the higher superficial gas velocity of 0.41 m s(-1). The fluorescence parameter, F(v)/F(m), which reflects the maximal efficiency of PSII photochemistry, showed that the cultures were stressed at average irradiances within the culture higher than 280 microE m(-2) s(-1) at every superficial gas velocity. For nonstressed cultures, the yield of the system was a function of average irradiance inside the culture, with the superficial gas velocity determining this relationship. When superficial gas velocity was increased, higher growth rates, biomass productivities, and photosynthetic efficiencies were obtained for similar average irradiance values. The higher the superficial gas velocity, the higher the liquid velocity, with this increase enhancing the movement of the cells inside the culture. In this way the efficiency of the cells increased and higher biomass concentrations and productivities were reached for the same solar irradiance.