A multicentre and multi-national evaluation of the accuracy of quantitative Lu-177 SPECT/CT imaging performed within the MRTDosimetry project

Purpose Patient-specific dosimetry is required to ensure the safety of molecular radiotherapy and to predict response. Dosimetry involves several steps, the first of which is the determination of the activity of the radiopharmaceutical taken up by an organ/lesion over time. As uncertainties propagate along each of the subsequent steps (integration of the time–activity curve, absorbed dose calculation), establishing a reliable activity quantification is essential. The MRTDosimetry project was a European initiative to bring together expertise in metrology and nuclear medicine research, with one main goal of standardizing quantitative 177Lu SPECT/CT imaging based on a calibration protocol developed and tested in a multicentre inter-comparison. This study presents the setup and results of this comparison exercise. Methods The inter-comparison included nine SPECT/CT systems. Each site performed a set of three measurements with the same setup (system, acquisition and reconstruction): (1) Determination of an image calibration for conversion from counts to activity concentration (large cylinder phantom), (2) determination of recovery coefficients for partial volume correction (IEC NEMA PET body phantom with sphere inserts), (3) validation of the established quantitative imaging setup using a 3D printed two-organ phantom (ICRP110-based kidney and spleen). In contrast to previous efforts, traceability of the activity measurement was required for each participant, and all participants were asked to calculate uncertainties for their SPECT-based activities. Results Similar combinations of imaging system and reconstruction lead to similar image calibration factors. The activity ratio results of the anthropomorphic phantom validation demonstrate significant harmonization of quantitative imaging performance between the sites with all sites falling within one standard deviation of the mean values for all inserts. Activity recovery was underestimated for total kidney, spleen, and kidney cortex, while it was overestimated for the medulla. Conclusion This international comparison exercise demonstrates that harmonization of quantitative SPECT/CT is feasible when following very specific instructions of a dedicated calibration protocol, as developed within the MRTDosimetry project. While quantitative imaging performance demonstrates significant harmonization, an over- and underestimation of the activity recovery highlights the limitations of any partial volume correction in the presence of spill-in and spill-out between two adjacent volumes of interests.

The Significance of Knowledge, Instructions, Habits and Denture Hygiene Practice in Relation to the Maintenance of Denture Hygiene at Hospital USM’s Dental Clinic

Good denture hygiene is crucial for the prevention of various periodontal diseases, dental caries and dental stomatitis, which can give rise to a negative impact on the general health of denture users. A comparison exercise was conducted, to determine the effectiveness of information on denture care, provided by different groups of dental personnel. A self-administered and structured questionnaire was distributed to patients who attended Hospital USM’s dental clinics, from 2014 to 2019 based on the attendance register of the clinic. The denture hygiene status of 100 participants was assessed during the interview session. The results derived through the questionnaire revealed that 100% of the respondents, who received both verbal and written instructions, practiced good dental hygiene. It was observed that the most effective instructions received by the respondents were delivered by the dental specialists. Respondents, who clean their dentures with denture cleaning tablets, soap, or denture cleaning paste, were observed to possess better denture hygiene than those who do not. Also, respondents who visit their dentists once every six months for routine dental examinations boasted a higher percentage of good denture hygiene (81.8%). A positive association was perceived, between knowledge and the status of denture hygiene.

Atmospheric Correction Inter-comparison eXercise: the second implementation

<p>The atmospheric correction inter-comparison exercise (ACIX) is an international initiative to benchmark various state-of-the-art atmospheric correction (AC) processors. The first inter-comparison exercise initiated in 2016 with the collaboration of European Space Agency (ESA) and National Aeronautics and Space Administration (NASA) in the frame of the CEOS WGCV (Committee on Earth Observation Satellites, Working Group on Calibration & Validation). The evolution of the participating processors and the increasing interest of AC community to repeat and improve such experiment stimulated the continuation of ACIX and its second implementation (ACIX-II). In particular, 12 AC developer teams from Europe and USA participated in ACIX-II over land sites. In this presentation the benchmarking protocol, i.e. test sites, input data, inter-comparison metrics, etc. will be briefly described and some representative results of ACIX-II will be presented. The inter-comparison outputs varied depending on the sensors, products and sites, demonstrating the strengths and weaknesses of the corresponding processors. In continuation of ACIX-I achievements, the outcomes of the second one are expected to provide an enhanced standardised approach to inter-compare AC processing products, i.e. Aerosol Optical Thickness (AOT), Water Vapour (WV) and Surface Reflectance (SR), and quantitively assessed their quality when in situ measurements are available.</p>

Spectral Emissivity (SE) Measurement Uncertainties across 2.5–14 μm Derived from a Round-Robin Study Made across International Laboratories

Information on spectral emissivity (SE) is vital when retrieving and evaluating land surface temperature (LST) estimates from remotely sensed observations. SE measurements often come from spectral libraries based upon laboratory spectroscopic measurements, with uncertainties typically derived from repeated measurements. To go further, we organised a “round-robin” inter-comparison exercise involving SE measurements of three samples collected at seven different international laboratories. The samples were distilled water, which has a uniformly high spectral emissivity, and two artificial samples (aluminium and gold sheets laminated in polyethylene), with variable emissivities and largely specular and Lambertian characteristics. Large differences were observed between some measurements, with standard deviations over 2.5–14 μm of 0.092, 0.054 and 0.028 emissivity units (15.98%, 7.56% and 2.92%) for the laminated aluminium sheet, laminated gold sheet and distilled water respectively. Wavelength shifts of up to 0.09 μm were evident between spectra from different laboratories for the specular sample, attributed to system design interacting with the angular behaviour of emissivity. We quantified the impact of these SE differences on satellite LST estimation and found that emissivity differences resulted in LSTs differing by at least 3.5 K for each artificial sample and by more than 2.5 K for the distilled water. Our findings suggest that variations between SE measurements derived via laboratory setups may be larger than previously assumed and provide a greater contribution to LST uncertainty than thought. The study highlights the need for the infrared spectroscopy community to work towards standardized and interlaboratory comparable results.