We present a new rodent SPECT system (U-SPECT-II) that enables molecular imaging of murine organs down to resolutions of less than half a millimeter and high-resolution total-body imaging.
The ...U-SPECT-II is based on a triangular stationary detector set-up, an XYZ stage that moves the animal during scanning, and interchangeable cylindric collimators (each containing 75 pinhole apertures) for both mouse and rat imaging. A novel graphical user interface incorporating preselection of the field of view with the aid of optical images of the animal focuses the pinholes to the area of interest, thereby maximizing sensitivity for the task at hand. Images are obtained from list-mode data using statistical reconstruction that takes system blurring into account to increase resolution.
For (99m)Tc, resolutions determined with capillary phantoms were smaller than 0.35 and 0.45 mm using the mouse collimator with 0.35- and 0.6-mm pinholes, respectively, and less than 0.8 mm using the rat collimator with 1.0-mm pinholes. Peak geometric sensitivity is 0.07% and 0.18% for the mouse collimator with 0.35- and 0.6-mm pinholes, respectively, and 0.09% for the rat collimator. Resolution with (111)In, compared with that with (99m)Tc, was barely degraded, and resolution with (125)I was degraded by about 10%, with some additional distortion. In vivo, kidney, tumor, and bone images illustrated that U-SPECT-II could be used for novel applications in the study of dynamic biologic systems and radiopharmaceuticals at the suborgan level.
Images and movies obtained with U-SPECT-II provide high-resolution radiomolecule visualization in rodents. Discrimination of molecule concentrations between adjacent volumes of about 0.04 microL in mice and 0.5 microL in rats with U-SPECT-II is readily possible.
The European Society of Breast Cancer Specialists (EUSOMA) has fostered a voluntary certification process for breast centres to establish minimum standards and ensure specialist multidisciplinary ...care. Prospectively collected anonymous information on primary breast cancer cases diagnosed and treated in the units is transferred annually to a central EUSOMA data warehouse for continuous monitoring of quality indicators (QIs) to improve quality of care. Units have to comply with the EUSOMA Breast Centre guidelines and are audited by peers. The database was started in 2006 and includes over 110,000 cancers from breast centres located in Germany, Switzerland, Belgium, Austria, The Netherlands, Spain, Portugal and Italy. The aim of the present study is assessing time trends of QIs in EUSOMA-certified breast centres over the decade 2006–2015.
Previously defined QIs were calculated for 22 EUSOMA-certified breast centres (46122 patients) during 2006–2015.
On the average of all units, the minimum standard of care was achieved in 8 of 13 main EUSOMA QIs in 2006 and in all in 2015. All QIs, except removal of at least 10 lymph nodes at axillary clearance and oestrogen receptor–negative tumours (T > 1 cm or N+) receiving adjuvant chemotherapy, improved significantly in this period. The desirable target was reached for two QIs in 2006 and for 7 of 13 QIs in 2015.
The EUSOMA model of audit and monitoring QIs functions well in different European health systems and results in better performance of QIs over the last decade. QIs should be evaluated and adapted on a regular basis, as guidelines change over time.
•The time trends of quality indicators in EUSOMA-certified breast centres over the decade 2006–2015 are evaluated.•The EUSOMA model of audit and monitoring QIs functions well in different European health systems.•Audit and measuring quality indicators result in better performance.
Abstract Aim of the study The European Society of Breast Cancer Specialists (EUSOMA) has fostered a voluntary certification process for breast units to establish minimum standards and ensure ...specialist multidisciplinary care. In the present study we assess the impact of EUSOMA certification for all breast units for which sufficient information was available before and after certification. Materials and methods For 22 EUSOMA certified breast units data of 30,444 patients could be extracted from the EUSOMA database on the evolution of QI's before and after certification. Results On the average of all units, the minimum standard of care was achieved for 12/13 QI's before and after EUSOMA certification (not met for DCIS receiving just one operation). There was a significant improvement of 5 QI's after certification. The proportion of patients with invasive cancer undergoing an axillary clearance containing >9 lymph nodes (91.5% vs 89.4%, p 0.003) and patients with invasive cancer having just 1 operation (83.1% vs 80.4%, p < 0.001) dropped, but remained above the minimum standard. The targeted standard of breast care was reached for the same 4/13 QI's before and after EUSOMA certification. Conclusion Although the absolute effect of EUSOMA certification was modest it further increases standards of care and should be regarded as part of a process aiming for excellence. Dedicated units already provide a high level of care before certification, but continuous monitoring and audit remains of paramount importance as complete adherence to guidelines is difficult to achieve.
Ho-166 is a combined beta-gamma emitter of which the betas can be used therapeutically. From the 81 keV gammas of Ho-166, SPECT images can be obtained, which give opportunities to guide Ho-166 ...therapy. Accurate reconstruction of Ho-166 images is currently hampered by photopeak-scatter in the patient, down-scatter in the detector, collimator and patient caused by the 1.4 MeV photons and by bremsstrahlung. We developed and validated a method for quantitative SPECT of Ho-166 that involves correction for both types of scatter plus non-uniform attenuation correction using attenuation maps. Photopeak-scatter (S) is compensated for by a rapid 3D Monte Carlo (MC) method that is incorporated in ordered subset (OS) reconstruction of the emission data, together with simultaneous correction for attenuation (A) and detector response (D); this method is referred to as OS-ADS. Additionally, for correction of down-scatter, we use a 14 keV wide energy window centred at 118 keV (OS-ADSS). Due to a limited number of available energy windows, the same 118 keV energy window was used for down-scatter correction of the simultaneously acquired Gd-153 transmission data. Validations were performed using physical phantom experiments carried out on a dual-head SPECT system; Gd-153 transmission line sources were used for acquiring attenuation maps. For quantitative comparison of OS-ADS and OS-ADSS, bottles filled with Ho-166 were placed in both a cylindrical phantom and an anthropomorphic thorax phantom. Both OS-ADS and OS-ADSS were compared with an ordered subset reconstruction without any scatter correction (OS-AD). Underestimations of about 20% in the attenuation map were reduced to a few per cent after down-scatter correction. The average deviation from the true activity contained in the bottles was +72% with OS-AD. Using OS-ADS, this average overestimation was reduced to +28% and with OS-ADSS the deviation was further reduced to 16%. With OS-AD and OS-ADS, these numbers were more sensitive to the choice of volumes of interest than with OS-ADSS. For the reconstructed activity distributions, erroneous background activity found with OS-AD was reduced by a factor of approximately 2 by applying OS-ADS and reduced by a factor of approximately 4 by applying OS-ADSS. The combined attenuation, photopeak-scatter and down-scatter correction framework proposed here greatly enhanced the quantitative accuracy of Ho-166 imaging, which is of the uppermost importance for image-guided therapies. It is expected that the method, with adapted window settings, also can be applied to other isotopes with high energy peaks that contaminate the photopeak data, such as I-131 or In-111.
Purpose
Thallous (
201
Tl) chloride is a single-photon emission computed tomography (SPECT) tracer mainly used for assessing perfusion and viability of myocardial tissue.
201
Tl emits X-rays around ...72 keV and gammas at 167 keV, and has a half-life of 73 h. Regulations allow an intrinsic contamination up to 3-5%, which is mainly caused by
200
Tl (368 keV; 26 h) and by
202
Tl (439 keV; 12.2 days). Contra-intuitive to the low-level percentages in which these contaminants are present, their impact may be significant because of much higher gamma camera sensitivity for these high-energy photon emissions. Therefore, we investigate the effects of the contaminants in terms of detected fractions of photons in projections and contrast degradation in reconstructed images.
Methods
Acquisitions of a digital thorax phantom filled with thallous (
201
Tl) chloride were simulated with a validated Monte Carlo tool, thereby, modelling 1% of contamination by
200
Tl and
202
Tl each. In addition, measurements of a thorax phantom on a dual-headed gamma camera were performed. The product used was contaminated by 0.17% of
200
Tl and 0.24% of
202
Tl at activity reference time (ART). This ART is specified by the manufacturer, thereby, accounting for the difference in half-lives of
201
Tl and its contaminants. These measurements were repeated at different dates associated with various contamination levels.
Results
Simulations showed that, with 1% of
200
Tl and
202
Tl, the total contamination in the 72 keV window can rise up to one out of three detected photons. For the 167keV window, the contamination is even more pronounced: more than four out of five detections in this photopeak window originate from contaminants. Measurements indicate that cold lesion contrast in myocardial perfusion SPECT imaging is at maximum close to ART. In addition to a higher noise level, relative contrast decreases 15% 2 days early to ART, which is explained by an increase in
200
Tl contamination. After ART, contrast decreased by 16% when the
202
Tl contamination increased to the maximal allowed limit.
Conclusions
Contra-intuitive to the low-level percentages in which they are typically present, penetration and downscatter of high-energy photons from
200
Tl and
202
Tl significantly contribute to thallous (
201
Tl) chloride images, thereby, reducing contrast and adding noise. These findings may prompt for improved production methods, for updated policies with regard to timing of usage, and they also render the usefulness of adding the high photopeak window (167 keV) questionable. A window-based correction method for this contamination is advisable.
(201)Tl-Chloride ((201)Tl) is a myocardial perfusion SPECT agent with excellent biochemical properties commonly used for assessing tissue viability. However, cardiac (201)Tl SPECT images are severely ...degraded by photons scattered in the thorax. Accurate correction for this scatter is complicated by the nonuniform density and varied sizes of thoraxes, by the additional attenuation and scatter caused by female patients' breasts, and by the energy spectrum of (201)Tl. Monte Carlo simulation is a general and accurate method well suited to modeling this scatter.
Statistical reconstruction that includes Monte Carlo modeling of scatter was compared with statistical reconstruction algorithms not corrected for scatter. In the ADS method, corrections for attenuation, detector response, and scatter (Monte Carlo-based) were implemented simultaneously via the dual-matrix ordered-subset expectation maximization algorithm with a Monte Carlo simulator as part of the forward projector. The ADS method was compared with the A method (ordered-subset expectation maximization with attenuation correction) and with the AD method (a method like the A method but with detector response modeling added). A dual-head SPECT system equipped with two (153)Gd scanning line sources was used for simultaneously acquiring transmission and emission data. Four clinically realistic phantom configurations (a large thorax and a small thorax, each with and without breasts) with a cardiac insert containing 2 cold defects were used to evaluate the proposed reconstruction algorithms. We compared the performance of the different algorithms in terms of noise properties, contrast-to-noise ratios, the contrast separability of perfusion defects, uniformity, and robustness to anatomic variations.
The ADS method provided images with clearly better visual defect contrast than did the other methods. The contrasts achieved with the ADS method were 10%-24% higher than those achieved with the AD method and 11%-37% higher than those achieved with the A method. For a typical contrast level, the ADS method exhibited noise levels around 27% lower than the AD method and 34% lower than the A method. Compared with the other 2 algorithms, the ADS reconstructions were less sensitive to anatomic variations and had better image uniformity in the homogeneously perfused myocardium. Finally, we found that the improvements that can be achieved with Monte Carlo-based scatter correction are stronger for (201)Tl than for (99m)Tc imaging.
Our results indicate that Monte Carlo-based scatter correction is suitable for (201)Tl cardiac imaging and that such correction simultaneously improves several image-quality metrics.
Purpose: Thallous ( super(201)Tl) chloride is a single-photon emission computed tomography (SPECT) tracer mainly used for assessing perfusion and viability of myocardial tissue. super(201)Tl emits ...X-rays around 72 keV and gammas at 167 keV, and has a half-life of 73 h. Regulations allow an intrinsic contamination up to 3-5%, which is mainly caused by super(200)Tl (368 keV; 26 h) and by super(202)Tl (439 keV; 12.2 days). Contra-intuitive to the low-level percentages in which these contaminants are present, their impact may be significant because of much higher gamma camera sensitivity for these high-energy photon emissions. Therefore, we investigate the effects of the contaminants in terms of detected fractions of photons in projections and contrast degradation in reconstructed images. Methods: Acquisitions of a digital thorax phantom filled with thallous ( super(201)Tl) chloride were simulated with a validated Monte Carlo tool, thereby, modelling 1% of contamination by super(200)Tl and super(202)Tl each. In addition, measurements of a thorax phantom on a dual-headed gamma camera were performed. The product used was contaminated by 0.17% of super(200)Tl and 0.24% of super(202)Tl at activity reference time (ART). This ART is specified by the manufacturer, thereby, accounting for the difference in half-lives of super(201)Tl and its contaminants. These measurements were repeated at different dates associated with various contamination levels. Results: Simulations showed that, with 1% of super(200)Tl and super(202)Tl, the total contamination in the 72 keV window can rise up to one out of three detected photons. For the 167keV window, the contamination is even more pronounced: more than four out of five detections in this photopeak window originate from contaminants. Measurements indicate that cold lesion contrast in myocardial perfusion SPECT imaging is at maximum close to ART. In addition to a higher noise level, relative contrast decreases 15% 2 days early to ART, which is explained by an increase in super(200)Tl contamination. After ART, contrast decreased by 16% when the super(202)Tl contamination increased to the maximal allowed limit. Conclusions: Contra-intuitive to the low-level percentages in which they are typically present, penetration and downscatter of high-energy photons from super(200)Tl and super(202)Tl significantly contribute to thallous ( super(201)Tl) chloride images, thereby, reducing contrast and adding noise. These findings may prompt for improved production methods, for updated policies with regard to timing of usage, and they also render the usefulness of adding the high photopeak window (167 keV) questionable. A window-based correction method for this contamination is advisable.
Cardiac SPECT images are degraded by photons scattered in the thorax. Accurate correction for scatter is complicated by the nonuniform density and varied sizes of thoraxes and by the additional ...attenuation and scatter caused by female patients' breasts. Monte Carlo simulation is a general and accurate method for detailed modeling of scatter. Hence, for 99mTc we compared statistical reconstruction based on Monte Carlo modeling of scatter with statistical reconstruction that incorporates the more commonly used triple-energy-window scatter correction. Both of these scatter correction methods were used in conjunction with attenuation correction and resolution recovery.
Simultaneous attenuation, detector response, and Monte Carlo-based scatter correction were implemented via the dual-matrix ordered-subset expectation maximization algorithm with a Monte Carlo simulator as part of the forward projector (ADS-MC). ADS-MC was compared to (i) ordered-subset expectation maximization with attenuation correction and with detector response modeling (AD); (ii) like (i) but with scatter correction added using the triple-energy-window method (ADS-TEW). A dual-detector SPECT system equipped with 2 153Gd scanning line sources was used for acquiring 99mTc emission data and attenuation maps. Four clinically realistic phantom configurations (a large thorax and a small thorax, each with and without breasts) with a cardiac insert containing 2 cold defects were used to evaluate the proposed reconstruction algorithms. In these phantom configurations, we compared the performance of the algorithms in terms of noise properties, contrast-to-noise ratios, contrast separability of cold defects, and robustness to anatomic variation.
Noise was found to be approximately 14% lower in the ADS-MC images than in the ADS-TEW and AD images. Typically, the contrast obtained with the ADS-MC algorithm was 10%-20% higher than that obtained with the other 2 methods. Furthermore, compared with the other 2 algorithms, the ADS-MC method was less sensitive to anatomic variations.
Our results indicate that the imaging performance of 99mTc SPECT can be improved more by Monte Carlo-based scatter correction than by window-based scatter correction.
Biochar addition to soils has been proposed as a means to increase soil fertility and carbon sequestration. However, its effect on soil nitrogen (N) cycling and N availability is poorly understood. ...To gain better insight into the short-term effects of biochar on gross N transformation processes, a 15N tracing experiment in combination with numerical data analysis was conducted. An arable loamy sand soil was used and mixed with two silage maize biochars, produced at 350 °C and 550 °C. The results showed accelerated soil N cycling following biochar addition, with increased gross N mineralization (185–221%), nitrification (10–69%) and ammonium (NH4+) consumption rates (333–508%). Moreover, transfer of N from a recalcitrant soil organic N (Nrec) pool to a more labile soil organic N (Nlab) pool was observed. In the control treatment, 8% of the NH4+ mineralized from Nlab was immobilized to the Nrec pool. In contrast, 79% and 55% of the NH4+ mineralized from Nrec were immobilized to the Nlab pool in the treatment with biochar-350 °C and biochar-550 °C, respectively. NH4+–N was adsorbed quickly to biochar at the start of the experiment, thereby buffering plant-available N. In conclusion, these types of biochar accelerated soil N transformations in the short term, thereby increasing soil N bio-availability, through a combined effect of mineralization of the recalcitrant soil organic N pool and subsequent NH4+ immobilization in a labile soil organic N pool.
► Upon maize biochar addition NH4+–nitrogen (N) was quickly adsorbed. ► Biochar accelerated various soil N transformation processes in the short term. ► Biochar transferred soil N from a recalcitrant to a labile pool in the short term. ► Biochar addition to soil increased gross nitrification rates in the short term.
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