KH2PO4 Solution Research Articles

Phosphorus accumulation in soil after successive applications of swine manure: a long-term study in Brazil

Successive applications of swine manure (SM) in agriculture may contribute to environmental contamination by excess of phosphorus (P). In this study, we analyzed the dynamics of P fractions in soil cultivated with Ilex paraguariensis, following successive applications of SM over a long period (> 40 years) in southern Brazil. Soil samples in the 0–5, 5–10 and 20–40 cm layers were collected in areas subjected to 35 (A35) and 45 (A45) years of SM application and an area with no anthropogenic intervention (M). The content of organic and inorganic P in the soil samples was quantified by sequential extraction with NaHCO3 0.5 mol L−1 (labile), H2SO4 (moderately labile), and NaOH 0.5 mol L−1 (recalcitrant). The potential of P adsorption was assessed using the solution of KH2PO4 which remained in contact with the soil for a night. Data were compared by Tukey test at 5% probability. The results showed that 35 and 45 years of successive SM application did not increase total P content in soil. In contrast, an increase in inorganic form of P was observed. In comparison to the forest area, SM application for 45 years increased the content of the labile inorganic P fraction by 168%, 162% and 290% in the 0–5, 5–10 and 20–40 cm soil layers, respectively. The accumulation of this fraction promoted the reduction of P adsorption in soil by 99%, 180% and 175% in the 0–5, 5–10 and 20–40 cm soil layers, respectively, increasing the risk of contamination of groundwater by P excess.

Evaluating of soil sulphur forms changes in long-term field experiments of Látókép

The aim of this work was to evaluate the changes of different sulphur forms (soluble, adsorbed) in chernozem soil in a long-term field experiment supplied with increasing doses of NPK fertilizers for a long time. In addition, other objective of this study included the examination of the applicability of recommended extractants of the different sulphate fraction in Hungarian soils. A long-term field experiment was established at the Research Station of Látókép of the University of Debrecen in 1984. In addition to control, two levels of NPK fertilizer doses have been used with irrigated and non-irrigated variants. Winter wheat and corn were cropped in a crop rotation on plots. Soil samples were collected in three different development stages of winter wheat, at the stage of stem elongation (April), flowering (May) and ripening (June of 2018) from the topsoil (0–20 cm) of experiment plots. Water-soluble inorganic sulphate was extracted with 0.01M CaCl2 solutions. The soluble plus adsorbed sulphate was extracted with 0.016M KH2PO4 solution. Sulphate was measured by turbidimetric method. 0.01M CaCl2-SO42— ranged between 0.293–1.896 mg kg-1 and the 0.016 M KH2PO4-SO42- varied between 5.087–10.261 mg kg-1. The values of KH2PO4 SO42- was higher than that of CaCl2-SO42-, because KH2PO4 extracted the adsorbed and soluble fractions of sulphate, while CaCl2 extracted the soluble sulphate fraction. The amount of absorbed sulphate was calculated by the differences of KH2PO4- SO4 and CaCl2-SO4. The KH2PO4 characterizes mainly the adsorbed sulphate fraction much more than the water-soluble fraction. KCl is the most widely used extractant for the determination of plant available sulphate content of soil in Hungary; therefore, KCl-SO42- fraction also was determined. The KCl-SO42- ranged between 0.328–2.152 mg kg-1. The CaCl2-SO42- and KCl-SO42- fractions were compared and based on Pearson's linear correlation, moderate correlation was established (r=0.511) between them. In all three extractant (0.01M CaCl2, 1M KCl, 0.016 M KH2PO4) higher sulphate fractions were measured in the fertilized plots where superphosphate had been supplied for ages until 2010. The arylsulphatase activity of soil also was determined and ranged between 9.284 and 26.860 µg p-nitrophenol g-1 h-1. The lowest value was observed in the treatment with highest NPK2 dose, both in irrigated and non-irrigated areas.

Biochar phosphorus fertilizer effects on soil phosphorus availability.

Biochar is a potential material for making slow-releasing phosphorus (P) fertilizers for the sake of increasing soil P use efficiency and mitigating P losses. However, the long-term effects of P-laden biochars on soil P availability remains unconcerned. In this study, a laboratory-scale 70-days soil incubation experiment was conducted to study the effects of original and P-laden biochars on soil P availability and fractions. Two original biochars were derived from maize stalks by pyrolyzing at 350°C and 600°C. P was laden on those biochars by immersing biochars in saturated KH2PO4 solution for 24h. Eight treatments were set for the incubation experiment, which were soil, soil+triple-superphosphate (TSP), soil+350°C biochar, soil+600°C biochar, soil+TSP+350°C biochar, soil+TSP+600°C biochar, soil+350°C P-laden biochar, and soil+600°C P-laden biochar. Results showed that original biochars could decrease soil available P through P adsorption. And there were no significant differences of soil P fractions under the treatments of mineral P fertilizer and P-laden biochars. Whereas, compared to mineral P fertilizer, P-laden biochars, especially 600°C P-laden biochar, could maintain soil available P in a significantly higher level across the incubation. It was mainly because of the slow-releasing pattern of P laden on biochar and a more homogeneous soil P source distribution under P-laden biochar treatments. These results indicated that P-laden biochar could work as P fertilizer to improve soil P use efficiency.

Color tracing in the hydration process of α-Ca3(PO4)2:Eu

Eu-doped tricalcium phosphate (α-TCP:Eu) powders were obtained via solid-state reaction under air. The phase and microstructures of as-recieved samples and the hydration products soaked in 0.25 M K2HPO4 solution for different time was investigated using X-ray diffraction, SEM and Rietveld refinement method. The photoluminescence results of powders were changed with prolonged hydration time, not only the luminescence intensity of the products gradually depressed, but also the CIE chromaticity coordinates moved from bluish-green region of α-TCP phase to orange region of hydroxyapatite phase. The light emission change was confirmed by the color under the UV lamp. Therefore, results of this study suggested that the photoluminescence color of hydration products can be used as an obvious qualitative feature to trace the hydration process of α-TCP: Eu.

Bone-Inspired Mineralization with Highly Aligned Cellulose Nanofibers as Template.

Bioinspired by the aligned structure and building blocks of bone, this work mineralized the aligned bacterial cellulose (BC) through in situ mineralization using CaCl2 and K2HPO4 solutions. The cellulose nanofibers were aligned by a scalable stretching process. The aligned and mineralized bacterial cellulose (AMBC) homogeneously incorporated hydroxyapatite (HAP) with a high mineral content and exhibited excellent mechanical strength. The ordered 3D structure allowed the AMBC composite to achieve a high elastic modulus and hardness and the development of a nanostructure inspired by natural bone. The AMBC composite exhibited an elastic modulus of 10.91 ± 3.26 GPa and hardness of 0.37 ± 0.18 GPa. Compared with the nonaligned mineralized bacterial cellulose (NMBC) composite with mineralized crystals of HAP randomly distributed into the BC scaffolds, the AMBC composite possessed a 210% higher elastic modulus and 95% higher hardness. The obtained AMBC composite had excellent mechanical properties by mimicking the natural structure of bone, which indicated that the organic BC aerogel with aligned nanofibers was a promising template for biomimetic mineralization.

Effect of solution condition on hydroxyapatite formation in evaluating bioactivity of B2O3 containing 45S5 bioactive glasses

The effects of testing solutions and conditions on hydroxyapatite (HAp) formation as a means of in vitro bioactivity evaluation of B2O3 containing 45S5 bioactive glasses were systematically investigated. Four glass samples prepared by the traditional melt and quench process, where SiO2 in 45S5 was gradually replaced by B2O3 (up to 30%), were studied. Two solutions: the simulated body fluid (SBF) and K2HPO4 solutions were used as the medium for evaluating in vitro bioactivity through the formation of HAp on glass surface as a function of time. It was found that addition of boron oxide delayed the HAp formation in both SBF and K2HPO4 solutions, while the reaction between glass and the K2HPO4 solution is much faster as compared to SBF. In addition to the composition and medium effects, we also studied whether the solution treatments (e.g., adjusting to maintain a pH of 7.4, refreshing solution at certain time interval, and no disturbance during immersion) affect HAp formation. Fourier transform infrared spectrometer (FTIR) equipped with an attenuated total reflection (ATR) sampling technique and scanning electron microscopy (SEM) were conducted to identify HAp formation on glass powder surfaces and to observe HAp morphologies, respectively. The results show that refreshing solution every 24 h produced the fastest HAp formation for low boron-containing samples when SBF was used as testing solution, while no significant differences were observed when K2HPO4 solution was used. This study thus suggests the testing solutions and conditions play an important role on the in vitro bioactivity testing results and should be carefully considered when study materials with varying bioactivities.

Enhancing the corrosion resistance of aluminum by graphene oxide and reduced graphene oxide films

This study is carried out with the goal of improving the corrosion resistance of aluminum in a saline solution through coating with graphene oxide (GO) and reduced GO (ERGO). The GO layer was applied on an aluminum substrate and then electrochemically reduced by cyclic voltammetry in 0.01 M K2HPO4 solution to form a reduced graphene oxide layer. The surface morphology, structure, and crystallinity of the coated materials were characterized using scanning electron microscope (SEM), x-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy techniques. To study the electrochemical corrosion behavior of the coated aluminum substrate, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods were performed in 3.5 wt% NaCl solution. The results showed that both GO and ERGO films uniformly covered the surface of the aluminum substrates with layered structures. A noteworthy elimination of oxygen-containing functional groups (OFGs) occurred upon the electrochemical reduction of the film, yielding a highly-reduced ERGO layer on the substrate. Furthermore, the electrochemical reduction process significantly increased the thickness of the GO coating. The electrochemical test results exhibited that both GO, and ERGO layers improved the corrosion resistance of the bare aluminum substrate. However, electrochemical reduction of the GO layer had adverse effects on the corrosion barrier properties of the GO coating.

Quantification of phosphate ions by diffusive gradients in thin films technique using ferrihydrite as a binding gel and application to marine sediments

A diffusive gradient in thin films (DGT) is a newly developed analytical technique that can isolate and quantify the phosphate ions. A DGT unit comprises two components: the diffusion and binding layers. The diffusion layer comprises polyacrylamide hydrogel, whereas the binding layer from the oxide gel of ferrihydrite is impregnated with polyacrylamide gel. The technique employs a thin film of diffusive hydrogel in contact with a binding phase (ferrihydrite) that can bind phosphate ions. The diffusive and binding gels were characterized via infrared spectroscopy. The main peaks of the diffusive gel were observed at 3336 and 1636 cm−1, whereas those of the binding gel were observed at 3332 and 1638 cm−1. The DGT technique was evaluated as a way to quantify the amount of phosphate ions present in an aqueous KH2PO4 solution. After a contact time of 24 h, ferrihydrite exhibited a high affinity for phosphate, with an uptake efficiency of 98.17%. A linear relationship (R2 = 0.9938) was found to exist between the contact time (3−24 h) and uptake efficiency. Within the 0.2-1.2-mgL−1KH2PO4 concentration range, a linear relationship existed between analyte concentration and the mass of phosphate salt accumulated in the binding gel (R2 = 0.9748). The phosphate ion was eluted from the ferrihydrite hydrogel using 0.25-M H2SO4 over 30 min. The DGT unit was used to measure the phosphate level in six marine sediment samples from Jakarta Bay. The results revealed mass accumulation of P-containing compounds in the 1.009−2.4676-μg range.

New Alternative of Enhancing Hospital Hygiene Facing Pseudomonas aeruginosa Drug Resistance Impact of Hypertonic Saline Solutions on the Behavior of P. aeruginosa

The objective of this study was to elucidate the antibacterial effect of hypertonic saline of KH2PO4 and NaCl solutions for enhancing hospital hygiene facing drug resistance of the biofilm of Pseudomonas aeruginosa isolated from a hospital environment on an agar cetrimide medium. The variations of P. aeruginosa biofilm density were measured following optical surface density by a correlated imaging method. Inhibition tests of 90% of the biofilm in a selective liquid medium monitored by spectrophotometry showed inhibition rates of 91.2 and 91.1% for minimal biofilm inhibition concentrations of 5.4 and 3.6% for NaCl and KH2PO4, respectively. The results of the eradication tests of 50% of the biofilm showed minimal biofilm eradication concentrations of 6.3 and 3.6% and eradication ratios of 50.6 and 50.9% for NaCl and KH2PO4, respectively. In the case of a selective solid medium, the results exhibited a minimal biofilm inhibition concentration of 4.2 and 3.9%, a biofilm inhibition rate of 90.8 and 90.5%, and ...

Insights into 33phosphorus utilisation from Fe- and Al-hydroxides in Luvisol and Ferralsol subsoils

There is currently relatively little available information on subsoil phosphorus (P) use for crop production as a function of soil order. In this study, a rhizobox experiment was performed using subsoils of two reference soil groups, an Orthic Ferralsol and a Haplic Luvisol. To evaluate the immediate P uptake by wheat (Triticum aestivum L.) from different subsoil P pools during 14 days of growth, subsoil bands were spiked with KH2PO4 solution associated to Fe-hydroxide (33P-Fe), to Al-hydroxide (33P-Al), in free form (33P-OrthoP), or in trace amounts without any additional 31P (33P-NoP). At the beginning of the experiment, the soil water content was set at 75% of water-holding capacity, corresponding to an initial soil matric potential of −12 ± 1 kPa. During plant growth, soil moisture decreased in both soils, but soil matric potentials in both soils did not drop below field capacity (−33 kPa; pF 2.5). The shoot dry weights of the Ferralsol were 1.2 to 1.8 times those of the Luvisol. Despite elevated soil P availability in the Luvisol, shoot P concentrations did not differ between the two soils. The amount of 33P taken up by the shoots from the oxide phases was 15% to 40% greater in the Ferralsol treatments than in those in the Luvisol treatments. It was concluded that the more favourable physical soil conditions facilitated 33P uptake from both oxidic phases from the Ferralsol subsoil relative to the Luvisol subsoil, despite better P phytoavailability in the latter.

Zwitterions as novel phase forming components of aqueous biphasic systems

Abstract A novel class of aqueous biphasic systems (ABS) formed by zwitterions (ZI) has been investigated in the present work. A series of water soluble ZIs have been synthesized using triethylamine, N-Methylimidazole, N-Vinylimidazole, pyridine, N-Methylpyrrolidine, N-Ethylpiperidine and 1,4 butane sultone. The synthesized ZIs were explored for their ability to form biphasic systems in combination with aqueous inorganic salt solutions of K3PO4, K2HPO4 and K2CO3. The phase diagrams for all systems have been constructed through cloud point titration method at 298.15 K and atmospheric pressure. The phase behavior of ZI based ABS have been analyzed to understand the structural effects of ZIs as well as the effect of nature of salt used on the overall phase formation. Further the temperature dependence of the ZI based ABS was also explored by studying the phase behavior at variable temperatures of 298.15, 308.15 and 318.15 K. In order to estimate the applicability of proposed ZI based ABS, extraction experiments have been performed for an alkaloid i.e. caffeine for all synthesized ZIs with K3PO4 and at 298.15 K. ZI based ABS have been found to be capable of single step extraction of caffeine similar to IL based ABS thus providing the possibilities to explore these ZI based ABS as efficient extraction and separation systems.

Design and Validation of Synchronous QCT Calibration Phantom: Practical Methodology

IntroductionQuantitative computed tomography (QCT) can supplement dual x-ray absorptiometry by enabling geometric and compartmental bone assessments. Whole-body spiral CT scanners are widely available and require a short scanning time of seconds, in contrast to peripheral QCT scanners, which require several minutes of scanning time. This study designed and evaluated the accuracy and precision of a homemade QCT calibration phantom using a whole-body spiral CT scanner. Materials and MethodsThe QCT calibration phantom consisted of K2HPO4 solutions as reference. The reference material with various concentrations of 0, 50, 100, 200, 400, 1000, and 1200 mg/cc of K2HPO4 in water were used. For designing the phantom, we used the ABAQUS software. ResultsThe phantoms were used for performance assessment of QCT method through measurement of accuracy and precision errors, which were generally less than 5.1% for different concentrations. The correlation between CT numbers and concentration were close to one (R2 = 0.99). DiscussionBecause whole-body spiral CT scanners allow central bone densitometry, evaluating the accuracy and precision for the easy to use calibration phantom may improve the QCT bone densitometry test. ConclusionThis study provides practical directions for applying a homemade calibration phantom for bone mineral density quantification in QCT technique.

Combining phytoremediation with soil flushing for arsenic removal from contaminated soil

ABSTRACTArsenic (As) contamination poses a high risk to public health in China. Remediation of soil As contamination is an urgent need. Development of more effective remediation technologies is crucial in order to achieve remediation goals. In this study, pot experiments were carried out to study the As removal effectiveness of planting Pteris vittata L. (P.v.) and Lolium multiflorum L. (L.m.) in combination with in situ soil flushing using monopotassium phosphate (KH2PO4) solutions. Results showed that planting P.v. and L.m. in combination with 8 days of KH2PO4 solution soil flushing achieved 35.20% and 52.93%. As removal efficiency in the rhizosphere soil, respectively, which was significantly higher than 9.14% removal from soil flushing alone. Results also indicated that planting P.v. and L.m. changed the speciation of As to labile form, facilitating As removal from soil. Growing P.v. with in situ KH2PO4 flushing was more effective in remediating As-contaminated agricultural soil; L.m. could not be used in place of P.v to achieve the same remediation efficiency. This research provides an important guidance on plant screening for phytoremediation in combination with in situ flushing to remediate As-contaminated soil.

Validation of Thin-Layer Chromatography-Bioautographic Method for Determination of Streptomycin

Background: A simple bio-assay for determination of streptomycin hyphenated with planar chromatography techniques was developed. Objective: This study aims to validate the method for identification and determination of streptomycin in injection preparations with TLC-bioautography. Methods: Thin Layer Chromatography (TLC) was performed on the silica Gel GF-254 using KH2PO4 solution as mobile solvent. The visualization was performed by spraying 2% resorcinol. Direct bi autography was developed using Escherichia coli ATCC 25922 as a bacterial test, grown on the nutrient agar medium at 37oC for 24 hours. The method was validated corresponding to linearity, limit of detection (LOD), intra day precision, and accuracy parameters. The accuracy was measured using streptomycin injection as a sample. Results: The Results showed that the KH2PO4 solution at 7.5% concentration was found to be the optimized solvent with Rf value of 0.5. The linear equation was y = 10.176x + 4.046 at 150 - 350 µg/mL concentration range with the linearity coefficient, Limit of Detection, accuracy, and variation coefficient were 0.9907; 40 ppm; 96.37 + 2.22% (with an RSD value of 2.31%); and 1.63 respectively. Conclusion: The prospective TLC-bioautographic method was applied for the identification and determination of streptomycin in a preparation using a single eluent KH2PO4. The eluent system optimization remains necessary for the identification and determination of the mixture of streptomycin with other antibiotics, such as aminoglycoside groups.

Stability indicating determination of Albendazole in bulk drug and pharmaceutical dosage form by chromatographic and spectrophotometric methods

Two sensitive stability indicating methods were developed for the determination of Albendazole in bulk drug and pharmaceutical dosage form, in presence of its alkaline-degradation product without any interference. The first one was isocratic HPLC method; using Agilent Zorbax Extend C-18 (150 × 4.6 mm, 5 μ) column, ' KH2PO4 solution and acetonitrile' in the ratio of (15:85v/v) as a mobile phase with a flow rate 0.6 ml min −1 and UV-detection at 295.0 nm, where the investigated drug could be quantized in a concentration range 1.00–50.00 μgml−1 with regression coefficient (r) of 0.9989. On the other hand, the second adopted method was derivative ratio spectrophotometry; where Albendazole could be determined in a concentration range 2.00–20.00 μg ml−1 at 281.4 and at 292.6 nm-296.8 nm (Peak-to-Peak difference) with a mean percentage recovery of 100.84 and 99.88 and with regression coefficient (r) of 0.9998 and 0.9999, respectively. The utilized methods were validated according to International Conference Harmonization (ICH) guidelines and successfully applied for analysis of bulk powder and pharmaceutical dosage form. All the obtained results were statistically compared to the chromatographic reported method and no significant difference was found; indicating the accuracy, sensitivity and reproducibility of the used methods.

Does an electronic continuum correction improve effective short-range ion-ion interactions in aqueous solution?

Non-polarizable force fields for hydrated ions not always accurately describe short-range ion-ion interactions, frequently leading to artificial ion clustering in bulk aqueous solutions. This can be avoided by adjusting the nonbonded anion-cation or cation-water Lennard-Jones parameters. This approach has been successfully applied to different systems, but the parameterization is demanding owing to the necessity of separate investigations of each ion pair. Alternatively, polarization effects may effectively be accounted for using the electronic continuum correction (ECC) of Leontyev et al. [J. Chem. Phys. 119, 8024 (2003)], which involves scaling the ionic charges with the inverse square-root of the water high-frequency dielectric permittivity. ECC has proven to perform well for monovalent salts as well as for divalent salts in water. Its performance, however, for multivalent salts with higher valency remains unexplored. The present work illustrates the applicability of the ECC model to trivalent K3PO4 and divalent K2HPO4 in water. We demonstrate that the ECC models, without additional tuning of force field parameters, provide an accurate description of water-mediated interactions between salt ions. This results in predictions of the osmotic coefficients of aqueous K3PO4 and K2HPO4 solutions in good agreement with experimental data. Analysis of ion pairing thermodynamics in terms of contact ion pair (CIP), solvent-separated ion pair, and double solvent-separated ion pair contributions shows that potassium-phosphate CIP formation is stronger with trivalent than with divalent phosphate ions.

An investigation on the solid–liquid phase equilibrium of the quaternary system KH2PO4–H3PO4–CH2OHCH2OH–H2O

The removal of HCl and the precipitation of KH2PO4 are the crucial factors to produce KH2PO4 from H3PO4 and KCl. A new process is proposed by introducing ethylene glycol to decrease the solubility of HCl and to precipitate KH2PO4. The solubility of KH2PO4 in H3PO4–CH2OHCH2OH–H2O system was studied systematically by isothermal solution saturation method. The results demonstrate that ethylene glycol is an excellent precipitant for the crystallization of KH2PO4 from the solution of KH2PO4–H3PO4–CH2OHCH2OH–H2O. The increase of ethylene glycol mass fraction brings a remarkably inhibitive effect on the dissolution of KH2PO4 in H3PO4 aqueous solution. Based on the phase equilibrium diagram of quaternary system KH2PO4–H3PO4–CH2OHCH2OH–H2O, KH2PO4 can be precipitated by cooling crystallization, evaporation crystallization or antisolvent crystallization. Focused beam reflectance measurement was used to online monitor the chord length distribution during the crystallization process. The results indicate that the particle size distribution is controllable in the process of continuous feeding antisolvent crystallization. The results provide a feasible way to separate KH2PO4 from the reaction solution of KCl and H3PO4.

Efficient Removal of Polyvalent Metal Impurities from KH2PO4 by Crystallization

The separation factors of metal impurities for potassium dihydrogen phosphate crystallization from nonstoichiometric solutions have been experimentally determined. Based on the results obtained, a method has been proposed that makes it possible to obtain a material containing aluminum, iron, chromium, and titanium at a level of ~5 × 10–2 ppm by weight from commercially available raw materials. In this method, a KH2PO4 solution is purified due to partial crystallization of the macrocomponent, so that the above impurities are concentrated in the solid phase. The purified solution is then boiled down with KOH additions.

Mixed Network Former Effect on Structure, Physical Properties, and Bioactivity of 45S5 Bioactive Glasses: An Integrated Experimental and Molecular Dynamics Simulation Study.

Boron-containing bioactive glasses display a strong potential in various biomedical applications lately due to their controllable dissolution rates. In this paper, we prepared a series of B2O3/SiO2-substituded 45S5 bioactive glasses and performed in vitro biomineralization tests with both simulated body fluid and K2HPO4 solutions to evaluate the bioactivities of these glasses as a function of boron oxide to silica substitution. The samples were examined with scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectrometry after immersing them in the two solutions (simulated body fluid and K2HPO4) up to 3 weeks. It was found that introduction of boron oxide delayed the formation of hydroxyapatite, but all the glasses were shown to be bioactive. Molecular dynamics (MD) simulations were used to complement the experimental efforts to understand the structural changes due to boron oxide to silica substitution by using newly developed partial charge composition-dependent potentials. Local structures around the glass network formers, medium-range structural information, network connectivity, and self-diffusion coefficients of ions were elucidated from MD simulation. Relationships between boron content and glass properties such as structure, density, glass transition temperature, and in vitro bioactivity were discussed in light of both experimental and simulation results.

Quantitative performance evaluation of 124I PET/MRI lesion dosimetry in differentiated thyroid cancer

The aim was to investigate the quantitative performance of 124I PET/MRI for pre-therapy lesion dosimetry in differentiated thyroid cancer (DTC). Phantom measurements were performed on a PET/MRI system (Biograph mMR, Siemens Healthcare) using 124I and 18F. The PET calibration factor and the influence of radiofrequency coil attenuation were determined using a cylindrical phantom homogeneously filled with radioactivity. The calibration factor was 1.00 ± 0.02 for 18F and 0.88 ± 0.02 for 124I. Near the radiofrequency surface coil an underestimation of less than 5% in radioactivity concentration was observed. Soft-tissue sphere recovery coefficients were determined using the NEMA IEC body phantom. Recovery coefficients were systematically higher for 18F than for 124I. In addition, the six spheres of the phantom were segmented using a PET-based iterative segmentation algorithm. For all 124I measurements, the deviations in segmented lesion volume and mean radioactivity concentration relative to the actual values were smaller than 15% and 25%, respectively. The effect of MR-based attenuation correction (three- and four-segment µ-maps) on bone lesion quantification was assessed using radioactive spheres filled with a K2HPO4 solution mimicking bone lesions. The four-segment µ-map resulted in an underestimation of the imaged radioactivity concentration of up to 15%, whereas the three-segment µ-map resulted in an overestimation of up to 10%. For twenty lesions identified in six patients, a comparison of 124I PET/MRI to PET/CT was performed with respect to segmented lesion volume and radioactivity concentration. The interclass correlation coefficients showed excellent agreement in segmented lesion volume and radioactivity concentration (0.999 and 0.95, respectively). In conclusion, it is feasible that accurate quantitative 124I PET/MRI could be used to perform radioiodine pre-therapy lesion dosimetry in DTC.