Lower risk of gout in sodium glucose cotransporter 2 (SGLT2) inhibitors versus dipeptidyl peptidase-4 (DPP4) inhibitors in type-2 diabetes.

OBJECTIVES: The effects of sodium-glucose cotransporter 2 inhibitors (SGLT2I) vs dipeptidyl peptidase-4 inhibitors (DPP4I) on the risk of new-onset gout remains unknown. This study aims to compare the effects of SGLT2I against DPP4I on gout risks. METHODS: This was a retrospective population-based cohort study of patients with type-2 diabetes mellitus treated with SGLT2I or DPP4I between 1 January 2015 and 31 December 2020 in Hong Kong. The study outcomes are new-onset gout and all-cause mortality. Propensity score matching (1:1 ratio) between SGLT2I and DPP4I was performed. Univariable and multivariable Cox regression models were conducted. Competing risks models and multiple approaches based on the propensity score were applied. RESULTS: This study included 43 201 patients [median age: 63.23 years old (Interquartile range, IQR): 55.21-71.95, 53.74% males; SGLT2I group: n = 16 144; DPP4I group: n = 27 057] with a median follow-up of 5.59 years (IQR: 5.27-5.81 years) since initial drug exposure. The incidence rate of developing gout [Incidence rate (IR): 2.5; 95% CI: 2.2, 2.9] among SGLT2I users was significantly lower than DPP4I users (IR: 5.2; 95% CI: 4.8, 5.8). SGLT2I was associated with 51% lower risks of gout (HR: 0.49; 95% CI: 0.42, 0.58; P-value < 0.0001) and 51% lower risks of all-cause mortality (HR: 0.49; 95% CI: 0.42, 0.58; P-value < 0.0001) after adjusting for significant demographics, past comorbidities, medications and laboratory results. The results remained consistent on competing risk and other propensity score approaches. CONCLUSIONS: SGLT2I use was associated with lower risks of new gout diagnosis compared with DPP4I use.

The Effect of Repetitive Transcranial Magnetic Stimulation in Synchronization with Effortful Swallowing on Post-stroke Dysphagia.

Either effortful swallowing exercise or repetitive transcranial magnetic stimulation (rTMS) is considered as an effective method to treat dysphagia after stroke. Thus, synchronizing these two interventions may improve the efficiency of treatment. This trial intended to explore the effects of rTMS and effortful swallowing exercise on the recovery of swallowing function in patients after stroke. A total of 56 patients with post-stroke dysphagia who were able to actively cooperate with the training were analyzed in this study. We experimented with different intervention effects of rTMS synchronization with effortful swallowing training (group 1), rTMS (group 2), and traditional swallowing training alone (group 3). Every patient completed conventional swallowing training 5 days a week for 2 weeks. Patients in group 1 and group 2 underwent 10 consecutive sessions of 5 Hz rTMS over the affected mylohyoid cortical region. Fiberoptic endoscopic dysphagia severity scale (FEDSS), penetration/aspiration scale (PAS), standardized swallowing assessment (SSA), and functional oral intake scale (FOIS) were assessed and compared across the groups. No significant difference in FEDSS, PAS, SSA, or FOIS scores was found at baseline among the three groups. The mean change values of the FEDSS score, PAS score, SSA score, and FOIS score between baseline and post-intervention of the three groups (H = 16.05, P < 0.001; H = 21.70, P < 0.001; F (2, 53) = 9.68, P < 0.001; H = 18.26, P < 0.001; respectively) were statistically significant. In addition, the mean change values of FEDSS, PAS, SSA, and FOIS scores in participants in group 1 (all P < 0.001) and group 2 (P = 0.046; P = 0.045; P = 0.028; P = 0.032; respectively) were significantly higher than in group 3. Similarly, the mean change values of FEDSS, PAS, SSA, and FOIS scores were significantly higher in participants in group 1 than in group 2 (P = 0.046; P = 0.038; P = 0.042; P = 0.044; respectively). The results revealed that the conjunction of rTMS and effortful swallowing training was an effective method to facilitate the recovery of swallowing function in stroke patients. The present clinical trial provided a new treatment method for the functional restoration of swallowing in stroke patients, which may further facilitate the recovery of swallowing function in stroke patients with swallowing disorders.

Risk of New-Onset Prostate Cancer for Metformin Versus Sulfonylurea Use in Type 2 Diabetes Mellitus: A Propensity Score-Matched Study.

BACKGROUND: The aim of this study was to compare the risks of new-onset prostate cancer between metformin and sulfonylurea users with type 2 diabetes mellitus (T2DM). METHODS: This population-based retrospective cohort study included male patients with T2DM presenting to public hospitals/clinics in Hong Kong between January 1, 2000, and December 31, 2009. We only included patients prescribed either, but not both, metformin or sulfonylurea. All patients were followed up until December 31, 2019. The primary outcome was new-onset prostate cancer and the secondary outcome was all-cause mortality. One-to-one propensity score matching was performed between metformin and sulfonylurea users based on demographics, comorbidities, antidiabetic and cardiovascular medications, fasting blood glucose level, and hemoglobin A1c level. Subgroup analyses based on age and use of androgen deprivation therapy were performed. RESULTS: The final study cohort consisted of 25,695 metformin users (mean [SD] age, 65.2 [11.8] years) and 25,695 matched sulfonylurea users (mean [SD] age, 65.3 [11.8] years) with a median follow-up duration of 119.6 months (interquartile range, 91.7-139.6 months) after 1:1 propensity score matching of 66,411 patients. Metformin users had lower risks of new-onset prostate cancer (hazard ratio, 0.80; 95% CI, 0.69-0.93; P=.0031) and all-cause mortality (hazard ratio, 0.89; 95% CI, 0.86-0.92; P<.0001) than sulfonylurea users. Metformin use was more protective against prostate cancer but less protective against all-cause mortality in patients aged <65 years (P for trend <.0001 for both) compared with patients aged ≥65 years. Metformin users had lower risk of all-cause mortality than sulfonylurea users, regardless of the use of androgen deprivation therapy (P for trend <.0001) among patients who developed prostate cancer. CONCLUSIONS: Metformin use was associated with significantly lower risks of new-onset prostate cancer and all-cause mortality than sulfonylurea use in male patients with T2DM.

Therapeutic Role of Additional Mirror Therapy on the Recovery of Upper Extremity Motor Function after Stroke: A Single-Blind, Randomized Controlled Trial.

Background: Rehabilitation of upper extremity hemiplegia after stroke remains a great clinical challenge, with only 20% of patients achieving a basic return to normal hand function. How to promote the recovery of motor function at an early stage is crucial to the life of the patient. Objectives: To invest the effects of additional mirror therapy in improving upper limb motor function and activities of daily living in acute and subacute stroke patients, and further explore the effects of other factors on the efficacy of MT. Methods: Participants who presented with unilateral upper extremity paralysis due to a first ischemic or hemorrhagic stroke were included in the study. They were randomly allocated to the experimental or control group. Patients in the control group received occupational therapy for 30 minutes each session, six times a week, for three weeks, while patients in the experimental group received 30 minutes of additional mirror therapy based on occupational therapy. The primary outcome measures were Fugl-Meyer Assessment-upper extremity (FMA-UE), Action Research Arm Test (ARAT), and Instrumental Activity of Daily Living (IADL) which were evaluated by two independent occupational therapists before treatment and after 3-week treatment. A paired t-test was used to compare the values between pretreatment and posttreatment within an individual group. Two-sample t-test was utilized to compare the changes (baseline to postintervention) between the two groups. Results: A total of 52 stroke patients with unilateral upper extremity motor dysfunction who were able to actively cooperate with the training were included in this study. At baseline, no significant differences were found between groups regarding demographic and clinical characteristics (P > 0.05 for all). Upper limb motor function and ability to perform activities of daily living of the patients were statistically improved in both groups towards the third week (P < 0.05). In addition, statistical analyses showed more significant improvements in the score changes of FMA-UE and IADL in the experimental group compared to the control group after treatment (P < 0.05), but no significant difference was observed in the ARAT score changes between the two groups (P > 0.05). The subgroup analysis showed that no significant heterogeneity was observed in age, stroke type, lesion side, and clinical stage (P > 0.05). Conclusion: In conclusion, some positive changes in aspects of upper limb motor function and the ability to perform instrumental activities of daily living compared with routine occupational therapy were observed in additional mirror therapy. Therefore, the application of additional mirror therapy training should be reconsidered to improve upper extremity motor in stroke patients.

A hemicyanidin-based NIR fluorescent probe for detection of H2S and imaging study in cells and mice.

The selective detection of hydrogen sulfide in physiological and pathological processes has gained substantial attention in recent years. However, the real-time detection of hydrogen sulfide remains an elusive goal. In this work, a new type of hemicyanidin-based fluorescent "turn-on" probe NTR-HS (Ex = 680 nm, Em = 760 nm) was developed to detected H2S in a very short time (3 min). The fluorescence quantum yield is 0.15 and accompanied with a noticeable color change from violet to blue that can be used to detect H2S in the range 1.04 × 10-7-4 × 10-5 M with a limit of detection of 1.04 x 10-7 M. The NTR-HS probe was also used for imaging of endogenous hydrogen sulfide and mitochondrial localization in HCT116 and HeLa cells. The detection mechanism was studied through fluorescence, UV-Vis, NMR, and mass analysis. Notably, the probe was successfully used to imaging H2S in mice and locating hydrogen sulfide in the large intestine of mice.

Piezoelectric energy harvesting systems using mechanical tuning techniques.

In this review, we review the recent research progress and results of piezoelectric energy harvesters applying mechanical tuning techniques in terms of literature background, methods of mechanical tuning, and practical applications. In the past few decades, piezoelectric energy harvesting techniques and mechanical tuning techniques have received increasing attention and made significant progress. Mechanical-tuning techniques are those that allow the resonant vibration energy harvesters the mechanical resonant frequency values to be adjusted to coincide with the excitation frequency. According to the different tuning methods, this review classifies mechanical-tuning techniques based on magnetic action, different piezoelectric materials, axial load, the variable center of gravity, various stresses, and self-tuning and summarizes the corresponding research results, comparing the differences between the same methods. In addition, the current application of the mechanical-tuning techniques is introduced, and the future development of mechanical tuning techniques is analyzed, facilitating the reader to better understand how mechanical-tuning techniques can improve the output performance of energy harvesters.

Design and study of an eccentric wheel drive-based rotating piezoelectric energy harvester.

A nonlinear rotating piezoelectric energy harvester (N-RPEH) driven by eccentric wheels is proposed to collect rotational energy in the environment. Driven by external rotational motion, an eccentric wheel converts rotational motion into linear motion and realizes electrical energy output through magnetic coupling. To increase the effectiveness of the equipment's energy conversion process, this article aims to transform the rotational motion of an eccentric wheel into a linear motion of a motion board. The effects of the motion board's length L, the cylindrical magnet's height H, and the mass block M at the piezoelectric patch's end on the output performance of N-RPEH are explained by theoretical modeling and simulation. Through theoretical analysis, simulation, and experiment, it is found that when L = 120 mm, H = 6 mm, and M = 5.0 g (medium mass), the output voltage reaches the maximum of 14.16 V. Under this parameter, N-RPEH can produce a maximum power of 7.0688 mW when the external resistance value is 2 kΩ. Application experiments show that N-RPEH can light up 60 light-emitting diodes. Therefore, the proposed N-RPEH can effectively collect rotational energy and has a wide range of potential applications in wireless sensor networks.

A novel energy harvester based on dual vibrating mechanisms with self-actuation.

This paper introduced a novel energy harvester with a tunnel and drop-shaped bluffbody for self-actuation and wind speed sensing. The harvester exhibits dual vibrating mechanisms of vortex-induced vibration (VIV) and galloping. Theoretical and numerical analyses were conducted to study the energy conversion relationship and fluid field of the harvester, and the conclusions were verified by controlled variable experiments. The optimal design values of inlet angle I 40°, polyvinylidene fluoride (PVDF) angle P 10°, and exit angle E 10° were demonstrated with the highest output of 10.42 Vp-p at the wind speed of 18 m/s. The output voltage of the PVDF energy harvester has a reliable relationship with the wind speed as a function of wind speed sensor, which could be applied for meteorological information collection and fluid flow rate monitoring with further study conducted underwater.

USP25 UPREGULATION BOOSTS GSDMD -MEDIATED PYROPTOSIS OF ACINAR CELLS IN ACUTE PANCREATITIS.

ABSTRACT: Acute pancreatitis (AP) is an inflammation-associated disorder in the digestive system. Ubiquitin-specific peptidase 25 ( USP25 ) can modulate inflammation in diseases. This study expounded on the role of USP25 in pyroptosis of acinar cells in AP. Acinar cells were treated with lipopolysaccharide (LPS) and caerulein (CRE) to induce AP. Afterward, the expression patterns of USP25 , microRNA (miR)-10a-5p, and Krüppel-like factor 4 ( KLF4 ) in acinar cells were examined. Then, acinar cell viability and levels of NLR family pyrin-domain containing 3 (NLRP3), cleaved caspase-1, cleaved N -terminal gasdermin D ( GSDMD - N ), interleukin (IL)-1ß, and IL-18 were determined. We observed that USP25 was highly expressed in AP models, and silencing USP25 increased cell viability and inhibited pyroptosis of AP acinar cells. The bindings of USP25 to KLF4 and miR-10a-5p to KLF4 and the GSDMD 3'UTR sequence were validated. We found that USP25 binding to KLF4 inhibited ubiquitination degradation of KLF4 , KLF4 transcriptionally decreased miR-10a-5p expression, and miR-10a-5p targeted GSDMD expression. Finally, rescue experiments proved that KLF4 overexpression or miR-10a-5p suppression enhanced pyroptosis of AP acinar cells. Overall, USP25 stabilized KLF4 expression through deubiquitination, limited miR-10a-5p expression, and increased GSDMD expression, finally promoting pyroptosis of acinar cells in AP.

The effects of physiotherapy treatments on dysphagia in Parkinson's disease: A systematic review of randomized controlled trials.

BACKGROUND: The prevalence of swallowing disorders in Parkinson's disease (PD) is relatively high. Different physiotherapy interventions for swallowing disorders are available but there is a lack of evidence-based medicine for their effectiveness in PD. OBJECTIVE: The purpose of this systematic review was to investigate the effects of different physiotherapy interventions on dysphagia in PD. METHODS: This systematic review was conducted according to PRISMA guidelines. We methodically searched databases including PubMed, PEDro, Cochrane Library, Embase, and Web of Science. Studies of any language published up to March 2022 were searched. Randomized controlled trials (RCTs) of non-pharmacological treatment for dysphagia in PD were selected in strict accordance with our exclusion and inclusion criteria. RESULTS: In total, we identified and included 10 RCTs in patients with PD undergoing dysphagia. This review involved seven rehabilitation treatments, including acupuncture, expiratory muscle strength training (EMST), repetitive transcranial magnetic stimulation (rTMS), video-assisted swallowing therapy (VAST), electrical stimulation, and speech and language therapy (SLT). CONCLUSION: For physiotherapy treatments, including acupuncture, EMST, high-frequency rTMS and VAST may be effective treatments for dysphagia in patients with PD. However, there was not enough evidence that electrical stimulation has therapeutic effects on dysphagia in patients with PD.

Baduanjin improves neck pain and functional movement in middle-aged and elderly people: A systematic review and meta-analysis of randomized controlled trials.

Background: Neck pain (NP), one of the most common musculoskeletal diseases, exercises a great influence on the daily life of individuals, especially the elderly. Baduanjin is a traditional Qigong therapy from China, but there is no evidence for its use in the treatment of neck pain in middle-aged and elderly people. Objective: We hope to summarize the efficacy evidence of Baduanjin in the treatment of middle-aged and elderly patients with neck pain (NP) for the first time, conduct a systematic review and meta-analysis, and provide basic evidence-based evidence for clinical practice. Methods: Two researchers collectively searched PubMed, Web of Science, Embase, Cochrane Library, China Biology Medicine disk (Sino-Med), China National Knowledge Infrastructure (CNKI), Wanfang database, and China Science and Technology Journal Database (VIP). The search time is set from initial to 27 September 2022, to find out RCT articles that may meet the criteria. The risk bias assessment tool Cochrane was applied to assess the methodological quality of involved studies. RevMan 5.3 was used for the meta-analysis with a mean difference (MD) and 95% confidence interval (CI), and the model type was a random effects model. The VAS scores of the intervention and control groups were extracted and the results of the meta-analysis were presented using a forest plot. Results: In total, 13 randomized controlled trials were meta-analyzed, including 840 patients. The results turned out that the VAS score in the intervention group was below the control group, which was statistically significant [MD = -1.15, 95% CI (-1.39, -0.92) and P < 0. 001]. The result of general efficiency suggests that the Baduanjin group was better than the control group [RR = 1.19, 95% CI (1.10, 1.29), P < 0.001]. Conclusion: The existing results seem to show that Baduanjin is safe and has a trend of positive benefits in the treatment of neck pain in middle-aged and elderly people. However, considering the limitations of this study, we need to be cautious in our conclusions, and more studies are needed to verify it in future.

A Novel Ocean Thermal Energy Driven System for Sustainable Power and Fresh Water Supply.

The ocean thermal energy conversion (OTEC) is a potential substitute for traditional power plants in tropical islands and coastal regions. However, the OTEC power generation cycle has low thermal efficiency and the integrated utilization is imperative, in which an OTEC coupled with seawater desalination is the most attractive option. Membrane distillation (MD) has distinct advantages making itself a competitive process for seawater desalination, especially the feature that the drained warm seawater from the OTEC power plant can be recycled, improving the integrated output of the OTEC system. In this study, an innovative OTEC system coupling a power generation sub-cycle (PGC) and a water production sub-cycle (WPC) was proposed, composed of the upstream organic Rankine cycle and the downstream membrane distillation modules. The mass, energy and exergy balance of the individual equipment, the sub-cycles and the whole system were performed by constructing the corresponding balance models. The thermal dynamic parameters were calculated, and the performance of power generation and water production was predicted. The results showed that by coupling with the MD desalination, the thermal efficiency of the OTEC system can be greatly improved from 2.19% to 25.38% while the exergy efficiency changed little. For a 100 kW OTEC power generation cycle, the water production rate approached 58.874 t/d. In addition, the economic analysis based on the electricity and water sale was carried out, and the profit can be improved by extra water production, especially in the Hawaii and Rainbow Beach by nearly 20%.

Effectiveness of Taijiquan in treating insomnia: A systematic review and meta-analysis of randomized controlled studies.

Background: Sleep efficiency of <80% based on actigraphy was defined as insomnia as self-reported difficulty falling asleep or waking up at night three to four times per week. It is known that adequate sleep is very important for human wellbeing, affecting people's work and life, insomnia will seriously damage our daily life. There is no recognized non-drug treatment. Studies have found that Taijiquan has a positive effect on insomnia patients. This systematic review and meta-analysis will evaluate the effect of Taijiquan on insomnia. Methods: To find all randomized controlled trials exploring the effects of Taijiquan on insomnia patients in Chinese and English, eight databases (Pubmed, Embase, Cochrane library, Web of Science, CNKI, CBM, VIP, and Wanfang Data) were searched. The retrieval time is from database construction to October 2021. Searches were conducted in both English and Chinese language. A meta-analysis by mean difference (MD) and 95% confidence interval (CI) was performed with RevMan 5.3. The risk of bias for each study was accounted for according to the Cochrane Handbook. Our primary outcome was Pittsburg Sleep Quality Index. We explored sources of heterogeneity by comparing effect sizes across different types of etiology, country, control group, and intervention type. The protocol was pre-registered with PROSPERO, CRD42021284511. Results: Twenty-one RCTs published between 2004 and 2021 with 2,022 participants were included in this study. Twenty-one randomized controlled studies showed that Tai Chi significantly improved PSQI scores in patients with cancer, muscle fibrosis, and sub-health insomnia [MD = -1.16, 95% CI (-1.62, -0.71), P < 0.01]; There is insufficient evidence of improvement in patients with cerebrovascular disease [MD = -0.54, 95% CI (-1.58, 0.51), P = 0.31]; 8-form, 10-form or 24-form Yang's Taijiquan had the same effect in improving PSQI [MD = -1.33, 95% CI (-1.85, -0.81), P < 0.01]. When there is no treatment, exercise, exercise and health education as the control, taijiquan has a significant effect on insomnia treatment, and there is no difference in efficacy compared with cognitive behavioral therapy and health education (usual care) alone. Conclusions: The results of the study showed that Taijiquan significantly improved sleep quality in healthy adults and patients with chronic diseases, which suggests that Taijiquan may be considered as an alternative behavioral therapy in the treatment of insomnia. In the future, more high-quality, well-controlled randomized trials are needed to better inform clinical decisions.

Simulation and Experimental Investigation of the Vacuum-Enhanced Direct Membrane Distillation Driven by a Low-Grade Heat Source.

Vacuum-enhanced direct contact membrane distillation (VEDCMD) has been proven experimentally to improve the permeate flux, compared with direct contact membrane distillation (DCMD). However, the theoretical mechanism for its transmembrane transfer process has not been revealed sufficiently. In this paper, with full consideration of the different driving forces of diffusion and Poiseuille flow under the vacuum enhancing condition, a theoretical transmembrane model for mass and heat transfer in VEDCMD is proposed. The CFD model and experimental platform are established to verify the theoretical model. The simulated results agree with the experimental data well, and nearly 200% improvement of the permeate flux is obtained when the permeate pressure drops to 30 kPa. The flow fields of the flow along the membrane surface are obtained and analyzed, with good consistency in the variation of the permeate flux. Since all the parameters of the proposed model are independent of the operating condition, the model is much easier for use and has better adaptability to fluctuating operating conditions.

Hip fractures risks in edoxaban versus warfarin users: A propensity score-matched population-based cohort study with competing risk analyses.

OBJECTIVE: The three direct oral anticoagulants (DOAC), rivaroxaban, apixaban and dabigatran have been associated with lower risks of fractures compared to warfarin. However, no large scale studies have explored the associations with the newest DOAC, edoxaban, with fracture risk. The present study aims to elucidate the effects of edoxaban on the risk of hip fracture amongst elderly patients by comparing the incidence of new onset hip fracture between edoxaban and warfarin users in a Chinese population. METHODS: This was a retrospective population-based cohort study of patients with edoxaban or warfarin use between January 1st, 2016 and December 31st, 2019 in Hong Kong, China. Patients with less than one-month exposure, medication switching between warfarin and edoxaban, those who died within 30 days after drug exposure, prior human immunodeficiency virus infection, age <50 years old, and those with prior hip fractures were excluded. Propensity score matching (1:2) between edoxaban and warfarin users using the nearest neighbour method was performed based on demographics, prior comorbidities, and use of different medications. The study outcomes were new onset hip fractures, medically attended falls and all-cause mortality. RESULTS: A total of 5014 patients including 579 edoxaban users and 4435 warfarin users (median age: 70 years old [interquartile range (IQR): 62-79], 56.66% males) with a median follow-up of 637.5 (IQR: 320-1073) days were included. In the matched cohort, edoxaban users had significantly lower rates of new onset hip fractures, medically attended falls and all-cause mortality. The protective value of edoxaban use against new onset hip fracture (hazard ratio [HR]: 0.13, 95% confidence interval [CI]: [0.03-0.54], p = 0.0051), medically attended falls (HR: 0.47, [0.29-0.75], p = 0.0018) and all-cause mortality (HR: 0.61, [0.42-0.87], p = 0.0059) in comparison to warfarin use persisted after matching. The significant relationship between edoxaban use and lower fracture risk was preserved in all sensitivity analyses using different approaches using the propensity score. CONCLUSIONS: Edoxaban use is associated with lower risks of new onset hip fractures, medically attended falls and mortality risks compared to warfarin after propensity score matching.

Errata: Spectral response model for a multibin photon-counting spectral computed tomography detector and its applications.

[This corrects the article DOI: 10.1117/1.JMI.2.3.033502.].

Spectral response model for a multibin photon-counting spectral computed tomography detector and its applications.

Variations among detector channels in computed tomography can lead to ring artifacts in the reconstructed images and biased estimates in projection-based material decomposition. Typically, the ring artifacts are corrected by compensation methods based on flat fielding, where transmission measurements are required for a number of material-thickness combinations. Phantoms used in these methods can be rather complex and require an extensive number of transmission measurements. Moreover, material decomposition needs knowledge of the individual response of each detector channel to account for the detector inhomogeneities. For this purpose, we have developed a spectral response model that binwise predicts the response of a multibin photon-counting detector individually for each detector channel. The spectral response model is performed in two steps. The first step employs a forward model to predict the expected numbers of photon counts, taking into account parameters such as the incident x-ray spectrum, absorption efficiency, and energy response of the detector. The second step utilizes a limited number of transmission measurements with a set of flat slabs of two absorber materials to fine-tune the model predictions, resulting in a good correspondence with the physical measurements. To verify the response model, we apply the model in two cases. First, the model is used in combination with a compensation method which requires an extensive number of transmission measurements to determine the necessary parameters. Our spectral response model successfully replaces these measurements by simulations, saving a significant amount of measurement time. Second, the spectral response model is used as the basis of the maximum likelihood approach for projection-based material decomposition. The reconstructed basis images show a good separation between the calcium-like material and the contrast agents, iodine and gadolinium. The contrast agent concentrations are reconstructed with more than 94% accuracy.

Energy-resolved CT imaging with a photon-counting silicon-strip detector.

Photon-counting detectors are promising candidates for use in the next generation of x-ray computed tomography (CT) scanners. Among the foreseen benefits are higher spatial resolution, better trade-off between noise and dose and energy discriminating capabilities. Silicon is an attractive detector material because of its low cost, mature manufacturing process and high hole mobility. However, it is sometimes overlooked for CT applications because of its low absorption efficiency and high fraction of Compton scatter. The purpose of this work is to demonstrate that silicon is a feasible material for CT detectors by showing energy-resolved CT images acquired with an 80 kVp x-ray tube spectrum using a photon-counting silicon-strip detector with eight energy thresholds developed in our group. We use a single detector module, consisting of a linear array of 50 0.5×0.4 mm detector elements, to image a phantom in a table-top lab setup. The phantom consists of a plastic cylinder with circular inserts containing water, fat and aqueous solutions of calcium, iodine and gadolinium, in different concentrations. By using basis material decomposition we obtain water, calcium, iodine and gadolinium basis images and demonstrate that these basis images can be used to separate the different materials in the inserts. We also show results showing that the detector has potential for quantitative measurements of substance concentrations.