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1.
Kidney Med ; 6(3): 100776, 2024 Mar.
Article in English | MEDLINE | ID: mdl-38435073

ABSTRACT

Rationale & Objective: High-dose steroids are recommended for the induction of idiopathic nephrotic syndrome. The aim of this study was to compare standard induction therapy with Mycophenolate Mofetil (MMF). We hypothesized that MMF could be noninferior to steroids in maintaining steroid-induced remission. The second aim was to reduce steroid-induced side effects. Study Design: This was an observational study. Setting & Population: Patients 2-11 years with first episode of nephrotic syndrome who entered remission within 2 weeks of standard steroid treatment were eligible for enrollment. Patients in the experimental group completed 12-week induction with MMF, whereas the control group continued a standard 12-week steroid protocol. Exposures: MMF and prednisolone were used in the study. Outcomes: The primary study outcomes were relapse rate and relapse-free interval during a 52-week follow-up. Analytical Approach: Descriptive statistics were used for analysis. Results: Ten of 41 eligible patients consented to participate in the MMF group and 8 completed the study. The control group included 31 patients, with 23 patients who completed 52 weeks follow-up. During the induction phase, 3 out of 10 patients (30%) in the MMF group and 1 out of 31 (3%) in the control group (P = 0.04) developed relapse. During the 52 weeks follow-up period, 7 out of 10 patients (70%) in the MMF group and 19 out of 31 (61%) in the control group developed relapse (P = 0.72). The median relapse-free interval was 11 and 19 weeks in MMF and control groups, respectively (P = 0.60). No serious side effects were recorded in either group. Limitations: The limitations of the study were low patient numbers receiving MMF and single-center design. Conclusions: Our small cohort of patients treated with MMF reported a higher relapse rate during the induction phase. However, by 12 months of follow-up the relapse rate and relapse-free intervals were similar between both groups. All patients tolerated MMF without significant side effects, and those who relapsed remained steroid-sensitive.


Despite their known side effects steroids remain a standard induction therapy for new onset nephrotic syndrome in children. The aim of this study was to assess whether mycophenolate mofetil (MMF) can be as successful as steroids in maintaining steroid-induced remission. Patients who achieved remission within 2 weeks of steroid treatment had either continued steroids for an additional 10 weeks or switched to MMF. The results of the study showed a higher relapse and infection rate in the MMF group. By 12 months there were no differences in the relapse rate and relapse-free interval between the groups. Larger multicenter studies are underway to demonstrate noninferiority of MMF to steroids in steroid-sensitive nephrotic syndrome.

2.
J Hypertens ; 42(4): 644-649, 2024 Apr 01.
Article in English | MEDLINE | ID: mdl-38230613

ABSTRACT

OBJECTIVE: Although anxiety is known to be associated with elevated blood pressure and hypertension in adults, this has not been studied in children. The aim of this study was to determine the association between anxiety and elevated blood pressures in adolescents. METHODS: Adolescents, aged 12-18 years old, referred to the nephrology clinic were eligible to participate. Elevated blood pressure was defined as either SBP or DBP measurement above the 95th percentile for age, height, and sex. Participants were evaluated for anxiety using the validated Screen for Child Anxiety Related Disorders questionnaire filled independently by the child (SCARED-C) and parent (SCARED-P) evaluating the child. RESULTS: Two hundred adolescents participated in this study. Thirty-one (53%) of SCARED-P-positive participants were found to have elevated blood pressure compared with 27 (19%) of SCARED-P negative, P 0.03. Twenty-five (43%) of SCARED-P positive had elevated DBP compared with 31 (28%) of SCARED-P negative ( P 0.003). In SCARED-P positive, mean DBP (78.4 ±â€Š9.9) was higher compared with SCARED-P negative (74.9 ±â€Š9.2) ( P 0.03). In a subgroup of adolescents (№ 130) not treated with blood pressure medications mean DBP was higher in both SCARED-P (79.0 ±â€Š10.1) and SCARED-C (77.1 ±â€Š10.4) positive groups compared with SCARED-P (73.6 ±â€Š9.3) and SCARED-C (73 ±â€Š8.9) negative, respectively. CONCLUSION: Our study demonstrates an association between anxiety and elevated DBP in adolescent children. Screening adolescents for anxiety should be a part of the routine evaluation of adolescent children.


Subject(s)
Anxiety , Hypertension , Adult , Child , Humans , Adolescent , Cross-Sectional Studies , Blood Pressure , Psychometrics , Anxiety/complications , Hypertension/epidemiology
3.
Pediatr Nephrol ; 39(1): 233-242, 2024 Jan.
Article in English | MEDLINE | ID: mdl-37458800

ABSTRACT

BACKGROUND: Anemia is a common complication of chronic kidney disease (CKD) and oral iron is recommended as initial therapy. However, response to iron therapy in children with non-dialysis CKD has not been formally assessed. METHODS: We reviewed medical records of pediatric patients with stages II-IV CKD followed in two New York metropolitan area medical centers between 2010 and 2020 and identified subjects who received oral iron therapy. Response to therapy at follow-up visits was assessed by improvement of hemoglobin, resolution of anemia by the 2012 KDIGO definition, and changes in iron status. Potential predictors of response were examined using regression analyses (adjusted for age, sex, eGFR, and center). RESULTS: Study criteria were met by 65 children (median age 12 years, 35 males) with a median time between visits of 81 days. Median eGFR was 44 mL/min/1.73 m2, and 40.7% had glomerular CKD etiology. Following iron therapy, hemoglobin improved from 10.2 to 10.8 g/dL (p < 0.001), hematocrit from 31.3 to 32.8% (p < 0.001), serum iron from 49 to 66 mcg/dL (p < 0.001), and transferrin saturation from 16 to 21.4% (p < 0.001). There was no significant change in serum ferritin (55.0 to 44.9 ng/mL). Anemia (defined according to KDIGO) resolved in 29.3% of children. No improvement in hemoglobin/hematocrit was seen in 35% of children, and no transferrin saturation improvement in 26.9%. There was no correlation between changes in hemoglobin and changes in transferrin saturation/serum iron, but there was an inverse correlation between changes in hemoglobin and changes in ferritin. The severity of anemia and alkaline phosphatase at baseline inversely correlated with treatment response. CONCLUSIONS: Anemia was resistant to 3 months of oral iron therapy in ~ 30% of children with CKD. Children with more severe anemia at baseline had better treatment response, calling for additional studies to refine approaches to iron therapy in children with anemia of CKD and to identify additional predictors of treatment response.


Subject(s)
Anemia , Renal Insufficiency, Chronic , Child , Humans , Male , Anemia/drug therapy , Anemia/etiology , Ferritins , Hemoglobins/analysis , Iron , Renal Insufficiency, Chronic/complications , Transferrins , Female
4.
Nat Genet ; 55(7): 1091-1105, 2023 07.
Article in English | MEDLINE | ID: mdl-37337107

ABSTRACT

IgA nephropathy (IgAN) is a progressive form of kidney disease defined by glomerular deposition of IgA. Here we performed a genome-wide association study of 10,146 kidney-biopsy-diagnosed IgAN cases and 28,751 controls across 17 international cohorts. We defined 30 genome-wide significant risk loci explaining 11% of disease risk. A total of 16 loci were new, including TNFSF4/TNFSF18, REL, CD28, PF4V1, LY86, LYN, ANXA3, TNFSF8/TNFSF15, REEP3, ZMIZ1, OVOL1/RELA, ETS1, IGH, IRF8, TNFRSF13B and FCAR. The risk loci were enriched in gene orthologs causing abnormal IgA levels when genetically manipulated in mice. We also observed a positive genetic correlation between IgAN and serum IgA levels. High polygenic score for IgAN was associated with earlier onset of kidney failure. In a comprehensive functional annotation analysis of candidate causal genes, we observed convergence of biological candidates on a common set of inflammatory signaling pathways and cytokine ligand-receptor pairs, prioritizing potential new drug targets.


Subject(s)
Glomerulonephritis, IGA , Animals , Mice , Glomerulonephritis, IGA/drug therapy , Glomerulonephritis, IGA/genetics , Glomerulonephritis, IGA/diagnosis , Genome-Wide Association Study , Immunoglobulin A/genetics
5.
Kidney Med ; 4(10): 100534, 2022 Oct.
Article in English | MEDLINE | ID: mdl-36159165

ABSTRACT

Rationale & Objective: Individuals with IgA vasculitis nephritis (IGAVN) may develop rapidly progressive glomerulonephritis and/or nephrotic-range proteinuria, which are associated with worse prognosis. We report our experience of treatment of children with IGAVN with nephrotic-range proteinuria. Study Design: Case series. Setting & Participants: We retrospectively analyzed all children who presented with IGAVN, cutaneous purpura, and nephrotic-range proteinuria from January 1, 2000 until December 31, 2018. Outcome: We evaluated time required to achieve remission of proteinuria, resolution of hematuria, and glomerular filtration rate (GFR) at 12 months and last follow-up. Results: Twelve patients, 8 boys and 4 girls, mean age 7.5 years (range 4-15) were included in the study. Mean urinary protein to creatinine ratio (UPC) was 12.5 ± 8.7 mg/mg and GFR 90.7 ± 19.1 mL/min/1.73 m2 before initiation of immunosuppression. All patients were treated with steroids and mycophenolate mofetil. Mean UPC declined progressively from 12.5 mg/mg to 4.6, 2.7, 0.3, and 0.2 mg/mg after 1, 3, 6, and 12 months, respectively. All patients achieved remission of proteinuria (UPC <0.3 mg/mg) and normalization of kidney function (GFR 102.2 ± 8.0 mL/min/1.73 m2) at 12 months. Immunosuppression was successfully withdrawn in all patients, and at last follow-up (mean 33.5 months), all patients except one remained in remission. All patients except one that relapsed maintained normal GFR at the last follow-up. Limitations: Retrospective study, single-center experience, no standard immunosuppressive protocol, lack of control group. Conclusions: Remission can be achieved in patients with IGAVN and nephrotic-range proteinuria using mycophenolate mofetil-based immunosuppression. Magnitude of proteinuria is a key laboratory finding that correlates with time to achieve remission. Prolonged follow-up of patients with severe IGAVN is warranted.

6.
Sci Total Environ ; 775: 145109, 2021 Jun 25.
Article in English | MEDLINE | ID: mdl-33631575

ABSTRACT

The long-term time trends of atmospheric pollutants at eight Arctic monitoring stations are reported. The work was conducted under the Arctic Monitoring and Assessment Programme (AMAP) of the Arctic Council. The monitoring stations were: Alert, Canada; Zeppelin, Svalbard; Stórhöfði, Iceland; Pallas, Finland; Andøya, Norway; Villum Research Station, Greenland; Tiksi and Amderma, Russia. Persistent organic pollutants (POPs) such as α- and γ-hexachlorocyclohexane (HCH), polychlorinated biphenyls (PCBs), α-endosulfan, chlordane, dichlorodiphenyltrichloroethane (DDT) and polybrominated diphenyl ethers (PBDEs) showed declining trends in air at all stations. However, hexachlorobenzene (HCB), one of the initial twelve POPs listed in the Stockholm Convention in 2004, showed either increasing or non-changing trends at the stations. Many POPs demonstrated seasonality but the patterns were not consistent among the chemicals and stations. Some chemicals showed winter minimum and summer maximum concentrations at one station but not another, and vice versa. The ratios of chlordane isomers and DDT species showed that they were aged residues. Time trends of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) were showing decreasing concentrations at Alert, Zeppelin and Andøya. The Chemicals of Emerging Arctic Concern (CEAC) were either showing stable or increasing trends. These include methoxychlor, perfluorohexane sulfonic acid (PFHxS), 6:2 fluorotelomer alcohol, and C9-C11 perfluorocarboxylic acids (PFCAs). We have demonstrated the importance of monitoring CEAC before they are being regulated because model calculations to predict their transport mechanisms and fate cannot be made due to the lack of emission inventories. We should maintain long-term monitoring programmes with consistent data quality in order to evaluate the effectiveness of chemical control efforts taken by countries worldwide.

7.
Pediatr Transplant ; 25(5): e13972, 2021 08.
Article in English | MEDLINE | ID: mdl-33502074

ABSTRACT

BACKGROUND: COVID-19 is caused by a novel form of coronavirus known as SARS-CoV-2. Patients can present with a wide variety of symptoms from fever to severe respiratory distress. Immunocompromised patients, including solid organ transplant recipients, may present with atypical symptoms, making the diagnosis of COVID-19 more difficult to make. New reports have been emerging about the management of COVID-19 disease in adult renal transplant recipients. However, very little is known in pediatric renal transplant recipients. METHODS: Here, we describe a case report of four pediatric renal transplant recipients who presented with mild-to-moderate COVID-19 disease. RESULTS: All patients presented with upper respiratory infection symptoms, with one requiring hospitalization for hypoxia. Patients were treated mostly with supportive care. Two of the patients developed AKI which resolved four to eight weeks after illness. All four patients developed COVID IgG antibodies one to two months after becoming infected. CONCLUSION: This case series demonstrates that immunocompromised renal transplant recipients have comparable outcomes compared with immunocompetent children.


Subject(s)
COVID-19/diagnosis , COVID-19/therapy , Kidney Transplantation/methods , SARS-CoV-2 , Adolescent , COVID-19/complications , COVID-19/immunology , Female , Fever , Humans , Hypoxia , Immunocompromised Host , Immunoglobulin G , Male , Renal Insufficiency/complications , Renal Insufficiency/surgery , Transplant Recipients , Young Adult
8.
Arch Dis Child ; 2020 Dec 21.
Article in English | MEDLINE | ID: mdl-33355203

ABSTRACT

BACKGROUND: Children are recognised as at lower risk of severe COVID-19 compared with adults, but the impact of immunosuppression is yet to be determined. This study aims to describe the clinical course of COVID-19 in children with kidney disease taking immunosuppressive medication and to assess disease severity. METHODS: Cross-sectional study hosted by the European Rare Kidney Disease Reference Network and supported by the European, Asian and International paediatric nephrology societies. Anonymised data were submitted online for any child (age <20 years) with COVID-19 taking immunosuppressive medication for a kidney condition. Study recruited for 16 weeks from 15 March 2020 to 05 July 2020. The primary outcome was severity of COVID-19. RESULTS: 113 children were reported in this study from 30 different countries. Median age: 13 years (49% male). Main underlying reasons for immunosuppressive therapy: kidney transplant (47%), nephrotic syndrome (27%), systemic lupus erythematosus (10%). Immunosuppressive medications used include: glucocorticoids (76%), mycophenolate mofetil (MMF) (54%), tacrolimus/ciclosporine A (58%), rituximab/ofatumumab (11%). 78% required no respiratory support during COVID-19 illness, 5% required bi-level positive airway pressure or ventilation. Four children died; all deaths reported were from low-income countries with associated comorbidities. There was no significant difference in severity of COVID-19 based on gender, dialysis status, underlying kidney condition, and type or number of immunosuppressive medications. CONCLUSIONS: This global study shows most children with a kidney disease taking immunosuppressive medication have mild disease with SARS-CoV-2 infection. We therefore suggest that children on immunosuppressive therapy should not be more strictly isolated than children who are not on immunosuppressive therapy.

9.
Front Pediatr ; 7: 155, 2019.
Article in English | MEDLINE | ID: mdl-31069203

ABSTRACT

Background: Most pediatric nephrologists work in academia. Mentor-mentee relationships provide support and guidance for successful research career. Mentorship program implementation is valuable in medical fields for providing research opportunities to young faculty. Methods: The American Society of Pediatric Nephrology (ASPN) established a research mentorship program to (a) assist with matching of appropriate mentor-mentee dyads and (b) establish metrics for desirable mentor-mentee outcomes with two independent components: (1) the grants review workshop, a short-term program providing mentor feedback on grant proposals, and (2) the longitudinal program, establishing long-term mentor-mentee relationships. Regular surveys of both mentors and mentees were reviewed to evaluate and refine the program. Results: Twelve mentees and 17 mentors participated in the grant review workshop and 19 mentees were matched to mentors in the longitudinal program. A review of NIH RePORTER data indicated that since 2014, 13 NIH grants have been awarded. Mentees in the longitudinal program reported that the program helped most with identifying an outside mentor, improving grant research content, and with general career development. Mentors perceived themselves to be most helpful in assisting with overall career plans. Email communications were preferred over phone or face-to-face communications. Mentees endorsed strong interest in staying in touch with their mentors and 100% of mentors expressed their willingness to serve in the future. Conclusion: This mentorship program was initiated and supported by a relatively small medical society and has shown early success in cultivating mentoring relationships for a future generation of clinician-scientists.

10.
Phys Rev Lett ; 111(1): 015002, 2013 Jul 05.
Article in English | MEDLINE | ID: mdl-23863006

ABSTRACT

In a laboratory, a two-dimensional complex (dusty) plasma consists of a low-density ionized gas containing a confined suspension of Yukawa-coupled plastic microspheres. For an initial crystal-like form, we report ideal gas behavior in this strongly coupled system during shock-wave experiments. This evidence supports the use of the ideal gas law as the equation of state for soft crystals such as those formed by dusty plasmas.

11.
Pediatr Transplant ; 17(2): 168-78, 2013 Mar.
Article in English | MEDLINE | ID: mdl-23442101

ABSTRACT

Recipient parenchymal lymphatic cells are crucial for direct and indirect pathways of allorecognition. We proposed that alemtuzumab, being infused several weeks pretransplant could eradicate peripheral lymphatic cells and promote donor-specific tolerance. We present here a single center, retrospective review of 101 consecutive living-donor kidney transplantations to pediatric patients aged from seven month to 18 yr, performed between September 2006 and April 2010. Immunosupression protocol included two 30 mg doses of alemtuzumab: first given 12-29 d prior to transplantation and second at the time of transplantation. Maintenance immunosupression was based on combination of low dose and wide range CNI and mycophenolate. Patients were followed for 3.8 ± 1.4 yr and protocol biopsies were taken one month, one, and three yr post transplant. The Kaplan-Meier graft and patient survival was 96% and 97% for one yr, 89% and 93% for three yr. Biopsy proven acute rejection developed in 26% patients at one yr and in 35% at two yr, no rejections occurred beyond two yr. We conclude that alemtuzumab pretreatment prior to living related donor kidney transplantation allows to reach satisfactory middle-term results in pediatric patients with wide range and low CNI concentrations.


Subject(s)
Antibodies, Monoclonal, Humanized/therapeutic use , Graft Rejection/prevention & control , Immunosuppressive Agents/therapeutic use , Kidney Failure, Chronic/surgery , Kidney Transplantation , Living Donors , Transplantation Conditioning/methods , Adolescent , Alemtuzumab , Child , Child, Preschool , Drug Administration Schedule , Female , Follow-Up Studies , Graft Survival , Humans , Infant , Kaplan-Meier Estimate , Kidney Failure, Chronic/mortality , Kidney Transplantation/mortality , Male , Retrospective Studies , Survival Rate , Treatment Outcome
12.
Transplant Res ; 1(1): 4, 2012 Apr 24.
Article in English | MEDLINE | ID: mdl-23369287

ABSTRACT

BACKGROUND: In the direct pathway, T cells recognize intact donor major histocompatability complexes and allogeneic peptide on the surface of donor antigen presenting cells (APCs). Indirect allorecognition results from the recognition of processed alloantigen by self MHC complexes on self APCs. In this study, we wished to evaluate the relative contribution of different intragraft cells to the alloactivation of nave and memory T cells though the direct and the indirect pathway of allorecognition. METHODS: The processing of membrane fragments from IFN-treated single donor endothelial cells (EC), fibroblasts or renal epithelial cells (RPTEC) was evaluated by DiOC labeling of each cell type and flow cytometry following interaction with PBMC. Direct pathway activation of nave CD45RA+ or memory CD45RO+ CD4+ T cells was evaluated following coculture with IFN-treated and MHC class II-expressing EC, fibroblasts or RPTEC. Indirect pathway activation was assessed using CD45RA+ or CD45RO+ CD4+ T cells cocultured with autologous irradiated APCs in the absence or presence of sonicates derived from IFN-treated allogeneic EC, fibroblasts or RPTEC. Activation of T cells was assessed by [3H]thymidine incorporation and by ELISpot assays. RESULTS: We find that CD14+ APCs readily acquire membrane fragments from fibroblasts and RPTEC, but fail to acquire membrane fragments from intact EC. However, APCs process membranes from EC undergoing apoptosis.There was a notable direct pathway alloproliferative response of CD45RO+ CD4+ T cells to IFN-treated EC, but not to fibroblasts or RPTEC. Also, there was a minimal direct pathway response of CD45RA+ CD4+ T cells to all cell types. In contrast, we found that both CD45RA+ and CD45RO+ CD4+ T cells proliferated following coculture with autologous APCs in the presence of sonicates derived from IFN-treated EC, fibroblasts or RPTEC. By ELISpot, we found that these T cells stimulated via the indirect pathway also produced the cytokines IFN, IL-2, IL-4 and IL-5. CONCLUSIONS: Recipient APCs may readily process membrane fragments from allogeneic intragraft cells, but not from EC unless they are undergoing apoptosis. This processing is sufficient for indirect pathway alloactivation of both CD45RA+ and CD45RO+ CD4+ T cells. Only graft vascular EC mediate direct pathway reactivation of CD4+ T cells.

13.
J Telemed Telecare ; 17(2): 99-104, 2011.
Article in English | MEDLINE | ID: mdl-21163814

ABSTRACT

We developed an educational website for parents of paediatric patients with kidney diseases in Russia. Parents could ask questions regarding their child's illness and submit information, including medical summaries and scanned or electronic images. A US-trained specialist in paediatric nephrology reviewed the information provided and advised about further evaluation or referral, as well as discussing possible treatment plans. In the first nine months, 141 distinct users communicated through the website. Fifty-eight percent of patients were female. An analysis of 70 cases suggested that in 45% there had been overdiagnosis of common paediatric problems, such as urinary tract infection and pyelonephritis. Users completed an anonymous satisfaction survey. The response rate was 84% (n = 59/70). The majority of respondents found the consultation useful (mean = 4.6 on a 5-point scale). The online consultation answered the questions of most respondents, provided useful information and relieved uncertainty regarding a follow-up. The majority of the respondents (>90%) confirmed that they trusted the online consultation and would recommend the technique to other parents. Online consultation for parents can provide reliable information that results in improved parental satisfaction and education. This approach may be useful in improving care and providing patient education in underserved areas in the USA and elsewhere.


Subject(s)
Computer Communication Networks/standards , Consumer Behavior , Internet , Kidney Diseases , Parents/education , Remote Consultation/standards , Child , Female , Humans , Kidney Diseases/diagnosis , Kidney Diseases/therapy , Male , Nephrology/education , Russia
14.
Isr Med Assoc J ; 12(6): 348-52, 2010 Jun.
Article in English | MEDLINE | ID: mdl-20928988

ABSTRACT

BACKGROUND: Peritonitis is a major complication of chronic peritoneal dialysis therapy. It is recommended that each center monitor infection rates in order to define the local microbiological profile and implement an appropriate empiric antibiotic regimen. OBJECTIVES: To analyze the microbiologic profile of peritonitis in our pediatric dialysis unit and identify local predisposing factors. METHODS: In this retrospective study we reviewed the files of children treated with chronic PD during the 10 year period 1997-2007. RESULTS: Eighty peritonitis episodes were recorded in 29 children (20 male, 9 female) aged 0.1-18.5 years (median 11.75) treated with peritoneal dialysis for 6-69 months (median 19) for a total of 578 patient-months. The annual peritonitis rate was 1.66/patient. The main pathogens were coagulase-negative Staphyloccocus (32.5%) and Pseudomonas spp. (16%), which were also cultured in most cases (64-69%) from the exit site during the 3 months preceding peritonitis. No peritonitis occurred in 31% of the patients (median age 12.5 years). All patients less than 5 years old had at least one peritonitis episode. Contaminating conditions (gastrostomy, enuresis, diaper use), found in 44% of the study group, and first infection within 6 months from starting PD were significantly associated with an increased peritonitis rate (P = 0.01, P = 0.009, respectively). Recurrent peritonitis led to a switch to hemodialysis in 18% of patients. There were no deaths. CONCLUSIONS: The risk factors for peritonitis in our study were: first infection within less than 6 months from starting treatment, Pseudomonas exit-site colonization, and contaminating conditions (gastrostomies, diaper use, enuresis). These susceptible subgroups as well as very young age (< 5 years) at starting PD should be especially targeted during training of caregivers and follow-up to prevent later complications.


Subject(s)
Peritoneal Dialysis/adverse effects , Peritonitis/epidemiology , Adolescent , Child , Child, Preschool , Chronic Disease , Female , Hospital Units , Humans , Infant , Israel , Male , Peritonitis/microbiology , Retrospective Studies , Risk Factors
15.
Article in English | MEDLINE | ID: mdl-19163264

ABSTRACT

A 3D weighting scheme have been proposed previously to reconstruct images at both helical and axial scans in stat-of-the-art volumetric CT scanners for diagnostic imaging. Such a 3D weighting can be implemented in the manner of either ray-driven or pixel-drive, depending on the available computation resources. An experimental study is conducted in this paper to evaluate the difference between the ray-driven and pixel-driven implementations of the 3D weighting from the perspective of image quality, while their computational complexity is analyzed theoretically. Computer simulated data and several phantoms, such as the helical body phantom and humanoid chest phantom, are employed in the experimental study, showing that both the ray-driven and pixel-driven 3D weighting provides superior image quality for diagnostic imaging in clinical applications. With the availability of image reconstruction engine at increasing computational power, it is believed that the pixel-driven 3D weighting will be dominantly employed in state-of-the-art volumetric CT scanners over clinical applications.


Subject(s)
Image Processing, Computer-Assisted/methods , Radiography, Thoracic/methods , Tomography, X-Ray Computed/methods , Algorithms , Computer Graphics , Computer Simulation , Humans , Imaging, Three-Dimensional , Models, Statistical , Models, Theoretical , Phantoms, Imaging , Radiographic Image Enhancement , Reproducibility of Results , Scattering, Radiation , Tomography, X-Ray Computed/instrumentation
16.
Phys Med Biol ; 51(4): 855-74, 2006 Feb 21.
Article in English | MEDLINE | ID: mdl-16467583

ABSTRACT

Based on the structure of the original helical FDK algorithm, a three-dimensional (3D)-weighted cone beam filtered backprojection (CB-FBP) algorithm is proposed for image reconstruction in volumetric CT under helical source trajectory. In addition to its dependence on view and fan angles, the 3D weighting utilizes the cone angle dependency of a ray to improve reconstruction accuracy. The 3D weighting is ray-dependent and the underlying mechanism is to give a favourable weight to the ray with the smaller cone angle out of a pair of conjugate rays but an unfavourable weight to the ray with the larger cone angle out of the conjugate ray pair. The proposed 3D-weighted helical CB-FBP reconstruction algorithm is implemented in the cone-parallel geometry that can improve noise uniformity and image generation speed significantly. Under the cone-parallel geometry, the filtering is naturally carried out along the tangential direction of the helical source trajectory. By exploring the 3D weighting's dependence on cone angle, the proposed helical 3D-weighted CB-FBP reconstruction algorithm can provide significantly improved reconstruction accuracy at moderate cone angle and high helical pitches. The 3D-weighted CB-FBP algorithm is experimentally evaluated by computer-simulated phantoms and phantoms scanned by a diagnostic volumetric CT system with a detector dimension of 64 x 0.625 mm over various helical pitches. The computer simulation study shows that the 3D weighting enables the proposed algorithm to reach reconstruction accuracy comparable to that of exact CB reconstruction algorithms, such as the Katsevich algorithm, under a moderate cone angle (4 degrees) and various helical pitches. Meanwhile, the experimental evaluation using the phantoms scanned by a volumetric CT system shows that the spatial resolution along the z-direction and noise characteristics of the proposed 3D-weighted helical CB-FBP reconstruction algorithm are maintained very well in comparison to the FDK-type algorithms. Moreover, the experimental evaluation by clinical data verifies that the proposed 3D-weighted CB-FBP algorithm for image reconstruction in volumetric CT under helical source trajectory meets the challenges posed by diagnostic applications of volumetric CT imaging.


Subject(s)
Algorithms , Imaging, Three-Dimensional/methods , Radiographic Image Enhancement/methods , Radiographic Image Interpretation, Computer-Assisted/methods , Tomography, Spiral Computed/methods , Humans , Reproducibility of Results , Sensitivity and Specificity
17.
Curr Opin Pediatr ; 14(2): 205-10, 2002 Apr.
Article in English | MEDLINE | ID: mdl-11981291

ABSTRACT

In this review, we discuss current and future issues in the management of pediatric renal transplant recipients, including the optimization of long-term graft function and the minimization of complications caused by immunosuppression. Long-term management involves not only the monitoring of graft function but also the identification of patients at risk for the development of complications. The identification of patients with immunoreactive or immunoregulatory responses can be performed molecular monitoring of the immune response. Also, the use of frequent surveillance kidney biopsies, surrogate markers of chronic rejection, and glomerular filtration rate will be a part of future management. Identifying high-risk patients enables the physician to optimize immunosuppression to limit acute rejection. Short-and long-term management of pediatric transplant patients also includes adequate monitoring of growth and the monitoring for post-transplant lymphoproliferative disease. Ongoing clinical trials are underway that focus on these novel approaches in caring for pediatric transplant recipients.


Subject(s)
Graft Rejection/etiology , Immunosuppressive Agents/administration & dosage , Kidney Transplantation/adverse effects , Kidney Transplantation/rehabilitation , Mycophenolic Acid/analogs & derivatives , Calcineurin Inhibitors , Child , Drug Therapy, Combination , Glomerular Filtration Rate/drug effects , Graft Rejection/drug therapy , Human Growth Hormone/therapeutic use , Humans , Mycophenolic Acid/administration & dosage , Receptors, Interleukin-2/therapeutic use , Risk Factors , Sirolimus/administration & dosage
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