GPU-accelerated 3D Bayesian image reconstruction from Compton scattered data

This paper describes the development of fast Bayesian reconstruction methods for Compton cameras using commodity graphics hardware. For fast iterative reconstruction, not only is it important to increase the convergence rate, but also it is equally important to accelerate the computation of time-consuming and repeated operations, such as projection and backprojection. Since the size of the system matrix for a typical Compton camera is intractably large, it is impractical to use a conventional caching scheme that stores the pre-calculated elements of a system matrix and uses them for the calculation of projection and backprojection. In this paper we propose GPU (graphics processing unit)-accelerated methods that can rapidly perform conical projection and backprojection on the fly. Since the conventional ray-based backprojection method is inefficient for parallel computing on GPUs, we develop voxel-based conical backprojection methods using two different approximation schemes. In the first scheme, we approximate the intersecting chord length of the ray passing through a voxel by the perpendicular distance from the center to the ray. In the second scheme, each voxel is regarded as a dimensionless point rather than a cube so that the backprojection can be performed without the need for calculating intersecting chord lengths or their approximations. Our simulation studies show that the GPU-based method dramatically improves the computational speed with only minor loss of accuracy in reconstruction. With the development of high-resolution detectors, the difference in the reconstruction accuracy between the GPU-based method and the CPU-based method will eventually be negligible.     

Risk factors for adjacent segment disease after lumbar fusion

The incidence of adjacent segment problems after lumbar fusion has been found to vary, and risk factors for these problems have not been precisely verified, especially based on structural changes determined by magnetic resonance imaging. The purpose of this retrospective clinical study was to describe the incidence and clinical features of adjacent segment disease (ASD) after lumbar fusion and to determine its risk factors. We assessed the incidence of ASD in patients who underwent lumbar or lumbosacral fusions for degenerative conditions between August 1995 and March 2006 with at least a 1-year follow-up. Patients less than 35 years of age at the index spinal fusion, patients with uninstrumented fusion, and patients who had not achieved successful union were excluded. Of the 1069 patients who underwent fusions, 28 (2.62%) needed secondary operations because of ASD and were included in this study. In order to identify the risk factors, we matched a disease group and a control group. The disease group consisted of 26 of the 28 patients with ASD, excluding the 2 patients for whom we did not have initial MRI data. Each patient in the disease group was matched by age, sex, fusion level and follow-up period with a control patient. The assumed risk factors included disc and facet degeneration, instability, listhesis, rotational deformity, and disc wedging. The mean age of the 28 patients with ASD requiring surgical treatment was 58.4 years, which did not differ significantly from that of the population in which ASD did not develop (58.2 years, p = 0.894). Of the 21 patients who underwent floating fusion, only 1 developed distal ASD. Facet degeneration was a significant risk factor (p < 0.01) on logistic regression analysis. The incidence of distal ASD was much lower than that of proximal ASD. Pre-existing facet degeneration may be associated with a high risk of adjacent segment problems following lumbar fusion procedures.     

Differential Methylation Pattern of ID4, SFRP1, and SHP1 between Acute Myeloid Leukemia and Chronic Myeloid Leukemia

To gain insight into the differential mechanism of gene promoter hypermethylation in acute and chronic leukemia, we identified the methylation status on one part of 5''CpG rich region of 8 genes, DAB2IP, DLC-1, H-cadherin, ID4, Integrin α4, RUNX3, SFRP1, and SHP1 in bone marrows from acute myeloid leukemia (AML) and chronic myeloid leukemia (CML) patients. Also, we compared the methylation status of genes in AML and CML using methylation-specific PCR (MSP). The frequencies of DNA methylation of ID4, SFRP1, and SHP1 were higher in AML patients compared to those in CML patients. In contrast, no statistical difference between AML and CML was detected for other genes such as DLC-1, DAB2IP, H-cadherin, Integrin α4, and RUNX3. Taken together, these results suggest that these methylation-controlled genes may have different roles in AML and CML, and thus, may act as a biological marker of AML.     

Clinicopathological features of syphilitic gastritis in Korean patients

Syphilitic gastritis is difficult to diagnose without a history of syphilis, because endoscopic and microscopic findings can simulate gastric cancer or lymphoma. Herein are reported two cases of syphilitic gastritis and analysis of the clinicopathological characteristics of 11 cases in Korean subjects, including nine previously reported ones. The two present patients were 25‐ and 32‐year‐old men with epigastric pain. The gastroduodenoscopy features were similar: multiple erosive or ulcerative lesions in whole gastric mucosa. Microscopically, gastric mucosa contained severe chronic active gastritis involving submucosa with crypt abscesses, venulitis and granulomas, suggesting unusual infectious gastritis. Numerous spirochetes were identified on silver staining, and serological tests for syphilis were reactive in both patients. They were treated with benzathin penicillin, and follow‐up gastric biopsy specimens indicated non‐specific chronic gastritis without evidence of syphilis. Of the 11 Korean patients with syphilitic gastritis, six were female and five were male (mean age, 31.7 years). The most common symptom was epigastric pain and all patients had diffuse erosive, ulcerative or infiltrative lesions on gastroduodenoscopy. Syphilitic gastritis should be considered in young patients with epigastric pain who have diffuse gastric involvement such as erosion or shallow ulcer on endoscopy and unusually extensive chronic active gastritis on microscopy, even if the history of syphilis is not clear.     

Endovascular treatment for transplant renal artery stenosis: A retrospective cohort study

Transplant renal artery stenosis (TRAS) is the most common (1%–23%) vascular complication following kidney transplantation. The aim of this study was to review our experience with an endovascular approach to treat TRAS.We retrospectively reviewed kidney transplant recipients who underwent percutaneous transluminal angioplasty (PTA) due to TRAS in our institute from January 2009 to December 2015. We analyzed the patient''s baseline characteristics, postoperative renal function, blood pressure evolution, and the number of pre- and post-procedure antihypertensive drugs.A total of 21 patients (15 men, 6 women) were treated with the endovascular technique. The predominant presentation was graft dysfunction (76.2%). Stenosis or hemodynamic kinking was located at the anastomosis in 7 (33.3%) patients, proximal to the anastomosis in 13 (61.9%) patients, and distal the anastomosis in 1 (4.8%) patient. PTA without stent placement was performed in 7 patients (33.3%), and PTA with stent placement was performed in 14 patients (67.7%). Serum creatinine levels demonstrated no difference between the pre-procedure level and that on discharge day (1.61 mg/dl [0.47–3.29 mg/dl] vs 1.46 mg/dl [0.47–3.08 mg/dl]; P = .33). The glomerular filtration rate also showed no difference between the pre-procedure value and that on discharge day (53.6 ml/min [22.4–145.7 ml/min] vs 57.0 ml/min [17.56 –145 ml/min]; P = .084). Systolic blood pressure and diastolic blood pressure (DBP) varied from 137 mm Hg (120–160 mm Hg) and 84 mm Hg (70–100 mm Hg) pre-procedure to 129 mm Hg (90–150 mm Hg) and 79 mm Hg (60–90 mm Hg) at discharge, respectively (P = .124 and P = .07). The number of antihypertensive medications significantly decreased from 1.5 (0–6) pre-procedure to 0.5 (0–2) at discharge (P = .023). In our study, there were no technical failures, procedure-related complications or deaths. During the follow-up period, the free-from-reintervention rate was 100%, and graft failures occurred in 2 patients (9.5%) due to rejection.Endovascular procedures for TRAS show a high technical success rate with a low complication rate and a low reintervention rate. PTA showed a trend toward a positive impact on lowering serum creatinine, systolic blood pressure, and diastolic blood pressure and improving estimated glomerular filtration rate, and the number of antihypertensive medications could be significantly reduced after this procedure.     

壳聚糖磷脂酰胆碱防治MCI的ERP早成分研究

目的 观察壳聚糖磷脂酰胆碱对轻度认知功能障碍(MCI)患者数物感知觉的影响.方法 采用纵向研究配伍组设计方案,根据MCI的诊断标准选取20例MCI患者,采用事件相关电位(ERP)的分析技术,通过数物感知觉对照实验,分析其ERP早成分.结果 用药后MCI患者额中央区的N1,P2波幅增大(P<0.05)以及颞枕区的N170波幅增大(P<0.05).结论 壳聚糖磷脂酰胆碱可以改善MCI患者早期感知觉.