Dose Calculation Accuracy of the Monte Carlo Algorithm for CyberKnife Compared with Other Commercially Available Dose Calculation Algorithms

Monte Carlo dose calculation algorithms have the potential for greater accuracy than traditional model-based algorithms. This enhanced accuracy is particularly evident in regions of lateral scatter disequilibrium, which can develop during treatments incorporating small field sizes and low-density tissue. A heterogeneous slab phantom was used to evaluate the accuracy of several commercially available dose calculation algorithms, including Monte Carlo dose calculation for CyberKnife, Analytical Anisotropic Algorithm and Pencil Beam convolution for the Eclipse planning system, and convolution-superposition for the Xio planning system. The phantom accommodated slabs of varying density; comparisons between planned and measured dose distributions were accomplished with radiochromic film. The Monte Carlo algorithm provided the most accurate comparison between planned and measured dose distributions. In each phantom irradiation, the Monte Carlo predictions resulted in gamma analysis comparisons >97%, using acceptance criteria of 3% dose and 3-mm distance to agreement. In general, the gamma analysis comparisons for the other algorithms were <95%. The Monte Carlo dose calculation algorithm for CyberKnife provides more accurate dose distribution calculations in regions of lateral electron disequilibrium than commercially available model-based algorithms. This is primarily because of the ability of Monte Carlo algorithms to implicitly account for tissue heterogeneities, density scaling functions; and/or effective depth correction factors are not required.     

A variant of nephrogenic diabetes insipidus: V2 receptor abnormality restricted to the kidney

In congenital nephrogenic diabetes insipidus (NDI) blunted responses of plasma factor VIII, von Willebrand factor, and plasminogen activator to the synthetic V₂ analogue 1-desamino-8-d-arginine vasopressin (DDAVP) have been reported. In addition, vasodilatory responses to DDAVP appear to be absent in NDI. We describe a boy, who presented shortly after birth with the typical features of NDI, but who showed normal coagulation, fibrinolytic and vasodilatory responses to DDAVP. We conclude that in this patient the defect is confined to the kidney, while in other NDI patients there may be a general V₂ receptor abnormality. These findings point to heterogeneity in NDI.     

Reduction in the minimum candidate interval in the dominant-intermediate form of Charcot-Marie-Tooth neuropathy to D19S586 to D19S432

As part of an on-going genomic screen of unlinked Charcot-Marie-Tooth disease type 2 (CMT2) families, we identified 11 regions in the genome with lod scores ≥1.0. One of these regions was near the recently identified CMTDI1 locus on 19q. We show evidence of linkage of DUK 1118 to this region and our data reduce the minimum candidate interval for CMTDI1 to the 9-cM interval spanned by D19S586 and D19S432.We also demonstrate that five additional CMT2 families are unlinked to 19q markers, providing further evidence of CMT2 heterogeneity. Electronic Publication     

The charge-heterogeneity of human fibrinogen as investigated by 2D electrophoresis

The charge-heterogeneity of human plasma fibrinogen subunit chains was characterized by two-dimensional electrophoresis (2DE). Western blotting with antibodies specific for the γ-chain demonstrated that the γ-chains focus at varying isoelectric points (pI). This microheterogeneity was also observed in fibrinogen secreted from hepatocytic cells and in recombinant fibrinogen expressed in Chinese hamster ovary (CHO) cells. Further, covalent γγ-dimerization by FXIIIa was not influenced by the charge-heterogeneity, and removal of the carbohydrate did not reduce the number of γ-chain pI variants. These observations suggest that the microheterogeneity of the γ-chain is a multifactorial phenomenon that is not due to physiologic modification of the glycoprotein in circulation.     

弹性仿生义齿在牙列缺失中的临床应用

目的探讨弹性仿生义齿在牙列缺失的矫治中的意义。方法印模、灌型、排牙后装盒、烫蜡,使之加温287℃5 min,放入材料持续11 min后冷却,打磨抛光即可。结果经过1年观察成功77例,失败3例。结论严格操作,弹性仿生义齿对矫治牙列缺失有较多优点。     

卵巢恶性肿瘤DNA倍体及其异质性的临床预后意义

目的 探讨卵巢恶性肿瘤DNA倍体、异倍体和异质性与临床预后的关系。方法 应用FCM流式细胞术，对20例卵巢恶性肿瘤、20例卵巢良性肿瘤、10例正常卵巢组织进行了DNA倍体、异倍体和异质性的检测，并分析其与临床预后的关系。结果 卵巢恶性肿瘤DNA异倍体、异质性的患者术后肿瘤复发率、死亡率明显高于卵巢恶性肿瘤DNA二倍体、同质性患者（P＜0．01）。卵巢恶性肿瘤DNA二倍体、同质性患者术后无瘤生存期明显长于卵巢恶性肿瘤DNA异倍体、异质性的患者（P＜0．01）。结论 卵巢恶性肿瘤DNA倍体、异倍体和异质性的测定是判断患者预后的良好指标。     

Not Infrequent K-ras Mutations in Depressed-type Early Colorectal Carcinomas Larger than 10 mm

The aim of this study was to elucidate whether K- ras (codons 12 and 13) mutations occur in depressed-type early colorectal carcinomas (DECas) larger than 10 mm in size. Thirty-four cases of DECas including 27 larger than 10 mm were examined for K- ras mutations by means of microdis-section, PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism), and direct sequencing. Although K- ras mutation was infrequent (1/7, 14%) in small (less than 10 mm) DECas, 16/27 (59%) and 17/27 (63%) of DECas larger than 10 mm revealed codon 12, or either codon 12 or 13 mutations, respectively. None of the evaluated pathological factors except size showed a correlation with K- ras mutation. These data indicate that although K- ras mutation could not be involved in the early stage of the progression of DECas, it might play a role at a later stage when the tumor size is over 10 mm.     

Dynamic cell cycle kinetics in vitro and in vivo in myelodysplastic syndromes with special reference to the influence of hematopoietic growth factors

We have investigated the effect of HGF in vivo and in vitro in MDS using a recently developed FCM assay involving the simultaneous measurement of cell surface antigens, DNA content, and BrdUrd or IodUrd incorporation. This allows for the determination of the dynamic cell kinetic parameters: LI, T_s, and T_pot and we observed that in vitro HGF stimulation resulted in a significant decrease in mean T_pot values from 6.6 to 3.5 days. Importantly, we demonstrated that in vivo GM-CSF administration to patients with RAEB resulted in a shortening of T_pot within the 2 first weeks of GM-CSF treatment.     

模拟缺血缺氧对左心室心肌细胞钠电流跨壁异质性的影响

目的 :　研究左心室心肌细胞快钠通道的跨壁异质性及模拟缺血对其的影响。　方法 :采用全细胞膜片钳记录技术直接记录左心室三层心肌细胞的快钠通道电流 (INa) ,并观察模拟缺血缺氧对心肌细胞INa跨壁异质性的影响。　结果 :左心室三层心肌细胞的钠电流特性存在异质性 ,表现为中层 (M )细胞的电流密度 电压关系(I V)曲线最低 ,M细胞的峰值INa是心内膜层 (Endo)和心外膜层 (Epi)的 2倍多 ;M细胞的INa失活最快。模拟缺血后 ,三层心肌细胞的INaI V曲线呈时间依赖性下移 ,M细胞的变化最显著 ;INa稳态失活曲线呈时间依赖性左移 ,以Epi变化最显著 ;模拟缺血 30min时Endo的恢复明显慢于M和Epi。　 结论 :左心室心肌细胞的INa存在跨壁异质性 ;模拟缺血缺氧对INa的跨壁异质性有明显影响。     

Effect of a hypergravity environment on cortical bone elasticity in rats

There is considerable interest in determining whether hypergravity can be used as a countermeasure for microgravity-induced bone loss. This study was conducted on 20 immature male rats in order to investigate possible elastic adaptations of cortical bone in rapidly growing rats exposed to chronic hypergravity. Ten rats were continuously centrifuged for 14 days at twice gravitational acceleration (2G) on a 12.75 foot radius centrifuge and 10 rats concurrently acted as stationary controls. The effect of hypergravity on the elastic characteristics of cortical bone was quantified via ultrasonic wave propagation. Propagation velocities of longitudinal and shear waves were measured through cubic cortical specimens from the posterior femoral diaphyses. Density was measured with an Archimedes' technique. The orthotropic elastic properties were calculated and used to compare the difference between groups. Results showed an average increase in both the Young's moduli (E_ii, + 2.2%) and shear moduli (G_ij, + 4.3%) with a statistically significant increase only in G₁₂ (+15.7%, P= 0.046). The ratio of transverse to axial strain (Poisson's ratio, ν_ij) demonstrated statistically significant changes in ν₁₂, ν₂₁, ν₁₃, and ν₃₁ (P < 0.05). These findings suggest that although slight elastic changes were incurred via a hypergravity environment, the treatment level or duration in this study do not dramatically perturb the normal elastic behavior of cortical bone and that dramatic biomechanical differences noted in previous studies were due more to structural changes than material elasticity changes. Hypergravity applied post facto to a microgravity environment would offer further illucidation of this method as treatment for a degenerative spaceflight experience. Received: 12 August 1995 / Accepted: 23 February 1996