Intensity modulated proton therapy treatment planning using single-field optimization: the impact of monitor unit constraints on plan quality

PURPOSE

To investigate the effect of monitor unit (MU) constraints on the dose distribution created by intensity modulated proton therapy (IMPT) treatment planning using single-field optimization (SFO).

METHODS

Ninety-four energies between 72.5 and 221.8 MeV are available for scanning beam IMPT delivery at our institution. The minimum and maximum MUs for delivering each pencil beam (spot) are 0.005 and 0.04, respectively. These MU constraints are not considered during optimization by the treatment planning system; spots are converted to deliverable MUs during postprocessing. Treatment plans for delivering uniform doses to rectangular volumes with and without MU constraints were generated for different target doses, spot spacings, spread-out Bragg peak (SOBP) widths, and ranges in a homogeneous phantom. Four prostate cancer patients were planned with and without MU constraints using different spot spacings. Rounding errors were analyzed using an in-house software tool.

RESULTS

From the phantom study, the authors have found that both the number of spots that have rounding errors and the magnitude of the distortion of the dose distribution from the ideally optimized distribution increases as the field dose, spot spacing, and range decrease and as the SOBP width increases. From our study of patient plans, it is clear that as the spot spacing decreases the rounding error increases, and the dose coverage of the target volume becomes unacceptable for very small spot spacings.

CONCLUSIONS

Constraints on deliverable MU for each spot could create a significant distortion from the ideally optimized dose distributions for IMPT fields using SFO. To eliminate this problem, the treatment planning system should incorporate the MU constraints in the optimization process and the delivery system should reliably delivery smaller minimum MUs.

Indications of proton-dominated cosmic-ray composition above 1.6 EeV

We report studies of ultrahigh-energy cosmic-ray composition via analysis of depth of air shower maximum (X(max)), for air shower events collected by the High-Resolution Fly's Eye (HiRes) observatory. The HiRes data are consistent with a constant elongation rate d<X(max)>/d[log(E)] of 47.9+/-6.0(stat)+/-3.2(syst) g/cm2/decade for energies between 1.6 and 63 EeV, and are consistent with a predominantly protonic composition of cosmic rays when interpreted via the QGSJET01 and QGSJET-II high-energy hadronic interaction models. These measurements constrain models in which the galactic-to-extragalactic transition is the cause of the energy spectrum ankle at 4x10(18) eV.

Clinical analysis of systemic lupus erythematosus with gastrointestinal manifestations

Our objective was to analyse the clinical characteristics of systemic lupus erythematosus (SLE) patients with gastrointestinal manifestations. Medical charts of 177 hospitalized SLE patients were systematically reviewed, including demographic data, clinical features, laboratory findings, and treatments, as well as outcomes. Thirty-nine cases (22.0%) had SLE-related gastrointestinal manifestations, and in 12 cases (30.8%), gastrointestinal manifestations occurred as the initial symptoms. Twenty-five cases (64.1%) had abdominal pain, 22 cases (56.4%) had nausea and vomiting, 12 cases (30.8%) had diarrhea, and gastrointestinal hemorrhage occurred in three cases (7.7%). Protein losing enteropathy and intestinal pseudo-obstruction were the most common identifiable gastrointestinal complications, though other reasons such as superior mesenteric venous thrombosis, pancreatitis, peritonitis, and liver impairment could also occur in SLE. The incidences of Raynaud's phenomenon and pyeloureterectasis were significantly higher in patients with gastrointestinal complications than those without (p < 0.05). Multivariable analysis indicated Raynaud's phenomenon, decreased C3, CH50, and anti-neutrophil cytoplasmic antibody positivity were independent predictors of gastrointestinal involvements (p < 0.05). Gastrointestinal complications are common, diverse, and could be the initial and major manifestations of lupus. SLE patients who had Raynaud's phenomenon, hypocomplementemia and positive anti-neutrophil cytoplasmic antibody were at increasing risk of developing gastrointestinal complication.

Positioning of quantum dots on metallic nanostructures

The capability to position individual emitters, such as quantum dots, near metallic nanostructures is highly desirable for constructing active optical devices that can manipulate light at the single photon level. The emergence of the field of plasmonics as a means to confine light now introduces a need for high precision and reliability in positioning any source of emission, which has thus far been elusive. Placing an emission source within the influence of plasmonic structures now requires accuracy approaching molecular length scales. In this paper we report the ability to reliably position nanoscale functional objects, specifically quantum dots, with sub-100-nm accuracy, which is several times smaller than the diffraction limit of a quantum dot's emission light. Electron beam lithography-defined masks on metallic surfaces and a series of surface chemical functionalization processes allow the programmed assembly of DNA-linked colloidal quantum dots. The quantum dots are successfully functionalized to areas as small as (100 nm)(2) using the specific binding of thiolated DNA to Au/Ag, and exploiting the streptavidin-biotin interaction. An analysis of the reproducibility of the process for various pattern sizes shows that this technique is potentially scalable to the single quantum dot level with 50 nm accuracy accompanied by a moderate reduction in yield.

Search for the Higgs boson using neural networks in events with missing energy and b-quark jets in pp collisions at square root(s) = 1.96 TeV

We report on a search for the standard model Higgs boson produced in association with a W or Z boson in pp collisions at square root(s)=1.96 TeV recorded by the CDF II experiment at the Tevatron in a data sample corresponding to an integrated luminosity of 2.1 fb(-1). We consider events which have no identified charged leptons, an imbalance in transverse momentum, and two or three jets where at least one jet is consistent with originating from the decay of a b hadron. We find good agreement between data and background predictions. We place 95% confidence level upper limits on the production cross section for several Higgs boson masses ranging from 110 GeV/c(2) to 150 GeV/c(2). For a mass of 115 GeV/c(2) the observed (expected) limit is 6.9 (5.6) times the standard model prediction.

First measurement of the b-jet cross section in events with a W boson in pp collisions at square root(s) = 1.96 TeV

The cross section for jets from b quarks produced with a W boson has been measured in pp collision data from 1.9 fb(-1) of integrated luminosity recorded by the CDF II detector at the Tevatron. The W+b-jets process poses a significant background in measurements of top quark production and prominent searches for the Higgs boson. We measure a b-jet cross section of 2.74+/-0.27(stat)+/-0.42(syst) pb in association with a single flavor of leptonic W boson decay over a limited kinematic phase space. This measured result cannot be accommodated in several available theoretical predictions.

Targeted melanoma imaging and therapy with radiolabeled alpha-melanocyte stimulating hormone peptide analogues

Radiolabeled alpha-melanocyte stimulating hormone (a-MSH) analogues have been used to define the expression, affinity and function of the melanocortin-1 receptor (MC1-R). The MC1-R is one of a family of five G-protein linker receptors, which is primarily involved in regulation of skin pigmentation. Over-expression of the MC1-R on melanoma tumor cells has made it an attractive target for the development of a-MSH peptide based imaging and therapeutic agents. Initially, the native a-MSH peptide was radiolabeled directly, but it suffered from low specific activity and poor stability. The addition of non-natural amino acids yielded a-MSH analogues with greater MC-1R affinity and stability. Furthermore, peptide cyclization via disulfide and lactam bond formation as well as site-specific metal coordination resulted in additional gains in receptor affinity and peptide stability in vitro and in vivo. Radiochemical stability of the a-MSH analogues was improved through the conjugation of metal chelators to the peptide's N-terminus or lysine residues for radionuclide coordination. In vitro cell binding studies demonstrated that the radiolabeled a-MSH analogues had low to subnanomolar affinities for the MC1-R. Biodistribution and imaging studies in the B16 mouse melanoma modeled showed rapid tumor uptake of the radiolabeled peptides, with the cyclic peptides demonstrating prolonged tumor retention. Cyclic a-MSH analogues labeled with beta and alpha emitting radionuclides demonstrated melanoma therapeutic efficacy in the B16 melanoma mouse model. Strong pre-clinical imaging and therapy data highlight the clinical potential use of radiolabeled a-MSH peptides for melanoma imaging and treatment of disseminated disease.

Translocation of protein kinase C isoforms is involved in propofol-induced endothelial nitric oxide synthase activation

BACKGROUND

Previous studies have indicated that protein kinase C (PKC) may enhance endothelial nitric oxide synthase (eNOS) activation, although the detailed mechanism(s) remains unclear. In this study, we investigated the roles of PKC isoforms in regulating propofol-induced eNOS activation in human umbilical vein endothelial cells (HUVECs).

METHODS

We applied western blot (WB) analysis to investigate the effects of propofol on Ser(1177) phosphorylation-dependent eNOS activation in HUVECs. Nitrite (NO(2)(-)) accumulation was measured using the Griess assay. The phosphatidylinositol 3-kinase/Akt (PI3K/Akt) pathway was examined by WB assay. Propofol-induced translocation of individual PKC isoforms in subcellular fractions in HUVECs was analysed using WB assay.

RESULTS

In HUVECs, protocol treatment (1-100 microM) for 10 min induced a concentration-dependent increase in phosphorylation of eNOS at Ser(1177). The NO production was also increased accordingly. PKC inhibitors, bisindolylmaleimide I (0.1-1 microM), and staurosporine (20 and 100 nM), effectively blocked propofol-induced eNOS activation and NO production. Further analyses in fractionated endothelial lysate showed that short-term propofol treatment (50 microM) led to translocation of PKC-alpha, PKC-delta, PKC-zeta, PKC-eta, and PKC-epsilon from cytosolic to membrane fractions, which could also be inhibited by both PKC inhibitors. These data revealed that the differential redistribution of these isozymes is indispensable for propofol-induced eNOS activation. In addition, Akt was not phosphorylated in response to propofol at Ser(473) or Thr(308).

CONCLUSIONS

Propofol induces the Ser(1177) phosphorylation-dependent eNOS activation through the drug-stimulated translocation of PKC isoforms to distinct intracellular sites in HUVECs, which is independent of PI3K/Akt-independent pathway.

Decreased level of 5-methyltetrahydrofolate: a potential biomarker for pre-symptomatic amyotrophic lateral sclerosis

BACKGROUND

Several studies have reported that homocysteine (Hcy) is associated with amyotrophic lateral sclerosis (ALS), a neurodegenerative disease without special biomarkers for early diagnosis. Here, we examined the levels of Hcy, folic acid and its metabolic molecule 5-methyltetrahydrofolate (5-MTHF) in SOD1(G93A) transgenic mouse model of ALS in an attempt to determine whether the change in those molecules can be used as potential biomarkers for the disease.

METHODS

According to the disease progression, SOD1(G93A) transgenic mice were divided into early stage group (30d); pre-symptom group (60d); symptom group (90d) and terminal stage group (120d). LC-MS/MS was used to measure the level of Hcy, folic acid and 5-MTHF in the plasma, spinal cord and cortex of the ALS transgenic SOD1(G93A) mice at different disease stages. Nissl staining was used to detect the motor neurons survival in the anterior horn of the spinal cord of the SOD1(G93A) mice.

RESULTS

In this study, we demonstrated that the level of 5-MTHF is significantly decreased in the plasma, spinal cord and cortex at the early stages of pre-symptomatic ALS transgenic SOD1(G93A) mice while folic acid is decreased at the middle to late stages of the disease. Furthermore, we found that the level of Hcy is markedly elevated after the motor symptoms appeared in the ALS mice.

CONCLUSION

Our study suggests that decreased 5-MTHF level may be a potential biomarker for the early stage of the disease in the ALS mice, which may warrant further validating study of 5-MTHF level in ALS patients.

Novel and recurrent mutations in the filaggrin gene in Chinese patients with ichthyosis vulgaris

BACKGROUND

Ichthyosis vulgaris (IV) is a common inherited skin disorder, and the filament aggregating protein (filaggrin) is a key protein involved in skin barrier function. Mutations in the filaggrin gene (FLG) have recently been identified as the cause of IV. However, there have been no reports of FLG mutations in mainland Chinese families with IV.

OBJECTIVES

To identify FLG mutations in Chinese patients with IV.

METHODS

Eleven unrelated Chinese families with IV were examined for FLG mutations with denaturing high-performance liquid chromatography prescreening and sequencing. SNaPShot was employed to obtain a high-throughput screening for the identified mutations.

RESULTS

Three mutations - one novel mutation (Q1256X) and two known mutations (3321delA and E2422X) - were identified in these families. The novel mutation, Q1256X, found in a Chinese family with IV, was located in filaggrin repeat 3. Mutation 3321delA, previously found in Japanese patients, was present in eight Chinese families with IV. Mutation E2422X, previously found in a Dutch patient of Chinese origin, was present in two Chinese families with IV. Neither of the null mutations, Q1256X and E2422X, were found in 100 unrelated control cases from the Chinese population; however, the mutation ratio for 3321delA was 3% in these controls.

CONCLUSIONS

Our study suggests that each population may have a unique and prevalent set of FLG mutations.

Search for technicolor particles produced in association with a W Boson at CDF

We present a search for the technicolor particles rho{T} and pi_{T} in the process pp-->rho{T}-->Wpi{T} at a center of mass energy of sqrt[s]=1.96 TeV. The search uses a data sample corresponding to approximately 1.9 fb{-1} of integrated luminosity accumulated by the CDF II detector at the Fermilab Tevatron. The event signature we consider is W-->lnu and pi{T}-->bb, bc or bu depending on the pi{T} charge. We select events with a single high-p{T} electron or muon, large missing transverse energy, and two jets. Jets corresponding to bottom quarks are identified with multiple b-tagging algorithms. The observed number of events and the invariant mass distributions are consistent with the standard model background expectations, and we exclude a region at 95% confidence level in the rho{T}-pi{T} mass plane. As a result, a large fraction of the region m(rho{T})=180-250 GeV/c{2} and m(pi{T})=95-145 GeV/c{2} is excluded.

Outcome of elderly patients with oesophageal squamous cell carcinoma after surgery

Background

Oesophagectomy may have morbidity and mortality rates that severely compromise long-term survival in elderly patients. The aim of this study was to compare clinical outcomes in elderly patients with oesophageal squamous cell carcinoma (SCC) with those of younger controls.

Methods

Elderly patients at least 70 years old with oesophageal SCC were matched 1 : 1 with controls aged less than 70 years according to sex, tumour stage, tumour location, histological grade, surgical approach, completeness of resection and surgical period. Co-morbidities, surgical complications, surgical mortality and long-term survival were compared.

Results

One hundred and thirty-six patients were included in each group. Surgical mortality was greater in the elderly group (5·9 versus 0·7 per cent; P = 0·036). Overall and disease-specific 5-year survival rates were worse among patients aged at least 70 years (30·0 versus 41·8 per cent, and 31·5 versus 44·7 per cent respectively), as were 10-year rates (13·7 versus 26·4 per cent, and 20·2 versus 29·0 per cent). Disease-free survival rates after 5 years (24·0 versus 35·5 per cent) and 10 years (12·3 versus 24·3 per cent) were not statistically significant (P = 0·076).

Conclusion

Poor functional status may account for higher morbidity and mortality rates in elderly patients with oesophageal SCC. Acceptable perioperative mortality rates and substantial long-term survival can still be achieved. Elderly patients should not be denied oesophagectomy.

Measurement of the Lambdab0 lifetime in Lambdab0 --> Lambdac+pi- decays in pp collisions at square root of s = 1.96 TeV

We report a measurement of the lifetime of the Lambda(b)(0) baryon in decays to the Lambda(c)(+)pi(-) final state in a sample corresponding to 1.1 fb(-1) collected in pp collisions at square root of s = 1.96 TeV by the CDF II detector at the Tevatron collider. Using a sample of about 3000 fully reconstructed Lambda(b)(0) events we measure tau(Lambda(b)(0)) = 1.401 +/- 0.046(stat) +/- 0.035(syst) ps (corresponding to ctau(Lambda(b)(0)) = 420.1 +/- 13.7(stat) +/- 10.6(syst) microm, where c is the speed of light). The ratio of this result and the world average B(0) lifetime yields tau(Lambda(b)(0))/tau(B(0)) = 0.918 +/- 0.038 (stat) and (syst), in good agreement with recent theoretical predictions.