Monte Carlo dosimetry modeling of focused kV x-ray radiotherapy of eye diseases with potential nanoparticle dose enhancement

PURPOSE

Eye plaque brachytherapy is the most common approach for intraocular cancer treatment. It is, however, invasive and subject to large setup uncertainty due to the surgical operation. We propose a novel-focused kV x-ray technique with potential nanoparticle (NP) enhancement and evaluate its application in treating choroidal melanoma and iris melanoma by Monte Carlo (MC) dosimetry modeling.

METHODS

A polycapillary x-ray lens was used to focus 45 kVp x rays to achieve pinpoint accuracy of dose delivery to small tumors near critical structures. In addition to allowing for beam focusing, the use of kV x rays takes advantage of the strong photoelectric absorption of metallic NPs in that energy regime and hence strong radiosensitization. We constructed an MC simulation program that takes into account the x-ray optic modeling and used GEANT4 for dosimetric calculation. Extensive phantom measurements using a prototype-focused x-ray system were carried out. The MC simulation of simple geometry phantom irradiation was first compared to measurements to verify the x-ray optic lens modeling in conjunction with the Geant4 dosimetric calculation. To simulate tumor treatment, a geometric eye model and two tumor models were constructed. Dose distributions of the simulated treatments were then calculated. NP radiosensitization was also simulated for two concentrations of 2 nm gold NP (AuNP) uniformly distributed in the tumor.

RESULTS

The MC-simulated full width at half maximum (FWHM) and central-axis depth dose of the focused kV x-ray beam match those measured on EBT3 films within ~10% around the depth of focus of the beam. Dose distributions of the simulated ocular tumor treatments show that focused x-ray beams can concentrate the high-dose region in or close to the tumor plus margin. For the simulated posterior choroidal tumor treatment, with sufficient tumor coverage, the doses to the optic disc and fovea are substantially reduced with focused x-ray therapy compared to eye plaque treatment (3.8 vs 39.8 Gy and 11.1 vs 53.8 Gy, respectively). The eye plaque treatment was calculated using an Eye Physics plaque with I-125 seeds under TG43 assumption. For the energy spectrum used in this study, the average simulated dose enhancement ratios (DERs) are roughly 2.1 and 1.1 for 1.0% and 0.1% AuNP mass concentration in the tumor, respectively.

CONCLUSION

Compared to eye plaque brachytherapy, the proposed focused kV x-ray technique is noninvasive and shows great advantage in sparing healthy critical organs without sacrificing the tumor control. The NP radiation dose enhancement is considerable at our proposed kV range even with a low NP concentration in the tumor, providing better critical structure protection and more flexibility for treatment planning.

Cognitive and hedonic responses to meal ingestion correlate with changes in circulating metabolites

BACKGROUND

We have previously shown that meal ingestion induces cognitive perception (sensations) with a hedonic dimension (well-being) that depends on the characteristics of the meal and the appropriateness of the digestive response. The aim of the present study is to identify metabolomic biomarkers of the cognitive response to meal ingestion.

METHODS

In 18 healthy subjects, the response to a test meal (Edanec, 1 kcal/mL) ingested until maximum satiation (50 mL/min) was assessed. Perception measurements and blood samples were taken before, at the end of the meal, and 20 min after ingestion. The cognitive response and the hedonic dimension were measured on 10 cm scales. Metabolomic analysis was performed using nuclear magnetic resonance (NMR) spectroscopy and values of triglycerides, insulin, peptide YY (PYY), and glucagon-like peptide-1 (GLP-1) were determined using conventional laboratory techniques.

KEY RESULTS

Ingestion up to maximum satiation induced sensation of fullness and decreased digestive well-being. The total amount ingested by each subject correlated with the basal sensation of hunger, but not with other sensations or blood metabolite levels. Immediately after ingestion, satiation correlated with an increase in glucose (R = 0.49; p = 0.038) and valine levels (R = 0.48; p = 0.043). Twenty-minutes after finalizing ingestion, triglyceride levels had significantly increased which correlated with the recovery in well-being (R = 0.48; p = 0.046) and the decrease in desire to eat a food of choice (R = -0.56; p = 0.016). The increase in lipids inversely correlated with abdominal discomfort (R = -0.51; p = 0.032).

CONCLUSIONS & INFERENCES

Cognitive and hedonic responses to meal ingestion correlate with changes in circulating metabolites, which may serve as objective biomarkers of perception.

Digestive, cognitive and hedonic responses to a meal

BACKGROUND

Gut dysfunctions may be associated to digestive symptoms. We hypothesized that the gut can also originate pleasant sensations, and wished to demonstrate the hedonic component of the digestive response to a meal.

METHODS

Healthy subjects (n = 42) were evaluated during basal fasting conditions and during experimentally induced fullness sensation (either by gastric distension or duodenal nutrient infusion). In each set of studies, a 240 mL test meal (12 kcal broth) and water, as inert control meal, were administered on separate days in a randomized, cross-over design. Gastric accommodation, the cognitive response and the hedonic dimension (both by 10 score scales) were measured 9 min before and 60 min after the meal.

KEY RESULTS

In basal conditions, the test meal induced a significantly greater gastric relaxation than the control meal (166 ± 28 mL isotonic volume increase 67 ± 14 mL; p = 0.002). Both meals induced epigastric fullness (3.8 ± 0.7 score and 3.2 ± 0.8 score, respectively; p = 0.740), but contrary to the inert meal, with the active meal this conscious sensation had a pleasant dimension (digestive comfort increase by 1.3 ± 0.6 score with active meal vs -1.1 ± 0.6 decrease with inert meal; p = 0.015). Experimentally induced fullness was associated to a decrease in digestive well-being or abdominal discomfort, which improved only after the active meal but not the inert meal.

CONCLUSIONS & INFERENCES

When appropriate conditions are met, the response to a meal includes a hedonic dimension involving pleasant sensation of digestive well-being.

Intracranial aneurysmal pulsatility as a new individual criterion for rupture risk evaluation: biomechanical and numeric approach (IRRAs Project)

BACKGROUND AND PURPOSE

The present study follows an experimental work based on the characterization of the biomechanical behavior of the aneurysmal wall and a numerical study where a significant difference in term of volume variation between ruptured and unruptured aneurysm was observed in a specific case. Our study was designed to highlight by means of numeric simulations the correlation between aneurysm sac pulsatility and the risk of rupture through the mechanical properties of the wall.

MATERIALS AND METHODS

In accordance with previous work suggesting a correlation between the risk of rupture and the material properties of cerebral aneurysms, 12 fluid-structure interaction computations were performed on 12 "patient-specific" cases, corresponding to typical shapes and locations of cerebral aneurysms. The variations of the aneurysmal volume during the cardiac cycle (ΔV) are compared by using wall material characteristics of either degraded or nondegraded tissues.

RESULTS

Aneurysms were located on 6 different arteries: middle cerebral artery (4), anterior cerebral artery (3), internal carotid artery (1), vertebral artery (1), ophthalmic artery (1), and basilar artery (1). Aneurysms presented different shapes (uniform or multilobulated) and diastolic volumes (from 18 to 392 mm3). The pulsatility (ΔV/V) was significantly larger for a soft aneurysmal material (average of 26%) than for a stiff material (average of 4%). The difference between ΔV, for each condition, was statistically significant: P=.005.

CONCLUSIONS

The difference in aneurysmal pulsatility as highlighted in this work might be a relevant patient-specific predictor of aneurysm risk of rupture.

Functional gut disorders or disordered gut function? Small bowel dysmotility evidenced by an original technique

BACKGROUND

This study aimed to determine the proportion of cases with abnormal intestinal motility among patients with functional bowel disorders. To this end, we applied an original method, previously developed in our laboratory, for analysis of endoluminal images obtained by capsule endoscopy. This novel technology is based on computer vision and machine learning techniques.

METHODS

The endoscopic capsule (Pillcam SB1; Given Imaging, Yokneam, Israel) was administered to 80 patients with functional bowel disorders and 70 healthy subjects. Endoluminal image analysis was performed with a computer vision program developed for the evaluation of contractile events (luminal occlusions and radial wrinkles), non-contractile patterns (open tunnel and smooth wall patterns), type of content (secretions, chyme) and motion of wall and contents. Normality range and discrimination of abnormal cases were established by a machine learning technique. Specifically, an iterative classifier (one-class support vector machine) was applied in a random population of 50 healthy subjects as a training set and the remaining subjects (20 healthy subjects and 80 patients) as a test set.

KEY RESULTS

The classifier identified as abnormal 29% of patients with functional diseases of the bowel (23 of 80), and as normal 97% of healthy subjects (68 of 70) (P < 0.05 by chi-squared test). Patients identified as abnormal clustered in two groups, which exhibited either a hyper- or a hypodynamic motility pattern. The motor behavior was unrelated to clinical features.

CONCLUSIONS & INFERENCES

With appropriate methodology, abnormal intestinal motility can be demonstrated in a significant proportion of patients with functional bowel disorders, implying a pathologic disturbance of gut physiology.

Hepatocellular carcinoma and liver transplantation: a 12-year experience

BACKGROUND

Orthotopic liver transplantation (OLT) for patients with cirrhosis and concomitant hepatocellular carcinoma (HCC) in early stages is the treatment of choice, with an acceptable recurrence rate and excellent survival.

AIM

We sought to evaluate (1) the accuracy of preoperative imaging; (2) the impact of pre-OLT treatments on survival and recurrence; and (3) the influence of beyond Milan criteria selection on global outcomes.

METHODS

We studied a cohort of 65 patients with HCC among 300 consecutive OLTs over a single 12-year experience. We analyzed the overall outcomes of survival and recurrence, the accuracy of preoperative diagnosis and staging the influence of neoadjuvant treatment prior to OLT, and the effect on overall outcomes beyond the Milan criteria in our series.

RESULTS

The 65 transplants were performed for HCC, mostly in association with hepatitis C virus and alcoholic cirrhosis with HTP. At a mean follow-up of 40.32 months, the recurrence rate was 5.7% among the 61 HCC confirmed by histopathology. The overall survival was 30.07. Actuarial survivals at 1, 5, and 10 years were 82%, 77%, and 62%, respectively. Six retransplants occurred among the seven graft losses albeit with poor survival after the second graft. Most explants showed low pTNM stages with favorable microscopic features. Preoperative imaging tests failed to achieve an accurate diagnosis in 15.38% of the series. The role of alpha-fetoprotein (AFP) and hepatic biopsy was irrelevant. Unfavorable histopathologic factors predicted a greater recurrence rate, but had no influence on survival. Neither recurrence nor survival were modified by pre-OLT therapy.

CONCLUSIONS

In our series, AFP, hepatic biopsy, and pre-OLT treatment had limited roles. Radiological imaging techniques underestimated HCC staging and lead to a misdiagnosis to an expected degree. Despite these findings, this single institution experience with OLT for HCC showed excellent survivals with a low recurrence rate including cases of patients beyond the Milan criteria.

Effect of spinal cord stimulation in a rodent model of post-operative ileus

Post-operative ileus (POI) is a transient impairment of gastrointestinal (GI) transit that develops after abdominal surgery. The goal of this study was to investigate the effect of spinal cord stimulation (SCS) on gastric emptying and upper GI transit in a rat model of POI. All rats had an electrode placed on the dorsal surface of the spinal cord between the T(5) and T(8) segments. After recovery, gastric emptying and upper GI transit (geometric centre and head of meal) were assessed using a radiolabelled meal fed to each rat via oral gavage. In unanaesthetized rats, SCS (15, 25, 50, 100, 200 Hz, 0.2 ms at 90% motor threshold for 15 min) was performed immediately after the meal. The sham control group had no current applied. The naïve group was without POI or SCS. Gastric emptying was significantly delayed in sham-stimulated rats with POI compared with naïve controls (39.8 +/- 6.2%vs 76.5 +/- 4.9%, P < 0.001). In rats with POI that underwent SCS, there was a significant acceleration of gastric emptying to levels that resembled those of naïve controls (65.1 +/- 7.4%, P < 0.05). However, while SCS did not normalize the geometric centre and head of the meal when compared with the naïve group, it did significantly improve both parameters compared with the sham stimulation group. In summary, SCS normalizes gastric emptying and improves upper GI transit in a rodent model of POI. Further experiments are required to address the mechanism(s) by which SCS exhibits prokinetic activity.

Use of the air pouch model to investigate immune responses to a hookworm vaccine containing the Na-ASP-2 protein in rats

Hookworms are gastrointestinal nematodes that affect approximately 600 million people in developing countries. Using the air pouch model, we have examined the effects of vaccination with the recombinant hookworm larval antigen Na-ASP-2 and the adjuvant Alhydrogel on the skin immune response to hookworms in Sprague Dawley rats. Following vaccination, rats were inoculated 100 Necator americanus L3 into the air pouch, and the exudates and cell infiltrates were collected from the pouch 24 h later. Larval inoculation induced leucocyte recruitment into the pouch. Exudates of rats vaccinated with Na-ASP-2 showed an increase of cytokines such as IL-4, IL-10, IFN-gamma and especially, IL-5, as well as IgG1 and IgG2 antibodies. The increased amount of antigen-presenting cells and cytokines in the pouch of vaccinated animals suggests that vaccination could potentially restrain this parasite to the inoculation site, avoiding its migration and establishment in the host. Moreover, the air pouch model could constitute an alternative to screen immune responses to L3 antigens.

Comparative immunology of human and animal models of hookworm infection

Hookworm infection is a major cause of disease burden for animals and humans. Over the past years, the use of animal models in hookworm infections has been driven by the search of new anthelminthic therapies and, especially, vaccine development. These studies also contributed to the advance of knowledge on immunity to hookworms, offering new insights to understand the nature of this parasitic infection. In this article, we will summarize the essential features of the immune response in the two major animal models of hookworm infections (dog and hamster) and then consider its implication for the human immune response.

Evidence for vertical phase separation in densely grafted, high-molecular-weight poly(-isopropylacrylamide) brushes in water

The detailed conformational change of poly(N-isopropylacrylamide) (PNIPAM) brushes at high grafting density in D2O was investigated as a function of temperature using neutron reflection. PNIPAM chains were grafted at high surface density from gold and silicon oxide surfaces by atom transfer radical polymerization. Whereas single layer profiles were observed for temperatures below and above the transition region, bilayer profiles were observed for a narrow range of temperatures near the transition. This nonmonotonic change in the concentration profile with temperature is discussed in the context of theoretical models of vertical phase separation within a brush.

Skin dendritic cells in murine cutaneous leishmaniasis

Studies of the immunopathogenesis of Leishmania major-induced murine cutaneous leishmaniasis provide a framework for understanding the evolution of L. major infection of skin in humans and the foundation for rationale vaccine design. Experiments in which infection is initiated with "suprap hysiologic" numbers of parasites clearly identify Th-derived type I cytokines as essential participants in macrophage activation and macrophage nitric oxide production as prerequisite for parasite control. Dendritic cells, rather than macrophages, appear to be responsible for L. major-specific Th priming in these studies. Recent studies of murine cutaneous leishmaniasis in a model system in which infection is initiated with lower, more physiologic numbers of parasites confirm many of the important findings obtained in "high dose" inoculation models, but important differences have been noted. The low dose inoculation model should ultimately provide insights into mechanisms that are responsible for dendritic cell recruitment into leishmania lesions, mechanisms that facilitate parasite acquisition by skin dendritic cells and cellular interactions that eventuate in T cell priming and lesion involution.

The role of interleukin (IL)-10 in the persistence of Leishmania major in the skin after healing and the therapeutic potential of anti-IL-10 receptor antibody for sterile cure

Some pathogens (e.g., Mycobacterium tuberculosis, Toxoplasma gondii, Leishmania spp) have been shown to persist in their host after clinical cure, establishing the risk of disease reactivation. We analyzed the conditions necessary for the long term maintenance of Leishmania major in genetically resistant C57BL/6 mice after spontaneous healing of their dermal lesions. Interleukin (IL)-10 was found to play an essential role in parasite persistence as sterile cure was achieved in IL-10-deficient and IL-4/IL-10 double-deficient mice. The requirement for IL-10 in establishing latency associated with natural infection was confirmed in IL-10-deficient mice challenged by bite of infected sand flies. The host-parasite equilibrium was maintained by CD4+ and CD8+ T cells which were each able to release IL-10 or interferon (IFN)-gamma, and were found to accumulate in chronic sites of infection, including the skin and draining lymph node. A high frequency of the dermal CD4+ T cells released both IL-10 and IFN-gamma. Wild-type mice treated transiently during the chronic phase with anti-IL-10 receptor antibodies achieved sterile cure, suggesting a novel therapeutic approach to eliminate latency, infection reservoirs, and the risk of reactivation disease.

A natural model of Leishmania major infection reveals a prolonged "silent" phase of parasite amplification in the skin before the onset of lesion formation and immunity

A model of Leishmania major infection in C57BL/6 mice has been established that combines two main features of natural transmission: low dose (100 metacyclic promastigotes) and inoculation into a dermal site (the ear dermis). The evolution of the dermal lesion could be dissociated into two distinct phases. The initial "silent" phase, lasting 4-5 wk, favored establishment of the peak load of parasites in the dermis in the absence of lesion formation or any overt histopathologic changes in the site. The second phase corresponds to the development of a lesion associated with an acute infiltration of neutrophils, macrophages, and eosinophils into the dermis and was coincident with the killing of parasites in the site. The onset of immunity/pathology was correlated with the appearance of cells staining for IL-12p40 and IFN-gamma in the epidermal compartment, and an expansion of T cells capable of producing IFN-gamma in the draining lymph node. Parasite growth was not enhanced over the first 4.5 wk in anti-CD4-treated mice, SCID mice, or C57BL/6 mice deficient in IL-12p40, IFN-gamma, CD40 ligand, or inducible NO synthase. These mice all failed to ultimately control infection in the site, but in some cases (anti-CD4 treated, IL-12p40-/-, CD40 ligand-/-, and SCID) high dermal parasite loads were associated with little or no pathology. These results extend to a natural infection model a role for Th1 cells in both acquired resistance and lesion formation, and document the remarkable avoidance of this response during a prolonged phase of parasite amplification in the skin.

Vaccination of Manchego lambs against Haemonchus contortus with a somatic fraction (p26/23) of adult parasites

A low molecular weight fraction from adult Haemonchus contortus containing two peptides (p26/23) was used to vaccinate Manchego female lambs between 3.5 and 5 months of age. Immunizing injections were given three times on days 0, 14 and 28 of the experiment. On day 43, lambs were challenged with 400 third stage larvae/kg live weight. Vaccination induced a lengthening of prepatent periods, significant reduction (> 60%) in mean faecal egg counts and smaller variations in packed cell volume values. At necropsy, average worm burden in the vaccinated lambs was significantly lower (61.6%) than that found in unvaccinated challenged animals. A clear correlation was found between protection and serum antibody response in immunized lambs.