Monte Carlo simulations and phantom validation of low-dose radiotherapy to the lungs using an interventional radiology C-arm fluoroscope

PURPOSE

To use MC simulations and phantom measurements to investigate the dosimetry of a kilovoltage x-ray beam from an IR fluoroscope to deliver low-dose (0.3-1.0 Gy) radiotherapy to the lungs.

MATERIALS AND METHODS

PENELOPE was used to model a 125 kV, 5.94 mm Al HVL x-ray beam produced by a fluoroscope. The model was validated through depth-dose, in-plane/cross-plane profiles and absorbed dose at 2.5-, 5.1-, 10.2- and 15.2-cm depths against the measured beam in an acrylic phantom. CT images of an anthropomorphic phantom thorax/lungs were used to simulate 0.5 Gy dose distributions for PA, AP/PA, 3-field and 4-field treatments. DVHs were generated to assess the dose to the lungs and nearby organs. Gafchromic film was used to measure doses in the phantom exposed to PA and 4-field treatments, and compared to the MC simulations.

RESULTS

Depth-dose and profile results were within 3.2% and 7.8% of the MC data uncertainty, respectively, while dose gamma analysis ranged from 0.7 to 1.0. Mean dose to the lungs were 1.1-, 0.8-, 0.9-, and 0.8- Gy for the PA, AP/PA, 3-field, and 4-field after isodose normalization to cover ∼ 95% of each lung volume. Skin dose toxicity was highest for the PA and lowest for the 4-field, and both arrangements successfully delivered the treatment on the phantom. However, the dose distribution for the PA was highly non-uniform and produced skin doses up to 4 Gy. The dose distribution for the 4-field produced a uniform 0.6 Gy dose throughout the lungs, with a maximum dose of 0.73 Gy. The average percent difference between experimental and Monte Carlo values were -0.1% (range -3% to +4%) for the PA treatment and 0.3% (range -10.3% to +15.2%) for the 4-field treatment.

CONCLUSION

A 125 kV x-ray beam from an IR fluoroscope delivered through two or more fields can deliver an effective low-dose radiotherapy treatment to the lungs. The 4-field arrangement not only provides an effective treatment, but also significant dose sparing to healthy organs, including skin, compared to the PA treatment. Use of fluoroscopy appears to be a viable alternative to megavoltage radiation therapy equipment for delivering low-dose radiotherapy to the lungs.

Spectral characterization of flash and high flux x-ray radiographic sources with a magnetic Compton spectrometer

In this work, we present a new analysis method applied to revitalize permanent magnet Compton spectrometers used to measure photon energy spectra in the MeV range. The inversion of the measured electron distribution to determine the original photon distribution is achieved via a method of consistent coupled radiation transport and magnetic field mapping of the input photon spectra to the measured electron distribution. The method of linear least squares was used to perform the unfolding of the electron distribution to the initial photon spectra, without any assumptions made regarding the electron distribution. We present an application of this method to data from a nominal 19.4 MeV flash radiographic source (the first axis of the Dual Axis Radiographic Hydro-Test Facility) capable of generating 500 R @ 1 m in ∼60 ns and a medical therapy source (a Scanditronix M22, Microtron) capable of variable energies with nominal endpoints of 6, 10, 15, and 20 MeV and an output of ∼1000-2000 R/min @ 1 m. The results provide agreement between the modeled and unfolded experimentally measured photon spectra as quantified by statistical tests, from 1.5 to 20 MeV. Experimental results are presented as well as a discussion of the novel MCNP6-based simulations and methods for reconstruction of the spectra.

Replicating ¡Cuídate!: 6-Month Impact Findings of a Randomized Controlled Trial

OBJECTIVES

To test whether ¡Cuídate!, a program culturally adapted for Hispanic youths, affects sexual risk behavior.

METHODS

We evaluated 3 replications of ¡Cuídate! in California, Arizona, and Massachusetts in a randomized controlled trial (registry no. NCT02540304) in which 2169 primarily Hispanic participants were randomly assigned to an intervention (n = 1326) or a control (n = 870) group. Youths were surveyed at baseline (September 2012-April 2014) and 6 months postbaseline (March 2013-October 2014). We estimated pooled and subgroup impacts using a regression framework with baseline covariates to increase statistical precision (1216 youths analyzed in the treatment group, 806 analyzed in the control group).

RESULTS

We found no impacts on the study's primary outcomes of recent sexual activity or recent unprotected sexual activity. However, ¡Cuídate! improved knowledge (10%-20% increase; P < .001), attitudes (effect size = .24; P < .001), and skills (effect size = .14; P = .002). Exploratory subgroup analyses suggest potentially problematic effects for some groups.

CONCLUSIONS

Findings suggest that ¡Cuídate! was effective in improving youths' knowledge and attitudes. However, after 6 months, these changes did not translate to improvements in reported sexual risk behaviors.

Perceptions and Motivations to Prevent Heart Disease among Puerto Ricans

OBJECTIVES

We performed a qualitative assessment of Puerto Ricans' knowledge and perceptions of cardiovascular disease (CVD), and motivations/barriers and preferences to participate in community/ clinical programs for CVD-prevention.

METHODS

Four guided focus group discussions were conducted on a total of 24 Puerto Ricans, aged 40-60 years in Boston, MA.

RESULTS

Participants were aware of CVD, but less knowledgeable about its prevention. They perceived it as serious, and either had CVD or knew someone who had it. They favored education and activities on nutrition, exercise, clinical advice, and social interaction, in weekly/ biweekly small-group sessions with other Latinos, led in Spanish by a familiar health professional, in a convenient community location. Age- and culture-specific program content and educational materials were preferred. A theme emerged on 'personal or family motivations' such as to become healthier and live longer so they would feel better and support their families, or to learn about CVD-prevention. Main barriers included family obligations, weather, safety concerns, transportation, and depressive mood.

CONCLUSIONS

Culturally-tailored CVD-prevention programs for Puerto Ricans should include multiple behavioral and social approaches, and draw on intrinsic motivators while reducing barriers to help enhance efficacy and sustainability.

Population mobility and the changing epidemics of HIV-2 in Portugal

INTRODUCTION

Portugal is the European country with the highest frequency of HIV-2 infection, which is mainly concentrated in West Africa. The cumulative number of notified HIV-2 infections in Portugal was 1813 by the end of December 2008. To better characterize the dynamics of HIV-2 infection in the country and to obtain data that may be of use in the prevention of the spread of HIV-2, we evaluated a large pooled sample of patients.

PATIENTS AND METHODS

Five Portuguese hospitals provided data on HIV-2-infected patients from 1984 to the end of 2007. Data concerning demographic characteristics and clinical variables were extracted. Patients were stratified according to date of diagnosis in approximately 5-year categories.

RESULTS

The sample included 442 patients, accounting for 37% of all HIV-2 infections notified in Portugal during that period. HIV-2-infected patients showed clearly different characteristics according to the period of diagnosis. Until 2000, the majority of HIV-2-infected patients were Portuguese-born males living in the north of the country. From 2000 to 2007, most of the patients diagnosed with HIV-2 infection had a West African origin, were predominantly female and were living in the capital, Lisbon. The average age at diagnosis and loss to follow-up significantly increased over time.

CONCLUSION

HIV-2 infection has been documented in Portugal since the early 1980s and its epidemiology appears to reflect changes in population movement. These include the movements of soldiers and repatriates from African territories during the independence wars and, later, migration and mobility from high-endemicity areas. The findings of this study stress the importance of promoting migrant-sensitive health care.

Gene expression in histologically normal epithelium from breast cancer patients and from cancer-free prophylactic mastectomy patients shares a similar profile

INTRODUCTION

We hypothesised that gene expression in histologically normal (HN) epithelium (NlEpi) would differ between breast cancer patients and usual-risk controls undergoing reduction mammoplasty (RM), and that gene expression in NlEpi from cancer-free prophylactic mastectomy (PM) samples from high-risk women would resemble HN gene expression.

METHODS

We analysed gene expression in 73 NlEpi samples microdissected from frozen tissue. In 42 samples, we used microarrays to compare gene expression between 18 RM patients and 18 age-matched HN (9 oestrogen receptor (ER)+, 9 ER-) and 6 PM patients. Data were analysed using a Bayesian approach (BADGE), and validated with quantitative real-time PCR (qPCR) in 31 independent NlEpi samples from 8 RM, 17 HN, and 6 PM patients.

RESULTS

A total of 98 probe sets (86 genes) were differentially expressed between RM and HN samples. Performing hierarchical analysis with these 98 probe sets, PM and HN samples clustered together, away from RM samples. qPCR validation of independent samples was high (84%) and uniform in RM compared with HN patients, and lower (58%), but more heterogeneous, in RM compared with PM patients. The 86 genes were implicated in many processes including transcription and the MAPK pathway.

CONCLUSION

Gene expression differs between the NlEpi of breast cancer cases and controls. The profile of cancer cases can be discerned in high-risk NlEpi from cancer-free breasts. This suggests that the profile is not an effect of the tumour, but may mark increased risk and reveal the earliest genomic changes of breast cancer.

Relevance of Group Milleri Streptococci in Thoracic Surgery: A Clinical Update

Group Milleri streptococci (GMS), a heterogeneous group of streptococci, are associated with purulent infections. This study was a retrospective analysis of all consecutive thoracic infections of GMS between 2001 and 2004. Of 246 surgical GMS infections, thoracic infections accounted for 4.5 per cent, including 10 pleural infections (eight empyemas and two infected pleural effusions) and one mediastinal infection. The etiology of pleural infection was parapneumonic (7), second to esophageal perforation (1), liver transplantation (1), and liver resection (1). Polymicrobial infections were present in 64 per cent. All patients underwent removal of the infected masses, including drainage (3), thoracoscopic decortication (5), thoracotomy with debridement (2), and incision with drainage (1). The case fatality rate was 9 per cent (there was one patient with congestive heart disease unfit to undergo surgical empyema evacuation) and the recurrence rate was 27.3 per cent (three patients). Combined antibiotic/surgical treatment was successful in all other cases. GMS isolates were susceptible to clindamycin and all β-lactam antibiotics except ceftazidime, but were resistant to aminoglycosides. If found intrathoracically, GMS frequently progress to severe empyema. Therefore, timely removal of pleural collection by percutaneous drainage or surgical intervention seems indicated. If surgery is required, thoracoscopic decortication may be the preferred approach.

Relevance of group Milleri streptococci in thoracic surgery: a clinical update

Group Milleri streptococci (GMS), a heterogeneous group of streptococci, are associated with purulent infections. This study was a retrospective analysis of all consecutive thoracic infections of GMS between 2001 and 2004. Of 246 surgical GMS infections, thoracic infections accounted for 4.5 per cent, including 10 pleural infections (eight empyemas and two infected pleural effusions) and one mediastinal infection. The etiology of pleural infection was parapneumonic (7), second to esophageal perforation (1), liver transplantation (1), and liver resection (1). Polymicrobial infections were present in 64 per cent. All patients underwent removal of the infected masses, including drainage (3), thoracoscopic decortication (5), thoracotomy with debridement (2), and incision with drainage (1). The case fatality rate was 9 per cent (there was one patient with congestive heart disease unfit to undergo surgical empyema evacuation) and the recurrence rate was 27.3 per cent (three patients). Combined antibiotic/surgical treatment was successful in all other cases. GMS isolates were susceptible to clindamycin and all beta-lactam antibiotics except ceftazidime, but were resistant to aminoglycosides. If found intrathoracically, GMS frequently progress to severe empyema. Therefore, timely removal of pleural collection by percutaneous drainage or surgical intervention seems indicated. If surgery is required, thoracoscopic decortication may be the preferred approach.

Toxoplasma gondii: Differential protection rates by two strains against cyst formation in a rat model

A previous infection with the ME-49 strain of Toxoplasma gondii (of low pathogenicity for mice), protected 17 of 20 rats against formation of brain cysts, following challenge with 10(3) oocysts of the high pathogenicity M3 strain, as determined by bioassay of rat brains in mice. The low pathogenic KSU strain did not afford comparable protection. Protection was further tested in rats that were orally or subcutaneously immunized with cysts or oocysts of the ME-49 strain, and later challenged with 2 x 10(2) cysts or 10(2) oocysts of the highly pathogenic strains M3, M-7741 and C. Protection ranged from 43 to 100%, compared to non immunized control rats and was independent of the stage of ME-49 strain and of the routes used to immunize the rats. The results obtained encourage further investigation into prevention of toxoplasmosis in humans and food animals.

Association of clinical risk factors with functional status following lung transplantation

A fundamental goal of lung transplantation is the regaining of functional capacity, yet little is known about what factors are associated with the achievement of this goal. The aim of this study is to test the association of clinical risk factors with functional status 1 year following lung transplantation. We conducted a cohort study of 321 lung transplants and assessed functionality by the distance achieved during a standard 6-min walk test (6MWT). Preoperative recipient risk factors were evaluated for association with functional status and adjusted for confounding using multivariable linear regression models. In these multivariable analyses, recipient female gender (p<0.001), recipient pretransplant body mass index (BMI) of greater than 27 kg/m2 (p=0.017) and shorter pretransplant 6MWT distances (p=0.006) were independently associated with shorter distances achieved during 6MWT after lung transplant, while cystic fibrosis (CF) (p=0.003), and bilateral lung transplant (p=0.014) were independently associated with longer distances achieved. Approximately 51% of the variance in 6MWT distance was explained by these risk factors in the linear regression models (R2=0.51). These findings may have implications in patient counseling, selection, procedure choice, and may lead to interventions aimed at improving the functional outcomes of lung transplantation.

Case report of lamivudine-resistant hepatitis B virus infection post liver transplantation from a hepatitis B core antibody donor

The use of allografts from donors with hepatitis B core antibody in liver transplantation (LT) is associated with the risk of de novo hepatitis B virus (HBV) infection. Prophylaxis using hepatitis B Immune globulin (HBIg) and lamivudine alone or in combination has been reported. Yet, there are no standardized regimens and long-term efficacy is not known. We report a case of a patient who underwent LT for alcoholic liver disease who received an allograft from a donor with Hepatitis B core antibody. The patient had no previous exposure to HBV, was vaccinated against HBV, and had demonstrated Hepatitis B surface antibody present in serum before and 6 months after transplantation. Prophylaxis with short-term HBIg (1 week) and indefinite lamivudine was given. De novo HBV infection developed more than 3 years after LT with a lamivudine-resistant polymerase mutant containing the rtM204I and rtl180L/M mutations. We reviewed the risk of de novo post-LT HBV infection in recipients of livers from hepatitis B core antibody positive donors. High risk were HBV naïve recipients, moderate risk recipients had isolated hepatitis B surface antibody (anti-HBs) or hepatitis B core antibody (anti-HBc), while low-risk recipients had both anti-HBs and anti-HBc. We reviewed prophylaxis protocols reported in the literature and made recommendations for management.

Structure of rutile TiO2 (110)-(1 x 2): formation of Ti2O3 quasi-1D metallic chains

Combining STM, LEED, and density functional theory, we determine the atomic surface structure of rutile TiO2 (110)-(1 x 2): nonstoichiometric Ti2O3 stripes along the [001] direction. LEED patterns are sharp and free of streaks, while STM images show monatomic steps, wide terraces, and no cross-links. At room temperature, atoms in the Ti2O3 group have large amplitudes of vibration. The long quasi-1D chains display metallic character, show no interaction between them, and cannot couple to bulk or surface states in the gap region, forming good atomic wires.

Pathogen inactivation of Leishmania donovani infantum in plasma and platelet concentrates using riboflavin and ultraviolet light

BACKGROUND AND OBJECTIVES

Leishmania is transmitted by the bite of the phlebotomine sandfly or by transfusion of infected blood products. Leishmaniasis currently poses a significant problem in several parts of the world, and is an emerging problem in others. The Mirasol PRT technology is based on the use of riboflavin and ultraviolet light to generate chemical reactions in the nucleic acids of pathogens, which prevents replication and leads to inactivation. The intent of this study was to examine the ability of the Mirasol PRT System to kill the Leishmania parasite in human plasma and platelet concentrates.

MATERIALS AND METHODS

In visceral Leishmaniasis, amastigotes are present in the blood and in the reticuloendothelial system within monocytes. For each unit of plasma or platelets treated, isolated mononuclear cells obtained from 100 ml of normal donor whole blood were incubated with 1.0 x 10(8) Leishmania donovani infantum promastigotes to produce amastigote-laden macrophages. The infected macrophages were added to 250 ml of human plasma or to 250 ml of platelet concentrates. Infected units were cultured pretreatment in 10-fold serial dilutions to determine the limits of detection. Thirty millilitres of 500 microM riboflavin was added to each unit, which was then illuminated with 5.9 J/cm2 of ultraviolet light (6.24 J/ml). After treatment and after 2 months of frozen storage, plasma units were cultured in 10-fold serial dilutions. Platelets were cultured on the day of treatment and on day 5 of storage post-illumination.

RESULTS

A 5 log reduction of Leishmania was demonstrated in five of six units of plasma, and a 7 log reduction of Leishmania was demonstrated in one plasma unit. A 5 log reduction of Leishmania was demonstrated in five of six units of platelets, and a 6 log reduction of Leishmania was demonstrated in one unit.

CONCLUSIONS

There is no donor screen for Leishmania and other pathogens constantly emerging in our blood supply. The Mirasol PRT System for Platelets and Plasma is an effective means of killing Leishmania and other emerging pathogens in these blood products.

Characteristics of pollinosis caused by Betula in patients from Ourense (Galicia, Spain)

A retrospective study was performed to describe the features of the pollinosis caused by Betula in the area of Ourense, Spain. The pollen count was carried out with a Lanzoni volumetric Hirts spore trap (1993-2000). The Betula pollen represented 5% over the annual total (annual mean quantity: 965 grains). It was present in the air from March to mid-May. The highest peaks took place in April (maximum values mean: 131 grains/m3). The medical records of 222 patients (mean age 25.66 years) diagnosed with pollinosis (1998-2000), who lived at less than 30 km. from the spore trap, were reviewed. In all of them, the skin-prick test (SPT) was carried out with pollen allergens. The percentages of positive SPT were: Lolium perenne, 91.89% (16.6% monosensitized); Plantago lanceolata, 71.17% (1.26% monosensitized); Betula alba, 41.89% (10.75% monosensitized); Platanus hybrida, 34.95%; Olea europea, 10.36%; and Parietaria judaica, 6.3%. The mean age of Betula monosensitized patients was 44.7 years. The majority of them had symptoms in March-April, 40% had asthma symptoms, 80% had lived in Central Europe, and 30% of them presented an oral allergy syndrome to fruits. There were 41.93% of the patients with positive SPT to Betula pollen who had asthma symptoms, in comparison with 23.25% of the patients with negative SPT to Betula (p = 0.0034). There were 20.28% of the patients with positive SPT to Betula pollen, who had lived in Central Europe, in comparison with 4.27% of the patients with negative SPT to Betula, p: 0.00049. The relative risk of sensitization was 2.05.

CONCLUSIONS

Betula pollen was the second cause of clinical pollinosis in our patients, after grass, being responsible of the symptoms in the early spring, in a small number of the patients in their forties. The presence of asthma was higher in Betula sensitized patients, and the residence in Central Europe was a sensitization risk factor.

An investigation of sterile immunity against toxoplasmosis in rats

The non-persistent BK strain was examined for its ability to induce sterile immunity in Wistar rats. Groups of 2-9 Wistar rats were inoculated subcutaneously with 5 x 10(4) BK strain tachyzoites per rat. Two months later, 46 rats were dosed by gavage with 2 x 10(1) cysts of the C, ME-49, Prugniaud, C-56, Elg, M-7741 or M3 strains. Another 26 rats were inoculated with 10(3) oocysts of the ME49, M7741, Bear or Hopa-Hopa strains of Toxoplasma gondii. After 2 months, the rats were euthanized and their brains screened microscopically for toxoplasma tissue cysts and bioassayed in mice if negative. As judged by bioassay, the BK strain of Toxoplasma induced statistically significant protection against reinfection only when rats were challenged with cysts of the C and Prugniaud strains or with oocysts of the ME49 strain. Nonetheless, cysts were detected microscopically only in 23% of brains of immunized rats challenged with oocysts of the Bear and Hopa-Hopa strains of Toxoplasma and none of those challenged with tissue cysts of any strain. Tissue cysts were detected in 43 and 48% of non-immunized control rats infected with tissue cysts and oocysts, respectively. The overall infection in control rats (microscopy and bioassay) was 70 and 72% for rats inoculated with cysts and oocysts, respectively. These results are consistent with the divergent results obtained by other investigators with regard to protection after challenge with different complete strains (cyst and oocysts forming) of the parasite, of rats immunized with incomplete strains.

Treatment of Type II Endoleaks after Endovascular Repair of Abdominal Aortic Aneurysms: Translumbar Puncture and Injection of Thrombin into the Aneurysm Sac

OBJECTIVES

The aim of this article is to report our experience in the use of a new technique for the treatment of type II endoleaks which appear after the endovascular treatment of abdominal aortic aneurysms.

MATERIALS AND METHODS

In three patients with secondary type II endoleaks, we performed a translumbar puncture, introducing a 22-Gauge needle into the aneurysm sac under CT guidance. Once intrasac pressure had been registered, 1000U (2 ml) of human thrombin were slowly injected into the sac.

RESULTS

Complete sealing of the endoleak was achieved in all three patients, confirmed by the lack of contrast filling of the sac in the CT scans performed 5 min and 24 h after the procedure. Initial intrasac pressure was equal to systolic arterial pressure in the three patients. After the procedure, the pressure decreased by 30-40 mmHg. There were no complications during the procedure, which lasted 45-90 min. No endoleak recurrence has been observed in any of the three cases 6 months later.

CONCLUSIONS

We present an alternative method of treating type II endoleaks, which could become the treatment of choice if and when a wider experience confirms our initial good results.