Shielding requirements in helical tomotherapy.

Helical tomotherapy is a relatively new intensity-modulated radiation therapy (IMRT) treatment for which room shielding has to be reassessed for the following reasons. The beam-on-time needed to deliver a given target dose is increased and leads to a weekly workload of typically one order of magnitude higher than that for conventional radiation therapy. The special configuration of tomotherapy units does not allow the use of standard shielding calculation methods. A conventional linear accelerator must be shielded for primary, leakage and scatter photon radiations. For tomotherapy, primary radiation is no longer the main shielding issue since a beam stop is mounted on the gantry directly opposite the source. On the other hand, due to the longer irradiation time, the accelerator head leakage becomes a major concern. An analytical model based on geometric considerations has been developed to determine leakage radiation levels throughout the room for continuous gantry rotation. Compared to leakage radiation, scatter radiation is a minor contribution. Since tomotherapy units operate at a nominal energy of 6 MV, neutron production is negligible. This work proposes a synthetic and conservative model for calculating shielding requirements for the Hi-Art II TomoTherapy unit. Finally, the required concrete shielding thickness is given for different positions of interest.

Stability of the Helical TomoTherapy Hi·Art II detector for treatment beam irradiations.

The Hi·Art II Helical TomoTherapy (HT) unit is equipped with a built-in onboard MVCT detector used for patient imaging and beam monitoring. Our aim was to study the detector stability for treatment beam measurements. We studied the MVCT detector response with the 6 MV photon beam over time, throughout short-term (during an irradiation) and long-term (two times 50 days) periods. Our results show a coefficient of variation ≤ 1% for detector chambers inside the beam (excluding beam gradients) for short- and long-term response of the MVCT detector. Larger variations were observed in beam gradients and an influence of the X-ray target where degradation was found. The results assume that an 'air scan' procedure is performed daily to recalibrate the detector with the imaging beam. On short term, the detector response stability is comparable to other devices. Long-term measure- ments during two 50-day periods show a good reproducibility. 

Use of active personal dosemeters in interventional radiology and cardiology: Tests in laboratory conditions and recommendations - ORAMED project

Active personal dosemeters (APD) have been found to be very efficient tools to reduce occupational doses in many applications of ionizing radiation. In order to be used in interventional radiology and cardiology (IR/IC), APDs should be able to measure low energy photons and pulsed radiation with relatively high instantaneous personal dose equivalent rates. A study concerning the optimization of the use of APDs in IR/IC was performed in the framework of the ORAMED project, a Collaborative Project (2008-2011) supported by the European Commission within its 7th Framework Program. In particular, eight commercial APDs were tested in continuous and pulsed X-ray fields delivered by calibration laboratories in order to evaluate their performances. Most of APDs provide a response in pulsed mode more or less affected by the personal dose equivalent rate, which means they could be used in routine monitoring provided that correction factors are introduced. These results emphasize the importance of adding tests in pulsed mode in type-test procedures for APDs. Some general recommendations are proposed in the end of this paper for the selection and use of APDs at IR/IC workplaces.

Laser-Ultraviolet-A induced ultra weak photon emission in human skin cells: A biophotonic comparison between keratinocytes and fibroblasts

Photons participate in many atomic and molecular interactions and processes. Recent biophysical research has discovered an ultraweak radiation in biological tissues. It is now recognized that plants, animal and human cells emit this very weak biophotonic emission which can be readily measured with a sensitive photomultiplier system. UVA laser induced biophotonic emission of cultured cells was used in this report with the intention to detect biophysical changes between young and adult fibroblasts as well as between fibroblasts and keratinocytes. With suspension densities ranging from 1-8x106 cells/ml, it was evident that an increase of the UVA-laser-light induced photon emission intensity could be observed in young as well as adult fibroblastic cells. By the use of this method to determine ultraweak light emission, photons in cell suspensions in low volumes (100 mu l) could be detected, in contrast to previous procedures using quantities up to 10 ml. Moreover, the analysis has been further refined by turning off the photomultiplier system electronically during irradiation leading to the first measurements of induced light emission in the cells after less than 10 mu s instead of more than 100 milliseconds. These significant changes lead to an improvement factor up to 106 in comparison to classical detection procedures. In addition, different skin cells as fibroblasts and keratinocytes stemining from the same donor were measured using this new highly sensitive method in order to find new biophysical insight of light pathways. This is important in view to develop new strategies in biophotonics especially for use in alternative therapies.

Ultraweak photon emission in assessing bone growth factor efficiency using fibroblastic differentiation.

Photons participate in many atomic and molecular interactions and changes. Recent biophysical research has shown the induction of ultraweak photons in biological tissue. It is now established that plants, animal and human cells emit a very weak radiation which can be readily detected with an appropriate photomultiplier system. Although the emission is extremely low in mammalian cells, it can be efficiently induced by ultraviolet light. In our studies, we used the differentiation system of human skin fibroblasts from a patient with Xeroderma Pigmentosum of complementation group A in order to test the growth stimulation efficiency of various bone growth factors at concentrations as low as 5 ng/ml of cell culture medium. In additional experiments, the cells were irradiated with a moderate fluence of ultraviolet A. The different batches of growth factors showed various proliferation of skin fibroblasts in culture which could be correlated with the ultraweak photon emission. The growth factors reduced the acceleration of the fibroblast differentiation induced by mitomycin C by a factor of 10-30%. In view that fibroblasts play an essential role in skin aging and wound healing, the fibroblast differentiation system is a very useful tool in order to elucidate the efficacy of growth factors.

Shikonin-loaded antibody-armed nanoparticles for targeted therapy of ovarian cancer.

Conventional chemotherapy of ovarian cancer often fails because of initiation of drug resistance and/or side effects and trace of untouched remaining cancerous cells. This highlights an urgent need for advanced targeted therapies for effective remediation of the disease using a cytotoxic agent with immunomodulatory effects, such as shikonin (SHK). Based on preliminary experiments, we found SHK to be profoundly toxic in ovarian epithelial cancer cells (OVCAR-5 and ID8 cells) as well as in normal ovarian IOSE-398 cells, endothelial MS1 cells, and lymphocytes. To limit its cytotoxic impact solely to tumor cells within the tumor microenvironment (TME), we aimed to engineer SHK as polymeric nanoparticles (NPs) with targeting moiety toward tumor microvasculature. To this end, using single/double emulsion solvent evaporation/diffusion technique with sonication, we formulated biodegradable NPs of poly(lactic-co-glycolic acid) (PLGA) loaded with SHK. The surface of NPs was further decorated with solubilizing agent polyethylene glycol (PEG) and tumor endothelial marker 1 (TEM1)/endosialin-targeting antibody (Ab) through carbodiimide/N-hydroxysuccinimide chemistry. Having characterized the physicochemical and morphological properties of NPs, we studied their drug-release profiles using various kinetic models. The biological impact of NPs was also evaluated in tumor-associated endothelial MS1 cells, primary lymphocytes, and epithelial ovarian cancer OVCAR-5 cells. Based on particle size analysis and electron microscopy, the engineered NPs showed a smooth spherical shape with size range of 120 to 250 nm and zeta potential value of -30 to -40 mV. Drug entrapment efficiency was ~80%-90%, which was reduced to ~50%-60% upon surface decoration with PEG and Ab. The liberation of SHK from NPs showed a sustained-release profile that was best fitted with Wagner log-probability model. Fluorescence microscopy and flow cytometry analysis showed active interaction of Ab-armed NPs with TEM1-positive MS1 cells, but not with TEM1-negative MS1 cells. While exposure of the PEGylated NPs for 2 hours was not toxic to lymphocytes, long-term exposure of the Ab-armed and PEGylated NPs was significantly toxic to TEM1-positive MS1 cells and OVCAR-5 cells. Based on these findings, we propose SHK-loaded Ab-armed PEGylated PLGA NPs as a novel nanomedicine for targeted therapy of solid tumors.

Length of the Mitral Isthmus But Not Anatomical Location of Ablation Line Predicts Bidirectional Mitral Isthmus Block in Patients Undergoing Catheter Ablation of Persistent Atrial Fibrillation: A Randomized Controlled Trial.

INTRODUCTION: Mitral isthmus (MI) ablation is an effective option in patients undergoing ablation for persistent atrial fibrillation (AF). Achieving bidirectional conduction block across the MI is challenging, and predictors of MI ablation success remain incompletely understood. We sought to determine the impact of anatomical location of the ablation line on the efficacy of MI ablation. METHODS AND RESULTS: A total of 40 consecutive patients (87% male; 54 ± 10 years) undergoing stepwise AF ablation were included. MI ablation was performed in sinus rhythm. MI ablation was performed from the left inferior PV to either the posterior (group 1) or the anterolateral (group 2) mitral annulus depending on randomization. The length of the MI line (measured with the 3D mapping system) and the amplitude of the EGMs at 3 positions on the MI were measured in each patient. MI block was achieved in 14/19 (74%) patients in group 1 and 15/21 (71%) patients in group 2 (P = NS). Total MI radiofrequency time (18 ± 7 min vs. 17 ± 8 min; P = NS) was similar between groups. Patients with incomplete MI block had a longer MI length (34 ± 6 mm vs. 24 ± 5 mm; P < 0.001), a higher bipolar voltage along the MI (1.75 ± 0.74 mV vs. 1.05 ± 0.69 mV; P < 0.01), and a longer history of continuous AF (19 ± 17 months vs. 10 ± 10 months; P < 0.05). In multivariate analysis, decreased length of the MI was an independent predictor of successful MI block (OR 1.5; 95% CI 1.1-2.1; P < 0.05). CONCLUSIONS: Increased length but not anatomical location of the MI predicts failure to achieve bidirectional MI block during ablation of persistent AF.

Molecular mechanism of a green-shifted, pH-dependent red fluorescent protein mKate variant.

Fluorescent proteins that can switch between distinct colors have contributed significantly to modern biomedical imaging technologies and molecular cell biology. Here we report the identification and biochemical analysis of a green-shifted red fluorescent protein variant GmKate, produced by the introduction of two mutations into mKate. Although the mutations decrease the overall brightness of the protein, GmKate is subject to pH-dependent, reversible green-to-red color conversion. At physiological pH, GmKate absorbs blue light (445 nm) and emits green fluorescence (525 nm). At pH above 9.0, GmKate absorbs 598 nm light and emits 646 nm, far-red fluorescence, similar to its sequence homolog mNeptune. Based on optical spectra and crystal structures of GmKate in its green and red states, the reversible color transition is attributed to the different protonation states of the cis-chromophore, an interpretation that was confirmed by quantum chemical calculations. Crystal structures reveal potential hydrogen bond networks around the chromophore that may facilitate the protonation switch, and indicate a molecular basis for the unusual bathochromic shift observed at high pH. This study provides mechanistic insights into the color tuning of mKate variants, which may aid the development of green-to-red color-convertible fluorescent sensors, and suggests GmKate as a prototype of genetically encoded pH sensors for biological studies.