A calibration method for patient specific IMRT QA using a single therapy verification film.

AIM: The aim of the present study is to develop and verify the single film calibration procedure used in intensity-modulated radiation therapy (IMRT) quality assurance. BACKGROUND: Radiographic films have been regularly used in routine commissioning of treatment modalities and verification of treatment planning system (TPS). The radiation dosimetery based on radiographic films has ability to give absolute two-dimension dose distribution and prefer for the IMRT quality assurance. However, the single therapy verification film gives a quick and significant reliable method for IMRT verification. MATERIALS AND METHODS: A single extended dose rate (EDR 2) film was used to generate the sensitometric curve of film optical density and radiation dose. EDR 2 film was exposed with nine 6 cm × 6 cm fields of 6 MV photon beam obtained from a medical linear accelerator at 5-cm depth in solid water phantom. The nine regions of single film were exposed with radiation doses raging from 10 to 362 cGy. The actual dose measurements inside the field regions were performed using 0.6 cm(3) ionization chamber. The exposed film was processed after irradiation using a VIDAR film scanner and the value of optical density was noted for each region. Ten IMRT plans of head and neck carcinoma were used for verification using a dynamic IMRT technique, and evaluated using the gamma index method with TPS calculated dose distribution. RESULTS: Sensitometric curve has been generated using a single film exposed at nine field region to check quantitative dose verifications of IMRT treatments. The radiation scattered factor was observed to decrease exponentially with the increase in the distance from the centre of each field region. The IMRT plans based on calibration curve were verified using the gamma index method and found to be within acceptable criteria. CONCLUSION: The single film method proved to be superior to the traditional calibration method and produce fast daily film calibration for highly accurate IMRT verification.

Effects of Thermal Annealing Duration on the Film Morphology of Methylamine Lead Triiodide (MAPbI3) Perovskite Thin Films in Ambient Air.

In the present communication we have studied the effect of thermal annealing duration on morphology of methylamine lead triiodide (MAPbI3) perovskite (prepared using single step method) semiconductor that changes into lead iodide (PbI2). Furthermore, the effect of annealing duration on thin films is investigated and correlated with its potential photovoltaic application. Thin films characteristics study by X-ray diffraction and scanning electron microscopy results indicate MAPbI3 degraded strongly by annealing duration. However, thin films (about 1.25 micron-thick) annealed at 80 °C for 10 min in ambient conditions cause minimum degradation with smooth and uniform surface morphology. It also shows a higher absorption coefficient with the band gap of °1.5 eV rendering this perovskite suitable for practical applications.

Dosimetric study of beam angle optimization in intensity-modulated radiation therapy planning.

PURPOSE: The quality of intensity-modulated radiotherapy (IMRT) highly depends on the choice of beam orientations and optimization algorithms used in the treatment planning. The present work reports dosimetric study of IMRT plans generated using preselected equiangular beam orientations (PSBO) and beam angle optimization (BAO) for the patients of prostate, head and neck, and esophagus carcinoma. MATERIALS AND METHODS: The computed tomography (CT) datasets of 30 patients treated with IMRT for prostate, head and neck, and esophagus carcinoma were selected. Two IMRT plans were made for each patient. First plan was prepared for seven to nine fields PSBO in coplanar arrangement. The second plan was made using the BAO by a computerized algorithm compatible treatment planning system (TPS). The dose-volume histograms (DVHs) of PSBO and BAO plans were compared for all the patients. The treatment plans were compared using the parameters delivered monitor units (MUs), doses delivered to organs at risk (OARs), target coverage (conformity index (CI)), homogeneity index (HI), and quality index (QI). RESULTS: DVHs generated showed that OARs receive almost identical or slightly better doses in case of BAO as compared to PSBO. CI, HI, and QI values were almost same for two plans. However, we have noticed significant reduction in MUs for all the plans generated using BAO. CONCLUSIONS: It is concluded that BAO provides superior plan with respect to MUs and should be used whenever possible in IMRT planning.

Total parenteral nutrition and cholestasis.

Hepatobiliary dysfunction is recognized as a major adverse effect of total parenteral nutrition (TPN). It is unknown if this is caused by a deficiency or toxicity of the TPN solution or the underlying pathophysiology of disease processes that require TPN therapy. This article presents algorithms for evaluating abnormal liver tests in patients on TPN and discusses treatment options and the current status of intestinal transplantation.

Biocompatible nanoparticle labeling of stem cells and their distribution in brain.

Nanolabeling is an invaluable novel technique in biology to detect and characterize different parts of biological systems including microscopic entities, viz., cells inside the living systems. Stem cells (SCs) are multipotent cells with the potential to differentiate into bone, cartilage, fat, muscle cells, and neurons and are being investigated for their utility in cell-based transplantation therapy. Yet, adequate methods to track transplanted SCs in vivo are limited, precluding functional studies. Nanoparticles (quantum dots) offer an alternative to organic dyes and fluorescent proteins to label and track cells in vitro and in vivo. These nanoparticles are resistant to chemical and metabolic degradation, demonstrating long-term photo stability. Here, we describe the technology of labeling the stem cells with silver nitrate nanoparticles in an in vitro coculture model. This is followed by defining the procedure of administering these cells in vivo and studying the distribution pattern and resultant regenerative effects of the "tagged" stem cells.

Peroxyl radical-mediated hemolysis: role of lipid, protein and sulfhydryl oxidation.

The objective of this study was to define the relationship between peroxyl radical-mediated cytotoxicity and lipid, protein and sulfhydryl oxidation using human erythrocytes as the target mammalian cell. We found that incubation of human erythrocytes with the peroxyl radical generator 2,2' azobis (2-amidinopropane) hydrochloride (AAPH) resulted in a time and dose-dependent increase in hemolysis such that at 50 mM AAPH maximum hemolysis was achieved at 120 min. Hemolysis was inhibited by hypoxia and by the addition of certain water soluble free radical scavengers such as 5-aminosalicylic acid (5-ASA), 4-ASA, N-acetyl-5-ASA and dimethyl thiourea. Peroxyl radical-mediated hemolysis did not appear to involve significant peroxidation of erythrocyte lipids nor did they enhance protein oxidation at times preceding hemolysis. Peroxyl radicals did however, significantly reduce by approximately 80% the intracellular levels of GSH and inhibit by approximately 90% erythrocyte Ca(2+)-Mg2+ ATPase activity at times preceding the hemolytic event. Our data as well as others suggest that extracellular oxidants promote the oxidation of intracellular compounds by interacting with certain redox active membrane components. Depletion of intracellular GSH stores using diamide did not result in hemolysis suggesting that oxidation of GSH alone does not promote hemolysis. Taken together, our data suggest that neither GSH oxidation, lipid peroxidation nor protein oxidation alone can account for peroxyl radical-mediated hemolysis. It remains to be determined whether free radical-mediated inactivation of Ca(2+)-Mg2+ ATPase is an important mechanism in this process.

Splenosis presenting as an ulcerated gastric mass: endoscopic and endoscopic ultrasonographic imaging.

A case of an ulcerated gastric wall mass ultimately found to be splenosis is presented in which the index patient had endoscopic and endoscopic ultrasonographic evaluation prior to resection. Although no visual features identified this mass as a splenic implant preoperatively, the lesion appeared to be atypical for leiomyoma, which led to surgical intervention. The role of endoscopic ultrasonography in assessing isolated gastric masses is discussed.

Prooxidant properties of 5-aminosalicylic acid. Possible mechanism for its adverse side effects.

There is a growing body of experimental and clinical evidence to suggest that oral or rectal administration of 5-ASA or 5-ASA conjugates is associated with significant adverse side effects including pancreatitis, hepatitis, and renal toxicity. The objective of this study was to assess the ability of 5-ASA to interact with low-molecular-weight iron to yield oxygen-derived free radicals and to determine whether these oxidants could damage model biological compounds. We found that 5-ASA was very effective at chelating ferric iron (Fe3+), and it rapidly reduced Fe3+ to the ferrous form (Fe2+). Addition of the 5-ASA/Fe2+ chelate to solutions containing polyunsaturated fatty acids or deoxyribose resulted in lipid peroxidation and oxidative carbohydrate degradation, respectively. These results are consistent with the formation of the highly reactive (and cytotoxic) hydroxyl radical. Formation of this free radical species was confirmed by the ability of hydroxyl radical scavengers (dimethyl sulfoxide, dimethyl thiourea) to inhibit the 5-ASA/Fe-mediated oxidative reactions. Maximum hydroxyl radical formation was achieved at a 5-ASA-to-Fe3+ ratio of 1.0 (20 microM 5-ASA and 20 microM Fe3+). Increasing this ratio significantly inhibited OH. formation with a concomitant reduction in lipid peroxidation and deoxyribose degradation. Finally, we demonstrated that 5-ASA promotes the reductive release of Fe3+ from ferritin. Data obtained in this study suggest that 5-ASA may, under certain conditions, promote the formation of potentially injurious free radical species. These oxidative reactions may contribute to some of the adverse side effects known to be associated with the newer preparations of 5-ASA.