How dangerous is low level radiation?

Molecular docking studies of Traditional Chinese Medicinal compounds against known protein targets to treat non-small cell lung carcinomas

In silico drug design using virtual screening, absorption, distribution, metabolism and excretion (ADME)/Tox data analysis, automated docking and molecular dynamics simulations for the determination of lead compounds for further in vitro analysis is a cost effective strategy. The present study used this strategy to discover novel lead compounds from an in-house database of Traditional Chinese Medicinal (TCM) compounds against epithelial growth factor receptor (EGFR) protein for targeting non-small cell lung cancer (NSCLC). After virtual screening of an initial dataset of 2,242 TCM compounds, leads were identified based on binding energy and ADME/Tox data and subjected to automated docking followed by molecular dynamics simulation. Triptolide, a top compound identified by this vigorous in silico screening, was then tested in vitro on the H2347 cell line carrying wild-type EGFR, revealing an anti-proliferative potency similar to that of known drugs against NSCLC.

Is bad luck the main cause of cancer?

A recent study reports that the log lifetime incidence rate across a selection of 31 cancer types is highly correlated with the log of the estimated tissue-specific lifetime number of stem cell divisions. This observation, which underscores the importance of errors in DNA replication, has been viewed as implying that most cancers arise through unavoidable bad luck, leading to the suggestion that research efforts should focus on early detection, rather than etiology or prevention. We argue that three statistical issues can, if ignored, lead analysts to incorrect conclusions. Statistics for traffic fatalities across the United States provide an example to demonstrate those inferential pitfalls. While the contribution of random cellular events to disease is often underappreciated, the role of chance is necessarily difficult to quantify. The conclusion that most cases of cancer are fundamentally unpreventable because they are the result of chance is unwarranted.

Partial volume characteristics of ionization chambers in kilovoltage x-ray exposure measurements

The partial volume (spatial) response of four ionization chambers (Keithley) in kilovoltage X-ray beams, generated by the Philips Super 80CP X-ray unit, was assessed. The volume of the ionization chambers were of 10 cm3, 15 cm3, 150 cm3, and 600 cm3 used with Keithley electrometer Model 35040. The beam output was measured using a monitor chamber (Radcal 6.0 cm3) placed close to the collimator. The source to chamber distance was kept constant at 1 m. For the measurement of the response of ionization chambers of 15 cm3, 150 cm3, and 600 cm3, a slit of 2.0 mm width was made in a lead sheet of 3.2 mm thick and size of 30 × 30 cm2 and was placed on the ionization chamber. The measurements were made for 81 kVp, 400 mA, and 0.25 s and the slit was moved at an increment of 2.0 mm over the entire length of the chamber. For the measurements of the ionization chamber of 10 cm3 (CT chamber), the beams of 120 kVp, 200 mA and 0.2 s were generated, and a slit of 5 mm width was made in a similar lead sheet that was moved at an increment of 5.0 mm. From the result it appears that the sensitive volumes of the ionization chambers affect the response of the ionization chamber to incident radiation.

Anti-inflammatory effects of low-dose radiotherapy. Indications, dose, and radiobiological mechanisms involved

Low-dose radiotherapy (LD-RT) has been used for several benign diseases, including arthrodegenerative and inflammatory pathologies. Despite its effectiveness in clinical practice, little is known about the mechanisms through which LD-RT modulates the various phases of the inflammatory response and about the optimal dose fractionation. The objective of this review is to deepen knowledge about the most effective LD-RT treatment schedule and radiobiological mechanisms underlying the anti-inflammatory effects of LD-RT in various in vitro experiments, in vivo studies, and clinical studies.

Lung cancer: epidemiology, etiology, and prevention

Lung cancer is the leading cause of cancer death in the United States and around the world. A vast majority of lung cancer deaths are attributable to cigarette smoking, and curbing the rates of cigarette smoking is imperative. Understanding the epidemiology and causal factors of lung cancer can provide additional foundation for disease prevention. This article focuses on modifiable risk factors, including tobacco smoking, occupational carcinogens, diet, and ionizing radiation. It also discusses briefly the molecular and genetic aspects of lung carcinogenesis.

Lung cancer: epidemiology, etiology, and prevention

Lung cancer is the leading cause of cancer death in the United States and around the world. A vast majority of lung cancer deaths are attributable to cigarette smoking, and curbing the rates of cigarette smoking is imperative. Understanding the epidemiology and causal factors of lung cancer can provide additional foundation for disease prevention. This article focuses on modifiable risk factors, including tobacco smoking, occupational carcinogens, diet, and ionizing radiation. It also discusses briefly the molecular and genetic aspects of lung carcinogenesis.

A contribution to the linear no-threshold discussion

The paper approaches the linear no-threshold (LNT) hypothesis, currently used as the basis for recommendations in radiological protection, from the point of view of the radiation mechanism. All considerations of the validity of the LNT hypothesis based on experiment or epidemiology are dismissed because of the impossibility of deriving statistically significant data at very low doses. Instead, the LNT hypothesis is assessed from a consideration of the mechanism of radiation action. The DNA double-strand break is proposed to be the crucial radiation-induced molecular lesion. A trace is made using a series of correlations that link the DNA double-strand break to effects at the cellular level and these cellular effects are linked to the induction of cancer. Multistep modelling of carcinogenesis is used to take the link through to a consideration of radiation risk. It is concluded that, from the point of view of radiation mechanism, at very low doses the LNT hypothesis of radiation action is valid, that is, the risk function has a positive slope from zero dose.

Optimum dental radiography in bone marrow transplant patients

OBJECTIVE

The purpose of this study was to establish an optimum radiographic examination regimen for patients undergoing bone marrow transplantation. Two radiographic examinations were compared: the panoramic radiograph and the full mouth series of radiographs.

STUDY DESIGN

A prospective analysis of 65 consecutive patients undergoing bone marrow transplantation was undertaken. All patients were examined through use of both panoramic and full mouth series intraoral radiographs, including bitewings. Significant findings were recorded and compared by means of paired t test analysis for parametric data, such as caries, periapical inflammation and subgingival calculus, and by means of McNemar's test for nonparametric data, such as the presence or absence of severe periodontal disease.

RESULTS

Acquired findings, such as caries, periodontal disease, and clinically significant faulty restorations, were detected more frequently from the full mouth series (P < .05). There was no significant difference in the detection of periapical pathosis. In 8 of 65 patients, clinically significant information, such as evidence of impacted wisdom teeth, neoplasms, and multiple myeloma, was better detected from the panoramic radiographs.

CONCLUSIONS

The results suggest a combination of both modalities as the optimum means of radiologic survey in this "high-risk" patient population.

Modeling radioprotective mechanisms in the dose effect relation at low doses and low dose rates of ionizing radiation

A new model (Random Coincidence Model--Radiation Adapted (RCM-RA)) is proposed which explains a possible pseudo threshold for stochastic radiation effects. It describes the formation of cancer in the case of multistep fixation of lesions in the critical regions of tumor associated genes such as proto-oncogenes or tumor-suppressor genes. The RCM-RA contains two different possibilities of DNA damage to complementary nucleotides. The damage may be caused either by radiation or by natural processes such as cellular radicals or thermal damage or by chemical cytotoxins. The model is based on the premise that radiation initially is bionegative, damaging organisms at their different levels of organization. The radiation, however, also induces various cellular radioprotective mechanisms which decrease the damage by natural processes. Considering both effects together, the theory explains apparent thresholds in the dose-response relation for radiation carcinogenesis without contradiction to the classical assumption that radiation is predominantly bionegative at doses typically found in occupational exposures.

Ion recombination and polarity effect of ionization chambers in kilovoltage x-ray exposure measurements

Exposure measurements with ionization chambers are dependent on the correction factors related to the beam energy (ke), temperature and pressure (ktp), ionization recombination (Pion), and polarity (kpol) effects. In this work, six different chambers commonly used in diagnostic radiology were investigated for the Pion and kpol at various exposure rates by changing the tube voltage, beam current, exposure time, and distance. A special triaxial connector was used to connect chambers to an electrometer capable of measuring positive and negative polarity and 150 V and 300 V electrode potentials to measure the kpol and Pion, respectively. A mammography unit (24-35 kVp) and a diagnostic x-ray unit (60-125 kVp) were used. Results indicate that the magnitude of the Pion is linearly dependent on kVp for large volume (> 150 cm3) chambers and independent for small volume (< or = 150 cm3) chambers. In general, Pion is higher at higher exposures (increasing kVp, mAs, and decreasing distance); however, kpol is independent of exposure rate and kVp, but strongly depends on the sensitive volume of an ion chamber. Pion and kpol vary between 1-48% and 1-16%, respectively, among various chambers and exposure conditions. Chambers with larger volumes have higher values of Pion and kpol. The desired accuracy of +/- 5% in exposure measurements might not be feasible unless both the polarity and recombination effects are known and accounted accurately.