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Four terarylenes having thieno[b]thiophene moieties with highly efficient intermolecular cascade ring opening reactivities have been synthesized.

This paper aimed to investigate effects of different tube voltage and image quality settings on radiation dose and image quality for patients undergoing computed tomography iodinated contrast studies using automatic tube current modulation system and to recommend settings to achieve improved radiation dose and image quality values. A Pagoda phantom with an additional rod of iodine contrast was scanned using different tube voltages and noise index (NI) settings. Size-specific dose estimate (SSDE) and image quality (noise, contrast, contrast-to-noise ratio (CNR) and figure of merit (FOM)) were analysed. Values of SSDE were maintained with similar NI settings. Contrast and CNR were higher for lower tube voltage settings. Better FOM values can be achieved with higher NI settings with the lower kVs. To achieve better CNR and SSDE compared with the standard setting of 120 kV, a 80 kV with an NI setting of 15 was recommended.

The volumetric computed tomography (CT) dose index (CTDIvol) is the measure of output displayed on CT consoles relating to dose within a standard phantom. This gives a false impression of doses levels within the tissues of smaller patients in Southeast Asia. A size-specific dose estimate (SSDE) can be calculated from the CTDIvol to provide an assessment of doses at specific positions within a scan using size-specific conversion factors. SSDE is derived using the water equivalent diameter (D w) of the patient, but calculation of D w requires sophisticated computer software. This study aimed to evaluate relationships between D W and effective diameter (D Eff), which can be measured more readily, in order to estimate SSDE at various positions within a routine clinical abdomen and pelvis CT examination for Thai patients. An in-house ImageJ algorithm was developed to measure D w, effective diameter (D Eff), and SSDE on CT slices located at the heart, liver, kidneys, colon, and bladder, on 181 CT examinations of abdomen and pelvis. Relationships between D Eff and D w were determined, and values of organ absorbed dose using D Eff were estimated. This approach was validated using a second cohort of 54 patients scanned on a different CT scanner. The results revealed that ratios between D Eff and D w at the heart level were 1.11–1.13 and those for the others were about 1.00. Additionally, the SSDE/CTDIvol ratio was estimated for each organ in terms of exponential functions using the relationships between D w and D Eff for individual organs. In summary, this study proposed a simple method for estimation of organ absorbed doses for Southeast Asian patients undergoing abdomen and pelvis CT examinations where sophisticated computer software is not available.

Purpose The effects of tube potential selection with a Computed Tomography (CT) Automatic Tube Current Modulation (ATCM) system on radiation dose and image quality have been investigated on a Canon CT scanner. The use of different values of tube voltage for imaging and the appropriate settings of the ATCM system were evaluated. Methods The custom made phantom consisted of three sections of different size with inserts of various materials. It was scanned using tube potentials of 80-140 kV and different image quality ATCM settings. CTDIvol and image quality in terms of noise, contrast, and contrast to noise ratio (CNR) for air, Polyethylene (PE), Acrylic, Polyoxymethylene (POM) and Polyvinylchloride (PVC) were analysed. A figure of merit (FOM) was estimated by combining CNR and CTDIvol. Results CTDIvol values were similar for all values of tube voltage and individual image quality ATCM settings when tube current was not restricted by the maximum value. The contrasts were independent of ATCM image quality setting, but CNR increased at the higher image quality level as image noise decreased. Both contrast and CNR decreased with increasing tube voltage for PVC and PE, but increased for POM and Acrylic. PVC was only insert material for which there was a significant improvement in contrast at lower tube potentials. Conclusions FOM indicated that Standard (SD=10) and Low dose (SD=12.5) ATCM settings might be appropriate. The optimum tube voltage settings for imaging the PVC was 80 kV-100 kV, but not for the lower contrast POM and Acrylic, for which the standard tube voltage setting of 120 kV was better. Tube potential should be carefully set to gain radiological protection optimization and keep radiation dose as low as possible. Results indicate 100 kV is likely to be appropriate for imaging small and medium sized Thai patients when iodine contrast is used.

Background Contrast-induced nephropathy (CIN) is an adverse reaction associated with the use of intravenous contrast media (CM). Purpose To investigate the impact of low tube voltage settings on single-energy computed tomography (SECT) and rapid kV switching dual-energy CT (DECT) with reduced concentrations of iodinated CM. Material and Methods A phantom containing four different concentrations of CM (original concentration CM, 20%, 40%, and 60% reductions) was scanned using SECT mode with varying tube voltages (70, 80, 100, and 120 kVp) and DECT mode through reconstructing monoenergetic energy (50 keV and 70 keV) images. ATCM system with different noise index (NI) settings were set, and the images were reconstructed using ASiR-V. Image quality were measured for individual phantom sizes and protocols and compared to a reference protocol for SECT of 120 kVp, NI = 18, threshold contrast enhancement ≥280 HU, and CNR ≥17. Results Tube voltage settings of 70 kVp together with 40% reduction in the iodinated CM is suitable for small phantom size, those of 80 kVp and 20% reduction is suitable for the medium and large sizes. This allows radiation doses to be reduced by 12%–30%. Values of CNR and contrast for DECT are better than those for SECT with the same NI setting. Conclusion Diagnostic reference of image quality can be maintained by using SECT with lower tube voltage and DECT with reductions of iodinated CM concentration and radiation dose. Therefore, the NI setting can be increased when DECT is used to achieve a similar image quality.

This study aimed to evaluate the relationship between the brain absorbed dose and personal dosimetry readings in interventional cardiologists. Interventional procedures were replicated using Monte Carlo simulations (MCNP 6) with anthropomorphic phantoms representing both operator and patient. Absorbed doses were evaluated for 10 predefined regions of the operator’s brain as well as for dosemeters at chest and neck level. One beam quality (HVL = 6.2 mm Al) and nine beam projections were considered. A significant bias in the laterality of brain dose was found with doses at the left side of the brain being up to 2.8 times higher compared with the right. The correlation between brain dose and dosemeter reading was found to be dependent on beam projection. Yet, a generalized conversion factor (brain dose normalized by Hp(10)), averaged over all considered beam projections, could be proposed for (retrospective) brain dose estimation from routinely measured dosimetry data.

Volume averaged CT dose index (CTDIvol) is an important dose index utilized for CT dosimetry. Measurements of CTDIvol are performed in reference cylindrical phantoms of specified diameters. A size-specific dose estimate (SSDE) has been recommended for assessment of doses delivered to individual patients. Evaluation of the SSDE requires the size of the scanned region of the patient to be estimated in terms of water-equivalent diameter (Dw) to allow calculation of a dose value appropriate for the patient. Estimation of Dw, however, may be challenging and time consuming as it requires assessment of Dw for each slice within the scanned region. A study has been carried out to investigate the suitability of using Dw,mid for a single slice at the middle of the scanned region to estimate a value of Dw,mean to apply to all slices. 351 phantoms (158 paediatric and 193 adult) developed from reconstructed CT images of patients were employed. Six scan regions were studied: chest, abdomen, pelvis, chest and abdomen, abdomen and pelvis, and the whole trunk. Results show that the use of Dw,mid can lead to over or underestimation of Dw,mean by up to 13% for paediatric and adult patients. SSDE values based on Dw,mid and Dw,mean were assessed for each phantom, and a linear regression analysis was performed. Use of the analysis could provide a simple and practical approach to assessing SSDE for a given scan based on Dw,mid with the root-mean-square errors estimated to be in the range of 1.2%–4.0% for paediatric and 1.2%–5.9% for adults.

Over recent years, an increasing number of fluoroscopically guided interventions (FGIs) have been performed by radiologists and non-radiologists. Also, the number of complex interventional procedures has increased. In the late nineties, first reports of skin injuries appeared in the literature. The medical community responded through increased awareness for radiation protection and public authorities by recommendations and legislation, for example, the European Basic Safety Standards (EU-BSS) which were published in 2014, or the international Basic Safety Standards (BSS). Implementation of the EU-BSS requires concerted action from interventionalists, radiographers, medical physics experts and competent national authorities. Interventionalists should play an important role in this project since implementation of the EU-BSS will affect their daily practice. This paper discusses some important issues of the EU-BSS such as unintended and accidental radiation exposures of patients, the meaning of significant dose events and how to deal with patients who were exposed to a substantial radiation dose with the risk of tissue injuries. In addition, this paper provides practical advice on how to implement alert and trigger levels in daily practice of FGIs in order to increase patient safety.

Five photochromic terarylenes which show reversible photocyclisation and cycloreversion with relatively high quantum yields are presented. Some of these have been observed to undergo a highly efficient cycloreversion cascade process from their coloured, closed forms to their uncoloured open forms that leads to cycloreversion quantum yields significantly larger than unity. This cascade effect can been induced with both chemical and X-ray initiation; the limit of detection from X-ray initiation has been tested and is comparable to existing systems with detection observed at values as low as 0.3 mGy., New photochromic terarylene displays extremely high photosensitivity with quantum yield as high as 3300% and radio-sensitivity to X-ray dose as weak as 0.3 mGy.

We present here a new photo-active molecule which acts as a photo-Lewis acid generator (PLAG) based on photo-chemical 6π-percyclization. Photo-illumination of the PLAG molecule produces a condensed aromatic carbocation with a triflate counteranion, which exhibits Lewis acid chemical catalytic reactivity such as initiation of the polymerization of epoxy monomers and catalysis of Mukaiyama-aldol reactions. The terminal-end structure in the epoxy polymerization was modified with the Lewis acid fragment. The carbocation induced the Mukaiyama-aldol reaction as a new photo-gated system with remarkably high catalytic reactivity and turnover numbers higher than 60. The photo-chemical quantum yield of the carbocation generation is 50%, which is considerably higher than obtained with most Bronsted photo-acid generators.

Medical radiation accidents and unintended events may lead to accidental or unintended medical exposure of patients and exposure of staff or the public. Most unintended exposures in nuclear medicine will lead to a small increase in risk; nevertheless, these require investigation and a clinical and dosimetric assessment. Nuclear medicine staff are exposed to radiation emitted directly by radiopharmaceuticals and by patients after administration of radiopharmaceuticals. This is particularly relevant in PET, due to the penetrating 511 keV γ-rays. Dose constraints should be set for planning the exposure of individuals. Staff body doses of 1-25 µSv/GBq are reported for PET imaging, the largest component being from the injection. The preparation and administration of radiopharmaceuticals can lead to high doses to the hands, challenging dose limits for radionuclides such as

Potential risks from radiation exposure on the development of cardiovascular and cerebrovascular disease are indicated by epidemiological studies. Medical exposures give the largest dose to the population from artificial sources, with cumulative doses from multiple CT scans being significant. Data on doses from scans performed on 12 CT scanners in three hospitals over a period of 5½ years, derived using RadimetricsTM software, have been reviewed for 105 757 patients. Data have been downloaded for heart, brain, thyroid, and effective doses, and cumulative doses analysed using ExcelTM spreadsheets. 2.4% of patients having body CT scans received cumulative doses to the heart over 100 mSv, 9% of whom were under 50 years. 9.6% of patients having head CT scans received cumulative doses to the brain over 100 mSv with 0.08% over 500 mSv from whom 41% were under 50 years, but only 1.3% of patients scanned had thyroid/carotid artery doses over 100 mSv. An approximate evaluation of potential risks from exposures of the heart above 100 mSv and brain over 500 mSv for patients under 60 years would suggest that at most only one patient would demonstrate any excess risk from vascular disease resulting from the exposures. 0.67% of patients scanned received effective doses over 100 mSv, in line with results from European studies, with 8.4% being under 50 years. The application of age and sex specific risk coefficients relating to excess cancer incidence suggests that two or three patients with effective doses over 100 mSv and five patients with effective doses between 50 and 100 mSv, from those examined, might develop cancer as a result of exposure. However, this will be an overestimate, since it does not take patients’ health into account. Exposure management software can aid in evaluating cumulative doses and identifying individual patients receiving substantial doses from repetitive imaging.

Photochromic molecules display reversible isomerization reactions between two isomers accompanied by an exchange between heat and chemical potential. A considerable part of the absorbed light energy is stored in and released from the present E-type photochromic molecules, which undergo cyclization reactions under UV light excitation and backward reactions after application of oxidative stimuli. The photochromic nature, thermal stability, and cascade ring-opening reaction of the closed form isomers of eight photochromic terarylenes are studied, and energy storage efficiencies at a single wavelength, η, as high as 23% are experimentally demonstrated. Their efficient photochemical quantum yield for the cyclization reaction markedly contributes to the high energy storage efficiency as well as showing the capability of efficient cascade cycloreversion reactions. Spontaneous cycloreversion reactions are well-suppressed because the forbidden nature of the cycloreversion reaction gives rise to sufficient heat storage duration.

International audience; The synthesis of ruthenium complexes incorporating an overcrowded pentaarylcyclopentadienyl ligand has been investigated, and higher efficiency has been reached using chlorine-functionalised precursors when compared with their brominated counterparts. A new methodology for the preparation of chlorocyclopentadienes has been developed which is well adapted for highly sterically hindered compounds and works with either electron rich or poor systems.

The International Commission on Radiological Protection has recently published a report (ICRP Publication 147; Ann. ICRP 50, 2021) on the use of dose quantities in radiological protection, under the same authorship as this Memorandum. Here, we present a brief summary of the main elements of the report. ICRP Publication 147 consolidates and clarifies the explanations provided in the 2007 ICRP Recommendations (Publication 103) but reaches conclusions that go beyond those presented in Publication 103. Further guidance is provided on the scientific basis for the control of radiation risks using dose quantities in occupational, public and medical applications. It is emphasised that best estimates of risk to individuals will use organ/tissue absorbed doses, appropriate relative biological effectiveness factors and dose–risk models for specific health effects. However, bearing in mind uncertainties including those associated with risk projection to low doses or low dose rates, it is concluded that in the context of radiological protection, effective dose may be considered as an approximate indicator of possible risk of stochastic health effects following low-level exposure to ionising radiation. In this respect, it should also be recognised that lifetime cancer risks vary with age at exposure, sex and population group. The ICRP report also concludes that equivalent dose is not needed as a protection quantity. Dose limits for the avoidance of tissue reactions for the skin, hands and feet, and lens of the eye will be more appropriately set in terms of absorbed dose rather than equivalent dose.

Improvements in delivery of radiation dose to target tissues in radiotherapy have increased the need for better image quality and led to a higher frequency of imaging patients. Imaging for treatment planning extends to function and motion assessment and devices are incorporated into medical linear accelerators (linacs) so that regions of tissue can be imaged at time of treatment delivery to ensure dose distributions are delivered as accurately as possible. A survey of imaging in 97 radiotherapy centres in nine countries on six continents has been undertaken with an on-line questionnaire administered through the International Commission on Radiological Protection mentorship programme to provide a snapshot of imaging practices. Responses show that all centres use CT for planning treatments and many utilise additional information from magnetic resonance imaging and positron emission tomography scans. Most centres have kV cone beam CT attached to at least some linacs and use this for the majority of treatment fractions. The imaging options available declined with the human development index (HDI) of the country, and the frequency of imaging during treatment depended more on country than treatment site with countries having lower HDIs imaging less frequently. The country with the lowest HDI had few kV imaging facilities and relied on MV planar imaging intermittently during treatment. Imaging protocols supplied by vendors are used in most centres and under half adapt exposure conditions to individual patients. Recording of patient doses, a knowledge of which is important in optimisation of imaging protocols, was limited primarily to European countries.

The purposes of this study were to assess the effect of patient vertical miscentering on eye lens radiation doses in patients who have undergone head computed tomography (CT) and to measure the absorbed dose to the eye lens in health-care staff who remain in the CT room during the procedure. All measurements were performed in phantoms. Nanodot™ optically stimulated luminescence dosimeters were used to measure radiation doses. For the assessment of the effect of patient vertical miscentering, CT scans were obtained at six different table heights. The radiation doses in the eye lens of health-care staff received when working at three different locations in the CT room were measured. Correction coefficients were applied to determine equivalent dose, Hp(3), in the eye lens. The results revealed that the positioning of patients off the CT scan isocenter during head CT may result in a significantly increased eye lens dose. The phantom eye lens doses can be increased by 43.7% (70 mGy), and image noise increased when the table was 5 cm below the isocenter due to the effect of the bow tie filter and eyes being irradiated directly by the primary beam for a greater proportion of the tube rotation. An estimated eye lens dose of ≤0.1-0.2 mSv was found in phantoms simulating health-care staff, with the dose depending on positioning of the phantom. Health-care staff in the room during CT scans are at risk of a significant eye lens dose, particularly if positioned posterior to the gantry.

The International X-ray and Radium Protection Committee was established in 1928 in response to concerns about effects of radiation exposure observed in radiologists. By 1950 the field of radiological protection had broadened beyond medical radiology and the committee was renamed the International Commission on Radiological Protection (ICRP). ICRP prepares fundamental recommendations on radiological protection that are adopted as the basis for standards, legislation, guidelines, programmes, and practices world-wide. The structure of ICRP consists of a main commission with four sub-committees, number three being established in 1977 to deal with protection in medicine. Task groups working under the direction of the committees prepare reports setting out recommendations and guidance on radiological protection in different areas. ICRP has created protection dose quantities that relate to risk, such as effective dose, that can be used for dose planning and comparison purposes. Committee 3 prepares short, concise reports aimed at specific needs of the medical community to promote accessibility. These give advice relating to many aspects of radiotherapy, diagnostic and interventional radiology, and nuclear medicine. In parallel with this work, modelling of dose distributions has been undertaken to derive coefficients for calculating patient doses from a wide range of radiopharmaceuticals. All ICRP reports over 2 years old will be available free of charge from January 2020 to aid the dissemination of information on radiological protection and help the medical community to adjust to challenges presented by new radiation techniques.

The dose quantities displayed routinely on CT scanners, the volume averaged CT dose index (CTDIvol) and dose length product, provide measures of doses calculated for standard phantoms. The American Association of Medical Physics has published conversion factors for the adjustment of CTDIvol to take account of variations in patient size, the results being termed size-specific dose estimate (SSDE). However, CTDIvol and SSDE, while useful in comparing and optimising doses from a set procedure, do not provide risk-related information that takes account of the organs and tissues irradiated and associated cancer risks. A derivative of effective dose that takes account of differences in body and organ sizes and masses, referred to here as size-specific effective dose (SED), can provide such information. Data on organ doses from NCICT software that is based on Monte Carlo simulations of CT scans for 193 adult phantoms have been used to compute values of SED for CT examinations of the trunk and results compared with corresponding values of SSDE. Relationships within ±8% were observed between SED and SSDE for scans extending over similar regions for phantoms with a wide range of sizes. Coefficients have been derived from fits of the data to estimate SED values from SSDEs for different regions of the body for scans of standard lengths based on patient height. A method developed to take account of differences in scan length gave SED results within ±5% of values calculated using the NCI phantom library. This approach could potentially be used to estimate SED from SSDE values, allowing their display at the time a CT scan is performed.

A molecular motor that has been previously shown to rotate when fueled by electrons through a scanning tunneling microscope tip has been functionalized with a terarylene photochrome fragment on its rotating subunit. Photoisomerization has been performed under UV irradiation. Variable-temperature 1H NMR and UV-vis studies demonstrate the rotational motion and its braking action after photoisomerization. The braking action can be reversed by thermal heating. Once the rigid and planar closed form is obtained, the rotation is effectively slowed at lower temperature, making this new rotor a potential motor with an independent response to electrons and light.

The International Commission on Radiological Protection (ICRP) developed effective dose as a quantity related to risk for occupational and public exposure. There was a need for a similar dose quantity linked to risk for making everyday decisions relating to medical procedures. Coefficients were developed to enable the calculation of doses to organs and tissues, and effective doses for procedures in nuclear medicine and radiology during the 1980s and 1990s. Effective dose has provided a valuable tool that is now used in the establishment of guidelines for patient referral and justification of procedures, choice of appropriate imaging techniques, and providing dose data on potential exposure of volunteers for research studies, all of which require the benefits from the procedure to be weighed against the risks. However, the approximations made in the derivation of effective dose are often forgotten, and the uncertainties in calculations of risks are discussed. An ICRP report on protection dose quantities has been prepared that provides more information on the application of effective dose, and concludes that effective dose can be used as an approximate measure of possible risk. A discussion of the way in which it should be used is given here, with applications for which it is considered suitable. Approaches to the evaluation of risk and methods for conveying information on risk are also discussed.

Effective dose (E) has been developed by the International Commission on Radiological Protection (ICRP) as a dose quantity with a link to risks of health detriment, mainly cancer. It is based on reference phantoms representing average individuals, but this is often forgotten in its application to medical exposures, for which its use sometimes goes beyond the intended purpose. There has been much debate about issues involved in the use of E in medicine and ICRP is preparing a publication with more information on this application. This article aims to describe the development of E and explain how it should be used in medicine. It discusses some of the issues that arise when E is applied to medical exposures and provides information on how its use might evolve in the future. The article concludes with responses to some frequently asked questions about uses of E that are in line with the forthcoming ICRP publication. The main use of E in medicine is in meaningful comparison of doses from different types of procedure not possible with measurable dose quantities. However, it can be used, with appropriate care, as a measure of possible cancer risks. When considering E to individual patients, it is important to note that the dose received will differ from that assessed for reference phantoms, and the risk per Sv is likely to be greater on average in children and less in older adults. Newer techniques allow the calculation of patient-specific E which should be distinguished from the reference quantity.

International audience; The design and synthesis of a new family of nanocarsis reported. To control their motion, we integrated adipole which can be tuned thanks to strategic donor and acceptorsubstituents at the 5- and 15-positions of the porphyrinbackbone. The two other meso positions are substitutedwith ethynyltriptycene moieties which are known to act aswheels. Full characterization of nine nanocars is presentedas well as the electrochemistry of these push-pull molecules.DFT calculations allowed us to evaluate the magnitude ofthe dipoles and to understand the electrochemical behaviorand how it is affected by the electron donating and acceptinggroups present. An X-ray crystal structure of one nanocarhas also been obtained.

Automatic tube current modulation (ATCM) is now available on all computed tomography (CT) scanners, but there is no standard phantom for testing its operation. For this study, a phantom comprising five elliptical sections of varying diameters in the shape of a pagoda has been made to represent the range of sizes for patients in Thailand and the Far East. ATCM performance can be evaluated in terms of how tube current and image noise vary with changes in the sizes of the sections. Additional rods of different materials with similar properties to human tissues have been inserted to allow the measurement of contrast-to-noise ratios (CNRs) for assessment of image quality. The phantom has been used to test and compare the performance of CT ATCM systems for the major four CT scanner vendors. The results showed that the ATCM systems of Toshiba and GE CT scanners maintained image noise and CNR within narrower ranges by varying tube current aggressively along the scan length, and commencing modulation before the high attenuation sections are reached. In contrast, the ATCM systems of Philips and Siemens scanners adjusted the tube current within narrower ranges, allowed larger variations in image noise and CNR, and commenced modulation at the start of sections with higher attenuation. The phantom can be used to confirm functionality of the system for acceptance testing, as well as providing information on the tradeoff between radiation dose and image quality when setting up clinical protocols during commissioning of new CT scanners. The phantom can also be used on a routine basis to check that performance is maintained, and could be used in the future for selecting protocol settings to give required values of CNR or adjusting protocol settings on different CT scanners to provide similar levels of clinical performance.

The dose length product (DLP) provides a measurement related to energy imparted from a computed tomography (CT) scan. The DLP is based on the volume-averaged CT dose index (CTDI vol), which is designed for fan beams. The aims of this study were to investigate the use of DLP for scans with wide beams used in cone beam CT (DLP CBCT) in radiotherapy that would be analogous to the DLP of fan beam scans (DLP CT), and to compare the efficiencies of DLP CT and DLP CBCT in reporting the total energy imparted in patients. A validated Monte Carlo model of a kV imaging system integrated into a Varian TrueBeam linac was employed. The DLP CT was assessed by multiplying the CTDI vol for a 20 mm fan beam by scan length, and the DLP CBCT determined through multiplying the CTDI vol, estimated for wide beams using a correction factor based on free-in-air measurements, by the beam width. Two scan protocols for head and body were investigated for tube potentials between 80 and 140 kV and a range of scan lengths/widths. Efficiency values were estimated by normalising the DLP CT and DLP CBCT with respect to the corresponding dose profile integrals (DPIs), which were evaluated within 900 mm long phantoms. The results show that the DLP CBCT values were within 1% of those for DLP CT of similar length performed on the same system, and the efficiencies decrease with tube potential. However, whereas DLP values for fan beams are approximately proportional to scan length, those for wide beams decrease by ∼2% between beam widths of 20 and 320 mm. As a result, while the DLP CT efficiency is similar over all scan lengths, that for DLP CBCT increases slightly with beam width. The DLP CT and DLP CBCT underestimated the total energy imparted by comparable amounts with efficiencies within the range of 80-81% and 80-83% for the head scans, and 71-76% and 70-77% for the body scans, respectively. The results indicate that the DLP CBCT can be considered as an analogous dose index to the DLP CT. It could, therefore, be used for quantification of doses from imaging in radiotherapy and provide a valuable tool to aid optimisation.

The International Atomic Energy Agency issued a statement calling for action to strengthen the radiation protection of patients undergoing recurrent imaging. This followed reports of patients receiving cumulative effective doses over 100 mSv from multiple computed tomography examinations. In order to evaluate excess risks of cancer incidence among UK patients, data from an exposure management system covering three hospitals within one trust have been studied over 5½ years. Cumulative effective doses for 105 757 patients, from whom 719 (0.68%) received effective dose over 100 mSv, have been analysed using age and sex specific risk factors for stochastic effects. Two cancers might be expected to be initiated in the patients receiving over 100 mSv, while five might be expected to develop cancer among patients receiving 50–100 mSv. However, the calculations ignore health conditions for which the patients are being treated that may shorten their lives, and rely on the linear-no-threshold dose-effect model which is a subject of debate, so they are likely to overestimate cancer incidence. If health of the patients receiving >100 mSv is taken into account, the risk of mortality from cancer initiated by medical exposure might be the order of 1 in 2000. Recommendations on further strengthening of optimisation should be applied to imaging procedures for all patients with special focus on those performed on children and adolescents.

Terarylene frameworks containing benzothiazole as a photoprecursor of hydride donors are presented. We here report on two new scaffolds along with their photoreactivity in solution. Through use of selected external oxidants, the photogeneration of hydride donors is monitored using UV–visible, NMR, and TEM methods. As a proof-of-concept, photogeneration of hydride in the presence of Ag+ gave rise to the formation of Ag nanoparticles.

For multi-detector CT scans, the region of the body irradiated is determined from the scan projection radiograph and is adjusted for each patient. However, for cone beam CT scans, standard field sizes are often used without any adjustment for patient size. Moreover, when cone beam CT is used with image guided radiation therapy, the scan position varies with each patient, based on the tumour position and clinical requirements. The aim of this study is to quantify the influence of the position of the scan isocentre on doses to organs and tissues within the patient, and derive values of effective dose that might be used in optimization of imaging protocols. A previously validated Monte Carlo model of a Varian kV on-board-imager system was used to assess organ and effective doses for the International Commission on Radiological Protection adult male and female reference phantoms. The scan isocentre was shifted along the z-axis of the phantoms in increments of 2.4 cm, while keeping the x and y axes fixed to assess variations in dose. The phantoms were divided into four regions, namely head and neck, thorax, abdomen, and pelvis. Each region was scanned using the protocol with scan parameters applied in the clinic. The position of the scan isocentre plays a major role in determining the organ doses and effective dose for all regions studied. Nevertheless, values for average effective dose derived at the centre of a region of interest would be suitable for planning treatment regimens and making adjustments to scan protocols. If conversion coefficients based on measurements made at centre of an area of interest were used to evaluate organ doses for individuals, these could lead to significant over/underestimation. The impact of changes in scan position should be taken into consideration when deriving doses to the organs of a patient.

A study has been undertaken over a period of eight years of tissue reactions in interventional radiology patients receiving cumulative air kerma values to their scalp above 3 Gy. Patients receiving doses to the scalp above this trigger level have been followed up to determine when effects occur and to provide reassurance if they do. The study has shown that hair thinning and hair loss are the more likely effects and may occur in 50% of patients at dose above 4.5 Gy.

The reduction in the occupational dose limit of the eye lens has created the need for optimising eye protection and dose assessment, in particular for interventional clinicians. Lead glasses are one of the protection tools for shielding the eyes, but assessing the eye lens dose when these are in place remains challenging. In this study, we evaluated the impact of the position of H p (3) dosemeters on the estimated eye lens dose when lead glasses are used in interventional settings. Using the Monte Carlo method (MCNPX), an interventional cardiology setup was simulated for two models of lead glasses, five beam projections and two patient access routes. H p (3) dosemeters were placed at several positions on the operator and the obtained dose was compared to the dose to the sensitive part of the eye lens (H lens). Furthermore, to reproduce an experimental setup, a reference dosemeter, H p (3)ref, was placed on the surface of the eye. The dose measured by H p (3)ref was, on average, only 60% of H lens. Dosemeters placed on the glasses, under their shielding, underestimated H lens for all parameters considered, by from 10% up to 90%. Conversely, dosemeters placed on the head or on the glasses, over their shielding, overestimated H lens, on average, up to 60%. The presence or lack of side shielding in lead glasses affected mostly dosemeters placed on the forehead, at the left side. Results suggest that both use of a correction factor of 0.5 to account for the presence of lead glasses in doses measured outside their shielding and placing an eye lens dosemeter immediately beneath the lenses of lead glasses may lead to the underestimation of the eye lens dose. Most suitable positions for eye lens dose assessment were on the skin, unshielded by the glasses or close to the eye, with no correction to the dose measured.

No abstract available.

Cone-beam CT (CBCT) scans utilized for image guided radiation therapy (IGRT) procedures have become an essential part of radiotherapy. The aim of this study was to assess organ and effective doses resulting from new CBCT scan protocols (head, thorax, and pelvis) released with a software upgrade of the kV on-board-imager (OBI) system. Influence of the scan parameters that were changed in the new protocols on the patient dose was also investigated. Organ and effective doses for protocols of the new software (V2.5) and a previous version (V1.6) were assessed using Monte Carlo (MC) simulations for the International Commission on Radiological Protection (ICRP) adult male and female reference computational phantoms. The number of projections and the mAs values were increased and the size of the scan field was extended in the new protocols. Influence of these changes on organ and effective doses of the scans was investigated. The OBI system was modelled in EGSnrc/BEAMnrc, and organ doses were estimated using EGSnrc/DOSXYZnrc. The MC model was benchmarked against experimental measurements. Organ doses resulting from the V2.5 protocols were higher than those of V1.6 for organs that were partially or fully inside the scans fields, and increased by (3 to 13)%, (10 to 77)%, and (13 to 21)% for the head, thorax, and pelvis protocols for both phantoms, respectively. As a result, effective doses rose by 14%, 17%, and 16% for the male phantom, and 13%, 18%, and 17% for the female phantom for the three scan protocols, respectively. The scan field extension for the V2.5 protocols contributed significantly in the dose increases, especially for organs that were partially irradiated such as the thyroid in head and thorax scans and colon in the pelvic scan. The contribution of the mAs values and projection numbers was minimal in the dose increases, up to 2.5%. The field size extension plays a major role in improving the treatment output by including more markers in the field of view to match between CBCT and CT images and hence setting up the patient precisely. Therefore, a trade-off between the risk and benefits of CBCT scans should be considered, and the dose increases should be monitored. Several recommendations have been made for optimization of the patient dose involved for IGRT procedures.

– The International Commission on Radiological Protection (ICRP) first introduced the term ‘diagnostic reference level’ (DRL) in 1996 in Publication 73. The concept was subsequently developed further, and practical guidance was provided in 2001. The DRL has been proven to be an effective tool that aids in optimisation of protection in the medical exposure of patients for diagnostic and interventional procedures. However, with time, it has become evident that additional advice is needed. There are issues related to definitions of the terms used in previous guidance, determination of the values for DRLs, the appropriate interval for re-evaluating and updating these values, appropriate use of DRLs in clinical practice, methods for practical application of DRLs, and application of the DRL concept to newer imaging technologies. This publication is intended as a further source of information and guidance on these issues. Some terminology has been clarified. In addition, this publication recommends quantities for use as DRLs for various imaging modalities, and provides information on the use of DRLs for interventional procedures and in paediatric imaging. It suggests modifications in the conduct of DRL surveys that take advantage of automated reporting of radiation-dose-related quantities, and highlights the importance of including information on DRLs in training programmes for healthcare workers. The target audience for this publication is national, regional, and local authorities; professional societies; and facilities that use ionising radiation for medical purposes, and responsible staff within these facilities. A full set of the Commission’s recommendations is provided.

In 2012 IRPA established a task group (TG) to identify key issues in the implementation of the revised eye lens dose limit. The TG reported its conclusions in 2013. In January 2015, IRPA asked the TG to review progress with the implementation of the recommendations from the early report and to collate current practitioner experience. This report presents the results of a survey on the view of the IRPA professionals on the new limit to the lens of the eye and on the wider issue of tissue reactions. Recommendations derived from the survey are presented. This report was approved by IRPA Executive Council on 31 January 2017.

This paper sets out guidelines for managing radiation exposure incidents involving patients in diagnostic and interventional radiology. The work is based on collation of experiences from representatives of international and national organizations for radiologists, medical physicists, radiographers, regulators, and equipment manufacturers, derived from an International Atomic Energy Agency Technical Meeting. More serious overexposures can result in skin doses high enough to produce tissue reactions, in interventional procedures and computed tomography, most notably from perfusion studies. A major factor involved has been deficiencies in training of staff in operation of equipment and optimization techniques. The use of checklists and time outs before procedures commence, and dose alerts when critical levels are reached during procedures, can provide safeguards to reduce the risks of these effects occurring. However, unintended and accidental overexposures resulting in relatively small additional doses can take place in any diagnostic or interventional x-ray procedure and it is important to learn from errors that occur, as these may lead to increased risks of stochastic effects. Such events may involve the wrong examinations, procedural errors, or equipment faults. Guidance is given on prevention, investigation, and dose calculation for radiology exposure incidents within healthcare facilities. Responsibilities should be clearly set out in formal policies, and procedures should be in place to ensure that root causes are identified and deficiencies addressed. When an overexposure of a patient or an unintended exposure of a foetus occurs, the foetal, organ, skin, and/or effective dose may be estimated from exposure data. When doses are very low, generic values for the examination may be sufficient, but a full assessment of doses to all exposed organs and tissues may sometimes be required. The use of general terminology to describe risks from stochastic effects is recommended rather than the calculation of numerical values, as these are misleading when applied to individuals.

Nuclear medicine (NM) procedures for diagnosis and treatment of disease are performed routinely in hospitals throughout the world. These involve preparation and administration to patients of pharmaceuticals labelled with radioactive material. The International Atomic Energy Agency (IAEA) and the World Health Organisation highlighted the need for improvement in prevention of medical radiation incidents and accidents in the Bonn Call-for-Action in 2012. An IAEA Technical Meeting was held on prevention of unintended exposures and accidents in NM in 2018 to address the issue. Exposures can take place at any time when radioactive material is being produced and used, and the risk continues after procedures have been completed. Thus there is potential for staff or members of the general public to be exposed, as well as patients. This paper sets out guidelines for incident prevention based on presentations and discussions at the meeting, and review of reports from the literature. It deals with potential incidents in in-house radionuclide production, radiopharmaceutical preparation, administration to patients, and following a procedure, as well as aspects in management of radioactive materials. Special attention has been paid to therapeutic procedures, as these have the potential to cause more harm to patients from erroneous administrations, including tissue reactions from extravasation of radiopharmaceutical, and could lead to significant contamination events. Administration of NM therapy is generally contraindicated in pregnancy. Identification of any patient who may be pregnant is crucial and it might be necessary to verify this with a pregnancy test for patients within the age band considered to be fertile. Inclusion of NM therapy incidents in the IAEA automated reporting system SAFRON is recommended. In summary, the paper aims to highlight errors that could occur during different phases of NM procedures in order to aid prevention of incidents. The value of periodic audit in evaluating systems in place on a regular basis is emphasised. Approaches to incident investigation and follow-up are described, and the need to ensure corrective action is taken to address any deficiencies stressed.

Organ doses for patients having CT scans can be assessed using Monte Carlo simulations, but this would require significant computing power if carried out for every patient. An alternative method is to use scanner-independent dose conversion coefficients (DCCs) to estimate organ doses. DCCs, calculated by normalizing organ doses with respect to the corresponding CTDIvol, have been developed based on patient size, in terms of patient perimeter or effective diameter (ED) in the region of interest (ROI). However, patient dimensions do not take account of x-ray attenuation within the patient, which will affect the accuracy of dose assessment, as the attenuations of tissues are different for each patient. The aim of this study was to develop size-specific and scanner-independent DCCs by quantifying patient size in terms of water-equivalent diameter (Dw). A library of 370 anatomical paediatric and adult phantoms was used. An algorithm was developed on MATLAB version 2015b to calculate Dw values for each phantom over six scan regions in the trunk. Organ doses and CTDIvol resulting from body scans acquired with 120 kVp were assessed using NCICT software for the phantom library to obtain DCCs. Good correlations were obtained between Dw as a measure for patient size and the DCCs, for which R2 values of correlations were above 0.92 for the majority of organs. These could provide better assessments of organ doses than ones based on patient dimensions. Comparisons of lung doses from scans of different regions assessed using NCICT software and DCCs showed that values based on Dw values gave lower variations in dose by up to 12% compared to those based on ED. The correlations could potentially be utilized to assess organ doses for patients undergoing scans with any CT scanner. This would simplify organ dose estimation for patients and overcome the limitations associated with Monte Carlo simulations.

The size-specific dose estimate (SSDE) concept is based on converting volume averaged CT dose index (CTDIvol) measured in cylindrical PMMA head and body phantoms of reference sizes to values for doses absorbed in individual patients. The original conversion factors used for SSDE is related to the effective diameter (ED) of the region of interest for the patient. ED is simple to measure, but does not include attenuation, which affects estimation of the dose absorbed. Water-equivalent diameter (Dw) which takes account of attenuation through the CT number, based on the linear attenuation coefficients, has been recommended to replace ED. The main scan parameter that affects Dw values is the x-ray spectrum. In this study, a library of 363 phantoms (168 paediatric and 195 adult) of a wide range of sizes from newborn to large adult were used to investigate the influence of the x-ray spectrum on Dw and the correlation between ED and Dw. Values were assessed for each phantom over seven scanned regions: head, chest, abdomen, pelvis, chest-abdomen, abdomen-pelvis, and the whole trunk using x-ray spectra of 80–140 kVp. The results show the effect of x-ray spectrum on the relationship between Dw and ED for the trunk regions was minimal, and almost all Dw/ED ratios were within a factor of ±1.01. However, Dw/ED values for the head region varied by a factor of up to 1.10 with the x-ray spectra. Energy-independent correlations between ED and Dw values for the trunk regions have been established. The correlations were compared with published results calculated by AAPM using another method and gave an average difference of 2.9%. Use of the correlations should simplify determination of the SSDE taking account of attenuation based on ED that is more readily measurable than Dw, which requires advanced software.

International Commission on Radiological Protection (ICRP) Publication 103 provided a detailed explanation of the purpose and use of effective dose and equivalent dose to individual organs and tissues. Effective dose has proven to be a valuable and robust quantity for use in the implementation of protection principles. However, questions have arisen regarding practical applications, and a Task Group has been set up to consider issues of concern. This paper focusses on two key proposals developed by the Task Group that are under consideration by ICRP: (1) confusion will be avoided if equivalent dose is no longer used as a protection quantity, but regarded as an intermediate step in the calculation of effective dose. It would be more appropriate for limits for the avoidance of deterministic effects to the hands and feet, lens of the eye, and skin, to be set in terms of the quantity, absorbed dose (Gy) rather than equivalent dose (Sv). (2) Effective dose is in widespread use in medical practice as a measure of risk, thereby going beyond its intended purpose. While doses incurred at low levels of exposure may be measured or assessed with reasonable reliability, health effects have not been demonstrated reliably at such levels but are inferred. However, bearing in mind the uncertainties associated with risk projection to low doses or low dose rates, it may be considered reasonable to use effective dose as a rough indicator of possible risk, with the additional consideration of variation in risk with age, sex and population group.

Nanophase-separated amphiphilic polymer co-networks are ideally suited as responsive membranes due to their stable co-continuous structure. Their functionalization with redox-responsive 2,2′:6′,2′′-terpyridine–metal complexes and light-responsive spiropyran derivatives leads to a novel material with tunable optical, redox and permeability properties. The versatility of the system in complexing various metal ions, such as cobalt or iron at different concentrations, results in a perfect monitoring over the degree of crosslinking of the hydrophilic poly(2-hydroxyethyl acrylate) channels. The reversibility of the complexation, the redox state of the metal and the isomerization to the merocyanine form upon UV illumination was evidenced by cyclic voltammetry, UV-Vis and permeability measurements under sequential conditions. Thus, the membrane provides light and redox addressable functionalities due to its adjustable and mechanically stable hydrogel network.

Measurement of cumulative dose f(0,150) with a small ionization chamber within standard polymethyl methacrylate (PMMA) CT head and body phantoms, 150 mm in length, is a possible practical method for cone‐beam computed tomography (CBCT) dosimetry. This differs from evaluating cumulative dose under scatter equilibrium conditions within an infinitely long phantom f(0,∞), which is proposed by AAPM TG‐111 for CBCT dosimetry. The aim of this study was to investigate the feasibility of using f(0,150) to estimate values for f(0,∞) in long head and body phantoms made of PMMA, polyethylene (PE), and water, using beam qualities for tube potentials of 80−140 kV. The study also investigated the possibility of using 150 mm PE phantoms for assessment of f(0,∞) within long PE phantoms, the ICRU/AAPM phantom. The influence of scan parameters, composition, and length of the phantoms was investigated. The capability of f(0,150) to assess f(0,∞) has been defined as the efficiency and assessed in terms of the ratios ϵ(f(0,150)/f(0,∞)). The efficiencies were calculated using Monte Carlo simulations for an On‐Board Imager (OBI) system mounted on a TrueBeam linear accelerator. Head and body scanning protocols with beams of width 40−500 mm were used. Efficiencies ϵ(PMMA/PMMA) and ϵ(PE/PE) as a function of beam width exhibited three separate regions. For beam widths

We here report a systematic study of structural and conformational variations in a series of terarylene molecules designed for use as photohydride generators. This family of compounds have been shown to facilitate self-contained hydride release, without the need for external sources of hydrogen in a manner analogous to previously reported photoacid generators. A systematic analysis has been carried out on the effects of minor structural changes on each of the three key constituent parts of the core terarylene framework. Through UV–vis, NMR, Mass Spectrometry and quantum photon counting methods, the effect of these changes in each part of the framework on hydride release efficiencies have been established. Based upon this detailed NMR and conformational DFT analysis have been carried out to quantify the yields of hydride release and to establish optimal structural motifs within the design of the photogenerator to maximize hydride release efficiencies.