Strategy for finding new materials for ESR dosimeters

The right strategy for finding a new ESR dosimetric material sensitive to radiation is to follow the orthodox procedures used in the development of thermoluminescence dosimeters (TLD) and phosphorescence studies. Modern procedures used in materials sciences, such as computer calculation of molecular orbitals (MO), should be employed to estimate the ESR and optical properties of prospective materials. Radiation effects in lithium and magnesium sulfates and metal salts of organic acids, such as lithium and magnesium lactates, have been investigated in search for tissue-equivalent dosimeter with a large G value.     

Novel Materials for Low-Contrast Phantoms for Computed Tomography

Acceptance testing and quality control of computed tomography (CT) scanners are of great importance. While most procedures and phantoms for testing other parameters are widely accepted, there is still discussion and uncertainty about low-contrast (LC) performance tests that measure the capability of a CT scanner to discriminate low-contrast objects. This work investigated the development of LC phantoms with available, low-cost polystyrene resin materials and some selected additives. We designed and tested phantoms with several different contrast steps by generating contrast in two different ways, one based on 'physical density difference' and the other on 'atomic number difference'. Physical density difference was achieved by adding a small amount of glycerin to the polystyrene resin, both having similar low atomic-number elements but differing in the density of their atoms. Atomic number difference was achieved by adding a small amount of iodobenzene to the resin, both having approximately the same physical density (less than 1% variation in density) but different atomic (i.e., elemental) composition. Prototypes were evaluated using a Philips Tomoscan LX system and varying beam properties. The behavior and validity of the results are discussed.     

Evidence for a genetic basis for altitude-related illness

Altitude-related illnesses are a family of interrelated pulmonary, cerebral, hematological, and cardiovascular medical conditions associated with the diminished oxygen availability at moderate to high altitudes. The acute forms of these debilitating and potentially fatal conditions, which include acute mountain sickness (AMS), high altitude pulmonary edema (HAPE), and high altitude cerebral edema (HACE), often develop in incompletely acclimatized lowlanders shortly after ascent, whereas, the chronic conditions, such as chronic mountain sickness (CMS) and high altitude pulmonary hypertension (HAPH), usually afflict native or long-term highlanders and may reflect a loss of adaptation. Anecdotal reports of particularly susceptible people or families are frequently cited as evidence that certain individuals have an innate susceptibility (or resistance) to developing these conditions and, in recent decades, there have been a number of studies designed to characterize the physiology of individuals predisposed to these conditions, as well as to identify the specific genetic variants that contribute to this predisposition. This paper reviews the epidemiological evidence for a genetic component to the various forms of altitude-related illness, such as innate susceptibility, familial clustering, and patterns of population susceptibility, as well as the molecular evidence for specific genetic risk factors. While the evidence supports some role for genetic background in the etiology of altitude-related illness, limitations in individual studies and a general lack of corroborating research limit the conclusions that can be drawn about the extent of this contribution and the specific genes or pathways involved. The paper closes with suggestions for future work that could support and expand on previous studies, as well as provide new insights.     

Planning for the Mercy Center for Breast Health

During the last months of 2000, administrators at the Mercy San Juan Medical Center in Carmichael, Calif., convened a steering committee to plan the Mercy Center for Breast Health. The Steering Committee was composed of the director of ancillary and support services, the oncology clinical nurse specialist, the RN manager of the oncology nursing unit, the RN surgery center manager, and me, the manager of imaging services. The committee was responsible for creating a new business with five specific objectives: to position the Center as a comprehensive diagnostic and resource center for women; to generate physician referrals to the Breast Center through various vehicles; to create awareness of the Breast Center's capabilities among area radiologists; to create awareness of the Breast Center among employees of six sister facilities; to create "brand awareness" for the Mercy Center for Breast Health among referring physicians and patients who could use competing centers in the area. The Steering Committee's charter was to design a center with a feminine touch and ambience and to provide a "one-stop shopping" experience for patients. A major component of the Breast Center is the Dianne Haselwood Resource Center, which provides patients with educational support and information. The Steering Committee brought its diverse experience and interests to bear on arranging for equipment acquisition, information and clerical systems, staffing, clinic office design, patient care and marketing. Planning the Mercy Center for Breast Health has been a positive challenge that brought together many elements of the organization and people from different departments and specialties to create a new business venture. Our charge now is to grow and to live up to our vision of offering complete breast diagnostic, education and support services in one location.     

Physician Skis for Fitness,Races for Reward

Milton Hanson was looking forward to a five-month cross-country skiing vacation, but the challenge of ski racing induced him to enter a series of international races.     

Challenges for managing the cumulative effective dose for patients

Notwithstanding that 100 mSv is not a threshold for radiation effects, cumulative effective dose (CED) for patients of ≥100 mSv derived from recurrent imaging procedures with ionising radiation has been recently the topic of several publications. The International Commission on Radiological Protection has alerted on the problems to use effective dose for risk estimation in individual patients but has accepted to use this quantity for comparison the relative radiation risks between different imaging modalities. A new International Commission on Radiological Protection document on the use of effective dose (including medicine), is in preparation. Recently published data on the number of patients with CED ≥100 mSv ranged from 0.6 to 3.4% in CT and around 4% in interventional radiology. The challenges to manage the existing situation are summarised. The main aspects identified are: 1) New technology with dose reduction techniques. 2) Refinements in the application of the justification and optimisation for these groups of patients. 3) Patient dose management systems with alerts on the cumulative high doses. 4) Education on the proper use of cumulative effective dose for referrers and practitioners including information for patients. 5) Future research programmes in radiation biology and epidemiology may profit the patient dose data from the groups with high cumulative dose values.

Cumulative effective doses for patients derived from recurrent imaging procedures with ionising radiation has been a topic of interest in the scientific literature since many years. However, its attention has been heightened in the last year with numerous publications, stating that at 100 mSv of effective dose, many organs may receive doses of 100 mGy or more.It was in 2009 when on one hand, IAEA announced its smart card project to track radiation exposure history of patients and on other hand a paper by Sodickson et al provided data on patients who underwent recurrent diagnostic CT examinations over the prior 22 years.^1,2 The approach was well received by the professional community³ but with the fear of its misuse.^4,5 In 2012, Durand et al⁴ considered it “dangerous” to use this approach for cancer risk estimations. Sometimes, it may cause patients or poorly informed physicians “to irrationally decide against medically indicated CT scans.” The authors remind the International Commission on Radiological Protection (ICRP) advice on this issue: “The use of effective dose is not appropriate for estimating the risk to an individual patient resulting from a diagnostic X-ray exam.”In 2014, Whalsh et al revisited the topic in a Commentary in the British Journal of Radiology focussing on the justification.⁶ One of the main aspects was if the radiation risks from previous examinations should affect the future procedures. The authors indicate that allowing cumulative dose estimates to influence whether a patient should get a scan would be equivalent to introducing dose limits for patients and, rather than improving patient safety, would unnecessarily restrict access to radiation-based diagnostic examinations.In the first ever multinational survey among referring physicians from 28 countries, the support for a system that provides radiation exposure history of the patient was demonstrated.⁷ A study from Finland covering 33 institutions in the Helsinki-Uusimaa Hospital District indicated that patient-specific justification and optimisation becomes possible using the tracking of radiologic procedures and radiation dose of individual patients.⁸Some recent papers have collected data to estimate number of patients with cumulative effective doses (CED) ≥100 mSv derived from recurrent CT examinations alone.^3,9,10 The papers estimated that around 0.9 million patients with CED ≥100 mSv are likely occurring every year globally.^3,9 The dose management systems used in some of the hospitals involved in these studies were able to calculate organ and effective doses allowing the analysis of the cumulative doses in the patients. In one of the papers,⁹ data were collected from 324 hospitals involving a total of 488 CT scanners in USA and 1 country in Central Europe (2.5 million patients with 4.8 million CT exams). The patients with CED ≥100 mSv vary from 0.64% to 3.4% in the different hospitals or institutions included in the study. Another paper contains the data of about 70,000 patients from 20 countries: 18 of them in Europe, 1 in Africa, and 1 in Asia with an average of 0.65% of 702,205 patients undergoing CT scans with CED ≥100 mSv.³The IAEA convened a meeting in 2019 with participants from 26 countries, representatives of various organisations, and experts in radiology, medical physics, radiation biology, and epidemiology.³ The meeting led to a Call for Action stating the need for urgent actions by all stakeholders to address the issue of high cumulative radiation doses to patients. The actions include development of appropriateness criteria/referral guidelines by professional societies for patients who require recurrent imaging studies, development of CT machines with lower radiation dose than today by manufacturers, and development of policies by risk management organisations to enhance patient radiation safety. Alert values for cumulative radiation exposures of patients should be set up and introduced in dose monitoring systems.³In another recent study with interventional radiology practices, Xinhua et al studied 25,253 patients who underwent 46,491 fluoroscopy-guided procedures (from January 2010 to January 2019). It was concluded that in 4% of them, the CED was ≥100 mSv and median age of the first procedures was 60 years. Around 80% patients underwent all of their procedures within 365 days.¹¹The automatic patient dose registries are able to set alarms informing clinicians in special situations. The referral criteria for patients with several (or many) previous imaging procedures involving moderated or high doses may be revisited¹⁰ and specific optimisation strategies could be considered in some cases. The European Working Group on “Dose Management” launched by the Eurosafe Imaging from the European Society of Radiology recommended setting alert trigger levels, to be able to send these alerts to professionals and to store and display cumulative patient dose values.¹²In a very recent paper Kachelrieß and Rehani identified several technology-related factors of the CT systems that can be used by manufacturers of CT equipment to achieve substantial reduction in radiation dose to the patients while maintaining or improving the image quality¹³ in line with need identified in recent papers.^3,9,10 The advances in the new systems used for interventional procedures may also allow remarkable decreases in patient doses.According to the ICRP recommendations, we should not use the radiation protection quantity “effective dose” to estimate radiation risks for individual patients.¹⁴ A new ICRP document on the use of effective dose (including medicine) is in preparation. Nevertheless, effective dose is useful to compare the doses and relative risks of different imaging modalities (e.g. CT, fluoroscopy-guided interventional procedures and nuclear medicine). This comparison is also useful for referrers when they balance the benefits and risks of the different examinations before suggesting one imaging modality.⁷ The quantity effective dose may also be useful to inform patients when they ask on the meaning of the different radiation units that may be included in the clinical reports: “mGy.cm” for CT, or Gy.cm² for interventional procedures, or MBq of a certain radiopharmaceutical in nuclear medicine procedures.The use of effective dose may have important limitations as the uncertainty in the calculation, the different implications on the patient risk depending on the age and gender, the radiation dose for the different organs and tissues may be distinct despite having the same value for effective dose. In many cases, effective doses can be estimated from a single conversion factor multiplying the practical radiation unit offered by the X-ray system or the activity of the radiopharmaceutical, and with this approach, the uncertainty may be much higher than using Monte Carlo calculations.The five main aspects to consider in the management of the cumulative effective doses could be summarised as follow:

1. Impact of technology: New technology with dose reduction techniques, especially for the high dose imaging modalities (CT, Interventional and PET-CT)^15,16 should be developed and promoted. Moreover, when available in health centres, they must be used for the high dose procedures. COCIR, the European Trade Association representing the medical imaging, radiotherapy, health ICT and electromedical industries, is doing an important effort to reduce the age of the imaging equipment in Europe to allow introducing the low dose techniques.¹⁷
2. Justification and optimisation: Professional societies could develop appropriateness criteria for patients who need series of imaging studies using ionising radiation. This group of patients may require some re-evaluation of the justification criteria, and improvements in the optimisation strategies for future procedures.
3. Patient dose management systems: Some alerts based on the cumulative dose should be included in the dose management systems. If effective doses are not available, other dosimetric quantities available from the X-ray systems may be used. However, these alerts should not be used to discourage any procedure if it is medically indicated. The clinical decision support systems may incorporate these alerts. The European Directive 2013/59/Euratom requires estimation of population doses from medical exposures and these data are required for the UNSCEAR surveys.
4. Proper use of cumulative dose: Education on the proper use of cumulative effective dose should be included in the training programmes for referrers and practitioners including the proper information for patients. In some cases, patients may accept a small additional radiation risk for a fast diagnosis or a second opinion, and this may be ethically acceptable as part of the autonomy and rights of the patient.¹⁸
5. Data for research: The future research programmes in radiation biology and epidemiology could use the data from the groups of patients with high dose values collected by the dose management systems allowing to estimate organ and effective doses.

     

A thermophysiological rationale for endurance training for racquet games

Three male athletes performed incremental work: Basal Metabolic Rate (BMR), 100 W and 150 W in two levels of controlled environmental heat. Conditions inside an environmental chamber were preset at 25°C 40% RH and 30°C 50% RH being 22°C and 29°C on the Effective Temperature Scale. Expired air and six body temperatures—two invasive and four skin sites—were monitored. Core and mean body temperatures, calculated from these figures, correlated highly with expired air values for all the anthropometrically homogeneous group. Results were in agreement with unpublished data of Bundgaard, i.e. the higher the O₂ max of the subject the smaller the range of expired air values and the smaller the increase in both mean and core body temperature during heat stress. Such thermophysiological reaction helps the athlete to prevent the onset of mild hyperthermia and the accompanying fatigue, independent of mitigating behavioural support.

The intermittent bursts of heavy physical activity required of the racquet athlete argue for a similar cardio-vascular training regimen. Data from this study suggest that such athletes would be wise to augment training schedules with prolonged cardio-vascular endurance work especially when the possibility of competing in high ambient temperature is foreseen.

     

The need for individualized dosimetry for tangential breast treatment

We have examined the isodose distributions of 119 intact breast patients treated on a 6 MV linae to determine if a library of treatment plans could be used instead of individualized computer plans for patient treatments without compromising the quality of those treatments. The parameters studied were: field width, baseline separation, central axis separation, wedge angle, and isodose coverage. At least two wedges were used in the computer plans for each patient and the best plan was then chosen. In order to construct a library of plans, the choice of wedge, treatment isodose, and dose uniformity should be predictable. Our results show that for 90 out of 119 plans (76%), the 30° wedge was best. In the other 29 cases, either the 15° or the 45° wedge yielded better plans. On average, the improvement in dose homogeneity due to choice of wedge was about 2% (range 0–7%) for these cases. Although grouping like-patient parameters generally restricted the isodose variation to ± 2.5%, there were five patients for which up to a 7% underdosage would not have been predicted. For the set of plans using a 30° wedge, a significant correlation was found for the ratio of the baseline to central axis separation vs. treatment isodose. The average isodose which covered the target area was 97% (range 90–100%) and 102 out of 107 patient plans using the 30° wedge fell between 94 and 100%. We conclude from these results that the variation in dose distribution found with seemingly similar sized breasts is due to the variation in breast shape and symmetry. The use of a library plan with a single wedge and a standardized isodose line for tangential field treatment of intact breast could cause up to a 7% dose difference compared to the actual dosimetry for that patient.     

Caution warranted for low-dose radiation therapy for Covid-19

Covid-19 is a morbid respiratory disease that has caused desperate times on a global scale due to the lack of any effective medical treatment. Some in the radiation community are actively proposing low-dose radiation therapy (LDRT) for managing the viral pneumonia associated with Covid-19. This commentary provides a rationale for exercising caution against such a decision as the efficacy of LDRT for viral diseases is unknown, while its long-term adverse risks are well known.