Monitoring the eye lens: how do the international organisations react?

The International Commission on Radiological Protection (ICRP) has recommended to lower the limit of the dose to the eye lens for occupationally exposed persons to a mean value of 20 mSv y(-1) (averaged over 5 y, with a maximum of 50 mSv y(-1)); already in the autumn of 2011, both the European Commission and the International Atomic Energy Agency : IAEA) took over this reduction in their respective draft basic safety standards. Even prior to this (and since then, increasingly so), several international activities were started (among other things, the following ones): (1) the ICRP adopted a stylised model of the eye to calculate dose conversion coefficients for its report ICRP 116; (2) the European Commission has funded the ORAMED project dealing with radiation protection in medicine; (3) in its standard IEC 62387 on passive dosimetry systems, the International Electrotechnical Commission (IEC) has laid down requirements for Hp(3) eye dosemeters; (4) the International Organization for Standardization (ISO) and the IAEA provide a range of practical advice in the standard ISO 15382 (still a draft) and in a technical document IAEA TecDoc on both radiation protection and on dosimetry; (5) for most cases, the International Commission on Radiation Units and Measurements (ICRU) recommends both phantoms (the slab and the cylinder). In short: most national procedures can orientate themselves on international ones; some questions, however, remain open.

[True and virtual risks of travellers]

Evidence-based information on travel associated mortality is scarce. Perception, intuition and the availability of interventions such as vaccinations and chemoprophylaxis often guide pre-travel advice. Important risks including accidents and cardiovascular events are not routinely included in pre-travel consultations although they cause more fatalities and costs than infectious diseases. The increased risk of sustaining a road accident in poor economy countries should always be mentioned. The general practitioner is further best placed to discuss possible problems of travellers with chronic diseases before travel.

[Ingestion of foreign bodies in the gastrointestinal tract of children and adolescents]

The diagnosis of foreign bodies in the gastrointestinal (G-I) tract can sometimes be difficult. Esophageal foreign bodies are dangerous and should be extracted as soon as possible whereas foreign bodies in the stomach usually pass through the GI-tract without complications. Exceptions are large, sharp or potentially toxic foreign bodies, such as button batteries or magnetic foreign bodies. Extraction by flexible endoscopy with the patient under deep sedation has proven to be effective, relatively minimally invasive and safe. Complications, such as ulcers, fistulas and perforations occur in 13% of patients and are strongly correlated to the localization in the esophagus.

On the operational quantity H(p)(3) for eye lens dosimetry

In the past the operational quantity H(p)(3) has been defined for calibration purposes in a slab phantom. Recently, an additional phantom in the form of a cylinder was suggested for eye lens dosimetry as a cylinder much better approximates the shape of a head than a slab. Therefore, this work investigates whether the quantity H(p)(3), when defined in the respective calibration phantom, adequately estimates the eye lens dose (or is at least conservative) depending on the phantom: it turns out that in most cases both calibration phantoms are similarly well suited. Finally, the definition of the eye lens dose is discussed together with possible consequences on the definition of H(p)(3): the consideration of only the radiation sensitive volume of the lens causes H(p)(3) not to be conservative in beta radiation fields.

Air kerma to Hp(3) conversion coefficients for a new cylinder phantom for photon reference radiation qualities

The International Organization for Standardization (ISO) has issued a standard series on photon reference radiation qualities (ISO 4037). In this series, no conversion coefficients are contained for the quantity personal dose equivalent at a 3 mm depth, H(p)(3). In the past, for this quantity, a slab phantom was recommended as a calibration phantom; however, a cylinder phantom much better approximates the shape of a human head than a slab phantom. Therefore, in this work, the conversion coefficients from air kerma to H(p)(3) for the cylinder phantom are supplied for X- and gamma radiation qualities defined in ISO 4037.

Hp(0.07) photon dosemeters for eye lens dosimetry: calibration on a rod vs. a slab phantom

In recent years, several papers dealing with eye lens dosimetry have been published as epidemiological studies are implying that the induction of cataracts occurs even at eye lens doses of less than 500 mGy. For that reason, the necessity to monitor the eye lens may become more important than it was before. However, only few dosemeters for the appropriate quantity H(p)(3) are available. Partial-body dosemeters are usually designed to measure the quantity H(p)(0.07) calibrated on a rod phantom representing a finger while a slab phantom much better represents the head. Therefore, in this work it was investigated whether dosemeters designed for the quantity H(p)(0.07) calibrated on a rod phantom can also be worn on the head (close to the eyes) and still deliver correct results (H(p)(0.07) on a head). For that purpose, different types of partial-body dosemeters from routine use were irradiated at different photon energies on both a rod and a slab phantom. It turned out that their response values are within ±5% independent of the phantom if the quantity value for the respective phantom is used. Thus, partial-body dosemeters designed for the quantity H(p)(0.07) calibrated on a rod phantom may be worn on the head and used to monitor the eye lens dose due to photon radiation via the measurement of H(p)(0.07) on the head.

IEC standards for individual monitoring of ionising radiation

This paper presents IEC/SC 45B 'Radiation protection instrumentation' and its standards for individual monitoring of ionising radiation: IEC 61526 Ed. 3 for active personal dosemeters and IEC 62387-1 for passive integrating dosimetry systems. The transposition of these standards as CENELEC (European) standards is also discussed together with the collaboration between IEC/SC 45B and ISO/TC 85/SC 2.

[Benefits and risks of tube feeding via gastrostoma in infants and children with peritoneal dialysis]

BACKGROUND

Nutrition of children with end-stage renal disease and peritoneal dialysis (PD) is often difficult. Tube feeding via a gastrostoma is discussed controversially, and some authors consider this as a contraindication because of the risk of peritonitis.

METHODS

In our centre 16 infants and children with end-stage renal disease were treated with PD and tube feeding over a gastrostoma in the last 12 years. The patients showed dystrophy (mean BMI -1.73 SDS) and were too small (mean body length -4.56 SDS). Seven of them (median age 11 months) received a gastrostoma before insertion of a Tenkhoff-catheter and start of PD. Nine children (median age 5 months) had PD primarily before insertion of the gastrostoma and start of tube feeding.

RESULTS

Patients with start of PD while a gastrostoma was already inserted had 15 events with peritonitis in the observation time of 91 months (1.98 per patient year). Patients with primary start of PD had 12 events with peritonitis in a total time of 43 month (3.34 per patient year), after insertion while PD was already running the number of events fell significantly to 25 peritonitis events in a total of 271 months (1.11 per patient year, p < 0.01). The children had a benefit from tube feeding via a gastrostoma in regard of body weight (BMI + 1.61 SDS, p < 0.01) as well as growth (body height + 2.29 SDS, p < 0.05).

CONCLUSION

Tube feeding via a gastrostoma is a good and safe option for alimentation, even under peritoneal dialysis. A decrease of PD-associated peritonitis under tube feeding was observed while physical development was positively influenced.

[Japanese encephalitis: risk for endemic populations and for travellers]

The importance of Japanese encephalitis (JE) in endemic populations and in travellers requires a balanced assessment. This disease represents an important public health problem in some endemic areas, which contrasts with the minimal risk for travellers to endemic areas. This is reflected by high numbers of infections mainly among children in endemic countries and by few case reports among tourists and even expatriates. The total number of case reports between 1978 and 2008 amounts to a risk of one to two cases per year. Nevertheless, some travelling groups may be at higher risk when visiting or working in high risk areas. A new vaccine against Japanese encephalitis will soon be registered in Switzerland. This paper contributes to the scarce data available for decision making whether or not to recommend the vaccination to tourists and expatriates.

Uncertainties in external dosimetry: analytical vs. Monte Carlo method

Over the years, the International Commission on Radiological Protection (ICRP) and other organisations have formulated recommendations regarding uncertainty in occupational dosimetry. The most practical and widely accepted recommendations are the trumpet curves. To check whether routine dosemeters comply with them, a Technical Report on uncertainties issued by the International Electrotechnical Commission (IEC) can be used. In this report, the analytical method is applied to assess the uncertainty of a dosemeter fulfilling an IEC standard. On the other hand, the Monte Carlo method can be used to assess the uncertainty. In this work, a direct comparison of the analytical and the Monte Carlo methods is performed using the same input data. It turns out that the analytical method generally overestimates the uncertainty by about 10-30 %. Therefore, the results often do not comply with the recommendations of the ICRP regarding uncertainty. The results of the more realistic uncertainty evaluation using the Monte Carlo method usually comply with the recommendations of the ICRP. This is confirmed by results seen in regular tests in Germany.

Secondary charged particle equilibrium in 137Cs and 60Co reference radiation fields

During the calibration or irradiation of dosemeters, typical irradiation geometries (collimated beams) and source-to-detector distances (1-5 m) lead to the fact that for photon energies above a few hundred keV, the secondary charged particle equilibrium is usually not ensured. The reason is that the effective beam radius at the detector position is smaller than the range of the secondary electrons produced in air whose maximum particle energy is as large as the maximum photon energy. Therefore, the International Organization for Standardization (ISO) recommends putting a build-up plate (BUP) made of polymethyl methacrylate in front of the dosemeter to be calibrated in ISO 4037-3. In this paper, the effect of the thickness of the BUP and its distance from the dosemeter at different source-to-dosemeter distances were investigated by means of measurement and calculation. It turned out that the geometrical arrangement of the source, dosemeter and BUP recommended by ISO mostly does not ensure secondary charged particle equilibrium. The consequence is to always place the BUP directly in front of the dosemeter to be calibrated or irradiated.

Characterisation of three high-energy photon and fast neutron reference radiation fields

Three reference radiation fields for the purpose of radiation protection were characterised: (1) radiation field R-F, consisting of photons in the energy range of about 6 and 7 MeV and a small neutron contamination; (2) radiation field R-C, consisting of photons with energies of about 4.4 MeV and neutrons with energies up to 2.65 MeV; (3) radiation field R-CF, consisting of photons in the energy range of about 1 and 7 MeV and neutrons with energies about 1.5 MeV. The radiation fields R-F and R-C have previously been defined in the ISO standard 4037. Their neutron components, however, have never been described accurately in the past. The new radiation field R-CF is proposed for the first time. This radiation field can, e.g., be used to calibrate tissue-equivalent proportional counters instruments for measurements at flight altitudes.

New concept of IEC standards for radiation protection dosemeters

The International Electrotechnical Commission (IEC) develops new standards for radiation protection dosemeters which follow a new concept. They are much more flexible in detail, but still ensure the same measurement quality. They are, for example, no longer specific for the detector type, but rather specific for the measurement task, e.g. for individual monitoring with active direct-reading instruments. Another example is that they are flexible with respect to the ranges of influence quantities. The conceptual changes are described in this paper, together with the advantages this new concept provides for manufacturers, users and legislators.

Chronisch-entzündliche Darmerkrankung und Nephritis

An 11 year old CD-patient developed an interstitial nephritis and acute kidney failure following treatment with Mesalazine (5-ASA) and Salazosulfapyridine (SASP). After removal of the medication and treatment with hemofiltration and prednisone there was only an incomplete recovery of the renal function (creatinine-clearance 34 ml/1,73 m2/min). It is thought that an hyperergic-allergic reaction due to SASP and 5-ASA causes interstitial nephritis in inflammatory bowel disease (IBD). This reaction can be induced by re-exposition too. On the other hand IBD can be associated with glomerulonephritis. This could be a not very well known extraintestinal manifestation in IBD caused by immune-complexes in serum and glomerula. A rapid histological verification of the renal disease is necessary for successful treatment. In both renal manifestations chronic courses are possible. These observations should not lead to avoid SASP/5-ASA in treatment of IBD, but renal function should be routinely investigated.