Alanine/EPR dosimetry for mailed intercomparison at ocular proton therapy facilities-preliminary results for three centres for irradaitions at CCB IFJ PAN eyeline.

Quality control of therapeutic photon beams in the form of postal dose audits based on passive dosemeters is widely used in photon radiotherapy. On the other hand, no standardised dosimetry audit programme for proton centres has been established in Europe so far. We evaluated alanine/EPR dosimetry systems developed at the Istituto Superiore di Sanità (Italy), the Hasselt Universiteit (Belgium) and the Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences (Poland) for their applicability as a potential tool for routine mailed dose audits of passively scattered therapeutic proton beams. The evaluation was carried out in the form of an intercomparison. Dosemeters were irradiated in the 70 MeV proton beam at ocular proton therapy facility in the Cyclotron Centre Bronowice at the Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences in Krakow. A very good agreement was found between the dose measured by three laboratories and the delivered dose determined with an ionisation chamber. This, together with the inherent properties of alanine, such as non-destructive readout, tissue equivalence, weak energy dependence, dose rate independence and insignificant fading, makes alanine a good candidate for a dosemeter used in postal auditing in proton ocular radiotherapy.

EPR dosimetry intercomparison using smart phone touch screen glass.

This paper presents the results of an interlaboratory comparison of retrospective dosimetry using the electron paramagnetic resonance method. The test material used in this exercise was glass coming from the touch screens of smart phones that might be used as fortuitous dosimeters in a large-scale radiological incident. There were 13 participants to whom samples were dispatched, and 11 laboratories reported results. The participants received five calibration samples (0, 0.8, 2, 4, and 10 Gy) and four blindly irradiated samples (0, 0.9, 1.3, and 3.3 Gy). Participants were divided into two groups: for group A (formed by three participants), samples came from a homogeneous batch of glass and were stored in similar setting; for group B (formed by eight participants), samples came from different smart phones and stored in different settings of light and temperature. The calibration curves determined by the participants of group A had a small error and a critical level in the 0.37-0.40-Gy dose range, whereas the curves determined by the participants of group B were more scattered and led to a critical level in the 1.3-3.2-Gy dose range for six participants out of eight. Group A were able to assess the dose within 20 % for the lowest doses (<1.5 Gy) and within 5 % for the highest doses. For group B, only the highest blind dose could be evaluated in a reliable way because of the high critical values involved. The results from group A are encouraging, whereas the results from group B suggest that the influence of environmental conditions and the intervariability of samples coming from different smart phones need to be further investigated. An alongside conclusion is that the protocol was easily transferred to participants making a network of laboratories in case of a mass casualty event potentially feasible.

Subcellular localization of ribosomal P0-like protein MRT4 is determined by its N-terminal domain.

The Mrt4 protein, showing extensive sequence similarity to the ribosomal P0 protein, is classified as a ribosomal P0-like protein and acts as a trans-acting factor which modulates the assembly of the pre-60S particle. In this report we investigated the biological nature of the human Mrt4 protein. First, we constructed a series of hybrid hMrt4-P0 proteins by replacing various domains of the P0 protein with corresponding protein fragments from hMrt4. We found that hMrt4 binds to the same site on the large ribosomal subunit as does P0, but despite the sequence homology it is not able to functionally complement the lack of P0. Using fluorescence microscopy and biochemical approaches we also show that hMrt4 occupies predominantly the nucleolar compartment, in contrast to P0 and P1/P2, which are located in the cytoplasm. The nucleolar accumulation of hMrt4 does not depend on a specific nucleolus localization signal, but rather occurs via interaction with established nucleolar components such as rRNA; however, nuclear import of hMrt4 is dependent on a short sequence in the N-terminal part of the protein. Functional analysis with specific inhibitors, actinomycin D and leptomycin B, showed that hMrt4 is a trans-acting factor involved in ribosome maturation, with nucleus-cytoplasm shuttling capacity.

Proton radiotherapy facility for ocular tumors at the IFJ PAN in Kraków Poland.

The proton radiotherapy facility for the eye melanoma treatment is under development at the Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences (IFJ PAN) in Krakow. The facility uses protons, accelerated by the AIC-144 isochronous cyclotron up to the energy of 60 MeV. The infrastructure and all necessary equipment have been already installed. The paper describes the present status of the facility, gives results of the preliminary beam measurements and shows future perspectives.