Slaven Jurković

Rotation of the Sacrum During Bellyboard Pelvic Radiotherapy

Patients with cervical, uterine, and rectal carcinomas are usually treated in the prone position using the bellyboard positioning device. Specific and uncomfortable prone position gives rise to uncertainties in the daily set-up of patients during the treatment. During investigation of translational movements, rotational movements of the pelvis are observed and investigated. The film portal imaging is used to discover patient positioning errors during treatment. We defined the rotational set-up errors by angle deviations of the sacrum. Thirty-six patients were included in the study; 15 patients were followed during the whole treatment and 21 during the first 5 consecutive treatment days. The image acquisitions were completed in 84%. Systematic and random positioning errors were analyzed in 725 images. Approximately half of the patients had adjusted to the bellyboard in the first few fractions, with sacrum angles remaining the same for the rest of the treatment. The other half had drifts of the sacrum angle during the whole treatment. The rotation of the sacrum during treatment ranged up to 14 degrees , causing the usual set-up verification and correction procedure to result in errors up to 15 mm. Rotational movements of the patient pelvis during bellyboard pelvis radiotherapy can introduce considerable patient position error.

NKG2D Promotes B1a Cell Development and Protection against Bacterial Infection

NKG2D is a potent activating receptor that is expressed on cytotoxic immune cells such as CD8 T and NK cells, where it promotes cytotoxicity after binding stress ligands on infected or transformed cells. On NK cell precursors NKG2D modulates proliferation and maturation. Previously, we observed that NKG2D deficiency affects peripheral B cell numbers. In this study, we show that NKG2D regulates B1a cell development and function. We find that mice deficient for NKG2D have a strong reduction of B1a cell numbers. As a result, NKG2D-deficient mice produce significantly less Ag-specific IgM Abs upon immunization with T cell–independent Ags, and they are more susceptible to Gram-negative sepsis. Klrk1−/− B1a cells are also functionally impaired and they fail to provide protection against Francisella novicida upon adoptive transfer. Using mixed bone marrow chimeric mice, we show that the impact of NKG2D deficiency on B1a cell development is cell intrinsic. No changes in homeostatic turnover and homing of B cells were detectable, limiting the effects of NKG2D to modulation of the hematopoietic development of B1a cells. Using conditional ablation, we demonstrate that the effect of NKG2D on B1a cell development occurs at a developmental stage that precedes the common lymphoid progenitor. Our findings reveal an unexpected new role for NKG2D in the regulation of B1a cell development. The protective effects of this activating receptor therefore reach beyond that of cytotoxic cells, stimulating the immune system to fight bacterial infections by promoting development of innate-like B cells.

NKG2D stimulation of CD8(+) T cells during priming promotes their capacity to produce cytokines in response to viral infection in mice.

Natural killer group 2 member D (NKG2D) is an activating receptor that is expressed on most cytotoxic cells of the immune system, including NK cells, γδ, and CD8+ T cells. It is still a matter of debate whether and how NKG2D mediates priming of CD8+ T cells in vivo, due to a lack of studies where NKG2D is eliminated exclusively in these cells. Here, we studied the impact of NKG2D on effector CD8+ T‐cell formation. NKG2D deficiency that is restricted to murine CD8+ T cells did not impair antigen‐specific T‐cell expansion following mouse CMV and lymphocytic choriomeningitis virus infection, but reduced their capacity to produce cytokines. Upon infection, conventional dendritic cells induce NKG2D ligands, which drive cytokine production on CD8+ T cells via the Dap10 signaling pathway. T‐cell development, homing, and proliferation were not affected by NKG2D deficiency and cytotoxicity was only impaired when strong T‐cell receptor (TCR) stimuli were used. Transfer of antigen‐specific CD8+ T cells demonstrated that NKG2D deficiency attenuated their capacity to reduce viral loads. The inability of NKG2D‐deficient cells to produce cytokines could be overcome with injection of IL‐15 superagonist during priming. In summary, our data show that NKG2D has a nonredundant role in priming of CD8+ T cells to produce antiviral cytokines.

Dosimetric verification of compensated beams using radiographic film

Dosimetric verification of compensated beams using radiographic film Introduction. External photon beam modulation using compensators in order to achieve a desired dose distribution when brachytherapy treatment is followed by external beam radiation is a well-established technique. A compensator modulates the central part of the beam, and the dose beneath the thickest part of the compensator is delivered mostly by scattered, low energy photons. A two-dimensional detector with a good spatial resolution is needed for the verification of those beams. In this work, the influence of different types of detectors on the measured modulated dose distributions was examined. Materials and methods. Dosimetric verification was performed using X-Omat V, Eastman Kodak radiographic films at different depths in a solid water phantom. The film measurements were compared with those made by ionization chambers. Photon beams were also modelled using EGSnrc Monte Carlo algorithm to explain the measured results. Results. Monte Carlo calculated over-response of the film under the thickest part of the compensator was over 15%, which was confirmed by measurements. The magnitude of over-response could be associated with changes in the spectra of photon energy in the beam. Conclusions. The radiographic film can be used for the dosimetry of compensated high energy photon beams, with limitations in volumes where photon spectra are hardly degraded.

[Influence of daily set-up errors on dose distribution during pelvis radiotherapy].

Utjecaj pogreške u položaju bolesnika tijekom zračenja zdjelice na raspodjelu doze Radioterapija megavoltnim snopovima fotona linearnog akceleratora oblik je lokalnog onkološkog liječenja. Njezin je cilj predati propisanu apsorbiranu dozu ciljnom volumenu, uz što nižu dozu okolnomu zdravom tkivu. Proces se sastoji od niza koraka u kojima sudjeluje tim stručnjaka iz različitih područja. Veliki broj postupaka i ljudi uključenih u radioterapijski proces, nepouzdanosti uređaja te pomaci bolesnika i unutrašnjih organa tijekom terapije mogu uzrokovati odstupanja između planirane i stvarne raspodjele doze. U ovom radu procijenili smo utjecaj pogreške položaja bolesnika tijekom terapije na raspodjelu doze, te na veličine koje služe za procjenu kvalitete plana. Pogreške u položaju bolesnika ispitane su u skupini od 35 bolesnika. Te smo pogreške simulirali na pet bolesnika, koristeći se 3D programom za planiranje XiO (CMS Inc., St. Louis, MO, Elekta). Ispitali smo razlike u raspodjeli doze između planiranog i stvarnog položaja. Dodatno, utjecaj pogrešaka na odabir plana zračenja provjerili smo analizirajući promjene u dozno-volumnom histogramu (DVH), pokrivenost planiranog volumena (engl. PTV conformity index, CIPTV) i jednoličnost raspodjele doze u ciljnom volumenu (engl. homogeneity index, HI). Simulacije pokazuju da promjene u položaju bolesnika mogu uzrokovati značajne razlike između planirane i stvarne raspodjele doze. Kod nekih bolesnika ako se ne korigiraju pogreške, CIPTV postaje manji od 97% što znači da plan više nije prihvatljiv za zračenje. Iznenađuje da HI nije ovisan o pomacima bolesnika kao CIPTV. Rezultati pokazuju potrebu za smanjenjem pogrešaka, što se može postići provođenjem kontrole kvalitete u radioterapiji. Influence of Daily Set-Up Errors on Dose Distribution During Pelvis Radiotherapy An external beam radiotherapy (EBRT) using megavoltage beam of linear accelerator is usually the treatment of choice in cancer patients. The goal of EBRT is to deliver the prescribed dose to the target volume, with as low as possible dose to the surrounding healthy tissue. A large number of procedures and different professions involved in radiotherapy, uncertainty of equipment and daily patient set-up errors can cause a difference between the planned and delivered dose. We investigated a part of this difference caused by measuring daily patient set-up errors for 35 patients. These set-up errors were simulated on five patients, using 3D treatment planning software XiO. The simulation investigated differences in dose distributions between the planned and shifted geometry. Additionally, we investigated the influence of the error on treatment plan selection by analysing changes in dose volume histograms, planning target volume conformity index (CIPTV), and homogeneity index (HI). Simulations showed that patient daily set-up errors can cause significant differences between the planned and actual dose distributions. Moreover, for some patients, those errors could affect the choice of treatment plan since CIPTV fell under 97%. Surprisingly, HI was not as sensitive to set-up errors as CIPTV. Our results have confirmed the need to minimise daily set-up errors through quality assurance programmes.

Quantitative testing of physiotherapy ultrasound beam patterns within a clinical environment using a thermochromic tile

The implementation of the non-standardized method developed at the National Physical Laboratory (UK) supporting the quality assurance of therapeutic ultrasonic beam parameters within a clinical environment is presented. The method consists of exposing an acoustic absorber tile, part of which contains a thermochromic pigment, to the ultrasonic beam, thereby forming an image of the two-dimensional intensity profile of the transducer. Nine different physiotherapy ultrasound treatment heads currently used clinically were tested using this method. Thermochromic images were postprocessed in order to estimate the Effective Radiating Area (ERA) for treatment heads operating within the frequency range from 1 MHz to 3.2 MHz, and nominal applied intensities in the range of 1-3 W/cm(2). Experimental results and comparisons with manufacturer specified values of ERA are presented. Differences in the experimentally derived results and the manufacturer values are typically well within 25%. The root-mean squared difference calculated over the nine treatment heads is 15.1%, with the thermochromic material tended to underestimate the ERA.

Survey of equipment quality control in radiotherapy centres in croatia: first results.

Survey of Equipment Quality Control in Radiotherapy Centres in Croatia: First Results Implementation of advanced radiation therapy techniques in clinical practice can greatly improve tumour control and normal tissue sparing. An important part of this implementation is quality control (QC) of every part of the radiotherapy process, as it helps to detect errors and provides instant remedy. This increases the probability of successful radiation treatment and ensures patient radiation safety. Every radiotherapy quality assurance (QA) programme is based on quality control of radiotherapy equipment. The aim of our survey was to review QC practices in a number of radiotherapy centres in Croatia. As a first step, we defined a set of tests to check different parameters of linear accelerators and simulators in these centres. The tests were defined and performed according to protocols developed at two university hospitals. Test results varied largely between the centres. This calls for harmonisation of QC protocols. Utvrđivanje stanja kontrole kvalitete opreme radioterapijskih centara u Hrvatskoj: prvi rezultati Uvođenje naprednih radioterapijskih tehnika u kliničku praksu ima golem utjecaj na bolju kontrolu tumora i poštedu zdravog tkiva. Veliku ulogu u tome ima postojanje protokola za kontrolu kvalitete za svaki dio radioterapijskog procesa. Provođenje protokola ključno je za detektiranje pogrešaka i njihovo trenutačno ispravljanje. Time se povećava vjerojatnost za željeni ishod radioterapije i osigurava zaštita pacijenta od neželjenog zračenja. Osnova osiguranja kvalitete u radioterapiji jest kontrola kvalitete samog uređaja. U sklopu projekata financiranih od Međunarodne agencije za atomsku energiju, istraživali smo postojanje protokola za kontrolu kvalitete radioterapijske opreme. Pokazalo se da se testovi kontrole kvalitete provode u svim centrima u Hrvatskoj, no među njima postoje razlike. Također, pisani su protokoli bili rijetko prisutni. Pregled prakse u kontroli kvalitete i razmjena iskustva pomogli bi u razvoju protokola za kontrolu kvalitete na nacionalnom nivou. Kao prvi korak definirali smo niz testova za provjeru raznih parametara na linearnim akceleratorima i klasičnim simulatorima u radioterapijskim centrima u Hrvatskoj. Testovi su definirani i izvedeni u skladu s protokolima razvijenim u naše dvije bolnice. Sljedeći korak planiran je tijekom ove godine, a odnosi se na verifikaciju sustava za planiranje u kliničkim uvjetima prema protokolu izrađenom u KBC-u Rijeka. U radu iznosimo pregled provedenih testova, uređaja i računalnih programa za analizu kojima smo se koristili, kao i cjelokupne rezultate.

Estimated collective effective dose to the population from nuclear medicine diagnostic procedures in Croatia: A comparison of 2010 and 2015

Objective This study presents national surveys of patient exposure from nuclear medicine (NM) diagnostic procedures in 2010 and 2015 in the Republic of Croatia. Methods The survey was performed according to the European Commission Dose DataMed (DDM) project methodology. 28 most frequent NM diagnostic procedures were identified. Data about frequencies of procedures and average administered activities of radioisotopes used in those procedures were collected. Average administered activities were converted to effective doses according to the dose conversion coefficients. Then the collective effective dose to the population and an effective dose per capita were calculated based on the number of the most frequent NM diagnostic procedures and the average effective dose per procedure. Results In 2010, 41200 NM diagnostic procedures led to 146.7 manSv collective effective dose to the population and in 2015, 42000 NM diagnostic procedures led to 146.8 manSv collective effective dose to the population. The frequencies of NM diagnostic procedures were 9.7 and 9.8 annually per 1000 population with 34.1 μSv and 34.2 μSv effective dose per capita for 2010 and 2015, respectively. The main contributors to the annual collective dose from NM in Croatia are examinations of the bone, heart, thyroid and PET/CT tumour diagnostic. Average administered activities have not changed considerably from 2010 to 2015. Nevertheless, within the frequency of some of the procedures, significant changes were found in five-year period. Conclusions Frequencies, average administered activities and collective effective dose to the population from NM diagnostic procedures in Croatia are comparable to the values reported by other European surveys. Changes were found between 2010 and 2015 and we intend to perform this study periodically to identify possible trends, but also to raise awareness about the potential dose optimization.

The Neutron Dose Equivalent Around High Energy Medical Electron Linear Accelerators

The measurement of neutron dose equivalent was made in four dual energy linear accelerator rooms. Two of the rooms were reconstructed after decommissioning of 60Co units, so the main limitation was the space. The measurements were performed by a nuclear track etched detectors LR-115 associated with the converter (radiator) that consist of 10B and with the ac - tive neutron detector Thermo BIOREM FHT 742. The detectors were set at several locations to evaluate the neutron ambient dose equivalent and/or neutron dose rate to which medical personnel could be exposed. Also, the neutron dose dependence on collimator aperture was analyzed. The obtained neutron dose rates outside the accelerator rooms were several times smaller than the neutron dose rates in side the accelerator rooms. Never the less, the measured neutron dose equivalent was not negligible from the aspect of the personal dosimetry with almost 2 mSv a year per person in the areas occupied by staff (conservative estimation). In rooms with 15 MV accelerators, the neutron exposure to the personnel was significantly lower than in the rooms having 18 MV accelerators installed. It was even more pronounced in the room reconstructed after the 60Co decommissioning. This study confirms that shielding from the neutron radiation should be considered when building vaults for high energy linear accelerators, especially when the space constraints exist.

Radiation Therapy Photon Beams Dose Conformation According to Dose Distribution Around Intracavitary-Applied Brachytherapy Sources

Intracavitary application of brachytherapy sources followed by external beam radiation is essential for the local treatment of carcinoma of the cervix. Due to very high doses to the central portion of the target volume delivered by brachytherapy sources, this part of the target volume must be shielded while being irradiated by photon beams. Several shielding techniques are available, from rectangular block and standard cervix wedge to more precise, customized step wedge filters. Because the calculation of a step wedge filters shape was usually based on effective attenuation coefficient, an approach that accounts, in a more precise way, for the scattered radiation, is suggested. The method was verified under simulated clinical conditions using film dosimetry. Measured data for various compensators were compared to the numerically determined sum of the dose distribution around brachytherapy sources and one of compensated beam. Improvements in total dose distribution are demonstrated, using our method. Agreement between calculation and measurements were within 3%. Sensitivity of the method on sources displacement during treatment has also been investigated.