Milojko Kovacevic

Mammography radiation dose: initial results from Serbia based on mean glandular dose assessment for phantoms and patients

The primary objective of this study is to investigate the actual mammography dose levels in Serbia and establish a baseline dose database for the future screening programme. The mean glandular dose (MGD) was assessed for standard size breast substituted by 45 mm polymethyl methacrylate (PMMA) phantom and imaged under typical clinical conditions at 30 screen-film mammography facilities. Average MGD was (1.9 +/- 1.0) mGy, with a range of 0.12-5.2 mGy. These results were used for the calculation of the initial diagnostic reference levels in mammography in Serbia, which was set to 2.1 mGy for a standard breast. At some facilities, high doses were observed and the assessed MGD was supplemented by a patient dose survey. MGD was measured for 53 women having a diagnostic mammography in cranio-caudal (CC) and mediolateral oblique (MLO) projections at the largest mammography facilities in Serbia. The parameters recorded were: age, compressed breast thickness, tube potential (in kV), tube loading (in mAs) and the MLO projection angle. The average MGD per image was 2.8 mGy for the CC projection and 4.3 mGy for the MLO projection. Dose to breast was compared with dose for PMMA phantoms of various sizes, assessed at the same facilities. The results have indicated that phantom dose values can assist in setting optimisation activities in mammography. Both phantom and patient dose values indicated unnecessary high doses in facilities with an extremely high mammography workload. For these facilities, urgent dose-reduction measures and follow-up actions were recommended.

A survey of patient doses from conventional diagnostic radiology examinations: first results from Serbia and Montenegro

Diagnostic reference levels provide framework to reduce variability. The aim of this study is to establish, for the first time, a baseline for national diagnostic reference levels in Serbia and Montenegro for the most common X-ray examination types. Measurements of patient dose using kerma-area product meter and entrance surface air kerma assessment were performed on at least ten patients for each examination type, in each of 16 randomly selected hospitals in Serbia and Montenegro, so that a total of 3,026 procedures for nine different examination categories were included in the survey. Exposure settings and individual data were recorded for each patient. Mean, median and third quartile values of patient doses are reported. Results have shown wide variation of mean hospital doses, with factor of four for barium enema to 23 for thoracic spine radiography. Entrance surface air kerma were compared with previously published diagnostic reference levels (DRL) proposed by Commission of European Communities (CEC). Doses for all studied examination types except chest radiography were within European DRL. The reasons for dose variation are discussed. Survey data are aimed to help in development of an on-going national quality assurance and quality control programme in diagnostic radiology. The findings emphasize the importance of regular patient dose measurement to ensure that patient doses are kept as low as reasonable achievable.

Sensitivity of P-Channel MOSFET to X- and Gamma-Ray Irradiation

Investigation of Al-gate p-channel MOSFETs sensitivity following irradiation using 200 and 280 kV X-ray beams as well as gamma-ray irradiation of 60Co in the dose range from 1 to 5 Gy was performed in this paper. The response followed on the basis of threshold voltage shift and was studied as a function of absorbed dose. It was shown that the most significant change in threshold voltage was in the case of MOSFET irradiation in X-ray fields of 200 kV and when the gate voltage was

Contribution of activation products to occupational exposure following treatment using high-energy photons in radiotherapy

When high-energy photon beams are used for irradiation in radiotherapy, neutrons that are the result of photonuclear reactions create activation products that affect the occupational dose of radiotherapy staff. For the assessment of activation products in situ gamma spectroscopy was performed parallel to dose-rate measurements following irradiation, by using a high-energy photon beam from a linear accelerator Elekta Precise (Elekta, Stockholm, Sweden) used in radiotherapy. The major identified activation products were the following radioisotopes: (28)Al, (24)Na, (56)Mn, (54)Mn, (187)W, (64)Cu and (62)Cu. Based on the typical workload and dose-rate measurement, the assessed additional annual occupational dose ranged from 1.7 to 0.25 mSv. As the measured dose rate arising from the activation products rapidly decreases as a function of time, the assessed additional dose is negligible after 10 min following irradiation. To keep the occupational dose as low as reasonably achievable, it is recommended to delay entrance to the therapy room at least 2-4 min, when high-energy photons are used. This would reduce the effective dose by 30%.

Environmental radioactivity in southern Serbia at locations where depleted uranium was used

Abstract In the 1999 bombing of the Federal Republic of Yugoslavia, NATO forces used ammunition containing depleted uranium. The cleaning of depleted uranium that followed was performed in southern Serbia by the Vinča Institute of Nuclear Sciences between 2002 and 2007 at the locations of Pljačkovica, Borovac, Bratoselce, and Reljan. This paper presents detailed results of radioactivity monitoring four years after cleaning (2011), which included the determination of gamma emitters in soil, water, and plant samples, as well as gross alpha and beta activities in water samples. The gamma spectrometry results showed the presence of natural radionuclides 226Ra, 232Th, 40K, 235U, 238U, and the produced radionuclide 137Cs (from the Chernobyl accident). In order to evaluate the radiological hazard from soil, the radium equivalent activity, the gamma dose rate, the external hazard index, and the annual effective dose were calculated. Considering that a significant number of people inhabit the studied locations, the periodical monitoring of radionuclide content is vital. Sažetak U napadu na Saveznu Republiku Jugoslaviju 1999. godine NATO-ove su snage koristile municiju s osiromašenim uranom. Od 2002. do 2007. Laboratorij za zaštitu od zračenja i zaštitu životne sredine Instituta Vinča proveo je akciju čišćenja osiromašenog urana na lokacijama Pljačkovica, Borovac, Bratoselce i Reljan. U ovom se radu iznose detaljni rezultati praćenja radioaktivnosti u južnoj Srbiji četiri godine nakon spomenute akcije čišćenja (2011), koji uključuje određivanje gama zračenja u uzorcima zemljišta, vode i biljki te određivanje ukupne alfa i beta aktivnosti u uzorcima vode. Rezultati gama spektrometrije pokazali su prisutnost prirodnih radionuklida: 226Ra, 232Th, 40K, 235U, 238U i proizvedenog radionuklida 137Cs. Za procjenu radijacijskog rizika iz zemljišta izračunati su ekvivalent radija, brzina apsorbirane doze gama zračenja, indeks radijacijskog rizika uslijed vanjskog izlaganja i efektivna doza zračenja. Imajući u vidu da na ispitivanim područjima živi znatan broj ljudi, iznimno je važno da se ondje periodično prati sadržaj radionuklida.

A radiological incident with a radioactive lightning rod source found in a vehicle used by film crewmembers: a case study

An overview of radiological incident involving radiation source from a lightning rod (152Eu/154Eu), together with dose estimation for individuals exposed to ionising radiation is given in the paper. The cause of the incident was an orphaned source from a lightning rod. The dose received by individuals was assessed using a retrospective dosimetry technique, based on the information on behaviour of individuals and results of dose rate measurements in the vicinity of the source. Several people have been exposed to relatively high dose rates for an extended period of time. The conservatively estimated cumulative dose values for two categories of individuals were 50 and 40 mSv, respectively, which are significantly higher than annual dose limit for public exposure of 1 mSv. The need to identify radioactive sources incorporated in radioactive lightning rods, to maintain control and accountability and to remove and dispose of them properly along with appropriate record keeping in Serbia was highlighted. These activities would reduce the probability of occurrence of radiation incidents in Serbia.

Patient Dosimetry and Image Quality in Conventional Diagnostic Radiology: A Practical Optimization Experience from a Serbian Hospital

The optimization of image quality vs. patient dose is an important task in medical imaging. Maximal validity of optimization has to be based on clinical images. Simultaneous measurement of patient dose levels and image quality assessment is used to investigate possibilities for dose reduction and maintain image quality. The survey was conducted in a general hospital performing more than 60000 images annually and representing typical Serbian practice. For five most frequent diagnostic projections patient exposure was measured using kerma area product meter. Image quality was assessed by experienced radiologists using “European Guidelines on Quality Criteria for Diagnostic radiographic Images”. Following examination types were included into the survey: chest PA, chest LAT, pelvis AP, lumbar spine AP, lumbar spine LAT and pelvis. Comparing actual radiographic technique with recommended technique in European Guidelines, modification of practice was proposed and implemented and image quality was re-assessed. At least 10 adult patients were followed for each projection, before and after corrective actions. Large dose saving without compromising diagnostic information were found for some examination types, showing that this simple method is very efficient dose reduction tool in conventional diagnostic radiology. Also, need for staff training and difficulties related to practical implementation of optimization methods in Serbia were discussed.

Investigation On The Soil Profile Around DU Projectile Three Years After Contamination

Abstract. During the war conflict at former Yugoslavia territory in 1999, depleted uranium (DU) ammunition was used by NATO air forces and the Bratoselce site have been contaminated. Three years later decontamination of the location had been undertaken. During cleaning up the site, samples of projectile and soil samples around it, along the depth profile and parallel to the projectile centerline were collected and analyzed by gamma and alpha spectrometry. Measurements were performed by gamma spectrometry system (HP Ge detector, efficiency 23%) and high-resolution alpha spectrometry systems (PIPS detectors, efficiency 7% and 15%). Concentrations of present uranium, radium and plutonium isotopes were determined and compared with naturally occurring levels of the location investigated. Results indicate that high DU contamination of the soil layers next to the penetrator decrease rapidly with the distance to the 1% of initial values that is about double background levels for the investigated location.