[en] Mortality reduction through screening mammography (SMG) is possible only with examination of high image quality (IQ), which should be performed with acceptable patient breast radiation dose (BRD). Besides film processing control, equipment assessment with breast phantom and dosimetry, periodical external mammographic IQ assessment (MIQA) is needed, including image labelling (L), breast positioning (BP), exposure (EX) and artefacts (AR) assessment. The nationwide breast cancer screening program (NBSP) has been introduced in Croatia in 2006, and the MIQA is initiated as the first step in establishing quality assurance/quality control (QA/QC) framework in breast imaging in Croatia. The current study was aimed: (1) to provide objective evidence about the technical MIQ in NBSP in Croatia, (2) to compare MIQ between different types of mammographic units (MUs), (3) to identify the common deficiencies, and (4) to propose corrective activities. Mammograms (MGs) for IQA were collected from a total of 84 MUs which participate in NBSP, which represents 70 % of all MUs nationwide: A total of 420 MG examinations were reviewed. Each MU was requested to submit ''what they consider to be their five best representative MGs, each one performed in one of five consecutive workdays''. Mean age of MG machines was 7.76 years (range 2 - 21), with no difference between four MU types. This very first study of MIQ in Croatia corroborated our intuitive impression of inadequate IQ, staff training and equipment in many MUs nationwide. As MIQ strongly influences BC detection rate, suboptimal QA/QC always carries a risk to compromise the success of NBSP. Deficiencies in SMG, especially in ID and BP reflect different level of competency of radiological staff in Croatia. Differences in MIQ in various MU types are determined by their organization, equipment, education, working habits and motivation. More efforts are needed to train both RTs and radiologists to implement and maintain QA/QC in their institutions. (author)

[en] Constantly increasing clinical requests for CT scanning of the head on our facility continue to raise concern regarding radiation exposure of patients, especially radiosensitive tissues positioned close to the scanning plane. The aim of our prospective study was to estimate scatter radiation doses to the breast from routine head CT scans, both with and without use of lead shielding, and to establish influence of various technical and anthropometric factors on doses using statistical data analysis. In 85 patient referred to head CT for objective medical reasons, one breast was covered with lead apron during CT scanning. Radiation doses were measured at skin of both breasts and over the apron simultaneously, by the use of thermo luminescent dosimeters. The doses showed a mean reduction by 37% due to lead shielding. After we statistically analyzed our data, we observed significant correlation between under-the-shield dose and values of technical parameters. We used multiple linear regression model to describe the relationships of doses to unshielded and shielded breast respectively, with anthropometric and technical factors. Our study proved lead shielding of the breast to be effective, easy to use and leading to a significant reduction in scatter dose. (author)

[en] Most medically-related radiation is caused by diagnostic examinations, in particular by computed tomography (CT). The purpose of this research is to reduce radiation doses faced by the population frequently exposed to such procedures-those with lymphoproliferative disorders. The research was conducted comparing radiation-exposition doses received by the radiosensitive organs (thyroid, lens, breast and gonad) using the standard thoracic CT protocol with the radiation received using the low-dose protocol, while maintaining display quality. The standard-dose thoracic protocol implies 120 kV and 150 mAs. The low-dose protocol was conducted on the same device using 120 kV and 30 mAs. We confirmed the hypothesis that the use of the low-dose thoracic CT protocol leads to a reduction in radiation dose without compromising display quality. It is further expected that a reduction in doses will reduce the risk of radiation-related mutations. (author)

[en] Computed tomography (CT) is a sectional imaging technique that uses a collimated X-ray beam perpendicular to the body axis to acquire image of a body slice of desired width. CT is playing an increasingly important role in the diagnosis of a wide variety of disorders. Since its introduction, it has been known that CT is related to high radiation dose to the patient. Expanding the use of this diagnostic modality resulted in making it a major source of radiation exposure to population from diagnostic X-rays. In countries with developed healthcare it contributes up to 41 % of the annual collective dose from medical radiation exposures. Many ways are found in the literature to describe and measure radiation dose from CT. In an effort to further improve dose management in CT, European Commission published European Guidelines (EG) on quality criteria for CT. To our knowledge, there are no data currently available concerning nationwide patient doses from CT examinations in Croatia. The aim of the present work is to contribute to the establishment of diagnostic reference levels (DRLs) for various CT examinations in our country. Our survey was performed on the helical CT scanner Shimadzu X-ray CT system SCT-7800 T (Shimadzu, Japan) during 2009 and 2010. 105 adult patients took part in our survey, 44 women (42 %) and 61 men (58 %). Mean patient age was 58, ranging from 21 to 94. Each patient signed the informed consent form. Typical CT examinations, namely routine head, chest and abdomen, were selected for the study. For each examination, the parameters, such as kVp, mAs, number of slices, slice thickness, pitch and length of examined body segment were recorded. CTDI₁00 was measured with standard ionization chamber and Unfors Xi (Unfors, Sweden) measurement system. Radiation dose in mGy was multiplied with 10 cm length, equaling CTDI in mGyxcm. Results were normalized to 10 mm slice width. For our measurements we used standard polymethyl - methacrylate (PMMA) phantoms: body (320 mm in length and 160 mm in diameter) and head (160 mm in length and 160 mm in diameter). The ionization chamber used for measurements of air kerma was placed in holes extending through the length of the phantom at 3, 6, 9 and 12 hours and at the phantom's central axis. We found that the scanning length L was longest for abdominal CT scans, which was expected, since abdomen is the largest anatomical region. In the abdominal protocol, L also had a broadest range of values (22 - 66 cm), probably because of a variable size of the field of interest. L for thorax had narrower range (25 - 44 cm), mostly because of the difference in patient size. For head protocol, L was relatively constant (15 - 26 cm). Starting point for the optimization of CT practices is the training of radiology personnel. Properly educated technologist can adjust technical parameters and length of an irradiated part of the body, therefore reducing the dose burden. hrough better cooperation with other clinical specialties, it is possible to narrow down the scanning area and lower the number of examination phases. That can also contribute to dose reduction. Some examinations were performed in phases, before and after intravenous contrast media application. For such patients we doubled or tripled the radiation dose, depending on weather scanning was done in two or three phases. The abdominal CT examination was significantly above the EC RDL concerning DLP, and slightly higher with CTDI values. That can probably be attributed to longer then needed examined body segment. Higher RDL-s were also recorded with a head CT. Since RDL-s act as parameters to help identify relatively poor or inadequate use of the technique, the exposure settings and the extent of the scan should be further investigated to lower the dose without affecting image quality. It should be noted that CT RDL-s should be monitored at certain time intervals to constantly assure optimization of the procedure. We believe that our measurements provide a good basis for further investigation of radiation doses from CT scanners in Croatia. We hope to expand our survey in near future to include more radiology departments in Zagreb and other regional medical centers in Croatia. (author)