Urbana stabla i šume doprinose kvaliteti života stanovnika urbanog područja i pružaju brojne koristi. Međutim, stabla u urbanim područjima su izložena različitim abiotskim i biotskim poremećajima ...koji utječu na njihov razvoj. Gljive truležnice se ističu kao bitan uzročnik pojave loma stabla. Dijagnostički instrumenti koji mjere određena svojstva drva se koriste u arborikulturi kao dopuna vizualnoj prosudbi urbanih stabala. Zvučni tomograf je uređaj koji mjeri brzinu prolaska zvučnih valova kroz drvo u radijalnom i tangentnom smjeru kako bi se prosudile unutarnje greške drva. Cilj istraživanja je bio odrediti veličinu i položaj zdravog i trulog drva te odrediti točnost zvučnog tomografa kod deset stabala hrasta kitnjaka u Parku Maksimir u Zagrebu. Usporedili smo rezultate grafičkih prikaza zvučnog tomografa (tomograme) sa fotografijama presjeka panjeva stabala koja su posječena radi potvrde truleži drva. Trulež drva je bila vidljiva na osam od deset istraživanih stabala koji su imali simptome truleži pri vizualnom pregledu. Trulež drva je potvrđena kod sedam stabala na panjevima nakon sječe. Kod tri stabla zabilježen je početni stadij truleži drva, dok su četiri stabla imala aktivnu trulež drva i pojavu šupljina. Oblik tomograma odgovarao je fotografijama presjeka panjeva kod osam stabala, a pozicija trulog drva je odgovarala fotografijama presjeka panjeva kod devet stabala. Područje trulog drva različitih kategorija je bilo točno prepoznato na tomogramima za šest od deset istraživanih stabala. Zvučni tomograf je podcijenio površinu zdravog drva, precijenio površnu drva u početnim stadijima truleži i točno predstavio područja s aktivnom truleži drva i šupljinama.
Urban trees and forests contribute to citizens’ wellbeing and provide a wide range of benefits. Yet in the urban environment, trees are exposed to a range of abiotic and biotic factors that can impair growth. Wood decay fungi are a major cause of tree failure. Devices supported methods that measure certain wood properties are often used in addition to visual assessment of urban trees. Acoustic tomography is a device that measures the velocity of sound wave propagation through wood in the radial and tangential directions and is used to assess internal defects in trees. The aims of this study were to determine the size and position of healthy and decayed wood and to define the accuracy of acoustic tomography on ten old sessile oak trees in the Maksimir Forest Park, Zagreb. Results of acoustic tomography images (tomograms) were compared with photographs of tree cross sections after felling to confirm decay. The visual assessment indicated the presence of decay on ten trees, and this decay was visible on eight of ten tomograms. Decay was further confirmed in seven cross-sections after felling. Of these, three trees had incipient wood decay, while four had active wood decay with cavity formations. The shape of tomograms and position of decay were similar to the cross-section photographs for eight and nine trees, respectively. The area of decayed wood in different wood condition categories was correctly shown on the tomograms in comparison with the cross-section photographs in six of the trees. Acoustic tomography underestimated the area of sound wood and overestimated incipient wood decay in comparison with the actual state of cross-sections, while the area of active degraded wood and cavities was accurately represented.
To investigate the relationship of the effective dose and dose area product (DAP) in dental cone beam computed tomography (CBCT) examinations and to propose conversion factors for estimation of ...effective doses of the patients using DAP. Dependence of organ doses on DAP was also investigated.
Different exposure geometries in Cranex3Dx CBCT device were simulated using Monte Carlo simulation and computational anthropomorphic phantom. Then organ doses and effective dose for every exposure geometry was compared to DAP and analysed.
The effective dose in all simulated CBCT protocols and positions with 180° tube rotation ranged from 5 μSv for 50 × 50 mm
field of view (FOV) localised on one tooth using lowest resolution to 265 μSv for the largest FOV and highest resolution. In case of 360° tube rotation the effective dose ranges from 6 to 332 μSv for the same FOV sizes and positions as well as resolutions as in 180° tube rotation.
Though the DAP introduces a large uncertainty in the risk measure in dental CBCT, it represents the dose and FOV size which are the most important scanning parameters affecting the dose. To decrease uncertainty in the risk measure, the effective dose has to be estimated for usual clinical positions of the FOV.
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