Larger Effective Dose Research Articles

Effective dose and image quality for intraoperative imaging with a cone-beam CT and a mobile multi-slice CT in spinal surgery: A phantom study.

To compare the effective dose (ED) and image quality (IQ) of O-arm cone-beam CT (Medtronic, Minneapolis, MN, USA) and Airo multi-slice CT (Brainlab AG, Munich, Germany) for intraoperative-CT (i-CT) in spinal surgery. The manufacturer-defined protocols available in the O-arm and Airo systems for three-dimensional lumbar spine imaging were compared. Organ dose was measured both with thermo-luminescent dosimeters and GafChromic films in the Alderson RadiationTherapy anthropomorphic phantom. A subjective analysis was performed by neurosurgeons to compare the clinical IQ of the anthropomorphic phantom images acquired with the different i-CT systems and imaging protocols. Image uniformity, noise, contrast-to-noise-ratio (CNR), and spatial resolution were additionally assessed with the Catphan 504 phantom. O-arm i-CT caused 56% larger ED than Airo due to the high definition (HD) imaging protocol. The noise was larger for O-arm images leading to a lower CNR than that measured for Airo. Moreover, scattering and beam hardening effects were observed in the O-arm images. Better spatial resolution was measured for the O-arm system (9 lp/cm) than for Airo (4 lp/cm). For all the investigated protocols, O-arm was found to be better for identifying anatomical features important for accurate pedicle screw positioning. According to phantom measurements, the HD protocol of O-arm offered better clinical IQ than Airo but larger ED. The larger noise of O-arm images did not compromise the clinical IQ while the superior spatial resolution of this system allowed a better visibility of anatomical features important for pedicle screw positioning in the lumbar region.

Doses in eye lens, thyroid, and gonads, due to scattered radiation, during a CT radiodiagnosis study

X-ray images used for radio-diagnosis are very useful to evaluate the progress of a treatment or to have a better diagnosis. However, during the interaction between the incoming X-ray beam and the body surface, part of the radiation is scattered out reaching other parts of the body delivering an undesirable dose. In this work the dose in eye lenses, thyroid, and gonads of a solid water phantom was measured using thermoluminescent dosimeters, while a Computer Tomography of the torso was obtained. With the measured absorbed dose the effective dose was calculated. Thus, the effective dose in the eye lens, thyroid, and gonads is approximately 57, 214 and 9 μSv respectively. The largest effective dose was on that area located nearest to the region where the radiation is scattered.

Radon Exposures in the Caves of Tenerife (Canary Islands)

There are more than a hundred volcanic caves and pits of various lengths on the island of Tenerife (Canary Islands. Spain). The results are presented of atmospheric radon measurements performed in three of these caves and in three pits. One of the caves selected, El Viento Cave, is nearly 20 km in length and is the longest volcanic tube in the Canarian archipelago and the second longest in the world. The measurements were performed over two distinct periods during the year using passive polycarbonate detectors. The mean radon concentrations range between 0.3 and 8 kBq.m 3 , the maximum value corresponds to a site located at 1850 m from the mouth of El Viento Cave. Possible touristic development of these caves has been taken into account in estimating the effective doses for visitors and guides (considered separately). The values obtained range from 0.3 to 100 μSv per visit for visitors. The largest effective dose would correspond to that for guides at 41 mSv.y -1 in the Viento Cave. This result would make protection against radiological hazards obligatory if the cave were to be developed as a site for tourism.

Molecular mechanism of hexane neuropathy: significant differences in pharmacokinetics between 2.3-, 2.4-, and 2.5-hexanedione.

Hexane neuropathy is thought to be produced through the direct action of its metabolite, 2, 5-hexanedione (2, 5-HD), on nervous tissues. 7-Diketones in-cluding 2, 5-HD are reported to be neurotoxic, whereas α, β, and δ-diketones are reported to be not. Experiments were designed to investigate the specificity of the y-diketones in terms of pharmacokinetics. 2, 3-HD (a-diketone), 2, 4-HD (α-diketone), and 2, 5-HD (7-diketone) were tested in this study. Aqueous solutions containing 0.5% of each HD were administered to rats by gavage. HDs in blood, brain, and sciatic nerve were determined at specific intervals after gavage by the extraction method with chloroform or the direct injection method using gas chromatography-mass spectrometry.Examination of tissue distribution revealed that 2, 5-HD was not selectively re-tained by nervous tissues. However, 2, 5-HD had higher concentrations and much longer elimination times in both blood and nervous tissues than 2, 3-HD and 2, 4-HD. Therefore, for an identical dose, 2, 5-HD has a much larger effective dose (con-centration in tissue x time retained by tissue) than 2, 3-HD and 2, 4-HD. These results suggest that the specific neurotoxicity of the 7-diketones is due to their pharmackinetic specificity.