Objectives: Cone beam CT (CBCT) in dentistry and maxillofacial surgery is a widely used imaging method for the assessment of various maxillofacial and dental pathological conditions. The objective of this study was to summarize the results of a multinational retrospective–prospective study that focused on patient exposure in this modality. Methods: The study included 27 CBCT units and 325 adult and paediatric patients, in total. Data on patients, clinical indications, technical parameters of exposure, patient dose indicator, or, alternatively, dose to phantom were collected. The dose indicator used was air kerma–area product, PKA. Results: In most scanners operators are offered with a variety of options regarding technical parameters, especially the field of view size. The median and the third quartile value of PKA for adult patients in 14 different facilities were 820 mGy cm² and 1000 mGy cm² (interquartile range = 1058 mGy cm²), and 653 mGy cm² and 740 mGy cm² (interquartile range = 1179 mGy cm²) for children, as reported by four different institutions. Phantom dose data were reported from 15 institutions, and median PKA ranged from 125 mGy cm² to 1951 mGy cm². Median PKA values varied by more than a 10-fold between institutions, mainly due to differences in imaging protocol used, in particular field of view and tube current-exposure time product. Conclusions: The results emphasize the need for a cautious approach to using dental CBCT. Imaging only when the clinical indications are clear, accompanied with the appropriate radiographic techniques and the optimum imaging protocol, will help reduce radiation dose to patients.
The aim of this study is to compare four dosimetry methods for wide-beam multi-detector computed tomography (MDCT) in terms of computed tomography dose index free in air (CTDI free-in-air) and CTDI measured in phantom (CTDI phantom). The study was performed with Aquilion One 320-detector row CT (Toshiba), Ingenuity 64-detector row CT (Philips) and Aquilion 64 64-detector row CT (Toshiba). In addition to the standard dosimetry, three other dosimetry methods were also applied. The first method, suggested by International Electrotechnical Commission (IEC) for MDCT, includes free-in-air measurements with a standard 100-mm CT pencil ion chamber, stepped through the X-ray beam, along the z-axis, at intervals equal to its sensitive length. Two cases were studied-with an integration length of 200 mm and with a standard polimetil metakrilat (PMMA) dosimetry phantom. The second approach comprised measurements with a twice-longer phantom and two 100-mm chambers positioned and fixed against each other, forming a detection length of 200 mm. As a third method, phantom measurements were performed to study the real-dose profile along z-axis using thermoluminescent detectors. Fabricated PMMA tube of a total length of 300 mm in cylindrical shape containing LiF detectors was used. CTDI free-in-air measured with an integration length of 300 mm for 160 mm wide beam was by 194 % higher than the same quantity measured using the standard method. For an integration length of 200 mm, the difference was 18 % for 40 mm wide beam and 14 % for 32 mm wide beam in comparison with the standard CTDI measurement. For phantom measurements, the IEC method resulted in difference of 41 % for the beam width 160 mm, 19 % for the beam width 40 mm and 18 % for the beam width 32 mm compared with the method for CTDI vol. CTDI values from direct measurement in the phantom central hole with two chambers differ by 20 % from the calculated values by the IEC method. Dose profile for beam widths of 40, 32 and 16 mm, and analysis and conclusions are presented.
Computed tomography urography (CTU) is a very detailed and powerful method of investigating the urinary tract, but an individual approach to each patient is recommended considering also the radiation dose. This article aims to present the initial experience from the diagnosis of urinary tract diseases and congenital variants in the anatomy of the urinary system using low-kV protocols. The image quality and patient dose in CTU were compared when replacing the standard 120-kV protocol with two different low-kV protocols. Totally, 91 patients (41 women and 55 men) with mean age 56.4 were studied with three different low-dose protocols. The patients underwent an unenhanced and excretory low-dose phases and standard corticomedullary and nephrographic phases. Effective dose was reduced by more than 65 % using the 100-kV protocol and by more than 76 % with introduction of 80-kV protocol. At the same time, patient images obtained with the new low-kV protocols maintained their diagnostic quality.
The aim of the present study was to compare image quality and patient dose in cardiac computed tomography angiography (CTA) in terms of volume computed tomography dose index (CTDI vol), dose length product (DLP) and effective dose, when changing from filtered back projection (FBP) to adaptive iterative dose reduction (AIDR) reconstruction techniques. Further aim was to implement prospective electrocardiogram (ECG) gating for patient dose reduction. The study was performed with Aquilion ONE 320-row CT of Toshiba Medical Systems. Analysis of cardiac CT protocols was performed before and after integration of the new software. The AIDR technique showed more than 50 % reduction in CTDIvol values and 57 % in effective dose. The subjective evaluation of clinical images confirmed the adequate image quality acquired by the AIDR technique. The preliminary results indicated significant dose reduction when using prospective ECG gating by keeping the adequate diagnostic quality of clinical images.
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