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Nowadays, a dose estimate for individual patients undergoing CT examination is carried out using the metric of size-specific dose estimate (SSDE), which is calculated by multiplying a volume CT dose index (CTDIvol) and a correction factor that is a function of patient size. Two CTDIvol values are based on head and body PMMA phantoms. There are also two values of correction factors (k), both for head and body PMMA phantoms. The purpose of this study was to compare the SSDE values calculated using head and body PMMA phantoms with their corresponding correction factors (k). The CTDIvol values were derived from the ImPACT 1.04 software for 12 CT scanners: Sensation 4, Sensation 16, Sensation 64, Light Speed, Light Speed 16, Light Speed VCT, Secura, Brilliance 16, Brilliance 64, Asteion Dual, Aquilion 4, and Aquilion 16. The size of the patients who underwent CT examination was characterized by a water-equivalent diameter (Dw) from 10 cm to 45 cm. The results indicated that the differenc...

Objectives:The American Association of Physicists in Medicine (AAPM) Task Groups (TG) 204 and 220 introduced a method to estimate patient dose by introducing the Size-Specific Dose Estimate (SSDE). They provided patient size-specific conversion factors that could be applied to volumetric CT Dose Index CTDIvol to estimate patient dose in terms of SSDE based on either effective diameter (Deff) or water equivalent diameter (Dw). Our study presented an alternative method to manually estimate SSDE for the everyday clinical routine chest CT that can be readily used and does not require sophisticated computer programming.Methods:For 16 adult patients undergoing chest CT, the method employed an average relative electron density (ρelung = 0.3) for the lung tissue and a ρetissue of 1.0 for the other tissues to scale the lateral thickness and compute the effective lateral thickness on the patient’s axial image. The proposed method estimated a “corrected” Deff (Deffcorr) to replace Dw and compared results with TG220 and a second method proposed by Huda et al, for the same set of CT studies.Results:The results showed comparable behavior for all methods. There is overall agreement especially between this study and TG220. Largest differences were +13.3% and+15.9% from TG220 and Huda values, respectively. Patient size correlation showed strong correlation with the TG220 and Huda et al methods.Conclusions:A simple, quick manual method to estimate CT patient radiation dose in terms of SSDE was proposed as an alternative where sophisticated computer programming is not available. It can be readily used during any clinical chest CT scanning.Advances in knowledge:The paper is novel as it presents simple, quick manual method to estimate CT patient radiation dose in chest imaging. The process can be used as alternative in cases no sophisticated computer programming is available.

Weighted and average dose within a scan volume of a phantom have been evaluated and validated using two different devices and techniques. The Barracuda electrometer and Ion Chamber techniques were applied on a 16 slice Siemens CT scanner and the results compared to the console displayed CTDIw and CTDIvol values for accuracy and compared to each other for validation purposes. With fixed exposure parameter of 130kVp and varying tube current-time products from 140mAs to 300mAs for the CT head phantom examination, there were varying deviations in both the CTDIw and CTDIvol from the two techniques. Tube currents of 140 mAs, 240 mAs and 300 mAs yielded 3.5%, 0.61% and -6.45% deviations when the respective CTDIvol values for both techniques were compared. There were mean CTDIvol of (42.3 + 8.6) mGy and (42.1 + 8.1) mGy for Barracuda and Ion Chamber techniques respectively with an average deviation of 1.4 mGy between them, when the tube current-time products were varied from 140 – 300 mAs f...

The purpose of this study was to calculate the average dose of a phantom with a diameter of 16 and 32 cm, as well as the dose distribution in the center and periphery. The results were then compared to those from the IndoseCT software. In this study, a standard PMMA phantom with a diameter variation of 16 and 32 cm was used. The phantom was scanned using fixed parameters, namely 120 kVp voltage, 100 mAs time current, 10 mm collimation width, 100 mm scan length, and 1 s tube rotation. This research was conducted at the Indriati Solo Baru Hospital using the GE CT scanner type Revolution EVO 64/128 slice. The results of this study show that for a 16 cm phantom diameter at the center position the difference in detector measurements with IndoseCT is 1.34% at the phantom edge position is 4.38% and the weighted dose is 2.59 %, while for a 32 cm phantom diameter, the difference is 8.1 percent, at the edge of the phantom it is 1.26 %, and the weighted dose is 0.62 %. Based on the results obtained from IndoseCT, it showed an insignificant difference with the measurement of radiation dose using a phantom. Overall, the difference in percentage is ±10% while the difference in percentage that is still acceptable is ±20%.

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The purpose of this study is to compare the water-equivalent diameter (Dw) and size-specific dose estimate (SSDE) obtained from CT localizer radiograph based on the step-wedge and computed tomography dose index (CTDI) phantoms. The two phantoms were scanned using a 64-slice SIEMENS Somatom CT Scanner with tube currents of 100 mA and 120 kV. The CT localizer radiographs of two phantoms were obtained. Subsequently, relationships between pixel values (PV) and water-equivalent thickness (tw) were developed. Based on those relationships, the Dw and SSDE of twenty patients were calculated from the CT localizer radiographs. The results of the Dw and SSDE measured using CT localizer radiographs based on the two phantoms were compared. The relationships between PV and tw obtained from both CT localizer radiographs of the phantoms of step-wedge and CTDI are established. The Dw and SSDE values from the CT localizer radiograph calibrated with the CTDI phantom and step-wedge phantom also have li...