With increasing use of CT in children and a lack of use of appropriateness criteria, there is a strong need to implement guidelines to avoid unnecessary radiation doses to children.
The article reports results from the largest international dose survey in paediatric computed tomography (CT) in 32 countries and proposes international diagnostic reference levels (DRLs) in terms of computed tomography dose index (CTDI vol) and dose length product (DLP). It also assesses whether mean or median values of individual facilities should be used. A total of 6115 individual patient data were recorded among four age groups: <1 y, >1-5 y, >5-10 y and >10-15 y. CTDIw, CTDI vol and DLP from the CT console were recorded in dedicated forms together with patient data and technical parameters. Statistical analysis was performed, and international DRLs were established at rounded 75th percentile values of distribution of median values from all CT facilities. The study presents evidence in favour of using median rather than mean of patient dose indices as the representative of typical local dose in a facility, and for establishing DRLs as third quartile of median values. International DRLs were established for paediatric CT examinations for routine head, chest and abdomen in the four age groups. DRLs for CTDI vol are similar to the reference values from other published reports, with some differences for chest and abdomen CT. Higher variations were observed between DLP values, based on a survey of whole multi-phase exams. It may be noted that other studies in literature were based on single phase only. DRLs reported in this article can be used in countries without sufficient medical physics support to identify non-optimised practice. Recommendations to improve the accuracy and importance of future surveys are provided.
Background: There is a paucity of real-time imaging modalities available for the bronchoscopic biopsy of peripheral lung nodules. We aim to demonstrate the feasibility of the O-arm imaging system to guide real-time biopsies of peripheral lung nodules during electromagnetic navigation bronchoscopy. Methods: A retrospective review was performed at 2 academic medical centers utilizing O-arm guidance. Results: The average nodule size was 2.1×2.0 cm and were mostly solid (66%) with a positive bronchus sign (83%). O-arm imaging confirmed tool-in-lesion in all cases. The diagnostic yield was 33%. Four cases were nondiagnostic of the 6 cases performed. In these cases, necrotic tissue was the most common (75%) and showed resolution following subsequent imaging. The average 3-dimensional (3D) spin time was 23.5 seconds. The average number of 3D spins performed per case was 4.33. The average effective dose per 3D spin was 3.73 mSv. Conclusion: We have demonstrated the O-arm’s feasibility with electromagnetic navigation bronchoscopy for peripheral lung nodules. The O-arm was able to confirm tool-in-lesion in all cases which added confidence to the biopsy. Four high-resolution 3D spins per case may limit the total computed tomography effective dose. We also noted that both metal and radiation scatter were minimal when appropriate radiation safety standards were met. Although additional experience and data will be required to verify the O-arm approach for routine use, our initial experience is promising.
Various methods, such as those developed by the Medical Internal Radiation Dosimetry (MIRD) Committee of the Society of Nuclear Medicine or employing dose point kernels, have been applied to the radiation dosimetry of (131)I radionuclide therapy. However, studies have not shown a strong relationship between tumour absorbed dose and its overall therapeutic response, probably due in part to inaccuracies in activity and dose estimation. In the current study, the GATE Monte Carlo computer code was used to facilitate voxel-level radiation dosimetry for organ activities measured in an (131)I-treated thyroid cancer patient. This approach allows incorporation of the size, shape and composition of organs (in the current study, in the Zubal anthropomorphic phantom) and intra-organ and intra-tumour inhomogeneities in the activity distributions. The total activities of the tumours and their heterogeneous distributions were measured from the SPECT images to calculate the dose maps. For investigating the effect of activity distribution on dose distribution, a hypothetical homogeneous distribution of the same total activity was considered in the tumours. It was observed that the tumour mean absorbed dose rates per unit cumulated activity were 0.65E-5 and 0.61E-5 mGY MBq(-1) s(-1) for the uniform and non-uniform distributions in the tumour, respectively, which do not differ considerably. However, the dose-volume histograms (DVH) show that the tumour non-uniform activity distribution decreases the absorbed dose to portions of the tumour volume. In such a case, it can be misleading to quote the mean or maximum absorbed dose, because overall response is likely limited by the tumour volume that receives low (i.e. non-cytocidal) doses. Three-dimensional radiation dosimetry, and calculation of tumour DVHs, may lead to the derivation of clinically reliable dose-response relationships and therefore may ultimately improve treatment planning as well as response assessment for radionuclide therapy.
PurposeIn this work, gold nanoparticles (GNPs) were embedded in the MAGIC-f polymer gel irradiated with the 192Ir brachytherapy sources.Material and methodsAt the first plexiglas phantom was made as the human pelvis. The GNPs were synthesized with 15 nm in diameter and 0.1 mM (0.0197 mg/ml) in concentration by using a chemical reduction method. Then, the MAGIC-f gel was synthesized. The fabricated gel was poured into the tubes located at the prostate (with and without the GNPs) locations of the phantom. The phantom was irradiated with 192Ir brachytherapy sources for prostate cancer. After 24 hours, the irradiated gels was read by using Siemens 1.5 Tesla MRI scanner. Following the brachytherapy practices, the absolute doses at the reference points and isodose curves were extracted and compared by experimental measurements and Monte Carlo (MC) simulations.ResultsThe mean absorbed doses in the presence of the GNPs in prostate were 14% higher than the corresponding values without the GNPs in the brachytherapy. The gamma index analysis (between gel and MC) using 7%/7 mm was also applied to the data and a high pass rate achieved (91.7% and 86.4% for analysis with/without GNPs, respectively).ConclusionsThe real three-dimensional analysis shows the comparison of the dose-volume histograms measured for planning volumes and the expected one from the MC calculation. The results indicate that the polymer gel dosimetry method, which developed and used in this study, could be recommended as a reliable method for investigating the dose enhancement factor of GNPs in brachytherapy.
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