This study sought to assess patient and operator eye lens doses in diagnostic coronary angiography (DCA) and percutaneous coronary interventions (PCI) in a University hospital in Oman. Kerma area product (PkA), cumulative air kerma (CAK) and fluoroscopic time (FT) were retrospectively recorded from the DICOM header for 264 patients. The median (interquartile range) of FT, PKA and CAK were: 5.3 min (2.6-10.5), 60.9 Gy cm2 (41.3-91.4) and 0.86 Gy (0.61-1.29), respectively, for DCA procedures, and they were 20.2 min (13.3-30.1), 174.0 Gy cm2 (113.7-253.3) and 2.6 Gy (1.8-3.9), respectively, for PCI procedures. The results revealed wide variability in patient doses among individual patients. Monitoring and recording patient dose data can be valuable for quality assurance and patient safety purposes. Feedback to the operator may help optimize radiation doses to patients and prompt further action, as needed.
1032 Objectives MIRD Pamphlet 15 published a revised head phantom for absorbed fraction and S-value calculations. The calculations were carried out with the EGS code. To the best of our knowledge, they have not been compared with other codes. In this study, we implemented the phantom with MCNPX and compared the absorbed fractions from the two codes. Methods The phantom is a stylized model created with mathematical surfaces. Except for the back of the head and the thyroid, the MIRD surfaces are supported by MCNPX. For the unsupported surfaces, we approximated each with a series of right elliptical cylinders. A simple body was included to account for backscattering. The photon source was uniformly distributed in each source organ and it was visually cross-checked by plotting 1000 of their positions. When the target organ and the source organ were different, we used the F6 track length estimator to obtain the energy deposition; when they were the same, the *F8 pulse height tally was used. The photons and electrons were tracked until they were below their MCNPX default cut-off energies. Results The relative errors of the absorbed fractions from the simulations were generally below 1 %. For most of the values, the differences between this work and MIRD vary from less than 1 % to about 15 %. There are several target/source combinations showing significant differences, up to 60 % in the worst case. These large discrepancies were not affected by the tally choice nor by the energy indexing scheme. It could not be explained by the small difference in the organ volumes either. Conclusions MCNPX is a well-validated Monte Carlo code in medical physics applications. For most of the target/source combinations, the MCNPX calculated absorbed fractions are comparable to the MIRD ones. However, we found significant discrepancies in some cases. These large discrepancies warrant further investigation.
The use of pediatric CT that had recently emerged as a valuable imaging tool has increased rapidly with an annual growth estimated at about 10% per year. Worldwide, there is a remarkable increase in the number of CT examinations performed. The purposes of this study are to: (i) to measure the radiation dose and estimate the effective doses to pediatric patients during CT for chest, abdomen and brain.A total of 182 patients were investigated. CT scanners that participated in this study are helical CT scanners (64 slices, 16 slices and dual slices). Organ and surface dose to specific radiosensitive organs were estimated by using software from National Radiological Protection Board (NRPB).For all patients, the age was ranged between 1.12 month-10.0 years while the weight was ranged between 5.0 kg to 29.0 kg. The DLP was 320.58 mGy·cm, 79.93 mGy·cm, 66.63 mGy·cm for brain, abdomen and chest respectively. The effective dose was, 2.05, 1.8, 1.08 mSv for brain, abdomen and chest respectively.The patient dose is independent of CT modality and depends on operator experience and CT protocol. The study has shown a great need for referring criteria, continuous training of staff in radiation protection concepts. Further studies are required in order to establish a reference level in Sudan.
Small field (≤ 4 × 4 cm) photon radiotherapy treatments include intensity-modulated radiation therapy (IMRT)and stereotactic body radiation therapy (SBRT). These require small, high spatial resolution dosimeters of adequate dynamic range. In this study, field sizes of 1 cm ×
1 cm, 2 cm × 2 cm, 3 cm × 3 cm, 4 cm × 4 cm, and 10 cm × 10 cm have been investigated using commercially available silica-based fibres and glass beads (GB) as TL dosimeters and a Varian linear accelerator operating at 6, 10 and 15 MV. Ge-doped SiO2 fibres have previously been shown by this group to offer a viable system for use as dosimeters. The fibres and GB, offer good spatial resolution (∼120 μm and
2 mm respectively), large dynamic dose range (with linearity from tens of mGy up to well in excess of many tens of Gy), a non-hygroscopic nature and low cost. The
main aim of this present work is to investigate the use of Ge-doped optical fibres and GBs as thermoluminescence dosimeters in small photon fields for different photon beam energies, comparing the measurements against Gafchromic films, hospital commissioning data obtained from small
ionisation chambers and photon diodes and Monte Carlo simulations with FLUKA and BEAMnrc.
Breast density is an important breast cancer risk factor related to decreased mammography sensitivity and as an independent risk factor. This research aims to establish the distribution of breast density in the Saudi screening population and to identify the relationship between visual and automated breast density methods. Screening mammograms from 2905 cancer-free women were retrospectively collected from the Saudi National Breast Cancer Screening Programme. Breast density of screening mammograms were assessed visually by 11 radiologists using the Breast Imaging and Reporting Data System (BIRADS) 5th edition and Visual Analogue Scale (VAS), and by automated methods; predicted VAS processed (pVASprocessed), predicted VAS raw (pVASraw) and VolparaTM. The relationship between breast density methods was assessed using the intra-class coefficient (ICC) and weighted kappa (κ). Results indicated that around one-third of Saudi women of screening age had high breast density (BI-RADS C/D: 31.5% or Volpara Density Grade (VDG) C/D: 29.0%). Full screening mammograms from 1022 women were used to assess the relationship between all methods. Predicted VAS estimates of percent density were generally lower than VAS. The highest ICC was between VAS and pVASraw (ICC=0.86, 95% CI 0.84-0.88). For categorical breast density methods, VDG 5th edition showed fair agreement with BI-RADS 5th edition (κ=0.35, 95% CI 0.29-0.39). In conclusion, this study shows the majority of Saudi women of screening age have low breast density as shown by visual and automated methods, and there is a positive relationship between visual and automated methods, being strongest for VAS and pVASraw.
1701 Objectives The objectives of this study are to measure the ambient radiation and patient dose during whole body bone scintigraphy, thyroid and renal scan procedures. Methods Staff radiation exposure personnel were calculated as a function of administered dose distance from the patient and at different times after the administration and workload. A calibrated survey meter and thermoluminancent dosimeters (TLDs- GR200A) were used to measure the ambient dose and staff dose, respectively. Prior to measurements, all TLD were calibrated in terms of air kerma free-in-air under reproducible reference condition using 99m Tc with activity 10 mCi (370 MBq). Quality control performed before administration of the radiopharmaceutical and doses are carefully calculated. All scan procedures were performed using MiE single head gamma camera (Orbiter 37 Gamma camera) after administration of 20 mCi, 4 mCi and 5 mCi of 99mTc. Results The average ambient dose equivalent rate equal to about 12, 25 and 10 μSv/h was obtained at distance of 1 m, at 1.3 m from patient during bone, renal and thyroid scan respectively. Injection room and hot lab has ambient dose equivalent rates of 1.0 and 30 μSv/h at the same order. The maximum dose were recorded at the reception area equal to 180 μSv/h. Staff may exposed to a dose range from 8.0 to 12.5 mSv annually. Knowledge of ambient dose values is crucial in order to determine exposure personnel who may limit the time spent at high dose areas. The dose values are within the safety limit in the light of the current practice. Conclusions Although, the ambient dose is high compared to previous studies, the staff exposure was below the annual dose limits in the light of the current workload. Appropriate isolation of the patients, training of staff and a strict compliance with the established radiation safety standards are crucial in order to avoid unnecessary radiation exposure. Research Support College of Applied Medical Sciences Research Centre and Deanship of Scientific Research at King Saud University
In interventional medical procedures, other than the highly important issue of optimizing image quality and patient exposure using the primary beam, there remains a continuing need for the study of staff exposure from the scattered radiation. Herein, investigation is made of the 3D stray-radiation distribution, the simulation being made of a realistic interventional scenario through use of the Monte Carlo code Geant4 (version 10.3). The simulation is conducted based on the high definition reference Korean-man (HDRK-man) computational phantom and a GE Infinia 3/8” C-arm machine, focusing on the effect of variation of kVp and field of view (FoV) on the scattered particles’ spatial distribution. With direct measurement of the absorbed dose remaining challenging, not least in respect of the organs at risk, we computed the scatter fractions, defined as the ratio of the air kerma free-in-air to the entrance surface air kerma (ESAK), which are both easily quantifiable. Scatter fraction distributions were simulated for X-ray tube outputs (and half-value layers, HVL) of 60 kVp (2.3 mm Al), 80 kVp (3.2 mm Al) and 120 kVp (4.3 mm Al) and FoV of 15, 20, 25 and 30 cm. The distributions are obtained for different height levels, corresponding to the lens of the eye, and the lung and prostate, all radiosensitive organs. Investigations are made for eight likely locations around the patient. At fixed FoV results reveal an inverse relationship between ESAK and kVp, also that change in kVp from 60 to 80 has a greater effect than from 80 to 120. For change in FoV at fixed kVp, the scatter fraction remains constant. The particular staff locations are found to be optimal in seeking mitigation of dose. Moreover, the combined usage of numerical human model and Monte Carlo simulation can be considered as an added value to the radiation safety research field, especially to the interventional radiology staff and to the patient.
We estimate the lifetime attributable risk (LAR) of lung cancer incidence in symptomatic Coronary Artery Disease (CAD) patients receiving enhanced Coronary Computed Tomography Angiography (CCTA) and the unenhanced Computed Tomography Calcium Scoring (CTCS) examination. Retrospective analysis has been made of CCTA and CTCS data collected for 87 confirmed CAD adult patients. Patient effective dose (E) and organ doses (ODs) were calculated using CT-EXPO. Statistical correlation and the differences between E and ODs in enhanced CCTA and unenhanced CTCS were calculated using the Pearson coefficient and Wilcoxon unpaired t-test. Following BEIR VII report guidance, organ-specific LARs for the cohort were estimated using the organ-equivalent dose-to-risk conversion factor for numbers of cases per 100,000 patients exposed to low doses of 0.1 Gy. Significant statistical difference (p<0.0001) is found between E obtained for CTCS and that of CCTA. The scan length was found to be greater in CCTA (17.5 ± 2.9 cm) compared to that for CTCS (15 ± 2 cm). More elevated values of dose were noted for the esophagus (4.2 ± 2.15 mSv) and thymus (9.6 ± 2.54 mSv) for both CTCS and CCTA. CTCS organ doses were lower than that of CCTA. Per 100,000 patients, female cumulative doses are seen to give rise to greater lung cancer LARs compared to that for males, albeit with risk varying significantly, noticeably greater for females, younger patients and combined CCTA and CTCS scans. While scan parameters and tube-modulation methods clearly contribute to patient dose, mAs offers by far the greater contribution.
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)
'/%3e%3cuse xlink:href='%23a' transform='translate(0 -400)'/%3e%3cuse xlink:href='%23a' transform='translate(0 -600)'/%3e%3cuse xlink:href='%23a' transform='translate(0 -800)'/%3e%3cuse xlink:href='%23a' transform='translate(0 -1000)'/%3e%3cuse xlink:href='%23a' transform='translate(0 -1200)'/%3e%3cpath d='M0 0h1400v800H0z' style='fill:%23010066'/%3e%3cpath d='M576 100c-166.146 0-301 134.406-301 300s134.854 300 301 300c60.027 0 115.955-17.564 162.927-47.783-27.353 9.44-56.71 14.602-87.271 14.602-147.327 0-266.897-119.172-266.897-266.01 0-146.837 119.57-266.01 266.897-266.01 32.558 0 63.746 5.815 92.602 16.468C696.217 118.91 638.305 100 576 100z' style='fill:%23fc0'/%3e%3cpath d='m914.286 471.429-99.538-53.25 29.43 108.982-66.575-91.165-20.77 110.96-20.428-111.024-66.857 90.96L699.314 418l-99.701 52.943 74.065-85.192-112.8 4.441 103.694-44.62-103.555-44.94L673.8 305.42 600 220l99.538 53.25-29.43-108.982 66.575 91.165 20.77-110.96 20.428 111.023 66.857-90.959L814.97 273.43l99.702-52.944-74.065 85.193 112.8-4.441-103.694 44.62 103.555 44.94-112.785-4.79z' style='fill:%23fc0' transform='matrix(1.2738 0 0 1.2423 -89.443 -29.478)'/%3e%3c/svg%3e)