Exposure Dose Reduction Research Articles

Comparison of Shield of Breast, Thyroid, Eyes for Exposure Dose Reduction in Mammography

Comparison of Shield of Breast, Thyroid, Eyes for Exposure Dose Reduction in Mammography

Radiation-Associated Lymphopenia and Outcomes of Patients with Unresectable Hepatocellular Carcinoma Treated with Radiotherapy

BackgroundThe immune system plays a crucial role in cancer surveillance. Previous studies have shown that lymphopenia associated with radiotherapy (RT) portends a poor prognosis. We sought to differentiate the effects of proton and photon RT on changes in absolute lymphocyte count (ALC) for patients with hepatocellular carcinoma (HCC).Patients and MethodsPatients with HCC treated with definitive RT from 2006 to 2016 were studied. Serial ALCs were graded according to CTCAE v4.0. Overall survival (OS), disease-free survival, and distant metastasis-free survival were analyzed using the Kaplan–Meier method. Univariable and multivariable Cox-proportional hazards analyses were used to identify predictors of OS. A cohort analysis matched for treatment volume was performed to investigate differences in ALC dynamics between photon and proton therapy.ResultsOf 143 patients identified, the median age was 66 (range, 19–90) years. The treatment modality was photon in 103 (72%) and proton in 40 (28%). Median follow-up was 17 months (95% confidence interval, 13–25 months). The median time to ALC nadir after initiation of RT was 17 days with a median relative decrease of 67%. Those who received proton RT had a higher median ALC nadir (0.41 vs 0.32 k/µL, p=0.002) and longer median OS (33 vs 13 months, p=0.002) than those who received photon RT. Matched cohort analyses revealed a larger low-dose liver volume in the photon group, which correlated with lower ALC. On multivariable Cox analysis, Grade 3 or higher lymphopenia prior to or after RT, portal venous tumor thrombus, larger planning target volumes, Child-Pugh (CP) Class B, and increased CP score after RT were associated with a higher risk of death, whereas the use of proton therapy was associated with lower risk.ConclusionGrade 3 or higher lymphopenia may be associated with poorer outcomes in patients receiving RT for HCC. Protons may mitigate lymphopenia compared with photons, potentially due to reduced dose exposure of sites of lymphopoiesis.

Calculation of Lens Exposure Reduction Using Organ-effective Modulation in Pediatric Head CT

Using a pediatric head phantom constructed in our department, we examined a method to reduce exposure by using organ-effective modulation (OEM; Toshiba Medical Systems Corporation, Tochigi) to tilt the gantry during pediatric head computed tomography (CT) scanning. The radiation reduction and CT image standard deviation (SD) were measured at gantry angles at which the orbit was slightly irradiated, partially irradiated, and completely irradiated. The OEM incident surface dose reduction rate was measured using an automatic exposure control (AEC) phantom with a diameter of 6-18 cm. The lens surface dose reduction rate using OEM was 21.2%. When the gantry was tilted and the orbit was completely out of the scanning range, the rate of reduction was 47.8%. OEM incident surface dose reduction rates were 27.4% for a phantom diameter of 18 cm, 22.0% for that of 16 cm, 17.8% for that of 14 cm, 17.2% for that of 12 cm, 8.4% for that of 10 cm, and 0% for that of 8 cm and 6 cm. OEM effectiveness decreased with decreasing phantom diameter. The use of OEM increased the rate of change of SD by 1.25´ when the gantry inclination was 0°, 1.27´ when the gantry inclination was 10°, and 1.27´ when the gantry inclination was 20°in the 12 o'clock position. The degree of reduction in exposure dose to the lens in pediatric head CT imaging was 47.8% by completely removing the lens from the irradiation range using gantry tilt and 21.2% by using OEM. The effect of OEM changed in proportion to tube current. The exposure reduction effect of the OEM decreases with decreasing head size, indicating its reduced effectiveness in head CT scans of smaller infants.

Evaluation of Exposure Dose Reduction in Computed Tomography Colonography

Evaluation of Exposure Dose Reduction in Computed Tomography Colonography

A RADIOLOGIA ODONTOLÓGICA DIGITAL NO ESQUADRÃO DE SAÚDE DE FLORIANÓPOLIS: RELATO DE CASO

O presente artigo relata como foi implementada a Radiologia Digital na Seção de Odontologia do Esquadrão de Saúde de Florianópolis (ES-FL). O objetivo foi a necessidade de modernização dos equipamentos de radiodiagnóstico odontológico existentes, tornando-os digitais. Para tanto, foram analisadas as opções de sistemas digitais existentes e as vantagens dos sistemas CMOS (Complementary Metal Oxide Semiconductor) e PSP (Photostimulable Phosphor Plate), considerando-se, além de seus aspectos técnicos, também os aspectos de biossegurança, de sustentabilidade e jurídicos. Após análise dos dados e comparação dos preços encontrados por intermédio de processo licitatório, optou-se pelo sistema PSP, que apresentava maior vantajosidade. Constatou-se que a implantação da Radiologia Digital no ES-FL trouxe inúmeras vantagens aos pacientes e profissionais da instituição, tais como a diminuição na dose de exposição do paciente, a possibilidade de manipulação das imagens para aprimorar o diagnóstico, a facilidade de comunicação com os pacientes e entre profissionais, além do impacto ambiental positivo, atendimento célere aos pacientes e radioproteção ao usuário, ao profissional e à equipe.

Radiological safety assessment of lead shielded spent resin treatment facility with the treatment capacity of 1 ton/day

The radiological safety of the spent resin treatment facility with a14C treatment capacity of 1 ton/day was evaluated in terms of the external and internal exposure of worker according to operation scenario. In terms of external dose, the annual dose for close work for 1 h/day at a distance of more than 1 m (19.8 mSv) satisfied the annual dose limit. For 8 h of close work per day, the annual dose exceeded the dose limit. For remote work of 2000 h/year, the annual dose was 14.4 mSv. Lead shielding was considered to reduce exposure dose, and the highest annual dose during close work for 1 h/day corresponded to 6.75 mSv. For close work of 2000 h/year and lead thickness exceeding 1.5 cm, the highest value of annual dose was derived as 13.2 mSv. In terms of internal exposure, the initial year dose was estimated to be 1.14E+03 mSv when conservatively 100% of the nuclides were assumed to leak. The allowable outflow rate was derived as 7.77E-02% and 2.00E-01% for the average limit of 20 mSv and the maximum limit of 50 mSv, respectively, where the annual replacement of the worker was required for 50 mSv.

Towards Real Time Radiotherapy Simulation

We propose a novel reconfigurable hardware architecture to implement Monte Carlo based simulation of physical dose accumulation for intensity-modulated adaptive radiotherapy. The long term goal of our effort is to provide accurate dose calculation in real-time during patient treatment. This will allow wider adoption of personalised patient therapies which has the potential to significantly reduce dose exposure to the patient as well as shorten treatment and greatly reduce costs. The proposed architecture exploits the inherent parallelism of Monte Carlo simulations to perform domain decomposition and provide high resolution simulation without being limited by on-chip memory capacity. We present our architecture in detail and provide a performance model to estimate execution time, hardware area and bandwidth utilisation. Finally, we evaluate our architecture on a Xilinx VU9P platform as well as the Xilinx Alveo U250 and show that three VU9P based cards or two Alevo U250s are sufficient to meet our real time target of 100 million randomly generated particle histories per second.

Interim analysis (IA) of OPTIC: A dose-ranging study of three ponatinib (PON) starting doses.

7502 Background: In PACE (NCT01207440) heavily pretreated patients (pts) with chronic-phase CML (CP-CML) had deep, lasting responses to PON; long-term follow-up showed increasing rates of arterial occlusive events (AOEs). We present IA results from OPTIC (NCT02467270), evaluating the association between PON exposure, efficacy, and safety, and response-based dose reduction in pts with CP-CML. Methods: This ongoing, multicenter, randomized phase 2 trial enrolled pts with CP-CML resistant or intolerant to ≥2 TKIs or with a T315I mutation to receive PON at a starting dose of 45 mg (cohort A), 30 mg (B), and 15 mg (C) qd. Doses were reduced to 15 mg qd on achievement of ≤1% BCR-ABL1IS in A/B. Primary endpoint: 12 mo ≤1% BCR-ABL1IS; secondary endpoints include cytogenetic and molecular response and AOE, VTE, and TEAE rates. Results are descriptive at this IA and will be inferential by adjusting multiplicity across 3 cohorts at final analysis. Results: 283 pts were randomized (A/B/C: n = 94/95/94); median age 48 y (18‒81 y). 26% had hypertension history; 2/43/55% received 1/2/≥3 TKIs; 40% had ≥1 baseline (BL) mutations, with 23% T315I. At IA data cutoff (20 Jul 2019), 162 pts (57%; n = 57/51/54) remained on study treatment. Among 282 pts in the safety population, median duration of exposure was ≈1 y (A/B/C, 12.9/11.2/11.0 mo). At 12 mo, 39% (95% CI, 27.6, 50.6), 27% (17.6, 39.1), and 26% (16.5, 38.6) in A, B, and C, respectively, achieved ≤1% BCR-ABL1IS. Additional efficacy in Table. Dose reductions due to efficacy (A/B): 35/21%. Most common TEAEs (any grade/≥3): thrombocytopenia 39/27%, neutropenia 25/17%. AOEs/serious AOEs were reported by (A, B, C) 5%/2%, 4%/3%, and 1%/0%. Dose reductions due to TEAEs: (A/B/C): 44/31/28%; discontinuations due to TEAEs: 18/15/14%. There were 4 (1.4%) on-study deaths; A, sudden death, n = 2; C, pneumonia, n = 2; no deaths were due to AOEs. Clinical trial information: NCT01207440 . Conclusions: OPTIC IA shows a trend toward dose-dependent efficacy and safety and may provide a refined understanding of the PON benefit:risk profile and its relation to dose. Data from longer follow-up may support an alternate dosing regimen for pts with CP-CML. [Table: see text]

Stereotactic Cavity Irradiation or Whole-Brain Radiotherapy Following Brain Metastases Resection-Outcome, Prognostic Factors, and Recurrence Patterns.

Introduction: Following the resection of brain metastases (BM), whole-brain radiotherapy (WBRT) is a long-established standard of care. Its position was recently challenged by the less toxic single-session radiosurgery (SRS) or fractionated stereotactic radiotherapy (FSRT) of the resection cavity, reducing dose exposure of the healthy brain.Patients and Methods: We analyzed 101 patients treated with either SRS/FSRT (n = 50) or WBRT (n = 51) following BM resection over a 5-year period. Propensity score adjustment was done for age, total number of BM, timepoint of BM diagnosis, controlled primary and extracranial metastases. A Cox Proportional Hazards model with univariate and multivariate analysis was fitted for overall survival (OS), local control (LC) and distant brain control (DBC).Results: Median patient age was 61 (interquartile range, IQR: 56–67) years and the most common histology was non-small cell lung cancer, followed by breast cancer. 38% of the patients had additional unresected BM. Twenty-four patients received SRS, 26 patients received FSRT and 51 patients received WBRT. Median OS in the SRS/FSRT subgroup was not reached (IQR NA−16.7 months) vs. 12.6 months (IQR 21.3–4.4) in the WBRT subgroup (hazard ratio, HR 3.3, 95%-CI: [1.5; 7.2] p < 0.002). Twelve-months LC-probability was 94.9% (95%-CI: [88.3; 100.0]) in the SRS subgroup vs. 81.7% (95%-CI: [66.6; 100.0]) in the WBRT subgroup (HR 0.2, 95%-CI: [0.01; 0.9] p = 0.037). Twelve-months DBC-probabilities were 65.0% (95%-CI: [50.8; 83.0]) and 58.8% (95%-CI: [42.9; 80.7]), respectively (HR 1.4, 95%-CI: [0.7; 2.7] p = 0.401). In propensity score-adjusted multivariate analysis, incomplete resection negatively impacted OS (HR 3.9, 95%-CI: [2.0;7.4], p < 0.001) and LC (HR 5.4, 95%-CI: [1.3; 21.9], p = 0.018). Excellent clinical performance (HR 0.4, 95%-CI: [0.2; 0.9], p = 0.030) and better graded prognostic assessment (GPA) score (HR 0.4, 95%-CI: [0.2; 1.0], p = 0.040) were prognostic of superior OS. A higher number of BM was associated with a greater risk of developing new distant BM (HR 5.6, 95%-CI: [1.0; 30.4], p = 0.048). In subgroup analysis, larger cavity volume (HR 1.1, 95%-CI: [1.0; 1.3], p = 0.033) and incomplete resection (HR 12.0, 95%-CI: [1.2; 118.3], p = 0.033) were associated with inferior LC following SRS/FSRT.Conclusion: This is the first propensity score-adjusted direct comparison of SRS/FSRT and WBRT following the resection of BM. Patients receiving SRS/FSRT showed longer OS and LC compared to WBRT. Future analyses will address the optimal choice of safety margin, dose and fractionation for postoperative stereotactic RT of the resection cavity.

The radiological assessment, hazard evaluation, and spatial distribution for a hypothetical nuclear power plant accident at Baiji potential site

BackgroundThe safety assessment in site selection for a new nuclear power plant is an essential issue for human health. It could be improved by predicting the consequences for a hypothetical accident. This paper is contextual with the nuclear safety regarding the risk upon human health from the hazard constituted by the emission of radioactive material due to a hypothetical nuclear power plant accident. HYSPLIT model used and configured based on terrestrial and meteorological conditions for this purpose.ResultsIt presents an analysis of the time-series and spatial distribution for dispersed radioactive contaminants from a hypothetical accident at Baiji potential site. This is based on the geological and meteorological specifications of the potential site. Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model configured to simulate the atmospheric dispersion of fission emissions, then assesses the public health consequences of a hypothetical nuclear accident. Results indicate that the total individual dose intake by the population living around the potential site from the hypothetical accident exceeded 1 Sv, greater than the allowed dose limits by International Commission on Radiological Protection (ICRP). The probability of cancer incidence at regions on directions of southeast to northeast along 30 km from the potential site was high (0.0378 to 0.00131) risk/person. However, the areas that laid on the west and south-west of the site recorded higher levels of influence compared to regions on other directions. Also, the reduction of exposure dose with the distance from the site presented. The north-direction regions from the Baiji site recorded a rapid reduction of exposure dose to become zero at 40 km distance.ConclusionsFinally, to minimize the radiological impacts on population, emergency procedures are required at the regions that laid on the west and south-west of the site. These countermeasure remedy actions should include evacuation, sheltering, ban the sale of local agriculture productions, and long-range resettlement of the population. Since the plume of radioactive contaminants did not arrive at the regions on east and northeast, 40 km away from Baiji site, these areas could be categorized as a support zone.

Development of CT Pelvimetry Using Deep Learning Based Reconstruction

X-ray pelvimetry is typically performed for the diagnosis of the cephalopelvic disproportion (CPD). The purpose of this study was to assess the utility of new computed tomography (CT) reconstruction "deep learning based reconstruction (DLR) " in ultra-low dose CT pelvimetry. CT pelvimetry was performed 320-row CT. All CT images were reconstructed with and without DLR and transferred for workstation to processing martius and guthmann view. Radiologist and obstetrician-gynecologist subjectively ranked overall image quality of each CT image from the best to the worst. Exposure dose of the CT pelvimetry used a following calculated value, displayed CT dose index (CTDI) vol multiplied by measured value using the thimble chamber and pelvic phantom, and of the X-ray pelvimetry used Japan-Diagnositic Refernce Levels 2015 as a reference, were compared. 3D images obtained from CT pelvimetry with DLR showed accurate biparietal diameter and obstetric conjugate as compared to without DLR. Radiation dose of CT pelvimetry is 0.39 mGy, of X-ray pelvimetry is 1.18 mGy, respectively. Conculusion: Although the visualizing high contrast object, such as bone morphology, is likely to reduce exposure dose in CT examination generally, DLR enable to further dose reduction to keep image quality. 3D image processing from CT pelvimetry solves the problem of expansion rate in X-P pelvimetry and provide accurate measurements. Furthermore, CT pelvimetry can undergo more comfortable position for Pregnant Woman in Labor.

Measurement of the Spatial Scattering Dose by Opening, Closing Door and Installing Shielding : A Study on the Reduction of Exposure Dose in Radiography

Measurement of the Spatial Scattering Dose by Opening, Closing Door and Installing Shielding : A Study on the Reduction of Exposure Dose in Radiography

Reduction of Exposure Dose of Mammography by Comparison of Compression Paddle Material

Reduction of Exposure Dose of Mammography by Comparison of Compression Paddle Material

Simple and fast scattering information in X-ray grating-based phase-contrast imaging

X-ray grating-based phase-contrast imaging is a potential imaging method with pre-clinical and clinical applications because it has the possibility of a large field of view and is compatible with X-ray tube sources. However, in X-ray grating-based phase-contrast imaging extraction methods have great importance to retrieve and separate information enabling high acquisition speed, reduced exposure dose and improved mechanical stability. Phase-stepping is a widely used extraction method in X-ray grating-based phase-contrast imaging. However, its discontinuous mode of acquisition leads to worse mechanical stability, exposure dose is generally high, which limits clinical applications significantly. In this work, the integrating bucket method is translated from visible light to X-ray regime, to extract scattering information of the investigated object. Both theoretical derivations with numerical simulation and experiments were performed to confirm the veracity and feasibility of the proposed method. In addition, we present the advantages of the proposed method over the phase-stepping method.

P2434Digital zoom decreases radiation exposure dose up to 30% in percutaneous coronary intervention

Abstract Background Interventional cardiology is gaining greater popularity worldwide with each passing year. Reduction of exposure dose is a very imminent and an important issue in cardiology procedure. Although a newer radiation reduction technique, device and procedure are very valuable and expected, we should consider about therapy technique, radiation technique, devices, and the way to protection. Digital zoom digitally enlarges images in real time by up to 2.5-fold at lower doses than those used with traditional field of view changes. In our phantom examination the average dose reduction of digital zoom was 27%. Methods and results This study is designated as single-center, retrospective, not-randomized, observation study. 2101 eligible cases were collected. We assigned the cases of PCI without the use of Digital zoom to the Conventional group and those involving the use of Digital zoom to the Digital zoom group. There were 806 patients in the Conventional group and 1195 in the Digital zoom group. Because we had begun using Digital zoom from January 2015 onwards, all patients in the Conventional group had undergone PCI from January 2013 to December 2014 and all patients in the Digital zoom group had undergone PCI from January 2015 to December 2016. In addition, we calculated the RAK/minute and DAP/minute for an accurate assessment. To minimize the difference of characteristics between two groups, propensity score including all baseline variables was performed. Furthermore, Predictors of radiation exposure were investigated using multivariable least square methods. Inter group differences were observed in DAP, RAK, DAP/min, and RAK/min (Digital zoom group vs conventional group: DAP, 16000 cGy cm2 [from 1st quartile to 3rd quartile; 10300–24400] vs 20700 [13400–29500], p&lt;0.001; DAP/min, 557 cGy cm2/min [392–737] vs 782 [571–1010], p&lt;0.01; RAK, 1590 Gy [990–2410] vs 1850 [1220–2720], p&lt;0.01; RAK/min, 54.7 Gy/min [38.5–73.2] vs 71.2 [51.5–93.0], p&lt;0.01). Even after propensity score matching, intergroup differences in DAP (810 cases), DAP/min (811 cases), RAK (746 cases), and RAK/min (744 cases) persisted. Furthermore, the least squares method showed that Digital zoom is an important predictor of DAP (β=0.17, p&lt;0.01) and RAK (β=0.12, p&lt;0.01). Conclusion Digital zoom is an old and cost-free technique, but one of most powerful reduction of exposure method. Propensity score adjustment and least square methods show that digital zoom is one of independent effective method.

Surgery Followed by Cornea-Sparing Treatment Approach with Proton Therapy Reduces Orbital Exenteration for Cancer Patients with Periorbital Malignancies

Periorbital malignancies are uncommon and technically challenging to treat given the proximity of several critical structures of the head and neck. Proton therapy offers a dosimetric advantage over photon-based radiation therapy (RT) by reducing dose exposure to tissues beyond the target range. Herein, we present the management, toxicity data, and outcomes after proton therapy for patients with periorbital head and neck cancers. Patients with primary, non-metastatic periorbital cancers treated with proton RT at our institution from 2008 to 2018 were included in this study. Descriptive statistics were used to evaluate patient and tumor characteristics as well as acute and chronic toxicities after proton RT. Two- and 5-year locoregional control (LRC), disease-free survival (DFS), and overall survival (OS) were estimated using the Kaplan-Meier method. Forty-four patients met the inclusion criteria and had a median age of 56 (range, 19-78) years with a median follow up time of 4.5 years. Most patients were white (n=32, 73%), male (n=30, 68%), and had clinical T2 or T3 cancers (n=27, 61%) of the lacrimal sac or gland (n=34, 77%). An orbit-sparing surgical approach was used for 39 patients (89%), and all but 2 patients were treated with surgery followed by (chemo-)radiation. There were 63% grade 1, 30% grade 2, and 6% grade 3 acute toxicities reported, most of which were radiation-induced dermatitis (grade 3: 80% of cases). In patients that had their orbit spared, xerophthalmia was the most common grade 1 ocular toxicity (n=11, 28% of patients) followed by diplopia and epiphora (15% each). Rates of chronic grade 3-4 toxicities were low at 8% (grade 4: 1 corneal ulcer and 1 retinopathy). Two- and 5-year LRC, DFS, and OS were 81% and 81%, 73% and 61%, and 77% and 63%, respectively. Multimodal therapy that includes proton radiation therapy results in excellent locoregional control and survival with preservation of vision and cosmesis for patients with periorbital malignancies.

A Study on the Usefulness of Breast Shielding Apron for Reducing Exposure Dose in Mammography

A Study on the Usefulness of Breast Shielding Apron for Reducing Exposure Dose in Mammography

Pre-Operative Versus Post-Operative Radiosurgery of Brain Metastases-Volumetric and Dosimetric Impact of Treatment Sequence and Margin Concept.

Background: Pre-operative radiosurgery (SRS) preceding the resection of brain metastases promises to circumvent limitations of post-operative cavity SRS. It minimizes uncertainties regarding delineation and safety margins and could reduce dose exposure of the healthy brain (HB). Methods: We performed a systematic treatment plan comparison on 24 patients who received post-operative radiosurgery of the resection cavity at our institution. Comparative treatment plans were calculated for hypofractionated stereotactic radiotherapy (7 × 5 Gray (Gy)) in a hypothetical pre-operative (pre-op) and two post-operative scenarios, either with (extended field, post-op-E) or without the surgical tract (involved field, post-op-I). Detailed volumetric comparison of the resulting target volumes was performed, as well as dosimetric comparison focusing on targets and the HB. Results: The resection cavity was significantly smaller and different in morphology from the pre-operative lesion, yielding a low Dice Similarity Coefficient (DSC) of 53% (p = 0.019). Post-op-I and post-op-E targets showed high similarity (DSC = 93%), and including the surgical tract moderately enlarged resulting median target size (18.58 ccm vs. 22.89 ccm, p < 0.001). Dosimetric analysis favored the pre-operative treatment setting since it significantly decreased relevant dose exposure of the HB (Median volume receiving 28 Gy: 6.79 vs. 10.79 for pre-op vs. post-op-E, p < 0.001). Dosimetrically, pre-operative SRS is a promising alternative to post-operative cavity irradiation that could furthermore offer practical benefits regarding delineation and treatment planning. Comparative trials are required to evaluate potential clinical advantages of this approach.

Evolving Radiotherapy Techniques in Paediatric Oncology

AimsChildhood cancer is rare and survival of childhood cancer has increased up to 80% at 5 years after diagnosis. Radiotherapy is an important element of the multimodal treatment concept. However, due to growing tissue, children are particularly sensitive to radiation-related side-effects and the induction of secondary malignancies. However, radiotherapy techniques have continuously progressed. In addition, modern treatment concepts have been improved in order to minimise long-term effects. Today, radiotherapy is used for various tumour types in childhood, such as sarcomas and tumours of the central nervous system. Materials and methodsExternal beam therapy with either photons or protons and brachytherapy are predominantly used for the treatment of childhood tumours. Technical developments and features, as well as clinical outcomes, for several tumour entities are presented. ResultsThe development of radiotherapy techniques, as well as risk-adapted therapy concepts, resulted in promising outcome regarding tumour control, survival and therapy-related side-effects. It is assumed that proton therapy will be increasingly used for treating children in the future. However, more data have to be collected through multi-institutional registries in order to strengthen the evidence. ConclusionThe development of radiotherapy techniques is beneficial for children in terms of reducing dose exposure. As compared with other modern and highly conformal techniques, particularly proton therapy may achieve high survival rates and tumour control rates while decreasing the risk for side-effects. However, clinical evidence for modern radiotherapy techniques is still limited today. An optimal patient triaging with the selection of the most appropriate radiation technique for each individual patient will be an important goal for the future.

A Study on Reduction of Exposure Dose According to Use of Cone in Radiologic Examination of Paranasal Sinus

It aimed to seek the measures to decrease the exposure dose of radiation for the patients as well as the guardians during the paranasal radiography upon the survey on the usage of cone, which is the radiation shielding material in the paranasal radiography in the medical institutions, to measure the exposure dose to the patients depending on the usage of cone. The cone, diagnostic radiator, Ion Chamber, and Skull Phantom were used. The mean value was obtained measuring the points of 5° intervals of 0°, 45°, 90°, 135°, 180°, 225°, and 315° at 15cm from the center of the phantom five times each. In addition, the space dose was measured up to 200cm while increasing the distance with a radius of 50 cm from the center of the phantom. The spatial scattering dose distribution was measured five times at 50cm, 100cm, 150cm, and 200cm intervals in the directions of 0°, 45°, 135°, and 180° based on the phantom.60% of medical institutions did not have the radiation shielding device of a cone and74.4% did not use the cone in paranasal sinus examination. In the comparison of doses between the use and non-use of a cone, the dose decreased by 50.8% at 0°, 47.3% at 45°, 35.7%at 90°,59.2% at 135°, 39.8% at 180°, 27.3% at 225°, and 46.4% at 315° when the cone was used. The spatial dosimetry according to the distance was highest at 11.56mR/h at 0°, 1.08mR/h at 45°, 1.59mR/h at135°, and 0.94mR/h at 180°. In addition, spatial scattering rays were reduced to 92.7% when thecone was used as compared to when no cone was used. Therefore, a cone should be used in the radiologic examinatio of paranasal sinuses, and radiation workers and the family protector should also ensure that they are a safe distance away in order to prevent exposure by secondary radiation.