Effects of bolus thickness and use frequency on skin dose in postmastectomy intensity-modulated radiotherapy / 中国辐射卫生

Objective To investigate the effects of bolus thickness and use frequency on skin dose in postmastectomy intensity-modulated radiotherapy. Methods We retrospectively reviewed 20 cases receiving postmastectomy fixed-field intensity-modulated radiotherapy, to analyze the homogeneity index (HI) and conformity index (CI) of the target volume and the skin dose (Dmax, Dmean, and Dmin) of radiotherapy plans with 0.5 cm-thick bolus or 1 cm-thick bolus alone at a use frequency of 5 F, 10 F, 15 F, 20 F, and 25 F versus a combination of 0.5 cm and 1 cm-thick bolus, and fit the relationship between skin dose and bolus use frequency. Results As the bolus use frequency increased, the skin dose increased, the hot spot of the target volume decreased, and the low-dose volume decreased. The HI of the target volume with the 1 cm bolus was better than that with the 0.5 cm bolus at all use frequencies (P < 0.05), and HI decreased with the increase of bolus use frequency. For both 0.5 cm and 1 cm bolus, the CI of the target volume increased initially and then decreased, reaching the maximum value at a frequency of around 15 F; the CI showed significant differences only at 20 F and 25 F between the two types of bolus (P < 0.05). The skin Dmax and Dmean were significant higher with the 0.5 cm bolus than with the 1 cm bolus (P < 0.05). The equation for the relationship between skin dose (D) and bolus use frequency (F) was D = A × F + B × F2 + C. The Dmax and HI with the combination of 0.5 cm bolus (6 F) plus 1 cm bolus (8 F) fell between those with the 0.5 cm bolus (15 F) and those with the 1 cm bolus (15 F) (P < 0.05). Conclusion In postmastectomy fixed-field intensity-modulated radiotherapy, skin dose can be calculated based on bolus use frequency. Mixed use of bolus may be more suitable than use of 0.5 cm bolus or 1 cm bolus alone.

Radiation dosimetric study of patients and professionals in an intervention procedure based on PBU-60 anthropomorphic phantom / 中国辐射卫生

Objective Based on the anthropomorphic phantom experiment and Monte Carlo simulation, the patients’ skin dose, professionals’ dose, and spatial distribution of DSA (Digital Subtraction Angiography) radiation field in an intervention procedure, was performed, in order to provide the basis for the inference of patients’ skin injury and professionals’ radiation protection in intervention procedure. Methods In the simulation experiment, a PBU-60 anthropomorphic phantom was used as the patient and the skin dose of patient’s abdomen was measured by TLD (Thermoluminescence Dosimeters). X-ray and gamma radiation dosimeter (AT1121) was applied to measure the spatial distribution of DSA radiation field, which was verified using Monte Carlo software MCNP meanwhile. Furthermore, the radiation dosimetry of operative staffs at different stations and under different protection conditions was studied experimentally. Results The experimental measurements showed that the maximum skin dose of patients every 5-minute fluoroscopy was 18.62 mGy under the irradiation of PA in an abdominal interventional procedure. The results of Monte Carlo simulation and measurement experiments showed that the spatial distribution of DSA radiation fieldis similar to the butterfly distribution, which is related to distance and angle. The experimental results showed that the dose rate decreases exponentially with the increase of lead equivalent. Conclusion It is very significant to carry out skin dose measurementof patients during interventional surgery and follow-up patients with high dose after surgery. In interventional surgery, doctors should try to avoid the station of high dose rate. However, it is necessary to strengthen the radiation protection of the operator and the first assistant. Under the dual protections of bedside lead protective equipment and personal protective equipment, the exposure dose of intervention personnel can be significantly reduced.

Peak skin dose measurements for patients in neuro-interventional procedures using radiochromic film / 中华放射医学与防护杂志

Objective:To determine the peak skin dose (PSD) to patients from neuro-interventional procedures and evaluate the risk of the deterministic effect.Methods:Gafchromic XR RV3 films were used in a level A tertiary hospital in Beijing to measure the patients′ PSD from neuro-interventional procedures, mainly three common types of procedures, including vascular embolization, vascular angioplasty and vascular angiography. The films were scanned by Epson Expression 10000XL, read by ImageJ software, and analyzed by Film QA Pro?2014 software.Results:PSD was measured in 23 embolizations, 14 stentings and 12 arteriography. There were 20 patients whose PSD were equal or greater than 2 Gy, including 15 in vascular embolization and 5 in angioplasty. The PSDs to patients in cerebral arteriography were all below 2 Gy. The PSDs to some of the patients were higher than the threshold for deterministic effect recommended by ICRP Publication 118.Conclusions:There is a risk of deterministic effect in neurointerventional procedures. It is suggested that the patients be followed up to observe their radiation injury as well as to know in time the subsequent diagnosis and treatment.

Neck skin dose planning for early-stage nasopharyngeal carcinoma: a comparative study of three radiotherapy methods / 中华放射肿瘤学杂志

Objective To compare the neck skin dose between fixed-field dynamic intensity-modulated radiation therapy (dlMRT),volumetric modulated arc therapy (VMAT),and helical tomotherapy (HT) in the treatment of early-stage nasopharyngeal carcinoma.Methods A total of 16 early-stage nasopharyngeal carcinoma patients undergoing radiotherapy were enrolled as subjects.The neck skin was delineated by contraction of the outer edge of neck by 3 mm.Dose planning was made by the traditional method (TP group)and a new method (NP group),in which the neck skin was considered as the organ at risk.Dmean and V5-V70 for the neck skin were recorded.The paired t-test was used to analyze the differences between two plans in each radiotherapy method.An analysis of variance was used to compare the same plan between the three radiotherapy methods.Results The HT group had significantly higher Dmean and V5-V70 for the neck skin than the dIMRT group and the VMAT group (P=0.00,0.00,0.00,0.00,0.00,0.00,0.00,0.02).Using dIMRT,the D and V10-V60 for the neck skin were reduced by 7％,8％,22％,25％,38％,59％,and 85％ in the NP group than in the TP group (P=0.00,0.00,0.00,0.00,0.00,0.00,0.00).Using VMAT,the D and V20-V40 for the neck skin were reduced by 4％,19％,29％,and 34％ in the NP group than in the TP group (P=0.02,0.01,0.02,0.01).Using HT,the V30-V60 for the neck skin were reduced by 20％,29％,50％,and 67％ in the NP group than in the TP group (P=0.00,0.00,0.00,0.00,0.03).Conclusions In the treatment of early-stage nasopharyngeal carcinoma,HT causes a higher radiation dose to the neck skin than dIMRT and VMAT,while dIMRT and VMAT have similar neck skin doses.The neck skin dose can be significantly reduced with the neck skin as the organ at risk.

A dosimetric study of neck skin dose for early-stage nasopharyngeal carcinoma treated by Tomotherapy / 中华放射医学与防护杂志

Objective The purpose of this study is to investigate the method to reduce the radiation dose to the neck skin in the Tomotherapy treatment plans for early-stage nasopharyngeal carcinoma.Methods The 17 patients with early-stage nasopharyngeal carcinoma that have been treated by the Tomotherapy were selected randomly for this skin sparing study.The neck skin sparing region was generated as an internal margin of 3 mm from the out body contour,excluding the intercrossed area with the targets.Candidate patients were planned using TP and NP method respectively:the TP group was planned with the traditional method.The new neck skin region was considered as an organ at risk (OAR) for planning dose constrain in NP group.The dosimetric metrics of targets and OARs,monitor units (MU) and delivery time were compared as the end points of these two groups.Results The two treatment plan groups satisfied the clinical requirement.There were no significant differences for D98,D95 and D2 of the targets (P ＞ 0.05).The Dmax of brainstem,D1cc of spinal cord,D of right parotid were higher in NP group than in theTPgroup (t =2.47,2.34,2.77,P＜0.05).The Dmax of left mandible joint was lower than TP group(t =2.30,P ＜ 0.05).The V30,V40,V50 and V60 of the skin were considerably lower than TP group (t =8.37,6.02,5.82,4.89,P ＜ 0.05).The mean MU and mean delivery time per fraction of NP group were 6.3％ and 8.1％ less than that of TP group respectively.Conclusions The neck skin region should be delineated as an OAR to be spared in the Tomotherapy treatment planning for early-stage nasopharyngeal carcinoma.This method can reduce the skin radiation dose effectively,alleviate the skin reaction,and improve the life quality of patients in radiotherapy.

Patient Dose Assessment for Common Digital Diagnostic Radiology Examination in Hamad Medical Corporation Hospitals in the State of Qatar.

The aim of this study was to estimate radiation doses to patients undergoing standard radiographic examinations using Computed Radiography (CR) and Direct Digital Radiography (DDR) in two hospitals within Hamad Medical Corporation (HMC) in Qatar, and compare the results with regional and international Diagnostic Reference Levels (DRLs). Data on 3391 patients were recorded from different X-ray rooms in HMC hospitals. Entrance Skin Dose (ESD) was measured for 1046 patients for the most five common X-ray examinations (a total of 7 projections) namely: Skull, Chest, Abdomen, Lumbar Spine and Pelvis. Exposure factors such as kV, mAs and Focal to Skin Distance (FSD) were recorded for each patient. Tube Output was measured for a range of selected kV values. ESD for each individual patient was calculated using the tube output and the technical exposure factors for each examination. The ESD values were compared with some international DRLs for all types of examinations. HMC patient demographic data evaluated from this study were: average age of 39 years, average weight of 60-80 kg and mean height of 165 cm. The most procedure performed during the time of this study was chest PA (52%), and the least procedure performed was skull AP/LAT (1%) examination. The mean ESD values found to be generally lower than the published values. With exception of abdomen examinations at Hamad General Hospital (HGH), mean ESD values were found to be within the established IAEA (DRL). The mean ESD values at HGH were found to be much higher than that at Al Khor Hospital (AKH) for abdomen, Lumbar spine AP, Lumbar Spine LAT and pelvis, but generally lower than the published values.

Peak skin dose measurements in two cardiac interventional procedures using radiochromic film / 中华放射医学与防护杂志

Objective To measure the peak skin dose (PSD) in two cardiovascular interventional procedures,including coronary angiography (CA) and percutaneous transluminal coronary angioplasty (PTCA) using radiochromic film.Methods Gafchromic XR-RV3 film was selected to measure PSD in two hospitals.The films were placed on the table underneath the patient during interventional surgery.The kV,mA,fluoroscopy time,dose-area product (DAP),and cumulative dose at reference point and other relevant information were recorded for all cases.Using the Epson V750 flatbed scanner for scanning and analyzing film,FilmQA software was chosen to analyze the pixel value of red,green and blue color channels.The PSD was determined using red channel data.The correlation and linear regression analysis between PSD and device-displayed parameters was carried out.Results PSD were measured using XR-RV3 film for 26 CA and 19 CA + PTCA procedures.For CA procedures,maximum fluoroscopy time,cumulative dose and DAP were 17.62 min,1 498.50 mGy and 109.68 Gy · cm2,respectively.The maximum PSD was 361.20 mGy.However,for CA + PTCA procedures,maximum fluoroscopy time,cumulative dose and DAP were 64.48 min,6 976.20 mGy and 5 336.00 Gy· cm2,respectively.One patient with CA + PTCA procedures was found to have received the PSD value more than 2 Gy,up to 2 195.70 mGy.DAP was found to be a good indicator (R2 =0.815,P ＜0.05) of PSD for CA procedure,and correlated with cumulative dose (R2 =0.916,P ＜ 0.05) for CA + PTCA procedures.Conclusions The PSD value of some patients in cardiac interventional procedures would exceed 2 Gy,the threshold of deterministic effects recommended by ICRP.The dose-related parameters value showed on DSA device can only used to estimate PSD roughly.Using XR-RV3 film accurate measurement of the PSD in interventional projects is a very fast and effective method.

Comparison of dosimetric characteristics of two radiochromic films (XR-RV3 and EDR2) / 中华放射医学与防护杂志

Objective To study the dosimetric characteristics of two different radiochromic films used to estimate peak skin dose(PSD) of patients.The characteristics of these two films were investigated and compared after exposure to ionizing radiation in the diagnostic energy range,including post-exposure gray growth,sensitivity,energy dependence and dose response.Methods GafChromic XR-RV3 film and KODAK EDR2 film were exposed to air kerma 800 mGy free-in-air using five X-ray beam qualities (60,80,100,120 and 140 kVp) in a SSDL.The measurement for each energy was normalized to 80 kV to analyze energy dependence of films.The films were calibrated to different dose level (0.025-10 Gy) onphantom by 80 kV X-rays.The response curve were plotted to analyze sensitivity and dose response.The films were scanned with Epson V750 commercial flatbed scanner.Color channel analysis was performed.Results The post-exposure gray growth of XR-RV3 film was found to be fairly stable.The change were 2％,4％,6％ at 24 h,72 h and 6 weeks after exposure respectively.EDR2 film was found to be more sensitivity than XR-RV3 film in low dose.The energy response of the XR-RV3 film and EDR2 film were within 9％ and 23％ over the clinical diagnostic x-ray energies,respectively.In the dose range of 0.025-10 Gy,for the XR-RV3 film,the red channel with the dose response curve was most obvious.For EDR2 film,the pixel value of three color channels was coincident.The EDR2 film appeared to be saturated when receiving doses greater than 500 mGy.Conclusions The XR-RV3 film is superior to EDR2 film in gray growth,energy dependence,dose-response and other aspects.This film is very suitable for measuring and analyzing PSD of patients in interventional radiology procedures.

Entrance Surface Dose from Pediatric Diagnostic X-ray Examinations in a Developing World Setting: Are We ‘ALARA Principle Compliant.

Background: Radiation protection in paediatric radiology requires special attention than in adult because children are more sensitive to radiation and at higher risk. This risk is explained by the longer life expectancy in children which allows for harmful effects of radiation to manifest and their developing organs and tissues being more sensitive to radiation. Hence, the need for determination of appropriate radiation dose for paediatric patients. Aims: To estimate entrance skin dose (ESD) received by paediatric patients during diagnostic x-ray examinations. Materials and Methods: A total of 253 paediatric patients undergoing various x-ray examinations between June 2011 and December, 2012 in a teaching hospital in the South West Nigeria were considered in this study. This hospital has no dedicated x-ray unit for paediatric radiology. The ESD received during x-ray examination was calculated using mathematical formula that incorporated the use of x-ray beam output and exposure parameters selected for the examination. Correlation coefficient (r) analysis was used to test the relationship between ESD, patient size (age and weight) and exposure parameters (kVp, mAs). Results: The ESD and ED received by paediatric patients from all the x-ray examinations considered in this study ranged from 10.29 ± 3.80 - 880.04 ± 89.44 μGy and 1.44 ± 0.53 - 66.74 ± 30.84 μSv respectively. The correlation coefficient analysis at 0.01 level of significant showed that there is a correlation between patient dose and exposure factors but there is no correlation between ESD, age and weight of patients. Conclusion: The ESD received by paediatric patients is higher than the internationally recommended reference dose. This is attributed to lack of dedicated x-ray unit and personnel for paediatric radiology.

Influência da dependência energética de dosímetros termoluminescentes na medida da dose na entrada da pele em procedimentos radiográficos / Influence of thermoluminescent dosimeters energy dependence on the measurement of entrance skin dose in radiographic procedures

OBJETIVO: O objetivo do presente trabalho foi avaliar a influência da dependência energética de materiais termoluminescentes na determinação da dose na entrada da pele de pacientes submetidos a exames radiográficos (radiologia geral, mamografia e radiologia odontológica). MATERIAIS E MÉTODOS: Três diferentes materiais termoluminescentes foram utilizados: LiF:Mg,Ti, LiF:Mg,Cu,P e CaSO4:Dy. Estes materiais foram expostos a fontes padronizadas de radiação X e gama, e a feixes clínicos de raios X. RESULTADOS: As curvas de calibração e de dependência energética foram obtidas. Todos os materiais apresentaram resposta linear em função do kerma no ar. Com relação à dependência energética, as amostras de CaSO4:Dy e LiF:Mg,Ti mostraram maior variação da resposta termoluminescente em função da energia efetiva do feixe de radiação. CONCLUSÃO: Os materiais testados mostraram desempenho adequado para a detecção da radiação X em feixes padronizados e clínicos. Embora as amostras de CaSO4:Dy e LiF:Mg,Ti apresentem dependência energética significativa no intervalo de energia considerado, este materiais podem ser utilizados para medição da dose de entrada na pele se fatores de correção apropriados forem utilizados.

OBJECTIVE: This study was aimed at evaluating the influence of the energy dependence of thermoluminescent materials on the determination of entrance skin dose in patients submitted to conventional radiographic studies (general radiology, mammography and dental radiology). MATERIALS AND METHODS: Three different thermoluminescent materials were utilized: LiF:Mg,Ti, LiF:Mg,Cu,P and CaSO4:Dy. These materials were exposed to standardized sources of X and gamma radiation and clinical X-ray beams. RESULTS: Calibration and energy dependence curves were obtained. All the materials showed a linear response as a function of the air kerma. As far as energy dependence is concerned, the CaSO4:Dy and LiF:Mg,Ti samples showed the greatest variation on thermoluminescent responses as a function of the effective radiation beam. CONCLUSION: The tested materials showed an appropriate performance for detecting X radiation on standard and clinical X-ray beams. Although CaSO4:Dy and LiF:Mg,Ti samples present a significant energy dependence in the considered energy range, these materials can be utilized for measuring entrance skin doses, provided appropriate correction factors are applied.

Verification of Skin Dose in Tomotherapy Using the Developed Phantom for Image Based Radiation Treatment System / 의학물리

Radiation treatment for skin cancer has recently increased in tomotherapy. It was reported that required dose could be delivered with homogeneous dose distribution to the target without field matching using electron and photon beam. Therapeutic beam of tomotherapy, however, has several different physical characteristic and irradiation of helical beam is involved in the mechanically dynamic factors. Thus verification of skin dose is requisite using independent tools with additional verification method. Modified phantom for dose measurement was developed and skin dose verification was performed using inserted thermoluminescent dosimeters (TLDs) and GafChromic EBT films. As the homogeneous dose was delivered to the region including surface and 6 mm depth, measured dose using films showed about average 2% lower dose than calculated one in treatment planning system. Region indicating about 14% higher and lower absorbed dose was verified on measured dose distribution. Uniformity of dose distribution on films decreased as compared with that of calculated results. Dose variation affected by inhomogeneous material, Teflon, little showed. In regard to the measured dose and its distribution in tomotherapy, verification of skin dose through measurement is required before the radiation treatment for the target located at the curved surface or superficial depth.

Superficial Dosimetry for Helical Tomotherapy / 대한방사선종양학회지

PURPOSE: To investigate the feasibility of helical tomotherapy on a wide curved area of the skin, and its accuracy in calculating the absorbed dose in the superficial region. MATERIALS AND METHODS: Two types of treatment plans were made with the cylinder-shaped 'cheese phantom'. In the first trial, 2 Gy was prescribed to a 1-cm depth from the surface. For the other trial, 2 Gy was prescribed to a 1-cm depth from the external side of the surface by 5 mm. The inner part of the phantom was completely blocked. To measure the surface dose and the depth dose profile, an EDR2 film was inserted into the phantom, while 6 TLD chips were attached to the surface. RESULTS: The film indicated that the surface dose of the former case was 118.7 cGy and the latter case was 130.9 cGy. The TLD chips indicated that the surface dose was higher than these, but it was due to the finite thickness of the TLD chips. In the former case, 95% of the prescribed dose was obtained at a 2.1 mm depth, while the prescribed does was at 2.2 mm in the latter case. The maximum dose was about 110% of the prescribed dose. As the depth became deeper, the dose decreased rapidly. Accordingly, at a 2-cm depth, the dose was 20% of the prescribed dose. CONCLUSION: Helical tomotherapy could be a useful application in the treatment of a wide area of the skin with curvature. However, for depths up to 2 mm, the planning system overestimated the superficial dose. For shallower targets, the use of a compensator such as a bolus is required.

Radiation Exposure to Premature Infants in a Neonatal Intensive Care Unit in Turkey

OBJECTIVE: The aim of this work was to determine the radiation dose received by infants from radiographic exposure and the contribution from scatter radiation due to radiographic exposure of other infants in the same room. MATERIALS AND METHODS: We retrospectively evaluated the entrance skin doses (ESDs) and effective doses of 23 infants with a gestational age as low as 28 weeks. ESDs were determined from tube output measurements (ESD(TO)) (n = 23) and from the use of thermoluminescent dosimetry (ESD(TLD)) (n = 16). Scattered radiation was evaluated using a 5 cm Perspex phantom. Effective doses were estimated from ESD(TO) by Monte Carlo computed software and radiation risks were estimated from the effective dose. ESD(TO) and ESD(TLD) were correlated using linear regression analysis. RESULTS: The mean ESD(TO) for the chest and abdomen were 67 micro Gy and 65 micro Gy per procedure, respectively. The mean ESD(TLD) per radiograph was 70 micro Gy. The measured scattered radiation range at a 2 m distance from the neonatal intensive care unit (NICU) was (11-17 micro Gy[corrected to 11-17 nGy]) per radiograph. Mean effective doses were 16 and 27 micro Sv per procedure for the chest and abdomen, respectively. ESD(TLD) was well correlated with ESD(TO) obtained from the total chest and abdomen radiographs for each infant (R2 = 0.86). The radiation risks for childhood cancer estimated from the effective dose were 0.4 x 10(-6) to 2 x 10(-6) and 0.6 x 10(-6) to 2.9 x 10(-6) for chest and abdomen radiographs, respectively. CONCLUSION: The results of our study show that neonates received acceptable doses from common radiological examinations. Although the contribution of scatter radiation to the neonatal dose is low, considering the sensitivity of the neonates to radiation, further protective action was performed by increasing the distance of the infants from each other.

Comparison of Skin dose Measurement Using Glass Dosimeter and Diode for Breast Cancer Patients / 의학물리

The purpose of this study was to measure the skin dose using the glass dosimeter and diode and to compare those measurements to the planned skin dose from the treatment planning system. For the reproducibility of the glass dosimeter (ASAHI TECHNO GLASS CIRPORATION, Japan), the same dose was irradiated to 40 glass dosimeters three times, among which 28 with the reproducibility within 3% were selected for the use of this study. For each of 27 breast cancer patients, the glass dosimeters and diodes were attached to 4 different locations on the skin to measure the dose during treatment. All the patients received one fraction of 180 cGy each. The maximum difference of measurements between the glass dosimeter and diode at the same location was 3.2%. Comparing with the planned skin dose from the treatment planning system (Eclipse v6.5, Varian, USA), the dose measured by the glass dosimeter and the diodeshowed on an average 3.4% and 2.3% difference, respectively. The measured doses were always less than the planned skin dose. This may be due to the specific errors of both detectors. Also, the difference may be caused by the fact that since the skin where the detectors were attached is pretty moveable, it was not fix the detectors on the skin.

Evaluation of Skin Dose of Intensity Modulated Radiation Therapy in Breast Cancer Patients / 의학물리

In the case of radiotherapy following breast conservation therapy for breast cancer patients, the characteristic of skin dose was investigated in the treatment of intensity modulated radiation therapy (IMRT) for breast cancer patients by comparing and analysing entrance skin dose irradiated during radiotherapy using tangential technique radiotherpy, and IMRT. The calculation dose irradiated to breast skin was compared with TLD measurement dose in treatment planning by performing the two methods of radiotherapy using tangential technique, and IMRT in treatment planning equipment. The skin absorbed dose was measured to pass a nipple by spacing of 1 cm distance from center to edge of body. In the radiotherapy of tangential technique, for the irradiation of 180 cGy to PTV, the calculation dose was ranged from 103.6 cGy to 155.2 cGy, measurement dose was ranged from 107.5 cGy to 156.2 cGy, and skin dose in the center was maximum 1.45 times more irradiated than that in the edge. In the IMRT, for the irradiation of 180 cGy to PTV, the calculation dose was ranged 9.8 cGy at 80.2 cGy, measurement dose was ranged 8.9 cGy at 77.2 cGy, and skin dose in the center was maximum 0.23 times less irradiated than that in the edge. IMRT was more effective for skin radiation risks because radiation dose irradiated to skin in IMRT was much less than that in radiotherapy of tangential field technique.

Skin Dose Distrubution with Spoiler of 6 MV X-ray for head and Neck Tumor / 대한치료방사선과학회지

PURPOSE: This study was performed for adequate irradating tumor area when 6 MV linear accerelator photon was used to treat the head and neck tumor. The skin surface dose and maximum build-up ragion was measured by using a spoiler which was located between skin surface and collimator. METHODS: A spoiler was made of tissue equivalent materials and the skin surface dose and maximum build-up region was measured varing with field size, thickness of spoiler and interval between skin and collimator. The results of skin surface dose and maximum build-up dose was represented as a build-up ratio and it was compared with dose distribution by using a bolus. RESULTS: The skin surface dose was increased with appling spoiler and decreased by distance of the skin-spoiler separation. The maxium build-up region was 1.5 cm below the skin surface and it was markedly decreased near the skin surface. By using a 1.0-cm thickness spoiler, Dmax moved to 5, 10.2, 12.3, 13.9 and 14.8 mm from the skin surface by separation of the spoiler from the skin 0, 5, 10, 15, 20 cm, respectively. CONCLUSION: The skin surface dose was increased and maximum build-up region was moved to the surface by using a spoiler. Therefore spoiler was useful in treating by high energy photon in the head and neck tumor.

Survey on patient dose in cardiac intervention / 介入放射学杂志

Objective To collect information of patient doses of interventional radiology in Beijing Xuanwu Hospital,and investigate correlation between the peak skin dose(PSD) and dose-area product(DAP).Methods Radiation doses from 135 patients have been studied including 84 coronary angiographies(CAG) and 51 percutaneous transluminal coronary angioplasties(PCI).Dose-area product(DAP) values,cumulative dose(CD) at interventional reference points,fluoroscopy times,total number of cine frames were collected for each patient.Skin dose measurements were made with thermoluminescent dosimeters(TLD) placed as a 10 ? 9 arrays of TLDs on the body.The grid of TLDs arrays was 5 ? 4 cm.Results Mean values for dose-area product were 2690.84 ?Gym2 for CAG and 7946.91 ?Gym2 for PCI.Mean values for CD were 431.6 mGy cm2 for CAG and 1395.3 mGy for PCI.Mean fluoroscopy times were 2.9 min for CAG and 10.9 min for PCI and mean number of frames were 544 and 945 for CAG and PCI,respectively.PSD values ranged from 26.18 to 120.37 mGy for CAG and 38.91 to 184.79 mGy for PCI.The relationship between DAP and PSD was r = 0.52 for CAG and r = 0.54 for PCI.The correlation of PSD with CD was r = 0.45 for CAG and r = 0.53 for PCI.Conclusion Comparison shows that patients DAP,CD and fluoroscopy time values were comparable with other publications.Skin dose values of investigated patients are below the threshold dose for radiation skin injury(2 Gy).There is no good relationship between DAP and PSD.So calculation of individual maximum skin dose based on DAP data is not reliable and needs to find a new reference value for skin dose.(J Intervent Radiol,2007,16:222-225)

The Enhancement of Skin Sparing by Tray Materials for High Energy Photon Beam / 대한치료방사선과학회지

The skin sparing effect associated with high energy x-ray or gamma ray beams may be reduce or lost under certain conditions of treatment. Current trends in using large fields. Shield carrying trays, compensating filters, and isocentric methods of treatment have posed problems of increased skin dose which sometimes become a limiting factor in giving adquate tumor doses. We used the shallow ion chamber to measure the phantom surface dose and the physical treatment variables for Co-60 gamma ray, 4MV and 10 MV x-ray beam. The dependence of percent surface dose on field sizes, atomic number of the shielding tray materials and its distance from the surface for 4, 10MV x-rays and Co-60 gamma ray is qualitatively similar. The use of 2 mm thick tin filter is recommended for situations where a low atomic number tray is introduced into the beam at distances less than 15 cm from the surface and with the large field sized for 4 MV x-ray beam. In case of Co-50 gamma ray, the lead glass tray is suitable for enhancement of skin sparing. Also, the filter distance should be as large as possible to achieve substantial skin sparing.

Dose Effect of Tissue Compensator for 6 MV X-Ray / 대한치료방사선과학회지

It is ideal thing to compensate tissue deficit without skin contamination in curvatured irradiation field of high energy Photon beam. The 3-dimensional compensating technique utilizing tissue equivalent materials to ensure an adequate dose distribution and skin sparing effect was described. This compensator was made of paraffin(70%) and stearin wax (30%) compound. The parameters for evaluation of the effect on skin dose in application of compensator were considered in the size of the field, the thickness of the compensator and the source-to-axis distance. The results are as follows; the skin doses were not changed even though application of the compensator, but depended on the field size and the source-to-axis distance, and the skin doses were only slightly changed within 1% relative errors as increasing the thickness of the compensator in these experiments.