Measurement of environmental radiation in X-ray room with passive integrating dosimeter

Radiation dose limits in the controlled area of an X-ray room have been prescribed at 1.3 mSv/3 months by the Enforcement Regulations of the Medical Service Law. Leakage effective dose must be measured once within a period that does not exceed six months. Scattered radiation and leakage effective dose were measured in 4 X-ray rooms (chest X-ray room, general-purpose X-ray room, skull and neck X-ray room, and X-ray CT room) with the optically stimulated luminescence dosimeter (OSLD), which is a passive integrating dosimeter. The availability of the measurement method for radiation control with OSLD was evaluated. Scattered radiation in the inside wall surface of the skull and neck X-ray room was less than 1.3 mSv/3 months of the dose limits. There was more scattered radiation in the X-ray CT room than in other X-ray rooms, and the maximum dose was 428 mSv/3 months, measured on the floor. All measurements of leakage effective dose in the 4 X-ray rooms were less than the radiation dose limit, and most measurements of leakage effective dose were less than the detection limits of the dosimeter. Leakage effective dose as calculated by Law 188 (Law 188-Dose) was less than the radiation dose limits in three X-ray rooms, the exception being the X-ray CT room. The Law 188-Dose of the X-ray CT room exceeded 1.3 mSv/3 months at the walls where primary X-rays were directed. The measurement method of leakage effective dose with an ionization survey meter was not able to guarantee the workload of each X-ray apparatus. Therefore, we were not able to confirm the security of X-ray rooms by measurement with an ionization survey meter. Scattered radiation in X-ray rooms was generated intermittently and showed a low dose rate. Consequently, it was established that dose leakage from X-ray rooms must be measured with an integrating dosimeter. It was suggested that the measurement method of environmental dose with OSLD was useful to measurement for radiation control.     

Patient dose measurement with fluorescent glass dosimeter: characteristics evaluation and patient skin dose measurement in abdominal interventional radiology

In this study, we investigated the usefulness of the fluorescent glass dosimeter for measuring patient dose. The fluorescent glass dosimeter is constructed of a glass element and its holder. One type has a tin (Sn) filter and the other does not. The characteristics of these two types of fluorescent glass dosimeters were studied in the range of diagnostic X-ray energy. The result was excellent for each characteristic. Directional dependency, however, was recognized in the fluorescent glass dosimeter with tin (Sn) filter. Based on these evaluations, patient skin dose was measured for abdominal interventional radiology and diagnostic digital subtraction angiography using the holder without filter, which is less direction-dependent and eliminates obstructive shadows in radiography and fluoroscopy. The average skin dose of 30 patients for abdominal IVR was 1.17+/-0.44 Gy (0.51-1.94 Gy), while those for diagnostic DSA examination was 0.54+/-0.21 Gy (0.15-1.02 Gy). The fluorescent glass dosimeter provides high capability for skin dose measurement. The fluorescent glass dosimeter is also useful for controlling patient dose during IVR procedures.     

Comparison of effective doses obtained from dose-area product and air kerma measurements in interventional radiology

In this study, measurements of dose-area product (DAP) and entrance dose were carried out simultaneously in a sample of 162 adult patients who underwent different interventional examinations. Effective doses for each measurement technique were estimated using the conversion factors that have been determined for specific X-ray views in a mathematical phantom. Exposure conditions used in clinical practice never match these theoretical models exactly, and deviations from the assumed standard conditions cause uncertainties in effective dose estimations. Higher effective dose values are found if the air kerma results are used rather than DAP readings, both for patient and Rando phantom studies. Comparison of DAP, fluoroscopy times and skin doses were made with published data. DAP measurement for the effective dose calculation and thermoluminescent dosimeter for the skin dose estimates are found to be the most reliable methods for patient dosimetry.     

Estimation of the effective dose of patient in interventional radiology: study of coronary angiography

The applications of interventional radiology (IVR) increasingly are being used in clinical examinations, where they tend to extend examination time. In addition, the risk of occupational exposure necessarily is increasing with this technology. In this study, the dose distributions in a sliced acrylic-acid phantom involving the bore for each irradiation condition were measured using a thermoluminescence dosimeter (TLD). Four patterns of set-up for the fluoroscopy unit were chosen as references for the conditions generally used clinically. Exposure also was measured with dose area product (DAP), and we then calculated the entrance skin dose and effective dose for the patient. The results showed that the effective dose was 7.0 mSv to 8.0 mSv at LAO45 degrees and RAO30 degrees; 100 kV, 2.3 mSv to 3.3 mSv at LAO45 degrees and RAO30 degrees; 80 kV. The effective dose is greatly influenced by the setup of fluoroscopy in IVR. The change in DAP is especially influenced. We found that the relation between DAP and effective dose was corrected with the exponential function. The effective doses were not necessarily less than those of other radiation examinations, and increase. When PCI and TAE are repeated many times in IVR, we propose that the effective dose should be taken into consideration together with the skin dose for dose control management.     

Skin and thyroid dosimetry in cervical spine screening: two methods for evaluation and a comparison between a helical CT and radiographic trauma series

OBJECTIVE: The first objective of this study was to test the hypothesis that estimates of radiation dose from an ionization chamber correspond to thermoluminescent dosimeter measurements in patients with suspected cervical spine injury. The second objective was to compare the radiation dose of a protocol using helical CT of the entire cervical spine with that of a protocol using radiography alone. SUBJECTS AND METHODS: Thermoluminescent dosimeter measurements of radiation dose to the skin over the thyroid were made in two patient groups: six patients evaluated with CT of the cervical spine and six patients evaluated with radiography. The skin dose for both groups was estimated with an ionization chamber, and the thermoluminescent dosimeter measurements and ionization chamber estimates of skin dose were compared for both groups. Using the ionization chamber, we estimated the radiation dose to the thyroid for all 12 patients. With these estimates, we computed the ratios of skin dose and thyroid dose (CT / radiography). RESULTS: Thermoluminescent dosimeter measurements correlated with ionization chamber estimates of skin dose in both patient groups. Using the ionization chamber estimates, we found that CT delivered 26.0 mGy to the thyroid. In the patients evaluated with radiography, the mean thyroid dose was 1.80 mGy (95% confidence interval, 1.05-2.55 mGy). Ionization chamber dose ratios (CT / radiography) for the skin and thyroid were 9.69 and 14.4 mGy, respectively. CONCLUSION: The correlation between the ionization chamber estimates and the thermoluminescent dosimeter measurements supports the use of ionization chamber estimates in future research. Although helical CT of the entire cervical spine is cost-effective in patients at high risk for fracture, the greater than 14-fold increase in the radiation dose to the thyroid emphasizes the importance of clinical stratification to identify patients at high risk for fracture and the judicious use of CT in patients with suspected cervical spine injury.     

介入手术中职业人员眼晶状体受照剂量测量方法及剂量水平研究

目的 建立介入手术中职业人员眼晶状体受照剂量测量方法,调查介入职业人员眼晶状体受照剂量,为降低介入职业人员眼晶状体受照剂量提供科学依据。方法 选择热释光剂量计(TLD)和光激发光剂量计(OSLD),以眼晶状体个人剂量当量H_p(3)刻度;选择包括单X射线管和双X射线管在内的5种型号的数字减影血管造影装置(DSA),选择心血管介入、脑血管介入等不同介入手术,开展介入职业人员的眼晶状体剂量水平测量。结果 调查的5种不同介入手术类型职业人员眼晶状体的个人剂量当量H_p(3)之间差别较大,其中冠状动脉造影术剂量最低,脑部支架植入术剂量最高;同一介入手术类型,第一术者剂量最高,第三术者剂量最低;同一术者的左眼剂量明显高于右眼剂量。此外OSLD测量结果明显高于TLD测量结果。结论 建立的个人剂量当量H_p(3)刻度方法可靠,使用TLD和OSLD两种剂量计用于介入职业人员眼晶状体剂量测量可行,TLD和OSLD两种剂量计现场测量结果有差异。     

心血管病介入操作时患者受照剂量研究

目的 对心血管介入手术中患者所受辐射剂量及与辐射剂量相关的指标进行采集和分析,为改善患者的辐射防护提供依据.方法 对在省属三级甲等医院进行的26例完整的心血管介入手术的患者进行临床数据采集,按手术类别分成冠状动脉血管造影术(CA)及行冠状动脉血管造影术(CA)后继续行经皮穿刺腔内冠状动脉成形术(PTCA)两组,采用TLD个人剂量计照射野矩阵测量法,检测患者荧光照射时间、入射皮肤剂量(ESD)、最高皮肤剂量(PSD)、剂量-面积乘积(DAP)等指标,用TLD测量在模拟心血管手术条件下体模器官剂量.结果 荧光透视时间为(17.7±15.6)min,范围为0.80～42.4 min;ESD范围为(159±138)mGy,4.40～459 mGy;PSD范围为(769±705)mGy,22.6～2.43×103mGy.CA+PTCA组的荧光照射时间、ESD、PSD均大于CA组,差异有统计学意义.最大皮肤受照剂量与透视时间有较好的相关性(r=0.84,P＜0.01).结论 心血管病放射性介入操作时,可通过透视时间来估算最大皮肤受照剂量.

Abstract：

Objective To collect and analyze the radiation dose to patients in cardiovascular interventional procedures and the radiation dose-related indicators,in order to provide a basis for improving radiation protection of patients.MethodsThe clinical data of 26 cases of complete cardiovascular interventional procedures was collected in the municipal Grade A Class Three hospitals,including coronary angiography (CA) and percutaneous transluminal coronary angioplasty (PTCA),and the patient-received radiation doses and other related factors was studied.TLD personal dosimeter radiation field matrix method was used to measure fluorescence time,the entrance skin dose (ESD),the peak skin dose (PSD),dosearea product (DAP) and other indicators.TLD was used to measure the organ dose of the phantom under the cardiovascular interventional procedure condition.ResultsThe fluoroscopy time was (17.7 ±15.6) min during the range of 0.80-42.4 min.The average entrance skin dose (ESD) was (159 ± 138)mGy during the range of 4.40-459 mGy.The peak skin dose (PSD) was (769 ± 705) mGy during the range of 22.6 - 2.43 × 103mGy.The fluorescence time,entrance skin dose (ESD) ,peak skin dose (PSD) of the group CA + PTCA are greater than the group CA and the difference has statistical significan.The peak skin dose and the fluoroscopy time have good linear correlation (r = 0.84,P ＜ 0.01 ).Conclusion The peak skin dose the patient received in cardiovascular interventional radiological operation can be estimated through the fluoroscopy time.     

Patient radiation dose at CT urography and conventional urography

PURPOSE: To measure and compare patient radiation dose from computed tomographic (CT) urography and conventional urography and to compare these doses with dose estimates determined from phantom measurements. MATERIALS AND METHODS: Patient skin doses were determined by placing a thermoluminescent dosimeter (TLD) strip (six TLD chips) on the abdomen of eight patients examined with CT urography and 11 patients examined with conventional urography. CT urography group consisted of two women and six men (mean age, 55.5 years), and conventional urography group consisted of six women and five men (mean age, 58.9 years). CT urography protocol included three volumetric acquisitions of the abdomen and pelvis. Conventional urography protocol consisted of acquisition of several images involving full nephrotomography and oblique projections. Mean and SD of measured patient doses were compared with corresponding calculated doses and with dose measured on a Lucite pelvic-torso phantom. Correlation coefficient (R(2)) was calculated to compare measured and calculated skin doses for conventional urography examination, and two-tailed P value significance test was used to evaluate variation in effective dose with patient size. Radiation risk was calculated from effective dose estimates. RESULTS: Mean patient skin doses for CT urography measured with TLD strips and calculated from phantom data (CT dose index) were 56.3 mGy +/- 11.5 and 54.6 mGy +/- 4.1, respectively. Mean patient skin doses for conventional urography measured with TLD strips and calculated as entrance skin dose were 151 mGy +/- 90 and 145 mGy +/- 76, respectively. Correlation coefficient between measured and calculated skin doses for conventional urography examinations was 0.95. Mean effective dose estimates for CT urography and conventional urography were 14.8 mSv +/- 90.0 and 9.7 mSv +/- 3.0, respectively. Mean effective doses estimated for the pelvic-torso phantom were 15.9 mSv (CT urography) and 7.8 mSv (conventional urography). CONCLUSION: Standard protocol for CT urography led to higher mean effective dose, approximately 1.5 times the radiation risk for conventional urography. Patient dose estimates should be taken into consideration when imaging protocols are established for CT urography.     

Radiation dose measurement of the patient in interventional radiology using a transmission ionization chamber

We propose a method to estimate patient radiation dose in radiologically guided interventional procedures using a transmission ionization chamber. A typical transarterial embolization (TAE) procedure for hepatocellular carcinoma was simulated, including 30 minutes of fluoroscopy and five series of DSA, each with appropriate collimation. The dose-area product was divided by the area and compared with values from a standard dosimeter placed in the center of the radiation entrance, to obtain a conversion factor. In this way, the entrance skin dose can be estimated immediately after the procedure by simply multiplying the value by the conversion factor, if the procedure roughly conforms to the simulated model. The average entrance skin dose of 33 patients who recently underwent TAE for HCC was found to be 0.66 (0.19-1.75) Gy. This technique can be applied to other areas of IVR and may help to reduce patient exposure to radiation.     

Quality assurance procedures for the Peacock system.

The Peacock system is the product of technological innovations that are changing the practice of radiotherapy. It uses dynamic beam modulation technique and inverse planning algorithm, both of which are new methodologies, to perform intensity-modulation radiation therapy (IMRT). The quality assurance (QA) procedure established by Task Group No. 40 did not adequately consider these emerging modalities. A review of literature indicates that published articles on QA procedures concentrate primarily on the verification of dose delivered to phantom during commissioning of the system and dose delivered to phantom before treating patients. Absolute dose measurements using ion chambers and relative dose measurements using film dosimetry have been used to verify delivered doses. QA on equipment performance and equipment safety is limited. This paper will discuss QA on equipment performance, equipment safety, and patient setup reproducibility.     

Evaluation and estimation of entrance skin dose in patients during diagnostic and interventional radiology procedures

A study was performed to evaluate the total entrance skin dose (ESD) of patients during diagnostic and interventional radiology procedures (IVR) and to estimate ESD with body mass index (BMI) and fluoroscopy time. The study included 26 cases of transcatheter arterial embolization therapy (TAE) for hepatocellular carcinoma (HCC) and 19 cases of diagnostic digital subtraction angiography (DSA) for HCC. The ESD of patients was evaluated with a zinc-cadmium sensor linked to a digital counter (SDM: skin dose monitor). Exposure doses were measured with SDM attached to the front of the X-ray beam-limiting device like a dose area product monitor. ESD was calculated from the measured exposure dose. In 26 TAE for HCC, ESD was 1793.7+/-739.1 mGy, with the mean fluoroscopic time of 23.5 minutes and 4.4 DSA acquisitions. The fluoroscopic dose rate was 52.4+/-11.5 mGy/min. In 19 diagnostic DSA for HCC, ESD was 962.9+/-375.2 mGy, with the mean fluoroscopic time of 11.1 minutes and 4.0 DSA acquisitions. The fluoroscopic dose rate was 32.7+/-12.7 mGy/min. Although 33.2% of ESD was from fluoroscopy in diagnostic procedures, the figure was 68.8% in TAE procedures. It was demonstrated that the increase in ESD during IVR was caused by the rise of fluoroscopy dose rate caused by high-magnification fluoroscopy and the extension of fluoroscopy time. In order to reduce ESD, it is necessary to use a low fluoroscopy dose rate with low-rate pulse fluoroscopy, in addition to shortening fluoroscopy time. Fluoroscopy time was a poor predictor of risk because it did not correlate well with ESD during IVR (diagnostic procedures r(2)= 0.897, IVR r(2)= 0.594). However, ESD correlated well with the product of BMI and fluoroscopy time (diagnostic procedures r(2)= 0.910, IVR r(2)= 0.783). The linear relationship between ESD and the product of BMI and fluoroscopy time provides a simple monitoring mechanism of the ESD delivered to the patient during interventional radiology procedures. This linear relationship needs to be established for other types of interventional procedures.     

Estimation of personal dose based on the dependent calibration of personal dosimeters in interventional radiology

The purpose of present study is, in interventional radiology (IVR), to elucidate the differences between each personal dosimeter, and the dependences and calibrations of area or personal dose by measurement with electronic dosimeters in particular. We compare space dose rate distributions measured by an ionization survey meter with the value measured by personal dosimeter: an optically stimulated luminescence, two fluoroglass, and two electronic dosimeters. Furthermore, with electronic dosimeters, we first measured dose rate, energy, and directional dependences. Secondly, we calibrated the dose rate measured by electronic dosimeters with the results, and estimated these methods with coefficient of determination and Akaike's Information Criterion (AIC). The results, especially in electronic dosimeters, revealed that the dose rate measured fell by energy and directional dependences. In terms of methods of calibration, the method is sufficient for energy dependence, but not for directional dependence, because of the lack of stable calibration. This improvement poses a question for the future. The study suggested that these dependences of the personal dosimeter must be considered when area or personal dose is estimated in IVR.     

Examination of types of exposure and management methods for nurses in interventional radiology

Although a large number of studies have been done on exposure to operators and doctors during interventional radiology(IVR), there have been very few reports on nurses. This study was carried out to clarify the situation regarding exposure for nurses, and provides examples of how to estimate and manage. We measured space dose-rate distributions with an ionization survey meter, and personal exposure dose by a small fluorescent grass dosimeter(Dose Ace). The experimental results disclosed that there tended to be two types of exposure depending on the task performed. Head and neck(collar level)were associated with the highest exposure dose, which was observed in nurses assisting operators. Alternatively, knees showed the highest exposure dose, which was observed in nurses observing and assisting the patient. When estimation of skin equivalent exposure at the knees is needed, it can be calculated by using the value measured at the collar level. Furthermore, in estimating exposure dose, the directional and energy characteristics of personal dosimeters should be considered adequate. For radiation management, a circular protective sheet can be placed around the patient's lower area and a protective screen near the patient's head, and basic and practical education can be given. We concluded that these are highly useful for the personal monitoring of nurses engaged in IVR.     

Evaluation of patient doses in interventional radiology]

PURPOSE: To verify the suitability of indicative quantities to evaluate the risk related to patient exposure, in abdominal and vascular interventional radiology, by the study of correlations between dosimetric quantities and other indicators. MATERIAL AND METHODS: We performed in vivo measurements of entrance skin dose (ESD) and dose area product (DAP) during 48 procedures to evaluate the correlation among dosimetric quantities, and an estimation of spatial distribution of exposure and effective dose (E). To measure DAP we used a transmission ionization chamber and to evaluate ESD and its spatial distribution we used radiographic film packed in a single envelope and placed near the patient's skin. E was estimated by a calculation software using data from film digitalisation. RESULTS: From the data derived for measurements in 27 interventional procedures on 48 patients we obtained a DAP to E conversion factor of 0.15 mSv / Gy cm2, with an excellent correlation (r=.99). We also found a good correlation between DAP and exposure parameters such as fluoroscopy time and number of images. The greatest effective dose was evaluated for a multiple procedure in the hepatic region, with a DAP value of 425 Gy cm2. The greatest ESD was about 550 mGy. For groups of patients undergoing similar interventional procedures the correlation between ESD and DAP had conversion factors from 6 to 12 mGy Gy-1 cm-2. CONCLUSION: The evaluation of ESD and E by slow films represents a valid method for patient dosimetry in interventional radiology. The good correlation between DAP and fluoroscopy time and number of images confirm the suitability of these indicators as basic dosimetric information. All the ESD values found are lower than threshold doses for deterministic effects.     

Evaluation of additional lead shielding in protecting the physician from radiation during cardiac interventional procedures

Since cardiac interventional procedures deliver high doses of radiation to the physician, radiation protection for the physician in cardiac catheterization laboratories is very important. One of the most important means of protecting the physician from scatter radiation is to use additional lead shielding devices, such as tableside lead drapes and ceiling-mounted lead acrylic protection. During cardiac interventional procedures (cardiac IVR), however, it is not clear how much lead shielding reduces the physician dose. This study compared the physician dose [effective dose equivalent (EDE) and dose equivalent (DE)] with and without additional shielding during cardiac IVR. Fluoroscopy scatter radiation was measured using a human phantom, with an ionization chamber survey meter, with and without additional shielding. With the additional shielding, fluoroscopy scatter radiation measured with the human phantom was reduced by up to 98%, as compared with that without. The mean EDE (whole body, mean+/-SD) dose to the operator, determined using a Luxel badge, was 2.55+/-1.65 and 4.65+/-1.21 mSv/year with and without the additional shielding, respectively (p=0.086). Similarly, the mean DE (lens of the eye) to the operator was 15.0+/-9.3 and 25.73+/-5.28 mSv/year, respectively (p=0.092). In conclusion, although tableside drapes and lead acrylic shields suspended from the ceiling provided extra protection to the physician during cardiac IVR, the reduction in the estimated physician dose (EDE and DE) during cardiac catheterization with additional shielding was lower than we expected. Therefore, there is a need to develop more ergonomically useful protection devices for cardiac IVR.     

Conversion factor for CT dosimetry to assess patient dose using a 256-slice CT scanner

Recent rapid progress in CT technology has yielded equipment with large numbers of detector rows and standard computed tomography dose index (CTDI) is therefore no longer an adequate integration range. An integration range of 300 mm is necessary to accurately measure dose under a nominal beam width of 128 mm due to scattered radiation. However, such a long phantom is inconvenient to use routinely in cone-beam CT patient dose checking. To assess patient dose accurately with standard dosimetry methods, we determined a conversion factor (CF) which was calculated from the weighted dose profile integral (DPI(w)) for the 300 mm integration range with a 300 mm long CTDI phantom using a 300 mm long ionization chamber divided by that for the 100 mm integration range with a standard CTDI phantom (140 mm long) with a 100 mm long chamber. CF values increase with increasing nominal beam width and effective energy in the range from 1.5 to 2.0. CF values can also be adapted for use with other CT systems as their dose profiles are thought to be analogous to those for the 300 mm phantom and are useful in any hospital situation to assess accurate patient doses using standard dosimetry methods.     

Effective dose in Albanian direct chest fluoroscopy

In the absence of reliable supplies of X-ray film, direct fluoroscopy is still extensively used in Albania, with chest radiology a particularly common application. This paper aims to quantify both patient skin dose and the risk-related quantity effective dose for direct fluoroscopy units based in seven different Albanian X-ray departments. A standard Quality Assurance (QA) protocol was used to assess tube potential accuracy, half value layer and X-ray tube output of these units. Three groups of X-ray beam parameters were defined from the QA results, covering the range of chest posteroanterior (PA) fluoroscopy technique factors seen during the study. Organ-equivalent doses were then measured for a nominal PA chest fluoroscopy examination using a Rando anthropomorphic phantom loaded with lithium fluoride thermoluminescent dosimeter chips. Normalised organ dose factors are listed for the three groups of beam conditions simulated. Using these factors, effective dose for the seven systems surveyed was found to be between 0.06 and 0.42 mSv for a 20 s PA chest fluoroscopy examination. Mean effective dose for this group of systems was 0.22 mSv which is a factor of 13 greater than mean effective dose for film/screen PA chest radiography in the UK, whereas entrance surface dose was a factor of 50 greater than the current EU reference level. Received: 11 February 2000 Accepted: 23 May 2000     

Report on the 89th Scientific Assembly and Annual Meeting of the Radiological Society of North America--analysis of radiation dose by a change of a scan parameter of multi-slice computed tomography by a film method

PURPOSE: It is for a purpose of this study to measure radiation dose by analyzing a dose profile of multi-slice computed tomography varying with helical pitch and a row slice thickness difference complicatedly. MATERIALS AND METHODS: We used multi-slice computed tomography, and helical pitch and row slice thickness change and scanned the helical scan. I used CTDI phantom of a diameter of 25 cm and I inserted roentgen diagnosis use film UR-2(new) which I put between my own phantom in center and 1 cm away from the outer surface and scanned it. And the provided level profile was converted into a dose profile with the dose-density curve which I made beforehand. I analyzed radiation dose than the dose profile. RESULT: In multi-slice computed tomography, radiation dose varied with assembly of row slice thickness and helical pitch. The change of a dose profile changed in a phantom surface part complicatedly. The maximum dose by the measurement of this time was 29 mGy in row slice thickness 0.5 mm, assembly of helical pitch 2.5. In addition, the minimum dose was 6.8 mGy in row slice thickness 3.0 mm, assembly of helical pitch 5.5. And, as for the difference of maximum dose in the same dose profile and the smallest dose, there were about 20 % in row slice thickness 1.0 mm, assembly of helical pitch 5.5. CONCLUSION: The dosimetry of multi-slice computed tomography by a film method enabled it to measure a change of a dose profile by a difference of a scan parameter by high interest solution ability. In addition, it is a method more superior in dosimetry of multi-slice computed tomography spreading through a Z-axis direction broadly than determination by computed tomography use ionization chamber dosimeter. Because radiation dose increases by a scan in thin row slice thickness and small helical pitch, care is necessary.     

用治疗级电离室测量短脉冲高剂量率X射线的实验研究

目的 探索研究治疗级电离室用于短脉冲高剂量率X射线的快速测量。方法 利用内插法测量某电子加速器装置所致脉冲X射线半值层,估算其等效能量;采用治疗级电离室和热释光测量方法,对比设备周围同一方向不同距离处相同数量脉冲辐射的累积剂量;分析电离室剂量仪测量结果与源距离之间的关系,对比不同频率下同一位置相同数量脉冲辐射的累积剂量。结果 工作状态下,距设备外壁1~12 m累计接收100个脉冲辐射,热释光测得空气比释动能范围0.08~9.65 mGy,电离室剂量仪所测范围0.08~9.85 mGy,两者相差在10%以内;距设备正前方2 m处,不同频率（1~10 Hz）下,电离室剂量仪所测100个脉冲所致X射线空气比释动能无明显差异（P>0.05）。结论 在实验所涉加速器装置的剂量率和脉冲频率范围内,治疗级电离室剂量仪可用于短脉冲X射线辐射剂量的快速测量。