辐射着色胶片XR-RV3和EDR2的剂量学性能比较

目的 比较两种用于介入放射学程序中患者峰值皮肤剂量测量的胶片性能,包括胶片的灰度随时间变化、灵敏度、能量响应、剂量响应等特性。方法 分别在60、80、100、120和140 kV 5档管电压下自由空气中照射GafChromic XR-RV3 胶片和KODAK EDR2胶片800 mGy剂量,测量结果归一到80 kV分析胶片的能量响应。在模体上用80 kV管电压分别照射两种胶片0.025~10 Gy剂量,分析胶片的灵敏度和剂量响应。采用Epson V750平板扫描仪对两种胶片进行扫描分析,分别测量图像的红、绿、蓝3色通道的像素值。结果 在灰度随时间变化上,XR-RV3胶片在照射后的24 h内灰度的变化为2%,在72 h内为4%,在6周内为6%;低剂量时EDR2胶片比XR-RV3胶片更灵敏;能量响应方面,在放射诊断能量范围内,XR-RV3胶片的能量响应在9%以内,EDR2胶片的能量响应在23%以内;在0.025~10 Gy的剂量范围内,对于XR-RV3胶片,红光通道随剂量的变化曲线的响应最明显。对于EDR2胶片,3种颜色通道的像素值曲线重合,EDR2胶片在接受剂量超过500 mGy时达到饱和。结论 XR-RV3胶片在灰度变化、能量响应、剂量响应等方面要优于EDR2胶片,非常适和用于介入放射学程序中患者峰值皮肤剂量的测量和分析。     

Independence of calibration curves for EBT Gafchromic films of the size of high-energy X-ray fields.

The EBT Gafchromic radiochromic film is a relatively new product designed specifically for dosimetry in radiation therapy. Due to the weak dependence of its response on the photon energy (variations are below 10% in the 50 kVp-10 MVp range), the film is ideal for dosimetry when the photon energy spectrum may be changing or unknown. In order to convert a map of optical densities into a map of absorbed radiation doses, a calibration curve constructed on the basis of standard calibration films is necessary. Our results have shown that, with the EBT Gafchromic film, one can use the same calibration curve for 6-MV X-ray fields of any size in the range from 5 x 5 cm(2) up to 40 x 40 cm(2). This is not the case for radiographic films, such as Kodak X-Omat V, whose response to the same dose varies approximately by 10% depending on the field size in this range. This insensitivity of the EBT Gafchromic film to size of the radiation field makes it possible to assess doses delivered by small radiation fields. With the help of this film, it was shown that the output factor for a 0.5 x 0.5 cm(2) field is 0.60+/-0.03 (2SD) relative to the 10 x 10 cm(2) field.     

Mutagenic effect of low energy neutrons on human chromosome 11

PURPOSE: The shape of the dose-effect curve for neutrons, i.e. the question as to whether the curve is linear or supralinear in the low-dose region, is still not clear. Therefore, the mutagenic effect of very low doses of low-energy neutrons was determined. MATERIALS AND METHODS: Human-hamster hybrid A(L) cells contain human chromosome 11, which expresses the membrane protein CD59. This membrane protein can be detected immunologically and quantified by flow cytometry. The A(L) cells were irradiated with neutrons of 0.565, 2.5 or 14.8 MeV and the results were compared with those after 200 kVp X-rays. Before irradiation, cells spontaneously mutated in the CD59 gene were removed by magnetic cell sorting (MACS). RESULTS: The relative biological effectiveness (RBE) for CD59 mutation induction was 19.8 (+/-2.7) for 0.565 MeV, 10.2 (+/-1.9) for 2.5 MeV, and 10.2 (+/-1.6) for 14.8 MeV neutrons. Linear mutation responses were obtained with all radiations except for 14.8 MeV neutrons where a supralinear curve may be a better fit. The deletion spectrum of mutated cell clones showed 29 Mbp deletions on average after irradiation with 0.069 Gy of 0.565 MeV neutrons. This scale of deletions is similar to that after 3 Gy 100 kV X-rays (=34 Mbp). For 50% cell survival, the RBE of the neutrons was 11 compared with 200 kV X-rays. CONCLUSIONS: Neutrons of low energies (0.565 or 2.5 MeV) produce a linear dose-response for mutation in the tested dose range of 0.015-0.15 Gy. The neutron curve of 14.8 MeV can be approximated by a curvilinear or linear function.     

Thermoluminescent response of CaSO4:Dy+PTFE induced by X-ray beams

The aim of the present work was to evaluate the feasibility of the utilization of CaSO4:Dy pellets for X-ray measurements in a general radiology department. Thermoluminescence (TL) response of CaSO4:Dy+PTFE was compared to the TL response of commercial LiF:Mg,Ti (TLD-100) samples. TL pellets were exposed to X-ray beam from X-ray machine CMR for clinical diagnosis purpose. The calibration curve of CaSO4:Dy+PTFE was obtained and it showed a linear response as a function of absorbed dose in air at the studied dose interval. Despite this fact, this material can be used for X-ray beams measurements if appropriate calibration procedures are performed.     

Luminescent characteristics of CaSO4:Dy films obtained by spray pyrolysis method

The present paper reports the experimental results of dysprosium doped calcium sulphate (CaSO4:Dy) films deposited by spray pyrolysis method. CaSO4:Dy films were deposited on three different surfaces: glass, aluminum and quartz substrates at temperatures in the range from 450 to 600 °C. Structural and morphological characteristics of CaSO4:Dy films were observed. Thermoluminescent characteristics of films were determined by irradiating ultraviolet energy region. Thermoluminescent glow curve of CaSO4:Dy films with glass and aluminum substrates showed a peak under environmental irradiation. Both TL response glow shape and intensity of CaSO4:Dy films UV irradiated as a function of substrates were studied.     

Technical note: Electrocardiogram electrode repositioning for 320-row coronary CT angiography in patients with regular and recurrent premature ventricular contractions

Arrhythmias can compromise image quality and increase radiation exposure during coronary CT angiography (CTA). However, premature ventricular contractions (PVCs) can occur in a predictable recurrent and regular pattern (ie, bigeminy, trigeminy, quadrigeminy) with post-PVC compensatory pauses. Electrocardiographic (ECG) electrode repositioning can achieve relative amplification of the R waves of PVCs compared with R waves of sinus beats. This technical note describes how simple ECG electrode repositioning, combined with an absolute-delay strategy, facilitated selective R waves of PVC ECG triggering of image acquisition in 6 patients with PVC bigeminy or quadrigeminy at the time of 320-row coronary CTA. All 6 studies were single heartbeat acquisition scans with excellent image quality and a median effective radiation dose of 2.9 mSv (interquartile range, 2.1–3.8 mSv). Standard ECG electrode positions used for 2 patients with PVC bigeminy undergoing coronary CTA were associated with an acquisition over 2 heartbeats and effective radiation doses of 6.8 and 10.3 mSv, respectively. In conclusion, ECG electrode repositioning combined with an absolute-delay strategy for regularly recurring PVCs, such as ventricular bigeminy, facilitates high image quality and lower radiation dose during coronary CTA. This simple and straightforward technique can be considered for all patients with regular and recurrent PVCs undergoing coronary CTA.     

Detection of thoracolumbar vertebral body destruction with lateral spine radiography. Part I: Investigation in cadavers

Despite few and inconclusive studies, radiography is generally believed to be insensitive for detection of osteolytic lesions of the spine. A more detailed investigation was undertaken to study the detectability of laboratory-produced osteolytic lesions in cadaveric thoracolumbar vertebral bodies using conventional lateral radiographs. The radiographs were presented to four radiologists in two sessions over a two month period. In the first session, the films were arranged in a composite of five vertebral bodies, T11 to L3 all from the same spine, in which one contained a lesion and the other four were normal. In the second session, each vertebral body film was presented individually. Area (Az) under the receiver-operating characteristic (ROC) curve was used to measure the performances of readers. Observer detection was similar in the two formats with Az ranging from 0.67 +/- 0.05 to 0.79 +/- 0.04 for the composite film arrangement and 0.57 +/- 0.08 to 0.85 +/- 0.10 for the films of individual vertebral bodies. Lesions were grouped into three relative size categories: 18% to 25%, 26% to 40%, and 41% to 60% of transverse vertebral body diameter. The mean increase in ROC area between the small and large lesions was 0.29 (P less than 0.04) for the composite films and 0.16 (P less than 0.05) for the individual films. In the composite study, all readers showed significant (P less than 0.05) increases in lesion detection in spines reflecting large increases (P less than 0.01) in bone mineral content.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of temperature,relative humidity,and dose rate on the sensitivity of cellulose triacetate dosimeters to electrons and γ-rays

Cellulose triacetate (CTA) films are useful dosimeters for radiation processing with γ rays and electron beams, and are usually analyzed by u.v. spectrophotometry. The radiation sensitivity of CTA film material increases linearly with both temperature (around room temperature) and relative humidity (between 20 and 80% r.h.) when irradiated at lower dose rates typical for ⁶⁰Co γ-ray irradiation (< 100 kGy h⁻¹). On the other hand, the response depends neither on temperature up to 45°C nor on relative humidity of the surrounding atmosphere during irradiation at high dose rates above 1 MGy h⁻¹, which are typical for electron irradiation. In fact, the extent of temperature dependence and humidity of response are markedly influenced by dose rate. There are also appreciable influences of temperature and relative humidity changes during the post-irradiation storage, but in this case there is no difference of storage effect for different dose levels. The thickness of CTA film influences the dose-rate dependence in the range between 10 kGy h⁻¹ and 1 MGy h⁻¹, but not the dependence on temperature during irradiation. Other environmental influences on the sensitivity were also examined, for the purpose of evaluating systematic uncertainties due to these effects in practical dosimetry.     

Short communication: Practical aspects for the evaluation of skin doses in interventional cardiology using a new slow film

Mapping skin doses in complex fluoroscopy interventions is useful to determine the probability of a possible injury, to detect areas of overlapping irradiation fields and to obtain a permanent register of the most exposed patient skin areas. To fulfil this task, large films with slow X-ray response can be used. Recently, Kodak has introduced a new radiotherapy verification film, named EDR2 (Extended Dose Range). The aim of this paper is to analyse the possibilities of using this new film for estimating skin dose distributions in interventions with potentially higher doses, such as complex percutaneous transluminal coronary angioplasty (PTCA), intravascular brachytherapy procedures (IVB) or cardiac ablations. The EDR2 film by Kodak is an improved option to be used in interventional cardiology to obtain maps of patient skin doses and to estimate maximum skin doses up to 1400 mGy. Film kVp dependence is negligible and the processor conditions can be standardized to obtain skin dose estimations. The linear range for accurate dose measurements is from 50 mGy to 500 mGy.     

Radiation exposure of patients in comprehensive computed tomography of the head in acute stroke

BACKGROUND AND PURPOSE: To assess patient radiation exposure in comprehensive stroke imaging using multidetector row CT (MDCT) combining standard CT of the head, cerebral perfusion (CTP), and CT angiography (CTA) studies. METHODS: Examination protocols for CT and CTA of cerebral and cervical vessels, as well as CTP were simulated using a Somatom Sensation Cardiac 64. Effective doses were derived from measurements with the use of lithium-fluoride thermoluminescent dosimeters (LiF-TLD) at several organ sites using an Alderson-Rando phantom. RESULTS: LiF-TLD measurements resulted in effective doses of 1.7 mSv for CT, 1.9 mSv for CTA of intracranial vessels, and 2.8 mSv for CTA of cervical vessels, respectively. Depending on examination parameters, effective doses varied between 1.1 and 5.0 mSv for cerebral CTP. For CTP, local doses in the area of the primary beam ranged between 114 and 444 mGy. CONCLUSIONS: Comprehensive stroke imaging may result in up to 9.5 mSv with possible local doses of 490 mGy. Although critical doses for organ damage (eg, cataract formation or hair loss) are not reached, physicians need to be aware of possible radiation induced sequelae particularly in repetitive examinations.     

On the use of NHZ-203C Thermoluminescence (TL) reader in clinical dosimetry

The sensitivity vs. dose characteristics of two TL readers (Harshaw 2000 A + B and NHZ-203C) was compared both in the range of small doses (10 microGy to 100 mGy) as well as in the radiation therapy level by using individually calibrated LiF:Mg, Ti detectors manufactured in Poland. The performance of both systems can be predicted by a three parameter theoretical model. The very good reproducibility of the NHZ-203C reader (sigma/D = 0.6%) is important in radiation therapy while the high sensitivity (the lowest detectable dose limit = 3 S.D. of the background = 27 microGy) is useful for radiation protection measurements.     

Mutagenic effect of low energy neutrons on human chromosome 11

Purpose: The shape of the dose–effect curve for neutrons, i.e. the question as to whether the curve is linear or supralinear in the low‐dose region, is still not clear. Therefore, the mutagenic effect of very low doses of low‐energy neutrons was determined.

Materials and methods: Human–hamster hybrid A_L cells contain human chromosome 11, which expresses the membrane protein CD59. This membrane protein can be detected immunologically and quantified by flow cytometry. The A_L cells were irradiated with neutrons of 0.565, 2.5 or 14.8?MeV and the results were compared with those after 200?kVp X‐rays. Before irradiation, cells spontaneously mutated in the CD59 gene were removed by magnetic cell sorting (MACS).

Results: The relative biological effectiveness (RBE) for CD59 mutation induction was 19.8 (±2.7) for 0.565?MeV, 10.2 (±1.9) for 2.5?MeV, and 10.2 (±1.6) for 14.8?MeV neutrons. Linear mutation responses were obtained with all radiations except for 14.8?MeV neutrons where a supralinear curve may be a better fit. The deletion spectrum of mutated cell clones showed 29?Mbp deletions on average after irradiation with 0.069?Gy of 0.565?MeV neutrons. This scale of deletions is similar to that after 3?Gy 100?kV X‐rays (=34?Mbp). For 50% cell survival, the RBE of the neutrons was 11 compared with 200?kV X‐rays.

Conclusion: Neutrons of low energies (0.565 or 2.5?MeV) produce a linear dose–response for mutation in the tested dose range of 0.015–0.15?Gy. The neutron curve of 14.8?MeV can be approximated by a curvilinear or linear function.     

The low energy X-ray response of the LiF:Mg:Cu:P thermoluminescent dosemeter: a comparison with LiF:Mg:Ti

LiF:Mg:Cu:P thermoluminescent dosemeters (TLD) can be used for the same X-ray dosimetry applications as LiF:Mg:Ti, with each type having the disadvantage of a response dependent on energy, particularly at low energies. Measurements were made of the response per unit air kerma of LiF:Mg:Cu:P and LiF:Mg:Ti to nine quasi-monoenergetic X-ray beams with mean energies from 12 keV to 208 keV. Each measurement was normalized to the value produced by 6 MV X-rays. LiF:Mg:Cu:P was found to under-respond to a majority of these radiations whereas LiF:Mg:Ti over-responded to a majority. Their smallest relative measured response was produced by the lowest energy beam, and the maximum measured relative response of 1.15+/-0.07 and 1.21+/-0.07 for LiF:Mg:Cu:P and LiF:Mg:Ti, respectively, occurred at 33 keV. Energy response coefficients were derived from these measurements to estimate the error introduced by using either type of TLD to measure the dose from an X-ray spectrum different to that used for its absolute response calibration. It was calculated that if the response of either type of TLD was calibrated at 100 kVp, then an error of no more than +/-2% would be introduced into measurements of tube output at potentials of 50-130 kVp. LiF:Mg:Cu:P was found to introduce a larger error (up to 30%) into the measurement of body exit dose than LiF:Mg:Ti at tube potentials of 40-150 kVp, if its absolute response was calibrated using the corresponding body entrance beam. The method should allow this type of error to be estimated in other dosimetry applications for either type of TLD.     

Evaluation of radiographs developed by a new ultrarapid film processing system

The image quality of radiographs developed by a new ultrarapid processor was evaluated to determine if faster processing causes degradation in the image. The processor used was the Konica Super-Rapid SRX-501 model. Two films designed for this processor (Konica MGH-SR and MGL-SR) were processed in 45 sec and were compared with standard rapid processing in 90 sec of corresponding conventional films (Kodak TMG and OC). Rare-earth screens (Kodak Lanex Regular and Lanex Medium) used with the new and conventional films interleaved during angiographic studies or for phantom images were assessed for image quality. The basic imaging properties of the screen-film systems were examined by measuring (1) Hurter and Driffield curves, (2) modulation transfer functions by using the slit method, and (3) noise Wiener spectra. Subjective clinical assessment showed that the images obtained with ultrarapid processing were acceptable, with increased contrast and graininess. Hurter and Driffield curve measurements confirmed higher gradients. Modulation transfer function measurements were the same as for the conventional films. Noise Wiener spectrum measurements showed a 10% increase in noise for MGH-SR vs TMG film and a 30% increase for MGL-SR vs OC film. We conclude that acceptable image quality can be obtained using ultrarapid processing, with processing time approximately 60% that of conventional rapid processing. Potential applications include all areas in which rapid availability of the radiograph for interpretation is important. Although the processor studied was the first of its kind available, our evaluation indicates that the technology is available for a new class of ultrarapid processors.     

90Sr- 90Y敷贴治疗的EBT3胶片剂量验证方法

目的:对 90Sr- 90Y敷贴治疗进行EBT3胶片剂量的测量,为临床应用提供一种快捷的剂量验证方法。 方法:选用能量响应较好的辐射直接显影EBT3胶片,并与固体水模进行比较,通过直线加速器建立0~500 cGy的胶片灰度-剂量标准曲线并检测其组织等效性。将20片6 cm×6 cm的E...     

CaSO4 (Dy) thermoluminescent dosimeters for the determination of gonadal doses.

For the measurement of gonadal doses sensitive dosimeters are necessary. Since CaSO4 (Dy) thermoluminescent dosimeters are very sensitive the energy dependence has been measured as compared to LiF in the tube potential region between 50 and 150 kV. Moreover the output of the LiF dosimeters was compared with the results of ionization chamber measurements. Although the energy dependence of CaSO4 (Dy) is well-known the actual dependence on the potential appears to be within +/- 10% for moderately filtered beams in the region from 50 to 150 kV.     

Diagnostic accuracy of CT angiography in infants with tetralogy of Fallot with pulmonary atresia and major aortopulmonary collateral arteries

BackgroundCT angiography (CTA) is increasingly used for the evaluation of congenital heart disease.ObjectiveThe aim was to determine the diagnostic accuracy of CTA in infants with tetralogy of Fallot with pulmonary atresia (ToF-PA) and major aortopulmonary collateral arteries (MAPCAs).MethodsWe retrospectively evaluated 18 consecutive patients (7 girls; median age, 6 days; range, 1–334 days) with ToF-PA and MAPCAs. Findings on CTA were compared with diagnostic catheterization (n = 16) or intraoperative findings (n = 2) for the number of MAPCAs, their diameter, origin, and supplied lung lobes and for the presence and diameter of central pulmonary arteries. Spearman correlation coefficient was calculated to assess the correlation between diameter measurements on CTA and catheterization. CTA dose-length product and catheterization dose-area product were recorded, and effective radiation doses were calculated with the use of age-specific conversion factors.ResultsAgreement was found between CTA and catheterization or intraoperative findings for the number of MAPCAs, their origin, and supplied lung lobes in all cases. In 11 of 13 patients, CTA accurately demonstrated central pulmonary arteries. A good correlation was found between diameter measurements on CTA and catheterization for MAPCAs (r = 0.83) and central pulmonary arteries (r = 0.82). Median effective doses were 0.9 mSv for CTA and 14.4 mSv for catheterization (P < .001).ConclusionCTA is accurate in the preoperative evaluation of infants with ToF-PA and MAPCAs and is associated with a substantially lower radiation dose than catheterization. Preoperative diagnostic catheterization, therefore, may only be necessary in select patients with small MAPCAs in whom the precise assessment of central pulmonary arteries is required for surgical planning.     

A personal thermoluminescence dosimeter using LiF:Mg,Cu,Na,Si detectors for photon fields.

A new personal thermoluminescence (TL) dosimeter for photon fields using LiF:Mg,Cu,Na,Si TL detector was developed by taking advantage of its dosimetric properties including energy dependencies. Solid pellet type LiF:Mg,Cu,Na,Si detector was developed and fabricated at Korea Atomic Energy Research Institute (KAERI) and has been studied on its dosimetric properties such as TL grow curve, dose response, energy response and reusability. Its dosimetric properties show the feasibility of application of LiF:Mg,Cu,Na,Si TL detector to personal dosimetry fields. A new dosimeter using LiF:Mg,Cu,Na,Si TL detector was designed and tested through irradiation experiments. This multi-element TL dosimeter allows the measurement of a personal dose equivalent Hp(d) in photon fields. Based on the experimental results of the proposed dosimeter, it was demonstrated that a personal TL dosimeter using sintered LiF:Mg,Cu,Na,Si TL detector is appropriate to estimate personal dose equivalent for wide range energy of photon fields.     

EBT3和EDR2胶片对扫描束碳离子剂量的响应研究

目的 研究EBT3和EDR2胶片对于不同传能线密度和剂量碳离子响应。方法 EBT3和EDR2胶片采用两种方法进行光密度-剂量校准：一是将胶片放置在固体水与束流垂直测量深度,每张胶片接受同能量不同剂量碳离子照射;二是将多张完整胶片放置与束流垂直固体水不同深度,采用碳离子单次照射,在胶片不同区域形成不同物理剂量校准野。结果 在测量范围内,EBT3胶片光密度-剂量校准曲线（下称校准曲线）呈双曲线型,不同传能线密度校准曲线间最大差异为±17%;而EDR2校准曲线呈直线形,不同传能线密度间差异为±27.4%;两种胶片剂量响应均受碳离子在胶片测量深度传能线密度影响,传能线密度越大,胶片光密度响应越低;EBT3胶片灵敏度与剂量呈反比,但EDR2胶片灵敏度则与剂量无关。结论 EBT3胶片响应受传能线密度和剂量双重影响,限制了其在碳离子剂量测量方面的应用。EDR2胶片响应虽受传能线密度影响更大,但受单能碳离子照射时,由于其灵敏度与剂量无关,可用于单能碳离子剂量测量。     

Coronary CT angiography versus intravascular ultrasound for estimation of coronary stenosis and atherosclerotic plaque burden: A meta-analysis

BackgroundNumerous studies have compared coronary CT angiography (CTA) with quantitativecoronary angiography. However, the ability of coronary CTA to identify atherosclerosis and to accurately measure plaque and coronary area and volume measurements as compared with intravascular ultrasound (IVUS) has not been fully defined.ObjectiveWe sought to assess the ability of coronary CTA to quantify coronary and plaque measurements commonly performed with IVUS.MethodsWe searched multiple databases for diagnostic studies that directly compared coronary CTA and IVUS for coronary plaque detection, vessel luminal area, percentage of area stenosis, plaque area, and plaque volume. We used a bivariate mixed-effects binomial regression model to pool test sensitivity and specificity for detection of any coronary plaque.ResultsForty-two studies that evaluated 1360 patients (75% men; mean age, 59 years) were identified. No significant difference was found between coronary CTA and IVUS measurements of vessel lumen cross-sectional area, plaque area, percentage of area stenosis, or plaque volume within the overall cohort and no difference for the measurement of cross-sectional area (n = 5 studies) and plaque volume (n = 8 studies) among a subgroup that used automated or semiautomated measurement techniques. Sensitivity and specificity of coronary CTA to detect any plaque compared with IVUS were 93% and 92%, respectively, with an area under the receiver-operating curve of 0.97.ConclusionsCompared with IVUS, coronary CTA appears to be highly accurate for estimation of luminal area, percentage of area stenosis, plaque volume, and plaque area and for detection of plaque. The use of automated vessel and stenosis measurements appears promising in limited studies to date.