Mammography in New Zealand: radiation dose and image quality.

The mean glandular doses to the breast, image quality and machine performance have been determined for all mammographic x-ray facilities in New Zealand, during 1988-89. For 30 mm and 45 mm phantoms the mean doses per film were 1.03 +/- 0.56 mGy and 1.97 +/- 1.06 mGy. These doses are within international guide-lines. Image quality (detection of simulated microcalcifications, and contrast-detail performance) was found to depend on focal spot size/FFD combination, breast thickness, and film processing. The best machines could resolve 0.2 mm aluminium oxide specks with the contact technique. The use of a grid improved image quality as did magnification. Extended cycle film processing reduced doses, but the claimed improvement in image quality was not apparent from our data. The machine calibration parameters kVp, HVL and timer accuracy were in general within accepted tolerances. Automatic exposure controls in some cases gave poor control of film density with changing breast thickness.     

Dose optimization for different medical imaging tasks from exposure index, exposure control factor, and MAS in digital radiography

ABSTRACT: In radiographic examination, not all medical imaging tasks require the same level of image quality or diagnostic information. Criteria should be established for different imaging tasks to avoid excessive doses where there is no clear net benefit in the diagnosis or the image quality. An exposure index provided by manufacturers would be a useful tool for this purpose. This study aims to establish an optimum exposure index to be used as a guideline for clinical imaging tasks to minimize radiation exposure for chest digital radiography. A three-level classification of image quality (high, medium, and low) for chest imaging tasks was carried out. An anthropomorphic phantom was employed to establish minimum exposure index and exposure (mAs) for clinical imaging task type I (corresponding to high image quality). The exposures of medium and low quality images derived from it. Thirty patients were exposed consecutively with these optimized exposure factors, and clinical tasks were considered, while another 30 patients were exposed with the exposure factors routinely used in practice. Image quality was assessed objectively by a consensus panel. The optimized exposure provided a significant reduction of the mean exposure index from 1,556 to 1,207 (p < 0.0001) and mean patient's entrance surface dose from 0.168 mGy to 0.092 mGy (p < 0.0001). The results show that a clinical-task-determined radiographic procedure is more conducive to radiation protection of patients. In this study, the posteroanterior chest imaging examination was chosen as an example. This procedure can also apply to other body parts and views.     

我国乳腺X射线摄影受检者乳腺剂量水平调查研究

目的 通过调查全国15个省市不同级别医疗机构乳腺X射线摄影曝光参数并测量计算受检者乳腺平均剂量,分析我国乳腺X射线摄影中受检者压迫后乳房厚度分布及乳腺受照剂量水平,为建立适合我国成年女性受检者乳腺X射线摄影的剂量指导水平提供依据。方法 按照《医用辐射危害评价与控制技术研究》实施方案的要求,调查临床实际乳腺摄影受检者的年龄、乳房压迫厚度、曝光参数、摄影体位等相关信息,通过手动曝光测量该条件下乳房压迫厚度处的入射空气比释动能(K_a,i),计算受检者的乳腺平均剂量(AGD)。结果 共在全国15个省的149家医院调查了4372例乳腺X射线摄影体位,273台不同类型乳腺X射线摄影设备,包括屏片乳腺X射线摄影、计算机乳腺X射线摄影(乳腺CR)和直接数字乳腺X射线摄影(乳腺DR)设备,对于这三种类型的设备,头尾(CC)位投照时受检者AGD的平均值分别为1.21,1.77,1.61 mGy,AGD的75%位分别为1.36,2.22,1.81 mGy;斜侧(MLO)位时受检者AGD平均值分别为1.02,1.78,1.66 mGy,AGD的75%位分别为1.23,2.46,1.81 mGy。CC位和MLO位时乳房压迫厚度的中位数分别为4.2和4.5 cm。结论 不同类型乳腺X射线摄影设备中,屏片乳腺X射线摄影设备致受检者的乳腺平均剂量最低,其次是乳腺DR设备,乳腺CR设备致患者剂量最高。     

A calibration comparison of mammographic kVp meters.

Modern screen-film mammography employs a molybdenum target and molybdenum filtration to obtain both high image contrast and low patient dose. Typical x-ray emission spectra are therefore dominated by molybdenum's characteristic radiation. The form of such spectra makes the accurate measurement of mammographic kVp difficult. Non-invasive digital kVp meters provide the simplest method of measuring mammographic kVp routinely, with a typical uncertainty of greater than +/- 1 kVp. With the expansion of breast screening, more stringent demands have been placed on these meters and recent calls for accuracies of better than +/- 1 kVp have been made. The responses of six popular mammographic kVp meters were compared in the range 22 to 32 kVp. Agreement between four of these meters above 24 kVp was within 1.8 kVp. The responses of the two remaining meters differed from the other meters by up to 5 kVp over the range. The results have highlighted the need for regular calibration checks on mammographic kVp meters and the provision of a national standard to which these calibrations can be traceable. Such a standard is currently not available in Australia.     

Evaluation of a new mammographic film: methods and considerations

In this study the performance of a new mammographic film, the XMA (Retina), was evaluated in comparison with HT (Agfa). The comparison was made in terms of sensitometric characteristics and in terms of image quality and speed when combined with four different cassettes-HDS (Agfa), Min-R 2000 and Min-R 2190 (Kodak), and AD-MA (Fuji)-using the Leeds TOR(MAX) Mammographic Quality Control phantom. The entrance surface air kerma was calculated from exposure factors and the relative speed of each screen-film combination was determined. These tests revealed that XMA requires about 40% less dose than HT when combined with the same intensifying screen, at a penalty of less than 8% in image quality. When combined with AD-MA the XMA presents the greatest speed, whereas the Min-R 2190 is the best compromise between image quality and breast dose. The above values are indicative of the dilemma that medical physicists and radiologists face when it comes to the selection of a screen-film combination for mammography. Both image quality and breast dose should be considered, but strict instructions on what weight should be assigned to each parameter have not been established yet. Health Phys. 94(4):338-344; 2008.     

数字乳腺X射线摄影中不同靶/滤过组合对辐射剂量的影响

目的 探讨数字乳腺X射线机应用Mo/Mo、Mo/Rh、W/Rh 3种不同靶滤过组合对辐射剂量的影响,以便优化选择摄影技术参数,降低受检者的辐射损伤。方法 应用Siemens MAMMOMAT Inspiration数字乳腺X射线机,Ray Safe X射线质量检测仪。首先使用全自动曝光模式对不同厚度的PMMA模体进行曝光并记录管电流量、管电压等摄影参数,然后采用相同的管电压、管电流量、压迫厚度在不同的靶滤过组合(Mo/Mo、Mo/Rh、W/Rh)模式下进行手动曝光,读取并记录体表入射剂量(ESD),计算平均腺体剂量(AGD)。对不同模体厚度在使用3种不同靶滤过组合时产生的平均腺体剂量进行随机区组的方差分析,采用线性相关和回归观察不同靶滤过组合及不同厚度与AGD的相关性并列出直线回归方程。结果 3种靶滤过组合对不同厚度模体产生的AGD差异有统计学意义,Mo/Mo组合的AGD最高,W/Rh组合的AGD显著降低。使用不同靶滤过组合时模体厚度与AGD均呈显著正相关。结论 W/Rh组合AGD明显低于其他两种组合,乳腺X射线摄影时采用W/Rh组合是最佳选择,可显著降低受检者的辐射剂量。     

Investigation of the practical aspects of an additional 0.1 mm copper x-ray spectral filter for cine acquisition mode imaging in a clinical care setting

Minimizing the x-ray radiation dose is an important aspect of patient safety during interventional fluoroscopy procedures. This work investigates the practical aspects of an additional 0.1 mm Cu x-ray beam spectral filter applied to cine acquisition mode imaging on patient dose and image quality. Measurements were acquired using clinical interventional imaging systems. Acquisition images of Solid Water phantoms (15-40 cm) were acquired using x-ray beams with the x-ray tube inherent filtration and using an additional 0.1 mm Cu x-ray beam spectral filter. The skin entrance air kerma (dose) rate was measured and the signal difference to noise ratio (SDNR) of an iodine target embedded into the phantom was calculated to assess image quality. X-ray beam parameters were recorded and analyzed and a primary x-ray beam simulation was performed to assess additional x-ray tube burden attributable to the Cu filter. For all phantom thicknesses, the 0.1 mm Cu filter resulted in a 40% reduction in the entrance air kerma rate to the phantoms and a 9% reduction in the SDNR of the iodine phantom. The expected additional tube load required by the 0.1 mm Cu filter ranged from 11% for a 120 kVp x-ray beam to 43% for a 60 kVp beam. For these clinical systems, use of the 0.1 mm Cu filter resulted in a favorable compromise between reduced skin dose rate and image quality and increased x-ray tube burden.     

A survey of fluoroscopic equipment in Victoria

A survey of fluoroscopic units in the state of Victoria has been carried out. For fixed fluoroscopy equipment, routine quality assurance tests were carried out on the x-ray tube used for conventional radiographs, and factors relating to image quality and patient dose were measured for the screening tube. For the mobile image intensifiers, quality assurance tests were carried out and factors relating to image quality and patient dose were measured. There was a ratio of about 20 in the dose rates between the units with the highest and lowest screening dose rates with the same size phantom. Guidance levels based on the third quartile values of the entrance dose rates and spot film doses are recommended. The recommended guidance doses are: mobile image intensifier: dose rate: 30 mGy/min; fixed screening unit: dose rate: 42 mGy/min and spot film: 5 mGy.     

全数字化乳腺X射线摄影系统质量控制检测方法探讨

目的:对全数字化乳腺X射线摄影系统的主要参数进行质量控制检测,以保证设备性能良好。方法:采用瑞典奥利科Piranha型乳腺机剂量仪、M12乳腺X射线机性能检测模体对全数字化乳腺X射线摄影系统进行胸壁侧照射野准直、光野与照射野的一致性、管电压指示的偏离、半值层、自动曝光控制重复性、探测器均匀性、伪影、高对比分辨力和乳腺平均剂量等检测。检测完毕根据测算方法计算出检测结果,并判断其是否符合WS 522-2017《乳腺数字X射线摄影系统质量控制检测规范》要求。结果:胸壁侧照射野准直检测中硬币被切割的直径距离为4 mm;光野与照射野的一致性检测中光野与照射野相应边沿的偏差为5 mm;管电压指示的偏离最大值为0.31 kV;靶/滤过为Mo/Mo,半值层为0.34 mmAl;自动曝光控制重复性的偏差为2.6%;探测器均匀性检测中图像中心区域与边缘区域兴趣区像素值的偏差为1.60%;无影响临床影像的伪影;高对比分辨力纵向为8 lp/mm,横向为10 lp/mm;乳腺平均剂量为0.61 mGy。全数字化乳腺X射线摄影系统符合WS 522-2017《乳腺数字X射线摄影系统质量控制检测规范》要求,质量控制检测通过,设备运行良好。结论:通过对进行质量控制检测,可以客观地反映设备的性能,从而保证设备处于良好的运行状态。     

Individual doses for women undergoing screening mammography examinations in Poland in 2007

Exposure doses to women undergoing screening mammography examinations should be kept as low as reasonably achievable, but they should ensure high enough image quality for adequate diagnosis. The aim of this study was to estimate the radiation risk according to the 'European guidelines for quality assurance in breast cancer screening and diagnosis', fourth edition (European Commission 2006). Materials for this study were obtained from data from 250 screening mammography facilities in Poland. For every mammography facility, a standard average glandular dose for routine exposure was calculated. Furthermore, average glandular doses for individual mammography examinations obtained according to the methods proposed by Dance et al (2000 Phys. Med. Biol. 45 3225-40) were calculated. The average glandular doses determined for 250 mammography facilities ranged from 0.12 to 14.56 mGy (the mean values ranged from 0.62 to 4.53 mGy). Only for 39 mammography facilities were all exposures found to be below the acceptable level for an average glandular dose, and for only 18 mammography facilities did no exposures exceed the achievable levels for an average glandular dose. Average glandular doses to women undergoing mammography screening attained unnecessary high values, and they were found to depend on the technical parameters of the mammography equipment and maintenance of mammography units by personnel in various mammography facilities.     

Investigation of breast dose in five screening mammography centres in Greece

The objectives of this study were to investigate the techniques currently used for screening mammography in Greece, to estimate the mean glandular dose (MGD) for establishing a baseline radiation dose database, to analyse the effects of various factors on MGD, and to compare the results with others in the literature. Five mammographic facilities and 250 women having as a routine screening mammogram one craniocaudal (CC) and one mediolateral oblique (MLO) projection in each breast were included in the study. The parameters recorded were age, weight, compressed breast thickness (CBT), tube potential (kV), tube loading (mA s) and MLO projection angle. Large differences were observed among the different mammography facilities, mainly in terms of the tube potential setting and the MLO angle used. The average MGD per exposure was 1.4 +/- 0.6 mGy while the respective averages separately for the CC and MLO projections were 1.2 +/- 0.5 and 1.5 +/- 0.7 mGy, respectively. The average MGD values recorded in this study were below the limit of 2 mGy established for the reference medium-sized breast of 4.5 cm CBT. However, the variety of techniques observed revealed the need for a nationwide survey concerning screening mammography in Greece.     

利用管电流自动调节技术降低常规头部CT的照射剂量

目的 探讨常规头部CT采用管电流自动调节技术(即TCM螺旋扫描模式)能否降低照射剂量和提高影像质量。方法 50例成人患者,分别接受常规头部CT的TCM螺旋和常规轴扫模式,常规轴扫参数:140 kV,170mA用于颅底部;120 kV,150 mA用于颅脑部,2s/周。TCM螺旋扫描参数:120 kV,280 mA(最大管电流阈值),0.8 s/周。扫描剂量直接取自设备剂量指示值(CTDI和DLP)。影像质量分别由两位专家采用双盲法,对头部CT的颅底、脑灰-白质层面以及全部影像逐层进行CT值、信噪比测量以及综合评估。结果 常规头部CT采用TCM螺旋扫描模式较轴扫模式可使患者有效降低管电流使用量(44±12)mA,扫描时间(4.8±0.8)s,照射剂量(38±0.9)%:[CTDI:(32.10±9.0)mGy、(55.00±7.2)mGy;DLP(442.10±72)mGy·cm、(668.00±26)mGy·cm];经计算人体吸收剂量可降低(1.5±0.4)mSv,并可有效提高影像质量。结论 经两种不同扫描模式所得影像的CT值测量结果及其他影像质量参数的对照,应用TCM螺旋扫描模式的影像质量完全可与轴扫描模式相媲美,同时具有可减少扫描时间和照射剂量的优越性。     

不同阳极滤过器组合的乳腺DR成像性能对比

目的对数字乳腺X射线摄影不同阳极和滤过器组合成像性能进行对比。方法采用不同厚度乳腺成像体模、选择不同的阳极/滤过器组合,在自动曝光模式下成像。测量图像信噪比和腺体吸收剂量,并引入图像品质因数综合评价成像性能的好坏。结果对于不同厚度的乳腺体模,使用钨铑组合平均腺体剂量比其他组合可以降低25%~42%,图像品质因数高于其他组合5%~37%。随着腺体厚度的增加平均腺体吸收剂量逐步增加,而图像信噪比则与平均腺体吸收剂量成反比。结论当体模厚度在4~9cm时,钨铑组合成像性能最佳,因此在临床使用中应充分考虑临床实际需要来选择适宜成像技术,在保证临床图像质量的同时尽量降低受检者的辐射风险。     

仿真人体模型测量腹部CT受检者受照剂量研究

目的 通过仿真人体模型实验,针对现在所使用的腹部扫描条件,对患者的受照情况进行全面了解。方法 选择常规扫描参数和低剂量扫描参数,利用仿真人体模型,在相应体表位置和预定孔中插入剂量计,测量体表剂量和器官或组织的吸收剂量,并计算有效剂量。结果 常规剂量组和低剂量组的器官或组织的受照剂量范围分别为0.014~96.7 mGy,0.00148~5.56 mGy,有效剂量结果分别为14.5 mSv和1.52 mSv。结论 合理减少CT检查所致受检者剂量,需要建立科学实用的放射诊断的医疗照射参考(指导)水平。     

Radiation doses to patients from extracorporeal shock wave lithotripsy

The aim of this study was to determine the radiation doses to patients during extracorporeal shock wave lithotripsy (ESWL) and compare them with the available bibliographical data. In this method localization of the renal stones is attained by the use of fluoroscopy, and thus ESWL is included among those medical practices associated with patient radiation exposure. The entrance surface dose was measured using 3-4 thermoluminescent dosimeters positioned on the patients' backs at the entrance surfaces of the two x-ray beams for 50 ESWL procedures. Fluoroscopy time and number of spot films were also recorded. The average entrance surface dose at the patient's side with the renal stone was estimated to be 76.5 mGy for the oblique x-ray beam and 44.5 mGy for the PA x-ray beam. The mean fluoroscopy time was 204 s while 4 spot films were acquired on average. The mean effective dose (E) was estimated as 1.63 mSv per patient. The mean entrance surface dose values recorded in this study are comparable to but smaller than the values reported in the literature for ESWL, while the mean fluoroscopy time is within the range of values reported by other authors. On the other hand, the estimated E value is relatively higher compared to the corresponding values given in the literature based on patient measurements. However, it is comparable to recent published data acquired using extended measurements in an anthropomorphic phantom.     

Effective and organ doses using helical 4DCT for thoracic and abdominal therapies

The capacity of 4DCT to quantify organ motion is beyond conventional 3DCT capability. Local control could be improved. However we are unaware of any reports of organ dose measurements for helical 4DCT imaging. We therefore quantified the radiation doses for helical 4DCT imaging. Organ and tissue dose was measured for thoracic and abdominal 4DCT in helical mode using an adult anthropomorphic phantom. Radiation doses were measured with thermoluminescence dosimeter chips inserted at various anatomical sites on the phantom. For the helical thoracic 4DCT, organ doses were 57.2 mGy for the lung, 76.7 mGy for the thyroids, 48.1 mGy for the breasts, and 10.86 mGy for the colon. The effective doses for male and female phantoms were very similar, with a mean value of 33.1 mSv. For abdominal 4DCT imaging, organ doses were 14.4 mGy for the lung, 0.78 mGy for the thyroids, 9.83 mGy for breasts, and 58.2 mGy for the colon (all obtained by using ICRP 103). We quantified the radiation exposure for thoracic and abdominal helical 4DCT. The doses for helical 4DCT were approximately 1.5 times higher than those for cine 4DCT, however the stepwise image artifact was reduced. 4DCT imaging should be performed with care in order to minimize radiation exposure, but the advantages of 4DCT imaging mandates its incorporation into routine treatment protocols.     

乳腺DR成像普通模式和精细模式成像性能对比

目的对数字乳腺X射线摄影的两种不同曝光模式（精细模式和普通模式）成像性能进行评价。方法采用乳腺成像体模,选择不同的阳极滤过器组合,分别在两种自动曝光模式下成像,测量图像信噪比和腺体吸收剂量,并引入图像品质因数综合评价成像性能的好坏。结果精细模式图像信噪比要高于普通模式,但使腺体吸收剂量增加,因而品质因数低于普通模式。结论在临床使用中必须充分考虑临床实际需要来选择相应的成像技术,在保证临床图像质量的同时尽量降低受检者的辐射风险。     

胸部CR的低剂量投照条件及影像质量研究

目的：探讨降低胸部计算机X线摄影（CR）的辐射剂量并获得优良影像质量的投照条件。方法：采用不同的管电压（kVp）、管电量（mAs）、焦片距（FFD）,用自动曝光控制（AEC）方式对X线检测水模和体模曝光,探测体表空气照射量;测试空间分辨率和密度分辨率及灵敏度;用视觉观测和测量胶片密度方式评价人体胸部影像质量。结果：不同的管电压和胶片距与入射体表剂量（ESD）相关,管电压越高、胶片距越远,则ESD越低;一定范围内管电量的大小对影像分辨率没有影响,但对影像噪声有影响。低剂量CR胸部照片测试密度值及视觉评价效果达到了优良的影像密度和诊断学评价的要求。结论：胸部CR投照条件应用高电压120kVp、FFD为150cm、AEC减挡曝光及正确调节CR胸部影像处理参数,可有效降低受检者辐射剂量并获得优良的影像质量。     

不同水模体直径和不同重建层厚对CT图像噪声的影响

目的 研究不同水模体直径和重建层厚等因素对CT图像噪声的影响，探讨CT质量控制检测中水模体合理的直径范围，为完善我国CT质量控制检测规范提供数据支持。方法 采用GE公司的Revolution型CT机，在两档剂量水平，即CTDI_W分别为30.20 mGy（120 kV、200 mAs）和49.82 mGy（120 kV、330 mAs）、图像重建层厚为5 mm和10 mm的条件下，分别对直径为16、18、20、22、24 cm的圆柱型均质水模体轴向扫描一圈，测量其CT值（水）和噪声等指标。比较不同水模体直径、不同层厚和不同剂量等条件下噪声测量值的差异。结果 噪声测量值随水模体直径增大而增大，随剂量增大而减小，在大小两档剂量水平下水模体直径分别为24、22 cm时的噪声值已超过现有检测标准；噪声随重建层厚的增大而减小。结论 噪声的测量结果与剂量、水模体直径、重建层厚等因素有关，在进行CT质量控制噪声项目的检测时，需规定所选择的剂量水平和层厚大小，并规定所选择水模体的直径大小。本研究结果提示CTDI_W在接近50 mGy的条件下，18~22 cm可能是比较合理的水模体直径范围。     

X线乳腺摄影受检者腺体平均剂量水平调查

目的调查河北省内部分医院乳腺x线机受检者腺体平均剂量水平,比较普通增感屏／胶片机,计算机x线摄影（CR）,数字放射线摄影（DR）及不同压迫厚度乳腺腺体平均剂量水平的差异。方法乳腺腺体平均剂量测量采用VictoreenNEROTMmax系统主机（美国Cardinal Health公司）及Victoreen6000—529乳腺电离室（美国FLUKE公司）。结果3种乳腺X线机在实际诊断工作中,钼靶屏／片机剂量平均值为（0．74±0．23）mGy,CR与DR剂量平均值分别为（1．60±1．02）与（1．69±0．80）mGy,受检者腺体平均剂量水平钼靶屏／片机低于CR及DR,其差异有统计学意义（P〈0．05）。对CR与DR受检者腺体平均剂量进行。检验,P值为0．35,差异无统计学意义。随着乳房压迫厚度的增加,腺体平均剂量水平有所增加,但差异无统计学意义（P〉0．05）。结论在医师操作熟练、设备保养得当的情况下,乳腺X线钼靶屏／片机可以满足一般患者诊断要求,中小型医院或经济欠发达地区医院可以使用钼靶屏／片X线