上海市质子重离子医院临床实践中放射治疗师的职业照射水平评估

目的 评估上海市质子重离子医院质子重离子临床实践过程中,放射治疗师的职业照射水平。方法 通过简单随机抽样方法选取2016年9-11月治疗的40例患者,其中接受质子和重离子治疗各20例。记录每个患者的粒子类型、粒子总数、处方剂量。利用光子/中子辐射剂量仪分别测量出束过程中控制室内剂量率、出束结束1 min后距肿瘤最近的皮肤处剂量率、距肿瘤约30 cm处（治疗师立位处）的剂量率;最后测量固定装置、床、机械臂、束流应用及监测系统（BAMS）窗口处的剂量率。分析影响治疗师的职业照射水平的因素,评估该院治疗师的年平均剂量。结果 治疗结束约1 min后,距肿瘤最近的皮肤处剂量率为（20.68±21.91）μSv/h,此处是各测量点位中剂量率最大的点位,且与治疗用的粒子总数呈显著正相关（r=0.828,P<0.05）,受质子或重离子照射后的肿瘤是本研究中治疗师职业照射的辐射源;距肿瘤约30 cm处（治疗师立位处）的平均剂量率为（2.03±2.84）μSv/h;控制室内剂量率为（0.08±0.01）μSv/h,患者的固定装置、床、机械臂、BAMS窗口处的剂量率为（0.09±0.01）μSv/h;未检测到中子,放疗师受到的年平均剂量为0.508 mSv。结论 上海市质子重离子医院放射治疗师受到的年平均剂量处于较低水平。     

以通识课程形式推动高校学生辐射安全知识普及的探索与实践

目的 通过调查问卷方式,评价通识课程《辐射防护基础》在构建与强化高校学生辐射安全意识过程中的实施效果,为提高大学生健康素养,培养知识结构合理、实践能力强的创新型人才提供新的策略。方法 2021—2022年度山东大学各学院选修通识课程《辐射防护基础》本科生总人数为127人,为对比医学、非医学专业学生学习效果,选取医学院、电气工程学院选课学生101人(79.5%)作为参与者,通过问卷调查对比分析课程学习前后大学生对辐射安全基本概念及理论的了解,以及对辐射危害科学防护意识的改变,从而评价该课程教学效果及意义。结果 2021—2022年度山东大学医学院与电气工程学院参加课程学习的学生中,接受邀请并全程自愿完成两次问卷调查的94人,占各校区总选课人数74.0%。调查结果显示:通过课程学习,明显提高了大学生对辐射科学防护的认知水平,对6个方面的认知李克特量化分值从学习前的3.59±1.35、3.81±1.17、3.45±1.16、4.11±1.13、3.62±1.05、3.98±1.24分别增加到学习后的4.94±0.32、4.87±0.32、4.96±0.21、4.98±0.15、4.81±0.39、4.98±0.15,差异均具有统计学意义(t=6.55、5.50、9.10、5.36、7.60、5.34,P< 0.05)。进一步分析发现不同专业背景影响学生对辐射安全防护的了解:在学习本课程前,对电离辐射5个方面知识认知评分,医学院学生优于电气工程学院学生,差异有统计学意义(t=5.69、4.06、6.46、6.27、7.78,P< 0.001);而学习本课程后,两个专业学生对该问题的认知程度均明显提升,无明显差异(P > 0.05)。对课程学习收获的反馈结果显示:通过通识课程学习方式,可以明显提高"日常辐射防护"意识(96.8%),鉴别伪科学、伪信息(93.6%),打消对"核"的恐惧(95.7%),并有效引导他们树立"珍爱生命"的观念(91.5%)。结论 《辐射防护基础》通识课程有效提升了学生的辐射安全意识,强化了辐射安全防护知识体系,为培养知识结构合理的创新型人才提供新的途径,值得在不同背景不同专业的大学生课程教育中进一步推广应用。     

Dual-source computed tomography: Estimation of radiation exposure of ECG-gated and ECG-triggered coronary angiography

Purpose

The aim of the study was to estimate radiation exposure of coronary calcium scoring and angiography using ECG-gated and ECG-triggered dual-source computed tomography.

Materials and methods

An Alderson Rando phantom equipped with thermoluminescent dosimeters was used for all dose measurements. Effective dose was calculated according to ICRP 103. Radiation exposure was performed on a dual-source computed tomography (DSCT) scanner with standard protocols for calcium scoring (DSCT-Ca) and coronary angiography (DSCTA) at different heart rates (40-100 beats/min). Furthermore, a scanning protocol with ECG-triggering as well as a standard chest CT scan were evaluated.

Results

Depending on gender, heart rate and ECG-pulsing, the effective dose of a complete cardiac DSCT (DSCT-Ca and DSCTA) scan varies from 10.2 to 32.6 mSv. The effective radiation dose increased significantly with lower heart rates (p < 0.035). ECG-pulsing reduced the radiation exposure significantly in DSCTA (p < 0.001). Due to breast tissue in the primary scan range, females’ doses showed an increase up to 69.9% compared to males in scan protocols without ECG-pulsing. Prospective ECG-triggered DSCTA resulted in estimated effective doses from 2.8 mSv (males) to 4.1 mSv (females).

Conclusion

The ECG-pulsing technique has proven its effectiveness to reduce effective dose in coronary CT angiography and is recommended for all patients with regular heart rates. The patient's heart rate influences the radiation exposure with a significant decrease at higher heart rates. Due to its lower dose, ECG-triggered DSCTA should be implemented for special indications, i.e. for diagnosis of pathologies of the aortic root and the ascending aorta.     

Repeated CT scans in trauma transfers: An analysis of indications,radiation dose exposure,and costs

ObjectivesTo identify the number of CT scans repeated in acute trauma patients receiving imaging before being referred to a trauma center, to define indications, and to assess radiation doses and costs of repeated CT.MethodsThis retrospective study included all adult trauma patients transferred from other hospitals to a Level-I trauma center during 2014. Indications for repeated CT scans were categorized into: inadequate CT image data transfer, poor image quality, repetition of head CT after head injury together with completion to whole-body CT (WBCT), and follow-up of injury known from previous CT. Radiation doses from repeated CT were determined; costs were calculated using a nation-wide fee schedule.ResultsWithin one year, 85/298 (28.5%) trauma patients were transferred from another hospital because of severe head injury (n = 45,53%) and major body trauma (n = 23;27%) not manageable in the referring hospital, repatriation from a foreign country (n = 14;16.5%), and no ICU-capacity (n = 3;3.5%). Of these 85 patients, 74 (87%) had repeated CT in our center because of inadequate CT data transfer (n = 29;39%), repetition of head CT with completion to WBCT (n = 24;32.5%), and follow-up of known injury (n = 21;28.5%). None occurred because of poor image quality. Cumulative dose length product (DLP) and annual costs of potential preventable, repeated CT (inadequate data transfer) was 631mSv (81′304mGy*cm) and 35′233€, respectively.ConclusionA considerable number of transferred trauma patients undergo potentially preventable, repeated CT, adding radiation dose to patients and costs to the health care system.     

A snapshot of patients' awareness of radiation dose and risks associated with medical imaging examinations at an Australian radiology clinic

BackgroundCumulative radiation exposure is linked to increasing the lifetime attributable risk of cancer. To avoid unnecessary radiation exposure and facilitate shared decision making, patients should be aware of these issues. This paper examines patients' awareness of radiation dose and risks associated with medical imaging examinations.MethodsConsecutive patients attending a private radiology clinic over a nine week period in 2014 in Metropolitan Melbourne were surveyed while waiting to undergo an imaging examination. Patients who were under 18 years of age, did not speak English and/or were referred for interventional imaging procedures were excluded from participation. Survey questions addressed patients' awareness of radiation dose associated with various imaging modalities' and patients' experience and preferences regarding communication of information about radiation. Data was analysed using SPSS (Ver 20.1).ResultsA total of 242 surveys were completed. Most participants were male (143/239, 59.8%) and aged between 33 and 52 years (109/242, 45%). Over half of participants were not concerned about radiation from medical imaging (130/238, 54.6%). Only a third of participants (80/234, 34.2%) correctly reported that CT has a higher radiation dose than X-ray. Very few participants correctly identified mammography, DEXA, PET and PET/CT as radiation emitting examinations. The majority of participants (202/236, 85.6%) indicated that they were not informed about radiation dose and risks by their referring doctor in advance.ConclusionThis paper provides information relevant to a single private radiology clinic in Australia. Nevertheless, our results have shown that patients presenting for medical imaging have little awareness of radiation dose and risks associated with these examinations and received little information by their referring physicians or staff at the radiology clinic.     

Dual-energy, standard and low-kVp contrast-enhanced CT-cholangiography: a comparative analysis of image quality and radiation exposure

Objective

Quantitative image quality assessment in terms of image noise (IN), contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR) in relation to required radiation dose (RD) for dual-energy (DE), standard and low-kVp contrast-enhanced computed-tomography (CT) cholangiography.

Materials and methods

For each of 22 DECT-cholangiography examinations, 3 image datasets were analyzed as independent single-source CT-acquisitions at different tube potential, i.e. 80 kVp, 120 kVp-equivalent (linear blended dataset M0.3: 30% 80 kVp, 70% 140 kVp), and 140 kVp. Analysis comprised determination of IN, CNR and SNR in regions of interest (ROI) placed in liver parenchyma and contrasted bile ducts. IN was evaluated as mean standard deviation of 3 ROI placed within liver parenchyma (segments 6/7, 5/8, 2/3); CNR was assessed as bile duct-to-liver parenchyma ratio, and SNR as bile duct-to-image noise ratio. RD in terms of CT dose index (CTDI_vol), dose-length product (DLP) and effective dose (ED) has been determined for each of the datasets, and compared to console prediction and scan summary values. Using phantom measurements of CTDI_vol, a method for separating comprehensive RD values of DE-acquisitions into the original RD contribution of each tube (80 kVp/140 kVp) has been developed, enabling comparison of all 3 datasets as if independently acquired using single-source “single-energy” technique.

Results

Highest IN was detected for 80 kVp- (38.6 ± 5.1 HU), lowest for 120 kVp-equivalent linear blended M0.3-datasets (23.1 ± 3.4 HU) with significant differences between all datasets (P < 0.001). Highest SNR and CNR were measured for M0.3- (SNR: 14.8 ± 4.1; CNR: 11.6 ± 3.8) and 80 kVp-datasets (SNR: 13.8 ± 4.8; CNR: 11.2 ± 4.5); lowest for 140 kVp-datasets (SNR: 9.5 ± 2.5; CNR: 7.1 ± 2.3) with significant differences between M0.3- and 140 kVp-datasets as well as between 80 kVp- and 140kVp-datasets (both P < 0.001 for both CNR, SNR). CTDI_vol, DLP and ED were reduced by 50% for low-kilovoltage acquisitions (CTDI_vol: 5.5 ± 1.4 mGy; DLP: 127.8 ± 40.1 mGy cm; ED: 1.9 ± 0.6 mSv) compared to comprehensive DE-acquisitions (CTDI_vol: 11.0 ± 2.3 mGy; DLP: 253.8 ± 67.5 mGy cm; ED: 3.8 ± 1.0 mSv, tube contribution: 80 kVp: 44.5%; 140 kVp: 55.5%), and by 20% compared to conventional acquisitions at 120 kVp (CTDI_vol: 6.71 mGy; DLP: 153.5 ± 16.9 mGy cm; ED: 2.3 ± 0.3 mSv).

Conclusions

Despite higher IN, low-kilovoltage CT-cholangiography reveals no significant difference with respect to CNR and SNR when compared to linear blended images yielded by DECT. Compared to DECT or conventional CT at 120 kVp, contrast-enhanced low-kVp CT cholangiography potentially allows reduction of patient dose by up to 50% or 20%, respectively. Therefore, CT-cholangiography at 80 kVp should be considered as an alternative to DECT-cholangiography whenever DECT is unavailable, or if increased image quality of DECT regarding quantitative bile duct evaluation is not needed for diagnosis.     

ALARA and paediatric imaging in radiation therapy: A survey of Canadian paediatric imaging practice

PurposeThere is little discussion in the literature regarding paediatric imaging dose reduction with respect to conventional imaging carried out in radiotherapy departments. This is in contrast to diagnostic radiography where dose optimization when imaging children is a very current topic. For this reason Canadian radiotherapy clinics were surveyed to look at paediatric imaging practice, knowledge and perspectives with respect to imaging dose reduction.MethodAs this was an exploratory study, a questionnaire was developed and sent to radiation therapy clinics across Canada, via email, to assess knowledge of paediatric imaging and dose reduction initiatives. The questionnaire focus was CT simulation and treatment verification imaging of children.ResultsPractice and knowledge of paediatric imaging varied across Canada. Forty percent of clinics reported using paediatric specific protocols for CT simulation and 20% of clinics reported using paediatric specific protocols for treatment verification imaging. There was variation in imaging practices among the clinics that reported treating the most children. The survey results show that while some measures are being taken to reduce paediatric imaging dose in radiation therapy, 46.7% of the respondents felt more could be done.ConclusionThe survey demonstrates interest in dose reduction in radiation therapy imaging as well as differences in current practice and knowledge across Canada. Paediatric imaging dose reduction would appear to be an area of practice that would benefit from more study and development of standards of practice.     

A narrative review of e-learning in professional education of healthcare professionals in medical imaging and radiation therapy

ObjectivesThis literature review attempts to explore the characteristics of e-learning tools used to develop the qualifications and skills of healthcare professionals in medical imaging and radiation therapy, and to promote the effectiveness and acceptance of e-learning through highlighting the outcomes of its implementation where applicable.Key findingsFrom the literature search in the PubMed and ResearchGate databases we concluded to 21 articles, which were included in the qualitative synthesis. Acceptance of e-learning tools was confirmed. Also, e-learning can be part of healthcare professionals' blended learning. The acquisition of new or improvement of existing knowledge, the improvement of clinical skills and the increase of the self-confidence of healthcare professionals in their daily practice were recorded, as outcomes of the e-learning implementation. The importance of human–computer interaction for the comprehension of theoretical concepts and practical aspects using multimedia was also captured. No significant findings emerged among the 21 articles against the adoption of the e-learning for the training of healthcare professionals. The Internet is the channel used for synchronous and asynchronous interaction of trainees with instructors.ConclusionsWe concluded that e-learning is an attractive training method, equally or occasionally more effective than the traditional educational methods for the lifelong training of healthcare professionals in the field of medical imaging and radiation therapy. Also, many collaborative web-based applications provide the necessary means to build an e-learning program, according to the training needs of each professional team.Implications for practiceThis new knowledge corroborates the perspective of e-learning beneficial contribution to remote interaction and collaboration of healthcare professionals in medical imaging and radiation therapy. Collaborative web-based tools are already available to decision makers and stakeholders, who want to develop an e-learning program.     

An assessment of Sri Lankan radiographer's knowledge and awareness of radiation protection and imaging parameters related to patient dose and image quality in computed tomography (CT)

IntroductionAs computed tomography (CT) examinations have considerably risen, safe operation is essential to reduce the patients’ dose. The main objective of this study was to evaluate the level of knowledge and awareness regarding the CT exposure parameters and radiation protection in CT imaging among Sri Lankan radiographers.MethodsAn online survey-based study was devised and distributed among the Sri Lankan CT radiographers working in 63 CT units. Questions were divided into three subsections that collected data on the participants’ demographic features, knowledge of the radiation protection, and imaging parameters.ResultsEighty-eight radiographers from 32 CT units (out of 63 CT units) distributed across 11 districts (out of 27 districts) participated in this survey.The percentages of correct responses for the questions related to radiation protection, imaging parameters, noise, Diagnostic Reference Level (DRL), and CT dosimetric parameters were 71%, 79%, 87%, 50%, and 66%, respectively. Although the years of experience did not influence any of above aspects, the level of education significantly impacted the knowledge about radiation protection, exposure parameters, and noise.ConclusionThe radiographer's knowledge of radiation protection and most imaging parameters associated with patient safety and image quality is satisfactory. However, findings also show that participants should fill the knowledge gap in radiation-related risks, CT exposure parameters, dosimetric parameters, and DRL.Implications for practiceThe study suggests the necessity of initiating continuous education programs for radiographers in line with national radiation protection legislation requirements that can be linked with code of practice.     

酰胺质子转移成像与DWI诊断宫颈鳞癌并评估其分级的对比研究

目的:对比分析酰胺质子转移成像(APT)与扩散加权成像(DWI)在诊断宫颈鳞癌并评估其分级中的价值。方法:回顾性分析50例宫颈癌患者的临床及APT、DWI资料,根据病理类型分为腺癌组(n=11)与鳞癌组(n=39),并根据病理分级将鳞癌组分为低分化组(n=12)与高中分化组(n=27),测量宫颈癌组织的不对称性磁化转移率(MTR asym)、平均ADC值、最小ADC值,分别比较宫颈腺癌组与鳞癌组、宫颈鳞癌高中分化组与低分化组各参数值的差异,采用ROC曲线评价各参数值的诊断效能及最佳诊断阈值,并根据约登指数确定各参数相应的诊断敏感度、特异度。结果:宫颈鳞癌组MTR asym[(3.03±0.06)%]低于宫颈腺癌组[(3.12±0.05)%],平均ADC值、最小ADC值[(0.94±0.03)×10^-3 mm^2/s、(0.85±0.03)×10^-3 mm^2/s]低于宫颈腺癌组[(0.98±0.03)×10^-3 mm^2/s、(0.88±0.03)×10^-3 mm^2/s],差异均具有统计学意义(t=4.35、3.66、3.55,P值均<0.05);低分化宫颈鳞癌组MTR asym值[(3.08±0.03)%]高于高中分化鳞癌组[(3.00±0.05)%],平均ADC值、最小ADC值[(0.92±0.02)×10^-3 mm^2/s、(0.82±0.02)×10^-3 mm^2/s]低于高中分化鳞癌组[(0.95±0.03)×10^-3 mm^2/s、(0.86±0.02)×10^-3 mm^2/s],差异均具有统计学意义(t=5.37、2.55、4.08,P值均<0.05);在诊断宫颈鳞癌及低分化宫颈鳞癌时,MTR asym均有最佳诊断效能,ROC曲线下面积分别为0.865、0.932,以MTR asym=3.08%、3.06%为阈值,诊断敏感度分别为79.5%、85.2%,特异度分别为81.8%、83.3%。结论:与DWI相比,APT在诊断宫颈鳞癌并评估宫颈鳞癌分级中更具优势。     

Impact of image noise levels, scout scan dose and lens shield on image quality and radiation exposure in z-axis dose-modulated neck MSCT on 16- and 64-slice Toshiba Aquilion scanners

Objective

Assessing the impact of image noise (IN) levels, scout scan dose and lens shield use on image quality and radiation exposure in neck multislice CT (MSCT) when using z-axis dose modulation (DM).

Methods

Neck MSCT phantom studies with/without z-axis DM were performed by using different IN levels (S.D. 7.5-30 HU) and scout scan tube currents (7.5-50 mA) on Toshiba Aquilion scanners (16-/64-slice). Image quality indices were evaluated by two radiologists and radiation exposure parameters calculated. Cadaveric phantom measurements elucidated lens shield interactions with DM efficacy. The lowest dose scan protocol with diagnostic image quality was introduced into the clinical imaging routine and retrospectively evaluated in 20 age-matched patients undergoing neck MSCT with/without DM.

Results

The highest image noise level in DM neck studies with comparable image quality to standard neck CT amounted to 20 HU, resulting in a mean tube current of 50 mAs (CTDI_w 6.3 mGy). DM reduced effective dose by 35% and organ dose figures (lens, thyroid) by 33%. Scout scan dose lowering to 20 mA resulted in an effective dose (ED) decrease of 0.06 mSv (5%). Avoiding lens shield placement during scout scan effected an organ dose decrease of 20%. Overall contour sharpness and image contrast did not differ significantly (DM/without DM) whereas image noise was rated higher in DM neck CT studies (p < 0.05).

Conclusions

z-Axis dose modulation, as assessed on 16- and 64-slice Toshiba Aquilion scanners, is effective and mandatory in neck MSCT. DM efficacy can be enhanced by optimising scout scan doses and lens shield use.     

Mapping very low level occupational exposure in medical imaging: A useful tool in risk communication and decision making

Objectives

The use of ionising radiation in medical imaging is accompanied with occupational exposure which should be limited by optimised room design and safety instructions. These measures can however not prevent that workers are exposed to instantaneous dose rates, e.g. the residual exposure through shielding or the exposure of discharged nuclear medicine patients. The latter elements are often questioned by workers and detailed assessment should give more information about the impact on the individual radiation dose.

Methods

Cumulated radiation exposure was measured in a university hospital during a period of 6 months by means of thermoluminescent dosimeters. Radiation exposure was measured at background locations and at locations where enhanced exposure levels are expected but where the impact on the individual exposure is unclear.

Results

The results show a normal distribution of the cumulated background radiation level. No enhanced cumulated radiation exposure which significantly differs from this background level could be found during the operation of intra-oral apparatus, during ultrasonography procedures among nuclear medicine patients and at operator consoles of most CT-rooms.

Conclusions

This 6 months survey offers useful information about occupational low level exposure in medical imaging and the findings can be useful in both risk communication and decision making.     

Assessment of the awareness of radiation protection and related concepts among nursing staff mainly working in diagnostic imaging units,cath-labs and operation theatres in Sri Lanka: A survey-based study

IntroductionThis study was carried out to evaluate the awareness of radiation protection, radiation types, medical imaging equipment and radiation effects among nurses for the first time in Sri Lanka. Since nurses are involved as direct caregivers in diagnostic and therapeutic radiography and radiation treatment procedures, they need to have a good understanding of the areas mentioned above.MethodsA self-administered questionnaire was used to collect data from 391 nurses working in hospitals, clinics, and other healthcare settings. Forwarded questions gathered the participants' demographic details and assessed their awareness of radiation protection, medical imaging equipment, radiation type and radiation effects. The average score per awareness area for each demographic characteristic was calculated based on the responses. Additionally, the percentage of participants who scored above 50 and 75 was calculated for each awareness area.ResultsThe majority were female participants (81.1%) and possessed a diploma in nursing (66.0%) with 10.8 years of average work experience. 92.3%, 74.7%, 69.8% and 22.3% of the participants scored more than 50 marks for the questions related to radiation protection, medical imaging equipment, radiation type and radiation effects, respectively. The level of nursing education and prior training in radiation protection significantly influenced all awareness areas, whereas participants with a graduate qualification in nursing and with prior radiation protection training scored the highest average marks.ConclusionBased on the scores obtained, the Sri Lankan nurses have satisfactory awareness of the essential concepts related to radiation types, medical imaging equipment and radiation protection. However, there is a significant lacking of awareness of radiation effects. This can be attributed to the fact that most participants did not have any formal training in radiation protection. The results implicate that proper training in radiation protection can significantly influence awareness of radiation protection and related concepts. Therefore, it is a timely requirement to initiate short awareness programs and continuing education programs on radiation protection for nurses working in specialised radiation units.Implications for practiceThe study suggests the necessity of initiating continuous education programs for nursing staff radiation protection to overcome the awareness gaps.     

MR积分法与灌注成像在脑胶质瘤中的对照研究

目的比较MR积分法与灌注成像在脑胶质瘤术前分级诊断中的价值。方法对30例脑胶质瘤(低级8例,高级22例,世界卫生组织分级)术前行MR常规及灌注成像检查。MR积分法使用9个指标进行评价,灌注指标相对脑血容量(rCBV)由肿瘤及对侧正常脑白质的脑血容量(CBV)相比后得出。分别对低级、Ⅲ级和Ⅳ级胶质瘤的积分及rCBV值进行分析。结果低级胶质瘤的积分值(067±029)显著低于Ⅲ级(132±047)(t=-348,P=0003)和Ⅳ级(156±020)(t=-736,P=0000)。Ⅲ级和Ⅳ级之间差异无统计学意义(t=-139,P=0182)。低级胶质瘤的rCBV值(238±066)显著低于Ⅲ级(581±320)(t=-357,P=0003)和Ⅳ级(699±247)(t=-509,P=0001)。Ⅲ级和Ⅳ级之间差异无统计学意义(t=-093,P=0365)。结论在脑胶质瘤术前分级诊断中,常规MR和灌注成像均有重要价值,可相互补充,提高诊断准确率。     

胸部能谱成像模式与常规CT扫描的辐射剂量及图像质量的仿真体模研究

目的 通过仿真胸部体模研究胸部能谱CT不同方案成像模式与常规胸部CT扫描的辐射剂量、图像质量、对比噪声比及主观评分对比,获得最佳能谱扫描参数。方法 对仿真胸部体模分别进行常规胸部CT扫描以及3种不同扫描方式的能谱CT成像。3种能谱模式为宝石能谱CT （GSI）Assist模式（方案A）、管电流平均值时的GSI模式（方案B）及管电流最大值时的GSI模式（方案C）。所有扫描方式分别在噪声指数（NI）=9和11时,螺距0.984∶1,依次扫描。记录辐射剂量,同时测量感兴趣区（ROIs）5个不同层面水平的脂肪和肌肉组织的图像噪声值（SD）以评价图像质量。所有扫描序列由两位资深放射医师对肺窗肺纹理及分支5分制主观评分。结果 NI=9和11时,常规CT平扫与方案A、B、C的有效剂量（E）值分别为（8.0、8.5、6.2、10.4）和（5.3、5.1、4.3、6.2）mSv。NI=9时,常规胸部CT平扫与方案A、C的SD值差异有统计学意义（F=4.496,P<0.05）;NI=11时,方案A、B、C与常规胸部CT平扫SD值差异有统计学意义（F=8.425,P<0.05）;常规胸部CT扫描中,NI分别为9和11时SD值差异有统计学意义（t=－2.570,P<0.05）;在相同能谱扫描模式中,NI不同,SD值差异均无统计学意义（P>0.05）。NI相同扫描模式不同及扫描模式相同NI不同时,CNR及主观评分差异均无统计学意义（P>0.05）。结论 合理的能谱扫描模式与常规扫描的辐射剂量没有明显差异,但能谱扫描模式可以获得较高的图像质量。此外,选择合适的噪声指数在图像质量相仿的同时可以明显降低辐射剂量。综合辐射剂量及图像质量,能谱CT智能模式可以达到辐射剂量及图像质量的双向平衡。     

原发性青光眼患者双侧视放射及视皮质的磁化传递成像

目的 应用磁化传递成像(MTI)研究原发性青光眼患者双侧视放射、视皮质的异常,探讨青光眼性损伤对后视路的影响.方法 选取20例常规颅脑MR检查无异常的原发性青光眼患者(青光眼组)及31名正常志愿者(对照组)行MTI检查,采用扰相梯度回波序列(SPGR)成像,分别于施加磁化传递饱和脉冲前后进行扫描.将扫描图像进行后处理分析,测量双侧视放射及视皮质的磁化传递率(MTR).组间各部位MTR值的比较采用两样本t检验(方差不齐则采用Satterthwaite近似t检验).结果 青光眼组左、右两侧视放射的MTR值分别为(32.8±2.2)％、(32.7±2.0)％,对照组相应部位MTR值分别为(34.6±1.4)％、(34.8±1.3)％,青光眼组低于对照组,差异有统计学意义(左侧t=3.284,右侧t=4.040;P值均＜0.01).青光眼组左、右两侧视皮质的MTR值分别为(30.1±2.0)％、(30.8±1.8)％,对照组相应部位MTR值分别为(32.3±1.2)％、(32.4±1.2)％,青光眼组低于对照组,差异也有统计学意义(左侧t =4.319,右侧t=3.445;P值均＜0.01).结论 青光眼患者后视路发生了潜在神经病理学变化,提示青光眼是累及全视路的病变.MTI能在肉眼可见的影像学改变之前提供微观病理方面的信息,是活体人青光眼视觉通路跨突触损害研究的有用方法,也为青光眼临床诊治及评估预后提供了新的思路.     

正常脑池段后组脑神经及相关动脉MRI与断层标本解剖的对比研究

目的获得正常人脑池段后组脑神经及相关动脉血管的MRI和断层解剖资料。方法对59名正常体检者进行三维（3D）积极干预稳态（3D-CISS）序列扫描、多平面重组（MPR）成像，其中22名同时行3D-时间飞跃法（TOF）脑干区血管成像。对这些受检者脑池段后组脑神经的走行和神经血管位置关系进行显示，并将脑池段后组脑神经MRI结果与5具尸体脑断层切片、尸体脑3D-CISS结果进行对照分析。结果（1）显示概率：59名正常体检者脑池段舌咽、迷走、副复合体神经在斜横断面、斜矢状面重组图像上分别以100％（118／118）、99％（117／118）的概率清晰显示；舌下神经在斜横断面、斜矢状面重组图像上分别以90％（106／118）、91％（107／118）的概率清晰显示；3D-TOF序列成像不能清晰显示后组脑神经。（2）神经走行显示：59名正常体检者的双侧舌咽、迷走、副复合体神经均从橄榄后沟发出，自上而下依次为舌咽、迷走、副神经；颈静脉孔为舌咽、迷走、副复合体神经出现的标志层面；45％（53／118）的舌咽、迷走、副神经呈分离平行状走行，55％（65／118）三者呈聚拢状走行；舌下神经从延髓前外侧沟出延髓，舌下神经管为舌下神经出现的标志层面。（3）3D-CISS序列MR影像：椎动脉（VA）是显示率较高的动脉，72％（85／118）的VA与后组脑神经无接触；28％（33／118）的VA与后组脑神经接触。（4）将脑池段后组脑神经成像结果与尸体3D-CISSMRI、断层切片标本进行对照，显示良好的对应关系。结论3D-CISS MRI可以清晰显示脑池段后组脑神经及相关动脉血管。     

Compliance to Diagnostic Reference Levels for radiation exposure in common radiological procedures in Dutch hospitals: A nation-wide survey carried out by medical imaging students

IntroductionIn the Netherlands, hospitals have difficulty in implementing the formal procedure of comparing radiation dose values to Diagnostic Reference Levels (DRLs).MethodsTo support the hospitals, train radiography students, and carry out a nationwide dose survey, diagnostic radiography students performed 125 DRL comparisons for nine different procedures in 29 radiology departments. Students were instructed at three Dutch Universities of Applied Sciences with a radiography programme and supervised by medical physicists from the participating hospitals.ResultsAfter a pilot study in the western part of the country in eight hospitals, this study was enlarged to involve 21 hospitals from all over the Netherlands. The 86 obtained dose comparisons fall below the DRLs in 97% of all cases. This very high compliance may have been enhanced by the voluntary participation of hospitals that are confident about their performance.ConclusionThe results indicate that the current DRLs that were not based on a national survey, may need to be updated, sometimes to half their current value. For chest and pelvis examinations the DRLs could be lowered from 12 and 300 μGy·m² to the 75-percentile values found in this study of 5,9 and 188 μGy·m², respectively.