Conversion factors for effective dose and organ doses with the air kerma area product in patients undergoing percutaneous transhepatic biliary drainage and trans arterial chemoembolization

Conversion factors used to estimate effective (E) and organ doses (H_T) from air Kerma area product (KAP) are required to estimate population doses in percutaneous transhepatic biliary drainage (PTBD) and trans arterial chemoembolization (TACE) interventional procedures.In this study, E and H_T for ten critical organs/tissues, were derived in 64 PTBD and 48 TACE procedures and in 14,540 irradiation events from dosimetric, technical and geometrical information included in the radiation dose structured report using the PCXMC Monte Carlo model, and the ICRP 103 organ weighting factors. Conversion factors of: 0.13; 0.19; 0.26 and 0.32 mSv Gy⁻¹ cm⁻² were established for irradiation events characterized by a Cu filtration of 0.0; 0.1; 0.4 and 0.9 mm, respectively. While a single coefficient of conversion is not able to provide estimates of E with enough accuracy, a high agreement is obtained between E estimated through Monte Carlo methods and E estimated through E/KAP conversion factors accounting separately for the different modes of fluoroscopy and the fluorography component of the procedures.An algorithm for the estimation of effective and organ doses from KAP has been established in biliary procedures which considers the Cu filtration in the X-ray irradiation events. A similar algorithm could be easily extended to other interventional procedures and incorporated in radiation dose monitoring systems to provide dosimetric estimates automatically with enough accuracy to assess population doses.     

Estimation of size-specific dose estimates (SSDE) for paediatric and adults patients based on a single slice

Volume averaged CT dose index (CTDI_vol) is an important dose index utilized for CT dosimetry. Measurements of CTDI_vol are performed in reference cylindrical phantoms of specified diameters. A size-specific dose estimate (SSDE) has been recommended for assessment of doses delivered to individual patients. Evaluation of the SSDE requires the size of the scanned region of the patient to be estimated in terms of water-equivalent diameter (D_w) to allow calculation of a dose value appropriate for the patient. Estimation of D_w, however, may be challenging and time consuming as it requires assessment of D_w for each slice within the scanned region. A study has been carried out to investigate the suitability of using D_w,mid for a single slice at the middle of the scanned region to estimate a value of D_w,mean to apply to all slices. 351 phantoms (158 paediatric and 193 adult) developed from reconstructed CT images of patients were employed. Six scan regions were studied: chest, abdomen, pelvis, chest and abdomen, abdomen and pelvis, and the whole trunk. Results show that the use of D_w,mid can lead to over or underestimation of D_w,mean by up to 13% for paediatric and adult patients. SSDE values based on D_w,mid and D_w,mean were assessed for each phantom, and a linear regression analysis was performed. Use of the analysis could provide a simple and practical approach to assessing SSDE for a given scan based on D_w,mid with the root-mean-square errors estimated to be in the range of 1.2%–4.0% for paediatric and 1.2%–5.9% for adults.     

Dendroclimatic potential of dendroanatomy in temperature-sensitive Pinus sylvestris

The most frequently and successfully used tree-ring parameters for the study of temperature variations are ring width and maximum latewood density (MXD). MXD is preferred over ring width due to a more prominent association with temperature. In this study we explore the dendroclimate potential of dendroanatomy based on the first truly well replicated dataset. Twenty-nine mature living Pinus sylvestris trees were sampled in North-eastern Finland at the cool and moist boreal forest zone, close to the latitudinal tree line, where ring width, X-ray MXD as well as the blue intensity counterpart MXBI were compared with dendroanatomical parameters. Maximum radial cell wall thickness as well as anatomical MXD and latewood density appeared to be the most promising parameters for temperature reconstruction. In fact, these parameters compare favorably to MXD derived from X-ray techniques as well as MXBI, in terms of shared variation and temperature correlations across frequencies and over time. The reasons for these results are thought to be the unprecedentedly high measurement resolution of the anatomical technique, which provide the optimal resolution – the cell – whereas X-ray techniques have a slightly lower resolution and BI techniques even lower. While the results of this study are encouraging, further tests on longer and multigenerational chronologies are required to more generally and fully assess the dendroclimate potential of anatomical parameters.     

CBCT引导放疗摆位误差对中上段食管癌患者受照射剂量的影响

摘要 目的：探究锥形束CT（CBCT）引导放疗摆位误差对中上段食管癌患者受照射剂量的影响。方法：选取2017年5月～2019年5月于我院收治的60例中上段食管癌患者为研究对象,所有患者均行CBCT图像、计划CT图像采集。在患者放疗前进行CBCT扫描,将CBCT图像与计划CT图像匹配,得到左右（x轴）、头脚（y轴）、前后（z轴）三个方向的线性误差,分析出现的误差及误差的分布规律。利用模拟实际照射系统,进行模拟计划,得到实际照射靶区及正常组织受照射剂量,将其与治疗前计划比较,研究摆位误差对患者受照剂量的影响。结果：患者整体摆位误差为x轴（2.91±2.20）mm,y轴（3.89±2.17）mm,z轴（2.44±1.64）mm,x轴的MPTV为4.054 mm,y轴的MPTV为8.183 mm,z轴的MPTV为3.482 mm。模拟计划的CI、PTV的Dmin、Dmean、D95%均低于标准计划差异显著（P均＜0.05）,而模拟计划的HI低于标准计划（P＜0.05）。模拟计划的脊髓Dmax高于标准计划（P＜0.05）,而标准计划与模拟计划的双肺V20、Dmean,心脏V40差异比较无统计学意义（P均＞0.05）。结论：CBCT引导放疗摆位误差对中上段食管癌患者影响较小,提高PTV受照射剂量及治疗准确程度,对脊髓有保护效果。摆位误差对心、肺的剂量分布无明显影响。     

癔球症患者食管测压结果、心理特征分析及小剂量阿米替林的干预效果研究

摘要 目的：分析患者的食管测压结果、心理特征及小剂量阿米替林的干预效果。方法：选取2017年5月~2019年5月期间上海市静安区市北医院收治的癔球症患者137例（癔球症组）,另选取同期到上海市静安区市北医院体检的健康志愿者50例（非癔球症组）,比较两组食管测压结果、癔球症症状评分量表（GETS）评分、汉密尔顿抑郁量表-17（HAMD-17）评分、汉密尔顿焦虑量表-14（HAMA-14）评分。按随机数字表法将癔球症患者分为对照组（n=68）和研究组（n=69）,对照组给予常规治疗,研究组则在对照组的基础上联合小剂量阿米替林干预。比较对照组、研究组的临床疗效、不良反应。结果：癔球症组、非癔球症组患者食管上括约肌（UES）长度、UES残余压、食管下括约肌（LES）静息压、收缩前沿速度（CFV）、远端潜伏时间（DL）组间比较差异无统计学意义（P>0.05）;癔球症组患者UES静息压高于非癔球症组（P<0.05）。癔球症组患者GETS、HAMA-14、HAMD-17评分高于非癔球症组（P<0.05）。研究组治疗后的临床总有效率为84.06%（58/69）,高于对照组的66.18%（45/68）（P<0.05）。两组不良反应发生率比较差异无统计学意义（P>0.05）。结论：相对于非癔球症患者,癔球症患者具有较高的UES静息压,癔球症症状及较为严重的不良情绪,采用小剂量阿米替林对癔球症进行干预可提高治疗有效率,用药安全性较好。     

Radioprotection of eye lens using protective material in neuro cone-beam computed tomography: Estimation of dose reduction rate and image quality

PurposeIn cerebral angiography, for diagnosis and interventional neuroradiology, cone-beam computed tomography (CBCT) scan is frequently performed for evaluating brain parenchyma, cerebral hemorrhage, and cerebral infarction. However, the patient’s eye lens is more frequently exposed to excessive doses in these scans than in the previous angiography and interventional neuroradiology (INR) procedures. Hence, radioprotection for the lenses is needed. This study selects the most suitable eye lens protection material for CBCT from among nine materials by evaluating the dose reduction rate and image quality.MethodsTo determine the dose reduction rate, the lens doses were measured using an anthropomorphic head phantom and a real-time dosimeter. For image quality assessment, the artifact index was calculated based on the pixel value and image noise within various regions of interest in a water phantom.ResultsThe protective materials exhibited dose reduction; however, streak artifacts were observed near the materials. The dose reduction rate and the degree of the artifact varied significantly depending on the protective material. The dose reduction rates were 14.6%, 14.2%, and 26.0% when bismuth shield: normal (bismuth shield in the shape of an eye mask), bismuth shield: separate (two separate bismuth shields), and lead goggles were used, respectively. The “separate” bismuth shield was found to be effective in dose reduction without lowering the image quality.ConclusionWe found that bismuth shields and lead goggles are suitable protective devices for the optimal reduction of lens doses.     

On the eptihermal neutron energy limit for Accelerator-Based Boron Neutron Capture Therapy (AB-BNCT): Study and impact of new energy limits

Background and purpose: Accelerator-Based Boron Neutron Capture Therapy is a radiotherapy based on compact accelerator neutron sources requiring an epithermal neutron field for tumour irradiations. Neutrons of 10 keV are considered as the maximum optimised energy to treat deep-seated tumours. We investigated, by means of Monte Carlo simulations, the epithermal range from 10 eV to 10 keV in order to optimise the maximum epithermal neutron energy as a function of the tumour depth.Methods: A Snyder head phantom was simulated and mono-energetic neutrons with 4 different incident energies were used: 10 eV, 100 eV, 1 keV and 10 keV. ¹⁰B capture rates and absorbed dose composition on every tissue were calculated to describe and compare the effects of lowering the maximum epithermal energy. The Therapeutic Gain (TG) was estimated considering the whole brain volume.Results: For tumours seated at 4 cm depth, 10 eV, 100 eV and 1 keV neutrons provided respectively 54%, 36% and 18% increase on the TG compared to 10 keV neutrons. Neutrons with energies between 10 eV and 1 keV provided higher TG than 10 keV neutrons for tumours seated up to 6.4 cm depth inside the head. The size of the tumour does not change these results.Conclusions: Using lower epithermal energy neutrons for AB-BNCT tumour irradiation could improve treatment efficacy, delivering more therapeutic dose while reducing the dose in healthy tissues. This could lead to new Beam Shape Assembly designs in order to optimise the BNCT irradiation.     

A lonely dot on the map: Exploring the climate signal in tree-ring density and stable isotopes of clanwilliam cedar,South Africa

Clanwilliam cedar (Widdringtonia cedarbergensis; WICE), a long-lived conifer with distinct tree rings in Cape Province, South Africa, has potential to provide a unique high-resolution climate proxy for southern Africa. However, the climate signal in WICE tree-ring width (TRW) is weak and the dendroclimatic potential of other WICE tree-ring parameters therefore needs to be explored. Here, we investigate the climatic signal in various tree-ring parameters, including TRW, Minimum Density (MND), Maximum Latewood Density (MXD), Maximum Latewood Blue Intensity (MXBI), and stable carbon and oxygen isotopes (δ¹⁸O and δ¹³C) measured in WICE samples collected in 1978. MND was negatively influenced by early spring (October-November) precipitation whereas TRW was positively influenced by spring November-December precipitation. MXD was negatively influenced by autumn (April-May) temperature whereas MXBI was not influenced by temperature. Both MXD and MXBI were negatively influenced by January-March and January-May precipitation respectively. We did not find a significant climate signal in either of the stable isotope time series, which were measured on a limited number of samples. WICE can live to be at least 356 years old and the current TRW chronology extends back to 1564 CE. The development of full-length chronologies of alternative tree-ring parameters, particularly MND, would allow for an annually resolved, multi-century spring precipitation reconstruction for this region in southern Africa, where vulnerability to future climate change is high.     

Eye lens and thyroid gland radiation exposure for patients undergoing brain computed tomography examination

This study aims to estimate the effective radiation dose and organ dose from head CT procedures. It was conducted in three main private hospitals in Khartoum State-Sudan, using Toshiba machines with 64 slices. The total number of patients included in this study was 142 patients (82 males and 60 females). The effective dose and organ dose were calculated by CT Expo software. The effective dose slightly varied among patients according to gender and age. The effective dose for female patients (5.99 mSv) was higher than that for male patients (5.84 mSv), and the pediatric dose (5.46 mSv) was lower than the adults’ dose (5.94 mSv).The dose for eye lens was found lower for male patients (89.117 mSv) than the dose for female patients (94.62) mSv). According to patients’ age: the dose received by the lens of the eye was much lower in pediatric (79.93 mSv) than the adults (92.41 mSv). The dose for thyroid in female patients (33.52 mSv) was higher than the male patients (28 mSv). The pediatric dose (28.34 mSv) was lower than the adults’ dose (30.64 mSv).Departmental imaging protocol and lack of training among hospital staff are expected to be responsible for these variations. Therefore, this study recommends that the CT technologists be trained on suitable strategies to achieve dose optimization. Moreover, patients’ doses must be monitored regularly.