硼中子俘获治疗的辐射场特点与剂量估算

BNCT(硼中子俘获治疗)基于这样一种思想:10B的载体化合物会优先选择癌细胞作为靶而后与热中子反应,进而产生高能、短射程裂变产物α粒子和Li粒子。它是一种双重的靶向治疗方法。BNCT的治疗效果依赖于两个主要因素:源于10B(n,α)7Li核反应的高LET(传能线密度)粒子的生物效应和在靶细胞及其特异区域内的硼沉积。本文总结和探讨了BNCT的发展概况、辐射场的特点以及吸收剂量的计算方法。     

瘢痕疙瘩术后电子线治疗效果分析

目的：观察瘢痕疙瘩术后电子线照射在预防手术部位瘢痕疙瘩复发的效果。方法：瘢痕疙瘩术后第1天起手术部位给予电子线照射1～2周，剂量150～300cGY／次，2～5次／周，总剂量1050～2500cGY。结果：瘢痕疙瘩术后电子线照射的伤口无明显缝线反应，愈合良好，无裂开，瘢痕呈细线状，随访病例手术部位未见瘢痕疙瘩复发。结论：瘢痕疙瘩术后电子线治疗是预防瘢痕疙瘩复发的有效方法之一。     

三维颅面水平参考平面的确定方法

目的:比较在三维影像选取双侧耳点和双侧眶下点构建的不同水平面之间差异,分析不同水平面对双侧耳点和双侧眶下点位置的影响,为颅面部三维头影测量水平参考平面的确定提供依据。方法:选取32名正畸治疗前面部基本对称患者(颏下点离正中矢状面≤2 mm), 获取DICOM格式的大视野锥形束CT数据并导入到Dolphin软件,将鼻根点、蝶鞍点和枢椎齿突最高点构建正中矢状面,测量双侧耳点和双侧眶下点中随机三点构建的4种水平参考平面。分别定义为,平面1:水平面由右侧耳点和双侧眶下点构成;平面2:水平面由左侧耳点和双侧眶下点构成;平面3:水平面由双侧耳点与右侧眶下点构成;平面4:水平面由双侧耳点与左侧眶点构成。记录4个平面在三维空间当中的俯仰角、侧偏角和横滚角。间隔两周,一位研究者进行两次测量。计算组间相关系数(interclass correlation coefficient,ICC)比较两次测量结果的一致性,检验测量者自身的可靠性,进行单因素重复测量方差分析检验组内4个平面之间的差异,按年龄分为13~17岁组和≥18岁组。以枢椎齿突最高点为原点计算双侧耳点和双侧眶下点位置,应用圆周长公式分析头部转动对双侧耳点和双侧眶下点的影响。结果:单因素重复测量方差分析结果显示,不同三点构建的4种平面之间俯仰角、侧偏角和横滚角差异均无统计学意义(P=0.196、0.314、0.341)。头位转动对双侧耳点和双侧眶下点的影响分析结果为:1°俯仰角变化产生耳点约0.5 mm、眶下点约1.6 mm的变化;1°侧偏角变化产生耳点约1.1 mm、眶下点约1.5 mm的变化;1°横滚角变化产生耳点约1.2 mm、眶下点约0.7 mm的变化。结论:对于面部基本对称个体,应用三维头颅影像对双侧耳点和双侧眶下点中随机选取三个点构建的4种水平面之间差异无统计学意义;以双侧眶下点和右侧耳点构建的水平面可能最适合临床使用;头部不同方向的转动使双侧耳点和双侧眶下点产生不同位置的变化。     

锥形束CT在青少年多生牙诊断中的应用

目的：观察青少年多生牙影像学和临床特点,阐明锥形束CT （CBCT）在多生牙诊断中的临床应用价值。方法：选取经过CBCT扫描并已确诊的青少年多生牙患者共146例,分析患者性别、多生牙数目、形态、位置及与邻牙及骨组织的结构关系等,评估多生牙形态不同引起邻牙吸收率的变化。结果：146例患者男女比例为1.98：1（97/49）,其中95例（65.07%）为单个多生牙。146例患者共有203颗多生牙,其中圆锥形多生牙为132颗（65.02%）,倒置多生牙112颗（55.17%）,牙根弯曲多生牙48颗（23.65%）;多生牙形态不同引起牙根吸收率比较差异无统计学意义（P>0.05）。结论：CBCT可直观显示多生牙数目和位置等影像学及临床特点,可为多生牙的诊断和治疗方案的制定提供重要的临床依据。     

河南省核查放射治疗参考与非参考条件下剂量学参数方法验证

目的 研究用热释光剂量计（TLD）方法核查放射治疗参考条件和非参考条件下剂量学参数的可靠性验证。方法 在参考条件和非参考条件下,用建立的TLD方法,核查10条6 MV光子线束剂量随照射野大小和45°楔形板等变化,4条9 MeV电子线束轴向最大剂量点处等剂量学参数,TLD估算结果与剂量仪测量结果进行对比。结果 6 MV光子线束TLD估算结果与指形电离室测量结果的平均相对偏差为4.7%,按照IAEA要求允许偏差不超过±7%;9 MeV电子线束TLD估算结果与平行板电离室测量结果平均相对偏差为2.4%,均未超过IAEA允许偏差要求（±5%）。结论 用TLD核查参考条件和非参考条件下放射治疗剂量学参数方法可靠,简单易行。     

利用四维锥形束CT指导肺癌内靶区的勾画

目的 研究四维锥形束CT(4D-CBCT)指导肺癌内靶区勾画的可行性。方法 简单随机法选取本院24例肺癌患者。平静呼吸下CT模拟定位获得CT图像,首次治疗前4D-CBCT扫描获得4D-CBCT中位图像,将4D图像重建算法更改为3D,获得3D-CBCT图像。图像融合算法取骨配准,分别在定位CT、4D-CBCT中位图像、3D-CBCT图像上勾画大体肿瘤靶区(GTV),定义GTV到临床靶区(CTV)的外扩边界为7 mm,获得CTV_CT、ITV_4D和ITV_3D,基于CTV_CT在三维方向上外扩5 mm得到ITV_CT。比较靶区间中心点位置、体积、相似度和相互包含关系的差异。结果 ITV_CT与ITV_3D在中下叶组的头脚方向上,靶区中心点位置差异有统计学意义(Z=-2.027,P<0.05)。在靶区体积方面,ITV_CT最大,与ITV_3D相比差异有统计学意义(Z=-2.941,P<0.05),ITV_4D最小,但与ITV_3D相比差异无统计学意义(P>0.05)。ITV_CT与ITV_3D相似度均数<75%,ITV_4D与ITV_3D相似度均数>90%(Z=-2.940、-2.975,P<0.05)。ITV_CT、ITV_4D未被ITV_3D包含的比例均数为40%和5%(Z=-2.952、-3.185,P<0.05)。结论 4D-CBCT的中位图像可以缩小内靶区的勾画范围,为肺癌的自适应放疗提供选择。     

The effective dose of different scanning protocols using the Sirona GALILEOS? comfort CBCT scanner

Objectives:

To determine the effective dose and CT dose index (CTDI) for a range of imaging protocols using the Sirona GALILEOS^® Comfort CBCT scanner (Sirona Dental Systems GmbH, Bensheim, Germany).

Methods:

Calibrated optically stimulated luminescence dosemeters were placed at 26 sites in the head and neck of a modified RANDO^® phantom (The Phantom Laboratory, Greenwich, NY). Effective dose was calculated for 12 different scanning protocols. CTDI measurements were also performed to determine the dose–length product (DLP) and the ratio of effective dose to DLP for each scanning protocol.

Results:

The effective dose for a full maxillomandibular scan at 42 mAs was 102 ± 1 μSv and remained unchanged with varying contrast and resolution settings. This compares with 71 μSv for a maxillary scan and 76 μSv for a mandibular scan with identical milliampere-seconds (mAs) at high contrast and resolution settings.

Conclusions:

Changes to mAs and beam collimation have a significant influence on effective dose. Effective dose and DLP vary linearly with mAs. A collimated maxillary or mandibular scan decreases effective dose by approximately 29% and 24%, respectively, as compared with a full maxillomandibular scan. Changes to contrast and resolution settings have little influence on effective dose. This study provides data for setting individualized patient exposure protocols to minimize patient dose from ionizing radiation used for diagnostic or treatment planning tasks in dentistry.     

Comparison of the influence of FOV sizes and different voxel resolutions for the assessment of periodontal defects

Objectives:

This study assessed the influence of different voxel resolutions of two different CBCT units on the in vitro detection of periodontal defects.

Methods:

The study used 12 dry skulls with a maxilla and a mandible. Artificial defects (dehiscence, tunnel, fenestration) were separately created on the anterior, premolar and molar teeth using burrs. A total of 14 dehiscences, 13 fenestrations, 8 tunnels and 16 non-defect controls were used in the study. Images were obtained from two different CBCT units in six voxel sizes (voxel size: 0.080, 0.100, 0.125, 0.150, 0.160 and 0.200 mm³). Kappa coefficients were calculated to assess both intra- and interobserver agreements for each image set.

Results:

Overall intraobserver kappa coefficients ranged between 0.978 and 0.973 for the 0.080-mm³ images and between 0.751 and 0.737 for the 0.160-mm³ images, suggesting notably high intraobserver agreement for detecting periodontal defects. CBCT performed significantly better at detecting fenestrations (p < 0.05) than tunnel and dehiscence defects. No statistically significant difference was found between the detection of dehiscence and tunnel defects (p > 0.05).

Conclusions:

A voxel size of 0.150 mm³ was identified as the cut-off point for overall detection of periodontal defects. CBCT should be considered the most reliable imaging modality for the diagnosis of periodontal defects.     

Image resolution and magnification using a cone beam densitometer: optimizing data acquisition for hip morphometric analysis

Bone mineral density (BMD) is a primary determinant of hip fracture risk. However, other factors, notably the femoral geometry, can influence hip fracture risk. The purpose of this study was to evaluate the potential of a new cone beam densitometer, the DMS Lexxos, in order to visualise femoral morphometry. Resolution, magnification and distortion were assessed in vitro using a line pair test pattern and a matrix test object. Results were given in comparison with currently available systems: the Hologic Discovery A and the Lunar Prodigy densitometers. The DMS Lexxos image resolution was the same in the longitudinal and transversal directions evaluated between 1.4 and 0.5 line pairs/mm (lps/mm) for an attenuation varying from 25 to 325 mm of Perplex. The longitudinal resolution was evaluated between 0.9 and 0.5 lps/mm with the Hologic Discovery densitometer, and inferior to 0.5 with the Lunar Prodigy; as for transversal resolution, it varied from 0.63 to 0.5 lps/mm and from 0.6 to inferior 0.5 lps/mm, respectively. The image was isotropic without magnification with the GE-Lunar Prodigy, whereas there was only a transversal magnification with the Hologic Discovery device. The magnification was about 1.17% cm^–1 in the two directions, while increasing the distance of the phantom above the examination table with the Lexxos. This magnification was isotropic without distortion. The magnification could be evaluated from two images taken before and after translation of the C-arm, and a magnification correction could be applied. This method was applied to a phantom and to a human cadaver femoral bone.