125I粒子平面布源剂量学研究

Objective To study the dosimetry of different arrangements of 125I seeds in one plane.Methods Nine different in-plane arrangements of 9 125I seeds (2.035 × 107 Bq/seed) were simulated according to distance (cm) along x (horizontal)- and y( longitudinal )-axis using the 3-dimensional treatment planning system (TPS) (3D-TPS): x0.5, y0. 5; x0. 5, y1.0; x0. 5, y1.5; x1.0, y1.0; x1.0, y1.5;x1.5, y1.5; x0. 5, y0. 5 (2)1.0; x0.5, y1.0 (2)0.5; x1.0, y1.0 (2)0.5. The isodose curves of 40,80, 130, 145 and 200 Gy were created and the area, radius and medical cost under the 40, 80, 130, 145and 200 Gy isodose curves were calculated. Results The area, radius and medical cost under the same isodose curves were significantly different with each 125I seed arrangement. The arrangements which had the biggest area under curves of 40, 80, 130, 145 and 200 Gy isodose were x1. 5, y1. 5; x1. 0, y1. 0; x1. 0,y1. 0; x0. 5, y1. 0 and x0. 5, y1. 0, respectively. Conclusion The matched peripheral dose and therapeutic effect were affected significantly by the geometric arrangement of 125I seeds.     

不同间距125I粒子放射性食管支架的剂量学对比

目的研究不同间距125I粒子放射性食管支架在肿瘤靶区的剂量学分布。方法按粒子纵横垂直间距0.5、1和1.5 cm将实验分成 A、B、C 3组,用激光扫描仪扫描一张画有直径2 cm的圆形并标记有5 cm刻度的白纸,以JPEG格式存储于计算机桌面。利用图像转换程序,创建17层图片,每层图片层距为5 mm,将图片传输到计算机治疗计划系统（TPS）中,模拟直径2 cm,长度8 cm食管支架,利用TPS勾画肿瘤靶区（gross tumour volume,GTV）,以模拟食管支架边界为肿瘤靶区内界,外扩0.5 cm为外界,勾画环形且长度为6 cm的靶区,设定相同处方剂量,每组分别于模拟食管支架上先后7次载入0.3、0.4、0.5、0.6、0.7、0.8、0.9 mCi 125I粒子,应用TPS得出DVH图,记录A、B、C 3组D90、V90。结果 A、B、C 3组D90算数平均数分别为（217.15±19.92）、（89.16±32.44）和（31.68±11.52）Gy（F=159.18,P<0.05）;V90算术平均数分别为（100.00±0.00）%、（86.47±21.36）%、（29.33±21.54）%（F=32.11,P<0.05）。结论直径2 cm 125I粒子放射性食管支架布源推荐粒子纵横垂直间距为1.0 cm,活度为0.6 mci。     

CT导向下125I粒子植入治疗难治生肺癌的疗效观察

目的 评价CT导向下125I粒子植入肿瘤组织间治疗难治性肺癌的临床价值.方法 共35例晚期难治性肺癌患者接受125I粒子植入治疗.术前采用治疗计划系统计算布源,术中将活度为2.855～3.087 MBq的125I粒子在CT导向下植入肿瘤组织间,粒子按照0.5～1.0 cm间距平面插植.肿瘤周边匹配剂量为150～180 ...     

治疗计划系统模拟125I粒子周边与中心分布剂量对比研究

目的：探讨同活度、同数量125I粒子周边分布与中心分布的剂量学差异。方法采用计算机三维放射治疗计划系统（3D-TPS）勾画出2、2.5、3、3.5、4、4.5、5 cm等7种边长的正方体,模拟不同大小肿瘤,分别载入0.5 mCi 125I粒子,处方剂量145 Gy,粒子周边分布（周边组）,得出剂量体积直方图（DVH）及90%靶体积吸收剂量（D90）、90%处方剂量覆盖的体积占靶体积百分比（V90）、最高剂量点、平均剂量等参数;同样方法将以上各肿瘤中载入粒子作中心分布（中心组）,得出上述参数。结果周边组和中心组D90均数分别为（147.29±0.58）Gy和（106.08±9.40）Gy,差异有统计学意义（t=-4.292,P=0.005）;V90均数分别为（95.46±0.44）%和（9.07±4.19）%,差异有统计学意义（t=-3.831,P=0.009）;最高剂量均数分别为（1224.65±12.7）Gy和（1532.48±48.54）Gy,差异有统计学意义（t=6.823,P=0.000）;平均剂量均数分别为（192.14±2.89）Gy和（179.81±5.40）Gy,差异有统计学意义（t=-2.847,P=0.029）。结论125I粒子不同分布模式直接影响剂量分布,粒子数目和活度相同时周边布源有较好的剂量分布。     

125I粒子条剂量分布研究

目的 探讨连续线状排列125I粒子条剂量分布.方法 通过玻璃剂量计及IP板测量粒子条剂量立体分布并与计算软件结果比较.结果 玻璃剂量计测量数据与软件计算相关性良好(r＞ 0.99,P=0.000).除R=0.5 cm处外,两者差异性无统计学意义(P＜0.05).IP板测定2 cm以内粒子间存在自吸收现象,自吸收的量约22.8％.结论 连续线状排列的125I粒子条辐射等计量分布类似于柱形体,为其应用于腔内放射治疗提供理论依据.     

携带125I粒子导管和徒手粒子植入模拟病灶后粒子纵向间距准确性的对比研究

目的 对比携带¹²⁵I粒子的可降解导管植入和徒手粒子植入后粒子纵向间距的准确性。方法 本研究用薯蓣制成24个模拟病灶,分为徒手组和粒子导管组,每组12个模拟病灶,由3位医师完成粒子和粒子针插植,每位医师每组插植4个病灶,每组共插植60针道,并按设定粒子间距（0.5和1.0 cm）分别在两组模拟病灶内行粒子植入。术后CT复查,并测量粒子纵向间距。配对t检验分析徒手组和导管组与设定间距偏离的差异。结果 徒手组与设定间距的偏离程度分别为（0.184±0.047）和（0.127±0.051）cm,导管组与设定间距的偏离程度分别为（0.007±0.006）和（-0.003±0.006）cm,导管组粒子的偏离程度明显小于徒手组（t=3.804、2.499,P<0.05）。结论 携带¹²⁵I粒子导管的应用,使粒子纵向间距的准确性优于徒手组,受术者的影响较小。     

125I粒子持续低剂量率照射对人前列腺癌细胞的抑制作用

目的探讨^125I粒子持续低剂量率照射对人前列腺癌细胞株（PC3）增殖抑制以及对细胞周期的影响。方法^125I粒子（初始剂量率2.77cGy/h）和^60Coγ射线（吸收剂量率2.215Gy/min）对体外培养的PC3细胞进行0、0.5、1、1.5、2、4、6和8Gy照射,用细胞计数、锥虫蓝染色和集落形成法检测细胞增殖、细胞活力和细胞存活率的情况;用单击多靶模型拟合剂量存活曲线;用流式细胞仪检测细胞周期。结果随着照射剂量的增加,^125I粒子照射组的细胞生长比^60Coγ射线组更加明显地受到抑制（P〈0.05）。^125I粒子照射PC3细胞D0值为2.243,Dq为0.87,N为1.618,SF2为0.5。^60Co照射组PC3细胞放射生物学参数D0值为2.824,Dq为1.08,N为1.587,SF2为0.7。^60Co和125I粒子的RBE比值为1.4。与空白对照组相比,^125I粒子组和^60Co组4Gy照射细胞24h后均出现G2期阻滞。结论^125I粒子照射能抑制人前列腺癌细胞的增殖并能使PC3细胞阻滞于G2期。     

125I放射性粒子植入计划定制研究

目的 定制¹²⁵I 放射性粒子植入计划的优选方案。方法 将¹²⁵I 粒子等间距植入直径为1、2和3 cm的3种球形模体和三径分别为1 cm×1 cm×2 cm、1 cm×1 cm×3 cm、1 cm×2 cm×2 cm、1 cm×2 cm×3 cm、1 cm×3 cm×3 cm、2 cm×2 cm×3 cm和2 cm×3 cm×3 cm的7种椭球形模体,粒子分布均匀对称,调整粒子活度和间距,使靶区剂量满足处方剂量D₉₀ 145 Gy,并实现尽可能适形均匀的剂量分布。初始粒子间距是1 cm,为改善靶区剂量分布适形度和均匀性,将粒子间距调整为0.75 cm。通过评价均匀性指数（HI）、靶区外体积指数（EI）和适形指数（CI）定制粒子植入优选方案。同时记录植入粒子活度和数目。结果 对直径1 cm的球形靶区,粒子间距1和0.75 cm 时HI分别为40.0%和55.9%,EI分别为98.3%和95.1%,CI均为0.44;对直径3 cm的球形靶区和1 cm×2 cm×2 cm的椭球形靶区,粒子间距1 cm植入方式的HI、EI和CI优于粒子间距0.75 cm 的植入方式。对其余靶区粒子间距0.75 cm植入方式的EI和CI均优于间距1 cm的植入方式,HI略小于间距1 cm的植入方式。粒子间距0.75和1 cm植入单颗粒子活度分别为17.0~27.8 MBq 和30.0~58.8 MBq,间距0.75 cm比间距1 cm多植入粒子2~10颗。结论 对于10种靶区,除直径为1 cm、3 cm的球形靶区和1 cm×2 cm×2 cm 的椭球形靶区以外,其余7种靶区0.75 cm 植入方式的剂量分布适形度更好,靶区外接受处方剂量体积更小,为粒子均匀植入的优选方案。     

CT导向下125I粒子植入术治疗恶性肿瘤

目的:评价CT导向下瘤体内125I粒子植入治疗恶性肿瘤的操作方法、可行性、安全性及其疗效。方法:21例26个病灶CT导向下穿刺并在瘤体内植入125I粒子,其中原发性病灶9个,转移性病灶17个。在CT导向下将125I粒子植入恶性肿瘤病灶内,采用治疗计划系统(TPS)计算布源,125I粒子的放射性活度为22、26、30、33MBq/粒,较大活度的粒子间距为1.5cm,较小活度的粒子间距为1.0cm。结果:21例粒子植入均顺利完成,术中无并发症发生,粒子在病灶内的分布与植入前计划基本一致。每个瘤体内植入125I粒子数为540粒(平均14粒)。10例恶性骨肿瘤患者植入术后疼痛均有明显缓解。术后随诊复查CT,18个病灶明显缩小,4个病灶内出现坏死组织,4个病灶大小无明显变化。结论:CT导向下瘤体内植入125I粒子近距离放射治疗恶性肿瘤是一种安全、有效、可靠的治疗方法。     

CT导引下125^Ⅰ粒子植入治疗兔VX2肿瘤的实验研究

目的探讨CT导引下125^Ⅰ粒子组织间植入兔VX2肿瘤模型对细胞凋亡率的影响。方法在20只兔两侧大腿肌肉内建立VX2肿瘤模型,3周后待肿瘤灶长至直径约2cm备用,每只兔随机选择一侧肿瘤灶作为治疗侧,另一侧作为对照侧,治疗侧在CT导引下经皮穿刺将活度为0.9mCi的125^Ⅰ粒子植入肿瘤组织内,对照侧肿瘤灶内植入无活性的空心粒子,于术后即刻、72h、1、2、3周在CT导引下分别穿刺距粒子0.5～1cm、1.0～1.5cm处组织检测细胞凋亡率。结果125^Ⅰ粒子植入后即刻、72h、1、2、3周距粒子0.5～1.0cm处对照侧和治疗侧细胞凋亡率分别为（5.43&#177;0.67）%和（5.48&#177;0.66）%（P〉0.05）,（5.45&#177;0.58）%和（11.60&#177;0.87）%（P〈0.05）,（6.07&#177;0.69）%和（18.8&#177;0.64）%（P〈0.05）,（5.94&#177;0.43）%和（37.20&#177;0.39）%（P〈0.01）,（6.30&#177;0.58）%和（36.56&#177;0.67）%（P〈0.01）。距125^Ⅰ粒子1.0～1.5cm处各个时间点对照侧与实验侧细胞凋亡率差别均无统计学意义（P〉0.05）。结论125^Ⅰ粒子组织间植入可诱导肿瘤细胞凋亡,植入后72h细胞凋亡率开始增加,术后2周达高峰并维持在高水平,且随距125^Ⅰ粒子的距离增加,细胞凋亡率迅速下降。     

125I与5-氟脲嘧啶联合应用治疗复发性甲状腺癌的疗效

目的探讨应用放、化疗粒子联合植入法靶向治疗复发性甲状腺癌的可行性、安全性及短期疗效。方法应用放、化疗粒子联合植入法靶向治疗甲状腺癌术后放疗后复发病人9例。在治疗计划指导下，经B超引导交替植入5．氟脲嘧啶(5-FU)缓释化疗粒子和^125I粒子。结果9例病人手术成功。术后6—9个月CT复查瘤体不同程度缩小，其中1例完全缓解，6例部分缓解，2例无变化，局部控制率为78％。随访8—26个月，现病人全部存活。结论放射性^125I粒子和5-FU缓释化疗粒子联合应用局部植入技术是综合治疗复发性甲状腺癌的较有效手段之一。     

粒子植入术后肿瘤缩小时不同布源方式对剂量的影响

目的 假定¹²⁵I粒子植入术后肿瘤每月以20%速度退缩时,研究等间距与周边密集、中间稀疏2种布源方式对剂量的影响。方法 利用计算机三维治疗计划系统（TPS）勾画4 cm×5 cm的圆柱形肿瘤,根据布源方式不同分为等间距组和周边密集、中间稀疏组,以处方剂量125 Gy载入放射性活度1.85×10⁷Bq ¹²⁵I粒子行术前计划。假设¹²⁵I粒子植入肿瘤后肿瘤高不变,直径每月以20%的速度缩小,粒子随肿瘤均匀向心性集中,分别计算¹²⁵I粒子植入术后0、1、2、3个月时90%靶体积吸收剂量（D₉₀）、90%处方剂量覆盖体积占靶体积的百分比（V₉₀）、150%处方剂量覆盖体积占靶体积的百分比（V₁₅₀）。结果 等间距组载入粒子85颗,植入0、1、2、3个月后的D₉₀分别为126.20、130.41、133.82和139.48 Gy,V₉₀分别为97.0%、98.1%、99.3%和100%,V₁₅₀分别为70.2%、69.9%、71.1%和71.5%;周边密集、中间稀疏组植入粒子75颗,植入0、1、2、3个月后的D₉₀分别为126.46、125.41、123.50和128.83 Gy,V₉₀分别为95.2%、95.7%、94.9%和97.6%,V₁₅₀分别为52.8%、60.4%、62.7%和59.3%。结论 当肿瘤直径每个月以20%速度退缩时,粒子等间距分布时肿瘤预期吸收剂量逐渐增加;周边密集、中间稀疏的布源方式肿瘤预期吸收剂量不变,且高剂量区范围明显小于等间距布源。     

125I粒子持续低剂量率照射胰腺癌细胞株PANC-1相对生物效应的研究

目的 探讨国产6711型¹²⁵I粒子的相对生物效应,并对其照射杀伤PANC-1细胞的效果进行了初步探讨。方法 PANC-1细胞处于指数生长期时,行¹²⁵I粒子离体照射;在初始剂量率为2.59 cGy/h时,分别给予1、2、4、6、8和10 Gy照射。⁶⁰Co照射作为对照组,吸收剂量率为2.21 Gy/min,给予相同剂量照射。用锥虫蓝染色法检测细胞死亡比率,并比较在4 Gy照射后培养12、24、48和72 h细胞死亡率随时间变化。采用克隆形成实验,计算细胞克隆形成率,绘制生存曲线,得出生物学参数,并测定¹²⁵I粒子与⁶⁰Co的相对生物效应。结果 在相同剂量照射下,¹²⁵I持续低剂量率照射与⁶⁰Co照射相比,当≥4 Gy时,细胞死亡率明显增高。在4 Gy照射后,随着时间延长细胞死亡率增高,两者相比有明显差异。从生存曲线分析,¹²⁵I粒子持续低剂量率照射细胞存活分数比60Co低,¹²⁵I粒子相对于⁶⁰Co的生物效应为1.45。结论 ¹²⁵I粒子持续低剂量率照射与⁶⁰Co高剂量率照射相比,细胞杀伤效应更强;测定的相对生物效应与其他研究者测量的结果相似;将为临床¹²⁵I粒子治疗肿瘤提供一定的参考价值。     

SPECT/CT探测颅内肿瘤粒子植入放射浓聚计数值与剂量关系

目的研究SPECT/CT探测颅内肿瘤125I粒子植入放射浓聚计数值与剂量关系,探讨颅内肿瘤粒子植入后剂量可视化的可行性。方法在CT引导下应用模板辅助穿刺颅内肿瘤模型。所有植入针按照术前计划在肿瘤内呈锥形分布,CT扫描植入针位置无误后按照术前计划植入2.035×10⁷ Bq粒子25颗。然后将术后头颅模型进行SPECT/CT扫描及图像融合。CT图像传入计算机治疗计划系统(TPS)行验证计划。在肿瘤最大层面分别沿着和垂直中间植入针方向测量40 Gy、60 Gy、80 Gy、100 Gy、140 Gy等剂量线包绕区域的长径。在SPECT/CT融合图像上找出对应剂量(D)位置的放射性浓聚计数值(x),应用SPSS18.0软件比较沿着针道方向和垂直针道方向两组计算值有无差异,并计算计数值与剂量的关系,得出关系公式。结果沿着针道方向与TPS中40 Gy、60 Gy、80 Gy、100 Gy、140 Gy等剂量线对应的放射性浓聚计数值分别为38.6±5.7、65.2±5.4、87±4.5、110±5.2、132.8±7.3;垂直针道方向与相应剂量对应的计数值分别81.7±22.8、178.2±49.8、247.7±65.8、289.7±67.2、358.7±74.5,两组相比差异有统计学意义,P<0.001。针道方向上计数值(x)与剂量(D)关系为指数关系,方程为:D=25.787×1.013^X。结论SPECT/CT显像可使颅内肿瘤125I粒子植入周围剂量可视化,放射性计数值与粒子剂量存在指数关系,为研发粒子植入颅内肿瘤术后剂量验证新方法奠定了理论基础。     

Loose seeds vs. stranded seeds: a comparison of critical organ dosimetry and acute toxicity in (125)I permanent implant for low-risk prostate cancer

PURPOSE: To compare the critical organ dosimetry and toxicity of loose seeds (LS) with stranded seeds (SS) in (125)I permanent implant for low-risk prostate cancer. METHODS AND MATERIALS: Two cohorts of 20 patients each were treated in Institutional Review Board-approved protocols designed to assess prostate edema and seed stability using MR-CT fusion on Days 0, 7, and 30 after permanent implant. (125)I LS were used for one cohort and (125)I SS for the other. Rectal wall dosimetry was compared for the two cohorts using RV100 and RD1cc and urethral dosimetry using UD5, UD30, and UV150. Statistical comparisons were performed using unpaired Student's t test. RESULTS: At each time point (Days 0, 7, and 30), both the mean RD1 cc (SS: 123.1, 139.7, and 156.1 Gy vs. LS: 90.2, 104, and 129.4 Gy, respectively) and the mean RV100 (SS: 0.63, 1.0, and 1.4 cc vs. LS: 0.2, 0.4, and 0.73 cc, respectively) were significantly higher for strands (all p-values<0.01). Only 1 patient developed radiotherapy oncology group (RTOG) Grade 1 acute rectal toxicity in the loose seed cohort, whereas 3 patients had Grade 1 and 1 patient had Grade 2 toxicity with strands. The mean percentage increase of UD5 (7.7% LS vs. 24.6% SS; p=0.004) and UD30 (5% LS vs. 15.9% SS; p=0.02) from preplan to Day 30 was higher for strands. The increase in UV150 from baseline to Day 30 was significantly higher for strands (0.2 vs. 0.06 cc; p=0.01). Urinary toxicity was similar in both cohorts. CONCLUSIONS: SS resulted in higher dose to urethra and rectal wall compared with LS on postimplant dosimetry. A trend toward higher acute rectal toxicity rate was observed for SS.     

Effects of low dose radiation therapy on adjuvant induced arthritis in rats

PURPOSE: Substantial clinical evidence shows the efficacy of low dose radiotherapy (RT) in the treatment of painful osteoarthritis. Experimental investigations into these empirically clinical observations remain scarce. This study investigated in vivo the effects of daily 5 x 1.0 Gy versus 5 x 0.5 Gy on adjuvant induced arthritis in rats in order to explore whether there is a dose dependence of anti-inflammatory efficacy. MATERIALS AND METHODS: Adjuvant arthritis in female Lewis rats was induced by intradermal injection of heat inactivated Mycobacterium tuberculosis on day 0. Both hind paws were X-irradiated daily from days 15 to 19 after induction according to four protocols (15 animals/group): group 1, 5 x 1.0 Gy (non-arthritic animals); group 2, sham-irradiated control; group 3, 5 x 1.0 Gy; group 4, 5 x 0.5 Gy. The clinical parameters arthritis score (AS), hind paw volume (HPV), body weight, and erythrocyte sedimentation rate (ESR) were determined. On days 21 and 30 histological sections of at least 12 ankle joints per group were analysed semi-quantitatively. RESULTS: Local irradiation of non-arthritic rats (group 1) with 5 x 1 Gy did not induce any arthritic signs. Sham-irradiated arthritic rats (group 2) showed a full-blown arthritic syndrome. Treatment of arthritic rats with 5 x 1 Gy (group 3) or 5 x 0.5 Gy (group 4) led to a reduction of mean AS from day 21 to 29 compared with group 2 (days 27-29--group 3: p=0.037; group 4: p=0.034), with no differences in efficacy between groups 3 and 4. Concurrently, following radiation treatment there was no further increase in HPV. At the end of the observation period, this effect demonstrated a dose-dependent level of significance (days 27-29--group 3: p=0.0036; group 4: p=0.039). A significant decrease in the ESR was noted in both irradiated arthritic groups on day 21 (group 3: p=0.015; group 4: p=0.006). The histopathological analysis revealed a highly significant reduction of cartilage and bone destruction on day 30 in both irradiated groups. CONCLUSIONS: This study confirms by objective criteria the anti-inflammatory efficacy of low dose RT and gives some indication for a dose dependence of its efficacy.     

125I粒子与缓释化疗粒子联合应用靶向治疗复发性直肠癌

目的 探讨应用放、化疗粒子联合植入法综合治疗复发性直肠癌的可行性、安全性及短期疗效。方法 自2001年12月至2005年12月,应用放、化疗粒子联合植入法综合治疗复发性直肠癌26例,均为直肠癌Mile＇s术后盆腔复发病人。在治疗计划指导下,交替植入氟尿嘧啶缓释化疗粒子和放射性125I粒子。放射性粒子的肿瘤匹配周边剂量（matched peripheral dose,MPD）为90～130Gy。平均每例使用^125Ⅰ粒子12粒,氟尿嘧啶600 mg。结果 26例病人手术均顺利完成,未发生出血、感染等并发症,经盆腔摄片证实放射性粒子的位置无变化。疼痛缓解率为88.9%（16/18）,平均疼痛缓解时间为5～10 d。于术后3～6个月CT复查肿瘤变化,提示瘤体不同程度缩小,其中2例完全缓解,19例部分缓解,4例稳定,局部控制率为81%。随访6～42个月,中位生存期为29个月,最长1例随访时间为术后42个月,现仍存活。1例术后6个月死于全身广泛转移。结论 放射性125I粒子和氟尿嘧啶缓释化疗粒子联合应用局部植入技术具有安全、微创及并发症发生率低的特点,是综合治疗复发性直肠癌较有效的手段之一。     

Precision and accuracy in CT attenuation measurement of vascular wall using region-of-interest supported by differentiation curve

Objectives

To evaluate the precision and accuracy in CT attenuation measurement of vascular wall using region-of-interest (ROI) supported by differentiation curves.

Study design

We used vascular models (actual attenuation value of the wall: 87 HU) with wall thicknesses of 1.5, 1.0, or 0.5 mm, filled with contrast material of 250, 348, or 436 HU. The nine vascular models were scanned with a 64-detector CT. The wall attenuation values were measured using three sizes (diameter: 0.5, 1.0, and 1.5 mm) of ROIs without differentiation curves. Sixteen measurements were repeated for each vascular model by each of two operators. Measurements supported by differentiation curves were also performed. We used analyses of variance with repeated measures for the measured attenuations for each size of the ROI.

Results

Without differentiation curves, there were significant differences in the attenuation values of the wall among the three densities of contrast material, and the attenuation values tended to be overestimated more as the contrast material density increased. Operator dependencies were also found in measurements for 0.5- and 1.5-mm thickness models. With differentiation curves, measurements were not possible for 0.5- and 1.0-mm thickness models. Using differentiation curves for 1.5-mm thickness models with a ROI of 1.0- or 1.5-mm diameter, the wall attenuations were not affected by the contrast material densities and were operator independent, measuring between 75 and 103 HU.

Conclusions

The use of differentiation curves can improve the precision and accuracy in wall attenuation measurement using a ROI technique, while measurements for walls of ≤1.0 mm thickness are difficult.