99m Tc-HYNIC-TOC人体内照射剂量研究

背景与目的：放射性显像药物在人体内的剂量分布、各器官的吸收剂量及全身有效剂量数据非常重要。研究^99mTc标记的经肼基烟酰胺修饰的奥曲肽（^99mTc-Hydrazinonicotinyl-Tyr3-Octreotide，^99mTc-HYNIC-TOC）在人体内各器官的吸收剂量、全身吸收剂量及全身有效剂量。方法：对2018年5—6月复旦大学附属肿瘤医院收治的5例神经内分泌肿瘤患者静脉注射370 MBq^99mTc-HYNIC-TOC后于0.5、1.0、2.0、4.0和8.0 h行全身平面采集，其中2.0 h平面采集后即刻行全身断层采集。断层数据经迭代重建后，将数据导入GE Dosimetry Toolkit处理，在单光子发射计算机断层显像（single photon emission computedtomography，SPECT）/CT融合图像上勾画各器官生成感兴趣区（region of interest，ROI），获得相应时间-活度曲线并计算曲线下面积得到滞留时间。依据美国核医学会医用内照射剂量学（Medical Internal Radiation Dose，MIRD）委员会提出的内照射剂量计算方法（MIRD体系），利用OLINDA/EXM软件计算^99mTc-HYNIC-TOC在人体内各器官的吸收剂量、全身吸收剂量和全身有效剂量。结果：脾脏、膀胱、肾脏的单位活度吸收剂量较高，男性分别为0.042、0.019和0.016 mGy/MBq，女性分别为0.026、0.027和0.017 mGy/MBq。大脑、皮肤、甲状腺的单位活度吸收剂量较低，男性分别为0.000 3、0.000 5和0.000 5 mGy/MBq，女性分别为0.000 3、0.000 5和0.000 6 mGy/MBq。对放射线敏感的器官如骨原细胞、胸腺和红骨髓的单位活度吸收剂量均较低，范围为0.001 2~0.002 2 mGy/MBq。全身平均单位活度吸收剂量男性为0.001 7 mGy/MBq，女性为0.0016 mGy/MBq。全身单位活度有效剂量男性为0.004 58 mSv/MBq，女性为0.004 55 mSv/MBq。结论：^99mTc-HYNIC-TOC可安全地用于人体，其有效剂量低于允许范围上限。该研究结果可为临床安全使用^99mTc-HYNIC-TOC提供依据，也为其他放射性药物的安全性评估和加快临床转化提供新的可行方案。     

153Sm-EDTMP治疗多发骨转移瘤的剂量效应关系初步观察

背景与目的:核素内照射治疗的剂量计算一直是核医学研究的热点和难点之一,用蒙特卡罗法(MonteCarlo,MC)计算153Sm-乙二胺四甲撑膦酸(Samarium-153ethylenediaminetetramethylenephosphonicacid,153Sm-EDTMP)治疗多发性骨转移患者骨转移灶、骨髓等靶器官的吸收剂量,初步探讨病灶吸收剂量与153Sm-EDTMP止痛疗效的关系。方法:选择鼻咽癌、乳腺癌伴全身多发骨转移患者4例,患者骨痛剧烈,骨痛评分Ⅳ级,按0.65×37MBq/kg药量静脉注射,行153Sm-EDTMP内照射治疗。基于患者的时序性SPECT/CT扫描和累积尿液的放射性强度测定,确定患者的药物代谢动力学特点,利用MCEGS4程序计算骨转移灶和其它靶器官的吸收剂量及其分布。观察骨痛症状的缓解状况和生活质量的改善情况。结果:153Sm-EDTMP治疗后,患者骨痛明显减轻,骨痛评分达Ⅱ级,持续3～4周。骨转移灶和其它靶器官的三维吸收剂量分布图显示:病灶内剂量分布不均匀。骨转移灶的最高吸收剂量约为4.9～5.9Gy,病灶边缘的吸收剂量为2.0Gy左右,以病灶区最高剂量为参考点,则骨髓剂量为0.48～1.1Gy,骨皮质剂量为0.51～0.85Gy;病灶周围软组织的吸收剂量为0.01～0.14Gy。结论:按常规单次153Sm-EDTMP治疗,骨转移病灶远未达到30Gy姑息剂量水平,虽有一定的止痛结果,但止痛持续时间短,疗效有限,与临床观察结果一致。     

FDG-PET/CT在鼻咽癌放疗后随访中的初步应用研究

背景与目的:既往主要依靠CT、MRI、SPE/CT、PET检查来判断鼻咽癌(nasopharyngeal carcinoma,NPC)放疗后局部复发、肿瘤残留或全身转移情况,本研究拟探讨脱氧葡萄糖-正电子发射计算机断层(FDG-PET/CT)在判断NPC放疗后局部复发及全身转移中的应用价值.方法:38例NPC均已临床确诊并经放疗后行PET/CT检查,显像时间为放疗后3～36个月,分别观察PET/CT、PET、CT图像,PET以标准摄取值SUV＞2.5定为18F-FDG代谢增高.注射18F-FDG 7.4 MBq/kg后30 min后行脑显像,l h后行全身显像,部分患者行2 h延迟显像.结合CT的形态学特征和PET图像表现将38例患者观察结果分4组:(1)局部无复发、全身无转移;(2)局部有复发全身无转移;(3)局部无复发、全身有转移;(4)局部有复发、全身有转移.所有病例的最后诊断依赖于随访,随访时间6～10个月.结果:PET/CT诊断的敏感性为100%、特异性为89.5%,高于单独PET的100%和80%,明显高于单独CT的77.8%和84.2%.结论:PET/CT对NPC放疗后有无局部复发或肿瘤残留及全身转移的综合判断优于单独CT,略优于单独PET,在判断病灶是否为转移灶时,PET/CT的CT影像能提供重要的参考信息,对指导临床的诊治具有更好的帮助.     

18F-FDG PET/CT在鼻咽癌诊断及分期中的临床价值

背景与目的:PET/CT能够通过准确显示肿瘤形态、大小及相邻关系从而对鼻咽癌(NPC)进行诊断及分期研究.本研究结合PET/CT、MRI结果及部分颈部小淋巴结病理结果,探讨18SF-FDG PET/CT在鼻咽癌TNM分期中的价值.方法:从2005年9月至2007年3月.选取行PET/CT和MRI检查的鼻咽癌患者68例.PET数据采用2D采集模式,CT扫描电压140 kV,采用自动毫安量跟踪扫描加血管增强的扫描方案,18F-FDG按3.7～5.5 MBq/kg剂量静脉注射.MRI检查采用T1W和T2W成像及T1W增强扫描成像.并对其中10例患者颈部小淋巴结切除和穿刺组织病理检查,进行图像与病理对照.结果:68例鼻咽癌患者所有鼻咽区域的病灶PET/CT均可以清晰显示,MRI和PET/CT显示病灶一致:对于直径≤1 cm的138枚PET/CT示阳性小淋巴结,MRI仅有约28%可作不肯定提示.10例鼻咽癌患者颈部16枚PET/CT显示阳性小淋巴结与病理结果相符14枚,符合率达87.5%.对于颈部肿大淋巴结PET/CT.和MRI均能显示,对部分放疗过程PET/CT示增殖活性明显受抑制的肿大淋巴结,MRI和PET/CT增强扫描可见强化.对于其中8例Ⅳb期鼻咽癌患者肺、骨、肝脏等转移灶,PET/CT全身扫描可清晰显示病灶,而MRI具有较多限制.由于18F-FDG PET/CT检查使其中24例的分期进行调整.结论:18F-FDG-PET/CT扫描采用自动毫安量跟踪扫描加血管增强的扫描方案,充分利用PET/CT信息进行鼻咽癌的临床分期,其结果较MRI全面、可靠.     

18F-FDG PET/CT在乳腺癌术后患者复发转移的诊断、治疗中的临床应用价值

目的探讨18F-FDG PET/CT对乳腺癌术后患者复发及转移诊断、治疗中的临床价值。方法收集并回顾性分析行18F-FDG PET/CT检查的94例女性乳腺癌术后患者,病理类型均为浸润性导管癌,年龄为28~79岁。患者均进行18F-FDG PET/CT全身显像,检测结果均应用半定量分析法和目测法判断。分析18F-FDG PET/CT对真阳性患者临床治疗策略的影响。结果18F-FDG PET/CT诊断乳腺癌术后复发转移的灵敏度、特异性、准确度、阳性预测值和阴性预测值分别为96.92%、89.65%、94.68%、91.30%、92.85%。依据18F-FDG PET/CT结果,58.51%真阳性患者最终更改了治疗方案。结论18F-FDG PET/CT能够有效评估乳腺癌术后复发及转移病例并且指导乳腺癌患者的临床治疗。     

18F-FDGPET/CT全身显像对乳腺癌复发和转移诊断价值分析

目的:探讨18F-FDG PET/CT全身显像对治疗后乳腺癌复发和转移的诊断价值。方法:回顾性分析山东省肿瘤医院2004-12-01-2009-12-31行18F-FDG PET/CT显像检查的乳腺癌患者142例,统计18F-FDG PET/CT显像诊断的灵敏度、特异性和准确性,并与增强CT及全身骨扫描进行对比。结果:18F-FDG PET/CT和增强CT对乳腺癌复发和转移的灵敏度分别为85.5%(71/83)和77.1%(64/83),特异性分别为88.1%(52/59)和84.7%(50/59),准确性分别为86.6%(123/142)和80.3%(114/142)。18F-FDG PET/CT诊断淋巴结转移的阳性率为89.5%(34/38),高于增强CT的73.7%(28/38),P=0.031;对于局部复发、肺转移、肝转移和脑转移的诊断,18F-FDG PET/CT和增强CT差异无统计学意义;对于骨转移的诊断,18F-FDG PET/CT的灵敏度为70.0%,全身骨扫描为90.0%,两者的特异性分别为100.0%和58.3%。结论:18F-FDG PET/CT显像对治疗后乳腺癌复发和转移诊断具有较高的灵敏度和特异性,但对于不同部位转移灶的诊断应合理选择检查方法。     

125I粒子植入治疗术中操作者辐射剂量水平分析

  目的  分析和评价125I粒子植入治疗术中不同操作者辐射剂量水平。  方法  用热释光(TLD)元件作为测量工具, 检测参与粒子操作手术的不同操作者(CT引导者、超声引导者、粒子植入者)眼晶状体、操作的手部位和甲状腺部位的辐射剂量水平, 估算眼晶状体、操作的手部位和甲状腺当量剂量。  结果  不同操作者间眼晶状体、操作的手部位和甲状腺当量剂量之间差异无显著统计学意义, 且未超出《电离辐射防护与辐射源安全基本标准》(GB-18871-2002)规定放射工作人员的剂量限值。  结论  参与粒子植入术的不同操作者在本研究的工作强度下, 眼晶状体当量剂量未超过ICRP最新推荐的眼晶状体剂量限值(20mSv), 操作的手部位当量剂量也未超过手部剂量限值(500 mSv)。      

~(18)F-16α-氟雌二醇正电子发射计算机断层显像在晚期雌激素受体阳性乳腺癌诊疗中的初步应用

目的探讨~(18)F-16α-氟雌二醇(~(18)F-FES)正电子发射计算机断层显像(PET/CT)评估晚期乳腺癌患者雌激素受体(ER)状态及预测内分泌疗效的应用价值。方法选取2012年1月至2017年12月间福建省立医院收治的13例晚期乳腺癌患者,对患者行~(18)F-FDG及~(18)F-FES PET/CT显像,对ER+(ER阳性)者行内分泌治疗一个月后再次复查FES PET/CT显像,分析穿刺病灶基线FES最大标准化摄取值(SUVmax)与免疫组化ER表达的相关性,分析病灶基线FES SUVmax值与治疗疗效的关系。结果 13例患者,8例ER+,FES SUVmax (3. 45±2. 10),5例ER-,SUVmax为(0. 88±0. 19),以FES SUVmax> 1. 5为ER阳性,则FES SUVmax诊断乳腺癌病灶ER阳性的敏感度为75. 0%,特异度100. 0%,阳性预测值100. 0%,阴性预测值71. 0%,2例假阴性患者均为ER低表达(1%和5%); 6例ER+患者进行内分泌治疗,PR病例基线FES SUVmax明显高于SD病例,差异有统计学意义(P <0. 05)。结论乳腺癌病灶FES的摄取值与免疫组织化学ER的检测结果具有良好的相关性,病灶基线FES摄取值可预测内分泌治疗的疗效,为晚期乳腺癌个体化治疗提供新的思路。     

^18F-FDG PET及PET/CT在胰腺癌临床应用中的价值

胰腺癌是最常见的消化系统恶性肿瘤之一,早期诊断难度大,预后极差。18F-脱氧葡萄糖（FDG）PET/CT将PET的功能显像与CT的解剖成像有机融合,不仅能有效显示肿瘤的代谢、增生、乏氧和细胞凋亡状态,而且能精确显示肿瘤组织与周围脏器组织的解剖结构关系,探查全身淋巴结及远处转移情况,在胰腺癌患者的诊断、分期、指导治疗、疗效监控和预后评价等方面,PET/CT都具有重要的临床应用价值。本文将就^18F-FDG PET及PET/CT在胰腺癌临床应用中的价值进行综述。     

Siemens Artiste加速器4种图像引导方式的放射剂量学研究

目的 对Artiste加速器image beam line (IBL)模式下2Dplanar、MV CBCT以及6 MV 2Dplanar和Somatom CT图像引导方式放射剂量进行测量,结合患者照射部位选择恰当图像引导方式。方法 利用IBA Dose 1静电计和FC65 指形电离室对头、胸、盆腔仿真模体在2Dplanar、MV CBCT及6 MV 2Dplanar图像引导模式下放射剂量进行测量,用IBA Dosimax plus A 系统测量Somatom CT 头、胸、盆腔扫描模式放射剂量,对测量结果进行分析。结果 在头颈部位,IBL模式 2Dplanar放射平均剂量为16.60 mGy, MV CBCT放射Dmean为58.73 mGy,6 MV 2Dplanar放射Dmean为19.83 mGy,Somatom CT的放射剂量为7~9 mGy;在胸部,IBL模式 2Dplanar放射Dmean为14.08 mGy,MV CBCT放射剂量为49.17 mGy,6 MV 2Dplanar放射Dmean为18.97 mGy,Somatom CT的放射剂量为9~11 mGy;在盆腔部位,IBL模式 2Dplanar放射Dmean为13.36 mGy, MV CBCT放射Dmean为45.65 mGy,6 MV 2Dplanar放射Dmean为17.52 mGy,Somatom CT的放射剂量为12~15 mGy。结论 头颈部,IBL 2Dplanar图像质量已达到配准要求,用IBL 2Dplanar即可;胸部使用Somatom CT进行图像引导较为恰当;盆腔部位,肠腔和膀胱充盈较好时IBL 2DPlanar进行引导即可,充盈欠佳时MV CBCT模式即可满足要求。     

Significantly Low Effective Dose from 18FDG PET/CT Scans Using Dose Reducing Strategies: "Lesser is Better"

Background: Fluorodeoxyglucose (18FDG) PET/CT imaging has become an important component of the management paradigm in oncology. However, the significant imparted radiation exposure is a matter of growing concern especially in younger populations who have better odds of survival. The aim of this study was to estimate the effective dose received by patients having whole body 18FFDG PET/CT scanning as per recent dose reducing guidelines at a tertiary care hospital. Materials and Methods: This prospective study covered 63 patients with different cancers who were referred for PET/CT study for various indications. Patients were prepared as per departmental protocol and 18FDG was injected at 3 MBq/Kg and a low dose, nonenhanced CT protocol (LD NECT) was used. Diagnostic CT studies of specific regions were subsequently performed if required. Effective dose imparted by 18FDG (internal exposure) was calculated by using multiplying injected dose in MBq with coefficient 1.9?102 mSv/MBq according to ICRP publication 106. Effective dose imparted by CT was calculated by multiplying DLP (mGy.cm) with ICRP conversion coefficient "k" 0.015 [mSv / (mG. cm)]. Results: Mean age of patients was 49 18 years with a male to female ratio of 35:28 (56%:44%). Median dose of 18FDG given was 194 MBq (range: 139293). Median CTDIvol was 3.25 (2.46.2) and median DLP was 334.95 (246.70 576.70). Estimated median effective dose imparted by 18FDG was 3.69 mSv (range: 2.855.57). Similarly the estimated median effective dose by low dose (nondiagnostic) CT examination was 4.93 mSv (range: 2.14 10.49). Median total effective dose by whole body 18FDG PET plus low dose nondiagnostic CT study was 8.85 mSv (range: 5.5613.00). Conclusions: We conclude that the median effective dose from a whole body 18FDG PET/CT in our patients was significantly low. We suggest adhering to recently published dose reducing strategies, use of ToF scanner with CT dose reducing option to achieve the lower if not the lowest effective dose. This would certainly reduce the risk of second primary malignancy in younger patients with higher odds of cure from first primary cancer.     

Radiation Dosimetry and Biodistribution of the Hypoxia Tracer (18)F-EF5 in Oncologic Patients

Abstract The primary goals of this study were to determine the biodistribution and excretion of (18)F-EF5 in oncologic patients, to estimate the radiation-absorbed dose and to determine the safety of this drug. Methods: Sixteen patients with histologically confirmed malignancy received a mean intravenous infusion of 217?MBq (range 107-364?MBq) of (18)F-EF5. Over a 4-6-hour period, four to five serial positron emission tomography (PET) or PET/computed tomography (CT) scans were obtained. To calculate the radiation dosimetry estimates, volumes of interest were drawn over the source organs for each PET scan or on the CT for each PET/CT scan. Serial blood samples were obtained to measure (18)F-EF5 blood clearance. Bladder-wall dose was calculated based on urine activity measurements. Results: The urinary bladder received the largest radiation-absorbed dose, 0.12±0.034 mSv/MBq (mean±SD). The average effective dose equivalent and the effective dose of (18)F-EF5 were 0.021±0.003 mSv/MBq and 0.018±0.002 mSv/MBq, respectively. (18)F-EF5 was well tolerated in all subjects. Conclusions: (18)F-EF5 was demonstrated to be safe for patients, and the radiation exposure is clinically acceptable. As with any radiotracer with primary excretion in the urine, the bladder-wall dose can be minimized by active hydration and frequent voiding.     

Dosimetry model for radioactivity localized to intestinal mucosa

BACKGROUND: This paper provides a new model for calculating radiation-absorbed doses to the full thickness of the small and large intestinal walls, and to the mucosal layers. The model was used to estimate the intestinal radiation doses from yttrium-90-labeled-DOTA-biotin binding to NR-LU-10-streptavidin in patients. METHODS: We selected model parameters from published data and observations, and used the model to calculate energy-absorbed fractions using the EGS4 radiation transport code. We determined the cumulated (90)Y activity in the small and large intestines of patients from gamma camera images, and calculated absorbed doses to the mucosal layer and to the whole intestinal wall. RESULTS: The mean absorbed dose to the wall of the small intestine was 16.2 mGy/MBq (60 cGy/mCi) administered from (90)Y localized in the mucosa, and 70 mGy/MBq (260 cGy/mCi) to the mucosal layer within the wall. Doses to the large intestinal wall and to the mucosa of the large intestine were lower than those for the small intestine by a factor of about 2.5. These doses are greater by factors of about 5 to 6 than those that would have been calculated using the standard MIRD models that assume the intestinal activity is in the bowel contents. CONCLUSIONS: The specific uptake of radiopharmaceuticals in mucosal tissues may lead to dose-related intestinal toxicities. Tissue dosimetry at the sub-organ level is useful for a better understanding of intestinal tract radiotoxicity and associated dose-response relationships.     

Results of individual patient dosimetry in peptide receptor radionuclide therapy with 177Lu DOTA-TATE and 177Lu DOTA-NOC

One of the few treatment options for inoperable neuroendocrine tumors (NET) is peptide receptor radiotherapy with somatostatin analogs. In this study, we compared the dosimetric parameter uptake, half-life (kinetics), and mean absorbed organ and tumor doses of (177)Lu DOTA-NOC and (177)Lu DOTA-TATE. METHODS: Ninety-five (95) post-therapeutic dosimetric assessments using (177)Lu DOTA-TATE and 8 using (177)Lu DOTA-NOC in 69 patients with neuroendocrine tumors with high somatostatin receptor expression (verified by Ga-68 DOTA-NOC positron emission tomography/computed tomography) were analyzed. Dosimetric calculations were performed according to the Medical Internal Radiation Dose scheme. RESULTS: (177)Lu DOTA-NOC showed a significantly (p < or = 0.05; sign test) higher uptake for whole-body and normal tissue, as compared to (177)Lu DOTA-TATE, leading to a significant higher whole-body dose of 0.07 mGy/ MBq for DOTA-NOC, as compared to 0.05 mGy/MBq for DOTA-TATE. Renal and spleen uptake and radiation doses were not significantly higher for DOTA-NOC. The uptake in tumor lesions and the mean absorbed tumor dose were higher for DOTA-TATE. The red marrow dose was approximately 0.2 Gy. CONCLUSIONS: Our first results demonstrated that the higher in vitro affinity of DOTA-NOC leads to a higher uptake in normal tissues and, therefore, to an increase in the whole-body dose. The high interpatient variability of these results makes an individual patient dosimetry obligatory.     

Radiation exposure of hemophiliacs after radiosynoviorthesis with 186Re colloid

Very limited data are available in the literature on the doses of unwanted radiation that patients receive following treatment with radiosynoviorthesis (RSO). OBJECTIVE: The aim of this study was to assess the radiation exposure after RSO with (186)Re colloid in hemophiliacs. METHODS: This study involved 12 hemophiliacs who were treated for hemophilic joint disease with 14 RSOs by using (186)Re colloid. Whole-body scintigrams were performed 1, 6, and 24 hours and 3 and 7 days after RSO. Measurements, using a whole-body counter, were done immediately after scintigraphy, with the treated joint protected with a lead shield. The cumulative activity of (186)Re in the body and in the lymph nodes was calculated. The distribution of (186)Re in the body was determined by using the values for small colloids as proposed by the International Commission on Radiological Protection (ICRP) Publication 53. The computer code, OLINDA/EXM (Vanderbilt University, Nashville, TN), was used for the calculation of the internal dose. A constant distance of 1 m between the ankle joint and body organs, and of 0.33 m between the elbow or shoulder joint and body organs, was used to calculate the contribution of gamma radiation to the effective radiation dose. RESULTS: The mean effective dose received by hemophiliacs after RSO with (186)Re colloid was 28 +/- 9 microSv/MBq of the activity injected into the joint. The patients received 0.8-3.7 mSv (1.9 +/- 0.8 mSv) owing to the leakage of (186)Re from the treated joint and its retention in the body. The highest doses were established in the spleen (26.0 +/- 10.7 mGy), the liver (17.6 +/- 7.2 mGy), and red marrow (3.0 +/- 0.8 mGy). The contribution of gamma radiation to the effective dose was less than 0.1 mSv in RSO of the ankle, 0.4 mSv in the elbow, and 0.6 mSv in the shoulder-joint treatment. The activity of (186)Re in the regional lymph nodes was noted in 4 of the 14 treatments. In these cases, the estimated average dose received by individual lymph nodes was 14.7 +/- 1.9 Gy. CONCLUSIONS: RSO with (186)Re colloid is a safe treatment method. The effective dose received by patients after RSO by using (186)Re colloid is low, as are the radiation doses to the most exposed organs. If (186)Re is retained in the regional lymph nodes, the lymph node radiation dose would be high.     

Long-term biokinetics and radiation exposure of patients undergoing 14C-glycocholic acid and 14C-xylose breath tests

The (14)C-glycocholic acid and (14)C-xylose breath tests are clinically used for the diagnosis of intestinal diseases, such as bacterial overgrowth in the small intestine. The two tests have in earlier studies been thoroughly evaluated regarding their clinical value, but due to the long physical half-life of (14)C and the limited biokinetic and dosimetric data, which are available for humans, several hospitals have been restrictive in their use. The aim of this study was to investigate the long-term biokinetics and dosimetry of the two (14)C compounds in patients and volunteers, using the highly sensitive accelerator mass spectrometry (AMS) technique. Eighteen (18) subjects were included, 9 for each compound. The (14)C content in samples from exhaled air, urine, and, for some subjects, also feces were analyzed with both liquid scintillation counting (LSC) and AMS. The results from the glycocholic acid study showed that, up to 1 year after the administration, 67%+/-6% (mean+/-standard deviation) of the administered activity was recovered in exhaled air, 2.4%+/-0.4% was found in urine, and 7.6% (1 subject) in feces. In the xylose study, the major part was found in the urine (66%+/-2%). A significant part was exhaled (28%+/-5%), and the result from an initial 72-hour stool collection from 2 of the subjects showed that the excretion by feces was insignificant. The absorbed dose to various organs and tissues and the effective dose were calculated by using biokinetic models, based on a combination of experimental data from the present study and from earlier reports. In the glycocholic acid study, the highest absorbed dose was received by the colon (1.2 mGy/MBq). In the xylose study, the adipose tissue received 0.8 mGy/MBq. The effective dose was estimated to 0.5 (glycocholic acid) and 0.07 mSv/MBq (xylose). Thus, from a radiation protection point of view, we see no need for restrictions in using the two (14)C-labeled radiopharmaceuticals on adults with the activities normally administered (0.07-0.4 MBq).     

Radiation dose in computed tomography of the pelvis: Comparison of helical and axial scanning

An anthropomorphic Rando phantom was used to compare radiation doses sustained during helical and conventional axial CT of the pelvis. The values obtained with the Rando phantom were validated against cadaveric phantoms, and show good agreement. For the authors’particular CT unit, helical scanning was found to deliver a lower radiation dose than conventional axial scanning. This was most prominent at 1.0-s tube rotation times (average dose ratio 1.24). For realistic scanning parameters and exposure factors, the ratio of radiation dose to pelvic organs can be expected to lie in the range of 40-100 mGy. The whole-body effective dose (ED) depends on selection of scanning parameters and patient anatomy. In a favourable case scenario, the ED for CT scanning of the pelvis in a male can be expected to be between 10 and 20 mSv if the scrotum is not included in the radiation field, while the ED in a female will be ?20 mSv. An examination of scatter radiation fall-off curves from a single slice shows that the spread of scatter radiation is only marginally affected by slice thickness. A total of 10-12 cm of human soft tissue acts as a good barrier against internal scattered radiation. The use of such scatter fall-off curves, together with manufacturers’dosimetry specifications, allows a fast estimate of absorbed dose.     

Biodistribution and dosimetry of (99m)Tc-depreotide (P829) in patients suffering from breast carcinoma

OBJECTIVE: This paper reports on the biodistribution and dosimetry of (99m)Tc-depreotide in patients. METHODS: Whole body planar images were acquired 30 minutes, 1, 2, 4, 9, and 24 hours after intravenous injection of 555-740MBq (99m)Tc-depreotide in 5 breast cancer patients. Urine was collected up to 24 hours after injection, allowing for a calculation of renal clearance and an interpretation of whole body clearance. Time activity curves were generated for the thyroid, lungs, liver, spleen, kidneys, colon, thoracic vertebrae/sternum, and whole body by fitting the organ-specific geometric mean counts, obtained from regions of interest (ROIs). The Medical Internal Radiation Dose (MIRD) formulation was applied to calculate the absorbed radiation dose for various organs. RESULTS: The whole body images show most of the activity distributed in the liver, spleen, and kidneys. Nearly all excretion of activity occurred by the renal system, and hepatobiliary excretion was negligible. Elimination of administered activity occurred predominantly through physical decay. The mean cumulative measured urinary excretion at 24 hours postinjection was 14.0% (standard deviation; 11.8%) of the administered activity. The highest absorbed dose was received by the kidneys, thyroid, and spleen. The average effective dose was estimated to be 1.15E-02mSv/MBq (standard deviation; 1.41E-03mSv/MBq). CONCLUSION: The biodistribution of (99m)Tc-depreotide demonstrated low lung and myocardial uptake allowing early imaging of the supradiaphragmatic region and this with a dosimetry favorable for clinical whole body and single photon emission computed tomography (SPECT) imaging.     

Crypt cell dosimetry for 99Tcm-sestamibi in a new small intestinal dosimetry model

The aim of the study was to calculate the absorbed dose to the crypt cells in the small intestine from (99)Tc(m)-sestamibi excreted through the intestinal tract. The absorbed dose was calculated taking into consideration the biodistribution of the radiopharmaceutical in the small intestinal wall and its contents, based on data gathered in rats. Absorbed dose calculations were performed using a new intestinal model in which S values for crypt cells are given both for the intestinal wall and for the intestinal contents as source organs. A maximum of 6% of the injected activity was found to be located in the intestinal wall at 30 minutes after injection and 13% in the intestinal contents at 2 h, resulting in an absorbed dose of 8.9 microGy/MBq to the crypt cells. Assuming the activity to be located only in the wall, we calculate an absorbed dose to the crypt cells 2.5 times higher than if all the activity is assumed to be present in the intestinal contents. Using the new intestinal dosimetry model, together with detailed biokinetic data for the radiopharmaceutical from animal studies, it is possible to calculate the absorbed dose to the crypt cells, which is not possible when using external imaging.