PET/CT检查中18F-FDG所致辐射剂量的研究

目的 研究在PET/CT检查中18F脱氧葡萄糖(FDG)所致的辐射剂量,使辐射防护更优化.方法 单纯随机法选取30名受检者,记录注射18F-FDG的活度;用451P-DE-DI型电离室巡测仪测量受检者的外照射剂量当量率;在职业人员的不同部位佩戴热释光个人剂量计(TLD),测其累积剂量当量,对有关数据分别进行曲线拟合和直线回归分析.结果 30名受检者注射18F-FDG活度为(432.9±51.8)MBq,有效剂量为(8.23±0.99)mSv;剂量当量率与距离和时间的相关系数(r)值分别为-0.994和-0.988,数据拟合后分别为乘幂曲线和指数曲线;职业人员不同部位TLD所测年累积剂量当量均小于相应的年剂量限值.结论 PET/CT检查中(432.9±51.8)MBq18F-FDG对受检者造成的剂量当量负担较小,但医师在申请检查时应综合考虑受检者的有效剂量;注射18F-FDG后的受检者为活动的辐射源,应从距离防护和时间防护方面对他们的活动稍加约束,减少对其他人员的照射;从医疗照射最优化的角度还可较大程度降低注射18F-FDG的活度.     

PET/CT显像剂18F-氟丙酸在肝癌中的生物学评估

目的 探讨PET/CT显像剂18F-氟丙酸（18F-FPA）对肝细胞肝癌（HCC）的显像效果及其摄取机制。方法 （1）以甲基-2-溴丙酸乙酯为前体合成18F-FPA;（2）通过体外细胞摄取实验测定人肝癌SK-Hep 1细胞不同时间点对18F-FPA的放射性摄取情况;观察不同浓度脂肪酸合成酶抑制剂-奥利司他（Orilistat）、乙酰辅酶A羧化酶抑制剂5-十四烷氧基-2-呋喃甲酸（TOFA）对18F-FPA的摄取抑制情况;（3）对荷人肝癌SK-Hep 1小鼠行18F-FPA microPET/CT显像,并与18F-FDG PET/CT显像进行比较。18F-FPA和18F-FDG在肿瘤中的放射性摄取率比较采用t检验。结果 （1）18F-FPA的合成产率为（45±2）%。（2）细胞摄取实验结果显示,人肝癌SK-Hep 1细胞对18F-FPA的摄取率从5 min的（1.3±0.4）%上升到120 min的（4.6±0.2）%。细胞摄取抑制实验结果显示,随着抑制剂浓度的增高,人肝癌SK-Hep 1细胞对18F-FPA的摄取逐渐降低。当抑制剂奥利司他和TOFA浓度均为400 μmol时,人肝癌SK-Hep 1细胞对18F-FPA的摄取率分别降低了（40.3±4.0）%和（26.0±6.0）%。（3）荷人肝癌SK-Hep 1小鼠18F-FPA microPET/CT显像显示了快速且准确的肿瘤定位,肿瘤/肝脏比值为1.63±0.26;18F-FDG PET/CT显像中的肿瘤/肝脏比值为1.09±0.21。18F-FPA比18F-FDG具有更好的显像效果,差异有统计学意义（t=4.055,P=0.047）。结论18F-FPA可用于肝癌显像,且其摄取与脂肪酸合成有关。     

心肌脂肪酸代谢显像剂18F-FTHA的自动化合成与生物学分布研究

目的实现心肌脂肪酸代谢显像剂14（R,S）-[18F]-氟-6-硫杂十七烷酸（18F-FTHA）的全自动化合成,并评价其在正常昆明小鼠体内的生物学分布特征。方法采用自动化合成模块以苄基-14-（R,S）-对甲苯磺酰基-6-硫代十七烷酸脂为前体合成18F-FTHA。并对其物理（性状、放射性活度、比活度、半衰期和放射性核纯度）、化学（化学纯度、放射化学纯度和室温稳定性）和生物学（毒性、无菌和细菌内毒素）性能进行鉴定。昆明小鼠20只,采用随机数字表法分为4组（每组5只）,经小鼠尾部静脉分别注射18F-FTHA显像剂7.4 MBq（体积 < 0.2 mL）,注射后15、30、60、90 min时各处死1组,分别取心脏、肝脏、脾、肺、肾脏、肌肉和骨等主要器官和血液,称重并测定放射性计数,计算每克组织百分注射剂量率（%ID/g）。组间数据比较采用配对t检验。结果合成时间约50 min,合成产率为（10.0±1.7）%。18F-FTHA注射液为含10%乙醇的无菌、无内毒素、无色澄清透明溶液,pH值为6~7,比活度为65 GBq/mmol,放射性核纯度≥99%,放化纯度>98%。正常昆明小鼠体内生物学分布实验结果显示,18F-FTHA在血液中清除快,心肌摄取高,非靶器官摄取较低。在注射显像剂后60 min时,心肌、肺和肝脏的放射性摄取分别为（19.04±4.87）%ID/g、（3.05±0.52）%ID/g和（5.99±2.96）%ID/g,心肌与肺的摄取比值为6/1（t=0.27,P=0.01）,心肌与肝脏的摄取比值为3/1（t=0.75,P=0.02）,差异均有统计学意义;肝脏摄取呈先高后低的趋势,在15 min和30 min时肝脏摄取略高于心肌摄取。结论实现了18F-FTHA的自动化合成,其放化纯度高,稳定性好。物理、化学和生物学鉴定结果证实其安全可靠,小鼠体内生物学分布实验证实其心肌摄取高于非靶器官,可用于实验研究。     

分化型甲状腺癌患者^131I治疗后体内残留放射性活度的评估

目的 评估分化型甲状腺癌（DTC）患者^131I治疗后体内残留放射性活度.方法 本研究共纳入了35例DTC患者,分为“清甲”（20例）与“清灶”（15例）组,分别于服^13I后2、6、24、48、72 h进行^131I全身显像及1m处当量剂量率的测定,以2h时显像计数和活度作为总计数和总活度.根据各时间点显像计数与2h的显像计数比值间接估算体内残留放射性活度,并估算患者体内残留放射性活度达到400 MBq时的1m处当量剂量率.统计学分析采用直线相关与回归分析.结果 “清甲”组服^131I后2、6、24、48、72 h体内残留^131I活度占服^131I总活度的百分比分别为99％±4％、86％±6％、35％±10％、12％±8％、7％±8％, “清灶”组分别为99％±1％、91％±7％、47％±17％、11％±9％、4％±6％. “清甲”组服^131I后2、6、24、48、72 h的1m处当量剂量率分别为（157±37）、（120±36）、（35±13）、（11±9）、（9±11）μSv/h,“清灶”组分别为（234±43）、（186±51）、（49±20）、（12±11）、（4±6）μSv/h.体内残留的放射性活度与1m处当量剂量率呈正相关（r=0.87,P＜0.001）.“清甲”与“清灶”组服^131I后48、72 h体内残留放射性活度分别为（432±292）、（265±281） MBq及（731±701）、（277±470） MBq,对应的1m处当量剂量率为8～ 11 μSv/h.结论 DTC患者服^131I后48～72 h体内残留放射性活度达到国家标准规定的400 MBq时,即DTC患者1m处当量剂量率达到8～11 μSv/h时方可出院.     

18F-FDG和99Tcm-MDP显像诊断多发性骨髓瘤骨病的对比研究

目的 对比研究18F-FDG PET/CT和99Tcm-亚甲基二膦酸盐（99Tcm-MDP）SPECT全身骨显像对多发性骨髓瘤骨病（MBD）的诊断价值。 方法 回顾性分析2015年4月至2018年5月在安徽医科大学附属安庆医院经临床确诊的29例多发性骨髓瘤初治患者,其中,男性18例、女性11例,年龄39~81（60.14±10.41）岁。所有患者均于两周内先后行18F-FDG PET/CT显像及99Tcm-MDP SPECT全身骨显像,对比分析18F-FDG PET/CT和99Tcm-MDP SPECT显像检出的骨异常改变,对两种显像方法检出MBD例数的比较采用配对资料的χ2检验。 结果 29例多发性骨髓瘤患者均伴发MBD,18F-FDG PET/CT显像阳性者28例（骨骼局灶型摄取显像剂18例,弥漫型骨髓摄取1例,混合型摄取9例）,99Tcm-MDP SPECT骨显像阳性21例（表现为骨骼单发或多发放射性浓聚灶）,阳性符合率分别为96.6%（28/29）和72.4%（21/29）,差异有统计学意义（χ2=5.0,P<0.05）。 结论 18F-FDG PET/CT显像比99Tcm-MDP SPECT全身骨显像对MBD的探测更为灵敏,且对骨髓浸润及髓外侵犯亦具有良好的诊断效能。     

骨转移癌患者对~(186)Re-HEDP和~(153)Sm-EDTMP的骨摄取和软组织滞留

目的 :利用改良骨扫描技术测定用 1 86　 Re- 1-羟基 - 1-亚乙基 - 1,1-二膦酸盐 (1 86　 Re- HEDP)和 1 53 　 Sm -乙二胺四甲撑膦酸盐 (1 53 　 Sm- EDTMP)治疗后的骨转移癌患者对这两种放射性药物的骨组织摄取和软组织滞留。方法 :将 2 9例恶性肿瘤多发骨转移患者分两组 ,分别给予 1 86　 Re- HEDP12 95 MBq和 1 53　 Sm- EDTMP37MBq/ kg弹丸式注射 ,治疗后 3min、3h、2 4h和 72 h进行前后位全身骨扫描 ,用感兴趣区技术测量全身、膀胱和双侧大腿内收肌的放射性活度。软组织残留放射性活度 (t) =全身总活度 (3m in)×双侧内收…     

11C-胆碱和18F-FDG PET/CT显像在脑胶质瘤诊断中的应用

目的 探讨11C-胆碱和18F-FDG PET/CT在脑胶质瘤显像中的意义,以提高PET/CT对脑胶质瘤病变的诊断价值。 方法 分别对21例颅脑占位疑似脑胶质瘤患者行11C-胆碱及18F-FDG PET/CT颅脑显像,分析11C-胆碱和18F-FDG最大标准化摄取值（SUV_max）与患者年龄、病理类型之间的关系。 结果 21例患者的18F-FDG和11C-胆碱SUV_max与患者年龄无显著相关性,18F-FDG SUV_max与病变的良、恶性也无显著相关性,而11C-胆碱SUV_max与病变良、恶性存在一定相关性。 结论 11C-胆碱PET/CT在诊断和鉴别颅内胶质瘤病变中具有重要的价值和意义。     

18F-FDG PET/CT检测淋巴结转移性鳞癌原发灶的价值

目的 探讨18F-氟脱氧葡萄糖（FDG） PET/CT在淋巴结转移性鳞癌原发灶检测中的临床应用价值。 方法 选取2018年3月至2020年11月于广东省佛山市禅城区中心医院因发现淋巴结转移性鳞癌而原发灶不明行全身18F-FDG PET/CT检查的56例患者进行回顾性研究,其中男性44例、女性12例,年龄19~81岁,中位年龄51岁。所有患者的淋巴结转移性鳞癌均于18F-FDG PET/CT显像前经组织病理学检查确诊,原发灶经组织病理学检查或临床随访确诊。分析并计算18F-FDG PET/CT检测原发灶的检出率;原发灶与淋巴结转移部位、最大标准化摄取值（SUV_max）的关系。采用双变量相关分析法分析原发灶与淋巴结转移灶的SUV_max的相关性。 结果 56例患者中,18F-FDG PET/CT检测原发灶阳性44例（真阳性42例、假阳性2例）,检出率为75.0%;假阴性1例（鼻咽癌）;11例患者18F-FDG PET/CT未发现原发灶。双变量相关分析结果显示,原发灶与淋巴结转移灶的SUV_max在一定程度上具有一致性（r=0.320,P<0.05）。 结论 18F-FDG PET/CT显像对淋巴结转移性鳞癌的不明原发灶检测具有较好的临床应用价值,淋巴结转移灶与原发灶的18F-FDG代谢强度存在良好的相关性。     

乳腺癌18F-FDG PET/CT和3.0T MRI联合显像评分与Ki-67表达水平的相关性分析

目的 探讨18F-FDG PET/CT和3.0T MRI联合显像评分与Ki-67（一种增殖细胞核抗原）表达水平的相关性。 方法 18例经病理确诊的原发性乳腺癌患者术前行18F-FDG PET/CT和3.0T MRI联合显像,对显像结果进行评分并与Ki-67的表达水平进行相关性分析。联合显像和术后病理标本的免疫组化检测在一周内完成。 结果 ① 乳腺癌最大标准化摄取值与Ki-67的表达水平呈正相关（r=0.473,P＜0.05）;②PET/CT和3.0T MRI联合显像评分与Ki-67的表达水平呈明显正相关（r=0.674,P＜0.01）。 结论 18F-FDG PET/CT和3.0T MRI联合显像在乳腺癌的预后判断中可能具有重要的潜在价值。     

淋巴瘤细胞株Raji摄取18F-氟脱氧葡萄糖和18F-氟脱氧胸腺嘧啶核苷的体外实验研究

目的研究测定人淋巴瘤细胞株Raji摄取18F-氟脱氧葡萄糖（18F—FDG）和18F-氟脱氧胸腺嘧啶核苷（18F—FLT）的方法并比较两者的差异。方法在不同条件下测定淋巴瘤细胞株Raji对18F—FDG和18F—FLT的细胞结合率：细胞数量1×10^5-1×10^7/瓶;18F-FDG和18F—FLT的放射性活度1．85—29．6kBq;反应时间20—120min;葡萄糖浓度0～11．1mmol／L。结果每瓶1×10^7个细胞、加入3．7kBq18F．FDG、葡萄糖浓度在0—2．78mmol／L、作用100min,18F-FDG细胞结合率达到（50．42×1．07）％;每瓶1×10^7个细胞、加入3．7kBq 18F—FLT、作用100min,18F—FLT细胞结合率达到（59．48±0．77）％;18F—FDG和18F-FLT的细胞结合率之间具有统计学差异（F=1192．805,P〈0．001）。结论Raji细胞与18F—FDG的结合率与细胞数量、作用时间及葡萄糖浓度有关,与18F-FDG的放射性活度无关;Raji细胞与18F-FLT的结合率与细胞数量和作用时间有关,与18F-FLT的放射性活度及葡萄糖浓度无关;同等条件下,Raji细胞对18F-FLT的细胞结合率高于18F—FDG。     

Adsorption of technetium-99m tetrofosmin and technetium-99m furifosmin on plastic syringes

Some groups have reported that adsorption of radiopharmaceuticals on disposable plastic syringes can reach levels of almost 50%. This high loss of radioactivity stimulated us to carry out similar studies. Our measurements were done in combination with patient studies. Therefore, we used 2-ml syringes, all of the same brand. The radioactivity in the syringe was measured immediately before and after injection. a total of 500–600 MBq technetium-99m labelled tetrofosmin or technetium-99m furifosmin was administered to 48 patients using four different injection techniques (n = 6 for each technique with each tracer): with needles, 1 min blood incubation at 22°C, 10 or 30 min after preparation of the tracer; with butterflies, 1 min blood incubation at 22°C, 10 or 30 min after preparation of the tracer. Neither in syringes nor in needles or butterflies did more than 7% of the initial radioactivity remain. The entire residual activity in syringe plus needle or syringe plus butterfly together never exceeded the 9% limit. Furthermore, in a pilot study we measured the remaining radioactivity in the vial; here, too, we found no more than 14% of total radioactivity. These findings indicate that total retention of radioactivity during elution and application of ^99mTc-tetrofosmin and ^99mTc-furifosmin with material used in our setting does not approach relevant amounts. Received 6 May and in revised form 19 May 1998     

Validation of a new protocol for 18F-FDG infusion using an automatic combined dispenser and injector system

Purpose

In nuclear medicine, radiopharmaceuticals are usually administered in unit doses partitioned from multi-dose vials. The partitioning typically takes place in a radiopharmacy, depending on local practice. Automatic, as opposed to manual, partitioning and administration should reduce radiation exposure of the personnel involved, improve the accuracy of the administration and mitigate contamination. This study set out to verify and validate the ¹⁸F-fluorodeoxyglucose (FDG) administration procedure performed using Intego? (MEDRAD, Inc., Warrendale, PA, USA), a combined dispenser and injector system. We considered maintenance of sterility and the system’s potential to improve, with respect to the manual procedure, the accuracy of net administered ¹⁸F-FDG radioactivity in patients and the radiation protection of operators.

Methods

A media-fill procedure was used to assess whether sterility is maintained during use of the Intego? system. Simulating a typical working day’s setup and use of the system, we investigated the accuracy of the net administered ¹⁸F-FDG activity obtained with Intego? versus the manual dose delivery system. We also measured personnel radiation exposure during use of Intego? and during manual administration and recorded and compared environmental doses in the two conditions.

Results

The radiopharmaceutical remained sterile in all the tests performed. The accuracy of the net ¹⁸F-FDG activity delivered to the patients was found to be within 3?% points, as required by European Association of Nuclear Medicine (EANM) guidelines on ¹⁸F-FDG imaging procedures. With Intego?, the residual radioactivity in the tubing was 0.20?MBq, corresponding to approximately 0.07?% of the mean activity delivered. With manual injection, the residual radioactivity in the syringe averaged 7.37?MBq, corresponding to a mean error of 2.9?% in the delivered dose. During the injection step of the positron emission tomography (PET) procedure, whole-body and extremity radiation exposures were significantly reduced with Intego? by 38 and by 94?%, respectively, compared to the levels associated with manual administration (p?<?0.05).

Conclusion

Intego?accurately partitions and administers sterile doses of ¹⁸F-FDG from multi-dose vials. Compared with standard manual ¹⁸F-FDG administration, the new procedure with an automatic dispensing and injection system greatly reduces the extremity dose to the operator involved in the administration of the radiopharmaceutical.     

Development of 18F-FDG ([F-18]-2-fluoro-2-deoxy-D-glucose) injection for imaging of tumor reflecting glucose metabolism--results of preclinical studies]

Fluorine-18-2-fluoro-2-deoxy-D-glucose (18F-FDG) injection was prepared by a modification of a method originally developed by Hamacher et al. The dosage form is the injectable solution (2 ml) containing 185 MBq of 18F-FDG at a calibration time. Preclinical studies of the agent were performed. Its radiochemical purity is more than 95% and expiration time is 4 hours after the calibration time at ambient temperature. No toxicity was observed with up to 200 mg/kg and 100 mg/kg of non-radioactive FDG intravenously injected to rats and dogs in single-dose toxicity tests, respectively. Biodistribution studies demonstrated that the radioactivity was mainly distributed into brain (3.0 to 3.3% I.D./Organ at 30 minutes) and heart (4.2 to 5.8% I.D./Organ at 1 to 3 hours) after intravenous injection of the agent to normal rats. In a tumor transplanted mouse model (colon 26), tumor uptake was 10.9 +/- 3.5% I.D./g at 1 hr after intravenous injection of the agent, the radioactivity was retained until 3 hours. The radiation absorbed dose was estimated according to the MIRD Pamphlet based on the biodistribution data both in humans reported by Mejia et al. and rats described in this report. The radiation absorbed dose was not higher than those of commercially available radiopharmaceuticals. In conclusion, the 18F-FDG injection is expected to be useful for further clinical application.     

Proposed addendum to previously published fetal dose estimate tables for 18F-FDG.

Placental transfer and fetal dose estimates have been published for women in early pregnancy and at the end of each trimester for a large number of radiopharmaceuticals. For the case of (18)F-FDG, a dose was given with no information about placental transfer of the radiopharmaceutical. Recent publications have reported quantitative values for maternal and fetal uptake of (18)F-FDG in primates and new values for (18)F-FDG kinetics. In this article, these data are applied to give radiation dose estimates for the fetus at all stages of pregnancy for (18)F-FDG. The recommended values are 2.2 x 10(-2) mGy/MBq in early pregnancy, 2.2 x 10(-2) mGy/MBq at 3-mo gestation, 1.7 x 10(-2) mGy/MBq at 6-mo gestation, and 1.7 x 10(-2) mGy/MBq at 9-mo gestation.     

Adsorption of radiopharmaceuticals to syringes: setting up a reliable protocol for its assessment

BACKGROUND: It is well known that various drugs, including radiopharmaceuticals, may adsorb to plastic syringes to different extents. Some reports suggest that adsorption can reach levels of almost 50%. The consequence of adsorption of a radiopharmaceutical and subsequent inadequate dosing can include an inappropriate diagnostic response in patients, an increase in the duration of investigation or treatment, and an increase in cost. AIM: To investigate the extent of adsorption of Tc-succimer to plastic syringes and to set up a reliable protocol for assessment of the extent of retention of drugs to single-use plastic syringes before a new syringe brand and/or radiopharmaceutical are introduced in a nuclear medicine department. METHODS: Radiopharmaceutical kits from two different manufacturers were compared for retention using syringes from three different producers. To assess the influence of dilution on retention, Tc-succimer preparations were further diluted with sodium chloride solution for injection. Syringes were filled to one-third of their capacity and incubated at room temperature before being emptied into vacuum vials. The radioactivity of the syringes was measured before and after emptying. The extent of retained radioactivity was calculated as a percentage of radioactivity in the syringe before emptying. RESULTS: Results show that adsorption of Tc-succimer considerably differs between syringe brands. The adsorption of undiluted Tc-succimer in 30 min may exceed 50%. CONCLUSION: The findings show that measurement of retention in syringes and injection sets should be regarded as an essential aspect of quality assurance before radiopharmaceuticals, syringes and injection sets are used routinely.     

Influence of thyroid-stimulating hormone on 18F-fluorodeoxyglucose and 99mTc-methoxyisobutylisonitrile uptake in human poorly differentiated thyroid cancer cells in vitro

Objective  In poorly differentiated thyroid cancer originating from thyroid follicular cells, the ability to concentrate iodine is lost. This makes recurrence undetectable by ¹³¹I whole-body scan. In this situation, other radiopharmaceuticals, such as ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) and technetium-99m-methoxyisobutylisonitrile (^99mTc-MIBI), are used to evaluate recurrence or metastasis. Some reports suggest that ¹⁸F-FDG uptake is increased by thyroid-stimulating hormone (TSH) stimulation. This study aimed to determine the influence of TSH on ¹⁸F-FDG and ^99mTc-MIBI uptake in human poorly differentiated thyroid cancer cells in vitro. Materials and methods  The cells were stimulated with 1000 μU/ml of recombinant human thyroid-stimulating hormone (rhTSH) for 1 day, 3 days, and 5 days. Each cell was incubated with 0.5 MBq/ml-1 MBq/ml of ¹⁸F-FDG or 0.5 MBq/ml-1 MBq/ml of ^99mTc-MIBI for 1 h at 37°C. The uptake of each radiopharmaceutical in the cells was quantified as a percent of whole radioactivity per total viable cell number. The quantification of glucose transporter 1, 2, 3 and 4 mRNA expression was measured using RT-PCR. Results  TSH stimulation increased ¹⁸F-FDG uptake in a time-dependent manner. Following 5 days of rhTSH stimulation, ¹⁸F-FDG uptake was approximately 2.2 times that of the control. The increase in ¹⁸F-FDG uptake following rhTSH stimulation was correlated to the increase in GLUT4 mRNA level. The GLUT1 mRNA level was unchanged. An increased uptake of ^99mTc-MIBI was observed with a pattern similar to that of ¹⁸F-FDG. The ^99mTc-MIBI uptake was approximately 1.5 times that of the control 5 days later. Conclusions  These results suggest that TSH stimulates ¹⁸F-FDG and ^99mTc-MIBI uptake in poorly differentiated papillary thyroid cancer, and therefore ¹⁸F-FDG-PET or ^99mTc-MIBI scans under TSH stimulation may be more accurate than under suppression.     

Comparison of sigma-ligands and metabolic PET tracers for differentiating tumor from inflammation.

Novel radiopharmaceuticals for the detection of tumors and their metastases may be of clinical interest if they are more tumor selective than (18)F-FDG. Increased glucose metabolism of inflammatory tissues is the main source of false-positive (18)F-FDG PET findings in oncology. METHODS: We compared the biodistribution of 4 PET tracers (2 sigma-receptor ligands, (11)C-choline, and (11)C-methionine) with previously published biodistribution data of 3'-deoxy-3'-(18)F-fluorothymidine ((18)F-FLT) and of (18)F-FDG in the same animal model. The model consisted of male Wistar rats that bore tumors (C6 rat glioma in the right shoulder) and also had sterile inflammation in the left calf muscle (induced by injection of 0.1 mL of turpentine). Twenty-four hours after turpentine injection, the rats received an intravenous bolus of PET tracer (approximately 30 MBq in the case of (18)F and 74 MBq for (11)C). RESULTS: (18)F-FDG showed the highest tumor-to-muscle ratio of all radiopharmaceuticals (13.2 +/- 3.0, mean +/- SD), followed at a large distance by the sigma-1 ligand (11)C-SA4503 (5.1 +/- 1.7), (18)F-FLT (3.8 +/- 1.3), the non-subtype-selective sigma-ligand (18)F-FE-SA5845 (3.3 +/- 1.5), (11)C-choline (3.1 +/- 0.4), and (11)C-methionine (2.8 +/- 0.3). sigma-Ligands and (18)F-FLT were relatively tumor selective ((18)F-FE-SA5845, greater than 30-fold; (11)C-SA4503 and (18)F-FLT, greater than 10-fold). The tumor selectivity of (11)C-methionine was only slightly better than that of (18)F-FDG. (11)C-Choline showed equal uptake in tumor and inflammation. All tracers were avidly taken up by proliferative tissue (small intestine, bone marrow). High physiologic uptake of some compounds was observed in brain, heart, lung, pancreas, spleen, and salivary gland. CONCLUSION: sigma-Ligands and (18)F-FLT were more tumor selective than (18)F-FDG, (11)C-choline, or (11)C-methionine in our animal model. However, these novel radiopharmaceuticals were less sensitive than were the established oncologic tracers.     

Evaluation of optimized injection dose and acquisition time using body mass index for three-dimensional whole-body FDG-PET

OBJECTIVE: The standardized uptake value (SUV) is a relative measure of tracer uptake in tissue used in (18)F-FDG PET. However, the quality of ordered subset expectation maximization (OS-EM) images is sensitive to the number of iterations, because a large number of iterations leads to images with checkerboard noise. The main advantage of data acquisition in the three-dimensional (3D) mode is the high sensitivity to better exploit the intrinsic spatial resolution and the lower injection dose given to patients. In the 3D mode, the scatter fraction is higher, and, for a given administered dose, the random fraction is higher than that in the two-dimensional mode, which implies that correction methods need to be more accurate. Moreover, in clinical oncology (18)F-FDG PET studies, patients have a wide variety of body shapes and sizes, which may impact image statistics. Consequently, it is necessary to make constant the acquisition (true) counts. The purpose of this study was to optimize injection dose and acquisition time in consideration of body mass index (BMI) for 3D whole-body (18)F-FDG PET. METHODS: A dedicated PET scanner, SIEMENS ECAT EXACT HR(+), was used to scan images of clinical data. The injection dose for BMI of <14-19, 19-22, 22-25, and 25< (kg/m(2)) were, 92.5 MBq, 111.0 MBq, 129.5 MBq, and 148.0 MBq, respectively. The emission scan time per bed position for BMI of <14-19, 19-22, 22-25, and >25 (kg/m(2)) were, 120, 120, 180, and 240 sec, respectively. A total of 20 patient subjects were evaluated as to true counts per bin (T/bin) of sinogram data and measured activity concentrations for the region of interest in the liver section. RESULTS: T/bin was stable using an optimized protocol that took into consideration the BMI for any type of body morphology. The overall coefficient of variation was 7.27% for radioactivity concentration. Additionally, Gaussian filtering (8 mm FWHM) after reconstruction by the OS-EM method provided stable SUV values even when the iteration number was increased 30 times over. CONCLUSION: Optimization of injection dose and acquisition time indicated that BMI was a clinically useful acquisition protocol for 3D whole-body (18)F-FDG PET.     

Technologist radiation exposure in routine clinical practice with 18F-FDG PET

OBJECTIVE: The use of 18F-FDG for clinical PET studies increases technologist radiation dose exposure because of the higher gamma-radiation energy of this isotope than of other conventional medical gamma-radiation-emitting isotopes. Therefore, 18F-FDG imaging necessitates stronger radiation protection requirements. The aims of this study were to assess technologist whole-body and extremity exposure in our PET department and to evaluate the efficiency of our radiation protection devices (homemade syringe drawing device, semiautomated injector, and video tracking of patients). METHODS: Radiation dose assessment was performed for monodose as well as for multidose 18F-FDG packaging with both LiF thermoluminescence dosimeters (TLD) and electronic personal dosimeters (ED) during 5 successive 18F-FDG PET steps (from syringe filling to patient departure). RESULTS: The mean +/- SD total effective doses received by technologists (n = 50) during all of the working steps were 3.24 +/- 2.1 and 3.01 +/- 1.4 microSv, respectively, as measured with ED and TLD (345 +/- 84 MBq injected). These values were confirmed by daily TLD technologist whole-body dose measurements (2.98 +/- 1.8 microSv; 294 +/- 78 MBq injected; n = 48). Finger irradiation doses during preparation of single 18F-FDG syringes were 204.9 +/- 24 and 198.4 +/- 23 microSv with multidose vials (345 +/- 93 MBq injected) and 127.3 +/- 76 and 55.9 +/- 47 microSv with monodose vials (302 +/- 43 MBq injected) for the right hand and the left hand, respectively. The protection afforded by the semiautomated injector, estimated as the ratio of the doses received by TLD placed on the syringe shield and on the external face of the injector, was near 2,000. CONCLUSION: These results showed that technologist radiation doses in our PET department were lower than those reported in the literature. This finding may be explained by the use of a homemade syringe drawing device, a semiautomated injector, and patient video tracking, allowing a shorter duration of contact between the technologist and the patient. Extrapolation of these results to an annual dose (4 patients per day per technologist) revealed that the annual extrapolated exposure values remained under the authorized limits for workers classified to work in a radioactivity-controlled area.     

Retro-orbital injection is an effective route for radiopharmaceutical administration in mice during small-animal PET studies

BACKGROUND AND AIM: Small-animal PET is acquiring importance for pre-clinical studies. In rodents, radiotracers are usually administrated via the tail vein. This procedure can be very difficult and time-consuming as soft tissue extravasations are very frequent and tail scars can prevent repeated injections after initial failure. The aim of our study was to compare the retro-orbital (RO) versus tail vein intravenous (i.v.) administration of (18)F-FDG and (11)C-choline in mice for small-animal PET studies. METHODS: We evaluated four healthy female ICR CD1 mice according to the following protocol. Day 1: each animal underwent an i.v. injection of 28 MBq of (11)C-choline. PET scan was performed after 10 min and 40 min. Day 2: each animal received an RO injection of 28 MBq of (11)C-choline. A PET scan was performed after 10 min and 40 min. Day 3: each animal received an i.v. injection of 28 MBq of (18)F-FDG. A PET scan was performed after 60 min and 120 min. Day 4: each animal received an RO injection of 28 MBq of (18)F-FDG. A PET scan was performed after 60 min and 120 min. Administration and image acquisition were performed under gas anaesthesia. For FDG studies the animals fasted for 2 h and were kept asleep for 20-30 min after injection, to avoid muscular uptake. Images were reconstructed with 2-D OSEM. For each scan ROIs were drawn on liver, kidneys, lung, brain, heart brown fat and muscles, and the SUV was calculated. We finally compared choline i.v. standard acquisition to choline RO standard acquisition; choline i.v. delayed acquisition to choline RO delayed acquisition; FDG i.v. standard acquisition to FDG RO standard acquisition; FDG i.v. delayed acquisition to FDG RO delayed acquisition. RESULTS: The RO injections for both (18)F-FDG and (11)C-choline were comparable to the intravenous injection of F-FDG for the standard and delayed acquisitions. CONCLUSION: The RO administration in mice represents a technical advantage over intravenous administration in being an easier and faster procedure. However, its use requires high specific activity while its value in peptides and other receptor-specific radiopharmaceuticals needs further assessment.