Biokinetics and radiation doses for carbon-14 urea in adults and children undergoing the Helicobacter pylori breath test

The long-term biokinetics and dosimetry of carbon-14 were studied in nine adults and eight children undergoing carbon-14 urea breath test for Helicobacter pylori (HP) infection. The elimination of ¹⁴C via exhaled air and urine was measured with the liquid scintillation counting technique and with accelerator mass spectrometry. After the subjects had been given 110 kBq ¹⁴C-urea (children: 55 kBq) orally, samples of exhaled air were taken up to 180 days after administration and samples of urine were collected up to 40 days. Sixteen of the subjects were found to be HP-negative. In these subjects a total of 91.1%±3.9% (mean of adults and children ± standard error of the mean) of the administered ¹⁴C activity was recovered. The majority of the administered activity, 88.3%±6.2% in adults and 87.7%±5.0% in children, was excreted via the urine within 72 h after administration. A smaller fraction was exhaled. In adults 4.6%±0.6% of the activity was exhaled within 20 days and in children 2.6%±0.3%. Uncertainties in the biokinetic results are mainly due to assumptions concerning endogenous CO₂ production and urinary excretion rate and are estimated to be less than 30%. The absorbed dose to various organs and the effective dose were calculated using the ICRP model for urea and CO₂. The urinary bladder received the highest absorbed dose: in adults, 0.15±0.01 mGy/MBq and in children of various ages (7–14 years), 0.14–0.36 mGy/MBq. The findings indicate that an investigation with ¹⁴C-urea gives an effective dose to adults of 2.1±0.1 μSv (for 110 kBq) and to children of 0.9–2.5 μSv (for 55 kBq). From a radiation protection point of view, there is thus no reason for restrictions on even repeated screening investigations with ¹⁴C-urea in whole families, including children. Received 27 October 1998 and in revised form 13 January 1999     

Biokinetics and radiation doses for carbon-14 urea in adults and children undergoing the Helicobacter pylori breath test.

The long-term biokinetics and dosimetry of carbon-14 were studied in nine adults and eight children undergoing carbon-14 urea breath test for Helicobacter pylori (HP) infection. The elimination of 14C via exhaled air and urine was measured with the liquid scintillation counting technique and with accelerator mass spectrometry. After the subjects had been given 110 kBq 14C-urea (children: 55 kBq) orally, samples of exhaled air were taken up to 180 days after administration and samples of urine were collected up to 40 days. Sixteen of the subjects were found to be HP-negative. In these subjects a total of 91.1%+/-3.9% (mean of adults and children +/- standard error of the mean) of the administered 14C activity was recovered. The majority of the administered activity, 88.3%+/-6.2% in adults and 87.7%+/-5.0% in children, was excreted via the urine within 72 h after administration. A smaller fraction was exhaled. In adults 4.6%+/-0.6% of the activity was exhaled within 20 days and in children 2.6%+/-0.3%. Uncertainties in the biokinetic results are mainly due to assumptions concerning endogenous CO2 production and urinary excretion rate and are estimated to be less than 30%. The absorbed dose to various organs and the effective dose were calculated using the ICRP model for urea and CO2. The urinary bladder received the highest absorbed dose: in adults, 0.15+/-0.01 mGy/MBq and in children of various ages (7-14 years), 0.14-0.36 mGy/MBq. The findings indicate that an investigation with 14C-urea gives an effective dose to adults of 2.1+/-0.1 microSv (for 110 kBq) and to children of 0.9-2.5 microSv (for 55 kBq). From a radiation protection point of view, there is thus no reason for restrictions on even repeated screening investigations with 14C-urea in whole families, including children.     

^14C—尿素呼气试验对胃幽门螺杆菌感染的诊断价值

目的建立１４Ｃ尿素呼气试验，评价其临床应用价值。方法胃镜下取胃窦粘膜作细胞培养及病理切片，染色阳性为幽门螺杆菌（Ｈｐ）感染的对比指标。对１３８４例临床怀疑为胃及十二指肠疾病的患者进行呼气试验，其中４４例行多时相动态呼气试验，以确定最佳集气时间。结果动态检测示３０分钟为１４Ｃ呼气量峰值，如将Ｈｐ阳性阈值定于呼气比值大于３５，则１４Ｃ呼气试验对Ｈｐ感染检出的灵敏度为９６７％，特异性为９６５％。１４Ｃ呼气试验在成人人群中的阳性率为５０４％，在儿童中为８１２％。结论１４Ｃ呼气试验在胃肠道Ｈｐ感染检测中具有良好的灵敏度及特异性，方法简便可靠，易于临床推广     

14C-尿素呼气试验诊断幽门螺杆菌感染的价值

 目的 探讨正常人群和慢性胃炎及消化性溃疡患者幽门螺杆菌(Hp)感染情况.方法 3 497例健康体检者和638例慢性胃炎和消化性溃疡患者行14C-尿素呼气试验(14C -Urea breath test,14C-UBT)Hp检测.计算机自动得出数据,2 min计数(dpm)＜100 dpm 为正常,即Hp阴性;＞101 dpm为异常,即Hp阳性.结果 健康体检3 497例,Hp阳性1 748例,阳性率50 %,发现胃癌1例(14C-UBT 1 200 dpm);慢性胃炎及消化性溃疡组638例,Hp阳性339例,阳性率53%.两组相比差异无统计学意义(P＞0.05).但是,健康体检组阳性者中＞601 dpm占41.2%(720/1748);慢性胃炎和消化性溃疡组阳性者中＞601dpm占38.3%(131/339).两组相比差异有统计学意义(P＜0.05).结论 在健康人群中存在有较高比例的Hp感染趋向,14C-UBT检测Hp的优点是简便、准确、安全、无创、经济、重复性好.     

The impact of brushing teeth on carbon-14 urea breath test results

OBJECTIVE: The 14C urea breath test noninvasively detects the presence of the urease-producing bacteria Helicobacter pylori in the stomach. Several sources of errors have been identified to cause false or indeterminate results on the test. The objective of this study was to identify whether brushing teeth affects the test results. METHODS: We performed the 14C urea breath test on 168 patients, with breath samples counted at 10 and 20 min after oral administration of 2 microCi (74 kBq) 14C urea. Ninety-four patients brushed their teeth before the test while 74 did not. RESULTS: Thirty-six of the 74 patients (49%) who did not brush their teeth had positive results at 10 min, which became negative at 20 min. None of the 94 patients who brushed their teeth before testing showed this pattern with agreement of results at 10 and 20 min. CONCLUSION: We recommend brushing teeth before the 14C urea breath test since it significantly decreased the ambiguous results of the test in our laboratory.     

Carbon-14 urea breath test for the diagnosis of Campylobacter pylori associated gastritis

Urease in the human gastric mucosa is a marker for infection with Campylobacter pylori (CP), an organism suspected of causing chronic gastritis and peptic ulceration. To detect gastric urease, we examined 32 patients who were being evaluated for possible peptic ulcer disease. Fasting patients were given 10 microCi (370 kBq) of 14C-labeled urea. Breath samples were collected in hyamine at intervals between 1 and 30 min. The amount of 14C collected at these times was expressed as: body weight X (% of administered dose of 14C in sample)/(mmol of CO2 collected). The presence of C. pylori colonization was also determined by examination of multiple endoscopic gastric biopsy specimens. On average, patients who were proven to have C. pylori infection exhaled 20 times more labeled CO2 than patients who were not infected. The difference between infected patients and C. pylori negative "control" patients was highly significant at all time points between 2 and 30 min after ingestion of the radionuclide (p less than 0.0001). The noninvasive urea breath is less expensive than endoscopic biopsy of the stomach and more accurate than serology as a means of detecting Campylobacter pylori infection. Because the test detects actual viable CP organisms, it can be used to confirm eradication of the bacterium after antibacterial therapy.     

Biokinetics and radiation dosimetry for patients undergoing a glycerol tri[1-14C]oleate fat malabsorption breath test.

The glycerol tri[1-14C]olein test for fat malabsorption was carried out in two male volunteers and measurements of the loss of 14C in expired air, urine and faeces and the retention of 14C in biopsy samples of abdominal fat were made using accelerator mass spectrometry. Exhalation accounted for 73% and 55% of the administered activity and could be described by three-component exponential functions with halftimes of about 1h, 2 days and 150 days, respectively. Urinary excretion accounted for 24% of the administered activity, almost all during the first 24h after administration; about 2% was excreted in the faeces in 48h. The halftime of retention of 14C in fat ranged from 137 to 620 days. Absorbed dose calculations indicate that for a normal adult the largest dose, 1.5-7.0mGy/MBq is received by the adipose tissue, and that the effective dose is 0.3-0.5mSv/MBq. It is concluded that no restrictions need to be placed on radiation safety grounds on the administration of 0.05-0.1MBq 14C-triolein for the triolein breath test.     

Accuracy of a rapid 10-minute carbon-14 urea breath test for the diagnosis of Helicobacter pylori-associated peptic ulcer disease

Urease in the human gastric mucosa is a marker for infection with Helicobacter pylori (HP), an organism which is associated with peptic ulcer disease. To detect gastric urease, we examined 184 patients (144 males, 40 females; mean age: 49.8±15.6 years) with suspected peptic ulcer disease. Fasting patients were given orally 5 Ci of carbon-14 labelled urea. From each patient only one breath sample was collected in hyamine at 10 min. The amount of ¹⁴C collected at 10 min was expressed as follows: [(DPM/mmol CO₂ collected)/(DPM administered)] × 100 × body weight (kg). The presence of HP colonization was determined by examination of multiple endoscopic prepyloric antral biopsy specimens subjected to culture or a rapid urease test. For the purpose of this study, HP-positive patients were defined as those with characteristic bacteria as indicated by a positive result of either the culture or the rapid urease test; HP-negative patients were defined as those with negative findings on both the culture and the rapid urease test. Of the 184 cases, 99 (53.8%) were positive for HP infection, and 85 (46.2%), negative. The sensitivity and specificity of the rapid 10 min ¹⁴C-urea breath test for the diagnosis of HP-associated peptic ulcer disease were evaluated by a receiver operating characteristic (ROC) curve with a variable cut-off value from 1.5 to 4.5. When a cut-off value of 1.5 was selected, the sensitivity was 100% and the specificity, 83.5%; when a cut-off value of 4.5 was selected, the sensitivity was 54.5% and the specificity, 97.6%. Correspondence to: Chia-Hung Kao     

MIRD Pamphlet No. 14: a dynamic urinary bladder model for radiation dose calculations.

The constant-volume urinary bladder model in the standard MIRD phantom has recognized limitations. Various investigators have developed detailed models incorporating more physiologically realistic features such as expanding bladder contents and residual volume, and variable urinary input rate, initial volume and first void time. We have reviewed these published models and have developed a new model incorporating these factors. The model consists of a spherical source with variable volume to simulate the bladder contents and a wall represented by a spherical shell of constant volume. The wall thickness varies as the source expands or contracts. The model provides for variable urine entry rate (three different hydration states), initial bladder contents volume, residual volume and first void time. The voiding schedule includes an extended nighttime gap during which the urine entry rate is reduced to one-half the daytime rate. Radiation dose estimates have been calculated for the bladder wall surface (including photon and electron components) and at several depths in the wall (electron component) for [18F]FDG, 99mTc-DTPA, 99mTc-HEDP, [99mTc]pertechnetate 99mTc-RBCs, 99mTc-glucoheptonate, 99mTc-MAG3, [123I]/[124I]/[131I]OIH and sodium [131I]iodide(Nal). The initial bladder volume and first void time that provide the lowest radiation dose to the bladder wall are determined separately for each compound to give guidance for establishing dose reduction protocols.     

Nuclear medicine liver function tests for pregnant women and children 1. Breath tests with 14C-methacetin and 13C-methacetin

Stable isotopes, such as ¹³C, should be substituted for the long-lived radionuclide ¹⁴C in the ¹⁴C breath test when doing liver function tests in children and pregnant women. For comparison ¹³C, ¹⁵N-methacetin and ¹⁴C-methacetin were synthesized as suitable diagnostic agents. Methods are described for the measurement of ¹⁴C and ¹³C in the breath. After oral administration of labelled methacetin to healthy subjects and patients with liver diseases a good correspondence between ¹³C- and ¹⁴C-measurements in the same subject on the one hand, and a good discrimination between controls and patients on the other hand were shown. Findings with regard to ¹⁴C measurements in urine are discussed supporting the supposed advantage of ¹³C-methacetin over ¹⁴C-methacetin application.     

Nuclear medicine liver function tests for pregnant women and children. 1. Breath tests with 14C-methacetin and 13C-methacetin

Stable isotopes, such as 13C, should be substituted for the long-lived radionuclide 14C in the 14C breath test when doing liver function tests in children and pregnant women. For comparison 13C, 15N-methacetin and 14C-methacetin were synthesized as suitable diagnostic agents. Methods are described for the measurement of 14C and 13C in the breath. After oral administration of labelled methacetin to healthy subjects and patients with liver diseases a good correspondence between 13C- and 14C-measurements in the same subject on the one hand, and a good discrimination between controls and patients on the other hand were shown. Findings with regard to 14C measurements in urine are discussed supporting the supposed advantage of 13C-methacetin over 14C-methacetin application.     

核医学诊断工作场所辐射水平及防护现状调查

目的 对我国核医学诊断工作场所辐射防护现状进行调查.方法 2013年2—12月期间,在东北、华中和华北地区分别选择1家三甲医院,用γ剂量率仪巡测核医学诊断制药、淋洗、分装、注射、扫描过程中工作场所周围剂量当量率,光致发光剂量计测量放射工作人员个人有效剂量和当量剂量.结果 在放射性药物分装、注射和受检者摆位等操作环节中周围剂量当量率较高, 分装时最高达1.92 mSv/h,注射时距针管5 cm处剂量率最高达1.2 mSv/h,受检者体表30 cm处剂量率范围为5.36~240 μSv/h,某医院护士手部当量剂量为0.01~0.02 mGy,部分工作场所存在人员路线交叉及注射后受检者停留在公众区域的现象.结论 核医学实践中放射工作人员应加强个人防护,提高操作熟练程度以缩短作业时间,应优化放射工作人员出入路线,加强注射后受检者的管理,以免公众人员受到不必要的照射.     

质子加速器治疗室辐射防护优化研究

目的 研究铁屏蔽体在主防护墙中不同深度对防护墙外周围剂量当量率的影响。方法 采用FLUKA蒙特卡罗模拟程序构建了质子治疗室的模型,治疗室的屏蔽体由混凝土和钢构成。分别模拟220和250 MeV的质子照射水模体,以获得不同情况下的周围剂量当量率分布。结果 随着嵌入防护墙的铁屏蔽体深度的变化,两种模拟条件下质子治疗机房主防护墙外30 cm处的周围剂量当量率发生显著变化,最大周围剂量当量率（220 MeV：3.42 μSv/h,250 MeV：6.39 μSv/h）比最小周围剂量当量率（220 MeV：1.75 μSv/h,250 MeV：3.32 μSv/h）高2倍。结论 在质子治疗加速器的设计中,应仔细评估铁屏蔽体在主防护墙中的位置。